Degradation and detoxification of microcystin-LR in drinking water bysequential use of UV and ozone

Microcystins (MCs) produced by cyanobacteria are strong hepatotoxins and classified as possible carcinogens. MCs pose aconsiderable threat to human health through tainted drinking and surface waters. Herein filtrated water from a waterworks in Harbin,China, was spiked with microcystin-LR (MC-LR) extracted from a toxic scum of microcystis aeruginosa, and the spiked sample waterswere treated using UV irradiation with consequent ozonation process (UV/O3), compared with ozonation at a dose range commonlyapplied in water treatment plants, UV irradiation at 254 nm and UV irradiation combined with ozonation (UV+O3), respectively. Theremaining of toxins were analyzed using high-performance liquid chromatography and also determined using a protein phosphatasetype 2A inhibition assay, which was utilized to evaluate the reduction in toxicity. Results indicated that in comparison to other threeprocesses (O3, UV, and UV+O3), UV/O3 process could e ectively decrease both the concentration and toxicity of MC-LR at 100 g/Llevel after 5 min UV irradiation with consequent 5 min ozonation at 0.2 mg/L (below 1 g/L ), while 0.5 mg/L ozone dose was requiredfor the level below 0.1 g/L. The addition of an UV treatment step to the existing treatment train may induce significant transformationof micropollutants and breaks down the natural organic matters into moieties unfavorable for ozone decomposition, stabilizing theozone residual. These findings suggested that sequential use of UV and ozone may be a suitable method for the removal of thesepotentially hazardous microcystins from drinking water.