Alternative On-site Wastewater Treatment And Disposal Systems-1988

ALTERNATIVE
ON -SITE
WASTEWATER
TREATMENT
ARID DISPOSAL
SYSTEM
DCM COPI
D",�
Please do not remi
Division of Coastal Management
we.
Copy

tALTERNATIVE
ON -SITE WASTEWATER
TREATMENT AND DISPOSAL SYSTEMS
prepared for
'
BEAUFORT COUNTY
tprepared
by
Yvonne Abernethy
Environmental Consultant
and
Y
MID-EAST COMMISSION
P.O.. BOX 1787
'
WASHINGTON, NC 27889
1
Preparation financed in part by
A grant provided by the North Carolina Coastal
' Management Program, through funds provided by the
Coastal Zone Management Act of 1972, as amended, which
is administered by the Office of Ocean and Coastal
Resource Management, National Oceanic and Atmospheric
Administration.
1
NOVEMBER 1988

TABLE OF CONTENTS
ALTERNATIVE ON-SITE•WASTEWATER
TREATMENT AND DISPOSAL SYSTEMS
PAGE
CHAPTER 1 _
INTRODUCTION
BACKGROUND.................................................. 1
Soils Map of Beaufort County. .......................... 3
Overview of Report....;..... 4
Permitting Procedures .................................. 5
Wastewater Characterization.... ...................... 8
Initial Site Evaluation ................................ 10
Preliminary Screening of Disposal Options .............. 10
Detailed Site Evaluation ............................... 12
Soil Texture ...................................... 13
Soil Structure .................................... 13
Soil Color ........................................ 15
Seasonally Saturated Soils.......... .............. 18
Other Selected Soil Characteristics ............... 18
Hydraulic Conductivity.......... ... 20
Other Site Characteristics .............. ......... 21
Selection of Most Appropriate System and Design........ 25
CHAPTER 2
ALTERNATIVES TO CONVENTIONAL ON -SITE SYSTEMS ................ 26
A. SYSTEMS WITH SEPTIC TANK COMPONENTS.................... 27
1. Ssptic Tank Mound Systems ......................... 33
2. Septic Tank/Evapotranspiration Bed ................ 37
3. Septic Tank/Intermittent Sand
Filter/Spray Irrigation ................ 41
4. Septic Tank/Constructed Wetland/Leachfield........ 49
5, Septic Tank/Low Pressure Pipe Distribution........ 58
i

... ..... .. .......... ...
--v
TABLE OF CONTENTS
CONTINUED
CHAPTER 3
PAGE
B. SYSTEMS NOT UTILIZING A SEPTIC TANK .................... 62
1. AEROBIC UNIT/SOIL ABSORPTION SYSTEM ............... 62
a. Extended Aeration Systems .................... 63
b. Fixed Film Systems ........................... 68
2. MICROWAVE UNIT/SOIL ABSORPTION FIELD
OR SPRAY IRRIGATION SYSTEM ........................ 77
C. MODIFICATIONS TO CONVENTIONAL ON -SITE SYSTEMS.......... 81
1. Trench Modifications. ... 81
2. Site Drainage. .......... ........... 84
3. Alternating Dual Drain Field•Distribution......... 88
CHAPTER 4
REJUVENATION TECHNIQUES FOR FAILING SYSTEMS ................. '89
A. EXCAVATION REPLACEMENT OF TRENCH/SOIL INTERFACE........ 90
B. SHALLOW CROSS -TRENCHING OF EXISTING DRAINFIELD..... .... 92
C. DRAINFIELD RESTING..........................0.......... 94
D. AERATION OF SEPTIC EFFLUENT.......... ....... oo .... _oo. 95
E. CHEMICAL OXIDATION OF CLOGGED DRAINFIELD............... 96
CHAPTER 5
WATER CONSERVATION PRACTICES AND DEVICES ..............:..... 98
A. WATER CONSERVATION PRACTICES ........................... 98
B. WATER -SAVING TOILETS .................................. 100
C. NON -WATER USING TOILETS...... 105
D. FLOW RESTRICTING;SHOWERHEADS ........................... 112
E. FLOW RESTRICTING FAUCETS ............................... 116
F. RECYCLE/REUSE.......................................... 119
ii

TABLE OF CONTENTS
CONTINUED
PAGE
CHAPTER 6
CLUSTER SYSTEMS ............................................. 123
A. SMALL DIAMETER EFFLUENT SEWER .......................... 124
B. GRINDER PUMP SYSTEM .................................... 126
C. VACUUM SEWER .................................`.......... 128
LARGE CLUSTER/COMMUNITY TREATMENT
AND DISPOSAL OPTIONS........... 130
A. PACKAGE TREATMENT,PLANTS/DISCHARGE
ORSPRAY IRRIGATION .................................... 130
B. WASTEWATER TREATMENT,PONDS/DISCHARGE
ORSPRAY IRRIGATION... o.000 ..... oo .... 00000000000000000 142
CHAPTER 7
DISINFECTION................................................. 146
A. CHLORINATION..._ .............................'............ 147
B. IODINE ................................................. 148
C. OZONE .................................................. 149
D. ULTRAVIOLET RADIATION- ............................. 150
CHAPTER 8
MANAGEMENTOF ON -SITE SYSTEMS ............................... 154
APPENDIX A
APPENDIX B
iii

�-v
LISTING OF TABLES
TABLE 1. Major Soil Types (Beaufort County 1987
Land Use Plan) ...................................
TABLE 2. Division of Environmental Management
Permitting Procedure (Hodges, pers. comm.).......
TABLE 3. County Health Department
Permitting Procedure (Taylor, pers. comm.).......
.TABLE 4. Sources of Information ...........................
TABLE 5. Textural Properties of Mineral'Soils (EPA, 1980).
TABLE 6. Types of Soil Structure (EPA, 1980)..............
TABLE 7. Description of Soil Mottles (EPA, 1980)..........
TABLE 8. Estimated Hydraulic Characteristics
of Soil (EPA, 1980)............................
TABLE 9. Falling Head Percolation Test Procedure
(EPA, 1980)........................................
TABLE 10. Summary of Effluent Data from Various
Septic Tank Studies (EPA, 1980...................
TABLE 11. Performance of Buried Intermittent Filters
Receiving Septic Tank Effluent (EPA, 1980).......
TABLE 12. Performance of Recirculating Intermittent
Filters (EPA, 1980)..............................
TABLE 13. Wetland Plants used in Constructed Wetlands
(Wolverton, pers. comm., 1988)...................
TABLE 14. Artificial Marshes for Treating Discharged
Wastewater from Sewage Lagoon and/or
Septic Tanks (Wolverton, 1987)...................
iv
PAGE
E
7
8
11
14
16
17
21
22
31
45
46
51
53

LISTING OF TABLES
PAGE
TABLE 15.
Artificial Marshes for Treating Discharged
Wastewater from Sewage Lagoon and/or.
Septic Tanks (Wolverton, 1987)...................
54
TABLE 16.
Artificial Marsh Wastewater Treatment System
Using Combined Plant/Rock and Plant/Carbon
Filters (Wolverton, 1987)........................
55
TABLE 17.
Summary of Effluent.Data from Various
Aerobic Unit Field Studies (EPA, 1980).....6.....
65
TABLE 18.
Suggested Maintenance for On -Site Extended
Aeration Package Plants (EPA, 1980)..............
66
TABLE 19.
Operational Problems: Extended Aeration
Package Plants (EPA, 1980).......................
67
TABLE 20.
Suggested Maintenance for On -Site Fixed Film
Package Plants (EPA, 1980).......................
70
TABLE 21.
Operational Problems: Fixed Film Package
Plants (EPA, 1980)......................... ...
71
TABLE 22.
National Sanitation Foundation Standard No. 40:
Product Listing for Individual Aerobic Wastewater
Treatment Plants .................................
74
TABLE 23.
Effluent Characteristics from Microwave
Treatment Unit (Microwave National,''1987)........
78
TABLE 24.
Wastewater Flow Reduction - Water Carriage
Toilets and Systems (EPA, 1980)..................
101
TABLE 25.
Wastewater Flow Reduction - Non -Water Carriage
Toilets (EPA, 1980)..............:.... ..........
109
v

LISTING OF TABLES
PAGE '
TABLE 26. Wastewater Flow Reduction Bathing Devices '
and Systems (EPA, 1980)............. ......... 113
TABLE.27. Wastewater Flow Reduction - Miscellaneous '
Devices and Systems (EPA, 1980).......... ...... 117
TABLE 28., Wastewater Flow Reduction - Wastewater Recycle
and Reuse Systems (EPA, 1980).................... 120 t.
TABLE 29. Commercial Biological Package Plants (EPA, 1977). 131
TABLE 30. Total Annual Cost of a Still Extended
Aeration Plant (Triangle J, 1978)................ 136
APPENDICES:
TABLE IA. Characteristics of Typical Residential Wastewater,
TABLE 2A. Summary of Average Daily Residential Wastewater
Flows (EPA, 1980).
TABLE 3A. Residential Water Use by Activity,` '
TABLE A-1. U.S. Department of Agriculture Size'Limits,
for Soil Separates (EPA, 1980). '
TABLE A-2. Soil Science Survey Type and Class
of Soil Structure (EPA, 1980).
MAP: Beaufort County Soils Map '
(U.S.D.A. Soil Conservation Service) ............. 3
t
vi '

LISTING OF FIGURES
PAGE
FIGURE 1.
On -Site System Design Strategy (EPA, 1980)......
9
FIGURE 2.
Types of Soil Structure (EPA, 1980).............
16
FIGURE 3.
Typical Observation Well for Determining
Soil Saturation (EPA, 1980).....................
19
FIGURE 4.
Construction of a Percometer (EPA, 1980)........
23
FIGURE 5.
Diagram of a Septic Tank System (EPA, 1980).....
28
FIGURE 6.
Components of a Mound System
(Cogger, et al., 1982)....,............. ..........
33
FIGURE 7.
Cross Section of Typical Evapotranspiration
Bed (EPA, 1980)...............0.................
37
FIGURE 8.
General Site Plan; Residential Spray Irrigation
(McKaskill, 1988) ...............................
42
FIGURE 9.
Recirculating Sand Filter (Otis, 1986)..........
43
FIGURE 10.
Artificial Marsh System for Treating Discharge
from Septic Tanks (Wolverton, 1988).............
50
FIGURE 11.
Basic Components of a Low Pressure Pipe System
(Cogger, et Al., (1982).........................
58
FIGURE 120''
Examples of Extended Aeration Package Plant
Configurations (EPA, 1980)......................
64
FIGURE 13.
Examples of Fixed Film Package Plant
Configurations (EPA, 1980)......................
69
FIGURE 14.
Curtain Drain to Intercept Laterally Moving
Perched Water Table Caused by a Shallow,
Impermeable Layer (EPA, 1980)...................
85
vii

LISTING OF FIGURES
PAGE '
FIGURE 15. Vertical'Drain to Intercept Laterally Moving '
Perched Water Table Caused by a Shallow,
Thin, Impermeable Layer (EPA, 1980)............. 85
FIGURE 16. Underdrains Used to Lower Water Table '
(EPA, 1980).................................... 86
0
FIGURE 17. Extended Aeration Treatment Plant with '
Air.Diffusers (EPA, 1977)....................... 137
FIGURE 18. Extended Aeration Treatment Plant with '
Mechanical Aerator (EPA, 1977).................. 138
FIGURE.19. Contact Stabilization Plant with Aerobic
Digester (EPA, 1977)............................ 139
FIGURE 20. Bio-Disc Treatment Plant (EPA, 1977)............ 140
APPENDIX A:
.1
FIGURE A-1. Names and Sizes of Practical -Size Classes
According to.Six Systems.
FIGURE A-2. Textural Triangles Defining Twelve Textural Classes
of the USDA. Illustrated for a Sample Containing '
.37% Sand, 45% Silt, and 18% Clay (EPA, 1980).
FIGURE A-3.' Schematic Diagram of a Landscape and Different
Soils Possible (EPA, 1980).
FIGURE A-4. Upward Movement by Capillarity in Glass Tubes '
as Compared with Soils (EPA, 1980).
viii
} !r

LISTING OF FIGURES
' FIGURE A-5. Soil Moisture Retention for Four Different
Soil Textures (EPA, 1980).
FIGURE A-6. Hydraulic Conductivity (K) versus Soil
Moisture Retention -(EPA, 1980).
FIGURE A-7. Schematic Representation of Water Movement
Through a Soil with Crusts of Different
Resistances (EPA, 1980).
1
r .
' ix

CHAPTER 1
INTRODUCTION
BACKGROUND
' North Carolina relies heavily on the use of on -site
wastewater treatment and disposal systems. This trend is not
' expected to change in light of predicted dispersed population
growth in rural areas and the high cost of large systems that
would be needed to accommodate such growth patterns.
A. conventional on -site system consists of a two
compartment concrete or masonry tank (septic tank) and a
' drainfield. The septic tank accomplishes primary treatment of
wastewater through solids removal and decomposition. The
drainfield provides final treatment by using the living medium of
' soil to trap and neutralize nutrients, organic material, and
pathogens and then disposes of the treated effluent. The
conventional system configuration has met.with.wide acceptance.
When properly designed, installed and maintained, a high degree
of treatment is achieved with a relatively simple design at low
cost over a long period of time.
In Beaufort County, an estimated 78 percent of the total
' land area has soil with severe limitations for on -site systems
which rely on the soil for final treatment and.disposal of sewage
' (Beaufort County 1987 Land Use Plan). Table 1 and Map 1 display
this information. The consequences of faulty installation or
1 1

TABLE 1. Major Soil Types (Beaufort County 1987 Land Use Plan).
LIMITATIONS FOR:
BUILDINGS W/0 SEPTIC RUNOFF DEPTH TO HIGH % TOTAL
SOIL TYPE SLOPE BASEMENTS TANKS (1) POTENTIAL WATER TABLE (FT) . CO. LAND
Arapahoe fine sandy loam
0-2%
severe
severe
varies
0.0
- 1.0
4.2
Augusta fine sandy loam
0-2%
severe
severe
moderate
1.0
- 2.0
3.2
Bayboro loam
0-2%
severe
severe
high
+1
- 0.5
5.9
Cape fear fine sandy loam
0-2%
severe
severe
high
0.0
- 1.5
3.3
Craven fine sandy loam
0-1%
severe
severe
moderate
2.0 -
3.0
2.3
Croatan muck
0-2%
moderate
severe
high
+1 -
1.0
2.2
Goldsboro fine sandy loam
0-2%
moderate
severe
slight
2.0 -
3.0
2.3
Leaf loam
0%
severe
severe
high
0.5 -
1.5
8.2
Lenior loam
0% -
severe
severe
high
1.5 -
2.5
6.2 [V
Lynchburg fine sandy loam
0%
severe
severe
moderate
0.5 -
1.5
3.7
Muckalee.loam
0%
severe
severe
high
0.5 -
1.5
4.0
Pantego loam
0-2%
severe
severe
varies
0.5 -
1.5
2.7
Ponzer muck
0-1%
severe
severe
high
0.0 -
1.0
2.8
Portsmouth loam
0-2%
severe
severe
varies
0.0 -
1.0
6.2
Rains fine sandy loam
0%
severe
severe
moderate
0.0 -
1.0
3.5
Roanoke fine sandy loam
0-2%
severe
severe
high
0.0 -
1.0
8.4
Torhunta sandy loam
0-2%
severe
severe
moderate
0.5 -
1.5
9.2
TOTAL
78.1
(1) Water table >4 ft. - severe limitations.
NOTE: "Major" soils comprise 2% or more of all land; limitations
are for soil in virgin state with no improvements.
Source: Soil Survey Maps and Interpretations, Beaufort County,
North Carolina, U.S.D.A., S.C.S., July 1984.
M wmmm mmmmmmmm

4
improperly siting on -site systems -ore grave. Ponding of raw
�. sewage in yards and backing up of sewage into dwellings, both
present threats to the public health. Less visible but just as
threatening to public health through environmental degradation
' are the effects of nutrient enrichment on lakes and rivers from
near -shore developments and the contamination of; groundwater.
' This document is a product of the Alternative Wastewater
Disposal: Demonstration Project funded - by North Carolina's
' Department of Natural Resources .and Community Development
through the Coastal Planning and Management Grant Program.
Beaufort County, was awarded the grant and subcontracted with the
Mid -East Commission to.complete the terms of the agreement. The
Mid -East Commission has prepared this catalogue of alternative
wastewater disposal systems in partial fulfillment of the
agreement.
Overview of Report
' The overall purpose of this document is to provide easily
understandable information on alternative wastewater treatment
' and disposal systems. Design characteristics, costs, avail-
ability, and. legality are presented on each system along with
strengths' and weaknesses for use. in, the coastal setting. The
' emphasis of this document is on systems for single family dwell-
ings and small clusters of up to 10 or 12 housing units.
1

w
Additional subjects addressed in this document are a
strategy for selecting an on site system, a brief discussion of
factors considered in evaluation, conventional system modifica-
tion, system rejuvenation techniques, and discussion of on -site
system management options.
This- document is - intended for use by professionals,
government officials,'and the general public. It will serve to
acquaint the user with the choices possible for on -site waste-
water treatment and disposal. More in-depth information and
detail can be obtained through the references cited. The
individual system specification included in the report are
intended as guides only. The appropriate local and state
authorities and/or knowledgeable sanitation engineer should be
consulted on a site -by -site basis for local design requirements.
Cost estimates are just that. Accurate cost data was not
available for systems not commonly used in the coastal area at
present.
Permitting Procedures
A wide variety of on -site wastewater treatment and disposal
systems exist. Primary consideration in selecting a design must
be the protection of public health and prevention of environ-
mental degradation. Secondary criteria are cost, east of opera-
tion and maintenance, and the fate of only residuals resulting

from the treatment system (EPA, 1980). In North Carolina, on -
I
site wastewater treatment and disposal systems are administered
by two agencies, the Department of Health and Human Services
through the local County Health Department and the Department of
INatural Resources and Community Development through the Division
of Environmental Management. The County Health Department is
authorized to permit domestic systems with flows under 3,000
gallons per day (gpd) and that utilize subsurface discharge as
ithe final effluent disposal method (North Carolina Administrative
' Code, Chapter 10, subchapter 10A, section 1900). The Division of
Environmental Management is authorized to permit systems with
flows greater than 3,000 gpd and/or utilize as the final disposal
method discharge to the surface of the land or discharge to
surface waters (North Carolina Administrative Code, Chapter 15,
subchapter 2H, sections .0100, .0200, and .0300).
The permitting, procedure for the Division of Environmental
P g
Management and County Health Department are presented in Tables 2
and 3 respectively. In order for individuals .to be informed
participants in the process, they need to acquire an -under-
standing of the information need to make wastewater treatment and. -
disposal decisions.
1 Figure 1 portrays a suggested strategy to utilize in
gathering the needed facts and can serve to guide individuals as

_.V
7
TABLE 2.. Division of Environmental Management
Permitting Procedure (Hodges, pers. comm.).
1. Submit Permit Application with fee
Application fee dependent on volume of
flow (in future), presently $150..
2. Require a certified soil scientist to review
site, conduct investigation, and submit report.
3. Hire professional engineer to prepare plan
in triplicate and submit with application.
MINIMUM INFORMATION REQUIRED
IN ENGINEERING PLAN
1. Plan view of site (aerial -type view overall)
drawn to.scale.
2. Appropriate design information on system components.
3. Design calculations:
a. rates of application
b. cover crops on site/care and
maintenance capacity of site
C. size of dwelling/number of
bedrooms and/or people
d. volume of flow and application rate based on
soil scientist's report and DEM regulations
e. specifications and drawing of
components and placement
f. copy of plan with information that contractor
can use for construction
CONDITIONS OF PERMIT
1. Permit is for 3 or 5 years; six months before
expiration, must request reissuance.
2. Recommendations will be made to correct any
areas of noncompliance.
3. Additional fee at time/flow proportioned.
4. Can require monitoring of groundwater and/or effluent.
5. Require licensed operator for system. To be licensed
individual must take a course and pass State
operators' test.

8
TABLE 3. County Health Department Permitting Procedure
(Taylor, pers. comm.).
1. Fill out application for lot inspections
at Beaufort County Health Department.
2. Sanitarian complete lot evaluation.
3. Sanitarian and lot owner meet and discuss project.
Site is classed as Suitable, Provisionally Suitable,
Unsuitable.
4. If modification is required, must be complete
before issuance of improvement permit.
5. If Provisionally Suitable, inspect modifications
and issue permit. If suitable, issue improvement permit.
6. Inspect after septic tank installed; contractor calls
sanitarian for an inspection before covering the system
with soil. If suitable, completion permit issued.
they pursue a solution to their wastewater treatment and disposal
questions. The following strategy and information is borrowed
in large measure from the Environmental Protection Agency's
Design Manual: Onsite Wastewater Treatment and Disposal Systems
(EPA 625/1/80-012).
Wastewater Characterization
' Domestic waste characterization is simply estimating the
' daily wastewater volume -and any short- or long-term variations in
flow which will affect system components. Characterizing
domestic flow chemically is usually unnecessary. Information

WASTE
CHARACTERIZATION
INITIAL
SITE
EVALUATION
PRELIMINARY
SCREENING OF
DISPOSAL OPTION
DETAILED
SITE
EVALUATION
9
■
DESIGN SYSTEM '
o Treatment
o Disposal
o Residuals
SELECTION OF
TREATMENT t
COMPONENT(S)
SELECTION OF
DISPOSAL OPTION
FIGURE 1. On -Site System, Design Strategy (EPA, 1980).

' 10
typifying domestic flows is detailed in Appendix A, Tables 1A,
2A, and 3A. Volume is typically based on the number of occupants
in the dwelling and is modified to reflect the use of household
appliances and water conserving devices (Tables 24, 25, and 26).
Variations in flow result from such factors as seasonal occupa-
tion of a dwelling.
Initial Site Evaluation
Initial site evaluation involves reviewing available
published information and records and a site visit. Maps and
published reports can provide information on soils, soil test
results and designs in use in the area, geology, topography,
climate, and other physical features such as a lot plan. An
' initial site visit will reveal relative soil permeability, depth
and nature of bedrock, depth to water table, slope, lot size, and
landscape position. This can be done by visual survey and field
testing with a hand auger. Table 4 details sources of published
information.
Preliminary Screening of Disposal Options
' Preliminary screening of disposal options involves determin-
' ing which options are potentially viable given the site con-
straints identified in the initial site evaluation. Disposal
options can be grossly grouped into three categories: subsurface
I A-

-v
11
TABLE 4. Sources of Information.'
County Soil Surveys USDA Soil Conservation Service
Local Office
(a guide to general soil suitability)
Quadrangles U.S. Geological Survey
(aid in describing topography, local
depressions and wet areas, regional
drainage, rock outcrops, water table
elevations)
Soil Test Reports Local Health Department
discharge, surface discharge and discharge to surface waters.
Traditionally, subsurface discharge has been viewed as the
most favored method for wastewater disposal for single family
residences. This is based on the method's reliability and need
for minimal attention in meeting public health and environmental
standards. When site characteristics are not conducive to
13

12
subsurface absorption, discharge. to -,the surface of the land or
' water may offer safe options. These methods are typically more
complex and so more costly to construct and more difficult and
' costly to maintain. Detailed information on system designs with
' various disposal options are provided in the next chapter.
' Detailed Site Evaluation
The objective of a site investigation is to evaluate the
characteristics of the area for their potential to treat and
dispose of wastewater. A good site evaluation is one that
'
provides sufficient information to select the most appropriate
' treatment and disposal system. This requires that the site
evaluation begin with all options in mind; eliminating those
' options as not feasible only as collected site data. indicate.
At the completion of the investigation, final selection of a
system from those practicable options is based on costs,
aesthetics, and personal preference.
A detailed site evaluation involves assessing the soil
' texture, structure, color, saturation, and hydraulic -conduc-
tivity. Brief explanations of these soil characteristics follow
' -and the reader is.referred to Appendix A. for greater detail.

