The water flows into the Aeration Tanks to be mixed with pure oxygen and secondary sludge. In the Aeration Tanks, bacteria consume more pollutants. The wastewater proceeds to the Chlorine Contact Tanks . The Winslow plant, a much smaller site, uses a similar though smaller scale process. Two major differences are that the Winslow plant uses air instead of pure oxygen and that the treated wastewater is disposed of in Recharge Basins .
Pure oxygen is used at the main plant because of space limitations.
The plant is hemmed in by a residential neighborhood to the east and the Delaware River to the west. In order to deal with the continuously arriving flow, without using more space for Aeration Tanks, pure oxygen is mixed with the wastewater. This allows much faster bacterial growth and purification. The Recharge Basins used by the Winslow plant are sand-lined open pits. Water seeps slowly through the special fine sand in the bottom of the pit as a final purification step.