Anaerobic Treatment of Low-Strength Wastewater in a Biofilm Reactor

A 3.9-L (70-cm high) upflow anaerobic filter (AF) packed with corrugated plastic rings was employed to evaluate the direct treatment of low-strength wastewater over a long period of operation (32 months at 25.4 degrees C and 2 months at 15.5 degrees C). The AF was fed four complex synthetic-type wastewaters with a low-solids content [chemical oxygen demand (COD) 325-403 mg L(-1), soluble COD (SCOD) 86-339 mg L(-1) and total suspended solids (TSS) 65-156 mg L(-1)] at organic loading rates (OLR) ranging from 0.02 to 0.91 kg COD m(-3) d(-1). Operation with filtered municipal wastewater supplemented with a sugar-nutrient based substrate (OLR 0.27-0.91 kg COD m(-3) d(-1)) yielded removal efficiencies in the range of 72-80% for COD and 80-92% for TSS, and use of a completely synthetic substrate resulted in improved effluent quality. Under these test conditions, removal of organic matter and solids occurred within the first 40cm of column height and accumulation within the reactor was not substantial or affected by the length of operation.