2003 Volume 1 Issue 1 Pages 119-124
Presence of wastewater particles is often cited as the reason for failure of UV-irradiation to inactivate targeted organisms to desired level. However, till now there is no method to directly assess the inactivation of particle-associated indicator organisms after UV-irradiation. In this study, we tried to establish a method to identify viable bacteria within wastewater particles. This method was then used to distinguish between particle-associated viable and non-viable bacteria after UV-irradiation. The objective was to assess the fraction of particles of different sizes that are associated with coliform bacteria and to analyze the impact that these particles may have on the residual coliform concentration after UV-radiation. We found that fluorescent in-situ hybridization (FISH) in conjugation with Direct viable count can be effectively used for identification and counting of particle associated Enterobacteriaceae. The method can also successfully distinguish viable bacteria after UV-radiation. We found that only 2 percent of the total coliforms in the supernatant from the secondary clarifier of the Shibaura water treatment plant is associated with particles. Association of coliforms were maximum for the particle size ranging from 41-µm to 80-µm. It was also found that UV-radiation can effectively penetrate through most of the waste water particles.
