Enhanced degradation of phenols and quinoline in coal gasification wastewater by iron-carbon multiple micro-electric field coupled with anaerobic co-digestion

Coal gasification wastewater (CGW) has a complex composition and exhibits significant concentration and toxicity. In practical engineering, a single treatment technique may not always produce the best results. In this paper, iron-carbon multi-micro-electric field coupling anaerobic co-digestion treatment is adopted with synthetic CGW as the research object. By using single factor analysis and response surface methodology, the optimum operating conditions: the activated carbon/zero-valent iron (ZVI) (C/Fe) ratio of 2:1 and a carboxymethyl cellulose (CMC) concentration of 0.8 mg/L were achieved. According to the reactor's operation findings, methane production grew to 200 mL/d, and the average removal efficiencies of total phenol and quinoline could reach 52.8±5.6% and 94.9±6.8%, respectively, under optimal operating conditions. The iron-carbon multi-micro-electric field coupling anaerobic co-digestion can significantly lower the toxicity of CGW during optimal operation, according to an investigation of effluent toxicity. The microbial community in the granular sludge of the anaerobic system was analyzed using metagenomic sequencing technology. Direct interspecies electron transfer (DIET) was promoted by the coupling system with enriched electroactive bacteria like Syntrophorhabdus and Geobacter. This study can serve as a guide for engineering applications that promote anaerobic improved treatment of refractory wastewater.