OPTIMIZATION TECHNIQUE FOR SEWAGE-SLUDGE CONDITIONING WITH POLYMER AND SKELETON BUILDERS

This study investigates sewage sludge conditioning with optimized combinations of a polymer and skeleton builders prior to fiter pressing. The objective is to produce a more porous and incompressible cake structure needed for successful sludge dewatering. Response surface methodology (RSM) was used as the experimental design strategy to optimize sludge conditioning, based on the resulting net sludge solids yield. Fly ash from a municipal sludge incinerator, cement kiln dust, and bagasse were found to be successful skeleton builders for dewatering primary sludge from a wastewater treatment plant that processes a mixture of industrial and municipal effluents. The commercial product CALGON WT-2640, a 6% by weight aqueous polymer solution, was used as chemical conditioner. The optimum conditioning strategy when using flyash as a skeleton builder was found to be the addition of a polymer dose of 1.1% and a fly ash dose of 151%, both based on the original dry solid content of the sludge. This combined treatment increased the net sludge solid yield by 580% when compared to conditioning only with polymer. The optimum conditioning strategy when using cement kiln dust was to add the same dose of polymer as before, and a cement dust dose of 173%. This combined treatment increased the net sludge solid yield by 96%. For conditioning with bagasse, a polymer dose of 1.33% and a bagasse dose of 37% was the optimum strategy. The resulting increase in net yield was 1260%.