Rocky River Regional Wastewater Treatment Plant

Concord, North Carolina

Rocky River Regional Wastewater Treatment Plant Capacity Expansion

The Rocky River Regional Wastewater Treatment Plant (RRRWWTP) is a two stage 26.5 MGD biological wastewater treatment facility that is owned and operated by the Water and Sewer Authority of Cabarrus County (WSACC). The facility serves a thriving area north of Charlotte, including the cities of Concord and Kannapolis, the towns of Harrisburg and Mt. Pleasant, and Cabarrus County. The staff performs all functions related to the facility including operations and maintenance, laboratory analysis, and industrial and groundwater monitoring. The recently upgraded plant uses a 95% pure-oxygen activated sludge biological process, and an upgraded disinfection system that uses sodium hypochlorite for disinfection, eliminating gaseous chlorine designated as extremely hazardous by EPA and OSHA.   An upgraded sludge processing system was completed in 1995. This system included high solids centrifuges for dewatering, high pressure pumps (originally developed for pumping concrete) for conveying dewatered sludge, and afterburner/wet electrostatic precipitator scrubbing for the incinerator stack gases.

  • High Biosolids Centrifuges – Dewatering units achieve continuous low-moisture biosolids fed to a multihearth incinerator that runs most efficiently under steady-state feed conditions.
  • Dewatering Biosolids Bunkers – Provides an inventory of dewatered biosolids that allows changes in furnace feed rates while maintaining constant centrifuge operation or constant feed rates and variable centrifuge operation. The bunkers are vented to the Odor Control Facility for odor control.
  • Piston-Type Biosolids Pumps – One of the first plants in the U.S. to install these to pump 30% biosolids. The pumps are equipped with pipeline lubrication system that reduces pumping energy by 50%.
  • Flue Gas Heat Exchanger – Preheats all incinerator combustion air, greatly reducing fuel needs for incineration. Only a few U.S. plants utilize this energy-saving technology.
  • Inlet Air Velocity Nozzles – Introduces air to the incinerator through nozzles to increase turbulence and promote more uniform and complete combustion.
  • Heat Recovery for Building Heat – Heat exchanger extracts heat from gas to warm plant buildings. This reduces electrical needs for heating.
  • Wet Electrostatic Precipitator (ESP) – Removes fine particulate from flue gas and allows greater reliability to meet air permit limits at lower operating cost that conventional methods.
  • Afterburner – Additional high-temperature combustion chamber burns total hydrocarbons and volatile organic compounds to meet new federal air regulations.
  • Grit Removal System – A new headworks / grit removal system was added in 2000.
  • Odor Control System – A new odor control system was added in 2002.

Innovative ash disposal methods have been approved by the Division of Environmental Management. In 1994, ash was beneficially used as daily landfill cover and in brick manufacturing. The ash brick project was the first in North Carolina using wastewater solids ash.

Muddy Creek Wastewater Treatment Plant

Cabarrus County, North Carolina

The Muddy Creek Wastewater Treatment Plant (MCWWTP) is permitted for 300,000 gallons per day.  The MCWWTP serves the Midland area of Cabarrus County, and is a package treatment plant which uses the following processes: 

  • Influent Pumping, Screening and Flow Equalization
  • Aeration Basins and Aerated Sludge Holding Tanks
  • Secondary Clarifiers
  • Filters and Ultraviolet (UV) Disinfection

Coddle Creek Reservoir/Lake Howell

Cabarrus County, North Carolina

Coddle Creek Reservoir/Lake Howell is a 1,300-acre reservoir impoundment that provides a raw water supply for the Coddle Creek Water Treatment Plant and the Kannapolis Water Treatment Plant. The impoundment dam is approximately 2,400 feet in length and consists of zoned earth fill. The principal spillway consists of three 75 feet wide by 5 feet high crest gates that allow the water elevation to be controlled between 645 feet and 650 feet. An auxiliary spillway and emergency spillway are also part of the dam. The drainage basin for Coddle Creek Reservoir/Lake Howell is approximately 47 square miles in parts of Cabarrus, Rowan and Iredell Counties. The total water impounded is approximately 5 billion gallons, which allows for a daily safe yield of approximately 28 million gallons.

