City Island Wastewater Treatment Plant
By Anonymous
Location: Atlantic City, N.J.
Startup date: 1978
Service population: 252,500
Number of employees: 79, including lab and administration
Average daily flow: 29 mgd (110,000 m^sup 3^/day)
Design flow: 40 mgd (151,400 m^sup 3^/day)
Peak flow: 75 mgd (284,000 m^sup 3^/day)
Annual operating cost: $25,960,000
Reliable, cost-effective wastewater treatment service is an important part of protecting the environment and human health in most communities, but for Atlantic City, N.J., wastewater treatment has been a link to economic development. Without it, Atlantic City’s casino industry would not have been possible. Realizing this, in 1969 Atlantic County implemented a program – which would become the Atlantic County Utilities Authority (ACUA) – to manage wastewater. In 1975, ACUA began construction on the City Island Wastewater Treatment Plant.
But the facility is not stuck in the past. In fact, Atlantic City’s City Island wastewater treatment facility is home to one of the largest hybrid solar-wind power plants in the world. Dedicated in Dec. 2005, the facility generates an estimated 40,800,000 kW/h annually – helping to provide for the energy needs of the 29-mgd (110,000-m^sup 3^/day) wastewater treatment plant (WWTP).
The facility is also the recipient of 10 gold and two platinum awards for large WWTPs, as awarded by the National Association for Clean Water Agencies (NACWA; Washington, D.C.).
Treatment Overview
The treatment process begins in the collection system where 20 regional pump stations use course manual bar screens to remove the largest pieces of debris. Flow meters allocate flow to member municipalities. Upon entering the City Island facility, wastewater passes through mechanically-cleaned bar screens. Material recovered from screens is compacted and disposed of at a sanitary landfill.
Next, the wastewater is routed to five circular primary clarifiers, where ferric chloride and polymer are added to enhance settling.
Mixed liquor suspended solids are kept at approximately 2000 mg/ L in all six of the rectangular aeration tanks. Surface aerators provide aeration to a concentration of approximately 1 mg/L. After the mixed liquor is routed to six final sedimentation tanks, a 15% solution of sodium hypochlorite is added for disinfection.
Finally, the disinfected effluent passes through a 3-mi (4.8 km) force main to a 1.5-mi (2.4-km) ocean outfall.
The City Island Wastewater Treatment Plant in Atlantic City, N.J., is home to one of the largest hybrid solar-wind power plants in the world.
The solids from the primary and final clarifiers are thickened separately. Two gravity thickeners removed excess water from the primary sludge, while three waste activated sludge centrifuges thicken the settled material from the final sedimentation tanks. After thickening, a solid bowl centrifuge further dewaters the combined material to approximately 25% solids. The dewatered solids are then incinerated in one of two multiple hearth incinerators, and the ash disposed of in a sanitary landfill.
Dedicated in Dec. 2005, the hybrid solar-wind power facility at the City Island Wastewater Treatment Plant in Atlantic City (N.J.) generates an estimated 40,800,000 kW/h annually.
A Bright Future
The installation of the solar-wind plant at the City Island facility will produce enough energy to power the equivalent of 2500 homes and eliminate the need for an estimated 24,000 barrels of oil per year.
Between the wind and solar energy, the power plant will provide as much as 40/6 of the facility’s energy needs. And, although the solar portion of the project alone cost $3.25 million, $1.9 million of the cost was offset by a rebate from the New Jersey Board of Public Utilities Office of Clean Energy. Additionally, AUCA estimates that it will save $135,000 annually, through reduced energy use and the sale of solar renewable energy certificates that the system will generate.
Copyright Water Environment Federation Mar 2006