Water Quality Systems with Constructed Wetlands-1994-1995

Now limover County Department of Environmental Management
WATER QUALITY SYSTEMS WITH
CONSTRUCTED WETLANDS
An Environmental Education Program
1994 - 1995
THIS PROGRAM SPONSORED IN PART BY A CAMA GRANT FROM THE NORTH CAROLINA DEPARTMENT OF NATURAL RESOURCES, DIVISION OF
COASTAL MANAGEMENT, OTHER SPONSORS INCLUDE GENERAL ELECTRIC COMPANY AND NELSON ENVIRONMENTAL CONSULTING
SERVICES.

INFORMATION PACKET A

The New Hanover County High -Tech Landfill:
How It Came to Be and How It Works
New Hanover County established North Carolina's first landfill utilizing artificial
liners with leachate monitoring and treatment systems in November, 1981. Basically a
response to the County's landfill crisis of 1980, this pioneering facility has been of
invaluable assistance to other communities seeking to develop similar high-tech landfills
and to the State of North Carolina in developing regulations affecting landfills. Moreover,
it affords New Hanover County residents and environmentally secure method of landfill
disposal.
The story of the present New Hanover County Landfill began in 1979 when the
County's contracted landfill, then located near the Flemington Community, was closed
due to alleged groundwater contamination. Numerous lawsuits, including a suit from the
Department of Justice would evolve from this site. The following two sites, the Carolina
Beach and Blue Clay Road Landfills, also contracted, would also draw the County into
litigation. The literally without a landfill for a week, was forced to ship its solid waste to
Raleigh.
Finally, the courts ruled that the County's contractor could operate a temporary
landfill site for a period of one year until a permanent site could be located. Unable to
find a suitable site within the County, the search turned to surrounding Counties with a
regional approach in mind. When the effort to establish a regional landfill proved
fruitless, the County once again mounted a search within its own borders and was able
to locate a site on Hwy 421 North, provided synthetic liners were used.
The use of synthetic liners, wastewater treatment, and monitoring are the keys
that make the New Hanover County Landfill special. The conventional landfill is
basically an excavation cell which is filled with refuse. Refuse is compacted as the
earthen layer of several feet and vegetated. The conventional landfill offers no
mechanisms to protect groundwater from contamination.
The New Hanover County Landfill differs from the conventional type in that each
landfill cell utilizes two synthetic plastic liners which prevent the leaching of
contaminated rainwater into groundwater. This leachate or contaminated rainwater is
pumped from the cell, treated at an on -site wastewater treatment plant, and then
discharged into the Northeast Cape Fear River. Both pretreatment and post -treatment
wastewater is monitored extensively.
Each landfill cell is a self-contained system. When closed, a synthetic plastic cap
is used to seal the cell and prevent the introduction of rainfall, thereby minimizing the
generation of leachate. As well, a "passive" landfill gas collection system has been
installed. Finally, special wells allow the monitoring of groundwater for contamination.

It is perhaps hard to believe that North Carolina's first high-tech landfill was
constructed in a matter of only 90 days. In subsequent years the cell configuration was
modified and improved, synthetic caps replaced clay ones, and improvements in landfill
gas collection system (which will. utilize landfill gas for energy production) loom on the
near horizon. The New Hanover County Landfill is looked to as a model, both from
design as well as operational standpoints, by solid waste experts across North Carolina.
While in the coming years other local governments will be scrambling to bring their
landfills in line with deadlines for the EPA'S Subtitle D regulations, New Hanover County
is already largely in compliance with those regulations. It is truly a facility that the
residents of New Hanover County can be proud of, typifying the lightning pace of solid
waste management improvements made by the County over the last decade.

PROPOSAL
NEW HANOVER COUNTY
DEPARTMENT OF ENVIRONMENTAL MANAGEMENT
TO
DIVISION OF COASTAL MANAGEMENT
CAMA Local Planning and Management Grant(15A NCAC 7L)
New Hanover County's 450 ton per day (TPD) Waste -to -Energy Facility and the 215 acre solid waste
disposal site is managed by the County's Department of Environmental Management. Three people are
primarily responsible for the leachate treatment system in addition to a contract consultant and
temporary employee. The following statements will describe New Hanover County's current involvement
and future planning for leachate treatment.
Background
New Hanover County developed North Carolina's first high-tech double
lined landfill in November, 1981. The site consists of four (4) cells each of
approximately seven (7) acres with leachate collection and pumping
stations. The pump stations deliver leachate to a 2.5 acre four (4) million
gallon lagoon. In March 1983, a 14,000 gpd extended aeration plant was
added to further enhance treatment and in 1992 this was replaced with a
50,000 gpd extended aeration plant. In 1984, North Carolinas's first Waste -
to -Energy Facility opened in New Hanover County with a capacity of 200
TPD. An expansion of this facility was completed in 1991 augmenting its
capacity to 450 TPD. Ash from this facility is disposed at the New Hanover
County secure landfill.
Until 1989, when biomonitoring became an NPDES requirement, the
leachate treatment system was capable of meeting State and Federal
discharge limitations. This new toxicity standard has created a new
challenge in the treatment of leachate and meeting permit requirements.
During this same period a renewed environmental awareness from the
public has intensified with a need to understand and become better
educated of the environmental concerns facing our nation. To meet this
need, education for environmental awareness should begin in our own
communities.

r
t
Scope of Work
Tremendous effort has taken place in the past ten (10) years to evaluate
and optimize the leachate treatment system at New Hanover County's
solid waste disposal site. During the past three years, three personnel
have become involved in an innovative process of compiling information,
analytical data and implementing various treatment techniques within the
current leachate treatment system. Recently, an additional person was
added as temporary staff to meet a need to enhance the capabilities to
organize analytical data and enhance the information system.
It has been determined that an additional stage of treatment is needed to
the present system to enhance the current process and as development to
meet future water quality standards. Constructed wetlands have been
explored and studied. The basis for using the constructed wetland
approach is the result of searching for a low-cost, low tech alternative to
conventional wastewater treatment. Additionally, a method for simple
biological treatment is needed with low maintenance costs that could
continue after post -closure of the disposal site. Several sites utilizing
constructed wetlands to treat various types of wastewater have been
visited (Florida). New Hanover County was recently represented at a
course of study emphasizing constructed wetlands presented by the
University of Colorado.
Currently, New Hanover County is working with NC State University and
Sea Grant with a proposal to develop a demonstration project for a
constructed wetland. This is the initial approach to accomplishing the
goals of maintaining a high -quality stream discharge to meet current and
future water quality standards. A summary of this project is as follows:
Five pilot -scale wetland plots will be constructed at the New Hanover
County Secure Landfill. These wetland plots will be designed after
the two basic constructed wetland types, Free Water Surface (FWS)
and Subsurface (SF). Design variations of these pilot wetland plots
will provide the needed data for a final design recommendation.
P)

Leachate collected from the landfill contains high levels of ammonia
which will lead to ammonia toxicity. Currently, leachate collected
from the landfill is aerobically treated to achieve nitrification,
converting ammonia to nitrate. This treatment system is very
effective in warm weather but not always in cold weather. In
addition, it would be desirable to have a treatment system that will
require low maintenance, will enhance the land use after closure of
the landfill, and will remove all nitrogen rather than just ammonia
nitrogen to prevent nutrient enrichment of the receiving water.
Constructed wetlands may provide all of these advantages. This
project will provide an opportunity to evaluate the effectiveness of
constructed wetlands for treatment of the leachate as well as for
additional treatment of the effluent from the currently used aerobic
treatment system.
Products from this project would be:
• understanding of the limitations of constructed wetlands for
Nitrogen removal in coastal North Carolina
• full-scale treatment recommendation for New Hanover County
• recommendations for application of constructed wetlands for
Nitrogen removal
• low cost leachate treatment which may be utilized by others
The need to use constructed wetlands for treating landfill leachate for
improving water quality is only a portion of what is intended by New
Hanover County's Department of Environmental Management. The
department's goal is to utilize the landfill area for the development of a
"wilderness park" that would make use of constructed and natural
wetlands on the current site. During the course of this planning and
development period, a need to organize and document the growing amount
of information being generated becomes increasingly apparent. In the
course of the last two to three years, greater demands have been placed on
this department to provide and present information and details to interest
groups in education, industry, and other communities. This has intensified
3

due to recent changes in requirements in the nation with respect to how
solid waste is handled and treated (Subtitle D). It becomes increasingly
important to be capable of presenting detailed information about the
operation in a professional manner to benefit those working with
community planning or educational interests. This also stimulates the
development of continued relationships with New Hanover County at
professional and educational levels or as a community involvement project.
This site has proven to be an area of high interest as noted recently from
the department's involvement with NC State University and Sea Grant.
The past six months has been spent working with UNC-Wilmington in
developing background information for our current and future process
planning. Therefore, it is the intention of this department to develop an
intern program with UNC Wilmington under the biological/environmental
sciences program. Other interests from UNC-Wilmington include using
this site for classroom studies, field trips, etc. as they relate to the current
process and future planning concerning constructed wetlands. This could
also be extended to public school science classes or as a community project
involving volunteers with citizens in our community taking part in the
planning and development.
Closing Statement
New Hanover County has met many challenges since the opening of its
lined landfill in late 1981. As the first secure landfill in North Carolina
and in much of the Southeast, we serve as a model for others.
New Hanover County continues to move in a positive way to exceed
environmental requirements. This is evident by its facilities for the
treatment of leachate and the disposal of solid waste. New Hanover
County would be proud to be among the innovators that use wetlands for
water treatment; to be able to provide research facilities to further
understand the full potential of wetlands in an on -site treatment system;
and to be able to offer guidance and instruction in the educational
opportunities that are stimulated from this very essential project.
4

