Natural gum based polymers as additives in enhancing the startup of UASB reactor treating municipal sewage - comparative study

This work has focused on the potential of natural gum based polymers as additives, to enhance the startup of upflow anaerobic sludge blanket (UASB) reactors treating municipal sewage. A laboratory study was taken up to substantiate this novel idea. Under identical conditions 4 similar UASB reactors were operated in parallel. Reactors locust bean gum (LBG) and guar gum (GG) were injected with the novel bio-flocculants LBG and guar gum. For better insights their performance was compared with the well proven cationic polymer chitosan, in reactor (CH). Reactor (CT) without any additive served as control. Reactor with LBG as additive outclassed others with an accelerated startup in 40 d reaching a maximum chemical oxygen demand removal of 92.5%, followed by GG, CH and CT with 88%, 80% and 60% removal respectively at the end of study period. Both LBG and GG also succeeded with a dense sludge bed anchoring most of the anaerobes denoted by a least sludge volume index of 26.2 and 29 mL/g, followed by high volatile suspended solids/ total suspended solids ratio of 0.75 and 0.72, respectively. Specific methanogenic activity and ECP secretions of all 4 reactors were almost similar, indicating that early granulation was primarily induced by the polymers. Hence in a nut shell, polymer enhanced reactors visualized an accelerated startup along with better biomass retention than the control.

Automated summary

This study focuses on the potential of natural gum based polymers as additives to enhance the startup of UASB reactors treating municipal sewage. The results show that reactors with novel bio-flocculants LBG or GG as additives demonstrate accelerated startup and better biomass retention.