Comparable Evaluation of Iron‐based Coagulants for the Treatment of Surface Water and of Contaminated Tap Water

The aim of this study was to investigate the efficiency of various commercially‐available coagulants based on iron, such as ferric or ferrous salts, or polyferric sulfate (PFS), for the treatment of surface (river) water in order to become drinkable. These coagulants were evaluated, considering the removal of suspended solids (SS), of natural organic matter (NOM) and of the residual iron concentration. Furthermore, the kinetics of flocculation was studied by using a Photometric Dispersion Analyzer (PDA), comparing the different flocculation rates. The optimum operational conditions, i.e. coagulant dosage, pH value, duration, and intensity of (initial) rapid‐mixing rate, were determined for the examined cases. The results indicated that certain trivalent iron coagulants [Ferrisol‐123 (based on FeClSO4) – Ferrisol‐Cl‐130 (based on FeCl3)] showed higher efficiency, than the divalent [Ferrosol‐9 (based on a mixture of FeSO4 and FeCl2), presenting higher SS and NOM removal, higher flocculation rates, and lower residual iron concentration.