Up-concentration of organic matter from municipal wastewater by coagulation coupled with active coke adsorption to improve carbon capture and anaerobic methanogenesis efficiency

Abstract

Up-concentration of organic matter plays a crucial role in recovering carbon resources and energy from municipal wastewater, and the capture of dissolved organic matter during coagulation process is essential for enhancing carbon separation and recovery efficiency. In this study, we employed active coke adsorption combined with ferric chloride (FeCl₃) coagulation process to enhance organic matter capture efficiency from municipal wastewater. Subsequently, the anaerobic methanation performance and microbial mechanism of the resulting carbon-rich sludge were investigated. Results indicated that the combined process increased organic matter capture efficiency by 0.8 % – 29.2 % compared to single coagulation treatment. Prepositive active coke adsorption within the FeCl₃ coagulation process achieved superior carbon capture performance compared to synchronous and postpositive configurations. Optimal dosage for adsorption-coagulation process using FeCl₃ of 43.65 mg Fe/L and active coke of 7.6 mg/L was obtained by applying an integrative response surface methodology (RSM) coupled nonlinear programming approach under effluent COD constraint of 48 mg/L. The integrative optimization resulted in a 47.9 % cost reduction compared to the RSM optimized condition. Anaerobic experiments demonstrated that utilization of active coke adsorption boosted organic matter capture, resulting in a 22.1 % increase in methane yield (CH₄/m³ wastewater) compared to using coagulation alone. Microbial community structure analysis showed that active coke promoted enrichment of acetoclastic methanogen and electroactive microorganisms. These findings posed ideas and technical support for strengthening carbon separation and recovery efficiency from municipal wastewater.