PRETREATMENT TECHNOLOGY FOR THE BENEFICIAL BIOLOGICAL REUSE OF MUNICIPAL SEWAGE SLUDGES

Modern municipal sewage waste treatment plants use conventional mechan ical and biological processes to reclaim waste waters. This process ha s the overall effect of converting a water pollution problem into a so lid waste disposal problem (sludges). The costs for conventional dispo sal of Sewage sludges have risen dramatically because of increased env ironmental mandates, which restrict their disposal, as well as a dwind ling number of landfills. Previously, we determined that secondary bio processing (specifically anaerobic digestion) was not effective in red ucing the organic content and bulk of the sludge waste (1). Therefore, we have examined the potential of a variety of pretreatment technolog ies designed to disrupt the macrostructure of the sludge and thereby e nhance its subsequent biodegradation. Two thermal/mechanical pretreatm ents tested were found to have a dramatic effect on the subsequent bio conversion of the microbial sludges. Both technologies evaluated, soni cation and shear, were found to be affected by sludge solids levels, d uration of treatment, and treatment temperature. Optimum sonication pr etreatment occurred with sludge solids of 1% and treatment times of 4- 8 min. The most effectivee treatment temperature tested was 55 degrees C. The optimum enhancement in bioconversion potential for the sonicat ion pretreatment was 80-83% of the materials carbon oxygen demand (COD ) content. The optimum shear pretreatment occurred with sludge solids of 1-2% and treatment times of 6-10 min. The most effective treatment temperature tested was 87 degrees C. The optimum enhancement in biocon version potential for the shear pretreatment was 88-90% of the materia l's COD content. These data were the basis for US parent no. 5,380,445 , granted January 10, 1995.