The photocatalytic disinfection of Escherichia coli, a pathogenic micro-organism. was investigated. An aqueous suspension of the micro-organism (1 x 10(8) cfu/ml) and neat TiO2 or silver-loaded TiO2 Were irradiated with a high pressure mercury lamp for various time periods at neutral pH (7.0). Silver loading (1%, w/w) dramatically reduced the illumination time for complete degradation (less than 1-2 min) and minimum catalyst concentration was determined as 0.1 mg/mL Possible killing mechanism and intermediate products were also determined. Occurrence of lipidperoxidation which produces malondialdehyde (MDA) was proposed but the method employed was so effective that all micro-organisms and intermediate products were further degraded to harmless products. (C) 2001 Elsevier Science B.V. All rights reserved.