Industrial Water Treatment
The treatment of fluoride bearing effluents is an area of increasing concern, as fluoride content in drinking water has become a part of the public and regulatory agenda. Industrial operations, such as petroleum refineries, aluminum smelters, and semi-conductor production facilities, generate effluents that are high in fluoride content and require treatment prior to discharge. Calcium Chloride can be used effectively in the removal of fluoride. The level of residual fluoride after treatment will depend on processing conditions but is typically in the range 10-100 mg/l. Fluoride is chemically converted to insoluble calcium fluoride, CaF2, in the process and can be removed by solid/liquid separation techniques.
Lowering the level of phosphate in industrial waste waters is necessary e.g. in order to mitigate eutrophication in lakes, rivers and coastal waters. Phosphate emitting industry includes e.g. fertilizers and chemicals. Calcium Chloride is effective in reducing phosphate by precipitating various forms of calcium phosphates. After removal of these solids, they can in some cases be re-used or sold.
Calcium Chloride can be used for removal of the bulk of sulfates in concentrated streams. After precipitation of sulfates as solid gypsum, the latter can be filtered off and sold or deposited. In some cases a polishing step is needed to achieve the desired concentrations in the effluent and this might be performed by e.g. ion-exchange.