MUA’s Seven Mile-Middle Plant Under Capacity, Tops Standards

COURT HOUSE –– What do they DO in those wastewater treatment plants?
Many are not familiar with the process by which the county Municipal Utility Authority prepares sewage wastewater here at the Seven Mile Regional management facility.
“Most people just flush and forget,” Chemist James Neville said.
The Seven Mile-Middle Regional facility treats water from Sea Isle City, Stone Harbor, Avalon, Avalon Manor, Middle Township and Crest Haven.
The plant is able to treat 7.67 million gallons per day with ample untapped capacity; at its busiest it runs at only 80 percent capacity or 6.3 million gallons per day, which was this summer’s peak usage, Neville said. Three out of four primary clarifiers are in use and all clarifiers are not at maximum flow.
“We are able to take things offline for maintenance without compromising treatment,” Neville said.
On average the plant treats 5.2 million gallons per day during the week and 5.8 million gallons each day during the summer weekends.
The Municipal Utility Authority (MUA) bases water allocations on an average of 400 gallons per household at 100 gallons per person each day. Municipalities flow contribution dictates its residents’ user rates.
The MUA is in the process of implementing a water reuse program in which effluent would be treated to a higher level and sent to the Cape May County Park and Zoo via pipelines be-neath the Garden State Parkway.
The “brown water” could then be used to water grass, bathe animals and for fire fighting purposes since it need not be potable. The project is a cooperative effort between Cape May County, the MUA and Middle Township. It is currently out to bid and seeking necessary permits.
Wastewater goes through an intricate purification process before being dumped at several outfall areas, each a mile out in the ocean.
Pipelines are located at 30th Street in Avalon and Jefferson Avenue in Lower Township at least 30 feet below ocean surface, below what’s known as the “focal zone,” which is the depth sun can penetrate water.
Sewage first travels through a bar screen to filter chunky debris that could potentially damage the equipment. The machinery uses gravity to help in the filtering process with influent starting at the highest point and traveling downward.
Next, sewage water is aerated through a grit removal system, which allows heavy inorganic materials, like sand, to settle to the bottom. It’s then taken through a primary clarifier settling-tank where floatables rise to the top and are skimmed off. Sludge is thickened with polymer and compacted into cake-like substance and stored for use in Cape Organic compost sold by the MUA.
In efforts to disinfect water to swim standards or better before it’s released, enemy number one is Biochemical Oxygen Demand (BOD), a contaminant in the water with the ability to rob it of oxygen.
The MUA lab tests oxygen levels in the water in order to cut down on BOD. Under permit, the plant is legally allowed to discharge water with a BOD level of 30 milligrams per liter or less. Neville said the Seven Mile Regional plant discharge has an average BOD level of only 10 milligrams per liter. Therefore, the plant runs three times more efficient than is required by state permits. Neville said these BOD levels are lower during storms as rain-water dilutes sewage.
The plant is able to control discharge pipes with computers that display which pumps are working. Computers sample BOD levels in the water every half an hour to compile a daily report.
Water travels through six Rotating Biological Contactors (RBCs), circulating interwoven plastic discs that attract microorganisms, which are needed to break down the BOD. Finally water is disinfected before being discharged.
Contact Truluck at (609) 886-8600 ext. 24 or at: ltruluck @cmcherald.com.