Tour of the Southwest Philadelphia Water Pollution Control Plant
The Southwest Water Pollution Control Plant is one of three waste water treatment facilities in the Philadelphia Water Department system and serves the western portions of Philadelphia and areas in eastern Delaware and southeastern Montgomery counties.
The Southwest plant was designed to handle an average annual flow of 200 MGD and a peak flow of 400 MGD. In Fiscal Year 2012, the plant treated an average of 183 MGD. The facility operates under a National Pollution Discharge Elimination System (NPDES) permit mandated by the PA-DEP and plant performance is well within permit limits with effluent concentrations consistently below 10 mg/l for CBOD and TSS.
The plant liquid stream processes include influent pumping, screening, grit removal, pre-aeration/flocculation, primary clarification, secondary treatment using pure oxygen activated sludge, secondary clarification, effluent pumping, and disinfection.
Sludge collected from the secondary treatment process is thickened in Dissolved Air Floatation Tanks and then combined with the Primary sludge. The combined sludge is anaerobically digested at a minimum temperature of 95oF and pumped to an adjacent facility, operated by Philadelphia Renewable Biofuels, for further processing. They dewater the biosolids in centrifuges and the generated cake is fed to one of two sludge dryers which produce a Class A pellet that can be used as a fertilizer or potentially as a fuel.