Repair and regrowth of Escherichia coli after low- and medium-pressure ultraviolet disinfection

Hu, Jiangyong; Chu, Xiaona; Quek, Puay Hoon; Feng, Yaoyu; Tan, Xin

doi:10.2166/ws.2005.0044

Cited by 23 publications

(10 citation statements)

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“…This agrees with previous photoreactivation studies using fluorescent light where MP UV disinfection was reported to have none or lower photoreactivation levels as compared to LP UV disinfection (Oguma et al. 2002; Zimmer and Slawson 2002; Hu et al. 2005).…”

Section: Discussionsupporting

confidence: 92%

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Influence of photoreactivating light intensity and incubation temperature on photoreactivation ofEscherichia colifollowing LP and MP UV disinfection

Quek

2008

Journal of Applied Microbiology

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Aims: To investigate the effects of fluorescent light intensity, sunlight intensity and temperature on photoreactivation of Escherichia coli after low‐pressure (LP) and medium‐pressure (MP) ultraviolet (UV) disinfection. Methods and Results: Two E. coli strains were irradiated with LP and MP UV lamps, and exposed to various fluorescent light (0–23 kLux) and sunlight intensities (1–80 kLux), and temperatures (4–50°C). Escherichia coli concentrations were enumerated at hourly intervals to determine photoreactivation rates and final photoreactivation levels. Higher photoreactivation rates and levels were observed with increasing fluorescent light intensities, while high sunlight intensity (>12 kLux) caused a one‐log decrease in E. coli concentrations. When exposed to near‐optimum growth temperatures (23–37°C), photoreactivation levels were higher than those with too high (50°C) or too low (4°C) temperatures. Overall, photoreactivation following MP UV disinfection was lower than that following LP UV disinfection. Conclusions: Photoreactivation of bacteria following UV disinfection can be a problem in tropical countries where sunlight is abundant and temperatures are high, unless high sunlight intensity is present or if MP UV disinfection is employed. Significance and Impact of the Study: With the increased use of UV disinfection, it is imperative that photoreactivation be taken into account in the design of reactors based on site‐specific conditions of temperature and light intensity exposure.

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Section: Discussionsupporting

confidence: 92%

“…The results also indicate that E. coli exposed to MP UV irradiation achieved a lower level of repair, with a maximum recovery of about 70% under all fluorescent light intensities tested. This has previously been reported (Hu et al. 2005).…”

Section: Resultssupporting

confidence: 83%

Influence of photoreactivating light intensity and incubation temperature on photoreactivation ofEscherichia colifollowing LP and MP UV disinfection

Quek

2008

Journal of Applied Microbiology

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“…The recovery of solar-inactivated E. coli through deoxyribonucleic acid repair mechanism after the stress is removed is a complex process with both biotic and abiotic components. Previous laboratory studies have demonstrated a logarithmic dark repair rate of 20% (or a 0.01% rate in the original count) for E. coli at a nearly constant temperature of 23uC 6 1uC after ultraviolet (UV) disinfection (Hu et al 2005;Quek and Hu 2008). Their dark repair case is comparable to the conditions of the present study, where E. coli would settle out of the sunlightpenetrated layer of water and eventually into the sediment.…”

Section: Methodssupporting

confidence: 81%

Nearshore hydrodynamics as loading and forcing factors for Escherichia coli contamination at an embayed beach

