Which coagulant is commonly used upstream of demineralization or reverse osmosis?

Aluminium sulphate is commonly used as a coagulant in various water treatment processes, particularly upstream of demineralization or reverse osmosis systems. The primary purpose of using aluminium sulphate is to facilitate the removal of suspended solids and colloidal materials from water. When added to water, aluminium sulphate reacts with the impurities to form larger aggregates, or flocs, that can be easily removed through sedimentation or filtration.

This flocculation process significantly improves the efficiency and effectiveness of downstream processes such as demineralization and reverse osmosis. By reducing the turbidity and particle load in the water, aluminium sulphate helps alleviate fouling and scaling issues that could negatively impact the performance of membrane systems. As a result, using aluminium sulphate pre-treatment enhances the overall quality of the water prior to its treatment by these more advanced purification technologies.

Other coagulants listed, such as sodium chloride, calcium carbonate, and ferrous sulphate, serve different purposes in water treatment and may not be as effective in preparing water for demineralization or reverse osmosis processes. Sodium chloride primarily functions as a source of chlorine or for softening, calcium carbonate is often used for pH adjustment or hardness control, and ferrous sulphate