The Portland, Indiana, Wastewater Treatment Plant (WWTP) had been using six granular-media filter units for tertiary treatment since the 1980s. The plant’s treatment protocol includes fine screens for grit removal, followed by primary clarifiers, trickling filters, aeration basins, secondary clarifiers, the tertiary treatment system, and then chlorine disinfection.
The problem was that the tertiary media filters required too much maintenance and excessive backwashing. According to Robert Brelsford, Superintendent, “Not a day went by that we didn’t have to work on them, particularly on the control valves.” Besides problems with the 30 control valves, the plant had trouble with broken underdrains and with losing media. And perhaps most significantly, “the system required about 10,000 gallons per backwash, says Brelsford.