Whitman

Nevers

et al. 2012

Limnology & Oceanography

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Numerical simulations of the transport and fate of Escherichia coli were conducted at Chicago's 63rd Street Beach, an embayed beach that had the highest mean E. coli concentration among 23 similar Lake Michigan beaches during summer months of [2000][2001][2002][2003][2004][2005], in order to find the cause for the high bacterial contamination. The numerical model was based on the transport of E. coli by current circulation patterns in the embayment driven by longshore main currents and the loss of E. coli in the water column, taking settling as well as bacterial dark-and solar-related decay into account. Two E. coli loading scenarios were considered: one from the open boundary north of the embayment and the other from the shallow water near the beachfront. Simulations showed that the embayed beach behaves as a sink for E. coli in that it generally receives E. coli more efficiently than it releases them. This is a result of the significantly different hydrodynamic forcing factors between the inside of the embayment and the main coastal flow outside. The settled E. coli inside the embayment can be a potential source of contamination during subsequent sediment resuspension events, suggesting that deposition-resuspension cycles of E. coli have resulted in excessive bacterial contamination of beach water. A further hypothetical case with a breakwater shortened to half its original length, which was anticipated to enhance the current circulation in the embayment, showed a reduction in E. coli concentrations of nearly 20%.Beach water, as the interface between the land and coastal waters, is a dynamic physical and ecological system. The transport and fate of fecal indicator bacteria (FIB) in beach water not only have direct implications for human health in coastal areas (Nevers and Whitman 2005;Frick et al. 2008) but also constitute an integral influence on the coastal ecosystem. Recently, computational models allowing for a simulation of temporal and spatial variations of model variables have been developed to understand microbial water quality in open beach waters of Lake Michigan (Liu et al. 2006;Thupaki et al. 2010). Embayed (i.e., partially enclosed) beach waters have been of particular interest because of their significantly more complex hydrodynamic properties and the tendency to accumulate FIB and other contaminants (Grant and Sanders 2010).The 63rd Street Beach of Chicago, a frequently closed beach, had by far the highest Escherichia coli concentration (geometric mean 140 MPN [most probable number], 100 mL 21 ) among 23 recreational beaches along Chicago's 37-km Lake Michigan shoreline during 2000-2005. In comparison, the site with the second-highest E. coli concentration was Montrose Beach, with a geometric mean of only 77 MPN 100 mL 21 (Whitman and Nevers 2008). Since typical meteorological (e.g., rainfall) and hydrodynamic (e.g., current and wave) events usually have spatial scales larger than 37 km, the unique situation of microbial contamination at 63rd Street Beach likely resulted from local facto...

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“…1, it was also found that lower UV doses were required to achieve the same log reduction of all E. coli strains when MP UV radiation was employed, indicating that MP UV disinfection was more efficient than LP UV disinfection. This has been reported previously [6], and is likely due to the more intense radiation and broader wavelength spectrum emitted by MP UV lamps that caused damage to intercellular biomolecules other than DNA [9].…”

Section: Resultssupporting

confidence: 65%

Indicators for photoreactivation and dark repair studies following ultraviolet disinfection

Quek

2008

J Ind Microbiol Biotechnol

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Repair of DNA in bacteria following ultraviolet (UV) disinfection can cause reactivation of inactivated bacteria and negatively impact the efficiency of the UV disinfection process. In this study, various strains of E. coli (wild-type, UV-resistant and antibiotic-resistant strains) were investigated for their ability to perform dark repair and photoreactivation, and compared based on final repair levels after 4 h of incubation, as well as repair rates. Analysis of the results revealed that the repair abilities of different E. coli strains can differ quite significantly. In photoreactivation, the log repair ranged from 10 to 85%, with slightly lower log repair percentages when medium-pressure (MP) UV disinfection was employed. In dark repair, log repair ranged from 13 to 28% following low-pressure (LP) UV disinfection. E. coli strains ATCC 15597 and ATCC 11229 were found to repair the fastest and to the highest levels for photoreactivation and dark repair, respectively. These strains were also confirmed to repair to higher levels when compared to a pathogenic E. coli O157:H7 strain. Hence, these strains could possibly serve as conservative indicators for future repair studies following UV disinfection. In addition, dimer repair by photoreactivation and dark repair was also confirmed on a molecular level using the endonuclease sensitive site (ESS) assay.

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Repair and regrowth of Escherichia coli after low- and medium-pressure ultraviolet disinfection

Cited by 23 publications

References 0 publications

Influence of photoreactivating light intensity and incubation temperature on photoreactivation ofEscherichia colifollowing LP and MP UV disinfection

Influence of photoreactivating light intensity and incubation temperature on photoreactivation ofEscherichia colifollowing LP and MP UV disinfection

Nearshore hydrodynamics as loading and forcing factors for Escherichia coli contamination at an embayed beach

Indicators for photoreactivation and dark repair studies following ultraviolet disinfection

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