�v
13
Soil Texture
Texture is one of the most important physical properties of
soil because of its relationship to pore size, pore size
distribution, and pore continuity. It refers to the relative
proportion of the various sizes of particles in the soil that are
less than 2 mm in diameter. The soil texture is detprminpa in
the field by rubbing a moist sample between the thumb and
forefinger. The grittiness, "silkiness," or stickiness can be
interpreted as being caused by the soil separates of sand, silt,
and clay. Table 5 summarizes the textural properties of mineral
soils (EPA,,1980).
soil Structure
Soil structure has a significant influence on the soil's
ability to accept and transmit water.. Soil structure refers to
the aggregation of soil particles into clusters of particles,
called peds. The space between the peds often appears as cracks
in the soil and can greatly modify the influence of soil texture
on water movement. Well -structured soils with large spaces
between peds will transmit water more rapidly than structureless
soils of the same texture, particularly if - the soil has become
dry before the water is added. Fine -textured_ mas-civo, _cr%iia
(soils with little structure) have very slow percolation rates
(EPA, 1980).

14
TABLE 5. Textural Properties of Mineral Soils (EPA, 1980).
APPEARANCE
FEELING AND
SOIL CLASS
DRY SOIL
MOIST SOIL
Sand
Loose, single grains which
Squeezed in the hand, it
feel gritty. Squeezed in
forms a cast which crumbles
the hand, the soil mass
when.touched. Does not form
falls apart when the
a ribbon between thumb and
pressure is released.
forefinger.
Sandy Loam
Aggregates easily crushed;
Forms a cast which bears
very faint velvety feeling
careful handling,without,
initially but with continued
breaking. Does not form a
rubbing the gritty feeling
ribbon between thumb and
of sand soon dominates.
forefinger.
Loam
Aggregates are crushed under
Cast can be handled quite
moderate pressure; clods can
freely without breaking.
be quire firm. When pulver-
Very slight tendency to -
ized, loam has velvety feet
ribbon between thumb and
that becomes gritty with
forefinger. Rubbed surface
continued rubbing. Casts
is rough.
bear, careful handling.
Silt Loam
Aggregates are firm but may
Cast can be freely handled
be crushed under moderate
without breaking. Slight
pressure. Clods are firm to
tendency to ribbon between
-hard. Smooth, flour -like
thumb and forefinger. Rubbed
feel dominates when soil
surface has a broken or
is pulverized
rippled appearance.
Clay Loam
Very firm aggregates and
Casts can bear much handling
hard clods that strongly
without breaking. Pinched
resist crushing by hand.
between the thumb and fore -
When pulverized, the soil
finger, it forms a ribbon
takes on a somewhat gritty
which surface tends to feel
_
feeling due to the harsh-
slightly gritty when dampened
ness of the very small
and rubbed. Soil is plastic,
aggregates which persist.
sticky and puddles easily.
Clay
Aggregates are hard; clods
Casts can bear considerable
are extremely hard and ,
handling without breaking.
strongly resist crushing by
;Forms a flexible ribbon
hand. When pulverized, it
between thumb and forefinger
has a grit -like texture due
and retains its plasticity
to the harshness of numerous
when elongated. Rubbed
very small aggregates which
surface has a very smooth,
persist.
satiny feeling. Sticky when,
wet and easily puddted.
A.-

_V
15
Since the structure can significantly alter the hydraulic
characteristics of soils, more detailed descriptions of soil
structure are sometimes desirable. Size and grade of durability
of the structural units provide useful information to estimate
hydraulic conductivities.- Grade descriptions are given in
Table 6 and Figure 2.
Soil Color
Color and color patterns in ,soil are good indications of
soil drainage characteristics. Soil properties,, location in the
landscape, and climate influence water movement in the soil.
These factors cause some soils to be saturated or seasonally
saturated, which affects their ability to absorb and.treat waste-
water. Understanding and interpreting soil color aids in
identifying these conditions'.
Color may be described by estimating the true color for each
horizon or by comparing the soil with the colors in a soil color
book. To do so, observe uncrushed moist soil in good sunlight.
The standard method of describing soil colors is using
Munsell color notation.• This notation is used in soil survey
reports and soil description. Hue is the dominant spectral color
and refers to the lightness or darkness of the color between
black and white. Chroma is the relative purity of strength of
the color, and ranges from gray to a bright color of that hue.

16
TABLE 6. Types of Soil Structure (EPA, 1980).
GRADE CHARACTERISTICS
Structureless No observable aggregation.
Weak Poorly formed and difficult to see.
Will not retain shape on handling.
Moderate Evident but not distinct in
undisturbed soil. Moderately
durable on handling.
Strong Visually distinct in undisturbed
soil. Durable on handling.
s
;., Subangular
Angular Blocky
Prismatic Columnar Blocky
dw
at,
Platy
FIGURE 2. Types of Soil Structure (EPA, 1980).
a-

-v
17
Numbers are given 'to each of the variables and a verbal descrip-
tion is also given. For example, 10YR 3/2 corresponds to a color
hue of 10YR value of 3 and chroma 2. This is a very dark grayish
brown.
Mottling in soils is described by the color of the soil
matrix and the color or colors, size, and number of the mottles.
Each color may be given a Munsell designation and name. A
classification of mottles used by the U.S. Department of
Agriculture is shown in Table 7 (EPA, 1980).
TABLE 7. Description of Soil Mottles (EPA, 1980).
CHARACTER CLASS LIMIT
Abundance Few
<2% of exposed face
Common
2-20% of exposed face
Many
>20% of exposed face
Size Fine
<5mm longest dimension
Medium
5-15 longest dimension
Coarse
>15mm longest dimension.
Contrast Faint
Recognized only by
close observation
Distinct
Readily seen but
not striking
Prominent
Obvious and striking

1 '
' 18
Seasonally Saturated Soils
' Seasonally saturated soils can be detected by soil .boring
made during the wet season or by the presence of mottles. For
' large cluster systems or for developments where each dwelling is
' served by an on -site system, the use of observation wells may be
needed. They are constructed as shown in Figure 3. The well
' should be placed in, but not extended through, the horizon that
is to be monitored. More than one well in each horizon that may
' become seasonally saturated is desirable. The wells are
' monitored over a normal wet season by observing the presence and
duration of water in the well. If water remains in the well for
' several days, the water level elevation is measured and assumed
to be the elevation of the seasonally saturated soil horizon
' (EPA, 1980) .
' Other Selected Soil Characteristics
Soil bulk density is related to porosity and the movement of
' water. High bulk density is an indication of low porosity and
restricted flow of water. Relative bulk densities of different
' soil horizons can be detected in the field by pushing a knife or
' other instrument into each horizon. If one horizon offers
considerably more resistance to penetration than the others, its
' bulk density is probably higher (EPA, 1980).

19 '
Swelling clays, particularly montmorillonite clays, can seal
off soil pores when wet. They can be detected in the field by '
their tendency. to be more sticky and plastic when wet. These
clays are of concern'in our geographic area. '
FIGURE-3. Typical Observation Well for Determining '
Soil Saturation (EPA, 1980).

20
Hydraulic Conductivity
Several methods of measuring the hydraulic conductivity of
soils have been developed. The most commonly used is the
percolation test. Done properly, the test gives an approximate
measure of the soil's saturated hydraulic conductivity. Since
the percolation of wastewater through soil below soil disposal
systems usually occurs through. unsaturated soils, the unsatu-
rated conductivities must be estimated (EPA, 1980).
' The percolation test is often criticized because of its
variability and inaccuracy. Percolation tests conducted in the
' same soils can vary by 90% or more. Reasons for large vari-
abilities can be attributed to the procedure used, the soil
moisture conditions, and the individual performing the test.
' Despite these shortcomings, the percolation test can be useful
to rank the relative hydraulic conductivity of the soil.
' Estimated percolation rates for various soil textures are given
' in Table 8.
Several percolation test procedures are used. The most
' common procedure is the falling head test. It is simple to
perform in the field. The falling head procedure is outlined in
' Table 9. A diagram of a "percometer" designed to simplify the -
testing is illustrated in Figure 4. For a discussion of other
methods see the National Environmental Health Association's "On -
Site Wastewater Management" (Denver, CO).
A-

21
TABLE 8. Estimated Hydraulic Characteristics of Soil
(EPA, 1980).
SOIL - PERMEABILITY PERCOLATION
TEXTURE IN./HR. MIN.JIN.
Sand
Sandy loams
Porous silt loam
Silty clay loams
Clays, compact
Silt loams
>6.0,
s 0.2-6.0
<0.2
Percolation tests are no longer used in North Carolina for
permitting septic systems. The site characteristics of drainage,
soil structure, texture, and shape are evaluated.
Other Site Characteristics
If subsurface disposal does not appear to be a viable
option or cost-effective, other methods of disposal are
evaluated. The land surface may be used for disposal of treated
wastewater if sufficient area is available and the soil is
receptive.
Surface waters also may be used for the disposal of treated
wastewaters. The capacity of surface waters to assimilate

ITABLE 9.
W
Falling Head Percolation Test Procedure (EPA, 1980).
1. Number and Location of Tests
Commonly a minimum of three percolation tests are performed within the area proposed for an
absorption system. They are spaced uniformly throughout the area. If soil conditions are
highly variable, more tests may be required.
2. Preparation of Test Hole
The diameter of each test hole is 6 inches, dug or bored to the proposed depths at the
absorption systems or to the most limiting soil horizon. To expose a natural soil surface, the
sides of the hole are scratched with a sharp pointed instrument and the loose material is
removed from the bottom of the test hole. Two ihches of 1/2 to 3/4 inches of gravel are placed
in the hole to protect the bottom from scouring action when the water is added.
3. soaking Period
The hole is carefully filled with at least 12 inches of clear water. This depth of water
should be maintained for at least 4 hours and preferably overnight if clay soils are present. A
funnel.with an attached hose or similar device may be used to prevent water from washing down
the sides of the hole. Automatic siphons or float valves may be employed to automatically
maintain the water level during the soaking period. It is extremely important that the soil be
allowed to soak for a sufficiently long period of time to allow the soil to swell if accurate
results are to be obtained.
In sandy soils with tittle or no clay, soaking is not necessary. If, after filling the
hole twice with 12 inches of water, the water seeps completely away in less than ten minutes,
the test can proceed immediately.
4. Measurement of the Percolation Rate
Except for sandy soils, percolation rate measurements are made 15 hours but no more than 30
hours after the soaking period began. Any soil that sloughed into the hole during the soaking
' period is removed.and the water level is adjusted to 6 inches above the gravel (or 8 inches
above the bottom of the hole). At no time during the test is the water level allowed to rise
more than 6 inches above the gravel.
Immediately after.adjustment, the water level is measured from a fixed reference point to
the nearest 1/16 inch at 30 minute intervals. The test is continued until two successive water
Level drops do not vary by more than 1/16 inches. At least three measurements are made.
After each measurement, the water level is readjusted to the 6 inch level. The last water
Level drop is used to calculate the percolation rate.
In sandy soils or soils in which the first 6 inches of water added after the soaking period
' seeps away in less than 30 minutes, water, level measurements are made at 10 minute intervals for
a 1 hour period. The last water level drop is used to calculate the percolation rate.
5. Calculation of the Percolation Rate
The percolation rate is calculated for each test hole by dividing the time interval used between
measurements by the magnitude of the last water level drop. This calculation results in a
percolation rate in terms of min./in. To determine the perc6tation rate for the area, the rates
obtained from each hole are averaged. (If tests in the area vary by more than 20 min./in.
variations in soil type are indicated. Under these circumstances, percolation rates should not
be averaged.)
EXAMPLE: If the last measure drop in water level after 30 minutes is 5/8 inches, the
percolation rate = (30 min.)/(5/8 in.) = 48 min./in.
F_

-v
23
Yard Stick
Thin Steel
Eyelets
Rod
Cross Arm
Support
Cork
Float
6"-9"
_
- Diameter
2" Layer
of Gravel
(a) Floating Indicator
When making percolation
tests, mark lines here at
*—Measuring Stick
regular time intervals
Batter Board or
Guide Line
Other Fixed
Reference Point
6"-9" Diameter
•- 2" Layer. of Gravel _
(b) Fixed Indicator
FIGURE 4. Construction of a Percometer (EPA, 1980).

�r
24
wastewater pollutants varies with thp, size and type of the body
of water. In many cases, the potential for human contact as well
as the concern for maintaining the quality of streams,
estuaries, and wetlands, the use of these waters for disposal are
limited. Where they can be used, the minimum quality of the
wastewater effluent to be discharged is specified by the Division
of Environmental Management.
A.t.«

W
Selection of Most Appropriate System and Design'
The disposal options available to use on a site`are reduced '
by the constraints identified in the detailed site evaluation.
This in turn affects the wastewater reduction and treatment
options which can be considered. If suitable' soils exist on '
site, subsurface disposal can be utilized and a high degree of
treatment is not needed. The soil's high assimilative capacity ,
will provide final treatment. If suitable soil is not available
on site, a greater degree of treatment will 'be required. The '
next chapter of this report will detail system configurations
with varying. degrees of applicability to '
PP y the North Carolina
coastal setting. '

D
CHAPTER 2
' ALTERNATIVES TO CONVENTIONAL ON -SITE SYSTEMS
A conventional system consists of a concrete or masonry tank
and a subsurface drainfield. The tank accomplishes solids
' removal through settling and decomposition. The drainfield acts
to both treat the effluent and -dispose of it through the medium
of the soil. Many areas are not suitable for this conventional
soil absorption system. In coastal North'Carolina poor drainage,
impermeable soils, or high seasonal water tables restrict their
use. The following section summarizes alternatives to the
conventional system configuration. Some of the systems are not
presently being used in North Carolina; they have been included
here because they are being used in other states with similar
' environmental concerns and constraints. 26

27
A. SYSTEMS.WITH SEPTIC TANK COMPONENTS
Several alternative 'systems utilize the septic tank as the
primary treatment unit. In this section, a',brief explanation of
septic tank design and function will.be given. Complete system
configurations will be described in following sections.
Septic tanks are buried, watertight receptacles designed and
constructed to receive wastewater from a home, to separate solids
from the liquid,. to provide limited anaerobic digestion of
organic matter, to store solids, and to allow the clarified
liquid to discharge for further treatment and disposal (Figure
5). Solids and partially decomposed sludge settle to the bottom
of the tank and accumulate. .,A scum of lightweight material
(fats and greases) rises to the top. The partially clarified
liquid is allowed to flow through an outlet structure just below
the. floating scum layer. The use of baffles, tees, and ells
prevents scum outflow. Leakage from septic tanks is often
considered a minor factor; however, if tank leakage causes the
level of the sum layer to drop below the outlet baffle, excessive
scum discharges can occur. In the extreme case, the sludge layer
will dry and compact, and normal tank cleaning practices will not
remove it. Another problem, if the tank is not watertight, is
infiltration into the tank which can cause overloading of the
tank and subsequent treatment and disposal components (EPA,
1980).
L,

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
28
Improper maintenance will also%result in problems. If the
tank is not pumped of its sludge every 3-5 years, sludge can
accumulate to the, point of discharge. When this occurs, the
disposal component of the system cannot function properly.
Solids, will clog the drainlines and/or soil. pores in the
drainfield causing the entire system to malfunction.
Sanitary
. In
Liquid —Outlet
Level ;.Scums.:.-:::•..
Scum Clear
Space
Total Clear Space Sludge Clete
Space s
.: Slude�•
FIGURE 5. Diagram of a Septic Tank.System (EPA, 1980).
A+
0

29
In North Carolina, tanks .are required 'to meet specific
standards as to construction, design, volumes, and dimensions.
Size is dependent on the hydraulic design load for the residence.
Two compartment tanks are now required of all new construction in
the State. This design requirement enhances efficient function-
ing of the tanks by improving their settling ability: Detailed
specifications can be found in the North Carolina Code (see
Appendix B).
Performance
Table 10 summarizes septic tank effluent quality. Bacterial
concentrations in the effluent are not significantly changed
since septic tanks cannot be relied upon to disease -causing
microorganisms. Oil and grease removal is typically 70 to 80%,
producing an effluent of about 20-25 mg/l. Phosphorus removal is
slight, at about 15%, providing an effluent quality -of about 20
mg/l total P.(phosphorus) (EPA, 1980).
Studies have shown that efficiency is improved when separate
septic tanks and disposal systems are used for blackwater (toilet
wastewater) and grey water (Brandes, 1978).
Installation Procedures
The following is a list of important considerations for
proper septic tank installation. 'The most important requirement
is that the. tank be placed on a level grade and at a depth that

30
' provides adequate gravity flow from the dwelling. Other
P � g Y g
considerations include:
1. Cast iron inlet and outlet structures should be used in
disturbed soil areas.where tank settling may occur.
2. Flotation collars should be used in areas with
high groundwater potential.
3. The tank should be placed 'so that the manhole is
slightly below grade to prevent accidental entry.
' 4. The tank should be placed in an area with easy access
to alleviate pump -out problems.
' 5. During installation, any damage to the watertight
coating should be repaired. ,After installation,
the tank should be tested for watertightness by
' filling with water.
6. Care should be taken with installation in areas with
' large rocks to prevent undue localized stresses.
7. Baffles, tees, and elbows should be made of
durable and corrosion -proof materials. Fiberglass
' or acid -resistant concrete baffle materials. are
most suitable. Vitrified clay tile, plastic', and
cast iron are best for,tees and ells (EPA, 1980).
Maintenance
Septage must be pumped on a regular basis. It is suggested
that this -be done by a competent septage hauler every three to
' five years.
' Daily maintenance is also needed. This merely involves not
flushing into the system anything which does not readily
' decompose (e.g., sanitary napkins, coffee grounds, cooking fats,
bones, wet strength towels, disposable diapers, facial tissues,

31
TABLE 10'. Summary of Effluent Data from Various
Septic Tank Studies (EPA, 1980).
SOURCE
REF.(2)
REF.(3)
REF.(4)
REF.(5)
REF.(6)
PARAMETER
7 SITES
.10 TANKS
19 SITES
4 SITES
1 TANK
BODS
Mean, mg/t
138
138a
140
240b
120
Range, mg/t
7-480
64-256
-
70-385
30-280
No.of Samples•
150
44
.51
21
50
COD
Mean, mg/l
327
-
-
-
200
Range, mg/L.
25-780
-
-.
71-360
No.of Samples
152
-
-
-
50
Suspended Solids
Mean, mg/l
49
155a
101
95b
39
Range, mg/t
10-695
43-485
-
48-340
8-270
No.of Samples
148
55
51
18
47
Total Nitrogen
Mean, mg/t
45
-
36
-
-
Range, mg/t
.9-125
No.of Samples
99
aCatculated from the average values from 10 tanks, 6 series of tests.
bCalcutated on the basis of a tog -normal distribution of data.

32
cigarette butts). These items wild. not degrade_ and ,can, clog
inlets,,outlets, and the disposal system.
Products touting their ability to_ improve or assist tank
performance are of questionable value and are not needed.
1. Bernhart, A.P., 1967. Wastewater from Homes, University of
Toronto, Toronto Canada.
2. Brandes, M., 1978. Characteristics of Effluents from
Separate Septic Tank Treating Grey and Black Waters from.
the Same House, J. Water Pollu. Control Fed. 50:2547-2559.
3. Environmental Protection Agency, 1980. Design Manual,
Onsite Wastewater Treatment and Disposal _Systems, EPA
625 1-80-012:391 p.
4. Laak, R., 1973. Wastewater Disposal Systems in Unsewered
Areas, Final Report to Connecticut Research Commission,
Civil Engineering_ Department, University of Connecticut,
Storrs.
5. Salvato, J.A., 1955. Experience with Subsurface Sand
Filters, Sewage and Industrial Wastes 27(8):909.
6. Small Scale Waste Management Project, 1978. University of
Wisconsin, Madison, Management of Small Waste Flows, EPA
600 2/78/173, NTIS Report No. PB 286 560:804 p.
7. Weibel, S.R., C.P. Straub, and. J.R. Thoman, 1949. Studies
on Household Sewage Disposal Systems, Part I., Environmental
Health Center, Cincinnati, OH, NTIS Report No. PB 217
671:279 p.

M
33
1. SEPTIC MOUND SYSTEMS
Description
A septic tank/mound is an on -site wastewater treatment and
disposal system that utilizes a standard septic tank for primary
treatment of domestic sewage. Further treatment and disposal is
accomplished with a subsurface soil absorption system that is
elevated above the natural soil surface in suitable fill material
(Figure 6).
Wastewater moves from theseptictank into a holding tank
where it is pumped in controlled doses through small diameter
pipes into a mound. In the mound a network of perforated pipe
distributes the wastewater. Dosed pumping assures uniform.
distribution and allows for resting cycles so that the mound can
dry and aerobic (oxygen rich) conditions can be maintained.
FIGURE 6. Components of a Mound System (Cogger, et al., 1982).

