Anionic polymer compound bioflocculant as a coagulant aid with aluminum sulfate and titanium tetrachloride

The objectives of this study are to investigate the impacts of anionic polymer compound bioflocculant (CBF) as a coagulant aid on coagulation performance and floc characteristics with titanium tetrachloride (TiCl4) and aluminum sulfate (Al2(SO4)3). The effect of dosing sequence was also investigated. Floc size, breakage, regrowth and floc fractal dimension were examined using a laser diffraction instrument. The results showed that CBF with TiCl4 or Al2(SO4)3 coagulants exhibited synergistic effects by promoting dissolved organic carbon (DOC) removal. For both TiCl4 and Al2(SO4)3, the floc recoverability was improved by CBF addition, and the flocs formed by TiCl4 and the corresponding dual-coagulants showed weaker recovery ability than those by Al2(SO4)3 and the corresponding dual-coagulants. Fractal dimension analysis demonstrated that the floc fractal dimension values increased with the increasing coagulant dose. The effect of CBF on fractal dimension of the flocs generated by TiCl4 was different from that of Al2(SO4)3.