Single and combined effects of divalent copper and hexavalent chromium on the performance, microbial community and enzymatic activity of sequencing batch reactor

摘要

Divalent copper (Cu~(2+)) and hexavalent chromium (Cr~(6+)) are often encountered in industrial wastewater and municipal wastewater, the effect of combined Cu~(2+) and Cr~(6+) on biological wastewater treatment systems has cause wide concern. In the present research, the performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were compared under the single and combined Cu~(2+) at 20 mg/L and Cr~(6+) at 10 mg/L The chemical oxygen demand (COD) and ammonia nitrogen (NH_4~+ -N) removal efficiencies under the combined Cu~(2+) and Cr~(6+) were less than those under the single Cu~(2+) and Cr~(6+). The combined Cu~(2+) and Cr~(6+) displayed more inhibition effects on the oxygen uptake rate, nitrification rate and denitrification rate of activated sludge than the single Cu~(2+) and Cr~(6+). The inhibitory effects of the combined Cu~(2+) and Cr~(6+) on the activities of dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase showed significant increases by comparison with the single Cr~(6+). However, the combined Cu~(2+) and Cr~(6+) had a little more inhibitory effects on the enzymatic activities than the single Cu~(2+). The microbial richness and diversity displayed some obvious changes under the single and combined Cu~(2+) and Cr~(6+) by comparison the absence of Cu~(2+) and Cr~(6+). The relative abundances of nitrifying genera (e.g. Nitrosomonas and Nitrospira) under the combined Cu~(2+) and Cr~(6+) was less than those under the single Cu~(2+) and Cr~(6+). These findings will be helpful to better understand the combined effects of multiple heavy metals on biological wastewater treatment systems.