3 4..
' Gravitymoves the effluent down through the .mound and
9
treatment is accomplished by filtration and aerobic decomposi-
tion. Treated effluent is disposed of by absorption through the
' underlying natural soil: and, to a lesser extent, atmospheric
evaporation and transpiration by the vegetative cover. The basal
area of most residential mounds ranges from 1,000 to 5,000 square
' feet depending on soil permeability, mound shape, and design
waste load. A 25-foot wide buffer zone around the base of the
' mound must be set aside as well for repair space. Mounds are not
suited for lots less than three-quarters of an acre in size
' (Cogger et al., 1982). Siting the mound on twelve inches of
' naturally occurring, suitable or provisionally suitable soil as
to texture, structure, and estimated permeability is recommended
' for good performance and required by North Carolina code.
Performance
When properly designed, mounds can give excellent treatment
' to effluent in soils with seasonally high water tables (Bouma et
al., 1975). Proper design and operation are essential for good
' performance.
Basic Components
1. Septic tank
2. Holding tank (2X volume of daily wasteflow)
' 3. 25-.4 horsepower submersible pump and
level controls
4. High water alarm and level -switch
5. Supply manifold (2" PVC pipe)
1

i
35
6. Perforated distribution laterals (1-1/4" PVC pipe
with 1/8-1/4" holes, 2.5-4.0" apart)
7. Mound fill
8. Gravel
9. Topsoil cap
10. Natural soil
11. Vegetation cover
Installation
Mound systems can be installed by a competent septic tank
and landscaping contractor. A backhoe is recommended for moving
fill and excavating for the two tanks. An important concern with
mound installation is protection of the site from disturbance
such as compaction or removal by heavy equipment. Care should be
taken not to work when soil is wet as this will damage the site
also. Any trees should be cut down rather than uprooted to avoid
soil damage. Proper site drainage and protection of the site
from surface runoff is essential. Electrical service must be
provided for the pump. A grassy vegetative cover should be
seeded as soon as possible after construction and be mowed
regularly.
Cost
Costs of an installed system are higher than for a conven-
tional system. This is due to the imported sand, gravel, and
topsoils for the mound. Costs for the system start at'$2,200 and
can range to $2,400 depending on the site. operating expenses
are negligible. Mainterfance,costs are associated with the pump
service and repair and with septage removal every 3-5 years.
Is

36
Strengths -
' 1. Overcomes severe site limitations of shallow soil
or high watertable.
' Weaknesses
1. Higher capital cost.
2. Requires specialized design and supervision in
light of_ site specific details of topography,
drainage, and site preparation.
3. May require substantially more inspection time
than conventional system.
4. In case of pump failure, need for immediate repair
' (3 days)
REFERENCES
1. Bouma, J., J. C. Converse, R.J. Otis,, W.G. Walker, and W.A.
' Ziebell, 1975. A mound system for onsite disposal of septic
tank 'effluent in slowly permeable soils with seasonally
perched water tables, J. Env. Qual. 4:382-388.
' 2. Cogger, C., B.L. Carlile, D. Osborne, E.A. Holland, 1982.
Design and Installation of Mound Systems for Waste Treatment
and Disposal Systems, University of North Carolina SeaGrant
College Pub. UNC-SG-82-04:31 p..
3. Environmental` Protection Agency, 1980. Design Manual Onsite
' Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391.. p.
4. Triangle J Council of Governments, 1978. Task B: Summary
' of Alternative, On -site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99'p.
' 5. Triangle J Council of Governments 1980. Task C:
Demonstration and Evaluation of Alternative Onsite Treatment
and Disposal Methods, Research Triangle Park, NC, 83 p.
1 '

37
2. SEPTIC TANK/EVAPOTRANSPIRATION BED
A septic tank/evapotranspiration bed (ET) is an on -site '
wastewater treatment, and disposal system which utilizes a septic
tank for initial treatment. A gravel and sand bed with an '
impermeable liner, distribution 'piping, and vegetative cover '
serve to dispose of effluent by'evaporation to the atmosphere and
by transpiration through the vegetation (Figure 7). '
Topsoil (Varies.0-4")
S_ lope Filter Cloth or Equivalent
0
CIOImpervious.
O O
Liner N
Sand 2"
Rock. Perforated -
Pipe (4")
FIGURE 7. Cross Section of T ical.Eva otrans iration-Bed ,
YP p . P -
(EPA, 1980).
Wastewater moves from the septic tank to the.bed.by gravity. ,
Effluent is distributed through the bed, with perforated pipe.
Gravel in the bottom of the bed surrounds the distribution pipes
i es '
and acts as a'storage area. Effluent is moved upward through the '
sand by capillary action where it evaporates at the surface and

� 38
also through the plants as roots take in effluent and the leaves
respire it. Vegetation on an ET bed is usually a type of grass..
The area required for an ET bed depends on the, design
' hydraulic loading rate. Estimates for single family dwellings
range from 4,000 to 6,000 square feet.
' Performance
' Evapotranspiration disposal systems are used in areas where
shallow soils, high groundwater, relatively impermeable soils, or
' fractured bedrock preclude subsurface disposal. The most
significant constraint in the use of the ET system is climatic
' conditions. The evaporation rate is affected by precipitation
' wind speed, humidity, solar radiation, and temperature.. Studies
indicate that essentially all precipitation falling on the'ET bed
' infiltrates and become part of the load to be evaporated (EPA,
1980). This raises questions as to the system Is applicability in
' the wetter regions of the country. Systems'in Virginia and North
Carolina have not functioned properly due to seasonal rainy
weather overloading (Triangle J COG, 1980). Indoor ET systems
' have been proposed to extend their use. Bed covers can be
greenhouses or clear plastic. Covered beds can be smaller due to
the load reduction when rainfall is excluded (U.S. Department of
' Energy, 1983). A similar system is the septic tank/constructed
wetlands system. It utilizes vegetation adapted to wet condi-
tions to filter and respire effluent.
0"

39
Basic Components
1. Septic tank
2. Filter sand
3. Washed gravel'
4. Plastic liner'
5. Perforated PVC pipe
6. Topsoil
7. Vegetative Cover
Installation
The ET system can be installed by competent septic tank and
landscaping contractors. A backhoe is usually needed to move
fill into place evacuated for the tank. Grading and leveling of
the bed must be done manually to prevent soil compaction and
damage. Site drainage and protection of the bed from surface
runoff must be provided. A well -maintained vegetative cover is
required for the bed surface.
Cost
An installed ET system will be more costly than a conven-
tional system. This is primarily due to the imported fill
material and topsoil. Labor may involve up to 50 to.100 man-
hours of work depending on the site. Costs for the system start
at $2,500 and can range up to $3,000 depending on the site.
Strengths
1. Overcomes severe site limitations of shallow soil
on high groundwater.

40
Weaknesses
' 1. Higher installation costs.
2. Need for. specialized design. May require more
' inspection time than a conventional system.
3. Climate of area is too wet for ET system to
' function properly without expense of cover.
REFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
' Wastewater Treatment and Disposal Systems, EPA L5 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
' of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
' 3. Triangle J Council of Governments 1980. Task C:
Demonstration and Evaluation of Alternative Onsite
Treatment and Disposal Methods, Research Triangle Park, NC,
1 83 p.
1

-v
41
3. SEPTIC TANK/INTERMITTENT SAND FILTER/SPRAY IRRIGATION
A septic tank/intermittent sand filter/spray irrigation
system accomplishes primary treatment with the septic tank.
Secondary treatment of effluent is accomplished with a sand
filter. This filter can be either a buried or recirculating
type. Effluent passes through.a disinfection system to a pumping
tank. In piedmont. North Carolina, buried dual filters in series
are most typically used. From there it is pumped to a spray
irrigation field for disposal (Figure 8).
An intermittent sand filter is a bed of granular material 24
to 26 inches deep and underlain with collection drains.
Wastewater from the septic tank is intermittently applied to the
surface of the bed where it percolates down to be collected by
the.underdrains. Treatment of the wastewater is accomplished in
the filter by chemical, physical, and biological processes.
Straining .and sedimentation of any suspended solid occurs ,along
with chemical sorption on the granular surfaces. The biological
activity that occurs within the filter, as long as aerobic
conditions are maintained, are the most significant
transformations.
The two more commonly used types of sand filters for single
family dwellings are buried and recirculating. The buried
filter is below grade. Wastewater is distributed through a
network of distribution lines laid in gravel over the surface of
the filter. With the recirculating filter, the surface of the

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. 1 ARCUND SI
1 I
-0QtEPA7:'!E E%!ENSIOr. 'MyfK IN `
CULTURE AND HOME ECONOMICS
Sl.rf QI NOCN f,.t.;UN.
XAI ANpff ACtiCVLTVAAL fwjNtrrr PEP? a W
�C SIMI VN.Vcas"..I t.lf.G1 y ?
,NoGENERAL SITE PLAN
...•f Or AC*,CvffVtf CV`OoftAW4 NO SCALE m F
at
SIDENTIAL SPRAY IRRIGATION —g o
.' sss,'„ISNEET 1 of 2 a
FIGURE 8. General Site Plan; Residential Spray Irrigation (McKaskill, 1988).

TOP SOIL FILL
OwA1NAay/�..e�
Jy:
9A.,
GRADED GRAVEL ryv'
y. .
ai•• TO 2112' q! t
PRA GRAVEL
GRAOED GRAVEL —�
v'T01 va'
RAW WASTE
I
PRETREATMENT
UNIT
43
DISTRIBUTION LATERALS
i • IN. .
�••� ,�
?BIN.
i i IN.
i s IN.
UNDERDRAIN
'TIC
UK DIVERSION
.USHT FILTRA VALVE
DISCNARpE
RECIRCULATION
TANK
SUMP PUMP
FREE ACCESS
SAND FILTER
FIGURE 9. Recirculating Sand Filter (Otis, 1986).

44
filter is left exposed or covered-. with removable covers. A
' recirculating tank receives septic tank effluent and effluent
that is returned from the filter. Wastewater is dosed from the
recirculating tank and a recirculating ratio of 3:1 to 5:1 is
1 maintained.
Before final disposal, disinfection must be accomplished.
' This can be done using several different systems described in
Chapter 7.
' Final disposal involves sending the treated effluent under
' pressure (30 psi) to the sprinkler heads of the spray irrigation
system. The exact configuration of the spray system, dosing
' schedule, field size, and vegetative cores are dependent on the
design wasteload and soils. Generally, three acres are required
' for a system to serve a single family dwelling. This includes
' prescribed buffer strips around the spray field. Fencing is
prescribed as well.
Performance
The effluent from intermittent sand filters is of high
' quality with respect to BOD and suspended solids. Tables 11 and
12 detail this information.
3
Basic Components
1. Septic tank
2. Recirculation tank or 2 pump tanks
' 3. Sand filter
4. Submersible pump and level controls
5. High water alarm

45
1
1
1
TABLE 11. Performance of Buried'Intermittent Filters Receiving
Septic Tank Effluent (EPA, 1980).
FILTER CHARACTERISTICS - EFFLUENT CHARACTERISTICS
EFFECTIVE UNIFORMITY HYDRAULIC '
SIZE COEFFICIENT LOADING DEPTH BOD SS NH3N NO3N
mm gpd/ft2 in. mg/l mg/l mg/t mg/l REFERENCE
0.24
3.9
1
30
2.0
4.4
0.3
25
25
0.30
4.1
1
30
4.7
3.9
3.8
23
25
0.60
2.7
1
30
3.8
4.3
3.1
27
25
1.0
2.1
1
30
4.3
4.9
3.7
24
25
2.5
1.2
1
30
8.9
12.9
6.7
18
25
0.17
.11.8
0.2
39
1.8
11.0
1.0
32
22
0.23-0.36
2.6-6.1
1.15
24
4
12
0.7
17
19

M M M M M M M M M M M M m m r M M M M
TABLE 12. Performance of Recirculating Intermittent Filtersa_(EPA, 1980).
FILTER CHARACTERISTICS
EFFLUENT QUALITY
EFFECTIVE UNIFORMITY
HYDRAULIC
RECIRCULATION
SIZE COEFFICIENT
LOADING
DEPTH
RATIO
DOSE
BOD
SS
NH3N
mm
gpd/ft2
in.
r/Q
mg/l
mg/l
mg/t
MAINTENANCE
REFERENCE
0.6 - 1.0 2.5
-
36
4:1
5 - 10 min.
4
5
-
weed/rake
24
every 30 min.
as req'd.
0.3 - 1.5 3.5
3.0 - S.Ob
24
3:1 - 5:1
20 min.
15.8c
10.Oc
8.4c
rake
26
every 2-3 hr.
weekly
1.2 2.0
3.Ob
36
4:1
5 min. every
4
3-
-
weed
27
30 min.
as req'd.
aSeptic tank effluent.
bBased on forward flow.
cAverage for 12 installations,(household flow to 6,500 gpd plant).

47 '
6. Disinfection system
7. Spray irrigation system (4-6 nozzles, piping; and
fencing)
Installation
A septic tank/intermittent sand filter/spray irrigation
system may be installed by'a competent septic tank and landscap-
ing contractor. A backhoe will be needed for excavation and
moving fill. Electrical service is necessary for the pump.
Proper landscaping and drainage, must be provided to protect the
system from surface runoff.
Cost
Costs for installing this system will be higher than for a
conventional one. Fencing, and the spray irrigation system are
the primary extra expenses. Costs for the system generally start
at $10,000. Operation and maintenance,.costs are associated with
the disinfection system and the pump.
Strengths
1. Overcomes severe site limitations of shallow or
impermeable soils or high groundwater.
2. Conserves water when allowed to use treated
wastewater on lawns, shrubbery, and flower
gardens.
3. Maximizes wastewater disposal through evapotrans-
piration.
Weaknesses
1. As currently regulated, generally unavailable to
area residents'.-
2. Disinfection system requires regular maintenance.
3.. Immediate repair required for pump malfunction.

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
48
REFERENCES -
1. McKaskill, C., 1988.` Regional Engineer North Carolina
Division of Environmental Management (personal
communication).
2.Otis, R.J., 1986. Onsite' Wastewater Treatment:
Intermittent sand filters, in Design Workshop Small
Alternative Wastewater Systems (21 p.), EPA Small Wastewater
Flow Clearinghouse.
3. Rubin, A.R., J. Stewart, and B.L. Carlile, 1978. Important
Considerations for the Land Application of Wastewater,
University of North Carolina Water Resources Research
Institute, 28 p.
4. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p..
5.' Triangle J Council of Governments 1980. Task C:
Demonstration and Evaluation of Alternative Onsite
Treatment and Disposal Methods, Research. Triangle Park, NC,
83 p.

j
49
4. SEPTIC TANK/CONSTRUCTED WETLAND/LEACHFIELD
A septic tank/constructed wetland/leachfield is an on -site '
wastewater treatment and disposal system which uses a.septic tank
for primary treatment, a series of constructed marsh .beds for '
advanced secondary treatment and partial disposal and a leach-
,
field for final disposal of effluent (Figure 10). The marsh beds
are 1.0 to 2.0 feet deep, lined with an impermeable liner, filled
,
with gravel and capped with topsoil. The most appropriate plants
to vegetate a particular system are those wetland plants native
to the area. A mixture of showy flowering species and others
'
gives an aesthetic "flowerbed" look to the system.. Table 13
lists commonly used wetland plants.
'
Treatment occurs in the marsh beds through a series of
'
complex biological reactions. As effluent is pumped or flows by
gravity into the bottom of beds, the gravel substrate acts as a
'
filter. Organics. are degraded by the microorganisms which
colonize the aerobic environment around the wetland plant roots.
'
As these organics are degraded they are made available to the
'
plants as -nutrients. The plants in turn provide the micro-
organisms with oxygen and food. The plants respire a great deal
'
of the effluent as well (Wolverton, 1983 and 1984).
This activity continues year around. Processes are
'
slowed in the winter, but the wetland plant roots are alive and
active during .the nongrowing season (Wolverton, 1988). Experi-

i
;j
a
�.
••III ,��a LEACH FIELD
� , a
SEPTIC TANK .. ; .� r,.��',, y!a�•i,���'•
FIGURE 10. Artificial Marsh Systems for Treating Discharge from Septic Tanks
(Wolverton, 1988).
cn
0

51
ence has shown that effluent coming from the septic tank will be
of such temperature to prevent freezing in the bed (Wolverton,
pers. comm., 1988).
The approximate size for a single family dwelling includes
400 to 500.square feet of beds. The beds are placed in series
and have a length to width ratio of 4 or 51. The bed should be
divided into four or five cells separated bylevel dikes to
enhance treatment by preventing short circuiting. The bottom of
the beds can have a slope no greater than 1% and the top -of the
fill must be level.
TABLE°13. Wetland Plants Used in Constructed Wetlands
(Wolverton, pers. comm., 1988).
COMMON NAME LATIN NOMENCLATURE
Calla lily
Canna lily
Elephant ears
Water iris
Ginger lily
Arrowhead
Pickerelweed
Southern bulrush
Torpedo grass
(Zantedesechia acthiovica)
(Canna flaccida)
(Colacasia esculenta)
(Iris pseudacorus)
(Hed chium coronarium)
(Sagittaria latifolia)
(Pontederia cordata)
(Scirpus californicus)
(Panicum repens)
(P

' 52
1
Performance -
Constructed wetlands are applicable to. areas with shallow
soils, high groundwater, relatively impermeable soils, or
' fractured bedrock. Treatment is achieved within the constructed
bed and high degrees of nutrient removal can be achieved without
' the use of the natural soil or mechanical processes. Ten systems
' for single family dwellings are in operation in Mississippi
(Wolverton, 1988). A system is being installed in East Tennessee
' (Watson, pers.comm., 1988). Systems designed for larger. flows
are used in Pearington; Mississippi, and Vrederburg,.Alabama
' (Wolverton, 1988). Tables 14, 15 and 16 describe the
characteristics of effluent pumped through experimental marsh
beds at the National Space Technology Laboratory.. The data shows
' the comparative effectiveness of several marsh species and
substrates in treatment.
Basic Components
1. Septic tank
2. 1/2 - 1" washed gravel
' 3. Topsoil
4. Impermeable bed liner
5. Dosing pump (optional)
' 6. 6" PVC perforated pipe for inlet and outlets
7. 4" PVC perforated pipe of leachfield
8. Wetland plants (preferably rhizosomes)
1
' Installation
A backhoe will be needed to excavate for the septic tank and
' can be used for the beds or they can be done manually. Care

--v
53
TABLE 14. Artificial Marshes for Treating Discharged Wastewater
from Sewage Lagoon and/or Septic Tanks (Wolverton,
1987).
RETENTION TIME DISSOLVED OXYGEN* BOD5 TEMP
MARSH PLANTS HOURS (DO) mg/l mg/l oC
Arrowhead
(Safittaria latifolia)
24
Pickerelweed
(Pontederia cordata)
24
Canna lily
(Canna flaccida)
24
Southern bulrush
(Sciraus californicus)
24
Torpedo grass
(Panicum reaens)
24
INF.
EFF.
INF.
EFF.
AVG.
1.3
2.2
53
2
20
0.85
2.1
47
8
27
2.5
3.2
42
3
20
2.7
4.1
90
16
21
3.0
-4.0
115
23
22
i
*Average data from two months continuous flow studies.

54
TABLE 15. Artificial Marsh Wastewater Treatment System
Using'Combined.Plant/Rock and P1ant,Carbon•Filters*,
(Wolverton, 1987).
TORPEDO GRASS/ROCK FILTER REED/GRANULAR CARBON FILTER
#1 INF. #2 EFF. #3 EFF.
pH
7.46
7.11
6.87
DO, mg/l
3.35
4.02
5.00
Temp, °C
26.4
25.9
26.2
TSS, mg/l
20.0
5.0
3.0
TDS, mg/l
532.0
323.0
290.0
BOD5, mg/t
130.6
15.0
1.9
NH3-N, mg/l
15.88
13.05
7.18
TOC, mg/t
72.67
32.80
12.73
Trichloroethylene, ppm
3.60
0.0009
<0.0001
Benzene, ppm
7.04
1.52
0.0003
Chlorobenzene, ppm
4.85
1.54
0.0016
Toluene, ppm
5.62
1.37
0.0009
*Average data from four different sampling days.

i
55
TABLE 16. Artificial Marsh Wastewater Treatment System Using
Combined Plant/Rock and Plant/Carbon Filters*
(Wolverton, 1987).
BULLRUSH/ROCK
FILTER
REED/GRANULAR
CARBON FILTER
#1 INF.
92 EFF.
#3
EFF.
pH
6.78
6.62
6.56
DO, mg/t
1.9
4.3
5.0
Temp, oC
21.0
20.5
19.8
TSS, mb/t
39.0
10.0
0.0
TDS, mg/t
403.0
357.0
310.0
BOD5, mg/l
103.0
12.7
<1.0
NH3-N, mg/l
29.0
16.7
2.3
TOC, mg/1
70.0
33.0
13.0
Trichloroethylene, ppm
9.9
0.05
<0.0001
Benzene, ppm
12.0
5.1
0.0005`
Chlorobenzene, ppm
10.65
4.9
0.0050
Toluene, ppm
11.47
4.5
0.0035
*Average data from four different sampling days.

56
should be taken to protect the area of the 'leachfield from
compaction. Beds should be located so as to receive maximum
solar "insulation. This will increase efficiency and allow for
' the best mix of plants to be used. The beds should be protected
from surface runoff.
Cost
Cost should be slightly higher than a conventional system
due to the added expense of the liner, pump, and the wetland
plants. Operating expenses will be negligible. Maintenance
costs will be associated with pump if a pump is needed and
removal of septage for the tank every 3-5 years.
' Strengths
1. Overcomes severe site limitations.
' 2. If a pump is not needed, requires no mechanical parts.
3. Low capital cost and low maintenance.
Weaknesses
' 1. Need for specialized design and supervision in light of
site specific details of topography, drainage, and bed
vegetation.
2. If pump is used, need for immediate repair when failure
occurs.
3. System is not currently in use in North Carolina.
1

57
REFERENCES
1. Watson, J., 1988, personal communication. Water Quality
Branch, Tennessee Valley Authority, Chattanooga, TN.
2. Wolverton, B.C., 1988.Aquatic'Plant Wastewater Treatment
Systems,. presented at National Environmental Health
Association Conference, Mobile, AL, 19 p.
3. Wolverton, B.C., 1987 Natural Systems for Wastewater
Treatment and Water Reuse for Space and Earthly
Applications, Presented at American Water Works
Association, Research Foundation Water Reuse Symposium IV,
Denver, CO, 17 p.
4. Wolverton, B.C., R.C. McDonald, C.C. Myrick, and K.M.
Johnson, 1984. Upgrading septic tanks using microlid/plant
filters, J. MS Acad. Sci. 29:19-25.
5. Wolverton, B.C., R.C. McDonald, `and W.R. Duffer, 1983.
Microorganisms and higher plants for wastewater treatment,
J. Environ. Qual. 12(2):236-242.
6. Wolverton, B.C., 1988, personal communication.

I
58
S. SEPTIC TANK/LOW PRESSURE PIPE DISTRIBUTION
A septic tank /low pressure pipe distribution system (LLP)
is a shallow, pressure closed,, soil absorption system (Figure
11). A septic tank accomplishes primary. treatment. Effluent is
then distributed through a soil absorption field under low
pressure 2-3 psi) in small diameter perforated pipes. The
effluent is uniformly distributed in controlled doses toshallow
trenches. Treatment of the effluent by thewsoil is enhanced by
the distribution method. Local overloading problems are
decreased and the dosing and rest cycles maintain an aerobic
environment. Shallow placement of pipes maximizes the vertical
separation between effluent and are restrictive layers or
seasonally high groundwater. Trenches can be placed as shallow
as 8 to 12 inches.
t 4lFa.c
Se+.IrpK1' $� —• - au�t5s R��CR
p' a
—TUW-LJP
--NV- 4*jFAR1 &L4 PJMPI*.6 -PWK
sePf� taNk
L niSTR �1 flail Ldjtl2AL
FIGURE 11. Basic Components of a Low Pressure Pipe System
(Cogger, et al., 1982).

O
59
The space required for the distribution network of a -single
family dwelling system ranges form 1,000 to 5,000 square feet
depending on soil permeability and design waste load. . An equal
area must also be set aside for a repair area. Generally an
undeveloped lot of greater than an acre are needed for this
system.
Performance
Septic tank/low pressure pipe -distribution systems can
function effectively when design sited, installed, and maintained
property. This system performance- in the central part of the
State has been acceptable (Herring,` pers. Comm., 1988).
Maintenance requirements include septageremoval every 3-5.years,
removal of solids at ends of lateral distribution lines annually
by flushing will a garden hose, routine pump maintenance.
Protection of the absorption field from comnaction nr
removal of topsoil is one of the most important concerns with the
LLP system. No construction should take place when the site is
wet as this will damage the soil. Care must be taken to protect
the system from surface runoff. The absorption field should be
sown to a grassy cover as soon as possible and maintained by
mowing. Electrical service must be provided for the pump.
Cost
The cost of a low pressure pipe system is fairly similar to
a conventional one. The added expense if the extra tank and pump
M

m
will be offset by the savings realized with the reduction in the
excavation and labor for the trenches.. Costs for the system
,generally start at $2,200-$2,500. Operating expenses are
negligible. Maintenance costs will be associated with the pump
and septage removal every 3-5 years.
Strengths
1. Overcomes site limitations of shallow soil or high
seasonal water table.
2. Treatment, absorption and evapotranspiration of
effluent -is maximized by shallow placement of the
distribution system
3. Cost is competitive with a conventional system.
Weaknesses
1. Need for specialized design and supervision.
2. May require more layout and inspection time than
conventional systems.
3. Need for immediate repair when pump fails.
4. Need for maintenance on distribution lines and
PUMP-
1

w
61
REFERENCES -
1. Cogger, C., B.L. Carlile, D. Osborne, E. Holland, 1982.
Design and Installation of Low Pressure Pipe Waste Treatment
Systems, UNC SeaGrant College Pub., UNC-SG-82-03, 31 p.
2. Herring, M., 1988, personal communication. Durham County
Health Department.
3. House, C.H., C.G. Cogger, 1985. Pressure Dosed Septic
Systems: Electric Components and Maintenance, UNC SeaGrant
Pub., UNC-SG-85=06. 25 p.
4. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
5. Triangle J Council of Governments 1980. Task C:
Demonstration and Evaluation of Alternative Onsite Treatment
and Disposal Methods, Research Triangle Park, NC, 83 p.

