Continuous treatment of dairy effluent in a downflow anaerobic filter packed with slag grains: Reactor performance and kinetics

Abstract

A downflow anaerobic filter packed with blast-furnace slag (BFS) grains was evaluated for treating cheese whey, a high-strength dairy effluent. The reactor demonstrated effective and stable biomethanation of whey in continuous mode without pH control. The chemical oxygen demand (COD) removal remained at around 80%, with the reactor pH being maintained neutral without buffering, in the organic loading rate (OLR) range of 0.8-2.4 g COD/l∙d. Although the COD removal decreased down to below 60% at higher OLRs along with acid accumulation, the methane production rate continued to increase with increasing OLR. On the other hand, the methane yield was maintained at 0.28-0.34 l/g COD throughout the experiment. The substrate removal and methane production kinetics were successfully described by the modified Stover-Kincannon model. The overall results suggest that BFS grains could be used as economic filter media for anaerobic treatment of cheese whey and other easily acidifying waste streams.