A Laboratory Scale Sequencing Batch Reactor with the Addition of Acetate to remove Nutrient and Organic Matter in Pig Slurry

The influence of carbon addition on performance of a laboratory-scale, anaerobic–anoxic–anaerobic–anoxic sequencing batch reactor [(An/Ax)2 SBR] in biologically removing nitrogen and organic matter from swine slurry was investigated in this study. The SBR was operated on three cycles per day (8 h per cycle) at constant 20 °C using raw slurry feeding until it reached a steady functional condition. After that, the SBR was subjected to a feeding treatment with addition of acetate. The sludge retention time and hydraulic retention time were maintained at 21 and 3·3 days for the experiment. The results indicate that with acetate addition, the removals of ammonium nitrogen, total Kjeldahl nitrogen, chemical oxygen demand, biochemical oxygen demand, and total phosphorus are 100·0%, 98·7%, 97·4%, 100·0%, and 98·7%, respectively. While without acetate addition, the corresponding reductions are 100·0%, 100·0%, 97·7%, 100·0%, and 97·8%. None of the feeding treatments (slurry alone or with acetate) appear to be effective in removing nitrate and nitrite due possibly to insufficient time allocated for denitrification, even when carbon is readily available. The removal of dissolved phosphorus by phosphorus-accumulating organisms reaches 87·2% with acetate addition but only 67·9% without. A good reduction in total solids (77·5% and 78·8%), total volatile solids (97·0% and 95·6%), total suspended solids (99·9% and 99·3%), and total volatile suspended solids (99·1% and 98·4%) for both treatments is also observed.