Water Treatment > Quality Water Solutions > FAQ > What are the best applications for alum, PACl and other coagulants?

Alum, the most widely used potable water coagulant, is used to clarify raw water, especially where water quality is highly variable. It is also applied to remove phosphorus and color and treat lagoons and reservoirs.

PACl is used for clarification, to enhance turbidity removal and to remove phosphorous. It is especially useful with colder source waters. Other major benefits it offers include reduced residuals and less alkali adjustment.

Iron salts (i.e., ferric chloride and ferric sulfate) are used to deal with specific water problems, such as partial softening, well-buffered systems and where the potential color of the effluent and the potential risk of system corrosion is not a problem.

Sodium aluminate is a costly material and so is generally applied in small doses in water softening, where the sulfate or chloride ion in other coagulants would be undesirable, in very soft or low pH water. It is also used as a supplement to alum.

Polyelectrolyte coagulants, which are synthetic organic polymers, act as either electrolytes (to neutralize electric charge), as flocculants (to agglomerate the neutralized material) or as both. They are used to improve the action of alum and iron compounds and in sludge dewatering.