Bioretention–Cistern–Irrigation Treatment Train to Minimize Stormwater Runoff

Water quality of parking lot (∼1,858 m2) stormwater runoff and corresponding bioretention-treated effluent flow (collected in a cistern) were analyzed for total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), electrical conductivity (EC), copper (Cu), lead (Pb), and zinc (Zn). The novel system includes a standard bioretention facility underdrained to a cistern to store treated stormwater and pumped to a vegetable garden for irrigation. The site abstraction, average bioretention abstraction, and bowl volume were estimated to be 8,500, 4,378, and 895 L, respectively; this indicates that rain events of more than 0.45 cm are necessary to produce runoff and more than 0.75 cm will produce system overflow. Cistern water concentrations averaged (±1 SD) 0.17±0.04 mg/L TP, 1.08±0.53 mg/L TN, 0.11±0.02 mS/cm EC (nonwinter), 15.7±17.6 μg/L copper, and 12.2±6.3 μg/L zinc. All of these concentrations were lower than measured in tap water, indicating effective treatment by the system and that the cistern represented a good-quality water source for irrigation. However, more data for winter EC are required to address EC removal effectiveness of the treatment train system.