Design of a Constructed Wetland
System for Leachate Treatm ant
at the New Hanover County Landfill,
North Carolina

0
Design of a Constructed Wetland System for
Leachate Treatment at the New Hanover County
Landfill, North Carolina
Prepared for
New Hanover County
Department of Environmental Management
Wilmington, North Carolina
Prepared by:
Post, Buckley, Schuh & Jernigan, Inc.
4201 North View Dr., Suite 302 1560 Orange Ave., Suite 700
Bowie, MD 20716 Winter Park, FL 32789
Draft Report
March 1993

r
Design of a Constructed Wetland System for
Leachate Treatment at the New Hanover County
Landfill, North Carolina
Table of Contents
Section
Title
1
Introduction
1.1 Background -
1.2 Objectives
2
Design Parameters
2.1 Design Criteria
2.2 Experimental Design
3
Construction Design
3.1 Location and Layout
3.2 Earthwork and Liner System
3.3 Piping and Flow -Control Structures
3.4 Bed Materials
3.5 Wetland Plant Community
3.6 Organic Carbon Additions
3.7 Water Quality Sampling
4
Cost of Construction
5
References
Appendices
A
Project Background and Design Parameters
B
Manufacturer's Information
1
2-1
2-1
2-2
3-1
3-1
3-1
3-4
3-13
3-14
3-19
3-21
A-1
B-1

b
POST, BUCKLEY, SCHUH & JERNIGAN, INC.
Section I
Introduction
1.1 BACKGROUND
The New Hanover County Department of Environmental Management has contracted Post,
Buckley, Schuh and Jernigan, inc. (PBS&.J) to prepare construction plans for a wetland
treatment system to serve as a pilot study for treating leachate generated at the New Hanover
County Secure Landfill. The design of the wetland treatment system is a'cooperative effort
between New Hanover County; the North Carolina State University Departments of Civil
Engineering, Biological and Agricultural Engineering, and Forestry; UNC Sea Grant
College; the State of North Carolina, Department of Environment, Health and Natural
Resources (DEHNR), Division of Coastal Management (DCM); Mr. Mike Neslon; and
PBS&J.
A detailed description of the background for this project has been prepared (Liehr and
coworkers 1993) and is provided in Appendix A for reference. In summary, the New
Hanover County Secure Landfill, which was the first double -lined landfill equipped with
leachate collection in the United States, receives a mixed waste stream consisting of
municipal waste, construction and demolition debris, and ash residue from the County's 450
ton per day waste -to -energy incinerator. Leachate is collected from two closed and two
active landfill cells and pretreated in a 2.5 acre, 4 million gallon, lined lagoon. Pretreated
leachate is pumped to a 50,000 gallon per day extended aeration treatment plant for final
treatment before being filtered to remove solids and discharged to the Northeast Cape Fear
River. The effluent is discharged in accordance with the requirements of the National
Pollutant Discharge Elimination System (NPDES) permit issued to the County by the
1-1

F".
NCDEHNR Division of Environmental Management. The County has investigated the use
of constructed wetlands as a possible low cost and low maintenance alternative to the
extended aeration treatment plant for the long-term treatment of landfill leachate and is
instituting this pilot study to test the feasibility and effectiveness of a constructed wetland
system.
.1.2 OBJECTIVES
New Hanover County is interested in securing a long-term, low maintenance method for
treating its landfill leachate that is both economically and environmentally feasible and
beneficial to the public. With this goal in mind, the objectives of this pilot project are as
follows:
• Determine if leachate quality can be improved using constructed wetlands
• Determine if a constructed wetland system is a viable low cost and low maintenance
alternative to an extended aeration plant for treating landfill leachate
• Determine the optimum design and operation parameters for a large-scale constructed
wetland system to treat leachate
I
Other related objectives include:
• Use the wetland system as a tool for public education and scientific research on the
potential uses and benefits of constructed wetlands for water quality improvement in
coastal North Carolina
• Incorporate large-scale treatment wetlands into the wilderness park post -closure plan
for the landfill
1-2

POST, BUCKLEY, SCHUH & JERNIGAN, INC.
Section 2
Design Parameters
2.1 DESIGN CRITERIA
The design criteria for the wetland treatment system were prepared by Liehr and coworkers
(1993 see Appendix B) with modifications made during discussions held at the February 24,
1994 project kick-off meeting. The critical criteria used to prepare the construction design
of the New Hanover Wetland treatment system are as follows:
Average Areal Cell Dimensions (w z 1) ................. 3 m z 12 m (10 ft. z 39 ft.)
Average Water Depth:
Surface Flow Wetland S (FW) Cells (water only) ....... 30 cm (1 ft.)
Subsurface Flow Wetland (SSFW) Cells (gravel & water) .. 60 cm (2 ft.)
Storage Volume:
SFW Cells:
Water and plants .......................... 11.3 m' (3,212 gal.)
Water only ................ 8 m3 (2,274 gal.)
SSFW Cells:
Water and gravel .......................... 22m3 (6,252 gal.)
Water only .............................. 8 m3 (2,274 gal.)
Design Inflow Rate ............................ 0.57 m'/cell-day (137 gal/cell-day)
Hydraulic Loading Rate ........................... 1.5 cm/ha-day (0.24 in/acre-day)
Estimated Nitrogen Loading Rate ..................... 31 Kg N/ha-day (27.6 lb N/ac-day)
2-1

Residence or Detention Time ........................ 14 days
Flow Regime:
SFW Cells .............................. Continuous or draw-down/fill
SSFW Cells ............................. Continuous
Cell Bed Materials
SFWCells .............................. Sand
SSFW Cells ............................. V gravel or V crushed brick
Plant Community Matrix ........................... Mixed herbaceous marsh
2.2 EXPEPJAIENTAL DESIGN
Liehr and coworkers (1993) and Liehr (1994) have identified three hypotheses that they wish
to test during the performance monitoring of the pilot project and various experimental
design parameters that they would manipulate to test these hypotheses (see documents in
Appendix A). In as much as these hypotheses and the experimental design affect the
construction design of the wetland treatment system they are described below.
The three hypotheses that would be tested during the monitoring period are:
(1) Free water surface and subsurface flow constructed wetlands can provide effective
removal of nitrogen all year in coastal North Carolina
(2) Oxygen needed for nitrification will limit nitrogen removal in these systems most of
the year.
(3) Inexpensive, locally available material can be used as the support media
In order to test these hypotheses, the researchers wished to incorporate certain features in
jthe design to allow for the experimental manipulation of the treatment cells. Three design

issues regarding nitrogen removal by the wetland system were presented by Professor Liehr
and Mr. House and discussed during the February 24 project kick-off meeting. Each of
these design issues is discussed below.
(1) Originally Liehr and coworkers (1993) proposed to operate each cell independently.
Upon further consideration it was proposed (Liehr 1994) that the cells be designed
with the flexibility of either operating the cells independently or operating a SFW cell
in series with a SSFW cell. It is postulated that higher nitrification rates may be
obtained in the SFW cells and higher denitrification rates may be obtained in the
SSFW cells. By operating SFW and SSFW cells in series, nitrogen removal by
nitrification - denitrification could be enhanced. This concept has been incorporated
into the piping and flow control aspects of the construction design. .
(2) Because both nitrifying and denitrifying bacteria require a source of organic carbon
to fuel their metabolism, concern was expressed that nitrogen removal by these
bacteria would be limited by a lack of available organic carbon, especially during the
first year of operation. This issue has been addressed in the construction design in
two ways:
• Supplemental additions of organic carbon can be added to the sand substrate
of the SFW cells and to the gravel bed of the SSFW cells. Additions to the
SSFW cells will be via a perforated PVC pipe installed in the bed.
• Several of the plant species that will be used to establish the marsh
communities in the treatment cells will be fleshy species that have rapid
decomposition rates, thus providing the microbial communities with a ready
source of organic carbon.
(3) It is postulated that natural wetlands that undergo periodic flooding and draw -down
may be more effective in removing excess nitrogen from water than permanently
2-3

inundated wetlands. The basis for this argument is that periodic aeration of wetland
soils enhances nitrification, and overall nitrogen removal. The construction design
incorporates a bottom drain value for- all of the wetland cells than can be manually
operated to completely drain the cell. While all cells are so equipped for
maintenance purposes, it is understood that only the SFW cells would be operated in
a draw -down and fill flow regime.
2-4

