Our flexible sulfate removal process consists of a sulfate precipitation stage at pH 11–13 using lime milk and aluminum, followed by a final neutralization stage using carbon dioxide. Gypsum precipitation can be included before the sulfate removal stage when required.
The process, built on easy-to-understand chemistry, can be applied to sulfate removal from gypsum saturated waters. Importantly, sulfate can be precipitated even when it is associated with highly soluble sodium and potassium sulfates. The sulfate concentration after treatment is typically 200–1000 mg/L. A level below 200 mg/L can be achieved with enhanced precipitation chemistry.
In addition to sulfate removal, the process includes advanced removal of metal impurities such as Ni, Cd, Cu, and Zn as metal hydroxides. The final product includes treated water with a low sulfate concentration for discharge or re-use, and stable, solid precipitate with a high buffer capacity.