Performance evaluation and microbial community shift of sequencing batch reactors under different nickel (Ni(II)) concentrations

Abstract

Abstract The performance, microbial enzymatic activities and the microbial community shift of sequencing batch reactors (SBRs) were evaluated under long-term exposure to 0–30 mg/L nickel (Ni(II)). More than 5 mg/L Ni(II) showed evident inhibition on NH 4 + -N removal, whereas Ni(II) at 30 mg/L decreased the COD removals of SBRs. The presence of 2 mg/L Ni(II) showed a slight promotion on the microbial nitrifying rates, denitrifying rates and the corresponding enzyme activities, whereas 5–30 mg/L Ni(II) reduced the pollutants removal rates and key enzymatic activity. The inhibition of Ni(II) on the above-mentioned microbial activities gradually increased with an increase in operational time and influent Ni(II) concentrations owing to the continual accumulation of Ni(II) contents in sludge flocs. High Ni(II) concentrations at 5–30 mg/L induced the microbial cellular to produce a higher reactive oxygen species and lactate dehydrogenase level. The microbial diversity and richness gradually declined with an increase in Ni(II) concentrations. The relative abundance of Nitrosomonas, Nitrospira and identified denitrifying bacteria displayed some changes under different Ni(II) concentrations.