Titanium nitride (TiN) is a biocompatible material and has very low electrical resistance. Electrochemical control of pathogenic microbes derived from a drinking water distribution system was investigated using a TiN electrode. When a potential of 1.2 V vs saturated calomel electrode (SCE) was applied, the survival ratio of microorganisms decreased to below 40%. Changes in pH were not observed at 1.2 V vs SCE. Also, by applying -0.6 V vs SCE for 30 min, 69% of cells on the electrode surface were detached by the electrostatic repulsion. Therefore, an electrochemical disinfection reactor using a TiN mesh as the working electrode and the counter electrode was constructed. The drinking water containing mean viable cell concentration of 73 cells/ml was continuously passed through the reactor at a flow rate of 15 ml/min. The viable cell concentration in treated water decreased to below 5 cells/ml. When no potential was applied, cell concentration in treated water gradually increased after 200 h of reactor operation. In contrast, when alternating potentials of 1.2 and -0.6 V vs silver/silver chloride (Ag/AgCl) were applied to the TiN mesh working electrode, the viable cell concentration remained below 100 cells/ml during a 440 h operation. The reactor for drinking water disinfection incorporated with the TiN mesh electrode worked effectively by applying alternating potentials of 1.2 and -0.6 V vs Ag/AgCl. (C) 2000 Elsevier Science Ltd.
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