AWWA ACE59826

Faced with rising sludge hauling and disposal costs, Gwinnett County, Georgia, retained CDM toevaluate options for residuals disposal and ultimately pilot, design, and oversee construction of anew residuals handling facility to dewater the filter backwash water residuals generated at their150-million-gallons-a-day (mgd) surface water treatment plant, the Lanier filter plant, and theirfuture 150-mgd Shoal Creek filter plant. Pilot testing comprised two stages, a bench-scalescreening of various dewatering technologies followed by pilot-scale confirmation andoptimization of the chosen dewatering technology. Evaluated dewatering technologies includedbelt filter presses, plate-and-frame filter presses, and centrifuges.Once the pilot data was gathered, it was used to develop the design criteria for the full-scalefacility. Design features include inclined plate settlers and picket fence thickeners using polymercoagulant, a sludge transfer and chemical conditioning system featuring liquid lime and ferricchloride chemical conditioning, and two plate-and-frame filter presses that discharge thedewatered solids into roll-off containers located below. The filter presses are a mixed packconfiguration that have fixed-volume recessed chamber plates alternating with diaphragm styleplates that can be pressurized to compress the sludge further. The new facility was designed in amanner that met the U.S. Environmental Protection Agency's (EPA) backwash recycle rule,which requires that any recycle stream be routed to the head of the treatment plant. Anotherrequirement was that the new facility also reduced the solids loading on the existing filterbackwash sedimentation basin and sludge collection system, which were overtaxed due to theincreasing plant production needs.Construction of the new facility ran from late 2000 to mid 2002. The facility is now on-line,allowing the county to begin to realize substantial savings in sludge hauling and disposal costs. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

06/17/2004

Number of Pages:

20

File Size:

1 file , 1000 KB