PWPF Settled Solids Dewatering Facility

The City of Cumming operated an 18.0 MGD potable water production facility that used a series of shallow ponds to remove solids generated by the water treatment process. The settled solids removal process in the shallow pond system was inefficient and significantly undersized for the 18.0 MGD capacity of the water treatment plant. CEC recommended a plate and frame filter press process to improve the capture and dewatering of the settled solids, which can be characterized as alum sludge.

The overall process included two 80-foot circular gravity thickeners, two thickened sludge transfer pumps (air diaphragm pumps, 100 gpm @ 40-feet), sludge conditioning with polymer, positive displacement and a sludge press feed pump (211 gpm at 150 psi). The filter press metal plates are 1,500 mm with a 113 cf capacity in 74 chambers. The filter press is equipped with a 22 psi membrane squeeze system and automatic 50 gpm, 1,500 psi cloth wash system. The filter press also has a compressed air 240 SCFM at 100 psi core blow system.

Settled solids dewatered to about 35% solids are automatically removed from the filter press and drop into a 16 cy dump truck for disposal. The solids are transported and disposed of in the old shallow ponds previously used for the settled solids removal. The settled solids dewatering facility has been operating successfully since 2001. The press system is housed in a two-floor, 90-ft by 53-ft by 35-ft high brick veneer and block building. The building includes an office and small process lab.