Identification of microbial communities and functional genes in an anaerobic-anoxic-oxic (A2O) process in responding to the iron-carbon micro-electrolysis (ICME) pre-treatment of electroplating wastewater based on high-throughput sequencing

Industrial wastewater contains high concentrations of refractory organic carbons, resulting in a low biodegradability difficult for the following biological treatments. The iron-carbon micro-electrolysis (ICME) was developed to break down the larger organic molecules and enhance the biodegradability. Previous ICME pretreatment coupling studies focused primarily on pharmaceutical, dye, and medical wastewater. In this study, the ICME was applied to treat the electroplating wastewater with surfactants, followed by an anaerobic-anoxic-oxic (A²O) biological process. When the ratio of the ICME-treated wastewater was low (10 %), the strike on nutrient removal efficiency (chemical oxidation demand, ammonia, total nitrogen, and total phosphate) was almost negligible. With the increase of ICME-treated wastewater up to 50 %, the removal efficiency gradually decreased, but the effluent water quality still met the discharge standard. Meanwhile, a shift of microbial communities in the three zones was also observed after the 50-day incubation. The abundance of Hydrogenophaga, Chitinophagaceae, and Lentimicrobiaceae all increased, which may be responsible for the degradation of refractory organics in the oxic and anaerobic zones. The functional gene analysis indicated that the adaptation of microbial communities was probably related to cell-to-cell communications and the transportation of molecules across the cell membrane. The microbial community and functional gene analysis revealed the adaptation of the microorganisms to the industrial wastewater. This study provides new insights into the ICME to enhance the biodegradability of electroplating wastewater for A²O treatment.