DURHAM COUNTY TRIANGLE WASTEWATER TREATMENT PLANT PERFORMANCE ANNUAL REPORT 2007 - 2008
Performance Annual Report – Triangle Wastewater Treatment Plant
GENERAL INFORMATION
To keep citizens informed and to maintain compliance with State requirements and the Clean Water Act of 1999 (House Bill 1160), Durham County has prepared this report summarizing the performance of the County-owned Triangle Wastewater Treatment Plant (TWWTP) and associated wastewater collection system. This report includes activities during the County’s fiscal year 20072008 (July 1, 2007 through June 30, 2008). This report contains a System Overview, a Performance Summary, and a Major Projects Overview. Facility / System Name: Triangle Wastewater Treatment Plant 5926 NC Highway 55 East Durham, North Carolina 27713
Operated by: United Water Hydro Management LLC 2554 Lewisville Clemmons Road Clemmons, North Carolina 27012 Responsible Entity: Durham County Contact: Mr. Joseph R. Pearce, P.E. Utility Division Manager Durham County Engineering Department 120 East Parrish Street Durham, North Carolina 27701 (919) 560-0735 Applicable Permits: Wastewater Treatment Plant – NC0026051 Collection System – WQCS00038 Stormwater – COCNCG110054 Reclaimed Water Utilization System – WQ0032821
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Performance Annual Report – Triangle Wastewater Treatment Plant
SYSTEM OVERVIEW
Description of Collection System and Treatment Process
The Durham County wastewater collection and treatment system serves a customer base of more than 9,700 residential, commercial, and industrial users, including the portion of Research Triangle Park located in Durham County. During the last year, the Triangle Wastewater Treatment Plant (TWWTP) treated an average of 4.49 million gallons per day (MGD) of wastewater. Included in this flow is wastewater collected from the Town of Cary under an agreement between Durham County and the Town of Cary to treat flow through 2010.
Collection System Wastewater Collection System
Page Road Pump Station with Generator
The collection system consists of gravity sewer lines, pump stations, and force-mains to convey wastewater to the treatment plant. Durham County owns and maintains approximately 108 miles of sewer with ten pumping stations. All pump stations are equipped with telemetry that provide immediate notification of alarm conditions. Nine of the ten stations have generators with automatic power transfer for emergency power during power outages. The station without the automatic power transfer generator is served by a portable generator, and can also be served by a portable diesel pump. Collection system operations include maintenance of the pump stations, easement maintenance, manhole inspections, sewer line cleaning, easement mowing, manhole inspections, and high priority line inspections. Pump station maintenance is completed both based upon periodic inspections and also based upon a Computerized Maintenance Management System (CMMS). Easement maintenance, primarily mowing, is completed at least once each year to ensure access to the collection system during all weather conditions. During the year, Durham County inspected over 2015 manholes and cleaned more than ten percent of the county-owned gravity sewer lines. To further minimize the risks of sewer blockages and spills, the County completed quarterly high priority line inspections.
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Performance Annual Report – Triangle Wastewater Treatment Plant
Treatment Process
A view of the oxidation ditch The 12 MGD biological nutrient removal (BNR) facility is specifically designed and operated to reduce oxygen demanding pollutants, suspended solids, pathogens, nitrogen and phosphorous from the wastewater prior to discharge into Northeast Creek, a tributary to Jordan Lake. As a secondary benefit, significant quantities of other pollutants are removed through the oxidation process and through sludge uptake. Industrial Pretreatment Program To ensure that the discharges to the wastewater treatment plant do not pass through the wastewater treatment plant; nor inhibit the biological processes; nor interfere with physical processes; nor contaminate the sludge so that it may not be beneficially reused; nor result in potentially hazardous operator conditions, an Industrial Pretreatment Program (IPP) is implemented at the Triangle Wastewater Treatment Plant. Twenty-one permitted industries are regularly inspected and monitored to ensure their discharges meet specific permit limits. Thirteen of these industries are Significant Industrial Users (SIUs). The IPP includes a Fats, Oil, and Grease (FOG) control program to minimize the accumulation of grease in the sewer system. FOG can cause blockages and wastewater overflows within collection systems. The IPP monitors discharges from commonly recognized sources such as restaurants to minimize problems associated with FOG. The FOG program also teaches best practices for FOG management to restaurant staff. In addition to restaurants, residences can be sources of FOG discharges. Everyone can help minimize FOG issues in the sewer by not pouring grease down the drain. 3
Performance Annual Report – Triangle Wastewater Treatment Plant
ANNUAL PERFORMANCE SUMMARY
Summary of System Performance
The Triangle WWTP discharge was non-compliant for a single pollutant in all sampling events in the past year. An effluent mercury limit was exceeded in the last week of May, 2008. The operation of the Biological Nutrient Removal facilities that were put into service in 2005 has provided the County with significant reduction of nutrients discharged to Northeast Creek. Below is a graph depicting the reductions that have been achieved. The Total Nitrogen removed from 2005 to 2008 was increased by 52 percent and the Total Phosphorus removed was increased by 22 percent while Total Nitrogen and Total Phosphorus influent loadings processed at the facility increased an average of 32 percent.
