Hi Tanvi:Ferric salts are ...

Hi Tanvi: Ferric salts are most suitable because their charge is such that they do not create high potential for accumulation on the membrane elements. Most membrane elements have slightly negative charge and if we use coagulants other than ferric salts (i.e., poly-aluminum chloride, aluminum sulfate) these coagulants have charge opposite to the charge of the RO membranes and they will accumulate on the RO membrane elements and can cause irreversible fouling. Flocculants are not commonly used for seawater pretreatment because in most cases they can cause more trouble than to provide enhanced solids removal by granular media filtration. Membrane ultrafiltration and microfiltration do not require the use of any coagulants and flocculants.