POST, BUCKLEY, SCHUH & JERNIGAN, INC.
Section 3
Construction Design
3.1 LOCATION AND LAYOUT
The wetland treatment system will be located just south of the southwest quarter of landfill
cell 1 at the New Hanover County Secure Landfill (Figure 1). A relatively flat, grassy area
lying between cell 1 and the access road to the leachate treatment plant was selected for
siting the five wetland treatment cells (Figure 2). As shown in Figure 2, the treatment cells
will be arranged in two stages, with the first stage consisting of two surface flow wetland
cells sharing a common internal berm and the second stage consisting of three subsurface
flow wetland cells sharing, in common, two internal berms. The piping and flow design for
the system will allow leachate to be discharged directly to each cell, independently of the
other cells, or for flow to be routed from the surface flow wetland cells to subsurface flow
wetland cells, thus operating the two types of wetland cells in series.
3.2 EARTHWORK AND LINER SYSTEM
The wetland cells are designed to allow for gravity flow throughout the treatment system
once the leachate enters the influent feed tanks. To accomplish this, the cells will be
excavated below the existing site grade. The elevation of the downstream subsurface flow
wetland cells will be lower than the upstream surface flow wetland cells.
Each wetland cell will be cut and filled to acquire the appropriate grades. Berms around
each cell will be formed at a slope of 3 horizontal to 1 vertical. A liner system will then be
placed over the bottom and sides (berms) of the cells.
3-1

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POST, BUCKLEY, SCHUH & JERNIGAN. INC.
WETLAND TREATMENT CELL LAYOUT FIGURE 2
REPRO PRODUCTS. INC. 713 314359

An estimate of the earthwork required to form the cells was prepared by PBS&J. The total
volume of cut and fill estimated is 215 cubic yards (cy) and 179 cy, respectively.
The wetland treatment cells will be lined in accordance with the State of North Carolina
Solid Waste Management Regulations Leachate Storage Requirements (T 15A:
13B.1680(E)(2)) which state: "At a minimum, surface impoundments shall be designed with
a liner system equivalent to the liner system for the landfill unit generating the liquid. " The
liner system that will be used for the wetland treatment cells is similar to that designed for
landfill cell 4A (the most recently designed landfill cell) and thus will meet or exceed the
liner systems for the landfill cells generating the leachate. The liner system will consist of
the following components:
• a 60 mil. high density polyethylene (HDPE) primary liner, underlain by:
• a geonet leak detection laver, underlain by:
• a 60 mil HDPE secondary liner, underlain by:
• a claymax geosynthetic clay liner (i.e., a bentonite impregnated geotextile).
The primary liner will be overlain by an 8 ounce non -woven geotextile layer to protect the
primary liner from punctures during installation of bed materials (i.e., sand, gravel and
crushed brick layers) and from plant roots.
3.3 PIPING AND FLOW -CONTROL STRUCTURES
As configured, the wetland treatment system will allow for the treatment of raw leachate
from the existing lagoons in parallel with the treatment of treated leachate from the existing
treatment plant. Figure 3 presents the piping plan for the five (5) wetland cells.
3-4

For treating raw leachate, a 250 gallon influent feed tank (Figure 4) will be located upstream
of Surface Flow Wetland (SFW) No. 2. The County is currently pumping leachate from the
lagoon to the treatment plant. It is proposed that a 1/2-inch pipe be connected to the existing
pumping system to transfer raw leachate from the lagoon to the influent feed tank. For
further treatment of leachate from the treatment plant, effluent (treated leachate) from the
plant will be pumped to the wetland system. A second 250 gallon influent feed tank for
treated leachate will be located upstream of SFW No. 1. Refer to Appendix B for
information on the tank.
As discussed in Section 2, the feed rate into a wetland cell is approximately 6 ml/s (0.1
gallons per minute) or 137 gallons per day. Each tank is designed to maintain a constant
volume of leachate within the tank. A 2-inch overflow outlet is provided approximately 6
inches from the top of the tank. Excess leachate pumped into the tank will overflow into the
outlet which is connected to a drainline. Overflow from both influent feed tanks will be
returned by gravity to the lagoon.
As shown in Figure 4 leachate is discharged from the feed tank through a 2 inch pipe header
system. Valves are provided to allow the operator to direct leachate to the SFW cell, the
Subsurface Flow Wetland (SSFW) cell, or to the drainline back to the lagoon. If the SSFW
is to be operated in series with SFW cell, the valve to the SSFW is in the closed position.
If the operation is parallel, the valve to the SSFW is open.
Leachate is discharged into each of the cells in the same manner. A small flow measuring
device is provided to control the dosage rate onto the cell and is located approximately one
foot above the water level (see Figure 5). Called a "dipper", leachate flows into 1.5 gallon
storage tray. Refer to Appendix B for information on the dipper. The dipper is based on the
pivot and counterweight principle. When the storage tray is filled, the tray tips forward to
discharge the leachate into the wetland. The counterweight returns the storage tray into the
filling position. The leachate will be discharged perpendicular to the flow direction of the
cell. This will allow the leachate to become thoroughly mixed prior to treatment.
3-6

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Effluent from each SFW cell leaves the cell through an effluent outfall pipe (Figure 6). The
outfall pipe consists of a vertical 6" diameter PVC pipe with 1/2-inch holes located every
3 inches. Treated leachate enters the pipe and discharges from the cell beneath the berm.
The effluent outfall pipe is also equipped with a submerged ball valve. The cell can be
drained by opening this valve.
The water level in each SFW cell is controlled by the effluent piping system outside the cell.
As shown on Figure 6, a reducing tee is located downstream of the first ball valve. Under
normal operating conditions, the second ball valve downstream of the reducing tee is closed,
forcing the effluent up through a 1 1/2-inch pipe header. It is the height of the 1 1/2-inch
header that controls the water level in the wetland cell. The header is equipped with two
sliding sleeves (Figure 7) which allows the height of the header to be raised or lowered.
Therefore, the water level in the cell can be raised or lowered. To adjust the height of the
header, the bolts at each sleeve must be loosened. The header can then be raised or
lowered, and then the bolts are tightened. A sample port is also provided on the header for
easy collection of treated leachate samples from the SFW.
Depending on the mode of operation, the effluent from the SFW cells can be directed to the
downstream SSFW cells, ,or returned to the lagoon via the drain line. For wetlands
treatment in series, effluent from SFW No. 1 (treatment plant leachate) flows to SSFW No.
1. Further treatment of effluent from SFW No. 2 can be directed to either SSFW No. 2
(gravel media) or to SSFW No. 3 (brick media). A series of buried valves allows the
operator to select the point of discharge of effluent from SFW No. 2.
Leachate is introduced to the SSFW cells the same way leachate was added to the SFW cells.
The method for removing leachate from the SSFW cells differs from the effluent outfall pipe
described for the SFW cells. An effluent collection pipe is located along the bottom of the
cell liner and covered by gravel media (Figure 8). Four 1/2-inch diameter holes are drilled
6-inches apart along each end of the collection pipe. The effluent enters the collection pipe
and exits beneath the berm. Similar to the effluent piping system for the SFW cells, the
3-9

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SUBSURFACE FLOW
WETLAND OUTFALL
FIGURE 8

IINFLUENT FEED TANKS
SEE DETAIL, FIGURE 4
WETLAND INFLUENT STRUCTURE
SEE DETAILS, FIGURE S
(TYPICAL 5 PLACES)
— — — — — — — — — of s--------,
SFW #2
—J
TOP OF BERM
'
-- ;km
SFW 01
,
(TREATED)
,
— — — — — — — —
— TOP OF BERM-------�
SURFACE FLOW WETLAND OUTFALL
SEE DETAIL. FIGURE Ca
(TYPICAL 2 PLACES)
ORGANIC MATTER FEED SYSTEM
SEE DETAIL, FIGURE 10
(TYPICAL 3 PLACES)
1400
00
SUBSURFACE FLOW WETLAND OUTFALL
SEE DETAIL, FIGURE 8
(TYPICAL 3 PLACES)
LEACHATE)
TO LAGOON
FROM LEACHATE
TREATMENT PLANT
NOT TO SCALE
PasT,
., WC.
r"
WETLAND TREATMENT CELL & PIPING PLAN FIGURE 3

water level in the gravel media is controlled by piping header downstream of the cell, which
can be raised or lowered. All effluent from the SSFW cells is returned to the leachate
lagoon. Under normal operations, the second buried valve is closed, which directs the flow
through the water level control header. To drain the SSFW cell, the second valve is opened,
allowing the cell to drain directly back to the lagoon.
To minimize the cost of construction, most of the piping can be constructed of Schedule 40
PVC pipe. PBS&3 recommends that the 1/2-inch pipe from the raw leachate pump, and the
treatment plant pump be Schedule 80 PVC. Most valves are designed to be PVC ball valves
with true -union connections for easier maintenance. All buried valves are to be provided
with 2-inch square operating nuts and valve boxes for easy access.
3.4 BED MATERIALS
Bed materials or substrates will be installed in the wetland treatment cells to support the
wetland plant and microbial communities. Bed materials will be installed on top of a non-
woven geotextile overlying the liner system for each cell. The following bed materials will
be used in the treatment cells:
• A 12 inch (30 cm) laver of clean sand in each of the two surface flow wetland cells
(SFW #1 and SFW #2);
• A 24 inch (60 cm) layer of one -inch gravel in two of the subsurface flow wetland
cells (SSFW #1 and SSFW #2); and
• A 24 inch (60 cm) layer of one inch crushed brick in one of the subsurface flow
wetland cells (SSFW #3).
The sand substrate for the surface flow wetland cells will likely be excavated from the
3-13

