Effects of Organic-Loading-Rate Reduction on Sludge Biomass and Microbial Community in a Deteriorated Pilot-Scale Membrane Bioreactor

Abstract

The effects of a precipitous decrease in the inlet organic loading rate on sludge reductions and the microbial community in a membrane bioreactor were investigated. The sludge biomass was markedly reduced to 47.4% of the initial concentration (approximately 15,000 mg L⁻¹) within 7 d after the organic loading rate was decreased by half (450 to 225 mg chemical oxygen demand L⁻¹ d⁻¹). An analysis of the microbial community structure using high-throughput sequencing revealed an increase in the abundance of facultative predatory bacteria-related operational taxonomic units as well as microorganisms tolerant to environmental stress belonging to the classes Deinococci and Betaproteobacteria.