B. SYSTEMS NOT UTILIZING A SEPTIC TANK
1. AEROBIC UNIT/SOIL ABSORPTION SYSTEM
Aerobic unit/soil absorption or spray irrigation an on -
site wastewater treatment and disposal system which utilizes a
mechanical aerobic unit for primary treatment. Final disposal is
accomplished by either a soil absorption field or spray irriga-
tion field.
Aerobic treatment units can provide a higher quality
effluent than a septic tank when properly designed, installed,
and operated. Aerobic (oxygen rich) treatment can remove
substantial amounts of BOD (Biological Oxygen Demand) and
suspended solids that simple sedimentation cannot. Nitrification
of ammonia occurs under appropriate conditions and pathogenic
organisms are significantly reduced in aerobic unit effluent
(EPA, 1980). Septic tank effluent can be expected to have a BOD
ranging from 120-150 ppm and suspended solids ranging from 40 to
150 ppm. To meet National Sanitation Foundation Class I
standards, effluent from anaerobic units cannot exceed 20 ppm for
BOD and 40 ppm for suspended solids for more than 10 percent of
samples taken in a six month evaluation period.
There are two types or process schemes among commercially
available aerobic treatment units. They are extended aeration
and fixed film. Treatment elements common to both are oxygen
N.
FL_

-v
63
transfer to wastewater, intimate contact between waste and
microbes, and solids separation and removal (EPA, 1980).
a. Extended Aeration
Figure 12 details extended aeration type treatment units.
This treatment process is a modification to the activated sludge
process.. First a high concentration of microbes are maintained
in an aeration tank, followed by separation and recycle of part
of the biomass back to the aeration tank. Wasting of .excess
solids must be done periodically depending on the unit design.
Performance
Extended aeration aerobic treatment units are more complex
than septic tanks and so require significant amounts or regular
operation and maintenance. Table 17 summarizes the field
performance of some of these 'systems. Per is variable.
Factors must commonly adversely affecting performance includes
shock loads,. sludge building, homeowner neglect or abuse, and
mechanical malfunctions. The process is temperature dependent
and so must be,protected from extremes.
Maintenance is crucial to high effluent quality. Table 18
summarizes maintenance suggestions for extended aeration
treatment units. Table 19 'summarizes operational problems,
causes, and remedies. High maintenance requirements are a severe
limitation of the system for general acceptability.

64
Batch -.Extended Aeration
Blower
Influentigh Water
Alarm
�—
Pump Shut-off::!H
—Elevation 1 C� t 11
niffucnr
Influent
Effluent
Pump
Mechanical or
Diffused Aeration
"--Effluent
Settling
Chamber
i
Sludge
Flow -Through Extended Aeration
FIGURE 12. Examples of Extended Aeration Package
Plant Configurations (EPA, 1980).

-v
65
'
TABLE 17.
Summary
of Effluent Data
from Various Aerobic
Unit Field Studies (EPA,
1980).
'
SOURCE
PARAMETER
REF.( 6)
REF.( 1) REF.(10)
REF.( 8)
REF.( 2)
REF.( 4)
REF.( 5)
'
BODS
'
Mean, mg/1
37
37 47
92
144
31
36
Range, mg/L
<1-208
1-235 10-280
-
10-824
9-80
30-170
'
No.of Samples
112
167 86
146
393
10
124
SUSPENDED SOLIDS
Mean, mg/L
39
62 94
94
122
49
57
Range, mg/L
2-252
1-510 18-692
-
17-768
5-164
4-366
No.of Samples
117
167 74
146
251
10
132
t=

M
TABLE 18. Suggested Maintenance for Onsite Extended Aeration
Package Plantsa (EPA, 198o).
ITEM
SUGGESTED MAINTENANCE
Aeration Tank
Check for foaming and uneven air distribution
Aeration System
Check air filters, seals, oil level, back
Diffused Air
pressure; perform manufacturer's required
maintenance.
Clarifier
Check for floating scum; check effluent
appearance; clean weirs; hose down sidewalls
and appurtenance; check sludge return flow
rate and adjust time sequence if required;
located sludge blanket; service mechanical
equipment as required by manufacturer.
Trash Trap
Check for accumulated solids; hose.
down sidewalls.
Controls
Check out functions of all controls and
alarms; check electrical control box.
Sludge Wasting
Pump waste solids as required.
Analytical
Measure aeration tank grab sample for DE,,
MLSS, pH, settleability, temperature;
measure final effluent composite sample
for BOD, SS, pH (N and P if required).
aMaintenance activities should be performed about once per month.
P-

--v
An
TABLE 19. Operational Problems: Extended Aeration
Package Plants (EPA, 1980).
OBSERVATION CAUSE REMEDY
Excessive local
Diffuser plugging
Remove and clean
turbulence in
Pipe breakage
Replace as req'd.
aeration tank
Excessive aeration
Throttle blower
White thick billowy
Insufficient MLSS
Avoid wasting solids
foam on aeration
tank
Thick scummy dark
High MLSS
Waste solids
tan foam on
aeration tank
Dark brown/black
Anaerobic conditions
Check aeration foam
and mixed
Aerator failure
system, aeration
liquor in area-
tank
tion' tank
Billowing sludge
Hydraulic or solids
Waste sludge; check
washout in
overload
flow to unit
clarifier
Bulking sludge
See Ref.,(37)_
Clumps of rising
Denitrification
Increase sludge
sludge in clarifier
-
return rate to
decrease sludge
retention,time
in clarifier
Septic conditions Increase return
in clarifier rate
Fine dispersed floc Turbulence in Reduce power
over weir, turbid aeration tank
effluent
Sludge age Waste.sludge
to .high

68
b. Fixed Film Systems -
Figure 13 depicts three types of on -site fixed film system:
the trickling filter involves gravity flow of wastewater
downward. The upflow filter pumps wastewater upward through the
media. The rotating biological contraction pumps effluent to
partially submerged rotating discs. The principle of treatment
with fixed film systems is that an inert media is employed to
which microorganisms may attach themselves. Wastewater comes in
contact either by moving the media or moving the wastewater.
Oxygen is introduced into the system by natural ventilation or
by mechanical or .diffused aeration with the wastewater (EPA,
1980).
Performance
Fixed film systems are generally less complicated than
extended aeration systems. There has been little long-term field
experience with the system and so data is presently unavailable.
The system is temperature dependent and so should be protected
from extremes. Maintenance suggestions are summarized in Table
20. Operational problems, causes, and remedies are detailed in
Table 21.
Basic Components
A list of aerobic treatment systems included on the National
Sanitation Foundation Standard No. 40 product listing is detailed
1
A--

69
�
Motor
Influent
Effluent
v
• . :. Packed
Media
ROTATING :,
BIOLOGICAL CONACTOR
!Motor,
s�Sludge`•
vo
UPFLOW FILTER =
' Clarifier
Effluent Timer
TRICKLING FILTER c Control
Valve
Influent Distributor I
Influent
Under
Fixed Pump Septic
Media — Tank
—Effluent to Clarifier or Septic Tank
FIGURE 13. Examples of kixed Film Package Plant Configurations
(EPA, 1980).

70
TABLE 20. Suggested Maintenance for -On -Site Fixed Film
Package Plantsa (EPA, 1980).
ITEM SUGGESTED MAINTENANCE
Media Tank Check media for debris accumulation, ponding
and excessive biomass -clean as required; check
underdrains-clean as required; hose down side -
walls and appurtenances; check effluent distri-
bution and pumping -clean as required.
Aeration System, See Table 18
RBC Unit Lubricate motors and bearings; replace seals
as required by manufacturer.
Clarifier See Table 18
Trash Trap See Table 18
Controls See Table 18
Analytical Measure final effluent composite sample for
BOD, SS, pH (N and P if required).
aMaintenance activities should be performed about once per month.
A-

-v
71
TABLE 21. Operational Problems: Fixed Film Package Plants
(EPA, 1980).
OBSERVATION CAUSE REMEDY
Filter ponding
Media too fine
Replace media
Organic overload
Flush surface with
high pressure stream;
increase recycle rate;
dose w/chlorine (10-
20 mg/1 for 4 hrs.)
Debris
Remove debris; provide
pretreatment
Filter flies
Poor wastewater
Provide complete wet -
distribution
ting of media;.increase
recycle rate; chlori-
nate (5 mg/1 for'6 hrs.
at 1 to 2 wk.
intervals)
Odors
Poor ventilation/
Check underdrains;
aeration
maintain aeration
equipment, if
employed; insure
adequate ventilation
increase recycle:
Freezing
Improper
Check and provide
insulation
sufficient insulation
Excessive biomass
Organic overload
Increase recycle; flush
accumulation
surface with high pres-
sure stream;.dose with
chlorine; increase
surface area (RBC)
Low pH; anaerobic
Check venting; pre-
conditions
aerate wastewater
Poor Clarification
Denitrification
Remove sludge more
in clarifier
often
Hydraulic overload
Reduce recycle; provide
flow buffering

72
' in Table 22. These systems have been tested and meet stringent
Y g
' effluent quality.and performance standards.
These units are commercially available. Some can be
' retrofitted in existing septic tanks and others must be purchased
as complete units.
' Extended Aeration
' 1. Aeration chamber with mechanical aerating device
2. Settling chamber
3. Soil absorption field or spray irrigation system
' and field.
Fixed Film
' 1. Contact chamber with fixed media
2. Some with motion to move media or wastewater
3. Clarifier
' 4. Soil absorption field or spray irrigation system
and filled
' Installation
For systems that can be installed in existing septic tanks,
' the tank must be pumped out, and electrical service installed.
' For systems that come as complete units, installation must be
done by factory -trained representatives in some cases.
' The drainfield or spray irrigation field for final,di'posal
of wastewater should be installed as detailed elsewhere in this
document.
' Cost
Aerobic units range in price from under $1,000 for a retro-
fitted unit up to several thousand dollars for the new unit by
I A-

-w
73
themselves. Prices vary as so maintenance packages and
warranties from the different manufacturers.
Strengths '
1. An aerobic system will decompose waste faster and
more completely than the standard septic system.
This produces less residual sludge and fewer odor
problems.
2. May in some cases prolong the life of a conven-
tional drainfield by reducing the clogging
potential of effluent.
3. May in some cases rehabilitate a failing drain -
field by introducing oxidized effluent."
Weaknesses
1. Under current policies Of, the North Carolina
Division of Health Services, aerobic units are not
approved for single family dwelling treatment
systems unless an approved management entity is
provided (i.e., homeowners association, sanitary
districts, water and sewer authorities, county) -
(Taylor, pers. comm.)
2. Insufficient field performance data.
3. High operation and maintenance requirements for
complex mechanical devices.
4. High installation costs and potentially high
maintenance and operation costs.
5. Site limitations of restrictive soils are not
overcome by unit.

TABLE 22. National
Sanitation Foundation.Standard
No.
40: Product
Listing
for Individual Aerobic Wastewater Treatment
Plants
MANUFACTURER
PLANT DESIGNATION
RATED
CAPACITY
CLASSIFICATION
1.
Aquarobic Limited
Mini -Plant* Model #5429105-54291-15
500 to 1000 gpd
II
171 Roberts.St.; E
(13 Plants in Series)
P.O. Box 704
-----
Pentetaguishana, Ontario
F54191-5-5 - F54291-15-S
500 to 1500 gpd
I
Canada LOK 2PO
(12 Plants in Series)
When used in conjunction with filter
Kit Model 3000, Models 54291-5 -
54291-15 are Class I
2.
Nayadic Sciences, Inc.
Nayadic
R.D. #4, P.O. Box 235
M-6A-F
400
gpd
I
Clarks Summit, PA 18411
M-BA-F
600
gpd
I
M-1050-A-F
800
gpd
I
M-2000A-G
1500
gpd
I
M-6A
400
gpd
II -
M-8A
600
gpd
II
M-1050-A
800
gpd
II
a,
M-2000-A
1500
gpd
R
3:
3.
Multi -Flow Wastewater
Multi -Flow Home Waste Treatment Systems
a i
;i
Treatment Systems, Inc.
Model FTB-0.5
500
gpd
I
2322 East River Road
Model FTB-0.75
750
gpd
I
Dayton, OH 45439
Model FTB-1.0
1000
gpd
I
!,I
Model FTB-1.5
1500
gpd
I
4.
Jet Inc.
Model J-150
500
gpd
I
a
750 Alpha Dr.
Model J-158 A
500
gpd
I
Cleveland, OH 44143
Model J-153
500
gpd
II
i

TABLE 22. Concluded.
5.
Owens Manufacturing &
C een Tank Model 650-500
500
gpd I
Specialty Company
Model 650-1000
1000.gpd
I'
P.O. Box 2443
Model 650-1500
1500
gpd I
Lafayette, LA 70502
6.
Norweco, Inc.
Singulair Model 820
500
gpd I
Firelands Industrial Park
Norwalk, OH 44857
7.
Cromaglass Corporation
Cromaglass Model CA-5
400 gpd II.
P.O. Box 3215
Williamsport, PA 17701
B.
Engineering Corporation
Treatment Plant
199 South Fifth Ave.
Model Western RBC 500
500
gpd I
Columbus, OH 43215
9.
GMS Rotordisk
Individual Aerobic Wastewater
5266 General Rd., Unit 12
Treatment Plant
Mississauga, Ontario
Model S-12 Rotordisk With
Canada L4W 1Z7
Fiberglass Tank
500
gpd I
v
V1
I
M = = r = = = = = = = =.= = M M = M M:

76
REFERENCES
1. Bernhart, A.P., 1967. Wastewater from Homes, University of
Toronto, Toronto, Canada.
2. Brewer, W.S., J..Lucas, and G. Prascak, 1978. An Evaluation
of the Performance of Household Aerobic Sewage Treatment
' Units. J. of. Environ. Health 41:82-85.
3. Environmental Protection Agency, 1980. Design Manual,
Onsite Wastewater Treatment and Disposal Systems, EPA
' 625 1-80-012:391 p.
4. Glasser, M.B., 1974. Garrett County Home Aeration
' Wastewater Treatment Project, ''Bureau of Sanitary.
Engineering, Maryland State Department of Health and Mental
Hygiene, Baltimore, MD.
5. Hutzler, M.H., L.E. Waldorf, and J. Fancy, 1978.
Performance of Aerobic Treatment Units, in Proceedings of
the Second National Home Sewage Treatment Symposium,
' Chicago, IL, December 1977; American. Society of
Agricultural Engineers, St. Joseph, MI, p.149-163.
' 6. Small Scale Waste Management Project, 1978. University of
Wisconsin, Madison, WI, Management of Small Waste.Flows, EPA
600 2/78-173, NTIS Report No. PB 286 560, September, 804 p.
7. Taylor,• G., 1988. Director of Beaufort County Health
Department, personal communication.
8. Tipton, D.W., 1975. Experiences of 'a County Health
Department with Individual Aerobic Sewage Treatment Systems,
Jefferson County Health Department, Lakewood, CO.
' 9. Triangle J Council of Governments, 1980. Task C:
Demonstration and Evaluation of, Alternative Onsite
Treatment and Disposal Methods, Research Triangle Park, NC,
83 p.
10. Voell, A.T. and R.A. Vance, 1974. Home Aerobic Wastewater
' Treatment Systems Experience in a Rural County, presented
at the Ohio Home Sewage Disposal Conference, Ohio State
University, Columbus, OH.
t

2.
77
MICROWAVE UNIT/SOIL ABSORPTION FIELD
OR SPRAY IRRIGATION SYSTEM
The microwave unit/soil absorption field system utilizes a
computer controlled microwave filtration device to accomplish
wastewater treatment, a disinfecting module, and a soil ab-
sorption'field for liquids disposal. The microwave unit consists
of two chambers measuring approximately 3.5' x 2.51 x 2.51 and
weighs 240 pounds. Treatment involves the separation ofthe
solids portion of the wastewater, microwaving the solids portion
to ash, clarification of the liquids portion by ceramic filters,
and disinfection of the filtered effluent by an ozonating module.
Solids treatment and liquids treatment each take about forty
minutes and occur simultaneously. The sterile ash must be
removed periodically. Treated effluent may be disposed of in a
soil absorption field or by spray irrigation.
Performance
This is a very new system and no data is available on field
performance. Table 23 summarizes some effluent data available
from the manufacturer. This system has not as yet been rated by
the National Sanitation Foundation. It is being installed as a
rejuvenation technique for a single family dwelling on -site
system in Durham County, North Carolina, on an experimental.
basis. Maintenance and repair other than ash removal must be
done by factory trained personnel.
9

78
TABLE 23. Effluent Characteristics from Microwave Treatment
Unit (Microwave National, 1987).
WITHOUT 03 WITH 03
PARAMETERS PURIFIER EFFLUENT PURIFIER EFFLUENT
Nitrate (mg/1) .01
5 Day BOD (mg/1) 64
COD (mg/t) 171.36
TOC (mg/t) 62.6
PH 7.69
Total Phosphate (mg/l) 3.59
Total Suspended Solids (mg/t) 66
Turbidity NTU 20
Fecal Coliform col/100 ml 10,000
4.49
5.48
5.04
4
56.16
66.64
65.52
38.9
4.61
41.8
8.01
7.86
•6.48
2.94
2.72
2.90
4
8
4
1.40
1.8
1.5
250
8,000
-

79
Basic Components
1. Interseptic microwave unit
2. Ozone disinfecting module
3. Soil absorption field or spray irrigation field
Installation
The microwave unit can be installed in a basement, garage,
or underground in a 1,000 gallon septic tank with a modified
access hole. Installation of the unit itself must be done by
factory trained representatives. The drainfield or spray
irrigation field can be done, by any competent septic tank and
landscaping contractor. A backhoe will be needed for tank
excavation if that configuration is chosen.
Cost
Interceptor microwave unit $4,585
Ozone disinfection model $800 to $1,200
PVC pipes and fittings
Gravel and sand or spray irrigation system
Labor
Strengths
i. High quality of effluent from treatment unit and
disinfection module
2. Low regular maintenance (ash removal)
3. May rejuvenate clogged soil absorption field
Weaknesses
1. No field performance data available
2. Requires factory trained personnel for installa-
tion and service
3. High capital cost
4. May not overcome severe site limitation of imper-
meable soil
.,E

' 80
REFERENCES
' 1. Brown, A. C., 1988. Home. Incinerator System Could be
Alternative to Septic Tank, Durham Morning Herald.
' 2. Ennis, F., 1988.. Director of Marketing, Microwaste
National, Inc., personal communication.
' 3. Microwaste National Corporation, 1988. Product Literature,
227 Hathaway Street, East, Girard, PA 16417.
1

81
C. MODIFICATIONS TO CONVENTIONAL ON -SITE SYSTEMS.
There are design modifications to conventional on -site
septic systems that can enhance performance on marginally
suitable sites. These modifications seek to optimize the soil's
ability to provide treatment and disposal of wastewater.
1. TRENCH MODIFICATIONS*
Description
Trench shape, depth and width can be modified from the
standard dimensions to maximize the soil's capability of treating
wastewater. Standard nitrification lines are rectangular, 36
inches wide and 2 to 4 feet deep.
V-Ditch: A shape variation is the V-ditch. This shape
increases sidewall to bottom ratio of the trench and capitalizes
on the fact that effluent infiltrates through the sidewall.
Narrower trenches have the more favorable sidewall to bottom
ratio.
Wider trenches are sometimes employed when poor native soil
is replaced with fill material of higher quality. The increased
width is thought to increase aeration and evaporation but
favorably reduced the sidewall to,better ratio. It also requires
more gravel fill than conventional or narrow width trenches.
Shallower trenches maximize utilization of the topsoil for
wastewater treatment and disposal. Nearness to the surface
*Based largely on Triangle J Task C Report.

82
e
allows for a more aerobic environment and so increased biological
' decomposition and evapotranspiration of the effluent. Site
limitations of shallow soil and high groundwater can be overcome.
Installation
Installation is accomplished as it is for conventional
trenches except in the case of the V-ditch. A special V-shaped
' bucket is, required for the backhoe to excavate the trench
properly.
cost
Cbsts will be comparable to standard trenches. Since State
' regulations base system size on total trench bottom are, more
' trench and thus higher cost will be associated with narrower
trenches.
Strengths
1 Variations on trench shape and dimensions may help
' overcome site limitations.
2. Variations can offer simple low cost improvements
to a conventional system.
' 3. Shallower trench depths allow for maximum use of
top soil in wastewater treatment and disposal.
' Weaknesses
1. Narrower trenches systems may be required to have
extra linear footage to comply with codes.
2. With shallower and narrower trenches ponded
effluent has a greater chance of surfacing.

83
m
REFERENCES
1. Environmental.Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA
625 1-80-
'
012:391 p.
2. Triangle J Council of Governments, 1978. Task B:
Summary
of Alternative On -Site Wastewater Treatment and
Disposal
'
Methods, Research Triangle Park, NC, 99 p.
3. Triangle J Council of Governments, 1980.
Task C:
'
Demonstration and Evaluation of Alternative Onsite
Treatment and Disposal Methods, Research Triangle
Park, NC,
83 p.
H

' 84
2. SITE DRAINAGE
' Description
In areas where seasonally high water tables limit the use of
subsurface soil absorption fields for wastewater treatment and
' disposal, site drainage can sometimes be employed. The three
types of drains most commonly used are vertical, curtain, and
' underdrains. Successful design of artificially drained systems
depends on correctly assessing the drainage problem. Attention
must be given to the source of the groundwater and its flow
' characteristics. Soil stratification andgroundwater gradients
are particularly important. Not all sites are suitable for
drainage. Soils that are saturated for long periods, or level
sites are not practical to drain (EPA, 1980).
curtain drains are trench excavations in which perforated
pipes and fill material are placed (Figure 14). they are placed
' on the u slo
a side of the drainfield to intercept groundwater.
P P P
' Often there is sufficient slope, the drains are brought .to the
surface downslope. On level sites, pumps must be used to collect
' the water.
Vertical drains .are similar to curtain drains except that
they are used where the restrictive layer that caused a perched
' water table is thin and have permeable soil beneath. .Vertical
drains penetrate the restrictive layer and allow water to drain
beneath (Figure 15).

85
Curtain
drain
Fill �j' .
R yF °� o��OpbC3b$oo Fill
Material— 4:d�go�4cdd,.
Perched
Water i.' •i" •..:L�;._'. '.o.
TableGravel Filled^`
Above High Absorption
_ _ w Water Table Trenches
Drainage Pipe
—__ Impermeable Layer
FIGURE 14. Curtain Drain to. Intercept Laterally Moving Perched ,
Water Table Caused by a Shallow, Impermeable Layer
(EPA, 1980).
Vertical
Pe
b
Backfill
:Fill
aterial
Gravel Filled
Above High 1
Water Table
Impermeable Layer
Absorption Bed j
:rmeable I _—
Soil
FIGURE 15. Vertical Drain to Intercept Laterally Moving Perched '
Water Table Caused by a Shallow, Thin, Impermeable
Layer (EPA, 1980). '
s .
H

Zi
Underdrains are used where water tables are high and soil
is permeable. The drain is. similar to a curtain drain in
construction, but several may be required to sufficiently lower
the water table (Figure 16).
Underdrains
• �-
ADsorption i I
'
Trenches I
I
r--Fill
Material
`
Gravel Filled
='
Above High
Q
Water
"'rs
Water Table
Tablex
— — — — — — — —
Drainage Pipe /
FIGURE'16. Underdrains Used to Lower Water Table (EPA, 1980).
Installation
Excavation will be required for the drains and pipes. Care
must be take to prevent silt from entering pipes. outlets should
be covered to prevent small animals from entering. If pumping is
required, electricity will have to be insthlled.
Cost
The cost of the additional pipes, fill, excavation, and
labor will increase the cost of a conventional system. If
pumping is required, this will incur additional costs.

87
Strengths
1. Can overcome site limitations and allow a soil
absorption system to be used.
2. Requires little maintenance, unless a pump is
required.
Weaknesses
1. Increases cost of a system.
-2. Not always able to remedy site limitations.
3. Pump requires maintenance.
REFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

88
3. ALTERNATING DUAL DRAINFIELD DISTRIBUTION
Two conventional or modified soil absorption fields are
constructed for a system with a manually operated diversion
' valve. This valve directs effluent from the primary treatment
unit to one of the fields while the other lays idle. Switching
' is done
annually. This gives the idle field time to dry and
' become aerated. This helps to restore the infiltrative
capacities of the trenches. This drainfield design can prolong
, the life of a soil absorption system and make on -site treatment
' and disposal of wastewater possible on marginally suitable soils.
Performance
Used successfully in this area and other parts of country.
Strengths
1. Extends the operating life of a conventional
drainfield on a conventional system in marginally
suitable soils.
' 2. Increases the performance of the drainfield by
allowing it to "rest" .and become aerated.
3. No additional maintenance.
Weaknesses
1. Increased cost of system.
2. Valve must be switched or one drainfield may be
overloaded.
REFERENCES
' 1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA k 5 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

CHAPTER 4`
REJUVENATION TECHNIQUES FOR FAILING SYSTEMS.
i
Soil absorption systems fail when wastewater is received
faster than it can be absorbed' by the soil. The failure
manifests itself with seepage on the ground surface, sluggish
' drains or plumbing backups. Groundwater contamination can also
P g P
occur with no surface evidence of failure and can only be
detected by groundwater monitoring.
Failure stems from hydraulic overloading and soil clogging.
Hydraulic overloading can occur when excessive wastewater is
' discharged from the home or when surface runoff infiltrates the
system. Soil clogging comes from suspended matter in the
effluent, organic matter growing on_ the surface of the soils
' system, by insoluble ferrous sulfide which forms in a saturated
septic environment, and by the breakdown of clay by an excess of
sodium ions in the water (Triangle J, 1978).
Failure occurs as a result of poor siting, poor design, poor
construction, poor maintenance, or a combination of these. The
., techniques in this chapter are intended for systems in soils
which is inherently suitable. Poor initial design or siting will
probably not be overcome by these suggestions.
i
89 .