Mlandfill site. The USDA Soil Conservation Service Soil Survey of New Hanover County
(Weaver 1977) identifies the majority of the landfill site as being comprised of Kureb sand,
an excessively drained, rapidly permeable soil. Smaller areas on the site consist of Leon
sand and Rimini sand, which are poorly drained and excessively drained soils, respectively.
It would be preferable to use topsoil (i.e., the top 12 24 inches of soil) for the sand
substrate if such a source is readily available on -site. Topsoil should contain a better balance
of plant nutrients to support wetland plant growth than sand excavated from greater depths.
The sand substrate may be supplemented with a source of organic carbon prior to its
installation in the beds (see Section 3.6). Approximately 12 cubic yards of soil will be used
T' for bed materials in each of the two surface flow cells.
Two substrates are proposed to be used in the subsurface flow wetland cells: gravel and
crushed brick (Liehr and coworkers 1993). Both of these substrates are specified as one -inch
sized material in order to provide similar flow characteristics and leachate volumes, and thus
similar detention times, within the three subsurface flow cells. The use of crushed brick was
proposed for two reasons: (1) culled brick is a locally available waste product that could be
put to beneficial use rather than disposing it in the landfill, and (2) there is some evidence
that the brick may aid in the removal of phosphorus from the leachate. Approximately 24
cubic yards of gravel or brick will be used for bed materials in each of the three subsurface
flow cells.
3.5 WETLAND PLANT COMMUNITY
Based on a review of previous studies, Liehr and coworkers (1993) originally proposed that
the following plant species be used in the wetland treatment system:
• Broad leaf cattail (Typha latifolia) for the surface flow cells,
• A mixture of soft stem bulrush (Scirpus validus) and soft rush (Junus effitsus) for the
subsurface flow cells.
During the February 24, 1994 project kick-off meeting, the attendees discussed the issue of

the composition of the wetland plant community to be used in the wetland treatment cells and
the following guidelines were agreed upon:
(1) The same wetland plant community should be used for all cells since this would
provide a better basis for comparison of cell performance.
(2) A diverse assemblage of wetland plant species should be used rather than a single
species (monoculture), since this may provide the treatment system with greater
overall ecological diversity and thus, possibly, a greater number of
biological/biochemical pathways for pollutant removal and transformation.
(3) The plant community should include fleshy plant species, such as pickerel weed
(Pontederia cordata) and arrowhead (Sagittaria latifolia), that will readily
decompose, thus providing a carbon source for the microbial community (especially
nitrifying and denitrifying bacteria).
Given the guidelines listed above, the following plant species will be used to make up the
wetland plant community for the treatment cells:
• Sweetflag (Acorus calamus)
• Soft rush (Juncus effusus)
• Arrow arum (Peltandra virginia)
• Pickerel weed (Pontederia cordata)
• Lizard's tail (Saururus cernuus)
• Arrowhead (Sagittaria latifolia)
• Softstem bulrush (Scirpus validus)
• Burreed (Sparganium americanum)
According to Thurnhorst (1993) all of the above species can tolerate regular to permanent
inundation up to 1 foot of water depth, except sweetflag which can withstand regular to
permanent inundation up to 0.5 feet. Based on PBS&Fs experience, softstem bulrush,
3-15

pickerel weed and arrowhead are often found in the deeper portions of natural wetlands
whereas the other species listed above usually occur at shallower depths. Species such as
sweetflag, pickerel weed, arrow arum, lizard's tail and arrowhead were selected because
these non persistent species should decompose rapidly, thus providing a ready source of
organic carbon for the microbial community. Soft rush, softstem bulrush and burreed should
persist during the winter season, providing permanent, above -ground physical structure to
the wetland community.
IThe planting plan for the wetland treatment cells is shown in Figure 9. The same planting
plan is used for both the SFW cells and the SSFW cells so that the cells will be comparable
in their biological/biochemical pollutant removal and transformation processes. The plan
specifies planting each species in repeating units or pods along the length of each wetland
treatment, cell. Softstem bulrush, pickerel weed and arrowhead are planted in the central
portion of the wetland cells, since these species should grow better in the deeper central
portion of the SFW cells. The. size of these central pods would be approximately 6.5 ft. x
6.5 ft. (2 m x 2 m) in the SFW cells and approximately 7.5 ft. x 6.5 ft. (2.3 in x 2.0 m) in
the SSFW cells. Sweetflag, soft rush, burreed, arrow arum and lizard's tail would be
planted in smaller pods along the margins of each cell, since these species should grow better
along the shallower side slopes of the SFW cells. The size of these smaller pods would vary
from approximately 3.25 ft. x 4.25 ft. (1.0 in x 1.3 m) for the SFW cells to 4.0 ft. x 4.25
ft. (1.25 m x 1.3 m) for the SSFW cells. The initial 1 meter length at the influent end of
each cell will not be planted to allow for an open water zone for mixing the influent
leachate.
Quantities of plant materials required for the wetland treatment system were estimated based
on the pod dimension specified in the planting plan and the growth characteristics of each
individual plant species. Plant sizes and planting densities were selected to provide good
coverage (i.e., 50 - 85%) within one year of plant installation. The quantities and
specifications for wetland plant materials are listed in Table 1. It is estimated that
approximately 1,900 plants will be needed to stock the wetland treatment cells.
3-16

Ac Je Sa Pv
Pc
SI
Ac I Je I Sa
Sv
0
Ac I Je I Sa I Pv I Ac I Je I Sa
Sc
SI
Sc
Ac — Acorus calamus
,-'Je — Juncus effusus
Pv — Peltandra virginica
Pc — Pontederia cordata
SI — Sagittaria latifolia
Sc — Sanaus cernuus
,/Sv — Scirpus validus
Sa — Sparganium americanum
NTS
POST. BUCKLEY, SCHUN E. JERNIGAN, INC.
WETLAND PLANTING PLAN FIGURE 9
IODI1C1S, INC. 70 314359

Wetland _CellStratum_
Surface Flow ~herb
(2 cells)
Subsurface Flow I herb
(3 cells)
TABLE 1. WETLAND PLANTING SPECIFICATIONS
Name
Common Name
Plant Size
_Scientific
Scirpus validus
Softstem bulrush
peat pot
Pontederia cordata
Pickerel weed
bare root
Sa ittaria latifolia
Arrowhead
bare root
_ Juncus effusus
Soft rush
Beat pot
Acorus calamus
Sweetflag
bare root
Peltan_dr_a vir inica
Arrow arum
bare root
Sarurus cernuus
Lizard's tail
bare root
parganium americanum
Burreed
bare root
Total Number of Plants for Surface Flow Cells
Scir us validus
Softstem bulrush
peat pot
Pontederia cordata
Pickerel weed
bare root
Sagittaria latifolia
Arrowhead
bare root
Juncus effusus
Soft rush
peat pot
Acorus calamus
Sweetflag
bare root
Peltandra vir inica
Arrow arum
'bare root
Sarurus cernuus
Lizard's tail
bare root
parganium americanum
Burreed
bare root
Total Number of Plants for Subsurface Flow Cells
Total Number of Plants for Pilot Wetland Treatment System
DensityArea/Species
o./s . ft.
(sq. ft.
Number of
Plants
0.25
169
42
0.44
169
74
0.44
169
74
0.44
110
48
1.00
110
110
1.00
110
110
1.00
110
110
1.00
110
110
679
0.25
293
73
0.44
293
129
0.44
293
129
0.44
204
90
1.00
204
204
1.00
204
204
1.00
204
204
1.00
204
204
1237
1916,

All of the species listed above can be obtain commercially from nurseries specializing in the
propagation of wetland plants. The following nurseries propagate wetland plants and are
possible sources for the plants specified for the wetland treatment system:
Van Hoose's Nursery, Inc. Central Florida Native Flora
1581 Hosier Road Box 1045
Suffolk, VA 23434
[phone] San Antonio, FL 33576
[phone]
Environmental Concern, Inc.
210 West Chew Avenue Pinelands Nursery
P.O. Box P 323 Island Road
St. Michaels, MD 21663 Columbus, NJ 08022
[phone] [phone]
3.6 ORGANIC CARBON ADDITION
It may be desirable to add an external source of organic carbon to the treatment cells -to
promote higher rates of nitrification and denitrification, especially during the first year of
operation and testing of the pilot project. Professor Liehr and Mr. House have investigated
the possible use of an organic waste material consisting of dead, washed bacterial cells as
a supplemental, organic carbon source. The organic waste under consideration would be
obtained from the Takata Chemical Products Plant in New Hanover County.
In discussions with Professor Liehr and Mr. House, it was decided that organic carbon
additions could be made directly to the sand bedding in the SFW cells, but that an alternative
feed system would be required for the SSFW cells. Based on an idea proposed by Mr.
House and Professor Liehr, an organic carbon feed system was designed that consists of
solid PVC feed and drain lines leading to and from a perforated 6 inch PVC pipe. The
perforated pvc pipe will be installed within the gravel bed, 12 inches from the bottom of the
bed. near the influent end of each SSFW cell (Figures 3 and 10). A slurry of the organic
Imaterial could then be introduced to each SSFW cell though the solid PVC feed pipe,
3-19

