DEVELOPMENT OF A NOVEL, 2-STEP PROCESS FOR TREATING MUNICIPAL BIOSOLIDS FOR BENEFICIAL REUSE

Modern municipal sewage waste treatment plants use conventional mechan ical and biological processes to reclaim wastewaters. This process has an overall effect of converting a water pollution problem into a soli d waste disposal problem (sludges or biosolids). An estimated 10 milli on tons of biosolids, which require final disposal, are produced annua lly in the United States. Although numerous disposal options for bioso lids are available, Including land application, landfilling, and incin eration, disposal costs have risen, partly because of increased federa l and local environmental restrictions (1). A novel, thermomechanical biosolids pretreatment process, which allows for a variety of potentia l value-added uses, was developed. This two-step process first employs thermal explosive decompression to inactivate or kill the microbial c ells and viruses. This primary step also results in the rupture of a s mall amount of the microbial biomass and increases the intrinsic fluid ity of the biosolids. The second step uses shear to effect a near-comp lete rupturing of the microbial biomass, and shears the nondigested or ganics, which increases the overall surface area. Pretreated biosolids may be subjected to a secondary anaerobic digestion process to produc e additional fuel gas, and to provide for a high-quality, easily dewat ered compost product. This novel biosolids pretreatment process was re cently allowed a United States patent.