Abstract
Natural water quality became worse these days by producing more pollutants than the amounts of decomposition in nature by primary decomposers. So, photocatalyst was intended to improve the environmenal water quality. However, photocatalyst was known to act both the oxidative decomposition of pollutants as well as primary decomposers. In order to know whether photocatalyst can contribute to the net result for the improvement of environmental water quality or not, phtocatalyst was applied to model polluted water. The rate of purification was measured by the rate of consumption of dissolved oxygen. When photocatalyst was applied, dissolved oxygen was consumed 5.7 times faster under bright solar irradiation, 3.3 times faster at twilight time, and 1.5 times faster even at night, than in model environmental polluted water without photocatalyst. These results show that photocatalyst can improve polluted water efficiently, if water can supply enough air, even in the presence of primary decomposers in both day and night.