Coddle Creek Reservoir/Lake Howell was constructed in 1992-1993 by Cabarrus County. Operation and maintenance is performed by WSACC.

Lake Concord

Concord, North Carolina

Lake Concord was built by the City of Concord in 1929 and still provides an emergency water supply source for the City of Concord. The 100 acre lake has been owned and operated by WSACC since 2003. The lake has a daily safe yield of 1.0 MGD.


The Laboratory at the RRRWWTP is state certified for the analysis of water and wastewater samples. The Laboratory performs approximately 2500 analyses per month for NPDES compliance monitoring for all WSACC owned or operated facilities, industrial pretreatment permit monitoring, process control, lake monitoring, and drinking water bacteria. The laboratory is permitted for 29 wastewater and 3 drinking water parameters.

Interceptor Sewer Collection System

WSACC currently operates and maintains approximately one hundred forty-eight (148) miles of interceptor sewer, ranging in size from 12 inches in diameter to 72 inches in diameter, and five (5) remote pump stations which transport wastewater to the RRRWWTP and the MCWWTP.

Operational and maintenance activities of the department include:

  • New construction
  • Design and structural criteria review, and general inspections.
  • Pump stations: Bi-weekly inspections, operational and maintenance modifications, scheduled preventive maintenance and repairs.
  • Interceptor sewers: Physical and visual inspections of the system, manhole rehabilitation, associated right-of-way maintenance, various flow monitoring, wastewater quality testing, and rainfall recording.

Industrial Pretreatment

WSACC is required by its NPDES permit to implement and enforce a Pretreatment Program for the Rocky River Regional Wastewater Treatment Plant and Muddy Creek Wastewater Treatment Plant. The purpose of the Pretreatment Program is to protect the treatment plants and the environment from damage that may occur when hazardous or toxic wastes are discharged into the wastewater treatment system. The program prevents problems such as upsets or interference with the operation of the wastewater treatment plants, pass-through of pollutants into the receiving waters, sludge contamination, and exposure of workers to chemical hazards. The program also ensures industries comply with the local Sewer Use Ordinance and state and federal regulations.

The Pretreatment Program issues industrial user permits, conducts wastewater monitoring, on-site inspections, and industrial surveys, as well as implements the surcharge program and septage hauler program.

Overall, the Pretreatment Program helps WSACC provide high-quality wastewater treatment services to the jurisdictions we serve.

Dental Facilities
On June 14, 2017, the USEPA promulgated pretreatment standards (40 CFR 441) to reduce discharges of mercury from dental offices into municipal sewage plants known as Publicly Owned Treatment Works (POTWs). The final rule requires dental offices to use amalgam separators and Best Management Practices (BMPs) recommended by the American Dental Association. As the local Control Authority, the Water and Sewer Authority of Cabarrus County (WSACC) is required to implement and enforce the regulation.
The regulation is applicable to all dental dischargers that remove or replace amalgam. It does not apply to dental dischargers that exclusively practice one or more of the following dental specialties: oral and maxillofacial surgery, orthodontics, periodontics, or prosthodontics. Also excluded are mobile units and those practices that only remove or place amalgam in limited emergency or unplanned circumstances. Key points to the standard are:
  1. All amalgam process wastewater must be treated prior to discharge to the POTW utilizing an amalgam separator meeting specific performance standards outlined in the regulation.
  2. For existing sources, including those facilities that do not place or remove amalgam, a One-Time Compliance Report must be submitted to WSACC no later than October 12, 2020, or no later than 90 days after a transfer of ownership. WSACC will work with these facilities to ensure the report is submitted by the deadline established by EPA.
  3. Any new dentist/dental practice that opens on or after July 14, 2017 is considered a “new source” and must comply with the Rule (amalgam separator, BMPs, record keeping) prior to discharging dental wastewater to a POTW.
    •  “New Sources” must comply immediately with all of the requirements upon opening the practice and do not get the 3-year compliance period allowed for an “existing source.”
    • The New Source One-Time Compliance Report is due no later than 90 days following the introduction of wastewater into a POTW.
Water and Sewer Authority
of Cabarrus County

232 Davidson Highway
Concord, North Carolina  28027

704-786-1783  |  Email Us

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