Simultaneous loading and draining as a means to enhance efficacy of sequencing biofilm batch reactors

In a sequencing biofilm batch reactor (SBBR) wastewater is treated by bacte ria growing on support media packed in the reactor body. In addition, the p acking serves as filter media to minimize the concentration of suspended so lids in the effluent. Mathematical simulation studies and tracer experiment s at lab-scale and semi-full-scale reactors were conducted to investigate t he hydraulic retention time distribution Function and flow patterns under v arious hydraulic loading rates. Results obtained reveal that introduction o f a new batch of wastewater and withdrawal of the purified water can be exe cuted at the same time without running the risk of polluting the effluent o f the reactor with not yet treated wastewater. At a volumetric exchange rar e of 68% in the lab-scale SBBR and 90% in the semi-full-scale system, respe ctively, the front of the tracer remained well underneath the effluent weir . Application of the fill/displacement strategy allows reduction of the cyc le time and enhanced exploitation of the reactor volume. (C) 2000 Elsevier Science Ltd. All-rights reserved.