EEO,
A. EXCAVATION REPLACEMENT OF TRENCH/SOIL INTERFACE
Description
This technique is° suited for clogged soils. It involves
cutting out the clogged interface between the soil and the trench
and replacing it with a mixture of sand and topsoil.
Installation
The septic tank and drainfield must be pumped of effluent to
lower the level of fluid in the nitrification lines. A trencher
can be used to excavate the old trenches along the sidewalls.
Performance
Will only be effective if soil clogging is in fact the cause
of failure.
Cost
Can be costly due to difficulty in following trench lines.
May be more cost effective to extend drainfield instead.
Strengths
1. May restore drainfield.
2. Option for small lots with no room for replacement
drainfield.

M
91
Weaknesses
1. Costs are high and variable.
2. A messy and unpleasant operation.
REFERENCES
1. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
' Methods, Research Triangle -Park, NC, 99 p.

92
B. SHALLOW CROSS -TRENCHING OF EXISTING DRAINFIELD
Description
A series of shallow 4-inch wide trenches are cut at 10 foot
intervals perpendicular to existing nitrification lines.
Trenches are put at a depth slightly below the top of the gravel
around the existing lines. They are then backfilled with gravel
and capped with topsoil. The purpose of the technique is to
increase the amount of sidewall available as an infiltration
surface for effluent. Rater than breaking out at the surface,
any ponded effluent can enter the cross -trenches.
The technique has been used successfully in coastal North
Carolina with the Low Pressure Pipe System.
Installation
The technique is best suited for flat sites with shallow
distribution lines. A small trenching machine can accomplish the
work. Proper landscaping is essential to avoid hydraulic
overloading from surface runoff.
Cost
Relatively inexpensive in cost due to small amounts of
gravel and labor required.
Strengths
1. Cost is low and installation is simple.
•2. Shallow and narrow placement allows. for more
efficient use of the topsoil and lends better
treatment of wastewater.
3. May prolong life of soil absorption field.
4. Well suited for flat lots with shallow soils or
high water tables.

93
Weaknesses
1. Not suitable to all lots, require flat area.
2. Suitable for shallow systems only.
1. Triangle J Council of Governments, 1978. Task.B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

94
C. .DRAINFIELD RESTING
Drainfield resting involves purging the septic tank and
nitrification lines of all effluent ,and allowing the entire
system to dry for several weeks. The technique seeks to reareate
the drainfield, oxidize the soil -clogging matter, and aid the
soil interface in requiring its infiltrative capacity._
To accomplish resting, the system must be pumped completely
of effluent. The system should not be used for several weeks.
Cost
Cost will, be about.,$100 if done by a commercial septic tank
service.
Strengths
1. Inexpensive and simple technique.
2. May remedy clogged soil absorption system.
Weaknesses
1. Inconvenience with not being able to use system.
2. May not remedy problems if anything other than
clogged soil is at fault.
REFERENCES
1. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

' 95
D. AERATION OF SEPTIC EFFLUENT
Description
Use of an aerobic treatment unit may reareate a clogged
' soil absorption system. Use of microwave treatment unit may be
effective in rejuvenating a clogged system as well (See Chapter
2)
' Cost
Retrofit costs vary for aerobic units. Microwave units
' with ozone purifiers are about $6,000 plus labor.
' Strengths
1. May rehabilitate a failing soil absorption system
' by oxidizing soil -clogging matter and ferrous
sulfides.
2. Aerobic and microwave units can decompose waste
' faster and more completely than septic tanks.
Weaknesses
' 1. High cost and potential maintenance problems and
costs.
2. No field performance data is available in our
' area.
3. Aerobic and microwave units are not readily
approved in North Carolina (Taylor, 1988).
REFERENCES
1. Microwaste National, Inc. 1988. Product Literature, 227_•
' Hathaway Street, East, Girard, PA 16417.
2. Taylor, G. 1988. Director, Beaufort County Health
' Department, personal communication.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
' Methods, Research Triangle Park, NC, 99 p.

M.
E. CHEMICAL OXIDATION OF CLOGGED DRAINFIELD
Description
An experimental technique for treating clogged drainfields
is the application of hydrogen peroxide. The chemical acts as an
oxidizing agent and dissolves soil clogging ferrous sulfide and
organic matter. The treatment may allow the soil interface to
regain some or all of its infiltrative capacity. This technique
most be carried out by persons trained in the use of and handling
of the dangerous and caustic hydrogen peroxide. A 50% solution
is needed and about 25 gallons is the volume that should be
pumped into the nitrification lines. The septic system should be
pumped out prior to treatment.
Cost
Not readily available, estimates of $200 - $500.
Strengths
1. May restore a clogged drainfield by dissolving the
organic matter and ferrous sulfide on the soil
interface.
2. Can provide more -immediate results than other
rejuvenation techniques.
Weaknesses
1. No field performance data available.
2. Caustic chemical requires trained person to handle
and apply.

PIFA
REFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

CHAPTER 5
' WATER CONSERVATION PRACTICES AND DEVICES
' Water conservation practices and devices are designed to
accomplish two basic things. First, when employed properly, they
reduce the amount of pure water required for everyday activities.
Secondly, they reduce the amount of wastewater coming from a home
that must be treated before returning it to the environment.
' This will reduce the changes of hydraulically overloading an on -
site system and prolong the system's usable life. Both are
' significant accomplishments in that they save money and conserve
' natural resources. Water conservation requires a large com-
mitment to alter water -consuming habits and a small investment
' in water -saving devices.
A. WATER CONSERVATION PRACTICES
' Water conservation practices involve becoming aware of
wasteful water using habits and altering them. The following is
a list of some of the habits which can help to reduce in home
' water consumption:
' 1. Don't flush the toilet to dispose of a cigarette
butt, tissue, or other unnecessary reason.
2. Repair leaky faucets and toilets.
1 3. Do not run waterwhennot actually using it. For
example, while brushing teeth, shaving, soaping up
' in showers, or when washing dishes by hand.
4. Avoid using automatic clothes washer or -dishwasher
for partial loads. Purchase and use appliances
with low -flow cycles for partial loads.
' 98

99 '
REFERENCES
1. Environmental Protection Ag ency, 1980. Design Manual,
Onsite Wastewater Treatment and Disposal Systems, EPA k 5 1-
80-012:391 p'. '
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site. Wastewater Treatment and Disposal '
Methods, Research Triangle Park, NC, 99 p.

' 100
B. WATER -SAVING TOILETS
' Description
Water -saving toilets can do a great deal to reduce the
' hydraulic load of an on -site wastewater treatment system.
Water -saving toilets using 3.5gallons per flush are now
i required in all new construction n North Carolina.
' To reduce flow in a conventional toilet in an older home,
plastic bottles, bricks, or dams can be placed in the tank (see
' Table 24).
' Very low flush toilets are available that use as little as
.3 to 2.5 gallons per flush. These include washdown flush
' toilets, pressurized tank models, compressed air -assisted flush
toilets, and vacuum -assisted flush toilets. Table 24 sum-
marizes the design and operation details of these toilets.
Cost
' Toilet tank inserts are veryinexpensive, generally under
P g Y
' $10.00. Very -low flow toilets are more costly and can range up
to $400 or more.
Strengths
' 1. Flush modifications are inexpensive.
2. Prolong life of soil absorption system.
3. Little -to -no maintenance requirements.
' 4. Substantial water savings.
' Weaknesses 1. High cost of very low -flow toilet units.
' 2. Bowl may not be completely rinsed on occasion.
0

TABLE 24. Wastewater F1ow.Reduction - Water Carriage Toilets and Systems (EPA, 1980).
DEVELOPMENT APPLICATION OPERATION AND WATER USE TOTAL FLOW
GENERIC TYPE DESCRIPTION STAGEa CONSIDERATIONS MAINTENANCE 'PER EVENT REDUCTIONS
GAL. GPCD %
Toilet with
Displacement devices placed 4-5
Device must be compatible
Post -installation 3.3-3.8 1.8-3.5 4-8
tank inserts
into storage tank of conven-
with existing toilet and
and periodic inspec-
tional toilets to reduce
not interfere with flush
tions to insure
volume but not height of
mechanism.
proper positioning.
stored water.
Varieties: plastic bottles
Installation by owner.
flexible panels, drums or
plastic bags.
Dual flush
Devices made for use with 3
Device must be compatible
Post -installation and 2.5-4.3 3.0-7.0 6-15 C
toilets
conventional flush toilets;
with existing toilet and
periodic inspections
enable user to select from
and not interfere with
to insure proper posi-
2 or more flush volumes
flush mechanism.
tioning and functioning.
based on solid or liquid ,
waste materials.
Installation by owner.
Varieties: many.
Water -Saving
Variation of conventional 5
Interchangeable with
Essentially the same 3.0-3.5 2.7-4.6 6-10
toilets
flush toilet fixture; -
conventional fixture
as for a conventional
similar in appearance and
unit.
operation. Redesign flushing
Requires pressurized
rim and priming jet to
water supply.
initiate siphon flush in
smaller trapway with
less water.
Varieties: Many manufacturers
but units similar.
s
M M M M M M M. M M M M M M M M M M M M 1

M M M M M M M r M MMMM M M M M M- M
TABLE 24. Continued.
r
Washdown flush
Flushing uses only water 3-4
Rough -in for unit may
Similar to conven- 0.8-1.6. 9.4-12.2 21-27
toilets
but substantially less due
be nonstandard.
tional toilet, but
to washdown flush.
more frequent
Drain line slope and
cleaning possible.
Varieties: few
lateral run restrictions
Requires pressurized
water supply.
Pressurized
specially designed toilet 3
Compatible with most any
Similar to conven- 2.0-2.5 6.3-8.0 14-18
tank
tank to pressurize air
conventional toilet unit.
tional toilet fixture.._ .
contained in toilet tank.
Upon flushing, the compressed
Increased noise level. -
air propels water into bowl
at increased velocity.
Water supply pressure of
35 to 120 psi.
N
Varieties: few
Compressed
Similar in appearance 3-4
Interchangeable with rough-
Periodic maintenance 0.5 13.3 30
air -assisted
and user operation to
in for conventional
of compressed air source.
flush toilets
conventional toilet;
fixture.
specially designed to
utilize compressed air
Requires source of
Power use - 0.002 KwH
to aid in flushing.
compressed air; bottled
per use.
or air compressor.
Varieties: few
If air compressor, need
power source.

TABLE 24. Concluded.
vacuum- Similar in appearance
assisted flush and user operation ttl
toitets conventional toilet;
specially designed
fixture is connected to
vacuum system which
assists a small volume
of water in flushing.
Varieties: several
3 Application largely
for multi -unit toilet
installations.
Above floor, rear
discharge.
Drain pipe may be
horizontal or inclined.
Requires vacuum pump.
Requires power source.
Periodic maintenance
of vacuum pump.
Power use = 0.002 KwH
per use.
at a Prototype developed and under evaluation.
2 a Development complete, commercial production initiated, not locally available.
3 a Fully developed, limited use, not locally available, mail order purchase likely.
4 a Fully developed, limited use, locally available from plumbing supply houses or hardware stores.
5 a Fully developed, widespread use, locally available from plumbing supply houses or hardware stores.
bcompared to conventional toilet usage (4.3 gal/flush, 3.5 uses/cap/day, and a total daily flow of 45 gpcd).
0.3 14 31
N
O
W
s

Y
104
REFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
' Wastewater Treatment and Disposal Systems, EPA 625 1-80-
OW2:391 p.
2. Microphor, -Inc.,.1988. .Product Literature, P.O. Box 490,
Willis, CA 95490.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
4. Water Conservation Systems, Inc., 1988. Demonmill Square,
Concord, MA 07142..
1
1
1 �-

105
C. NON -WATER USING TOILETS
There are three types of non -water using indoor toilets,
composting, incinerating,- and oil flush. All of these toilets
are a zero discharging, waterless unit.
Composting toilets come in either self contained units which
accept only toilet waste or as larger units that accept some
kitchen waste as well. Wastes are biologically decomposed with
the addition of heat to dry nutrient rich humus. The humus is
pathogen free and can be used as a soil amendment. A properly
functioning system is odor free. In the States of Maine,
Massachusetts, and Oregon, use of a composting toilet .system
allows for a reduction in the size of the soil absorption field
needed to dispose of the homes grey water. This reduction
varies from 30 to 40 percent (Lombarbo and Associates, 1986).
Installation
Some units require structural modifications to a home. Self-
contained units do not. All units require a ventilation system
and electric power. Installation can be done by a competent
carpenter. ,
Cost
Units range in price from $100 to•$3,300. Installation and
labor costs will vary. Operation and maintenance costs are
negligible.

106
Strengths
1. Uses no water.
2. Residual material is safe and nutrient rich. _
3. Installation can be done by a competent carpenter.
4. Low maintenance required.
5. Operation and maintenance costs are low.
6. May significantly reduce the amount of wastewater
generated and could. result in: a smaller soil
absorption field being needed.
Weaknesses
1. High cost of units.
2. May require modification of site for installation.
3. Gray water disposal system is not addressed.
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
2. Lombardo and Associates, 1986. Novel Alternatives Small
Alternative Wastewater Systems Workshops in Design
Workshop Manual.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
4. Water Conservation Systems, Inc., 1988. Demonmill Square,
Concord, MA 07142. 1

107
Incinerating toilets are. a zero discharging waterless unit
that use high temperature incineration to dispose of liquid and
solid waste. Electricity or gas is used as the fuel source. A
sterile ash is the only residue. Incinerator cycles take from 10
to 15 minutes, and in some'units cannot be interrupted by the
next user.
Installation
All systems require ventilation, electricity, and a fuel
source for incineration. Some units can be installed with little
structural modification while others require more.
Cost
Operating and maintenance costs may be high. Units cost
between $500 and $1,000.
Strengths
1. No water use.
2. Safe residual material.
3. May significantly reduce the amount of wastewater
generated and could result in a smaller. soil
absorption system being needed.
Weaknesses
1. No field performance data.
2. High energy consumption.
3. Potential for high operation and maintenance
costs.
4. Malfunctions require immediate repaired by trained
personnel.
5. In some units, frequent use not possible.
6. Gray water disposal system is not addressed.

108
REFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
Oil -Flush Toilet. The oil -flush toilet. is a waterless,
closed recirculating system that uses clear mineral oil to
transport waste to a storage or treatment container. Treatment
includes clarifying, filtering, and disinfecting the oil. It is
then available for reuse in the toilet. Waste material must be
incinerated, treated, or removed annual from the storage
container.
Components
1. Toilet
2. Oil recycle system
3. Storage and/or treatment system holding tank,
incinerator or aerobia/anaerobic digestion,
Installation
Installation and maintenance must be done by factory trained
personnel. Retrofitting oil flush systems is very difficult.

109
TABLE 25.
Wastewater Flow Reduction
- Non -Water carriage
Toilets
■
(EPA, 1980).
DEVELOPMENT APPLICATION
OPERATION AND
'
GENERIC TTPEa
DESCRIPTION
STAGEb
CONSIDERATIONS
MAINTENANCE
Composting
Small, self-contained
3-4
Installation requires 4-in.
'Removal and disposal
Small
units accept toilet
diameter roof vent.
of composted material
'
wastes only and utilize
quarterly.
the addition of heat in
Handles only toilet waste.
Power use = 2.5 KwH/da
combination with aerobic.
biological activity to
Set usage capacity.
Heat loss through vent
stabilize human excreta.
Power required.
Varieties: -several
I
Residuals disposal.
Composting
Larger units with a
3-4
Installation requires 6-
Periodic addition of
'
Large
separated decomposition
to 12-In. diameter roof
organic matter.
chamber. Accept toilet
vent and space beneath
wastes and other organic -
floor for decomposition
Removal of composted
'
matter, and over a long
chamber.
material at 6 to 24
time period stabilize
month intervals.
excreta through
Handles toilet waste
biological activity.
and some kitchen waste.
Power use = 0.3 to
'
1.2 KwH/day.
Varieties: several
Set usage capacity.
Heat loss through vent'
May be difficult to
retrofit.
Residuals disposal.

110
TABLE 25. Concluded.
DEVELOPMENT
APPLICATION
OPERATION AND
GENERIC TYPEa
DESCRIPTION STAGEb
CONSIDERATIONS
MAINTENANCE
Incinerator Small, self-contained
units which volatilize the
organic components of
human waste and evaporate
the liquids.
Varieties: several
Oil recycle Systems use a mineral oil
to transport human excreta
from fixture (similar in
appearance and use to con-
ventional) to a storage
tank. Oil is purified and
and reused for flushing.
Varieties: few
3 Installation'requires 4-in.
Weekly removal,•
diameter roof vent.
of ash.
Handles only toilet waste.
Semiannual cleaning
and adjustment of
Power or fuel required..
burning assembly
and/or heating
Increased noise level.
elements.
Residuals disposal.
Power use = 1.2 KwH
or 0.3 lb LP gas
per use.
2 Requires separate plumb-
Yearly removal and
ing for toilet fixture.
disposal of extreta
in storage tank.
May be difficult to retrofit.
Yearly maintenance
Handles only toilet wastes.
of oil purification
system by skilled
Residuals disposal.
Power use = 0.01
KwH/use.
allone of these devices uses any water; therefore, the amount of flow reduction is equal to the amount
of conventional toilet use: 16.2 gpcd or 36% of normal daily flow (45 gcpd). Significant quantities
of pollutants (including N, BODS, SS, P, and pathogens) are therefore removed from wastewater stream.
bl = Prototype developed and under evaluation.
2 = Development complete; commercial production initiated, but distribution
may be restricted; mail order purchase.
3 = Fully developed; limited use, not locally available; mail order purchase likely.
4 = Fully developed; limithd use, available from local plumbing supply houses or hardware stores.
5 = Fully developed; widespread use, available from local plumbing supply houses or hardware stores.

Operation and maintenance costs may be high. Oil -flush ,
systems may range in price from several thousand to $10,000
(Triangle J, 1978). ,
Strengths
1. Nondischarging
2. No water needed
Weaknesses
1. High capital costs
,
2. Potential for high maintenance
and operating costs
3. Does not address greywater disposal
4•. Requires major modification to
site
,
5. No field performance data available
6. Repair must be done by factory
trained personnel
7. Residual disposal still needed
,
REFERENCES
,
'
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal
Systems, EPA 625 1-80-
012:391 p.
2. Triangle J Council of Governments,
1978. Task B: Summary
of Alternative On -Site Wastewater
Treatment and Disposal
Methods, Research Triangle Park, NC,
99 p.

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
112
D. FLOW RESTRICTING SHOWERHEADS
Description
Normal showerheads deliver a 4 to 10 gallons per minute flow
rate. Flow restricting devices and water -saving shower heads
attempt to lower, this flow rate. Flow restrictions are small
washer -like inserts that can be installed between the water
supply and the shower head. They are designed to maintain water
velocity and pressure while restricting flow. Low -flow shower -
heads are designed to do the same thing and can be installed as a
unit by the homeowner. Table 26 summarizes the different types
of devices available.
Cost
Most devices are under $20.00.
Strenaths
1. Conserve water.
2. Reduce wastewater generated and so prolong life of
soil absorption field.
3. Energy savings through reduced use of hot water.
Weaknesses'
1. Some devices may reduce pressure and velocity of
water flow.

_M
113
0
TABLE 26. Wastewater Flow Reduction - Bathing Devices and Systems
(EPA, 1980).
DEVELOPMENT
APPLICATION
WATER USE
GENERIC TYPEa'
DESCRIPTION
STAGEb
CONSIDERATIONS
GAL/MIN
Shower flow
Reduce flow rate by
4
Compatible with most
1.5-3.0
control
reducing the diameter of
existing showerheads.
inserts and
supply line ahead of
restrictors
shower head.
Installed by user.
Varieties: many
Reduced -flow
Fixtures similar to
4-5
Can match to most
1.5-3.0
showerheads
conventional, except
plumbing fixture
restrict flow rate.
appearance schemes.
Varieties: many
Compatible with most
manufacturers, but
conventional plumbing.
ON/OFF
Small valve device placed
4
Compatible with most
---
showerhead
in the supply line of
conventional plumbing
valve _
showerhead, allows shower
and fixtures.
flow to be turned on/off
without readjustment of
May be installed by owner.
of volume or temperature.
Thermostatically
Specifically designed valve
3
May be difficult to
---
controlled
controls temperature of
retrofit.
mixing valve
total flow according to
predetermined setting.
Valve may be turned on/off
without readjustment.
Pressure-
Specifically designed valve
4
Compatible with most
---
balanced
maintains constant tempera-
conventional plumbing
mixing valve
ture of total flow regardless
and fixtures.
of pressure changes. Single
control allows temperature
to be preset.

w
114
TABLE 26. Concluded.
Air -assisted Specifically designed 2 May be impossible to
Low -flow system uses compressed air retrofit.
shower system to atomize water flow and
provide shower sensation. Shower location < 50
feet of water heater.
Requires compressed
air source.
Power source required.
Maintenance of
air compressor.
Power use = 0.01 KwH/use.
0.5
allo reduction in pollutant mass; slight increase in pollutant concentration.
bl = Prototype developed and under evaluation.
2 = Development complete; commercial production initiated, but distribution
may be restricted; mail order purchase.
3 = Fully developed; limited use, not locally available; mail order purchase likely.
4 = Fully developed; limited use, available from local plumbing supply houses or hardware stores.
5 = fully developed; widespread use, available from local plumbing supply houses or hardware stores.

115
REFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B:, Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
3. Microphor, Inc., 1988. Product Literature, P.O. Box 490,
Willis, CA 95490.

