Operational characteristics and life cycle assessment of full-scale bioaugmented coking wastewater treatment system:...

Coking wastewater (CWW) is characterized by high toxicity, poor biodegradability, and significant compositional fluctuations, which pose substantial challenges to the stable, long-term operation of conventional A/O/O treatment processes. In this study, a full-scale bioaugmented CWW treatment system was implemented at a large coking plant, and its treatment efficiency, microbial community succession, and environmental impacts were comprehensively investigated. The results demonstrated that, even under highly toxic and unstable influent conditions, the biological treatment unit achieved COD and NH₄⁺-N removal efficiencies of up to 97 % and 99 %, respectively. In comparison, the advanced treatment unit achieved maximum removal efficiencies of 75 % and 85 %, respectively. The final effluent maintained COD concentrations below 120 mg/L and NH₄⁺-N concentrations below 5 mg/L, with the lowest recorded values reaching 64 mg/L and undetectable levels of NH₄⁺-N. High-throughput 16S rRNA sequencing revealed that bioaugmentation promoted microbial community reorganization and enriched several key functional genera, including Thiobacillus, Nitrosomonas, Limnobacter, and Denitratisoma. Life cycle assessment (LCA) further showed that the biological and advanced treatment units were the primary sources of environmental impacts, contributing nearly 90 % of the total burden. This study offers practical insights into the stable and low-carbon treatment of CWW and provides guidance for optimizing systems for highly toxic industrial wastewater.