Coagulation of surface waters with pre-hydrolysed iron salts

The use of prehydrolized iron salts based coagulants as substitutes for aluminium based prehydrolized compounds for drinking water is a feasible alternative given the high removal efficiency of natural organic matter when treating water coming from various sources. By using prehydrolized coagulants, the removal efficiencies of the dissolved organic matter, (DOC), are 15-24% higher than in the case of using aluminium salts. On the other hand, as part of these experiments, the residual total organic carbon (TOC), is by 16.5% lower when prehydrolized iron based salts are used. Each situation is assessed in order to set up the specific working conditions when substitution of iron salts for aluminum compounds is suitable given the fact that even extremely small amounts of residual iron can colour the treated water.