Solar Photocatalysis Using Fixed-Film TiO_2 for Microcystins from Colonial Microcystis aeruginosa

摘要

Microcystins (MCs) are endotoxins produced by cyanobacteria in freshwaters globally. With known potential for human health risks, rapid and effective treatment methods are needed for MCs. Previous studies have shown photocatalysis can achieve rapid half-lives with UV lamps and slurries of TiO2. In this experiment, rates and extents of solar photocatalysis of MCs were measured using bench-scale reactors with fixed films of TiO2 for solutions with a range of cellular:aqueous MC ratios. Since cellular MCs can be removed physically, photocatalysis rates were measured following sand filtration to discern the extent of MC removal post-filtration. Since UV energy drives photocatalysis using TiO2, rates of removal were calculated as a function of cumulative UV insolation and time. For water containing 10% aqueous MC, filtration removed 90% of total MC, and the subsequent photocatalysis half-life was 0.37 MJ/m(2) (or 111 min). For water with similar to 50% aqueous MCs, filtration removed 52% of the total MCs, and the average half-life for photocatalysis was 0.38 MJ/m(2) (or 138 min). For the 90% aqueous MC treatment, filtration removed 0% MCs, and the photocatalysis half-life for MCs was 0.37 MJ/m(2) (or 135 min). Previous studies have used clarified waters; however, results from this study are likely representative of scenarios with waters containing confounding water characteristics and use of solar light for UV, as anticipated in developing countries with less advanced water treatment methods. Photocatalysis is a rapid and effective process for decreasing concentrations of MCs and could be useful for mitigating risks from MC exposures in drinking water.