NC0026051_Annual Performance_20230831

DURHAM
COUNTY
Triangle Wastewater
Treatment Plant
5926 NC Hwy. 55 E.
Durham, NC 27713
[phone]
Permits:
Wastewater
Treatment Plant:
NCO026051
Collection System:
WQCS00038
Stormwater :
N CG 110054
Reclaimed Water:
WQ0032821
Owned and Operated
by:
Durham County
Engineering
Environmental Services
Utilities Division
Contact:
Stephanie Brixey
Deputy Director
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:N •� } urham County Utilities Division
_ Dcontinues to reinvest in the
Publicly Owned Treatment
Works (POTW), both at the Triangle
Wastewater Treatment Plant (TWWTP)
and within the collection system. In
FY2023, the rehabilitation of one
process train was completed which
consisted of cleaning the inside of the
structure, seam replacement, flapper
valve replacements, weir replace-
ments, as well as replacing all
mechanical rotors with new stainless -
steel rotors, and gearbox replacements
that include variable frequency drives.
The project cost approximately $950,000.
Additional projects at the TWWTP Before
consisted of rehabilitation on one
of three centrifuges, installation of '
a new compactor, as well as the
complete replacement of drain and
flapper valves on all four clarifiers.
The collection system consists of
110 miles of sanitary sewer pipes
and 13 lift stations. Approximately
370 linear feet of pipe was rehabil-
itated by applying cured in place -
pipe lining (CIPP), several man-
holes were rehabilitated, and =~�•
pump control panels and panel
hoods were replaced at two lift
stations. See page 2 of this report
under Projects & Rehabilitation for
additional projects completed in
FY2023. 9
After IF
/

Collection System
urham County owns and maintains a
wastewater collection system which
includes 110 miles of gravity sewer, 11
miles of pressurized force mains, and
13 lift stations.
In the past 12 months Durham County had no
reportable sewer spills.
Durham County Utilities prides itself on providing
a high level of customer service. All commercial,
industrial, and residential customers' questions
and concerns are responded to in a timely man-
ner. If you have a question or concern regarding
the collection system, services, or any item cov-
ered in this report, please call [phone] or
send an e-mail to [e-mail].
Projects &
Rehabilitation
hroughout the last year, the County has
continued its efforts to rehabilitate
aging collection system infrastructure
and increase sanitary sewer capacity to
facilitate economic growth in our
service area. Along with several items
listed on the cover page, the following are
additional projects completed in FY2023:
=> Stirrup Iron Lift Station — Installed a new flow meter,
new grating, and an additional pump.
=> Rehabilitation on the wet well and pumps were
completed at five lift stations.
=> At TWWTP, nineteen pumps and mixers were
rehabilitated.
=> At TWWTP, grit chamber internal concrete was
rehabilitated.
=> At TWWTP, replaced the auger and chute guides on
the influent conveyor system.
=> At TWWTP, purchased and installed a new sodium
hypochlorite tank.
=> Upgraded the communication system from a remote
reclaimed monitoring station.
=> Preliminary Engineering Reports for Page Park
Apts. Lift Station, Slater Road Lift Station, and
TWWTP Phase IV Upgrade.
A Preliminary Engineering Report or PER, is a very useful document for:
- Assessing the condition of an existing Water, Wastewater, Stormwater
system;
Understanding any deficiencies within the utility;
Prioritizing infrastructure upgrades;
Evaluating alternatives for addressing system needs;
Developing a cost estimate for the selected improvement project;
Communicating required capital improvement needs to the residents
of a community and other stakeholders.
Biosolids System
TWWTP generates biological residuals
(approximately 6,700 wet tons per year), which are
dewatered by centrifuges. The dewatered cake
(approximately 1,969 dry tons per year) is transport-
ed to McGill Environmental Systems, where it under-
goes further biological treatment to produce a Class
A biosolid. These biosolids are beneficially used as
soil amendments in commercial landscaping and
agricultural activities.

Treatment System & Process
The Influent Pump Station (IPS) is used to pump raw wastewater
(sewage) to the treatment process to be biologically treated. The IPS is
sized for 12 million gallons per day average flow.
The Fine Screens are used to remove fine materials from the wastewater
such as grit, sand, egg shells, etc. All of the organic materials are washed
off and used in the biological treatment process.
The Five Stage Biological Nutrient System is where all biological treatment
TWWTP takes place, such as removing ammonia through nitrification and
BIOCHEMICAL OXYGEN DEMAND denitrification processes as well as the removal of phosphorus.
(BOD)
VIOLATIONS The Chemical Polishing process removes any phosphorus that is remaining
after the biological treatment process. Methanol is used in this polishing
July2022 process to add additional BOD to support the denitrification treatment
Exceeded weekly BOD limit
process.
August2022 The Clarifiers are where the biomass is separated from the treated
Exceeded monthly BOD limit wastewater and then is returned to the BNR for further treatment.
May2023 The Tertiary Filters are next in the clarification process which removes all
Exceeded weekly BOD Limit remaining unsettled biomass in the treatment process.
5.0 mg/1 Monthly Avg. Permit Limit
3.24 mg/I 0
BIOCHEMICAL OXYGEN DEMAND
30 mg/I Monthly Avg. Permit Limit
<2.5 mg/1
TOTAL SUSPENDED SOLIDS
111,207lbs. Annual Permit Load Limit
74,871 lbs.
41
TOTAL NITROGEN
200 cfu/100ml Monthly Avg. Permit Limit
3 cfu/100 ml
FECAL COLIFORM
1.0 mg/I Monthly Avg. Permit Limit
0.14 mg/1
AMMONIA -NITROGEN
8,432 lbs. Annual Permit Load Limit
7,973 lbs.
TOTALPHOSPHORUS
The Ultraviolet Disinfection
treatment process is used to
remove all disease causing
bacteria without creating
harmful by-products.
The Reaeration stage of the
treatment process adds
dissolved oxygen to the treated
wastewater to meet required
permit limits before it is
discharged to Northeast Creek.

Glove Recycling
Program
Durham County Utilities continues to partner
with RIGHTCYCLE* to reduce landfill waste
by recycling gloves and has diverted approxi-
mately 40 pounds of glove waste from the
landfill by collecting used gloves and sending
them to RIGHTCYCLE*. Used products are
sorted, processed into plastic pellets, and
raw materials which are molded into new con-
sumer products.
Durham County is committed to vigorously
pursuing sustainable practices in all opera-
tions and continue to make progress related
to our environmental stewardship goals.
=
Industrial
Pretreatment
Program
TWWTP implements an Industrial
Pretreatment Program (IPP) to control
pollutants which may cause pass through
or interfere with the treatment plant's
processes, which may contaminate
sewage sludge, or potentially be
hazardous to worker's health and safety.
Currently, there are seventy permitted
industries that are regularly inspected and
monitored to ensure their discharges meet
specific permit limits. Seventeen of these
industries are Significant Industrial Users
(SIUs). Biosafety Laboratories in our
service area have also been identified and
eleven are currently permitted. Several of
the Industrial Pretreatment Permit holders
are required to certify that their facility has
followed biosafety procedures consistent
with the fifth edition of the Biosafety in
Microbiological and Biomedical
Laboratories, US DHHS -PHS, -CDC and
-NIH for the deactivation of Biosafety Level
1, 2, 3 or 4 materials prior to discharge to
the sewer system.
M