The presence of algae in a drinking water source can have a significant impact on the treatment of that water. Algae and their extracellular organic matter can be precursors for disinfection by-product (DBP) formation which is of concern for treatment plants that employ pre-chlorination. This research examined the DBP formation of suspensions of Scenedesmus quadricauda, a green alga, and the effect of ozonation on that formation. Trihalomethane formation potential (THMFP) was found to increase by 10% to 30% when preozonation was applied versus non-ozonated samples. A slight increase in haloacetic acid (HAA) formation was also observed in the ozonated samples. Ozonation caused an increase in the dissolved organic carbon content of the algal suspension, thereby increasing the concentration of precursors. The alkalinity of the water did not significantly affect the formation potential of either THMs or HAAs.

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