For the backwash process, the treated effluent from the storage tank (305 gallons) was
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injected through side valves (2 ft from the bottom of the reactor) and underdrain pipes, and evenly distributed over the bottom of the SGBR as shown in Figure 3−1. Approximately, 4.7% of the total volume of treated wastewater was used for backwashing. The backwashed water was discharged into the main influent channel of the plant.