Research progress on enhancing wastewater treatment performance in constructed wetlands with substrates in low−temperature environment

CW have been widely applied in the treatment of micro-polluted water and rural decentralized domestic sewage due to their low cost and environmental friendliness. However, the treatment performance of CW significantly declines in low-temperature environments, which becomes a key limiting factor for their widespread application. In a low-temperature environment, the process of substance transfer will slow down, the efficiency of some physical and chemical reactions will decrease, and the activity and metabolic rate of microorganisms will also decline. This paper summarizes the types and functions of natural minerals, industrial by-products, and artificial materials commonly used in CW, as well as the research progress on using substrates to enhance CW in low-temperature environments. Among them, artificial and modified materials can precisely design surface properties and electronic structures, significantly enhancing the adsorption capacity and catalytic activity under low temperatures; the combination of functionally complementary substrates will selectively enrich specific functional microorganisms while exerting their respective functions, promoting microbial diversity, and thereby enhancing the functional stability and treatment performance of CW in low-temperature environments. Appropriate substrate types and performance enhancement can not only maintain strong physical adsorption capacity in low-temperature environments but also effectively change the redox conditions through chemical reactions, effectively enhancing the activity and function of microorganisms in low-temperature environments, achieving the synergistic enhancement of system performance. However, current substrate materials still face issues such as economic efficiency, operational stability, and unclear mechanisms for micro-ecological regulation. This review, from the perspective of practical application, proposes to advance the development of CW technology in low-temperature environments from the four dimensions of "mechanism insight - material innovation - system design - engineering integration", providing theoretical basis and technical support for improving the treatment efficiency of CW in cold regions.