Contributions of enhanced endogenous microbial metabolism via inoculation with a novel microbial consortium into an anoxic side-stream reactor to in-situ sludge reduction for landfill leachate treatment

In-situ sludge reduction plays a significant role in reducing excess sludge production. This study investigated the role of beneficial microorganisms (BM) in the anoxic-oxic-settling-anoxic (A-OSA) process associated with the in-situ sludge reduction efficiency under synthetic landfill leachate treatment. The rates of excess sludge reduction with the inoculation of BM increased up to 53.6% (calculated as total suspended solids) and 38.3% (calculated as total volume), respectively. Side-stream reactors, as important components of the A-OSA process, were further studied to explore change of parameters related to in-situ sludge reduction. With the inoculation of BM, the release and conversion of extracellular polymeric substances and the dehydrogenase activity (increasing rate = 60.9%) were increased. Species richness and microbial diversity, as well as the microbial community composition (e.g., hydrolytic and fermentative bacteria), were improved via bioaugmentation. Moreover, potential gene functions of microorganisms were positively regulated and the abundance of gene expressions (e.g., nirK, norB) for in-situ sludge reduction could be improved.