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EDM-ZLD optimization for brackish water brine treatment

From September 2015 to December 2016, EDM-ZLD performance was evaluated to treat brine from brackish water desalination. During this period, optimal conditions for EDM (current density and voltage applied) were defined to reach a concentration factor above 4 for multivalent ions in the two concentrate streams and a conductivity of 5 mS/cm for the dilutes to allow their discharge into the sewer. Once optimized, EDM allowed to recover 80% of water with an overall concentration factor of 4.6. To recover valuable compounds from the Na-mixed stream and the Cl-mixed stream and accomplish a ZLD process, technologies such as crystallization, evaporation and advanced solar evaporation have been applied. The overall EDM-ZLD process would allow to recover 90% of water. Per m3 of brine treated several valuable compounds have been recovered: around 1.7 kg of Na2SO4 (95% purity), 2.7 kg of mixed salts (Na2SO4 and NaCl), 6.3 kg of Mg(OH)2 (95% purity) and 17 kg of NaCl (93% purity). The energy consumption per m3 of Helios brine treated was on average 11±3 kWh. The energy consumption per m3 of concentrates was on average 0.14±0.05 kWh/kg TDS (Total Dissolved Solids).