Performance and microbial consortium structure in simultaneous removal of sulfur and nitrogen compounds under micro-oxygenated condition

Abstract

Effects of COD/SO42− and SO42−/NH4+ ratios on simultaneous removal of sulfate- and ammonium-rich synthetic wastewaters were investigated under micro-oxygenated condition (dissolved oxygen concentration at 0.10–0.15 mg/L). Lactate was served as carbon source to generate COD/SO42− ratios of 2.0, 2.5, 3.0 3.5 and 4.0. The batch experimental results indicated that the highest sulfate (72.1%) and ammonium (62.8%) removal efficiencies could be reached at COD/SO42− ratio of 4.0. The main metabolic products were elemental sulfur (0.63 g S0/g SO42−–Sadded) and nitrogen gas (0.57 g N2/g NH4+–Nadded). Subsequently, various SO42−/NH4+ ratios (0.5, 1.0, 1.5, 2.0 and 2.5) were performed at controlled COD/SO42− ratio of 4.0. The highest SO42−/NH4+ ratio of 2.5 provided 76.6 and 72.8% sulfate and ammonium removal efficiencies, respectively, and also reached the highest yield of elemental sulfur and nitrogen gas of 0.68 g S0/g SO42−–Sadded and 0.66 g N2/g NH4+–Nadded, respectively. Microbial consortium structure providing the highest removal efficiencies was consequently analyzed using Illumina sequencing and polymerase chain reaction-denaturing gradient gel electrophoresis approaches. Taxonomic assignments demonstrated that Proteobacteria (46%), Firmicutes (15%), and Bacteroidetes (14%) were the most abundant phyla. Almost core genera analysis with two distinguished approaches demonstrated similar results. Aside from microbial community analysis, quantitative real-time polymerase chain reaction was used to validate existing abundance of aforementioned seven dominant microorganisms. The nitrous oxide reductase gene was shown the most abundance (~ 108 copies/µL) which plays a crucial role for simultaneous removal of sulfur and nitrogen compounds.