NC0079057_AUTHORIZATION TO CONSTRUCT_19980622

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NPDES DOCYNENT SCANNING COVER SHEET
NPDES Permit: NC0079057
Manteo WWTP
Document Type: Permit Issuance
Wasteload Allocation
Authorization to Construct
(AtC)
Per odification
Speculative Limits
Complete File - Historical
Instream Assessment (67B)
Environmental Assessment (EA)
Permit
History
Document Date: June 22, 1998
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1 �
State of North Carolina
Department of Environment N15A
IT
and Natural Resources A4 •
Division of Water Quality
James B. Hunt, Jr., Governor ��
Wayne McDevitt, Secretary D E N R
A. Preston Howard, Jr., P.E., Director
June 22, 1998
Mr. John Luke, Jr.
Utilities Superintendent
Town of Manteo
Post Office Box 246
Manteo,North Carolina 27954
Subject: Permit No. NCO079057
Authorization to Construct
UV Disinfection/Weir Modification
Town of Manteo WWTP
Dare County
Dear Mr. Luke:
The Division received a letter of request for an Authorization to Construct on March 4, 1998 and
final plans and specifications for the subject project have been reviewed and found to be satisfactory.
Authorization is hereby granted for the construction and installation of an ultra-violet (UV) disinfection
unit and weir modification at the Town of Manteo, which discharges to Shallowbag Bay in the
Pasquotank River basin.
This Authorization to Construct is issued in accordance with Part III, Paragraph A of NPDES
Permit No. NCO079057 issued April 27, 1993 and shall be subject to revocation unless the wastewater
treatment facilities are constructed in accordance with the conditions and limitations specified in Permit
No. NC0079057.
Any sludge generated from this treatment facility must be disposed of in accordance with G.S.
143-215.1 and in a manner approved by the North Carolina Division of Water Quality.
In the event that the facility fails to perform satisfactorily, including the creation of nuisance
conditions, the Permittee shall take immediate corrective action, including those as may be required by
this Division, such as the construction of additional or replacement wastewater treatment or disposal
facilities.
The Washington Regional Office, telephone number(252) 946-6481, shall be notified at least
forty-eight (48) hours in advance of operation of the installed facilities so that an in-place inspection can
be made. Such notification to the regional supervisor shall be made during the normal office hours from
8:00 a.m. until 5:00 p.m. on Monday through Friday, excluding State Holidays.
P.O. Box 29535, Raleigh, North Carolina 27626-0535 Telephone [phone]FAX [phone]
An Equal Opportunity Affirmative Action Employer 50%recycled/10%post-consumer paper

Mr. Luke
June 22, 1998
NC0079057/ACA079057
Page 2
Upon completion of construction and prior to operation of this permitted facility, a certification
must be received from a professional engineer certifying that the permitted facility has been installed in
accordance with the NPDES Permit, this Authorization to Construct and the approved plans and
specifications. Mail the Certification to the NPDES Unit, P.O. Box 29535, Raleigh, NC 27626-0535.
The Permittee, for the life of the facility, shall maintain a copy of the approved plans and
specifications on file.
Failure to abide by the requirements contained in this Authorization to Construct may subject the
Permittee to an enforcement action by the Division of Water Quality in accordance with North Carolina
General Statute 143-215.6A to 143-215.6C.
The issuance of this Authorization to Construct does not preclude the Permittee from complying
with any and all statutes, rules, regulations, or ordinances which may be imposed by other government
agencies (local, state, and federal) which have jurisdiction.
One (1) set of approved plans and specifications is being forwarded to you. If you have any
questions or need additional information, please contact Paul Clark, telephone number(919) 733-5083
extension 580.
Sincere-
Wq-r.11�
f-11. Preston Howard, Jr., P.E.
cc: Central Files
Washington Regional Office, Water Quality
Technical Assistance and Certification Unit
y,FD6� P mt-��e/Enforcement=Unit
E. Leo Green, Green Engineering
303 North Goldsboro Street
Post Office Box 609
Wilson, NC 27893

J ACA079057 Summary
June11, 1998
On February 27, 1998, Leo Green (on behalf of the Town of Manteo) submitted an
Authorization to Construct for a proposed UV disinfection system and weir modification.
Manteo WWTP operates at 0.6 MGD, but is permitted to discharge 1.0 MGD into
Shallowbag Bay (SC) in the Pasquotank River Basin (030151).
WWTP consists of mechanical bar screen, grit chamber, multi-channel mechanical
aeration, two standard clarifier units, tertiary traveling bridge filters, chlorine gas
disinfection, dechlorination, post aeration, sludge digester, sludge holding tank, standby
power and permitted land application.
Facility has been in compliance and has passed its toxicity tests for the past year (last
failure was 2/97). TSS values have been consistently below 2.0 mg/l (well below 10.0
mg/l recommended for UV disinfection units).
After UV disinfection unit is installed, wastewater will bypass existing
chlormation/dechlorination unit, pass through UV disinfection unit and then proceed to
existing post aeration chamber before going to effluent pump station.
Green has installed UV disinfection for the Town of Zebulon (NC0079316) and that
system has had fecal coliform values well below permit limits.
The weir will be lowered because now that chlorine contact chamber will be bypassed
water level does not have to be as high in this chamber.
Review of the plans and specifications indicate that an Authorization to Construct can be
issued for the proposed UV disinfection unit and weir modification.
Page 1 of 1