No CAP
P
C
NpUt
NOT TO SCALE
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ORGANIC CARBON FEED SYSTEM
Tpp O
BERM
• I FIGURE 10

allowing organic carbon to be slowly released to the bed concurrent with leachate flow
through the bed.
3.7 WATER QUALITY SAMPLING
In order to collect treated leachate samples fronl
So,,
middle and bottom depths within -the
gravel bed of the SSFW cells, a water quality sampling device was devised for in situ sample
collection (Figure 11). The device consists of a vertically supported 3 inch PVC pipe
installed within the gravel bed. The PVC pipe contains three sample ports at depths of 4
inches (10 cm), 12 inches (30 cm) and 20 inches (50 cm) below the surface of the gravel
bed. Each sample port consists of 1/4 inch diameter polyethylene tubing inserted through
a 1/4 inch hole in the PVC pipe at the appropriate depth and glued in place with silicone
caulk. From the sample port, each polyethylene tube runs out of the top opening of the PVC
pipe and over to the nearest berm, where samples can be collected from the desired depth
using a hand vacuum pump and vacuum flask -assembly. Four water quality sampling
devices will be installed in each SSFW cell, such that duplicate samples can be collected
from locations approximately 1/3 and 2/3 of the distance downstream of the influent mixing
zone of each SSFW cell.
3-21

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eSuR PpRTP�pF \
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o
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SAMPLING MANIFOLD
SC" . 11

POST, BUCKLEY, SCHUH & JERNIGAN, INC.
Section 4
Cost of Construction
A probable cost of construction was estimated by PBS&J for the constructed wetland
treatment system. The estimate includes the following items.
0 Earthwork
• Liner System installation
• Piping, Valves, and Flow Control
• Wetland System and Plants, and
• Miscellaneous Items.
The probable cost of construction is presented in Table 2.
4-1

TABLE 2. PROBABLE COST OF CONSTRUCTION
EARTHWORK
- Cut
$ 650
- Fill
$ 500
Subtotal'
$ 1,150
LINER SYSTEM
- Geosynthetic Clay Liner
$ 5,600
- 60 mil HDPE Liner
$ 7,750
- Geonet
$ 2,600
- Geotextile
$ 650
Subtotal
$16,600
PIPING AND FLOW CONTROL
- Yard piping and Valves
$22,400
- Influent Tanks (250 gal) and Stands
$ 2,600
- Inflow Measuring Devices (United Dippers)
$ 325
Subtotal
$25,325
MISCELLANEOUS ITEMS
- Influent Piers
$ 3,600
- Sampling Ports
$ 400
- Organic Feed Systems
$ 1,200
WETLAND SYSTEM
- Sand (24 cy)
No cost(*)
- Gravel (48 cy)
$ 850
- Brick (24 cy)
No cost(**)
- Plants (installed)
$ 2,375
TOTAL
$51,500
Available on -site material
** Locally available
4-2

POST, BUCKLEY, SCHUH & JERNIGAN, INC.
Section 5
References
Liehr, S. 1994. Memorandum to B. Doll and A.R. Rubin on Meeting with New Hanover
County and consultants on design of test plots. Dated February 22, 1994. 2 pp.
Liehr, S.K., B. Doll, R.A. Rubin and H. House, 1993. Constructed Wetlands for Treatment
of High Nitrogen Waste Waters: Pilot Study at New Hanover County Landfill. A
proposal to the UNC Sea Grant College Program. 29 pp.
Thunhorst, G.A., 1993. Wetland Planting Guide for the Northeastern United States, Plants
for Wetland Creation, Restoration and Enhancement. Environmental Concern Inc., St.
Michaels, MD. 179 pp.
Weaver, A. 1977. Soil Survey of New Hanover County, North Carolina. USDA Soil
Conservation Service, Washington, D.C. 69 pp. + maps.
5-1

POST, BUCKLEY, SCHUH & JERNIGAN, INC.
Appendix A
Project Background and Design Parameters

TO: Barbara Doll, A.Robert Rubin
FROM: Sarah Liehr
DATE: February 22, 1994
RE: meeting with New Hanover County and consultants on design of test plots
Hal and I met today to organize our thoughts on what things we would like to be considered in the
actual design of the test plots. If you have comments, additions, etc., let me know today or
tomorrow (or Thurs. if you are going to be at the meeting!).
The main thing we want is to design the maximum amount of flexibility into these plots. We
intend to start with our original plan: five plots including one FWS and one SSF receiving treated
effluent (high nitrate in summer, ammonia in winter) and one FWS and two SSF receiving leachate
from the holding lagoon (high ammonia all the time). However, if it becomes obvious that these
systems won't provide good treatment we would like to be able to change the configuration or
operation.
These are the design flexibility features we thought of:
1) We have discussed the possibility (probably good possibility) that the SSF plots will not get
adequate nitrification. One thing we could do about this is to put a FWS and a SSF in series,
assuming that we will get nitrification in the FWS and denitrification in the SSF. One
possible arrangement of plots that would allow changing the flow from the. five parallel setup
is the following:
A
J

This arrangement would allow us to run the five plots in parallel, run FWS to SSF, or compare
the FWS,SSF series to SSF alone (for the plots receiving lagoon leachate). This setup would
eliminate the option of running two plots in series in the order SSF to FWS, but we could not
think of a reason why we would want to do that anyway.
2) Another way we might be able to improve nitrification in the SSF plots is to use intermittant
flow (periodic drawdown). We want to be sure we have enough control over water levels that
we can do this, and we want to install the proper valves, etc. that would allow us to install a
mechanism to time this automatically at a later date if we choose to.
3) Another way to improve nitrification if it is oxygen limited (and prevent clogging problems,
etc.) is to distribute the inflow along the length of the plot. We did not decide on a mechanism
for doing this, but we want to discuss it at this stage to make sure we have the option of
installing the appropriate distribution devices later.
4) It may turn out that carbon source is limiting denitrification/nitrogen removal. We also want
to plan for a system of adding supplemental carbon source. We are pursuing possibilities for
testing Takata waste as a carbon source; we want to plan for that possibility now.
The following are other issues we thought of to mention at this time:
- measurement of flow rates in influent and effluent
- water level control
- two -valve exit drain so that we can take water from either top or bottom
- how the lining will be secured around the edges, how it will be covered, etc.
- size of brick/substrate; whether we could do this in association with others on campus who
are currently studying use of brick in wetlands (this doesn't have to be resolved right now).

A Proposal to the
UNC Sea Grant College Program
For Research Entitled
Constructed Wetlands for Treatment of High Nitrogen Waste Waters:
Pilot Study at New Hanover County Landfill
Covering the Period from January 1, 1994 to December 31. 1996
Requested Support for three years in the Amount of S 181,692
Matching Support from North Carolina State University in the Amount of $9,939
A/ 27
Sarah K. Liehr
Assistant Professor
Civil Engineering
Barbara Do
UNC Sea Grant
AINM5110a�
AeV44 - -
Robert A. Rubin
Ex. Associate Professor
Bio. and Agric. Engineering
2 ri�L
Halford House
Forestry Depart rent
W.L. Klarman
Vice Chancellor for Research
North Carolina State University
Submitted. April 15, 1993

�1�
CONSTRUCTED WETLANDS FOR TREATMENT OF HIGH NITROGEN WASTE
WATERS: PILOT STUDY AT NEW HANOVER COUNTY LANDFILL
Sarah K. Liehr (PI), Assistant Professor, Department of Civil Engineering, North Carolina State
University
Barbara Doll (Co -PI), UNC Sea Grant College Program
1 Robert A. Rubin (Co -PI), Extension Associate Professor, Department of Biological and
Agricultural Engineering, North Carolina State University
Halford House (Co -PI), Research Associate, Department of Forestry, North Carolina State
University
I INTRODUCTION
Eutrophication of coastal waters is a problem in North Carolina, as it is in much of the country
(McCullough, 1984). In many of North Carolina's Atlantic -bound river basins as well as other
coastal and inland waters, nitrogen addition is the cause of algal blooms and subsequent water
quality degradation. Nitrogen sources include wastewater effluents from municipal treatment
facilities and septic systems, agricultural and urban runoff, animal wastes from feedlots and
1 confinement operations, landfill leachates, and various food processing effluents. Many of these
1 sources are difficult to control because of lack of collection systems, remote locations, or
expense.
Constructed wetland systems offer many advantages as a low cost, low maintenance method of
providing treatment (Butler et al., 1990; Gearheart, 1992). Wetland systems have been
demonstrated to be effective for removing BOD, suspended solids, nitrogen and sometimes
phosphorus, metals and toxic organics (Reed et al., 1988; Reed and Brown, 1992a; Soukup et al.,
1992; Wolverton and Bounds, 1988; Wolverton and Wolverton, 1992). These systems consist of
lined basins containing a solid substrate, such as soil or stone, and some type of emergent aquatic
vegetation, frequently Typha (cattail), Phragmites (common reed), or Scirpus (bulrush).
Wastewater that is applied to the system is treated by natural physical, chemical and biological
processes. The key removal mechanism for nitrogen in these systems appears to be
microbiological (Reed et al, 1988; Watson et al., 1988), through the processes of nitrification
(microbial conversion of ammonia to nitrate) and denitrification (microbial conversion of nitrate
to N2 ), although sedimentation/filtration, ammonia volatization and plant uptake may also
contribute to removal (Rogers et al., 1991; Schiemp et al., 1990). The role of the emergent
vegetation in nitrogen removal is to provide attachment sites for microbial growth, transport
oxygen to the subsurface in the root zone method, and to provide some amount of direct uptake.

