Optimized multi-stage baffle design for enhanced pollutant interception in rainwater harvesting systems

Rainwater, as an unconventional water resource, is crucial in mitigating the water resource crisis. Most rainwater harvesting (RWH) systems feature a simple design, which often results in pollutant accumulation at the bottom of the tank, significantly impacting the quality of reused water. This study introduces a novel RWH system utilizing a multi-stage baffle for the separation of sedimentation and clarification zones. Computational Fluid Dynamics (CFD) is employed to optimize and simulate the energy dissipation efficiency across various inlet and baffle configurations within the RWH system. The study examines optimal tank structural conditions for effective pollutant interception. Simulation results indicate that the proposed RWH system demonstrates superior pollutant retention performance, achieving maximum interception efficiency for suspended solids (SS) at low flow rates (0.03 m/s) and high concentrations (492.8 mg/L). A physical model of the RWH system was constructed, and experimental results indicated that the system could intercept over 80 % of pollutants and reduce sediment disturbance during continuous storage, thereby enhancing the quality of rainwater for reuse.