Deciphering the water quality deterioration in isolated artificial landscape replenished with reclaimed water: Key driving factors and mechanism

Reclaimed water reuse is critical to alleviate urban water resources shortage. However, applying it to artificial landscape might pose ecological issues, and key factors driving water quality deterioration especially in isolated waters with weak self-purification capacity remains unclear. This study unveiled the relationship between water quality deterioration with dissolved organic matter (DOM), algal and bacterial communities in isolated artificial landscape replenished by reclaimed water. Results showed that the trophic level index was increased by 58.6-88.2% with increase in turbidity, chemical oxygen demand, and chlorophyll a after reclaimed water reuse. Carbon, nitrogen, phosphorus as key factors drove the deterioration of water quality. Fluorescence characteristics suggested that increased DOM was derived from endogenous microorganisms. The algae of Chlorelia , Scenedesmus , Ankistrodesmus and bacteria of Porphyrobacter , Fluviimonas , Rhodobacter were dominant contributors. Partial least squares path modeling revealed that bacteria were more sensitive to reclaimed water, while algal proliferation more likely induced water quality deterioration. These findings deepened our understanding on water quality deterioration process, and highlighted the superiority of monitoring algae when reusing reclaimed water in artificial landscapes. • Trophic level index increased by 58.6-88.2% after reclaimed water reuse. • The C, N, P in reclaimed water as key factors drove water quality deterioration. • Increased dissolved organic matter was derived from endogenous microorganisms. • Partial least squares path modeling revealed deterioration mechanisms. • Algae need priority control when reusing reclaimed water in artificial landscapes.