Municipal Wastewater Treatment Plants

General Treatment Process:

Ashbrook Supplying 12 Winklepresses Jefferson County, AL, has selected Ashbrook Corporation, a Thames Water Company, to supply 12 Winklepress high solids belt filter presses for the Valley Creek Wastewater Treatment Plant in Bessemer. The plant is expanding operations, and one phase of the expansion will involve construction of a sludge dewatering facility that will house the 12 units and their accompanying control panels. The expansion, which was expected to start in April, was designed by F.W. Dougherty Engineering & Associates Inc., which will also coordinate the project. The total project is worth more than $21 million.

SEDIMENTATION & CENTRIFUGATION NEWSLETTER - April 2002, No. 268 Jefferson County, AL Includes Centrifuges in Expanded Facility In August 2000, the Jefferson County (AL) Environmental Services Dept. placed into operation the largest-known installation of the phased-temperature anaerobic digestion process at its 60-mgd (227,100-m3/d) Village Creek Wastewater Treatment Plant (WWTP) in Birmingham, AL. The purpose of installing the system was to provide an easily operated and conservatively designed facility that would continually meet the U.S. Environmental Protection Agency's (EPA's) requirement for Class A biosolids for use in the county's beneficial land-application program. The new facility consists of two 100-ft-diameter (30-m-diameter), fixed-cover, 30-ft-deep (9-m-deep) thermophilic digesters operated in parallel at 57° C to 60° C. The design solids retention time (SRT) is 8.2 days with an organic loading rate of 0.25 lb volatile suspended solids (VSS)/ft3 d (4.0 kg VSS/m3 d). Each thermophilic digester is fed for a 12-hour interval, then mixed without feeding for 6 hours, and then pumped to the mesophilic digesters. This feeding schedule provides a continuous-flow process while preventing short-circuiting. Three similar-sized, fixed-cover mesophilic digesters with a 12.3-day design SRT and three similar-sized, unheated, floating-cover digesters with a 12.3-day design SRT follow the thermophilic digesters in series. Each mesophilic digester is fed for 2 to 3 hours daily and overflows to the unheated digesters where all supernating takes place. The total design digestion SRT is 32.8 days (28 days with any digester out of service). Both the thermophilic and mesophilic digesters are mixed and heated by Cannon systems from Ondeo Dregemont Inc. (Richmond, VA). The capacity of the new digestion system was based on operating data for solids production at the WWTP in the five years before the new system went online, and allowances for solids production at design flow and from a future peak-flow treatment plant that currently is under construction. Actual solids production is significantly less than design for several reasons: · current flows are at 60 percent of design capacity; · the peak-flow facility has not been completed; · the in-plant pretreatment of digester supernatant and centrifuge centrate has reduced influent suspended solids concentration by about 20 mg/l; and · increased dewatering capability attributable to the new centrifuge facility has reduced the plant's solids inventory.