Micro-Organism Re-Growth in Wastewater Disinfected by UV Radiation and Ozone: A Micro-Biological Study

Abstract

A series of disinfection experiments using UV radiation and ozone was performed on the secondary effluent from a wastewater treatment plant at a pilot plant scale. The microbial population in the inflowing wastewater and the treated outflow water were quantified for each of the treatment modules (fecal coliforms, fecal streptococci, Salmonella spp. (presence/absence), Clostridium Sulphite-reducers, Pseudomonas aeruginosa, Staphylococcus aureus, coliphages, nematodes, intestinal nematodes and pathogenic fungi). Treated water was stored in opaque tanks at a temperature between 20 and 22 degrees C, after which, a one-month study of the regrowth of the bacterial flora, nematodes and fungi was carried out. Clostridium Sulphite-reducers, pathogenic fungi and nematodes were the micro-organisms showing a greatest degree of resistence to UV- and Ozone-treatment. It was only concerning Clostridium and Pseudomonas abatement that significant elimination results were achieved with both technologies.

Removal of pathogenic bacteria from sewage-treated effluent and biosolids for agricultural purposes

“…Dungeni et al (2010) suggested UV disinfection as an additional treatment process of effluents to increase the effective inactivation and removal of pathogenic bacteria and viruses. However, Alonso et al (2004) found that Clostridium spp., showed a greatest degree of resistance to UV treatment. Munir et al (2010) indicated that the disinfection of effluents by UV process did not contribute to the significant reduction of antibiotic-resistant bacteria.…”

“…Lepeuple et al (2004) reported that the C. perfringens is common in raw sludge and resistant to heat, and hence their removal can be related to removal of spore-forming species such as Bacillus sp. C. perfringens has been reported as resistant to oxidizing agents and to UV disinfection (Alonso et al 2004). Rouch et al (2011) indicated that C. perfringens appeared to be a conservative indicator during their study on the air drying of sludge generated from two STPs in Victoria, Australia.…”

Disinfection and Antimicrobial Processes

“…Ozone was more effective than UV for the more resistant species. Clostridium sulfite-reducers and Pseudomonas aeruginosa exhibited significant regrowth over time, which was believed to be due to the presence of nutrients in the water (Alonso et al, 2004).…”

Review of Upflow Anaerobic Sludge Blanket Reactor Technology: Effect of Different Parameters and Developments for Domestic Wastewater Treatment

“…Therefore, posttreatment of anaerobically treated wastewater is usually required in order to improve the quality of effluent in accordance with the irrigation standards. This has been successfully done by conventional systems such as maturation ponds, waste stabilization ponds, polishing ponds, constructed wetlands, rotating biological contactors, moving bed biofilm reactor, downflow hanging sponge [60][61][62], and advanced oxidative processes (AOPs) [63,64].…”