In anticipation of significant growth in its service area, the Tohopekaliga Water Authority (TWA; Kissimmee, Fla.) needed a master plan for its biosolids. This plan should outline an effective biosolids management strategy based on recent technical advances, scientific research, evolving federal and state legislation, and community expectations. TWA owns and operates nine water reclamation facilities. Only one of these dewatered residuals: the South Bermuda facility, which also treated residuals from the Sand Hill Road, Camelot, Harmony, and Parkway water reclamation facilities. At press time, the dewatered solids were transported to an offsite vendor for further stabilization and final disposal. The other four facilities were part of the Poinciana system that TWA had recently acquired. They aerobically digested residuals to produce liquid Class B biosolids, which were land-applied. It was time to rethink the biosolids management strategy. The Biosolids Master Plan team determined that TWA should install dewatering systems at all of its facilities and then transport the dewatered solids to a new biosolids management facility, which would produce Class A biosolids. Dewatering the solids first would reduce transportation costs significantly. TWA decided to start by retrofitting the Sand Hill Road Water Reclamation Facility. This dewatering installation also would serve as a pilot for the rest of TWA’s facilities. Sand Hill Road is a 22,700-m3/d (6-mgd) activated sludge plant that can use the Four-Stage Bardenpho or Modified Ludzack-Ettinger process for biological treatment. At press time, settled secondary solids were transferred to two 1098-m3 (290,000-gal) holding tanks, partially digested and thickened to 1.5% to 2% solids, and then transported to South Bermuda for dewatering.
Step 1: Dewatering
Authors: George P. Anipsitakis, Michael R. Leffler, J. Richard Voorhees, Robert J. Leacock, Edward B. Scott, Rick Nipper and Quyen M. Newell
2010 Water Environment & Technology magazine, pp. 24-29.