Photodecomposition Behaviors of Pesticides in the Source for Water Supply Using an Alumina Carrier-Titanium Dioxide Photocatalyst

The countermeasures against toxic substances or musty odor cause substances in the source for water supply have become a serious subject with the pollution of environmental waters (Coleman et al., 1980; Nakasugi, 1993; Tanada et al., 1995; U. S. EPA, 1993). For the purpose of the utilization of the photodecomposition method for the water purification at a water purification plant or a water purifier, we have investigated on the photodecomposition behaviors of organic pollutants (Matsuda et al., 2002; Okumura et al., 2003), total organic compounds (Tanizaki et al., 2005), formaldehyde (Tanizaki et al., 2005), total organic halides (Tanizaki et al., 2005), trihalomethanes (Tanizaki et al., 1997, 2005), geosmin (Okumura et al., 2004) and 2-methyl-iso-borneol (Okumura et al., 2004) using a titanium dioxide (TiO2) photocatalyst. Relatively high photodecomposition efficiencies were obtained for these substances. Pesticide is one of the toxic chemical substances polluting the source for water supply (Tanada et al., 1995), vegetables, fruits, etc (Ishikawa et al., 2004). Then, the residual pesticide in many kinds of food have already been regulated and the aiming standard values of 101 types of pesticide for tap water quality control were set up in 2003 (Ando, 2004). However, only 21 in 117 types of pesticide showed over 80% of removal ratio in the coagulation and sedimentation usually performed at a water purification plant (Ishikawa et al., 2006). Then, we investigated on the photodecomposition behaviors of the 5 types of pesticide which were largely used in Kitakyushu district. We have ever used silica gel having high decomposition efficiency as a carrier of TiO2 photocatalyst. However, a silica gel carrier was fragile. In addition, sufficient endurance of the carrier is demanded when the decomposition of chemicals in water and food or that disinfection using supersonic wave together is performed (Ishikawa et al., 2008). Then, we also investigated on the photodecomposition ability with an alumina carrier, which could stand against ultra violet (UV) light and water, instead of silica gel carrier.