Autotrophic denitrification in coking wastewater treatment systems: Comprehensive comparative study of full-scale...

The biological treatment of coking wastewater faces challenges due to high toxicity, high nitrogen loading, and excessive carbon demand. This study comprehensively investigated the pollutant removal performance, microbial community diversity, and metabolic functions of 14 full-scale coking wastewater treatment systems (CWWs) in China, aiming to explore pollutant removal mechanisms to reduce environmental impacts. The dominant functional microorganisms exhibit significant variations across different CWWs. The core autotrophic sulfur-oxidizing denitrifiers Thiobacillus and Arcobacter drive the sulfur-driven autotrophic denitrification process, leading to higher nitrogen removal in mixotrophic systems. Deterministic factors influence microbial community structures, which can enable targeted community structure regulation. Based on sulfide-based pollutants such as thiocyanates, the contribution of sulfur-driven autotrophic denitrification processes to CWWs was revealed. By optimizing the allocation of electron donors, the construction of mixotrophic nitrogen removal systems can improve nitrogen removal efficiency while reducing carbon inputs and greenhouse gas emissions.