Evaluation of Quantity and Quality of Reject Water from Desalination Plants in Saveh City and Providing the Necessary Solutions

Abstract Aim: The concentrate stream or saline reject water from reverse osmosis plants with high dissolved solid provides an environmental problem. In the present work, the quantity and quality of saline reject water from desalination plants was evaluated and its effect on the wastewater treatment plant (WWTP) of Saveh city was assessed. Methods: The random sampling of raw feed water and reject water of desalination plant was conducted in duplicate and subjected to total dissolved solids (TDS), electrical conductivity, total hardness, pH, and residual chlorine analysis. Results: The results showed that the value of TDS in the raw feed water, municipal wastewater, reject water in the household treatment system, and centralized RO plant in Saveh was 1732 mg/L, 2220 mg/L, 2408 mg/L, and 3315 mg/L, respectively. The quantity of reject water was 2238.5 m 3 /day and when it was mixed by the feed wastewater to the WWTP with the capacity of 4000 m 3 /day, the TDS content reduced from 2220 to 2441 mg/L. By introducing saline wastewater into the Saveh WWTP, TDS increased by 1.6%. Overall, the TDS of effluent wastewater of the Saveh WWTP was reached 2257 mg/L with a total capacity of 35,000 m 3 /day. Conclusion: The amount of recoverable salt from saline wastewater is about 2.794 tons/ day. Transfer of saline reject water to Saveh WWTP or salt recovery to produce sandsalt can be proposed as an effective solution for the management of saline reject water.