Coagulation behaviors of new covalently bound hybrid coagulants (CBHyC) in surface water treatment

Abstract

Abstract While new coagulants are able to remove more contaminants and reach higher removal efficiency, basic coagulation performance, such as turbidity removal and floc settling, is also considered in the process evaluation. Here, we systematically evaluated the performance of a novel covalently-bound hybrid coagulant (CBHyC) in natural surface water coagulation using jar test. Size-exclusion chromatography coupled with online organic carbon detection (SEC-DOC), fluorescence excitation emission matrix (EEM), acid-base titration and zeta potential analysis were used to characterize the behaviors of CBHyC coagulation. Compared with metal-based coagulants, CBHyC has better settling properties and removes more turbidity. Across a range of dosages, the CBHyC formulation with higher zeta potential achieved better removal of natural organic matter (NOM) and resulted in less of a pH change. Total dissolved nitrogen decreased 37% with CBHyC coagulation. CBHyC can remove both low molecular weight (LMW) organics and high molecular weight components. The interaction between quaternary ammonium plus phenolic and carboxylic groups is likely responsible for the removal of LMW and nitrogenous organics, and thus CBHyC removed more NOM than conventional coagulants. In summary, CBHyC performs better than conventional coagulants for removing turbidity and NOM and also overcomes emerging needs to remove LMW and nitrogenous organics.