A cationic polymer enhanced PAC for the removal of dissolved aquatic organic carbon and organic nitrogen from surface waters

Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are important components of the aquatic environment and may produce harmful disinfection by-products through chlorination associated with water treatment processes. Coagulation-flocculation is the key unit in the pre-treatment of drinking water but deals poorly with DON. Despite the increase in nitrogen pollution of the environment, little attention has been paid to the removal of DON. We present a study to investigate the enhancement of poly aluminum chloride (PAC) using a cationic polymer for the removal of both DON and DOC. The cationic dimethyl diallyl ammonium chloride (PDMDAAC) polymer was hybridised with PAC to remove DON and DOC. The results showed that the PDMDAAC increased the charge neutralization capacity of PAC and floc aggregation thereby increasing the settling efficiency of flocs; the PDMDAAC increased the amount of colloidal species in PAC, which was beneficial to the formation of adsorption-bridging; with the increase of pH, a greater proportion of colloidal adsorption sites were used in the removal of DON; the DOC, DON and turbidity removal were dependent on multiple interactions through charge neutralization, adsorption-bridging and floc sweeping. However, DOC and DON removal were primarily determined by adsorption-bridging and floc sweeping, while turbidity removal was mainly dependent on charge neutralization.