Enhanced removal of dichloroacetonitrile from drinking water by the combination of solar-photocatalysis and ozonation

• Photocatalytic ozonation removes dichloroacetonitrile at the highest rate.
• The operating parameters were optimized for photocatalytic ozonation.
• Solar photocatalytic ozonation provides complete removal of dichloroacetonitrile.
• Solar photocatalytic ozonation has higher energy efficiencies than other systems.

In this study, the photocatalytic ozonation process using either UV lamps with a wavelength close to a solar wavelength (UVsolar) or natural solar light was established to study the effects of the major operating parameters on the removal of a toxic disinfection by-product (DBP), dichloroacetonitrile (DCAN), from drinking water. Based on the test results of a bench system, the UVsolar/TiO2/O3 process had the highest DCAN-removal rate among the advanced oxidation processes (AOPs). The optimal TiO2 and ozone doses were 1 g L−1 and 1.13 g L−1 h−1, respectively, while room temperature (20 °C) produced the highest rate constant in the kinetic tests. The kinetic rate constants linearly increased when the UVsolar intensity increased in the range 4.6–25 W m−2; however, it increased less at intensities higher than 25 W m−2. The test results of the outdoor system showed that the solar/TiO2/O3 process provided complete removal of DCAN that was two times faster and had about 4.6 times higher energy efficiency than with solar/TiO2. As a green oxidation technique, solar photocatalytic ozonation could be a good alternative for treating recalcitrant and toxic organic pollutants, because it has high oxidation potential and low energy consumption compared to conventional AOPs.