Comparison of methods of enumerating coliforms after UV disinfection

Abstract

In view of the differences that have been found between the most-probable-number and membrane filtration methods for the recovery of coliforms from chlorinated samples, the survival of total and fecal coliforms in UVirradiated effluent samples, as tested by the most-probable-number and standard single-step membrance filtration methods, was compared. There were no significant differences in the survival of total and fecal coliforms, as tested by the two methods. In a separate set of experiments comparing total and fecal coliform survival, as tested by the most-probable-number method, only a very small but statistically significant difference of 0.1 log survival units was found. For UV-disinfected wastewater effluents, standard one-step

UV inactivation of pathogenic and indicator microorganisms

“…Samples of secondary effluent were collected from the Sandy Creek Wastewater Treatment Plant, Durham, N.C. A portion of the samples was gently filtered through a nylon screen with approximately 10-,um pores to remove most of the larger particles capable of harboring embedded bacteria. These samples were irradiated within 2 h. Coliform survivors were enumerated by the one-step total coliform membrane filtration procedure (1), since no significant difference was found for the survival of UV-irradiated coliforms as enumerated by either the standard membrane filtration or most-probable-number total and fecal coliform procedures (21). Standard plate count microorganisms were enumerated according to standard methods (1).…”

High‐Performance, Low‐Cost Solar Collectors for Disinfection of Contaminated Water

“…Research has demonstrated that the effects of water composition (turbidity, temperature, ionic strength, pH, and so forth) are probably the most significant with respect to field applications of solar disinfection. For example, an adverse effect of suspended solids on UV disinfection has been reported by several authors (Acra et al, 1990;Qualls et al, 1984;and Screible, 1987). In this case, sunlight attenuation by particulate matter was not expected to be significant because of the low turbidity levels in the contaminated water used (0.8 to 0.9 Nephelometric turbidity units).…”