Impact of pre-ozonation on the formation of haloacetic acids and trihalomathanes from algae cells and extracellular organic matter

This research examined the roles that algae cells and extracellular organic matter (EOM) played as sources of trihalomethanes (THMs) and haloacetic acids (HAAs) precursors and the effect of pre-ozonation on THM and HAA precursors' removal by the following coagulation process. The results show that the main trihalomethanes from both algae cells and EOM are chloroform and that the main haloacetic acids are dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), but distribution of specific HAAs and THMs from algae cells and EOM are greatly different. HAAFP from both algae cells and EOM are bigger than THMFP. The major HAAs from algae cells is DCAA, while that from EOM is TCAA. HAAFP from EOM is reduced by pre-ozonation; furthermore, low dosage and long pre-ozonation time is more beneficial to the control of HAAFP from EOM effectively, while THMFP is increased by pre-ozonation. At the same time, both HAAFP and THMFP from algae cells are significantly increased by pre-ozonation and this increase is almost a linear function of pre-ozonation time.