I 2
There are two basic types of constructed wetlands used for treatment of wastewaters. FWS and
SSF. The free water surface system (FWS) consists of a shallow basin containing sand or soil as
the solid substrate. The surface is flooded with water to a depth of 6 to 24 inches. Typha
appears to be well suited to this type of system and provides extensive surface area for
attachment of microorganisms (Reed et al., 1988; EPA, 1988). Oxygen is provided by diffusion
through the water surface; algae do not provide significant oxygen to the water because they are
effectively shaded by the emergent vegetation.
j . The subsurface flow system (SSF) uses a more hydraulically conductive substrate, such as coarse
■ sand or stone. Water applied to the system flows below the surface of the substrate, allowing
filtration, sorption, precipitation, and microbial processes to remove contaminants.
Microorganisms attach to the substrate surfaces; oxygen is provided primarily through transport
by the plants from the air to the root zones (Reddy et al., 1989). Phragmires and Scirpus appear
to be most effective for this root zone method of oxygen transfer because of deep penetration of
roots and rhizomes into the subsurface (Conley et al., 1991; Cooper et al., 1989; Wood, 1990).
Such reed bed treatment systems are already fairly common in Europe.
Landfill leachate is a good example of a wastewater that wetlands present an attractive treatment
option (Birkbeck et al., 1990; Dornbush, 1989; Keely et aL, 1992; Moshiri and Miller, 1991;
Sanford et al., 1990; Staubitz et al., 1989; Surface et al., 1991). Most leachate is currently
transported by truck to local municipal wastewater treatment plants. Hauling of leachate is
expensive, potentially dangerous, and many wastewater facilities require pretreatment. On -site
treatment by conventional processes usually involves high construction and operation costs,
which continue for years after landfill closure. Alternative on -site treatment methods for
leachate are becoming more important as more landfills collect and require treatment for their
leachate as a result of legislative requirements.
New Hanover County lies in the southern region of the North Carolina coastal plain at the mouth
of the Cape Fear River. Bording the Atlantic Ocean, New Hanover County has a permanent
population of approximately 120,000 with about 60,000 located in the county's largest
municipality of Wilmington. In addition, New Hanover County receives about 1.3 million
visitors per year. Average annual rainfall for the county is 136 cm (53.5 in); the average daily
high temperature for the summer months is about- 310C (870F); the average daily low
temperature for the winter months is 40C (390F).
New Hanover County began operation of the first double -lined landfill with leachate collection
in North Carolina in 1981. The county also operates a 450 ton per day (TPD) waste -to -energy
incineration facility adjacent to the landfill. Ash from the incinerator is disposed of in the
landfill.
Leachate is currently collected from four separate landfill cells including 1, 2, 3A and 3B. Cells
1 and 2 are completed and capped, cell 3A is scheduled for closure in Spring 1993, and cell 3B is
actively used primarily for disposal of incinerator ash and construction debris. The leachate
collected from the landfill is pumped to a 2.5 acre, 4 million gallon capacity lagoon for
pretreatment. From the lagoon the leachate is fed to a 50,000 gallon per day (gpd) extended
aeration plant for further treatment. Filter cloth is used to remove solids from the aeration plant

3
effluent. which is then discharged to the Cape Fear River, in accordance with the requirements of
the National Pollutant Discharge Elimination System (NPDES) as mandated by the State of
North Carolina, Department of Environment, Health and Natural Resources (DEHNR), Division
of Environmental Management (DEM).
In order to meet NPDES requirements, the effluent discharged to the Cape Fear River must have
30 milligrams per liter (mg/L) or less 5-day Biological Oxygen Demand (BODD, 30 mg/L or
less of Total Suspended Solids (TSS), a pH between 6-9, must pass toxicity test as specified by
DEM and must not cause the turbidity of the Cape Fear River to exceed 50 NTU. The facility is
also requested to monitor concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper
(Cu), iron (Fe), nickel (Ni), zinc (Zn), aluminum (Al), mercury (Hg), manganese (Mn), total
nitrogen (TN) and total phosphorus (IP). In May, 1989, a toxicity reopener was placed on the
landfill's NPDES permit which modified toxicity testing from 48 hour acute toxicity of Daphnia
to 24 hour acute toxicity of fathead minnow. Prior to this new toxicity requirement the facility
had no difficulty in meeting NPDES requirements.
Leachate influent to the extended aeration plant from the lagoon is characterized by fairly low
BOD5, TSS and metals and fairly high ammonia nitrogen and TN. BOD5-concentrations are
generally less than 50 mg/L, but on occasion have gone as high as 260 mg/L. Most of the
influent nitrogen is in the form of ammonia-N. Concentrations of ammonia-N up to 100 mg/L
are common in the summer. Winter concentrations are somewhat higher, occasionally up to 200
mg/L. Effluent concentrations of BODS are generally less than 20 mg/L, with occasional higher
levels. In the summer, most of the nitrogen in the effluent is in the form of nitrate, with
ammonia-N concentrations generally in the range of 1 to 5 mg/L. During periods of cold
weather, November or December to March, nitrifying bacteria slow down in the extended
aeration plant, resulting in low to no removal of ammonia. In all instances, high ammonia
concentrations of 8 parts per million (ppm) or greater have corresponded to failure of the toxicity
test (Mike Nelson, personal comm.). However, the plant has consistently performed well during
periods of warn weather. Additional testing has shown no evidence of toxicity from organics or
metals in the effluent. Iron concentrations are frequently less than 0.5 mg/L, with occasionally
higher Ievels, up to 6.0 mg/L. Other metals have consistently been present in very low
concentrations.
There are many potential benefits to New Hanover County of a wetland treatment system. The
immediate concern is with meeting their toxicity standard by effectively removing ammonia
during cold weather. Nitrification requires temperatures greater than 60C to be effective
(Shammas, 1986; Hammer and Knight, 1992). Wetland systems may be able to provide warmer
temperatures during cold periods by providing insulation with organic debris which prevents
rapid heat Ioss stored in the ground and generated by microbial activity. This may be enough to
enhance nitrification in the relatively mild coastal North Carolina climate. The County also
wants to replace their extended aeration plant with a technology that requires less maintenance,
such as a wetland system. This option is especially attractive for post -closure treatment of
leachate, and would fit in well with current plans to develop a "wilderness park" at the site after
closure of the landfill. A wetland system may also be better able to handle shock loadings of
pollutants and may be effective at total nitrogen removal. Standards for total nitrogen are
anticipated to be included in their discharge permit in the future. The County is very responsive
to public opinion and is interested in developing a wetland treatment technology that would gain

4
public acceptance. They are also interested in the potential for using such a system as an
educational tool that will help train environmental professonals and inform the general public
about the potential for wetland treatment systems for applications in water quality improvement
in coastal North Carolina.
Constructed wetlands have many features that are attractive for use in water quality improvement
in coastal areas. Although such systems have been shown to be effective in various applications,
design criteria vary widely and are not. based on solid theory of removal mechanisms within
these systems (Bavor et al, 1989; EPA, 1988; Reed and Brown, 1992a; Steiner et al., 1991;
Watson et al., 1988). This project will use five pilot scale constructed wetland plots to test the
effectiveness for treatment of this high ammonia landfill leachate. The focus will be on ammonia
and total nitrogen removal. A mass balance approach will be used to identify how much nitrogen
is actually removed and by what mechanisms. Other water quality parameters that will be
studied include suspended solids, biochemical and chemical oxygen demand (BOD/COD),
organic carbon, phosphorus, metals, alkalinity, and pH. These parameters will not be considered
as extensively as nitrogen.
The following hypotheses will be tested during this research:
1) Free water surface and subsurface flow constructed wetlands can provide effective
removal of nitrogen all year in coastal North Carolina.
2) Oxygen needed for nitrification will limit nitrogen removal in these systems most of
the year.
3) Inexpensive, locally available material can be used as the support media.
OBJECTIVES
ORMI 1 tell'IM-10-1.
The purpose of this project is to evaluate the ability of constructed wetlands to treat a high
nitrogen wastewater in a southeastern North Carolina coastal environment by treating leachate
from the New Hanover County Landfill. Treatment ability will be determined in pilot scale
wetland plots with different design strategies.
Compare effectiveness of subsurface flow wetlands (SSF) and free water surface
wetlands (FWS) under seasonal conditions.
Deten-nine effect of loading rate and detention time on treatment ability of constructed
wetlands.
Determine the ability of constructed wetlands to treat both raw landfill leachate directly
from the collection lagoon and aerobically pretreated leachate.

