Strong oxidants are widely used in drinking water treatment for the purpose of controlling biological growths, improving the performance of subsequent treatment processes and assisting in the removal of metals and trace organic compounds. The choice of an oxidant depends on many factors, but one of the most important is its effect on the level of disinfection byproducts in the finished water. Some oxidants will produce halogenated DBPs directly, but all will have some impact on DBP precursors that becomes apparent when the water is subject to final chlorination. In this presentation we report on a series of studies intended to directly compare the impacts of ferrate, chlorine dioxide, ozone and ozone/peroxide on DBP precursors in two contrasting waters. Among the DBPs explored are the trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles, haloketones, and chloropicrin. These were measured in the presence of low and high bromide concentrations. In addition, three different free chlorine contact times were used, effectively separating precursors into fast, medium and slow acting fractions. All oxidants showed similar trends in their tendency to reduce or increase the concentration of DBP precursors. However, the quantitative impacts when normalized to the oxidant dose were different for the different oxidant-DBP combinations. Effectiveness of pre-oxidation often showed greater precursor destruction for the fast-acting precursor as compared to the slower ones.

Relative effectiveness of ferrate, chlorine dioxide, zone and peroxone for control of disinfection byproduct precursors

253rd National Meeting (2017)

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