The photocatalytic removal of bacterial pollutants from drinking water

Abstract

Pathogens in drinking water supplies can be removed by sand filtration followed by chlorine or ozone disinfection. These processes reduce the possibility of any pathogens entering the drinking water distribution network. However, there is doubt about the ability of these methods to remove chlorine resistant microorganisms including protozoan oocysts. Concern has also been raised about the production of disinfection by-products following the chlorination process. Titanium dioxide (TiO 2) photocatalysis is a possible alternative/complementary drinking water treatment method. TiO 2 electrodes were prepared by the electrophoretic immobilisation of TiO 2 powder (Aldrich and Degussa P25). These electrodes were tested for their photocatalytic bactericidal efficiency. E. coli K12 was used as a model test organism. The rate of disinfection was greater for the P25 electrode compared to the Aldrich electrode under open circuit conditions. The application of an electrical bias to the working electrode increased the rate of disinfection by ∼40% for the P25 electrode and ∼80% for the Aldrich electrode. The effect of applied potential was more pronounced under conditions of high initial bacterial cell loading and high light intensities. Bacterial recovery did not occur up to 48 h after disinfection.