' 116
E. FLOW RESTRICTING FAUCETS
Description
Faucet inserts and flow restricting aerators or reducing
' flow faucet fixtures are available to reduce the flow of water
used for rinsing activities in sinks and basins.
' All can be installed by the homeowner. Inserts and aerators
' can be attached to existing fixtures. Table 27 summarizes these
devices and their use.
' Cost
Flow restricting aerators generally cost, less than $5.00.
' Reduced flow fixtures are comparable to.standard ones.
' Strengths
1. Easy to install and use,.
' 2. Reduces use of water for rinsing activities.
3. Can reduce hydraulic load to soil absorption
field.
' Weaknesses
1. Inconvenience when doing constant volume uses such
' as filling a bathtub..
' REFERENCES
' 1. Environmental Protection Agency, 1980. Design Manual Onsite,
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
' 2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
' Methods, Research Triangle Park, NC, 99 p.
t

-M
117
TABLE 27. Wastewater Flow Reduction - Miscellaneous Devices
and Systems (EPA, 1980)..
GENERIC TYPEa
DESCRIPTION
DEVELOPMENT
STAGEb
APPLICATION
CONSIDERATIONS
Faucet inserts
Device which inserts
4
Compatible with most
into faucet valve or supply
plumbing.
Line and restricts flow
rate with a fixed or
Installation simple.
pressure compensating
orifice.
Varieties: many
Faucet aerators
Devices attached to faucet
5
Compatible with most
outlet which entrain air
plumbing.
into water flow.
installation simple.
Varieties: many
Periodic cleaning of
aerator screens.
Reduced -flow
Similar to conventional
4
Compatible with most
faucet fixtures
unit, but restrict flow
plumbing.
rate with a fixed or
pressure compensating
Installation identical
orifice.
to conventional.
Varieties: many
Mixing valves
Specifically designed valve
5
Compatible with most
units which allow flow and
plumbing.
temperature to be settwith
a single control.
Installation identical
to conventional.
Varieties: many

118
TABLE 27. Concluded.
Hot water Hot water piping is wrapped 4 May be difficult to
pipe with insulation to reduce retrofit.
installation heat loss from hot water
standing in pipe between
uses.
allo reduction in pollutant mass; insignificant increase in pollutant concentration.
b1 = Prototype developed and under evaluation.
2 = Development complete; commercial production initiated, but distribution
may be restricted; mail order purchase.
3 = Fully developed; limited use, not locally available; mail order purchase likely.
4 = Fully developed; limited use, available from local plumbing supply houses or.hardware stores.
5 = Fully developed; widespread use, available from local plumbing supply houses or hardware stores.
I%,

-.r
119
F. RECYCLE/REUSE
Description
Water recycle/reuse systems collect and treat the entire
wastewater flow of a home or fractions from certain activities
for storage and reuse. Typically these systems collect and
process only the flows from bathing, laundry, and bathroom sinks.
The treated water is then used for toilet flushing and lawn and
garden irrigation. Systems are under development which will
process wastewater and recycle it as a potable water source.
These are very expensive and experimental systems. Table 28
summarizes the details of some of the recycle/reuse systems
currently in use.
Installation
Recycle/reuse systems require substantial modification of
household plumping. The system must be designed to collect the
appropriate flows, send them through a filtration and disinfec-
tion system and then store the treated water for reuse. A pump
is usually required.
Cost
Difficult to estimate and will vary greatly.
Strengths
1. Conserves water.
2. Reduces the hydraulic load for an on -site waste-
water treatment system and hence prolong its
useful life.

TABLE 28. Wastewater Flow Reduction - Wastewater Recycle and Reuse Systems (EPA, 1980).
f
DEVELOPMENT APPLICATION OPERATION AND TOTAL FLOW WASTEWATER
GENERIC TYPE STAGEa CONSIDERATIONS MAINTENANCE REDUCTIONS QUALITY
GCCD % IMPACTS
Recycle bath and
laundry for toilet
flushing
2
Recycle portion of total 3
wastewater stream for
toilet flushing
Requires separate toilet
Periodic replenishment 16 36
Sizeable removals of
supply and drain line
of chemicals, cleaning
pollutants, primarily P.
of filters and storage
May be difficult to
tanks.
retrofit to multi-
story building.
Residuals disposal.
Requires wastewater
Power use.
disposal system for
toilet and kitchen
sink wastes.
Requires separate
Cleaning/replacement 16 36
Significant removals
toilet supply line.
of filters and other
of pollutants.
treatment and storage
May be difficult to
components.
retrofit to multi-
story building.
Residuals disposal.
Requires disposal system
Periodic replenishment
for unused recycle water.
of chemicals.

TABLE 28. Concluded.
Recycle toilet waste-
4 Requires separate
Cleaning/replacement 16 36
Significant removals
water stream for
toilet plumbing network.
of filters and other
of pollutants.
flushing water
treatment components.
carriage toilets
Utilizes low=flush
toilets.
Residuals disposal.
Requires system for'
Power use.
nontoilet wastewaters.
May be difficult
to retrofit.
Application restricted to
high use on multi -unit
installations.
Recycle total
1-2 Requires major variance
All maintenance by •45 100
No wastewater generated
wastewater stream
from State/local health
skilled personnel.
for on -site disposal.
for all water uses
codes for potable reuse.
Routine service check.
Difficult to retrofit. Periodic pump out and
residuals disposal.
Power use.
Comprehensive monitoring
program required.
N
W
P
a1 = Prototype developed and under evaluation. S
2 = Development complete; commercial production initiated, but distribution may be restricted.
3 = Fully developed; limited use, not locally available, mail order purchase likely.
4 = Fully developed; limited use, locally available from plumbing supply houses and hardware stores. l
5 = Fully developed; widespread use, locally available from plumbing supply houses and hardware stores.
bBased on the normal waste flow information resented in Table
r presented MEr

122
Weaknesses
1. Recycled water may not be aesthetically pleasing.
It may be discolored or cloudy.
2. Potentially high installation costs.
3. Maintenance requirements for pump, filtration,
and disinfection systems will be high.
4. Systems are not commonly used in North Carolina at
this time so acceptance by local health officials
and members of the public may be lacking.
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 6 5 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

Cluster or community wastewater treatment and disposal
systems service two or more houses but fewer than entire
communities. The systems are designed to overcome the soil and
size restrictions of individual lots. An alternative sewer
collects wastewater from individual homes and transports it a
short distance to a neighborhood treatment and disposal facility.
This allows for more treatment and disposal options. Treatment
and disposal facilities for cluster systems can include all those
systems discussed in Chapters 2 and 3.
In this chapter alternative collection systems will be
described. Alterative collection systems are most appropriate
in rural areas where population density is low. They are well
suited to service cluster systems because of their lower costs.
Two additional treatment and disposal systems will be
described. These are systems particularly suited to larger
community systems. They are package treatment plants and
lagoons. Final disposal with both systems could be spray
irrigation or discharge to surface waters depending on site
appropriateness.
123
r._ J

124
A. SMALL DIAMETER EFFLUENT SEWER
Description
With this collection system, septic tanks at each home serve
as primary treatment units. Effluent flows from the septic tank
through small diameter:, (4 inch) plastic piping to a central
treatment facility. This facility can be traditional or
innovative in its technology. Small diameter effluent sewers
are installed at shallow depths and'may generally follow the
contour of the land. In very flat or low lying areas.gravity may
not be enough to move effluent through the pipes. A small pump
may be needed. These systems are called Septic Tank Effluent
Pumping (STEP) systems.
The systems were first used extensively in Australia in
areas where homes were too scattered for conventional sewers.
They have been in use in the United States sincee 1961 (Otis,
1986) .
A management authority is needed to oversee operation and
maintenance of the system.
Cost
The small diameter collection system is relatively inexpen-
sive compared with conventional vacuum and pressure sewers.
Pipes are laid more shallow and in narrower trenches which
significantly lowers labor costs. Costs will vary according to
topography, distance, and other site specifications factors.

125
Strengths
1. Relatively low costs
2. Septic tanks provide primary treatment on site rather than
at a central facility.
3. Adaptable to existing developments where homes have septic
tanks.
4. Maintenance is minor. Septic tanks must be pumped of
septage every 3-5 years. The small diameter lines may have
to flushed occasionally to remove slime accumulation. If a
pump is utilized, regular repair and maintenance is needed
(Triangle J, 1978).
Weaknesses
1. Gravity flow may not always be possible and pumps may be
needed to move effluent.
2. Anaerobic septic tank effluent may not be suitable for
addition at aerobic treatment plants.
1. Environmental Protection Agency,'`1987. It's your choice. A
guidebook for local officials on small community wastewater
management options, CPA 430/9-87-006, 73 p.
2. Otis, R.J., 1986. Wastewater Collection Systems, Small
Diameter Gravity Sewers, in EPA Design Workshop Manual.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

-.r
e 126
B. GRINDER PUMP SYSTEM
Description
Grinder pump systems are very similar to small diameter
effluent systems. Instead of using a septic tank at each home
for primary treatment, a grinder pump, much like a garbage
disposal, grinds up solids and pumps the resulting slurry. Small
diameter pipes, 2 to 4 inches, are used to transport sewage to a
central treatment facility.: As with the small diameter effluent
system, pipes may be placed shallowly and in narrow trenches.
A management authority is needed to oversee operation
and maintenance of the system.
Cost
Costs are substantially less than conventional sewers.
Grinder pump maintenance costs may be somewhat more than with a
STEP system.
Strengths
1. Lower costs than conventional sewers.
2. Adaptable to a wide range of topographic situations.
Weaknesses
1. Maintenance requirements are high. Pipes with the grinder
pump system may require more cleaning than small diameter
effluent systems. The grinder pump itself will require more
maintenance than a regular effluent pump.

127
' REFERENCES
' 1. Environment One, 1973. Design Handbook for Low Pressure
Sewer Systems, 5th ed., 2772 Balltown Rd., Schenectady, NY,
28 p.
' 2. Environmental Protection Agency, 1987. It's your choice. A
guidebook for local officials on small community wastewater
management options, CPA 430/9-87-006, 73 p.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC,'99 P.
1

128 '
C. VACUUM SEWER
Description
With a vacuum sewer collection system, septic wastewater
from individual homes flows through a special valve into small
diameter plastic piping where it is transported via a vacuum to a
central vacuuming station. From, there it is pumped to a
treatment facility.
Some systems can'. be, connected to: existing, home plumbing.
Others require special low flush vacuum toilets as part of a
black and greywater separation system.
A management authority is needed to oversee the operation
and maintenance of the system..
Cost
Costs are less than for conventional sewers but vary
according to site factors.
Strengths
1. Costs may be lower than for a conventional sewer system.
2. Septic tank not needed.
3. Adaptable to a variety of sites.
4. Greywater/blackwater separation systems use less water. -
Weaknesses
1. Some systems may require expensive modifications to existing
plumbing.
2. Skilled maintenance required.

F
129
E•0Q0_0c1:4z144*`
1. Brinley, R.K., R.D. Olmstead, and S.M. Wilkinson, 1982.
Design Manual for Pressure Sewer Systems, Peabody Barnes,
651 North Main St., Mansfield, OH, 41 p.
2. Environmental Protection Agency, 1987. It's your choice. A
guidebook for local officials on small community wastewater
management options, CPA 430/9-87-006, 73 p.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC,*99 p.

130
LARGE CLUSTER/COMMUNITY TREATMENT
AND DISPOSAL OPTIONS
A. PACKAGE TREATMENT PLANTS/DISCHARGE OR SPRAY IRRIGATION
Description
Package treatment plants are commercially, available
wastewater treatment plants. They are sold as prefabricated
units or in easily assembled components. The most common units
employ some type of activated sludge process, either extended
aeration or contact stabilization. ' Other biological units
available are mixed and step aeration, trickling filters, and
rotating biological contractors. Physical/chemical systems are
now becoming available as well.
Package treatment plants are available in capabilities
ranging from 500 to several million gallons per day. Table 29
lists details on commercially available biological package
plants. The plant itself provides treatment for the wastewater
which must then be disposed. The options of spray irrigation or
discharge to surface waters are two options discussed.in Chapter
2 which can be meshed with the plant to complete a treatment and
disposal system.
Performance
A detailed performance and development history of extended
aeration and contact stabilization plants is available in reports
by the National Sanitation Foundation (1966, 1968). Generally
treatment performance ranges from 80 to 95 percent removal of BOD
and suspended solids. Plants utilize conventional biological

' 131
TABLE 29. Commercial Biological Package Plants (EPA, 1977).
' MANUFACTURER MODEL CAPACITY (GPD) REMARKS
EXTENDED AERATION
' Bio-Pure Inc.
�
Model BP
600 -
10 000
.
Includes 2-stage batch
9
clarifier and batch
chlorination
Can -Tex Industries
Tex-A-Robic
5,000 -
25,000
Field erected; circular
50,000 -
1,250,000
tank
Clow (AerO-Flow)
Model S,SO, C
1,000 -
100,000
The larger plants must
must be field erected
Davvo
6DA21-12DA40
2,000 -
40,000
50,000 -
500,000
' Defiance of Arizona
1.65 EA-40 EA
1,650 -
40,000
Field erected
Dravo Corp.
Mobilepack E
2,500 -
35,000
Field erected
Aeropack E
30,000
- 2,000,000
Field erected
Lunco Corp.
ADC
2,000
- 1,000.000
Extended Aeration Co.
500
- 46,000
Field erected for sizes
greater than 15,00 gpd
EMC Corp. Environmental
'
Equipment Division
Model SS
1,000
- 5,000
Extend Aeration
7,500
- 15,000
Stepaire
35,000
- 175,000
Field erected
Keene Corp.
Oxy-Pak
1,000
- 20,000
Lakeside Equipment Corp.
EA Aerator Plant
160,000
-
Uses cage rotors for
aeration
Spirojet EA and EAR
2,000
- 12,000
'
Mack Industries
Model MV
1,500
- 150,000
Marolf Hygienic Equip.Co.
Stress -Key
1,500
- 1,000,000
Field erected
Amcodyne E.A. Plants
4,000
- 25,000
'Permutit-Sybron
30,000
- 225,000.
Modulate, field erected
Polcon Corp.
Polcon Package Plant
5,000
- 40,000
Pollution Control, Inc.
Activator S
1,000
- 100,000
Field erected
' Pollutiol Tech., Inc.
Puritrol
1,500
- 25,000
Batch operation
Purestream Indust., Inc.
Model P
3,000
- 100,000
. Puretronics
STP-600
1,000
- 25,000
Purification Sci., Inc.
Ecolog Systems
30,000
30,000
- 1,000,000
Field erected

132
TABLE 29. Continued.
MANUFACTURER MODEL CAPACITY (GPD) REMARKS
EXTENDED AERATION, continued
Richards of Rockford, Inc. Rich -Pak A 10,000 - 500,000
Smith
& Loveless
Model B
15,000
- 35,000
Model D
17,000
- 35,000
Model CY
2,000
- 22,500
Model RE
72,000
- 360,000
Suburbia Systems, Inc.
DCSC-50-DCSC-1000
50,000
- 1,000,000
Stang
Hydronics, Inc.
A-D
1,500
- M,000
Sydnor-Hydrodynamics
Centri-Swirl
2,000
- 50,000
Texas
Tank, Inca
A-D
1,500
- 50,000
Topco
Co.
Aero-Fuse
Water
& Sewage, Inc.
Model EA
3,000
- 20,000
Water
Poll. Cont. Corp.
Sanitaire Mark I & II
1,000
- 35,000
Sanitaire Mark IV
30,000
- 2,500,000
CONTACT STABILIZATION
Can -Tex Industries Tex-A-Robic
Clow (AerO-Flow) Model CS
Davco 11DAC20-12DAC 70
Drava Corp. Mobilpack C
Aeropack C
40,000 -
50,000
50,000 -
1,250,000
50,000 -
500,000
20,000 -
70,000
50,000 -
500,000
10,000 -
20,000
30,000 -
2,000,000
Field erected; requires
construction of lines,
earthen aeration basins
Field erected
Field erected; can also be
operated as conventional,
contact stabilisation or
step aeration process
Factory assembly;
rectangular design
Circular design
Can be operated as
extended aeration plant
at reduced capacity
Factory assembled
Factory assembled;
rectangular design
Factory assembled;
circular design

1
1
1
1
1
1
1
1
1
1
1
1
1
133
TABLE 29. Continued.
MANUFACTURER MODEL CAPACITY (GPD) REMARKS
CONTACT STABILIZATION, continued
EMC Corp. Environmental
Equipment Division ' Stepaire 100,000 - 500,000 Can be operated as
extended aeration or
or contact stabilization
Stabilaire SL-150
20,000 -
500,000
Factory assembled;
rectangular design
Gulfsten Bio-Con
BC20P-BC80P
20,000 -
80,000
Lakeside Equip. Corp.
Spirojet CS
2,500 -
3,000,000
Marolf Hygienic Equip.Co.
50,000 -
3,000,000
Custom designed;
rectangular design
Permutit-Sybron
Amcodyne C.S. Plant
40,Od0 -
1,000,000
Rectangular design
Pollution Control, Inc.
Activator CS
10,000 -
120,000
Purification Sci., Inc.
Contact Stabilization
System
30,000 -
1,000,000
Smith & Loveless
Model B
15,000 -
35,000
Model D
17,000 -
35,000
Model CY
2,000
2,000
Model RE
72,000 -
360,000
Field erected
Model V
2,000 -
90,000
Field erected
Walker Process Equip.
Sparjair
20,000 -
500,000
Circular design
Water & Sewage, Inc.
Model A
15,000 -
50,000
Westinghouse
RCS
10,000 -
50,000
Rectangular units
30,000 -
10000,000
Circular units
STEP -AERATION
EMC Corp. Environmental
Equipment Division Stepaire 100,000 - 500,000 Can be operated as
aeration or contact
stabilization

_M
134
TABLE 29. Concluded.
MANUFACTURER
MODEL
CAPACITY (GPD)
REMARKS
CONVENTIONAL ACTIVATED SLUDGE
EMC Corp. Environmental
Equipment Division
Completaire
15,000 -
25,000
Smith & Loyeless
Model V
2,000
- 90,000
Field erected
Walker Process Equipment
Swirlmix
100,000 -
2,000,000
Water Pollu. Cont., Co.
Sanitaire Mark IV
30,000
- 2,500,000
Field erected; can also be
-
operated as conventional,
contact stabilization or
step aeration process.
COMPLETE MIX
Dorr-Oliver, Inc. 100-500 100,000 - 500,000

135
processes can achieve 80 to 85 percent removal. Plants with
P
physical/chemical options can achieve 90 to 95 percent removal
(Triangle J, 1978). The Extended Aeration process has the
advantage of being able to accept intermittent loading without
becoming upset. Contact stabilization provides similar perfor-
mance but has the advantage of requiring less aeration tank
volume and less compressed air than extended aeration. It has
the disadvantage of being more complicated to operate and
requires more extensive sludge wasting and handling (Triangle J,
1978).
Rotating biological contactors have the advantage of low
maintenance, low power needs, minimal odor, and fly nuisance, and
lownoiselevels. Care must be taken with these plants to
protect them from high winds and vandalism, heavy rains contact-
ing rotating disks, and freezing.
A sanitary engineer or knowledgeable consulting firm should
be employed to assist in selecting the appropriate plant.
Installation
' Package plants should be installed by trained representa-
tives of the manufacturer. The manufacturers should also provide
operation training. For the plant to function effectively it
must not only be installed properly. Most importantly it must be
operated and maintained consistently and carefully by a licensed
' operator.
i --

-.r
136
Cost
Costs of package plants vary greatly due to type of process
used, shipping distance, and installation costs. For illustra-
tive purposes Table 30 displays the total annual cost of a still
extended aeration plant with an expected twenty-year lifetime.
Total annual cost is calculated from capital, installation,
operation, utilities and chemical costs over the expected
lifetime of the plant.
TABLE 30. Total Annual Cost of a Still Extended
Aeration Plant (Triangle J, 1978).
PLANT CAPACITY (gpd) TOTAL ANNUAL COST (1975 DOLLARS)
1,000 $ 4,000
5,000 8,300
10,000 10,500
20,000 14,000
40,000 19,500
100,000 29 500
Strenaths
1. Relatively small area needed.
2. Installation by manufacturer.
3. Possible to sell or move.
4. Possible to expand capacity (Triangle J, 1978).

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
EF
W
EF
SCUM RETURN
FFLUENT AIR LIFT AIR LIN
EIR
E-
EFF:::�F
LUENT
FINAL11 TANK
137
ON TANK TANK
INLET
SLUDGE RETURN
TROUGH J1
INFLUENT
PLAN
AERATION TANK
.-DIFFUSERS
SECTIONAL ELEVATION
TANK INLET
INFLUENT
FIGURE 17. Extended Aeration Treatment Plant with
Air Diffusers (EPA, 1977).

138
BYPASS A
TO
SETTLING
TANK
i
AERATION TANK
A.1
BAR -SCREEN
CHAMBE Ll�NFLUENT
PLAN
SECTION A -A
B SLUDGE
RETURN PUMP
PUMP
PIT
iSCUM LINE
�r
W
EFFLUENT
B -J
-SLUDGE RETURN
F_.WEIR TROUGH rSL'
._._._ DRIVE UNIT, 1 RE
SETTLING TANK
SLUDGE HOI
SECTION B-8
FIGURE 18. Extended Aeration Treatment Plant with
Mechanical Aerator (EPA, 1977).

COMMINUTOR
INFLUENT--k r
Ql WEIR
�v `
'TTROU
139
PR�
DIFFUSER
r—
\F�ER
Q' STILL
P WELL
Vv �
CLARIFIER J"�—
�0 INLET PIPE.
tiT
�cT
coMpARTMENT
t�/PLANT EFFLUENT
// RETURN WASTE
SLUDGE AIRLIFT
d
W
N '
\ W
1r C�
C
C.)
Q
SLUDGE DRAW -OFF
AND PLANT DRAIN
FIGURE 19. Contact Stabilization Plant with
Aerobic Digester (EPA, 1977).

^ `M
140
PISCS
FIRST STAGE
SECOND STAGE
DISC DRIVE MOTOR
EFFLUENT WEIR
r
'
EFFLUENT
DISCHARGE
• ///////
SLUDGE
SCOOP
INLET FROM
,\
\
PRIMARY
CLARIFIER INLET
SLUDGE
SCOOP DRIVE
DISCHARGE
SECONDARY
CLARIFIER
FIGURE 20. Bio-Disc Treatment Plant (EPA, 1977).

141
Weaknesses
1. High total cost especially for small plants.
2. Need for expert engineering selection, design, and
installation.
3. Need for trained, reliable operation and maintenance
by licensed operators (Triangle J, 1978).
1. National Sanitation Foundation, 1966. Package Sewage
Treatment Plants Criteria Development, Part I: Extended
Aeration, FWPCA Grant Project Report no.WPD-74.
2. National Sanitation Foundation, 1968. Package Sewage
Treatment Plants Criteria Development, Part II: Contact
Stabilization, FWPCA Grant Project Report no.WPD-74.
3. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
a
4. U.S. Environmental Protection Agency, 1977. Process Design
Manual, Wastewater Treatment Facilities for Several Small
Communities, 331 p.
.%_

142
1
B. WASTEWATER TREATMENT PONDS/DISCHARGE OR SPRAY IRRIGATION
Description
Wastewater treatment ponds are earthen basins that are open
to the air and sun. Natural biological, physical, and chemical
processes stabilize the wastewater. These processes include
sedimentation, digestion, oxidation, synthesis, photosynthesis,
endogenous respiration, gas exchange, aeration, evaporation,
thermal currents, and seepage (EPA, 1977). There are three
types of ponds.
1. Facultative Pond. these are medium depth (3-6 ft.)
ponds and are sometimes. called oxidation ponds or
aerobic/anaerobic , ponds. In these ponds, an 'aerobic
zone overlies an anaerobic zone. A layer between the
two zones is occupied by facultative bacteria. Solids
in the anaerobic zone undergo fermentation and
hydrolysis. The soluble organics and NH3 then rise to
the .anaerobic zone to be oxidized by the aerobic
bacteria colonizing this zone. Algae at the surface
metabolize CO2 produced and provide needed oxygen to
the aerobic bacteria (EPA, 1977).
Properly operated facultative ponds can provide 80 to 85
percent removal of BOD and 50 to 80 percent removal of suspended
solids. The problems associated with facultative ponds are due
to excessive algal growth and high algal suspended solids in
final effluent (Triangle T, 1978).

