VALUABLE BY-PRODUCTS RECOVERY FROM CATTLE WASTES USING TEMPERATURE-PHASED ANAEROBIC DIGESTION PROCESS

The performance of TPAD process in the digestion of livestock wastes has never been evaluated, though the process has proven advantages over other high-rate anaerobic digestion processes in the treatment of municipal wastewater sludge. This study investigated the applicability of TPAD process in the stabilization of dairy cattle manure. For all the organic loadings investigated, volatile solids reduction in the range 36–40%was achieved with biological conversion efficiency of 0.58–0.62 L methane/g of volatile solids destroyed. Pathogen counts in the residual solids were less than the limits specified by U.S.E.P.A to meet class A standards. The high volatile fatty acid concentrations in the thermophilic reactor were reduced significantly by the mesophilic stage and the ammonia nitrogen concentrations in the reactors were below inhibitory levels. The process was stable at all the organic loading rates studied.