Effect of pre- and post-UV disinfection conditions on photoreactivation of fecal coliforms in wastewater effluents

Photoreactivation of microorganisms following UV disinfection can represent a disadvantage to using UV technology for wastewater treatment since recovery may, in some cases, reach several logs. Thus, decreasing photoreactivation can lead to considerable savings in capital and operating costs. Object...

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Bibliographic Details
Published in:Water research (Oxford) 2010-05, Vol.44 (9), p.2885-2893
Main Authors: Hallmich, Catherine, Gehr, Ronald
Format: Article
Language:English
Subjects:
Applied sciences
Bacterial Proteins - radiation effects
coliform bacteria
disinfection
Disinfection - methods
duration
Effluents
Enterobacteriaceae - radiation effects
Enzymes - radiation effects
Exact sciences and technology
Fecal coliforms
feces
Feces - microbiology
Irradiation
Light
Logs
Microbial Viability - radiation effects
Operating costs
Other industrial wastes. Sewage sludge
Photodecomposition
Photolyase
photolysis
Photoreactivation
Pollution
Populations
summer
ultraviolet radiation
Ultraviolet Rays
UV disinfection
Waste water
Wastes
Wastewater effluent
wastewater treatment
Water Pollutants
Water treatment and pollution
Winter
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Summary:Photoreactivation of microorganisms following UV disinfection can represent a disadvantage to using UV technology for wastewater treatment since recovery may, in some cases, reach several logs. Thus, decreasing photoreactivation can lead to considerable savings in capital and operating costs. Objectives of this study were to determine pre- and post-UV irradiation conditions which could decrease fecal coliform (FC) photoreactivation in wastewater effluents. Results indicated that delaying exposure to photoreactivating light for 3 h suppressed photoreactivation after relatively low UV doses of 10 and 20 mJ/cm 2. Moreover, at least 440 lux (0.065 mW/cm 2) of visible light was needed to initiate photoreactivation. Additionally, photoreactivation decreased significantly when samples were exposed to visible light simultaneously or prior to UV irradiation. This was more significantly observed for winter samples, where photoreactivation decreased by nearly 50%. Finally, summer FC populations were more sensitive to inactivation and less able to photoreactivate than winter populations. The effect of visible light on photoreactivation levels may be explained by several photo-mechanisms of FC photolyase, such as photodecomposition of the MTHF co-factor and reduction of FAD.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2010.02.003