Efficacies of a locust bean gum polymer on the startup of a novel upflow anaerobic sludge blanket reactor treating municipal sewage

Abstract

The present study investigates the potential of locust bean gum (LBG), in accelerating the startup of a novel upflow anaerobic sludge blanket (UASB) reactor handling municipal sewage. Under identical conditions, two lab-scale UASB reactors were operated in parallel, to substantiate this idea. The novel reactor (RH) with an inner centric hybrid UASB module and an outer concentric downflow hanging sponge (DHS) unit started off with an LBG polymer as an additive. Its performance was compared with a conventional system (RC). RH outclassed with an accelerated startup in 40 days, with the highest COD removal of 89% by the UASB compartment and 95% by the entire system (UASB + DHS). RC took nearly 85 days to achieve the highest COD removal of 83%. The polymer also succeeded with a dense sludge bed fastening most of the anaerobes, read by the least sludge volume index (SVI) of 26 mL/g. Specific methanogenic activity (SMA) (RH – 0.715 ± 0.05 and RC – 0.670 ± 0.07 g CH4-COD/g VSS/ day) and extracellular polymer (ECP) concentration (0.30–0.32 g/g VSS) of biomass in both reactors were almost similar. This further confirmed that early granulation was induced solely by the polymer and it also had no deleterious impact on substrate transfer. HIGHLIGHTS Enhancement of anaerobic granulation by natural gum-based polymer – locust bean gum.; Polysaccharidic structure, self-gelling property, and good coagulating potential of the biopolymer, favored aggregation of microflora in the sludge bed.; The novel UASB reactor was designed to bear the resemblance of clariflocculator – inner centric UASB module and an outer concentric downflow hanging sponge unit;

Keywords

• anaerobic
• granulation
• locust bean gum
• municipal sewage
• startup phase
• upflow anaerobic sludge blanket reactor