Effect of ozone on algae as precursors for trihalomethane and haloacetic acid production

The effect of ozone on the trihalomethane (THM) and haloacetic acid (HAA) f ormation of two algae species was investigated. Scenedesmus quadricauda (gr een alga) and Cyclotella sp. (diatom) were cultured under controlled condit ions and harvested in the log or late log growth phase. Experiments examine d the formation of disinfection byproducts (DBPs) from the algal suspension s with and without preozonation. Preozonation with 1 mg/L increased chlorof orm formation from Scenedesmus by 17-44%. For Cyclotella, chloroform produc tion increased by 5-26% with 1 mg/L ozone and by 39-109% with 3 mg/L ozone. Chlorinated HAA yields were not significantly increased after 1 mg/L ozone but increased by 38-76% for Cyclotella after 3 mg/L ozone. As compared to other sources of organic matter, algae under bloom conditions may contribut e significantly to the DBP precursor pool. However, the majority of the DBP precursors (70%) were attributable to the cellular material, and thus remo val of algae cells from a drinking water supply prior to oxidation will sub stantially reduce algal precursor concentrations.