Optimisation of dual coagulation process for the removal of turbidity in source water using streaming potential

The charge at the surface of suspended particles and the degree of its neutralisation play an important role for achieving better turbidity removal efficiency in the coagulation process. Therefore, optimisation of the process critically requires continuous measurement or monitoring of surface charge. Streaming potential for this purpose can be considered as a good potential option in dual coagulation system. This study investigated factors that alter the streaming potential of source water, including pH, turbidity, humic acid concentration, inorganic coagulants, ionic strength, and polyelectrolyte concentrations. A range of dual coagulation systems were tested using the streaming potential to optimise coagulant doses., And jar test experiments were performed to estimate the extent of floc formation and turbidity reduction. Several inorganic and organic coagulants were combined in dual coagulation systems; Ferric chloride (FeCl₃), Titanium chloride (TiCl₄), and Aluminium chloride (AlCl₃), Non-ionic polyacrylamide (PAM) and anionic polyacrylamide (aPAM). Turbidity removal efficiencies ranged from 83% to 99%. Ti (IV) systems gave the most efficient removal, which was not improved by the addition of polymer. PAM and aPAM added to Al (III) and Fe (III) flocculant systems, did improve the total removal efficiency and the rate of removal, with the effect more pronounced for Fe (III). Overall, PAM yielded the best results, particularly in combination with Fe (III). The streaming potential proved to be an excellent measure of optimum coagulant dosing.