Biological treatment of cadmium (Cd2+)-containing wastewater with sulfate as the electron acceptor and its microbial community

Abstract

The pollution of cadmium (Cd) to environment is becoming increasingly serious. In this study, the ability of the continuous flow bioreactor with sulfate as the electron acceptor to remove pollutants from Cd-containing wastewater was investigated. The results show that Cd²⁺ could be effectively removed and the concentration of Cd²⁺ in the anaerobic effluent is less than 0.01 ​mg/L. Cd can affect the decomposition of urea by anaerobic sludge. In addition, ammonia nitrogen could be also effectively removed with the removal rate was approximately 72.4%. The activated sludge mainly removed Cd through the precipitation of cadmium sulfide outside the bacteria after sulfide was generated by bacterial sulfate metabolism, facilitated continuous biological removal of Cd from wastewater. Microbial community structure analysis revealed Trichococcus and Hyphomicrobium mainly occurred in anaerobic and anoxic reaction, and Sulfurovum was unique to the sulfur oxidation reaction, with a content of 10.20% and the ability to oxidize sulfide. The content of Nitrosomonas in aerobic reaction zone reached 36.75%, but no nitrifying bacteria were detected. The technology in this study, which used sulfate as the electron acceptor for the continuous biological removal of Cd²⁺, has future engineering application value for the treatment of wastewater containing low concentrations of Cd.