Research progress on environmental and ecological impacts of wastewater treatment plant reclaimed water discharge and reuse

Reclaimed water from sewage treatment plants is a valuable water resource, and reclaimed water reuse can not only alleviate the problem of water shortage but also improve water resource utilization. Although the reclaimed water from sewage treatment plants can meet the relevant water quality standards, it still contains more nutrients, salts, organic matter and heavy metals, which is an important source of pollution in rivers and lakes, and poses potential risks to the ecological environment and human health through the recharge of rivers and lakes and agricultural irrigation. The effects of reclaimed water from sewage treatment plants reuse on the river water environment, water ecology, soil physical and chemical properties, soil microbial community, and crop yield and quality when it was reused for ecological water replenishment of rivers and lakes and agricultural irrigation were reviewed. The main conclusions were as follows: 1) Reclaimed water replenishment in rivers could improve the quality of river water environment and enhance the self-purification capacity of water bodies. 2) Reclaimed water irrigation could effectively reduce the application of fertilizer, increase soil nutrients and improve soil fertility. 3) Long-term reclaimed water irrigation could increase soil microbial biomass and activity and change the structure and function of microbial communities. 4) The nutrients rich in reclaimed water could provide crops with nutrients needed for growth and promote the growth and yield of crops, but excessive supply of nutrients should be avoided. In the context of the current increasing scarcity of water resources, reclaimed water had great potential for utilization, but its environmental risks should be fully assessed, and corresponding precautions should be taken to use reclaimed water safely and efficiently.