Optimizing roof-harvested rainwater storage: Impact of dissolved oxygen regime on self-purification and quality dynamics

Roof-harvested rainwater presents a promising, unconventional, and sustainable water resource for both potable and non-potable uses. However, there is a significant gap in understanding the quality evolution of stored rainwater under varying dissolved oxygen conditions and its suitability for various applications. This study investigated the evolution of rainwater quality under three distinct storage conditions: aerated, open, and sealed. Additionally, the microbial community and metabolic functions were analyzed to systematically evaluate the self-purification performance over long-term storage durations. The results indicate that aerated storage enhances microbial carbon metabolism, leading to a degradation rate of 54.4%. Sealed and open storage conditions exhibited primary organic matter degradation at the early and late stages, respectively. Open storage displayed the highest accumulation of NO3-N (5.23 mg/L), indicating limited denitrification activity. In contrast, sealed storage demonstrated robust self-purification performance, evidenced by a comprehensive coefficient of 15.83 calculated by Streeter-Phelps model. Proteobacteria emerged as the dominant phylum in stored rainwater, accounting for up to 79% relative abundance. These findings provide valuable insights into the mechanisms governing rainwater quality changes under various storage conditions, emphasizing the necessity for developing effective management strategies for the storage and utilization of roof-harvested rainwater.