' 143
2. Aerated Ponds. These are ponds which. use mechanical
' devices to diffuse oxygen into the wastewater.
Completely mixed aerated ,ponds' keep all solids in.
suspension while in partially mixed aerated ponds only
theupper zone is aerated and the lower zone is
undisturbed (EPA, 1977).
' Aerated ponds are usually seven to 15 feet deep and require
less area than facultative ponds. They can provide 80 to 90
percent removal of BOD and 70 to 85 percent removal of suspended
solids when properly operated. Problems are occasionally
' associated with high suspended solids levels due to excess algal
g P g
' growth (Triangle J, 1978).
3. Anaerobic Ponds., These are typically deep and heavily
' loaded organically. They do not have an aerobic zone
except possibly at the surface. Anaerobic ponds'are
' typically used as primary treatment for waste flows of
' strongly organic composition. They must be followed by
an aerobic treatment process (EPA, 1977).
In an anaerobic pond a thick mat of accumulated solids on
the surface helps to minimize odors produced by the anaerobic
' processes at work on the wastewater. Most pond effluents will
' require additional treatment far suspended solids and
disinfection.
O

ft
144
Installation
Wastewater treatment ponds should be designed by a competent
sanitary engineer or consulting firm. In coastal North Carolina,
an appropriate disposal method will be needed to complete the
wastewater treatment system. Spray irrigation or discharge to
surface waters are two alternatives discussed in Chapter 2 which
could be considered.
Cost
Wastewater treatment ponds can be less expensive than
comparable capacity package plants. Factors affecting the
decision are land costs, excavation costs, and degree of
treatment required.
Strengths
1. Ponds can tolerate considerable variation in organic
and hydraulic loading with little adverse effect on
effluent quality.
2. Ponds require minimal control by relatively unskilled
operators. 1
3. Capital costs and operation and maintenance costs are
low (EPA, 1977).
Weaknesses
1. Large land area is required especially if spray
irrigation is the chosen disposal option.
2. Localized odor problems when pond becomes anaerobic.
3. High accumulation of algal and bacterial cells in
effluent (EPA, 1977).
4. Treatment efficiency depends_ on climate, particularly
temperature and sunlight.

145
REFERENCES
1. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
2. U.S. Environmental Protection Agency, 1977. Process Design
Manual, Wastewater Treatment Facilities for Several Small.
Communities, 331 p.

CHAPTER 7
' DISINFECTION
Disinfection of wastewater is employed as the last step of a.
treatment process before final disposal. Systems detailed in
Chapter 2 requiring disinfection include those utilizing spray
irrigation or discharge to surface waters as disposal methods.
Most are moved from wastewater during treatment in one
pathogens g
' of three ways:
1. Elimination through filtration and sedimentation;
' 2. Organisms die off in unfavorable or hostile
environment; and
3. Harmful organisms are rendered inactive by chemicals
used in the treatment process for purposes other than
disinfection (Triangle J, 1978).
' Disinfection is used to destroy pathogenic organisms that
may still be in the wastewater stream. The disinfector process'
' effectiveness, is measured by the use of indication bacteria
(total or fecal coliform) or, where applicable,. disinfectant
' residual. Neither of these methods guarantees complete destruc-
tion of the pathogens so conservative standards are'used to hedge
against risk (EPA, 1980).
' The most common method of disinfection is chlorination.
Ultraviolet radiation, ozonation, and iodine are also appropriate
' methods of disinfection for on -site wastewater treatment pro-
146

147
cesses. The choice of disinfection method is dependent on the
characteristics of the wastewater, known pathogens it contains,
and method of treatment employed. Disinfection methods vary in
their effectiveness against the different pathogens and in their
compatibility with wastewater streams.
This chapter will summarize information on the most
common disinfection methods.
A. CHLORINATION
Description
Chlorine is a powerful oxidizing agent. It is capable of
oxidizing pathogenic organisms at rapid rates in relatively low
concentrations. It can be used to disinfect wastewater in three
forms; gas, liquid, and solid. The liquid form is a solution of
sodium hypochlorite. The solid is calcium hypochlorite in tablet
form. The liquid and solid forms are more practical for on -site
and flow systems. Chlorine gas can pose a safety hazard and is
highly corrosive so is more difficult to manage (EPA, 1980).
Components
1. Chlorine source: chlorine tablet dispenser, liquid
metering pump, gas chlorinator.
2. Contact Chamber: any container which will allow at
least 20 minutes of detention time (Triangle J, 1978).
Installation
Chlorinators need to be designed, installed and adjusted by
a competent expert in disinfection. The factors of wastewater

148
' temperature, wastewater characteristics, pathogens present,
chlorine residual concentration and content time must all be
considered. It is important that enough chlorine is used to
achieve the desired level of pathogen destruction. When
discharge to surface waters is used the level should not be such
' that aquatic life downstream is harmed. Effluent must be
' regularly monitored to check'chlorine`levels.
Cost
' Chlorinators are available for small flows for $100 to $350
(Triangle J, 1978).
Strengths
' 1. Relatively inexpensive.'
2. Widely available.
' Weaknesses
1. Maintenance requirements are high. Chlorinator must be
monitored regularly.-
2. Certain pathogens, cysts and viruses are not as
sensitive to chlorine.
3. Chlorination produces harmful residuals which can pose
a hazard to aquatic life downstream of discharge.
' REFERENCES
1. Environmental Protection Agency,, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
' 012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
' Methods, Research Triangle Park, NC, 99 p.

_V%
149
B. IODINE
Description
Iodine is chemically similar to chlorine and acts against
pathogens by oxidizing them at rapid rates in relatively low
concentrations. It is used to disinfect wastewater in the
crystalline form. Iodine disinfection systems are commercially
available and require less frequent routine maintenance. Iodine
crystals may last up to a year before dissolving completely.
Effluent must be routinely monitored to assure adequate effec-
tiveness. No toxic by-products from iodine disinfection have been
found at present (EPA, 1980).
Components
1. Iodine crystals.
2. Contact chamber.
Cost
A small iodine disinfection system is available for $200 to
$300 (Triangle, J, 1978).
Strengths
1. Iodine is easier to handle than chlorine.
2. System requires less routine maintenance.
3. Potential for harm to aquatic life downstream of a
discharge is low.
Weaknesses
1. Long term field performance data is not available.
a�.

150
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.
C. OZONE
Description
Ozone is an unstable form of oxygen. It is pale blue,
has a pungent odor, and is a powerful oxidizing agent. Because
of its instability it must be produced on site. To generate the
gas, an electric current is passed through a stream of air.
Ozone is a powerful disinfectant against virus, protozoan cysts,
and vegetative bacteria. It has been found to be more effective
against them than chlorination (EPA, 1980). Ozone's half-life
is short which results in no residuals in discharge which might
harm aquatic life.
Ozonation is a highly technical process and requires
competent experts to install and maintain the system. Long-term.
field performance data is not available. Ozonators are not
readily available commercially. '

_w
Components
1. Ozone generator.
.2. Contact chamber.
Cost
151
Ozonators can start at $1,000.
Strengths
1. Very effective disinfectant.
2. No harmful residual compounds are produced to threaten
aquatic life.
Weaknesses
1. High cost and potential for high maintenance cost.
2. Requires expert installation and maintenance.
3. Not readily available.
REFERENCES-
1. Environmental Protection Agency, 1980. Design Manual Opsite
Wastewater Treatment and Disposal Systems, EPA 625/1-80-
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

' 152
D. ULTRAVIOLET RADIATION
Description
Ultraviolet (UV) rays comprise the shorter wavelengths and
' highest energy band of the visible light spectrum.. UV rays' mode
of action is the denaturation of nucleic acids. This makes UV
especially effective against viruses.
' UV rays can be produced artificially by high intensity, low
pressure mercury vapor lamps. To be effective against pathogens,
tthe UV rays must reach them, so effluent to be disinfected must
be fairly free of suspended solids that might otherwise absorb
' the rays.
' Components
1. Source of ultraviolet light (mercury vapor lamp).
2. Contact chamber which allows effluent to be exposed to
the UV source is a thin film.
Cost
Prices varies depending on size of unit.
Strengths
1. Especially effective against viruses.
2. Produces no harmful residual to affect aquatic life
' downstream.
Weaknesses .
1. Not commercially available for small flows.
2. Suspended solids reduce effectiveness.
3. Potential for high capital costs and operation and
maintenance costs.
1
--

-.%
153
REFERENCES
1. -Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80- ,
012:391 p.
2. Triangle J Council of Governments, 1978. Task B: Summary
of Alternative On -Site Wastewater Treatment and Disposal
Methods, Research Triangle Park, NC, 99 p.

CHAPTER 8
' MANAGEMENT OF ON -SITE SYSTEMS
On -site systems as discussed in this document offer viable
alternative to large municipal sewer systems for small com-
munities. For these on -site systems to provide maximum protec-
tion ofthe public health and prevention of environmental
degradation they must be properly managed. A good management
program performs the following function:
0
1. Site evaluation validation
r2. System design review
3. Construction supervision
4. Operation and maintenance certification
' 5. Rehabilitation assistance
6. Monitoring and enforcement
' 7. Public education activities (EPA, 1980).
In North Carolina, State and local county authorities do
' many of these functions. Effective management programs provide
1 technical assistance along with strong regulation enforcement.
Both elements are crucial to program success. Control over on -
site systems can most logically be exercised at three points in
the system's life: installation, operation, and maintenance.
The successful management program must provide appropriate
guidelines to insure installation in only suitable areas. Proper
design and construction must also be assured. Management can be
imost effective at this point in'avoiding threats to public health
and the environment (EPA, 1980).
154

155
Monitoring operation is the next control point. A
successful management program will provide for monitoring the
operation of on -site systems. This is relatively simple for
conventional systems, but• will take more time with the
alternative ones (EPA, 1980).
Finally, maintenance must be provided. An effective
management program will provide for adequate system maintenance
whether it is carried out by a management entity or by the
homeowner. Failed systems must be detected and rehabilitated or
abandoned. Maintenance such as septage removal should be
required and regulated.
The functions of a management program mentioned earlier must
each be the responsibility of a management entity if the program
is to be effective. There are a number of different options
available including:
1. State agencies
2. Local government/quasi-government units
3. Special purpose districts
4. Private institutions (EPA, 1980).
In North Carolina, the Departments of Environmental Manage-
ment and Human Resources have mandated jurisdiction over on -site
systems. Regional offices of Environmental Management and the
local County Health Departments act to implement regulations
governing the on -site systems under their jurisdictions.

156
Other entities that could be enlisted to provide management
control over on -site systems include quasi -government units such
as regional water quality boards, regional planning commissions,
and councils of government. Special purpose districts are
independent units of government which can be created to provide
one or more services. Legislation must create them, designate
their boundaries, and define their scope and powers. Examples
are water and wastewater districts. Sufficient financial
authority is given them to allow for collection of service
charges and such (EPA,.1980).
' Private institutions are founded on the right of individuals
' and corporations to enter into contracts. Nonprofit institutions
that can provide services for on -site systems include homeowners'
rassociations, private cooperatives, nonprofit corporations.
Private -for -profit institutions are businesses that can enter
' into contract with individual homeowners or homeowner associa-
tions to provide services for on -site systems. Private institu-
tions, both nonprofit. and for -profit, may be regulated by the
' State public services commission or public utility laws (EPA,
1980) .
IREFERENCES
1. Environmental Protection Agency, 1980. Design Manual Onsite
Wastewater Treatment and Disposal Systems, EPA 625 1-80-
012:391 p.
t --

r.«
k
H
A
z
w
a
4!
S

kr
TABLE 1A. Characteristics of Typical Residential Wastewatera.
PARAMETER
MASS LOADING
gm/cap/day
CONCENTRATION
mg/l
Total. Solids
115
- 170
600
- 1000
Volatile Solids
65
- 85
380
- 500
Suspended Solids
35
- 50
100
- 290
Volatile Suspended Solids
25
- 40
150
- 240
BOD5
35
- 50
200
- 290
Chemical Oxygen Demand
115
- 125
680
- 730
Total Nitrogen
6
- 17
35
- 100
Ammonia
1
- 3
6
- 18
Nitrites and Nitrates
< 1
< 1
Total Phosphorus
3
- 5
18
- 29
Phosphate
1
- 4
6
- 24
Total Coliformsb
-
1010
- 1012
Fecal Coliformsb
-
108
- 1010
aFor typical residential dwellings equipped with standard water -
using fixtures and appliances (excluding garbage disposals)
generating approximately 45 gpcd (170 1pcd).
bConcentrati.ons presented in organisms per liter.
Source: EPA, 1980.
A-1

TABLE 2A. Summary of Average Daily Residential Wastewater Flows
(EPA, 1980). '
WASTEWATER FLOW
NUMBER . DURATION STUDY RANGE OF INDIVIDUAL '
OF OF STUDY AVERAGE RESIDENCE AVERAGES
STUDY RESIDENCES (MONTHS) GCPD GPCD
Linaweaver, et at. (1)
22
-
49
36 -
66
Anderson and Watson (2)
18
4
44
18 -.
69
Watson, et at. (3)
3
2-12
53
25 -
65
'
Cohen and Waltman (4)
8
6
52
37.8 -
101.6
Laak (5)
5
24
41.4
26.3 -
65.4
'
Bennett and Linstedt (6)
5
0.5
44.5
31.87 -
82.5
Siegrist, et at. (7)
11
1
42.6
25.4 -
56.9
Otis (8)
21
12
36
8 -
71
'
Duffy, et al. (9)
16
12
42.3
-
Weighted Average
44
'
1. Lineaweaver, F.P., Jr., J.C. Geyer, and J.B. Wolff, 1967. A study of Residential Water
Use, Department of Environmental Studies, Johns Hopkins Univ., Baltimore, MD, 105 pp.
2. Anderson J.S., and K.S. Watson, 1967. Patterns of Household Usage, J. Am. Water Works
Assoc., 59:1228-1237.
3. Watson,K.S., R.P. Farrell, and J.S. Anderson, 1967. The Contribution from the Individual
Home to the Sewer System, J. Water Pollut. Control Fed. 39:2039-2054.
4. Cohen, S., and H. Waltman, 1974. Demonstration of Waste Flow Reduction From Households,
EPA 670/2-74-071, NTIS Report No. PB 236 904, 111 p.
5. Laak, R., 1975. Relative Pollution Strengths of Undiluted Waste Materials Discharge in
Households and the Dilution Waters Used for Each, Manual of Grey Water Treatment Practice -
Part II, Monogram Industries, Inc., Santa Monica, CA.
6. Bennett, E.R., and E.K. Linstedt, 1975. Individual Home Wastewater Characterization and
Treatment, Completion Report Series No. 66, Environmental Resources Center, Colorado State
Univ., Ft. Collins, Co, 145 p.
7. Siegrist, R.L., M. Witt, and W.C. Boyle, 1976. Characteristics of Rural Household
Wastewater, J. Env: Eng. Div., Am. Soc. Civil Eng. 102:533-548.
8. Otis, R.J., 1978. An Alternative Public Wastewater Facility for a Small Rural Community,
Small Scale Waste Management Project, Univ. of Wisconsin, Madison, WI.
9. Duffy, C.P., et at., 1978. Technical Performance of the Wisconsin Mound System for On -Site
Wastewater Disposal - An Interim Evaluation, in Preliminary Environmental Report for Three
Alternative Systems (Mounds) for On -Site Individual Wastewater Disposal in Wisconsin,
Wisconsin Dept. of Health and Social Services, December.
A-2
k

TABLE 3A. Residential Water Use'by Activitya.
ACTIVITY
GPCDb
GAL/USE USES/CAP/DAY
Toilet flush
4.3
3.5
16.2
4.0 - 5.0
23.1 - 4.1
9.2
- 20.0
' Bathing
24.5
0.43
9.2
21.4 - 27.2
0.32 - 0.50
6.3
- 12.5
'
Clothes washing
37_4
0.29
10.0
33.5 40.0
0.25 0.31
7.4
11.6
' Dishwashing
8.8
0.35
3.2
7,.0 - 12.5
0.15 - 0.50
1.1
- 4.9
Garbage grinding
2.0
0.58
1.2
'
2.0 - 2.1
0.4 - 0.75
0.8
- 1.5
Miscellaneous
-
-
6.6
'
5.7
- 8.0
TOTAL
-
-
45.6
41.4
- 52.0
aMean and ranges of
results reported.
bgpcd may not equal
gal/use multiplied
by use/cap/day due
to difference in the number of study
averages used
to
'
compute the mean and ranges shown.
Source: EPA, 1980.
A-3

SOIL PROPERTIES AND SOIL -WATER RELATIONSHIPSI
A.1 Introduction
An understanding of how water moves into and through soil is
necessary to predict the' potential of soil for wastewater
absorption and treatment. Water moves through the voids or pore
spaces within soil. Therefore, the size, shape, and continuity
of the pore spaces are very important. These characteristics are
dependent on the physical properties of the soil and the
characteristics -of water as well.
A.2 Physical Properties of Soil
A.2.1 . Soil Texture
Texture is one of the most important physical properties of
soil because of its close relationship to pore size, pore size
distribution, and pore continuity. It refers to the relative
proportion of the various sizes of solid particles in the soil
that are smaller than 2 mm in diameter. The particles are
commonly divided into three size fractions called soil
"separates." These separates are given in Figure A-1. The U.S.
Department of Agriculture' (USDA) system is used in this manual
(Table A-1).
lEnvironmental Protection Agency, 1980. Design Manual: Onsite
Wastewater Treatment and Disposal Systems, EPA 625 l/80-012.
A-4

SYSTEM
1 U.S. Bureau of Reclamation and Corps of Engineers
(U.S. Department of the Army
2 American Association of State Highway officials
3 knerican Society for Testing and Materials
4 Wentworth
5 U.S. Department of Agriculture
6 International Society of Soil Science
1
%a
3
4
5
0
Sill and Clay
(distinguished on the
Fine sand
Medunn
Coarse
Fine gravel
Coarse
Cobbles
basis of plasllcily)
sand
sand
gravel
Clay
I
Silt
Fine sand
Coarse sand
Fine gravel
Medium
Coarse
Boulders
Colloids
gravel
gravel
Clav
ISilt
Fine sand
Medium
Coarse
Gravel
sand
sand
Colloids
Very
Clay
Sill
Very
fine
Fine
Medium
sand coarse
Pebbles
Cobbles
sand
sand
sand
oars!
Granules
sand
Very
Clay
Very
Sill fine
ne
Medium
coarse
sand
Fine gravel
Coarse gravel
Cobbles
sand
sand
sand
Coarse
sand
Clay
S-11
Fine sand
Coarse sand
Gravel
C. u %0 0 002 002 02 20 20 200
Particle diameter• nim
s
FIGURE A-1. Names and Size Limits of Practical -Size Classes
According to Six Systems (EPA, 1980).
A-5

!r
' TABLE A-1. U.S. Department of Agriculture Size Limits
for Soil Separates (EPA, 1980).
TYLER STANDARD
' SOIL SEPARATE SIZE RANGE (MM) SIEVE NUMBER
'
SAND
2-0.05
10-270
mesh
very coarse sand
2-1
10- 16
mesh
coarse sand
1-0.5
16- 35
mesh
medium sand
0.5-0.25
35- 60
mesh
fine sand
0.25-0.1
60-140
mesh
very fine sand
0.01-0.05
140-270
mesh
'
SILT
0.25-0.002
---
CLAY
<0.002
---
'
Twelve textural classes are defined by the
relative
proportions of the
sand, silt, and clay separates.
These are
represented on the
textural triangle (Figure A-2). to
determine
the textural class
of a soil horizon, the percent by
weight of
the soil separates
is needed. For example, a sample
containing
' 37% sand, 45% silt, and 18% clay has a textural class of loam.
This is illustrated in Figure A-2.
Soil textural classes are modified if particles greater than
' 2 mm in size are present. The adjectives "gravelly," "cobbly,"
and "stony" are used for particles between 2 and 75 mm, 75 and
250 mm, or 250 mm, respectively; if more than 15% to 20% of the
soil volume is occupied by these fragments.
' Soil permeability, aeration and drainage are closely related
to the soil texture because of their influence on pore size and
pore continuity. They are also related to the soil's ability to
' filter, particles and retain or absorb pollutants from the waste
stream. For example, fine textured or clayey soils do not
transmit water rapidly or drain well because the pores are very
small. They tend to retain water for long periods of time.
However, they act as better filters and can retain more chemicals
than soils of other textures. On the other hand, coarse textured
' A-6

FIGURE A-2. Textural Triangles Defining Twelve Textural Classes '
of the USDA. Illustrated for a Sample Containing
37% Sand, 45% Silt, and 18% Clay (EPA, 1980).
A-7 '

' or sandy soils have large, continuous pores that can accept and
transmit large quantities of water. They retain water for only
short periods of time. The capacity to retain chemicals is
generally low and they do not filter wastewater as well as finer
' textured soils. Medium textured or loamy, soils have a balance
between wastewater absorption and treatment capabilities. They
accept and transmit water at moderate rates, act as good filters,
■ and retain moderate amounts of chemical constituents.
A.2.2 Soil Structure
' Soil structure has a significant influence on the soil's
acceptance and transmission of. water. Soil structure refers to
the aggregation of soil particles into. clusters of particles,
called peds, that are separated by surfaces of weakness. The
surfaces of weakness open planar pores 'between the peds that are
often seen as cracks in the soil. These planar pores can greatly
modify the influence of soil texture on' water movement. Well
structured soils with large voids between peds will transmit
water more rapidly than structureless soils of the same texture,
particularly if the soil has become dry before the water is
' added. Fine textured, massive soils (soils with little struc-
ture) have very slow percolation rates.
The form, size and - stability of the aggregates or peds
' depend on the arrangement of the soil particles and the bonds
between the particles. The four major types of structures
include platy, blocky, prismatic, and granular.' Detailed
I descriptions of types and classes of soil structure used by SCS
are given in Table A-2.
Between .the peds are voids which are often relatively large
and continuous compared to the voids or pores between the primary
1 particles within the peds. The type of structure determines the
dominant direction of the pores and, hence, water movement in the
soil. Platy structures restrict vertical percolation of water
' because cleavage faces are horizontally oriented. Often,
vertical flow is so restricted that the upper soil horizons
saturate, creating a perched water table. Soils with prismatic
' and columnar structure enhance vertical water flow, while blocky
and granular structures enhance flow both horizontally and
vertically.
The soil's permeability by air and water is also influenced
' by the frequency and degree of expression of the pores Icreated by
the structural units. These characteristics depend upon the size
of the peds and their grade or durability. Small structural
' units create more pores in the soil than large structural units.
Soils with strong structure have distinct pores between peds.
Soils with very weak structure, or soils without peds or planes
' of weakness, are said to be structureless. Structureless sandy
soils are called single grained or granular, while structureless
clayey soils are called massive.
A-8

TABLE
A-2. Type and Classes of Soil
Structure (EPA,
1980).
TYPE (SHAPE
AND ARRANGEMENT OF
PEDS)
CLASS
Platelike with
Prism -like with
2 dimensions
Block -like, polyhedron
-like, or spheroids, or with 3 dimens-
1 dimension
(the horizontal)
limited and
sions of the same
order of magnitude arranged around a point.
(the vertical)
considerably
less than the
Block -like, blocks or polyhedrons
Spheroids or polyhedrons
limited and
vertical, arranged
around a
having plane or curves surfaces,
having plane or curved sur-
greatly less
vertical line,
vertical faces
that are casts of
the molds,
faces which have slight or
than the other
well defined,
vertices
formed by the faces of the
no accommodations to the
2, arranged
angular.
surrounding peds,
faces of surrounding peds.
around a hori-
zontal plane,
WITHOUT
WITH ROUNDED
Faces flattened,
Mixed rounded
Nonporous Porous peds
faces mostly
ROUNDED CAPS
CAPS
most vertices
and flattened
peds
horizontal
sharply angular
faces with many
rounded vertices
PLATY
PRISMATIC
COLUMNAR
ANGULAR
SUBANGULAR
GRANULAR CRUMB
BLOCKY*
BLOCKY•
�O
Very fine
very thin
very fine
very fine
very fine
very fine
very fine very fine
very thin
platy, <1mm
prismatic,
columnar,
angular blocky,
subangular,
angular crumb
<10mm
<10mm
<5mm
blocky, <5mm
0mm <1mm
Fine or
thin platy, 1
fine pris-
fine columnar,
fine angular
fine subangu-
fine granu- fine crumb
thin
to 2mm
matic, 10
10 to 20mm
blocky, 5 to
tar blocky,
tar 1 to 2mm 1 to 2mm
to 20mm
10mm
5 to 10mm
Medium
medium platy,
medium pris-
medium colum-
medium angular
medium subangu-
medium gran- medium crumb
2 to 5mm
matic, 20 to
nar, 20 to
blocky, 10 to
tar, blocky,'
ular, 2 to 2 to 5mm
50mm
SOam
20mm
10 to 20mm
5mm
Coarse
thick platy,
coarse pris-
coarse colum-
coarse angular
coarse subangu-
coarse granular
or thick
5 to 10mm
matic, 50
nar, 20 to
blocky, 20 to
tar, 20 to
5 to 10mm
100mm
100mm
soma
to 50mm
Very"coarse
very thick
very coarse
very coarse
very coarse
very coarse
very coarse
or very
platy, >10mm
prismatic,
columnar,
angular blocky,
subangular
granular
thick
>100mm
>100mm
>50mm
blocky, >50mm
>10mm
t
M M M M M M M= .= M M M M M M M M M M

