When conventional ozonation processes are replaced by a combination of ozone and hydrogen peroxide, bromate formation increases when the ozone residual is kept constant but decreases when the ozone dose is kept constant. Bromate formation in conventional ozonation and advanced oxidation processes combining ozone and hydrogen peroxide was investigated at five water treatment plants. Before ozonation, bromide concentrations ranged from 35 to 130 pg/L. Bromate formed during the ozonation step varied from <2 to 42 μg/L. In general, advanced oxidation leads to higher bromate concentrations when compared with a conventional ozonation process, if the same ozone residual is maintained for both processes. Lower concentrations result if the ozone dosage is kept constant and the hydrogen peroxide dosage is increased.

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The objective of the study was to determine the influence of chlorination by-products of naturally occuring nitrogenous organic compounds on tastes and odors in drinking waters. Amino acids, peptides and amino sugars have been chlorinated under various chlorine/nitrogen ratios. Six natural amino acids were shown to induce tastes and odors at concentrations in the range 10-20 µg/l after chlorination. A multicomponent mixture containing 2.5 µg/l each of these 6 amino acids consistently induced detectable odors after a contact time with chlorine of 2 hours. Investigation of the by-products indicated that the odors generated were systematically linked to the aliphatic aldehydes formed. The peptides investigated revealed varying degrees of odor formation potential, while the amino sugars did not impart any odor. Chlorinous odors occasionally detected during these experiments were thought to arise from the organic chloramines or other oxidation by-products.

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