Scaling salt removal by addition of inorganic particles

Reverse osmosis (RO) concentrates containing high amounts of dissolved salts and anti-scalants are commonly discharged directly. Considerable economic and environmental benefits could be achieved by extending current water recovery limits. One way for reuse of concentrates and thus increasing the water recovery is to recycle part of the brine concentrate to the feed, after precipitating the scaling salts such as CaSO₄/CaCO₃ held in solution by anti-scalants. In the present study, scaling salt removal was carried out from RO CaSO₄ concentrate in the presence of four anti-scalants via addition of six kinds of inorganic particles. Analyses of the kinetics of gypsum removal and the morphologies of CaSO₄ crystals were performed. The results show that the was effective for the removal of scaling salt. After the precipitation removal reactions, the test solutions reached thermodynamic equilibrium. Furthermore, the precipitated gypsum appeared shorter and broader crystal forms. The economic analysis shows the method is feasible.