Faced with rising sludge hauling and disposal costs, Gwinnett County, Georgia, retained CDM to
evaluate options for residuals disposal and ultimately pilot, design, and oversee construction of a
new residuals handling facility to dewater the filter backwash water residuals generated at their
150-million-gallons-a-day (mgd) surface water treatment plant, the Lanier filter plant, and their
future 150-mgd Shoal Creek filter plant. Pilot testing comprised two stages, a bench-scale
screening of various dewatering technologies followed by pilot-scale confirmation and
optimization of the chosen dewatering technology. Evaluated dewatering technologies included
belt 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-scale
facility. Design features include inclined plate settlers and picket fence thickeners using polymer
coagulant, a sludge transfer and chemical conditioning system featuring liquid lime and ferric
chloride chemical conditioning, and two plate-and-frame filter presses that discharge the
dewatered solids into roll-off containers located below. The filter presses are a mixed pack
configuration that have fixed-volume recessed chamber plates alternating with diaphragm style
plates that can be pressurized to compress the sludge further. The new facility was designed in a
manner 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. Another
requirement was that the new facility also reduced the solids loading on the existing filter
backwash sedimentation basin and sludge collection system, which were overtaxed due to the
increasing 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.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1000 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 06/17/2004 |
