The team led by Professor Guangxu Chen and Professor Guanglei Qiu of South China University of Technology (SCUT) published a paper titled Realizing the practical application of CO2 electroreduction (CO2RR) for urban wastewater denitrification in the top-tier journal Nature Water. Based on a detailed comparison of the CO2RR system and municipal wastewater denitrification, the team proposed a novel electrochemical–biological hybrid system that merges CO2 electrolysis with municipal wastewater denitrification.

In this hybrid system, the electrocatalytic reaction efficiently generates formate (formate‑e) in neutral electrolyte, which directly serves as both a carbon source and energy carrier for biological denitrification. The results shows that the system achieves an excellent nitrate nitrogen (NO3−-N) removal rate (~3.06 mg L-1h-1). Moreover, after long-term continuous operation of the tailored denitrification bioreactor, the formate-e displays high denitrification rate, surpassing that of acetate, widely used as a commercial carbon source. Further environmental and techno-economic analyses indicate that integrating this electrochemical–biological hybrid system with an electrochemical recovery and separation system can significantly lower the cost of the electrolyte, thereby paving the way for the large-scale application of the hybrid system. This research offers a novel approach for the coordinated development of CO2 mitigation and urban wastewater treatment and demonstrates the significant potential of directly applying electrochemical products in environmental governance. With the continuous optimization of engineering design, the system holds promise for achieving both technical and economic viability. More importantly, by recycling and utilizing CO2 released from sources including thermal power generation, sludge or waste incineration, and biological denitrification processes as reaction feedstock, the system is expected to achieve net-zero emissions and even carbon-negative emissions.