Durham County Triangle Wastewater Treatment Facility Total Nitrogen (TN) and Total Phosphorus (TP) Removal
900,000 800,000 700,000 Pounds 600,000 500,000 400,000 300,000 200,000 100,000 FY 2005 FY 2006
Influent TN TN Discharged
FY 2007
Influent TP TP Discharged
FY 2008
The Triangle WWTP experienced no flow bypasses during the year and treated 1,638,850,000 gallons. There were two reportable spills in the collection system: On December 12, 2007 a spill occur at 4825 Creekstone Drive. The discharge occurred as a result of a blockage cause by grease. Approximately, 6,000 gallons of wastewater spilled into the Stirrup Iron Creek drainage area in the Neuse River Basin. The spill was stopped within two hours of the identification of discharge. NCDENR was notified and the sewer line was temporarily rerouted while the line was cleared. No detrimental environmental impacts were observed due to the spill. 4
Performance Annual Report – Triangle Wastewater Treatment Plant
On March 6, 2008, approximately 100,000 gallons of wastewater spilled into an unnamed tributary of Kitt Creek in the Cape Fear River Basin located at 4406 Hopson Road from the collection system for the Triangle Wastewater Treatment Plant. This spill resulted in a fish kill of approximately 50 fish, 1 inch or smaller in size. The discharge occurred as a result of a blockage caused by the collapse of a 21” sewer line. The spill was stopped within 50 minutes of the identification of the discharge. To prevent further discharge, the sewer line was temporarily rerouted while the line was repaired. The tributary was temporarily dammed and approximately 200,000 gallons was pumped into the sanitary sewer system. NCDENR was notified and the areas impacted by the spill was disinfected. Environmental impacts were identified, and minimized by the pumping of wastewater from the creek.
TRIANGLE WASTWATER TREATMENT PLANT OVERVIEW
Triangle Wastewater Treatment Plant Improvements
Durham County continues the process of upgrading the Triangle Wastewater Treatment Plant. The WWTP process comprised of the following: • • • • • • • • • Influent Pump Station – sized for 12 MGD average flow, and located above the 100-year flood elevation to avoid flooding. Fine Screens – removes large materials prior to the beginning of the treatment process. Grit Removal – removes small dense inorganic materials prior to the beginning of the treatment process. Five Stage Biological Nutrient Removal System – provides the ability to remove nitrogen and phosphorous during treatment. Chemical Polishing – sodium aluminate is used to remove additional phosphorus from water by chemical precipitation. Clarifiers – separates biomass from the treated water. Tertiary Filters – filtering to remove unsettled biomass. Ultraviolet Disinfection – disinfection process without harmful by products Reaeration – supplemental dissolved oxygen provided prior to discharge.
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Performance Annual Report – Triangle Wastewater Treatment Plant
Current Phase 3 Improvements Under Design
Phase 3 will provide for the dewatering of the sludge generated by the treatment processes. This project is in the design phase and will consist of new sludge holding facilities, dewatering facilities and truck loading facilities. The dewatered sludge cake will then be taken off-site for treatment to Class A standards. The Class A designation by the U.S. Environmental Protection Agency (EPA) indicates a highly treated product. The Phase 3 improvements are scheduled for construction in 2009 and 2010.
Water Reuse
The design of the reuse project is in progress, and it will result in the use of the treated water produced by the treatment plant being available for uses, such as irrigation and the operation of cooling towers. The project, proceeding as a joint effort with Wake County and the Town of Cary, is partially funded by an EPA grant. The benefits of this project include the reduction of nutrient loading to Jordan Lake and the conservation of potable water supplies due to the use of the treated water for uses that are currently supplied by the potable water system.
Final Effluent at TWWTP at the final weir at the discharge to Northeast Creek.
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Performance Annual Report – Triangle Wastewater Treatment Plant
Notification
The Performance Annual Report for the Durham County Triangle Wastewater Treatment Plant, July 1, 2007 through June 30, 2008, was forwarded to the North Carolina Department of Environment and Natural Resources. Public notice of the Performance Annual Report was advertised in the Durham Herald Sun newspaper and is available for review at the following locations: Durham County Web Site (http://www.co.durham.nc.us/departments/ceng/Utility_Division.html) Durham County Library, Main Branch, 300 North Roxboro Street, Durham Durham County Library, Parkwood Branch, 5122 Revere Road, Durham Durham County Administrative Complex, Clerk’s Office, 200 East Main Street, Durham
Certification I certify under penalty of law that this report is complete and accurate to the best of my knowledge. I further certify that this report has been made available to the users or customers of the named system and that those users have been notified of its availability.
July 31, 2008 _________________________________ Joseph R. Pearce, P.E. Utility Division Manager Durham County Engineering Department ________________ Date
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