A practical study on the near-zero discharge of rainwater and the collaborative treatment and regeneration of rainwater and sewage

Non -conventional water recovery, recycling, and reuse have been considered imperative approaches to addressing water scarcity in China. The objective of this study was to evaluate the technical and economic feasibility of Water Reclamation Plants (WRP) based on an anaerobic-anoxic-oxic membrane bioreactor (A 2 O- MBR) system for unconventional water resource treatment and reuse in towns (domestic sewage and rainwater). Rainwater is collected and stored in the rainwater reservoir through the rainwater pipe network, and then transported to the WRP for treatment and reuse through the rainwater reuse pumping station during the peak water demand period. During a year of operation and evaluation process, a total of 610,000 cubic meters of rainwater were reused, accounting for 10.4 % of the treated wastewater. In the A 2 O-MBR operation, the average effluent concentrations for COD (chemical oxygen demand), NH 4 + -N (ammonium), TN (total nitrogen), and TP (total phosphorus) were 14.23 +/- 4.07 mg/L, 0.22 +/- 0.26 mg/L, 11.97 +/- 1.54 mg/L, and 0.13 +/- 0.09 mg/L, respectively. The effluent quality met standards suitable for reuse in industrial cooling water or for direct discharge. The WRP demonstrates a positive financial outlook, with total capital and operating costs totaling 0.16 $/m 3 . A comprehensive cost -benefit analysis indicates a positive net present value for the WRP, and the estimated annualized net profit is 0.024 $/m 3 . This research has achieved near -zero discharge of wastewater and effective allocation of rainwater resources across time and space.