5
• Investigate economics and effectiveness of alternative support media.
• Observe evidence of long-term problems, including clogging of SSF and excessive
sedimentation in FWS systems.
• Construct and plant five test plots
• Establish good plant growth
• Begin sampling
• Complete one full year of data collection
• Complete preliminary analysis to look for operational diff culties and potential
problems
• Make minor adjustments to operational stragegy as necessary
Remaining, Work
• Collect second full year of data after plants have become more fully established in the
wetlands
• Analyze data and compare operational strategies in the different plots
• Make recommendations
METHODOLOGY
Five pilot -scale wetland plots will be constructed at the New Hanover County Landfill. Leachate
collected from the landfill has been found to contain high levels of ammonia, causing potential

6
• problems with ammonia toxicity. Currently, leachate collected from the landfill is aerobically
treated to achieve nitrification, converting ammonia to nitrate. This treatment system is very
effective in warm weather but not always in cold weather. This project will provide the
opportunity to evaluate the effectiveness of constructed wetlands for treatment of the leachate as
well as for additional treatment of the effluent from the currently used aerobic treatment system.
The project objectives will be addressed by the following strategies:
Free Water Surface vs. Subsurface Flow Wetlands
Parallel plots will be used to evaluate the relative effectiveness of subsurface flow wetlands
(SSF) and free water surface wetlands (FWS). Each of these types of systems has advantages
and disadvantages. FWS wetlands may get better oxygen transfer, do not have clogging
problems, and provide better opportunity for ammonia volatization. SSF wetlands should get
better temperature control in the winter and will not require mosquito control (Reed et al.,1988).
This research will include an analysis of the advantages and disadvantages of these two basic
types of wetlands. Factors that will be considered in the analysis will include: cost of
construction; treatment efficiency, especially under cold weather conditions; evidence of long-
term problems and aesthetics for post -closure use of landfill site.
N-Ioading and Detention Time
the effect of loading rate and detention time will be determined by strategic placement of sample
locations within each bed, allowing analysis of several detention times and mass loading rates
within each bed.. Flow rate will be kept constant Data collected will allow a critical evaluation
of design assumptions.
Three of the wetland plots will receive leachate directly from the collection lagoon. The other
two cells will receive effluent from the aerated treatment system currently in place. This
arrangement will allow evaluation of use of constructed wetlands for complete leachate treatment
and for polishing the effluent of the treatment system by providing additional nitrification for
ammonia removal and denitrification for nitrate removal.
Substrate
The effectiveness and economics of alternative support media for subsurface flow will be
evaluated. The current recommendation for support media is to use a one -inch gravel to
minimize problems with clogging (Cooper et al., 1989; Sanford et al, 1990; Steiner and Freeman
1988; Steiner et al., 1991). Probable alternative substrate is culled bricks, compared to locally
available gravel or marl. Use of a locally available waste product, such as culled bricks, could be
economically favorable as well as ease the waste disposal problem of landfilling unwanted brick.
Free surface wetlands will use on -site fill soil, primarily a slightly silty, clayey sand.
Long -Term Problems
Evidence of long-term problems will be examined. Such evidence includes clogging of
subsurface flow wetland by organic matter which may cause change in water level, resulting in
ponding. Another long-term problem that will be examined is sedimentation of free surface
wetland. Accumulation of organics will be measured in both types of systems.

' 7
Pilot Plot Set-un
Pilot plots will be built and sampled according to the following strategy in order to test the stated
hypotheses.
Pilot Plot Cells
Five 12 m by 3 m pilot plot cells will be built with resulting length to width ratios of 4:1 (Figure
1), which corresponds to current recommendations (Crites, 1992; Hammer and Knight, 1992).
Previous recommendations suggested larger length to width ratios for the purpose of minimizing
short circuiting in the beds (Steiner and Freeman, 1989). However, this strategy is more costly
and can result in overioading the front end of the systems.
Three of the cells will receive untreated leachate from the holding lagoon. One of these cells will
be a FWS wetland and two will be SSF wetlands. One of the SSF wetlands will use a standard
gravel support media and the other will use a locally available waste product, such as culled
brick, as an alternative. These cells will receive high ammonia influent all year, and will test the
ability and limitations of such systems to remove ammonia.
Two of the cells will receive treated effluent from the extended aeration plant. This effluent
contains high levels of nitrate most of the year when effective nitrification takes place in the
1 treatment plant. One of these cells will be a FWS wetland and the other will be a SSF wetland
using the alternative support media. This arrangement will allow analysis of the effectiveness of
these two types of wetlands for denitrification during most of the year, and will demonstrate
1 effectiveness of ammonia removal during the cold season when nitrification is not'effective in
1 the treatment plant.
Plants
A mixture of Scirpus validus and Juncus eff=is will be used in the SSF systems. Scirpus has
been shown to be effective in the root zone method of treatment in SSF wetland systems and is a
locally abundant plant (Conley et al., 1991; Watson et al, 1989; Wood, 1990). Juncus is also
locally common, and is better at over -wintering than many other wetland plants.
Typha latifolia will be used in the FWS systems. This species has been shown to be effective in
constructed FWS wetlands (Birkbeck et al., 1990; Reed et al., 1988).
Water Depth
In the SSF systems, the support media will be 60 cm deep and the water level will be maintained
just below the surface of the support media. This depth was selected based on the depth of root
penetration of the plant species, which will be important for effective oxygen transfer by the root
zone method. Scirpus has the deepest root penetration of the commonly used wetland plants, up
to 76 cm (Cooper et al, 1989; Gersberg et al., 1986).
In the FWS systems, the soil substrate will be 30 cm deep, and the water depth will be
maintained between 20 - 60 cm, averaging 30 cm. Shallow water depths will provide better
oxygen transfer through surface diffusion and is expected to allow better nitrification (Crites,
1992). The same conditions will possibly allow greater ammonia volatization.

Figure 1. Schematic diagram of wetland pilot plots.
treated leachate
* Sample locations
BED
A:
Free Water
Surface
BED
B:
Subsurface
Flow/ Brick Media
BED
C:
Free Water
Surface
BED
D:
Subsurface
Flow/ Brick Media
BED
E:
Subsurface
Flow/ Gravel Media
raw leachate

g
Detention Time and Loading Rates
Flow rates through the systems will be determined based on detention time. Detention time for
each system will be 14 days. Previous studies have shown that 14 days detention time is
adequate for treatment in most FWS systems; shorter detention times have been recommended
for SSF systems (Conley et al, 1991; EPA, 1988; Reed and Brown, 1992b; Watson et al.,1989).
Alternate detention times will be analyzed by sampling at intermediate locations along the test
plots.
Two types of loading rates are important for proper operation of wetland systems. One type is
hydraulic loading rate (HLR), which is volume per area per time. The other is mass loading rate
(MLR), which is mass of N per area per time.
The SSF systems have total volumes of 22 m3. Assuming a porosity of 0.35 for the gravel or
alternative media, the total volume available for flow is about 8 m3. To achieve an overall
detention time of 14 day, a flow rate of about 0.57 m3/day is required. This flow rate would
result in a HLR of 1.5 cm/day and a MLR of 31 kg N/ha-day (based on a maximum influent
concentration of 200 mg NIL). The HLR is within currently recommended guidelines ( Hammer
and Knight, 1992; Platter and Netter, 1992, Watson et al., 1988; 1989); the MLR is higher than
some recommendations (Hammer and Knight, 1992; Swindell and Jackson, 1990; WPCF, 1990)
and lower than others (Watson et al., 1989). Some design guidelines are given in terms of
oxygen demand, assuming oxygen transfer into the system will be the limiting factor. The MLR
of N corresponds to an oxygen demand loading of 142 kg OZ/ha-day. This is within some
published values for maximum oxygen transfer by the root zone method (Armstrong et al, 1990;
EPA, 1988; Reed et al, 1988). Tracer tests will be performed to determine actual flow rates
required to achieve the desired detention time in the plots after plants become established
The FWS systems with 30 cm water depth contain a total volume of 11.3 m3. Assuming a
porosity of 0.7 with fully established plants, the total volume available for flow is about 8 m3,
which is the same as the SSF systems. Therefore, estimates of required flow rate, HLR, and
MLR are the same for both types of systems. Again, the actual flow rate required will be
determined in the system after plants have become established Loading rates for the full 14 day
detention time are again similar to some of the recommended guidelines (EPA, 1988; Reed et al.,
1988; WPCF, 1990). FWS wetlands may not be as limited by oxygen transfer as are SSF
wetlands (Hammer and Knight, 1992)
Sampling Locations
Samples will be taken monthly for measurement of water quality parameters from the influent
and the effluent of each test plot. In addition, samples will be taken from two locations within
the plots (Figure 1). The first of these will be at a distance one-third the length of the plots, at a
detention time of approximately 5 days. Samples will be taken from two places along a transect
at this distance. At each of these two places, separate samples will be taken from the top, middle
and bottom of the water column. The second location will be at a distance of two-thirds the
length of the plots, at a detention time of approximately 10 days. Samples will be collected in
the same way as at the first location. Therefore 14 samples will be collected from each plot.
Collection -of separate samples at the top, middle, and bottom of the water columns will allow.
analysis of the effectiveness of removal at different depths. providing information that will be
useful in detemining optimum depths for such systems.

