[Effect of photoreactivating light intensity on photoreactivation of Escherichia coli and fecal coliform in the tertiary effluent disinfected by UV].

ABSTRACT

The effect of photoreactivating light intensity on photoreactivation of E. coli and fecal coliform in tertiary effluent after UV disinfection were investigated. The response of the two species to intensity of photoreactivating light varied with UV dose and bacterial species. Photoreactivation of E. coli after UV irradiation of 5 mJ/cm2 achieved the same maximum under three selected intensities of photoreactivating light (0-43 microW/cm2). A threshold existed when UV dose increased to 20 mJ/cm2 and significant photoreactivation was detected only under intensity of light 43 microW/cm2. With different UV doses irradiation, fecal coliform showed little difference under selected intensities of photoreactivating light in this study. The different effects of photoreactivating light intensity on photoreactivation of different bacteria should be considered when proposing the control measurements.