;/ar,%v OF tiiA�vTED / L� 6e s'
ULTRAVIOLET RADIATION DISINFECTION CHECKLIST
(UV DISINFECTION)
Y N
1. Does the facility have sand filters prior to the UV unit?
2. Does the facility have tertiary treatment?
3. Does the facility achieve monthly average TSS values from 10 - 15 mg/I or
less? 7s5 < a r,_j/�(�/�96- v/se )
If not, the facility should be cautio ed about using UV and the facility should be
encouraged to acquire a'gaurantee' from the manufacturer stating that the Fecal coli limit
an be met at their TSS range.
4. Has a pilot study been performed at the facility?
If not, has data from similar facilities using UV been provided by the manufacturer?
5. Is the unit designed for peak flow? The unit must be designed for peak flow.
6. Is a cleaning method iitdicated/provided?
Do design requirements in specifications reflect appropriate permit limits '
and operating conditions for the treatment system?
7. Is a system drain provided so the chamber may be cleaned?
8. Does the operator have the ability to isolate modules? (i.e. by flow control)
9. Is duality of the UV banks provided?
10. Is there a redundant and separate power supply? Although standy power is required for
some new facilities, ME may wish to require this for UV units. This should be evaluated
on a case by case basis right now.
l l. Does the unit measure]amp output over time?
12. Does the unit have in-place intensity monitors?
14. Does the unit have ballast panel temperature indicators or specifiy optimum temp. ranges?
15. Does the unit have an alarm system?
16. Does the unit indicate which lamps are in use or are out of service?
17. Does the manufacturer provided spare ]am s, sleeves, etc.?
18. What is the % Transmissivity value?I h5 1
Questions 1 -3 may be investigated by the review engineer and do not have to be provided.
Question 4 should be provided by the consultant as separate documentation from the plans and specs.
Questions 5 - 18 may be found in the plans or specs of the UV unit.
Modules/Bank
No.of Banks
NOTE: This checklist will not provide you with a method to check the design and configuration of the UV unit,as
that is site specific and complex. However,the manufacturer should be able to provide that information and you
may check their calculations by reviewing the EPA Manual (p. 184). The design parameters provide a means to
calculate total wattage for a given fecal coliform limit. Based on that total wattage,the design engineer can calculate
the number of lamps needed per bank and the number of modules needed.
The EPA Manual (p. 159)recommends a range of transmissivity values for: �eb /o C/LLOO�rj 3�6�
Secondary treatment: 60-74%
Tertiary treatment: 67 -82%
Basic definitions:
Lamp -individual lamp that delivers UV radiation
Module- stainless steel device to hold lamps horizontally.
Bank-series of modules contained within the chamber area.

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ULTRAVIOLET RADIATION DISINFECTION INFORMATION
(UV DISINFECTION)
Ultraviolet disinfection is used as an alternative to chlorine disinfection due to the reduction
in risk factor(as opposed to gas chlorine handling), due to the elimination of chlorine by-
products with UV, and due to increased requirements of chlorine limits.
UV disinfection is more costly initially than chlorine and also has higher operation and
maintenance costs. These factors should be taken into account by facilities considering UV
disinfection.
UV lamps are activated by electron flow between electrodes through ionized mercury
vapor. They are very similar to fluorescent lamps,except fluorescent lamps are coated with
a phosphor compound which converts UV to visible light.
UV disinfection attacks the bond of nucleoproteins in the cell and either keeps the micro-
organism from replicating or kills it. UV does not alter the water chemistry since only
energy is involved. UV may cause an increase in the water temperature, but this should be
slight since exposure time is limited.
UV dosage is a function of UV intensity and exposure time measured in µW- s/cm2 (micro
Watts - seconds per square centimeter). Current designs are usually high intensity, low
exposure time(10-30 seconds). D= I * t [Dosage= Intensity * time]
To properly design a UV disinfection unit a pilot study must be performed or a pilot study
from similar wastewaters and flows should be provided. The design criteria specified in
the EPA Manual [ref. below] is based on actual data. UV is a direct function of UV
absorption (which varies with wastewater) and average intensity (which is dependent on
lamp selection and configuration). Closely spaced lamps have a high UV intensity. Also,
the longer the forward distance traveled during exposure, the better the efficiency of the
unit. Design configurations can vary.
The current consensus is that suspended solids should not exceed 20 mg/1 for reliable
operation. This is stated in the Chlorination Handbook and the EPA manual. Suspended
solids will cause a higher UV absorbance and lower kill. The TSS can act to 'mask'the
microorganisms.
At minimum the manufacturer must provide the facility with gauranteed capacity and range
of operation.
Dead zones and short circuiting should be avoided in the UV unit. Baffles may need to be
inserted into the unit.
Some method of cleaning the tubes should be provided. Cleaning may be done through a
mechanical wiper, ultrasonic device (usually used for a closed channel UV unit), high
pressure wash, and chemical cleaning. Chemical cleaning is especially useful in removing
scale buildup and fouling from hard water.
References:
Handbook of Chlorination and Alternative Disinfectants,Thud Edition,Geo.Clifford White,pp. 1208-
1236.
EPA Design Manual, Municipal Wastewater Disinfection,EPA/625/1-86/021,pp. 157- 245.
Wastewater Engineering,Third Edition,Metcalf&Eddy,pp. 195 -200.
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