Feasibility analysis of reclaimed water reuse based on water quality data and microbial community structure study

The ecological recharge of urban landscapes with reclaimed water plays a crucial role in alleviating urban water shortage. In Yinchuan, we examined the effects of recharging urban rivers with either Yellow River or reclaimed water on the abundance and diversity of microbial communities. This study aimed to support the effective utilization of reclaimed water. We monitored six sites: three in the reclaimed water recharge area (Lucaowa inlet (ZLJ), Lucaowa channel (ZLH), and Lucaowa outlet (ZLC)) and three in the Yellow River water recharge area (Ningcheng lock (FNCZ), Qingfengjie (FQFJ), and Laifosi (FLFS)). Various indicators (pH, turbidity, temperature (T), dissolved oxygen (DO), electrical conductivity (EC), chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH₃-N), and nitrate nitrogen (NO₃-N)) were used to assess the water quality. The microbial community abundance and diversity were evaluated using 16S rRNA high-throughput sequencing. The results indicated that throughout the monitoring period, the reclaimed water recharge area exhibited increased water transparency and greater microbial community abundance and diversity than the Yellow River water recharge area. However, the reclaimed water recharge area also showed significantly higher levels of nitrogen, phosphorus, organic matter, and electrical conductivity, along with an increase in Firmicutes. Seasonal changes significantly influenced water quality factors, significantly affecting Cyanobacteria and Campylobacter populations, as demonstrated by RDA analysis, which showed a close relationship between microbial communities and environmental factors. Further comparative analysis revealed that erythrocytic bacteria were predominant in the reclaimed water recharge area, whereas Actinobacteria, Planktonia, and Aspergillus spp. were more significant in the Yellow River water recharge area. Predictive analysis of microbial functions suggested that carbon and nitrogen cycle-related functions were more abundant in the reclaimed water recharge area, indicating that reclaimed water recharge could improve the self-purification capacity of the water body.