A comparison of three treatment processes for emulsified rinsing wastewater using integrated LCA-AHP: From lab to pilot-scale

Emulsified rinsing wastewater from textile industry is difficult to treat due to its stable oil-in-water emulsion. To address the issues of high cost and suboptimal effluent quality in the flocculation-biotreatment process at a textile wastewater pretreatment station, this study systematically compared two improved schemes: enhanced pretreatment (demulsification-flocculation coupled with biotreatment) and enhanced biotreatment (carbon material enhanced anaerobic process). Key operational parameters were optimized through lab-scale experiments. Demulsifier E and biochar showed the best effect respectively. These parameters were validated in a 100-day, 1000 m 3 /d pilot-scale application. Two schemes both achieved better average effluent chemical oxygen demand (COD) than the original process. For comprehensive decision-making, an integrated life cycle assessment (LCA) combined analytic hierarchy process (AHP) model was developed, evaluating in economic, environmental, and technical effectiveness. LCA results indicated the biochar enhanced anaerobic process exhibited the lowest environmental impact, particularly in global warming potential (GWP). AHP weight revealed that technical effectiveness, especially COD removal efficiency, was the primary concern, resulting the selection on biochar enhanced anaerobic process. This study provides both a practical upgrade solution for industrial wastewater treatment plants and demonstrates the value of the LCA-AHP framework in guiding the green transformation of such processes.