Study on the treatment of tempering lubricant wastewater in steel industry by anaerobic/aerobic process

Abstract

Tempering lubricant wastewater (TLW) is alkaline oily wastewater produced in the cold rolling process of steel, which has multiple contaminants in high concentration including complex organic components, oil, and surfactants. And the ratio of BOD/COD was only around 0.1. This study evaluated the performance of the combined anaerobic/aerobic (A/O) batch reactors for treating real TLW under different organic load rates (OLRs). The results of 140 days monitoring indicated that A/O process was effective to TLW treatment, the removal efficiencies of TOC and total nitrogen (TN) reached 86.2% and 81.5% when OLR was 5 g-COD/L/d. It was also found that OLR had much effect on the microorganism's distribution in the anaerobic reactor. The abundance of Firmicutes increasing at higher OLR (over 5 g-COD/L/d) caused volatile fatty acids accumulation during anaerobic treatment and then inhibited TLW degradation, especially for TOC removal. Based on the sludge characters and microbial community analyses, aerobic granule sludge formed in aerobic reactor contributed to TN removal by simultaneous nitrification and denitrification. Functional genes were also detected through real-time quantitative PCR analysis.