Photocatalysis by TiO2 is a new technology which can treat water without adding any chemicals. In this research, the disinfections of three microorganisms such as bacteriophage Qβ, E. coli and Cryptosporidium parvum were investigated. An immobilized TiO2 reactor was used and UV lamp and Black light (BL) lamp were used as light source. The intensity of each lamp was set up to equalize the photocatalysis efficiency determined by the decomposition rate of Methylene Blue. The additive effect of TiO2 to inactivation did not appear in the E. coli experiments with UV and BL irradiation or in the experiment with UV. In these three cases, light irradiation gave a high germicidal effect and the addition of inactivation by photocatalysis was relatively too small to be significant. In the experiment with BL and in the Cryptosporidium experiment with UV and BL, the additive effect by TiO2 could be seen clearly because these microorganisms were resistant to light irradiation in these cases. In spite of setting equal photocatalysis efficiency in both lamp reactors, UV photocatalytic inactivation of Cryptosporidium was much faster than BL. It is assumed that UV and photocatalysis enhanced each other.

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