About Delaware No. 1 Water Pollution Control Facility...

JUNCTION CHAMBER

Three underground pipes bring influent to the junction chamber, where the three flows mix before entering the Preliminary Treatment Facility. One of the two main pipes brings sanitary sewage from the main regional collection system. The second brings sewage from the Camden City collection system. A smaller pipe brings sewage from North Camden and Pennsauken.

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PRELIMINARY TREATMENT FACILITY

In the preliminary treatment facility, the wastewater flows through three mechanically cleaned bar screens which catch debris, rags, and large solid objects. After this stage, centrifugal pumps lift the wastewater 35 feet (a little more than ten meters) to begin its trip through the gravity-fed treatment tanks.

Next the water enters three rectangular grit chambers, where small stones and sand settle out. Removing sand and larger solid objects helps extend the life of equipment. The grit and screenings are pumped to grit separators and washers where they are cleaned before being trucked to sanitary landfills.

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PRIMARY SEDIMENTATION TANKS

Wastewater takes 12 to 15 hours to flow through the primary sedimentation tanks. During this slow passage, solids settle to the bottom of the tanks. These solids, called "primary sludge", are skimmed off the bottom and held for further processing. Oil and grease scum is skimmed off the top of the primary sedimentation tanks into scum wells.

Delaware No. 1 Water Pollution Control Facility has ten primary sedimentation tanks, measuring about 186 feet by 50 feet (57 x 15.24 meters) with an average side water depth of ten feet (3 meters).

The primary sedimentation tanks remove 50 - 60% of the solid contaminants in the wastewater. When the plant was run by the city of Camden, this was all the treatment provided before discharging the wastewater into the Delaware River. The CCMUA purchased the plant and upgraded it to produce cleaner water.

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AERATION TANKS

In the aeration tanks, "primary wastewater" coming from the primary sedimentation tanks is mixed with oxygen and secondary sludge - a mixture of dead microbes and bacteria coming from the final sedimentation tanks down the line. The wastewater spends four hours in the aeration tanks. These tanks are designed to be "bacteria heaven", with a combination of warm temperatures (about 40 Celsius or 104 Fahrenheit), food (the organic solids in the wastewater), and oxygen. Under these circumstances, bacteria grow and consume the organic solids very quickly.

There are eight aeration tanks at Delaware No. 1. Each tank is about 220 feet by 55 feet (67 x 16.76 meters), with an average liquid depth of 15 feet (4.6 meters). Mechanical surface aerators are used to mix the activated sludge, the primary wastewater, and the oxygen.

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FINAL SEDIMENTATION TANKS

In the aeration tanks, the bacteria have formed clumps as they grow and consume solids. Here in the final sedimentation tanks, these clumps are allowed to settle to the bottom forming secondary sludge. Secondary sludge is more liquid than primary sludge. It is composed of small particles. About 30 % of the secondary sludge is recycled to the aeration tanks. The rest is removed for further processing.

Delaware No. 1 WPCF has eight final sedimentation tanks. Each is about 270 feet long by 78 feet wide (82 x 24 meters).

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CHLORINE CONTACT TANKS

The final stage of treatment takes place in the chlorine contact tanks. To kill any remaining bacteria, the water is mixed with a solution of sodium hypochlorite. (This is the same chemical found in household chlorine bleach.)

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OUTFALL

The treated wastewater is discharged through an outfall pipe into the Delaware River. It has spent about one full day passing through the treatment plant.

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