Mixing characteristics and performance of the anaerobic upflow blanket filter (UBF) reactor

Abstract

AbstractMixing characteristics (using a radioactive tracer) and reactor performance of the upflow blanket filter (UBF) reactor operated at different loading rates (up to 32 kg chemical oxygen demand (COD) m−3 day−1) were compared. The results indicated that mixing profiles of the reactor operated with effluent recirculation and without biomass were of the perfectly mixed type. Operation without recirculation resulted in about 18% dead space. The filter made of plastic rings and located in the top third of the reactor had no negative effect on reactor mixing. Operation at loading rates of up to 25 kg COD m−3 day−1 permitted a soluble COD removal rate of 95% with a methane production rate of 5.9 m3 m−3 day−1. At higher loading rates, the efficiency of COD reduction decreased with a decrease of the specific acetoclastic activity to 0.5 kg acetate removed per kg volatile suspended solids (VSS) day−1. At all loading rates studied it was observed that the performance was not related to the mixing characteristics, which had remained of the perfectly mixed type with an occasional small dead space (below 10%). The good mixing characteristics of the UBF reactor coupled with the high biomass content and the effective action of the filter make this reactor one of the most promising designs for the treatment of soluble wastes.