Structure is one soil characteristic that is easily altered
or destroyed. It is very dynamic, changing -in response to
moisture content, chemical composition of soil solution,
biological activity, and management practices. Soils containing
' minerals that shrink and swell appreciably, such as montmoril-
lonite clays, show particularly dramatic changes. When the soil
peds swell upon wetting, the large pores become smaller, and
' water movement through the soil is reduced. Swelling can also
result if the soil contains.a high proportion of sodium salts.
Therefore, when determining the hydraulic properties of a soil
for wastewater disposal, soil moisture contents and salt
concentrations should be similar to that expected in the soil
surrounding a soil disposal system.
' A.2.3 Soil Color
The color and color patterns in soil are good indicators of
the drainage characteristics of the soil. Soil properties,
location in the landscape, and climate all influence water
movement in the soil. These factors cause some soils to be
' saturated or seasonally saturated, affecting their ability to
absorb and treat wastewater. Interpretation of soil color aids
in identifying these conditions.
Soil colors are a result of the color of primary soil
particles, coatings of iron and manganese oxides, and organic
matter on the particles. Soils that are seldom or never
saturated with water and are well aerated, are usually uniformly
red, yellow, or brown in color.
Soils that are saturated for
'
extended periods or
all the time
are often grey or blue in color.
Color charts have been developed
for identifying the various soil
colors.
Soils that are
saturated or
nearly saturated during portions
of the. year often
have spots
or streaks of different colors
called mottles.
Mottles are
useful to determine zones of
' saturated soil that may occur only during wet periods. Mottles
result from chemical and biochemical reactions when saturated
conditions, organic matter, and temperatures above 40C occur
' together in the soil. Under these conditions, the bacteria
present rapidly deplete any oxygen present while feeding on the
organic matter. When the oxygen is depleted, other bacteria
' continue the organic decomposition using the oxidized iron and
manganese compounds, rather than oxygen, in their metabolism.
Thus the insoluble oxidized iron and manganese, which contribute
much of the color to soil, are reduced to soluble compounds.
This causes the soil to lose its color, turning the soil grey.
When the soil drains, the soluble iron and manganese are carried
by the water to the larger soil pores. Here they are reoxidized
' when they come in contact with the oxygen introduced by the air -
filled pores, forming insoluble compounds once again. The result
is the formation of red, yellow, and black spots near surfaces,
' A-10

�r
and the loss of color, or greying, at the sites where the iron
and_ manganese compounds were removed. Therefore, mottles seen
in unsaturated soils can be interpreted as an indication that the
soil is periodically saturated. Periodic saturation of soil
cannot always be identified by mottles, however. Some soils can
become saturated without the formation of mottles, because one of
4 the conditions needed for mottle formation is not present.
Experience and knowledge of moisture regimes related to landscape
position and other soil characteristics are necessary to make
proper interpretations in these situations.
Also, color spots and streaks can be present in soils for
reasons other than soil saturation. For example, soil parent
materials sometimes create a color pattern in the soil similar to
mottling. However, these patterns usually can be distinguished
from true mottling. Some very sandy soils have uniform grey
colors because there are no surface coatings on the sand grains.
This color can mistakenly be interpreted as a gley or'a poor
draining color. Direct measurement of zones of soil saturation
may be necessary to confirm the soil moisture regimes if
interpretations of soil colors are not possible.
A.2.4 Soil Horizons
A soil horizon is a layer of soil approximately parallel to
the soil surface with uniform characteristics. Soil horizons are
identified by observing changes in soil properties with depth.
Soil texture, structure, and color changes are some of the
characteristics used to determine soil horizons.
Soil horizons are commonly given the letter designations of
A, B, and C to represent the surface soil, subsoil, and sub=
stratum, respectively. Not all soils have all three horizons.
On the other hand, many soils show variations within each master
horizon and are subdivided as Al, A2, A3, and Bl, etc. Some
example soils and their horizons are shown in Figure A-3.
Each horizon has its ownset of characteristics and
therefore will respond differently to applied wastewater. Also,
the conditions created at the boundary between soil horizons can
significantly influence wastewater flow and treatment through the
soil. Therefore, an evaluation of a soil must .include a
comparison of the physical properties of each horizon that
influences absorption and treatment of wastewater.
A.2.5 Other Selected Soil Characteristics
Bulk density and clay mineralogy are other soil characteris-
tics than can significantly influence water infiltration and
percolation in soils. Soil bulk density is the ratio of the
mass of soil to its bulk or volume occupied by the soil mass and
A-11

DnC2
A - Surface c:,,il
Y B - Subsoil
C - Substratum
TrB
- Surface Soil
- Subsoil
- Substratum
FIGURE A-3. Schematic Diagram of a Landscape and Different
Soils Possible (EPA, 1980).
A-12

�M
pore space. There is not a direct correlation between bulk
density and soil permeability, since sandy soils generally have a
higher bulk density and permeability than clayey soils. However,
of soils with the same texture, those soils with the higher bulk
densities are more compact with less pore volume. Reduced
porosity reduces the hydraulic conductivity of the soil.
Fragipans are examples of horizons that have high bulk densities
and reduced permeabilities. They are very compact horizons rich
in silt and/or sand but relatively low in clay, which commonly
interferes with water and root penetration.
The mineralogy of clay present in the soil can have -a very
significant influence on water movement. Some clay minerals
shrink and swell appreciably with changes in water content.
Montmorillonite is the most common of these swelling clay
minerals. Even if present in small amounts, the porosity of
soils containing montmorillonite can vary dramatically with
varying moisture content. When dry, the clay particles shrink,
opening the cracks between peds. But when wet, the clay swells,
closing the pores.
A.3 Water in the Soil System
A.3.1 Soil Moisture Potential
Soil permeability, or the capability of soil to conduct
water, is not determined by the soil porosity but, rather, the
size, continuity, and tortuosity of the pores. A clayey soil is
more porous than a sandy soil, yet the sandy soil will conduct
much more water because it has larger, more continuous pores.
Under natural drainage conditions, come pores in the soil are
filled with water. The distribution of this water depends upon
the characteristics of the pores, while its movement is deter-
mined by the relative energy status of the water. Water. flows
from points of higher energy to points of lower energy. The
energy status is referred to as the moisture potential.
The matrix potential is produced by the affinity of water
molecules to each.other and to solid surfaces. Molecules within
the body of water are attracted to the solid surfaces by adhesive
forces. The result of these forces acting together draws water
into the pores of the soil. The water tries to wet the solid
surfaces of the pores due to adhesive forces and pulls other
molecules with it due to cohesive forces. This phenomenon' is
referred to as capillary rise. The rise of water is halted when
the, weight of the water column is equal to the force of capil-
larity. Therefore, water rises higher and is held tighter in
smaller pores than in larger pores (see Figure A-4). Upon
draining, the largest pores empty first because they have the
weakest hold on the water. Therefore, in unsaturated soils, the
water is held in the finer pores because they are better able to
retain the water against the forces of gravity.
A-13

It
11
Air Sp aces lSoil Particle
apillary Water
Adsorbed Water
FIGURE A-4. Upward Movement.by Capillarity in Glass
Tubes as Compared with Soils (EPA, 1980).
' The ability of the soil to draw or pull water into its pores
is referred to as its matrix potential. Since the water is held
against the force of gravity, it has a pressure less than
atmospheric. This negative pressure is often referred to as soil
' suction or soil moisture tension. Increasing suction or tension
is associated with soil drying.
The moisture content of soils with similar moisture tensions
varies with the nature of the pores. Figure A-5 illustrates the
change in moisture content versus changes in moisture tensions.
When the soil .is saturated, all the pores are filled with water
' and no capillary suction occurs. The soil _moisture tension is
zero. When drainage occurs, the tensions increase. Because the
sand has many relatively large pores, it drains abruptly at
relatively low tensions, whereas the clay releases only a small
' volume water over a wide tension range because most of it is
strongly retained in very fine pores. The silt loam has more
coarse pores than does the clay, so its curve lies somewhat'
' below that of the clay. The sandy loam has more finer pores than
the sand so'its curve lies above that of the sand.
A-14

—. .�a.� �..i +�.a..�s+rww..iwaanu��ww�u-�.y.r.rµ ♦y •-sY,..�....r.w .�-�..�... � ... .....y. ..-n �.�._.....,..� r.�wr..v..m.�...�
0
60
o�
50
clay
aci 40
o silt loam
30
0 20 sandy loam
010
sand
0 2b 46 60 80 100
Soil Moisture Tension (MBAR)
Soil Drying ---�
FIGURE A-5. Soil Moisture Retention for Four
Different Soil Textures (EPA, 1980).
A.3.2 'Flow of Water in Soil
The flow of water in soil depends on the soil's ability to
transmit the water and the presence of a force to drive it.
Hydraulic conductivity is defined as the soil's ability to
transmit water, and is related to the number, size, and con-
figuration of the pores. Soils with large, continuous water -
filled pores can transmit' water easily and have a high conduc-
tivity, while .soils with small, discontinuous water -filled pores
offer a high resistance to flow, and, therefore, have low
conductivity. When the soil is saturated, all pores are water -
filled and the conductivity depends on all the soil pores.. When
the soil I�edomes unsaturated or dries (see Figure A-5), the
larger pores fill with air, and only the smaller water -filled
pores may transmit the water. Therefore, as seen in Figure A-6,
the hydraulic conductivity decreases for all soils as they dry.
Since clayey soils have more fine pores than sandy soils, the
hydraulic conductivity of a clay is greater than a sand beyond a
soil moisture tension of about 50 mbar.

FIGURE A-6.- Hydraulic Conductivity (K) Soil
Moisture Retention (EPA, 1980).
' Water movement in soil is governed by the total moisture
potential gradient and the soil's hydraulic conductivity. The
direction of movement is from a point .of higher potential
' (gravity plus matrix potential) to a point of lower potential.
When the soil is saturated, the matrix potential is zero, so the
water moves downward due to.gravity. If the soil is unsaturated,
both the gravity and matrix potentials determine the direction of
flow, which may be upward, sideward, or downward depending on the
difference in total potentials surrounding the area. The greater
' the difference in potentials between two points, the more rapid
the movement. However, the volume of water moved in a given time -
is proportional to the total potential gradient and the soils
hydraulic conductivity at the given moisture content. Therefore,
soils with greater hydraulic conductivities transmit larger
quantities of water at the same potential graUient -than soils
with lower hydraulic conductivities.
' A=16

-.r
A.3.3 Flow of Water Through Layered Soils
Soil layers of varying hydraulic conductivities interfere
with water movement. Abrupt changes in conductivity can cause
the soil to saturate to nearly saturate above the boundary
regardless of the hydraulic conductivity of the underlying layer.
If the upper layer has a significantly greater hydraulic
conductivity, the water ponds because the lower layer cannot
transmit the water as fast as the upper layer delivers it. If
the upper layer has a lower conductivity, the underlying layer
cannot absorb it because the.finer pores in the upper layer hold
the water until the matrix potential is reduced to near
saturation.
Layers such as these may occur naturally in soils or as the
result of continuous wastewater application. It is common to
develop a clogging mat of lower hydraulic conductivity at the
infiltrative surface of a soil disposal system. This layer forms
as a result of suspended solids accumulation, biological
activity, compaction by construction machinery, and soil slaking
(3). The clogging mat may restrict water movement to the point
where water is ponded above, and the soil below is unsaturated.
Water passes through the clogging mat due to the hydrostatic
pressure of the ponded water above the pushing the water through,
and soil suction of the unsaturated soil below pulling it
through. f
Figure A-7 illustrates three columns of similar textured
soils with clogging mats in various stages of development. Water
is ponded at equal heights above the infiltrative surface of each
column.
Column A has no' clogging mat so the water, is able to pass
through all the pores, saturating the soil. the moisture tension
in this column is zero. Column B has a permeable clogging mat
developed with moderate size pores. IFlow .into the underlying
soil is restricted*by the clogging mat to a rate less than the
soil is able to transmit it. Therefore, the large pores in the
soil empty. With increasing intensity of the mat, as .shown in
Column C, the flow rate through the soil is reduced to very low
levels. The water is forced to flow through the finest pores of
the soil, which is a very tortuous path. Flow rates through
identical clogging mats developed on different soils will vary
with the soil's capillary characteristics.
A.4 Evaluating Soil Properties
To adequate predict how soil responds to wastewater
application, the soil properties described and other site
characteristics must be identified. The procedures. used to
evaluate soils are described in Chapter 3 of this manual.
A-17

UWater
L'I Clogging Layer
Pore Particle
A B C
FIGURE A-7. Schematic Representation of Water Movement Through
a Soil with Crusts of Different Resistances
(EPA, 1980).
REFERENCES
1. Black, C.A., 1968. Soil Plant Relationships, (2nd ed.),
Wiley, NY, 799 p.
2. Brady, N.C., 1974. The Nature and Properties of Soils (8th
ed.), MacMillan, NY, 655 p.
3. Bouma, J.W., A. Ziebell, W.G. Walker, P.G. Olcott, E.. McCoy,
and F.D. Hole, 1972. Soil Absorption of Septic Tank
Effluent, Information Circular 20, Wisconsin Geological and
Natural History Survey, Madison, 235 p.
4. Bouma, J., 1975. Unsaturated Flow During Soil Treatment of
Septic Tank Effluent, J. Environ. Eng., Am. Soc. Civil Eng.
101:967-983.
A-18

' History Note: Statutory Authority G.S. 130A-355(e);
Eff. July 1, 1982.
' .1953 SEPTIC TANK CONSTRUCTION
' (a) A septic tank shall be watertight, structurally sound,
and not subject to excessive corrosion or decay. Septic tanks
shall be of two -compartment design. The inlet compartment of a
two -compartment tank shall be between two-thirds and three -
fourths of the total tank capacity. A properly designed dosing
syphon or pump shall be used for discharging sewage effluent into
nitrification lines when the total length of such lines exceeds
' 750 linear feet in a single system. When the design daily flow
from a single system exceed 3,000 gallons per day, alternating
syphons or pumps shall be.used which shall discharge to separate
nitrification fields. Discharges from syphon systems shall be of
' such design so as to fill the nitrification lines from 60 percent
to 75 percent of their capacity at each discharge or as required
for pressure distribution systems. Discharges from pump systems
' shall be designed to maximize the distribution of the effluent
throughout the system. Septic tanks installed where the top will
be deeper than 30 inches below the finished grade shall have an
' access manhole, with cover, extending to within 12 inches of the
finished grade, having a minimum opening adequate to accommodate
the installation or removal of the septic tank lid. Pump or
dosing chambers shall have an access manhole having a minimum
diameter of 30 inches extending a minimum of six inches above the
finished grade. Syphon dosing chambers shall be designed in
accordance with the minimum dose requirements in this rule.
' Effluent pump chambers shall meet the construction requirements
of this section and shall have a minimum liquid capacity
equivalent to the septic tank liquid capacity required in this
rule. All effluent pump chambers shall have a properly function-
ing high-water alarm installed independent of.the electrical
circuit for the pump.
.(b) Minimum liquid capacities for septic tanks shall be in
' accordance with the followings
(1) Residential
Septic
Tanks
(for each
individual
' residence.or
dwelling unit):
NUMBER OF
MINIMUM
LIQUID
EQUIVALENT CAPACITY
BEDROOMS
CAPACITY
PER BEDROOM
' 2 or less
750
gals.
375
gals.
3
900
gals.
300
gals.
4
.1,000
gals.
250
gals.
' 5
1,250
gals.
250
gals.
B-1

�Y
The figures in the preceding table provide for use
of garbage grinders, automatic clothes washers,
and other household appliances.
(2) Septic tanks for large residences or places of
business or public assembly shall be in accordance
with the following:
(A) The minimum liquid capacity of septic tanks
for places of business or places of public
assembly with a design sewage flow of 600
gallons per day or less shall be determined
in accordance with the following: V = 2Q;
where V is the liquid capacity of the septic
tank and Q is the design daily sewage flow.
(B) Individual residences with more than five
bedrooms, multiple -family residences, or any
place of business or public assembly where
the design sewage flow is greater than 600
gallons per day, but less than 1,500 gallons
per day, the liquid capacity of the septic
tank shall be designed in accordance with the
following: V = 1.17Q + 500; where V is the
liquid capacity of the septic tank and Q is
the design daily sewage flow.
(C) Where the design sewage flow is 1,500 gallons
per day or greater, the liquid capacity of
the septic tank shall be designed in
accordance with the following: V = 0.75Q +
1,125; where V is the liquid capacity of the
septic tank and Q is the design daily sewage
flow.
(3) The minimum capacity of any septic tank or
effluent pump chamber shall be 750 gallons.
History Note: Statutory Authority G.S. 130A-335(e);
Eff. July 1, 1982.
.1953 PREFABRICATED TANKS,
(a) When prefabricated concrete tanks or tanks of other
material are used, they shall be -constructed in accordance
with the plans which have been approved by the State
Department of Human Resources and shall comply with all
requirements of this section. Three complete sets of plans
and specifications for the design of the prefabricated
septic tank shall be submitted to the Environmental Health
Section, Division of Health Services, P.O. Box 2091,
D

4.
' Raleigh, North Carolina 27602-2091. These plans and
specifications shall show the design of the septic tank in
detail, including:
(1) All pertinent dimensions;
(2) Reinforcement material;
(3) Material strength;
' (4) Liquid depth;
(5) Cleanout provisions;
(6) Other design features —
History Note: Statutory Authority G.S. 130A-335(e);
' Eff. July 1, 1981.
.1954 MINIMUM STANDARDS FOR PREFABRICATED SEPTIC TANKS
' (a) The following are minimum standards of design and
construction of precast reinforced concrete septic tanks:
(1)
The minimum requirement for the liquid depth is 36
'
inches.
(2)
A minimum of nine inches freeboard is required,
'
the freeboard being the air space between the top
of the, liquid and the bottom side of the lid or
cap of the tank.
(3)
The length of the septic tank shall be at least
twice as long as the width.
'
(4)
There shall be three inlet openings in. the tank,
one on the tank end and one on each sidewall of
the inlet end of the. tank. The blockouts for
'
these openings shall leave a concrete thickness of
not less than one inch in� the tank wall. The.
blockouts shall be made for a minimum of four -inch
'
pipe or a maximum of six-inch pipe.
(5)
The inlet in the tank shall be a straight pipe.
(6)
The outlet shall be a cast -in -place concrete
sanitary tee, a polyvinylchloride (PVC) sanitary
'
tee, or a polyethylene (PE) sanitary tee, made of
not less than class 160 pipe or equivalent
fittings and pipe. Class 160 pipe shall have a
wall thickness of not less than 0.183 inches. The
cast -in -place concrete sanitary tee shall have a
minimum thickness of not less than two inches.
The tee shall extend down one-fourth of the liquid
depth. The invert of the outlet shall be at least
two inches lower in elevation than the invert of
'
the inlet.
' B-3

(7) All tanks shall be manufactured with a cast -in -
place partition so that the tank contains two
compartments. The partition shall be located at a
point not less than two-thirds nor more than
three -fourths the length of the tank from the
inlet end. The top of the partition shall
terminate two inches below the bottom side of the
tank top in order to leave space or air or gas
passage between compartments. The top and bottom
halves of the partition shall be cast in such
manner as to leave a water passage slot four
inches high for the full width of the tank. The
partition (both halves) shall be reinforced by the
placing of six-inch by six-inch NO. 10 gage welded
reinforcing wire. The reinforcing wire shall be
bent to form an angle of 90 degrees on the ends in
order to form a leg not less than four inches
long. When the wire is placed in the mold, the
four -inch legs should lay parallel with the
sidewall wire and adjacent to it. It is recog-
nized that there are other methods of constructing
a partition or two -compartment tank. Any method
other than the one described will be considered on
an individual basis for approval by the division
of health services. However, the tank wall
thickness must remain not less than two and one-
half inches thick throughout the tank except for
blockouts.
(8) Adequate access openings must be provided in the
tank top. Access shall be provided for cleaning
or rodding out of the inlet pipe, for cleaning or
clearing the air or gas passage space above the
partition, an entrance for inserting the suction
hose for tank pumping, and for entrance of a
person if internal repairs are needed after
pumping. This shall be accomplished by properly
locating two manholes with each having a'minimum
opening of 18 inches by 18 inches as the opening
cuts the plane of the bottom side of the top of
the tank. The manhole covers shall be beveled on
all sides in such manner as to accommodate a
uniform load of 150 pounds per squire foot without
damage to the cover or the top of the tank. If
the top of the tank is to be multislab construc-
tion, the slabs over the inlet of the tank,
partition, and outlet of the tank must not weigh
in excess of 150 pounds each. Multislab construc-
tion allows for the elimination of the manholes.
Manhole covers, opening covers, or slabs shall
have a handle of steel or other rot -resistant
B-4

material equivalent in strength to a No. 3
'
reinforcing rod (rebar).
(9)
The tank shall be reinforced by using a minimum
_reinforcing .of six-inch by, six-inch No. 10 gage
'
welded steel reinforcing wire. in the top, bottom
ends, and sides of:the tank. The reinforcing wire
shall be lapped at least six inches. The tank top
must be able to withstand a uniform loading of 150
pounds per square foot. If additional reinforcing
is required to accomplish this, it is the
responsibility of the manufacturer to install the
'
added reinforcing. .
(10)
The top, bottom, ends, and sides of the tank must
have a minimum thickness of two and one-half
'
inches.
(11)
A minimum end product strength of 3,000 pounds per
square inch shall be used in the construction of a
'
septic tank. The strength of 3,000 pounds per
square inch must have been reached within 10
percent or 300 pounds per square inch prior to the
tank's being removed from the place of manufac-
'
ture. It shall be the responsibility of the
manufacturer to certify that this condition has
been met prior to shipment. A septic tank shall
'
be subject to testing to ascertain the strength of
the concrete prior to its being approved for
installation. Recognized devices for testing the
strength of concrete include a properly calibrated
'
Schmidt Rebound Hammer or Windsor Probe Test.
Accelerated curing i the mold by use of propane
gas or other fuels is prohibited, except in
'
accordance with accepted methods and upon prior
approval of the division of health services.
(12)
After curing, tanks manufactured in two sections
'
shall be joined and sealed at the joint by the
manufacturer, or my the installer, by using a
mastic sealant or pliable sealant that is both
waterproof and corrosion resistant.
'
(13)
All tanks produced shall bear an imprint identify-
ing the manufacturer, the serial number assigned
to the manufacturer's plans and specifications
'
approved by the division of health services, and
the liquid or working capacity of the tank. This
imprint shall be located to the right of the
blockout made for the outlet pipe on the outlet
end of the tank.
. (b) Plans for prefabricated tank, other than those for
precast reinforced
concrete tanks, shall be approved on an
'
individual basis as determined by the information furnished by
the designer
which indicates the tank will provide equivalent
'
B-5

effectiveness as those designed in accordance with the provisions
of .1954(a).
(c) Septic tanks other than approved prefabricated tanks
shall be constructed consistent with the provisions of this rule
except as fellows:
(1) Cast -in -place concrete septic tanks shall have a
minimum wall thickness of six inches.
(2) Concrete block or brick septic tanks shall have a
minimum wall thickness of at least six inches when the
design volume is less than 1,000 gallons and a minimum
wall thickness of at least eight inches when the design
volume is 1,000 gallons or more. All septic tanks
constructed of block or brick shall be plastered on the
inside with a" 1:3 mix (one part cement, three parts
sand) of Portland Cement at least three -eighths -inch
thick or the equivalent using other approved water-
proofing materia.
(3) The bottom of the built -in -place septic tank shall.be
poured concrete with a minimum thickness of four
inches.,