Bioaugmentation of an anaerobic sequencing batch biofilm reactor (AnSBBR) with immobilized sulphate reducing bacteria (SRB) for the treatment of sulphate bearing chemical wastewater

A bioaugmentation strategy was applied to an anaerobic sequencing batch biofilm reactor (AnSBBR) by inoculating with enriched sulphate reducing bacteria (SRB) in alginate-immobilized matrix for the enhanced treatment of sulphate bearing chemical wastewater. Non-augmented AnSBBR showed 35% of COD removal efficiency and 27% of sulphate reduction. Volatile fatty acid (VFA) accumulation was evidently observed during reactor operation indicating non-functioning of methanogenic bacteria (MB). Poor performance of the reactor may be attributed to process inhibition due to presence of sulphate and non-existence of SRB and MB. Subsequently, the reactor was augmented with enriched SRB consortia entrapped in the alginate matrix. After augmentation the reactor showed significant enhancement in the overall performance. COD removal efficiency enhanced from 35% to 78% and sulphate reduction from 27% to 80%. Concomitant increase in the biogas yield and reduction in VFA concentration in the system were also observed. Microbial diversity in a non-augmented reactor showed about 28% of MB, 66% of acetogenic bacteria (ACB) and 6% of SRB accounting for SRB/total anaerobic bacteria (AnB) ratio of 0.08 indicating the dominance of ACB over the MB and SRB. After augmentation, the microbial distribution varied significantly (45% of ACB, 41 % of MB and 14% of SRB with SRB/AnB ratio of 0.14). The introduction of enriched SRB consortia resulted in altering the competition between anaerobic bacteria in the system leading to the overall improvement in the process performance. (c) 2005 Published by Elsevier Ltd.