Impact of catalytic ozonation with ferric hydroxide on HAAs formation potential of a filtered surface water

Formation potential of five haloacetic acids (HAA5FP) of a filtered surface water was studied after ozonation alone and catalytic ozonation with a ferric hydroxide (FeOOH). Factors studied were oxidation time, bromide, pH, bicarbonate alkalinity, and ozone dosages. The haloacetic acids detected were dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and dibromoacetic acid (DBAA) when bromide existed. The catalytic ozonation caused a reduction of HAA5FP of the non-bromide containing water from 9.5% to 18.3% compared to that of ozonation in 5~20 minutes. Incremental addition of bromide led to a much lower HAA5FP after catalytic ozonation than that after ozonation. HAA5FP of the water at neutral pH was higher than that at acidic and basic conditions. Catalytic ozonation showed a most advantageous potential in controlling HAA5FP over ozonation at neutral pH. The HAA5FP decreased as bicarbonate concentration increased, and the disparity between ozonation and catalytic ozonation was also reduced. The HAA5FP after catalytic ozonation was 11.2% to 28.0% lower than that after ozonation while the ratio of O₃/TOC ranging from 0.45 to 1.43. The effect of catalytic ozonation on HAA5FP of the water is closely related to its enhanced generation of hydroxyl radicals in catalytic process.