E
. Parameters To Be Measured
The inflow and outflow rates to each system will be measured continuously. Rainfall data will
also be collected at the landfill site. This information will allow calculation of a water balance,
assuming evapotranspiration is the only other loss of water from the systems.
Temperature ('I'), dissolved oxygen (DO), and pH will be measured weekly at all the places that
water samples are normally collected. Alkalinity, total dissolved solids (TDS), total suspended
solids (TSS), volatile suspended solids (VSS), chemical oxygen demand (COD), total
phosphorus (TP), and dissolved phosphorus (diss.P) will be analyzed monthly. BOD will be
measured quarterly to develop a conversion from COD to BOD. Metals (As, Cr, Cd, Cu, Ni, Zn,
Fe, Mn, Al, Hg) will be measured quarterly or as determined to be necessary. Phosphorus, BOD
rand metals will be measured only in the influent and effluent.
The concentrations of .important nitrogen species will be measured monthly. These species
include nitratelnitrite (NO3-/NO2'), total ammonia nitrogen (TAN), total kjeldahl nitrogen
(TKN), and dissolved kjeldahl nitrogen (diss.TKN).. Analysis of dissolved as well as total
kjeldahl nitrogen will allow determination of the contribution of sedimentation to removal of
nitrogen in these systems. Nitrate will be present in dissolved form.
Plant samples will be collected quarterly. These samples will be analyzed for dry weight, N,
NO3-, P, K, Ca, Mg, Cu, Ni, Pb, Zn and Cd. This analysis will allow estimates of the amount of
nitrogen that has been removed by direct uptake by the plants. It will also give us an indication
of metal uptake by the plants. Metal concentrations have typically been low in this leachate, and
problems with metal accumulation are not expected. Samples will be taken from four locations
within each plot, with two replicate samples taken per location.
The accumulation of organics in the sediments will be measured semi-annually. Sediment
samples will be taken and analyzed for organic matter and for nitrogen. This measurement is
important as an indicator of accumulation of material that may cause long-term problems for
operation of these systems. Clogging of SSF systems is of particular concern, but FWS wetlands
may also become filled in with organic debris.
Toxicity will be measured quarterly by New Hanover County according to their required
protocol. Samples will be taken from the influent and effluent of each system. Scans of organics
by GCMS will be done twice during the study to check for potential toxicity problems by priority
pollutants.
Data Analysis
Influent and effluent rates are monitored continuously, and rainfall will be measured at the site.
These measurements will allow us to calculate water loss by evapotranspiration and thereby the
total water balance.
Concentrations of nitrogen species will be used with flow data to determine mass flows of
nitrogen species. Ammonia volatization rates will be calculated from TAN concentrations, pH
and established transport relationships. Uptake of nitrogen by plant material will be estimated
from plant tissue and total biomass analyses. Sedimentation of nitrogen will not be measured

l 10
- directly, but estimates of the importance of this removal mechanism will be made based on data
for total vs. dissolved nitrogen in the water and from sediment analyses. The rates of microbial
activity, including nitrification and denitrification, will also not be measured directly, but will be
determined by rate of changes in TAN, nitrate, and total nitrogen in the system after accounting
for the other removal mechanisms. By determining rates of different removal mechanisms and
not just determining whether nitrogen is removed, better recommendations and design criteria
>i will be developed for these types of systems.
Data from both FWS and SSF systems will be analyzed in. this way and compared for
effectiveness of various removal mechanisms. Different detention times and loading rates will
be evaluated by comparing data from several locations within each test plot. Data will be
analyzed on a seasonal basis to determine if these systems will be effective for nitrogen or
ammonia removal in cold weather. Additional insight into effectiveness of the various removal
mechanisms will be obtained by comparing results from plots that receive raw leachate,
containing mostly ammonia nitrogen, to those that receive aerobically treated leachate,
containing mostly nitrate nitrogen.
Data for other water quality parameters will also be analyzed for the purpose of gaining insight
into the processes occurring in these systems. This insight will also be useful in developing
meaningful design criteria. Accumulation of organic material in the support media will give an
indication of potential for long-term problems in both types of systems. A complete analysis of
long-term problems will not be possible as a result of this project, but some insight into potential
problems may be gained.
EXPECTED RESULTS
The following is a list of the major results expected from the proposed research:
• Develop an understanding of the limitations of constructed wetlands for N removal in
coastal North Carolina.
• Make full-scale treatment recommendation for New Hanover County Landfill.
• Develop recommendations for application of constructed wetlands for N removal for
other high N wastewaters in coastal North Carolina.
This research will also be beneficial in association with other research projects. Graduate
students in the Civil Engineering Department are currently working on related research,
including a study of mechanisms of nitrogen removal in greenhouse wetland plots and
development of a model of nitrogen removal in wetlands based on established mathematical
descriptions of fundamental removal mechanisms. This research would interrelate to both of
those projects. This research would also be enhanced by UNC-Wilmington students work in
conjunction with New Hanover County to enumerate nitrifying bacteria. Development of this
field experiment would provide opportunities for other graduate students to study related topics
on established pilot scale test plots.

11
Another result of this project will be the development of an educational tool,for New Hanover
County. The County plays an important role in public education, including school children as
well as adults. They plan to use this research in developing their mission to educate the public in
potential alternatives for waste treatment that preserve the quality of the environment.
RELEVANCE TO NORTH CAROLINA
Control of nitrogen effluents into coastal waters is an important problem in North Carolina.
Eutrophication has resulted in algal blooms, populations of predatory algae, and nitrate toxicity
to sensitive vegetation beds (Burkholder, 1991).
This will also be useful to North Carolina given the mandate for communities to collect and treat
their landfill leachate. Collection and treatment of landfill leachate will be a major expense for
many communities.
Wetland systems show promise as a technology for controlling nitrogen inputs to coastal waters
from a variety of sources. Landfill leachate is only one problem source of nitrogen that might be
able to take advantage of these systems. Other sources include. municipal wastewater,
agricultural and urban runoff, feedlot wastes, animal confinement wastes, and food -related
industrial wastewater. Some of these types of waste waters will require pretreatment, especially
for removal of high BOD, prior to application to a wetland system. Even with pretreatment,
wetland systems may be an economical and effective method for removal of some pollutants,
including nitrogen.
Using wetland treatment systems for non -toxic waste waters has the additional benefit of creating
wildlife habitat (James and Bogaert, 1989; Feierabend, 1989; Wentz, 1987). The public is very
concerned about loss of wildlife habitat (Hoban and Clifford, 1992) and would likely be
receptive to the concept of using constructed wetlands to enhance the environment.
North Carolina currently has no policy guidelines for the use of constructed wetlands for water
treatment in the state. This work could be an important factor in defining a policy regarding this
treatment method.
RELEVANCE TO OTHER WORK
Constructed wetlands are receiving much attention as an alternative treatment method for many
types of waste waters. Constructed wetlands appear to have potential for removal of a number of
pollutants, including BOD, TSS, N, P, metals and toxic organics. Many states have not yet
developed well defined policies for use of constructed wetlands because necessary information is
lacking. There is still considerable disagreement about the effectiveness of these systems.
Design criteria are generally based on case -by -case input-output observations.
The effectiveness of constructed wetlands for removal of ammonia nitrogen is particularly
controversial. Some researchers question whether enough oxygen will be transported to the
sediments to achieve nitrification in the root zone method (Brix and Schierup, 1990; Schierup et

12
al.. 1990). Others believe that the root zone method is effective in providing oxygen to the
sediments (Armstrong et al., 1990; Conley et al., 1991; Gersberg et al., 1989). There is evidence
that nitrification is the limiting step in nitrogen removal in many systems, with the supply of
oxygen usually_the limiting factor (Choate et al, 1990; Hsieh and Coultas. 1989; Watson et al.,
1988). Nitrification has been enhanced in several studies by providing aeration (Choate et al,
1991; Davies and Hart, 1990; Willadsen et al., 1990). Others have found that the limiting factor
in nitrogen removal is the organic carbon supply required for denitrification (Gersberg et al.,
1983, 1984).
Many studies of constructed wetlands have not determined removal mechanisms and thereby do
not offer insight into why some systems work well and others do not. This research will address
the issue of removal mechanisms, which should improve our understanding of rate limiting
factors, and will provide a basis for rational design criteria.

1 13
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t t- A 15
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