Anaerobic treatment of poultry mortalities in a modified LB-UASB system

The efficiency of a modified LB-UASB system in treating poultry mortalities was tested. The anaerobic digestion system consisted of an upflow anaerobic sludge blanket (UASB) and three leachbeds (LB). The LBs were batch-loaded with mortality to be treated. The LBs were sequentially connected to the UASB, one at a time. Leachate from a connected LB was fed to the UASB while effluent from the UASB overflowed to the LB to form a closed loop. When the concentrations of leachate from the first LB became so low that it could no longer support accelerated methanogenesis in the UASB, it was replaced by a second LB containing a new batch of mortality. Concentrated leachate from the second LB allowed the UASB to continue operation at higher loading rates (LR), thus, alleviating the problems of lengthy LR build-up and idling time. Meanwhile,the off-lined LB continued to mature independently. The UASB was connected to a third LB when the second LB entered accelerated methanogenesis phase. Operation of the first LB was stopped when CH4 production rate from it became marginal. The remaining solids material was replaced by a new batch of mortality to start the second cycle. The first cycle was completed when fermentation in the third LB was ended. The modified LB-UASB system performed significantly better than the original system. It took an average of only 86 days to treat one batch of mortality, yet, the methane yield was about 40% higher. The average methane yield was 0.28 m(3) (kg wet weight)(-1). Strategies to optimize system performances are discussed.