Performance evaluation of a novel upflow anaerobic sludge blanket reactor with built-in downflow hanging sponge module for the treatment of municipal sewage

The present study investigates the potential of a novel upflow anaerobic sludge blanket (UASB) reactor with a built-in polishing facility for the treatment of municipal sewage. A laboratory-scale reactor, which combined an inner-centric hybrid UASB module and an outer concentric downflow hanging sponge (DHS) unit, was designed and fabricated as a part of this research work. The reactor had been continuously operated for 210 days under ambient conditions. With anaerobically digested sewage sludge (seed sludge blended with Locust bean gum polymer) as inoculum, the reactor attained a successful startup in 40 days. Ensuring startup, the reactor was employed under varying organic loading rates (OLR) from 0.87 to 5.09 kg COD/m3/d, with corresponding hydraulic retention times (HRT) of 24–4 h. The novel UASB reactor made its mark with a high COD and TSS removal of 93.2% and 93%, respectively, under the optimum conditions of 6-h HRT. In addition, biogas rich in methane content (68%), with a maximum specific yield of 0.42± 0.02 m3 biogas /kg COD destroyed, was generated. The VSS/TSS ratio observed a steady rise (0.51 to 0.75) with increasing sludge age, bearing witness to the active growth of biomass. Hence, in brief, the novel UASB reactor can be coined as an energy economic system with improved effluent quality.