Overall performance and microbial community analysis of a full-scale aerobic cold-rolling emulsion wastewater (CREW) treatment system

Abstract

Cold-rolling emulsion wastewater (CREW) is an important type of wastewater generated from steel cold-rolling processes. In this study, for the first time, a full-scale aerobic bioreactor was studied to treat CREW. The consecutive 1-year field data showed that the average removal rate of total oil, TOC and COD reached 75.2%, 83% and 81%, respectively. The results of high-throughput sequencing demonstrated that the dominant phyla were Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes, consistent with other aerobic biochemical treatment systems in general, which ensured good adaptability of such bio-community to treat CREW. The average relative abundance of one dominant class, Alphaproteobacteria, was slightly higher than that of Betaproteobacteria, which is a unique phenomenon of the CREW treatment process and is different from most of the oil-containing wastewater processes. Combined with the GC×GC-TOF MS analysis of the influent and effluent, this phenomenon was hypothesized to be driven by the presence of phenols and was discussed in detail using the redundancy analysis, as well as the function and classification of dominant bacteria at genus level.