[Advances in stress response mechanisms and wastewater treatment application of cadmium-tolerant denitrifying...

Industrial wastewater from battery manufacturing, metal smelting, and electroplating often contains high concentrations of cadmium and nitrogen, resulting in cadmium-nitrogen combined pollution. Conventional physicochemical methods for simultaneous removal of cadmium and nitrogen face limitations such as complex processes, high energy consumption, and risks of secondary pollution. In contrast, using cadmium-tolerant denitrifying microbes, which achieve synergistic removal of cadmium and nitrogen through adsorption, biomineralization, and other pathways, offers advantages of low energy consumption and high efficiency. In this review, we summarize the classification and denitrification characteristics of cadmium-tolerant denitrifying microbes, with a focus on the cadmium tolerance mechanisms and nitrogen removal performance of Pseudomonas as a representative microbial group. We analyze the inhibitory effects of cadmium on denitrification, explore the underlying molecular mechanisms, and summarize microbial response mechanisms and cadmium removal pathways under cadmium stress. In addition, we review the advances in the application of functional bacterial strains in various reactor systems for synergistic cadmium and nitrogen removal, and reviews the achievements in enhancing removal efficiency and system stability through biomineralization and carrier optimization. Finally, we discuss current challenges and limitations and makes an outlook on the future research directions, aiming to provide theoretical and practical insights for the bioremediation of wastewater co-contaminated with cadmium and nitrogen.