Insights into enhanced constructed wetland for wastewater treatment: nitrogen removal and greenhouse gas emissions

In order to solve the problems of low removal rate of NO₃^-- N and increased N₂O emissions in sewage caused by the limitation of denitrification due to the lack of carbon source and other electronic donors in traditional constructed wetlands, enhanced technologies such as electrochemical enhancement, improved substrate, microbial enhancement and plant enhancement have emerged in recent years, but there is a lack of systematic summary of such technologies. Based on the statistics of relevant literatures at home and abroad in the past five years, this paper summarizes the nitrogen removal efficiency and mechanism of various types of enhanced constructed wetlands, such as electrochemical enhancement, improved substrate, plant enhancement and microbial enhancement, discusses the greenhouse gas emission laws and emission reduction mechanisms represented by CH₄ and N₂O in constructed wetlands, and evaluates their efficiency and application prospects in the treatment of low pollution water. It is found that various enhanced technologies can improve the nitrogen removal efficiency of constructed wetlands and reduce CH₄ and N₂O emissions from different paths, especially in the treatment of low pollution water. However, due to environmental conditions, the stability of various strengthening technologies is difficult to guarantee, and the actual engineering application still needs to be further optimized and verified.