The Rocky River Regional Wastewater Treatment Plant (RRRWWTP) is a two stage 24 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 incinerator 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, nearly eliminating 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.