Influence of photoreactivating light intensity and incubation temperature on photoreactivation of<i>Escherichia coli</i>following LP and MP UV disinfection

Quek, Puay Hoon; Hu, Jiangyong

doi:10.1111/j.1365-2672.2008.03723.x

Cited by 40 publications

(26 citation statements)

References 17 publications

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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: 82%

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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Section: Methodssupporting

confidence: 82%

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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“…However, the strength of this local source was not anticipated to be large, because most of these resuspended E. coli had been inactivated by solar radiation during the day before they were settled into the sediment and overnight recovery in the submerged sediment was unlikely under typical, natural conditions. 5 In this sense, the observed high E. coli concentration in the submerged sediment (mean value 1585 CFU 100 mL −1 ) underneath the knee-deep water was more likely to be a result of early morning deposition of E. coli from deeper water than an original source. The local input of E. coli in the knee-deep water, even if significant to some extent, does not necessarily weaken the contribution of nighttime wave-transported E. coli onshore.…”

Section: ■ Discussionmentioning

confidence: 95%

Wave-Induced Mass Transport Affects Daily Escherichia coli Fluctuations in Nearshore Water

Whitman

Nevers

et al. 2012

Environ. Sci. Technol.

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Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s(-1)). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731-6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.

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“…The following equation proposed in previous studies (Quek and Hu ,b) was applied to obtain repair at each hour:

% repair = \frac{N_{t} - N_{0}}{N_{i} - N_{0}}

…”

Section: Methodsmentioning

confidence: 99%

Effects of salinity and temperature on inactivation and repair potential of Enterococcus faecalis following medium- and low-pressure ultraviolet irradiation

et al. 2016

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

Cited by 40 publications

References 17 publications

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

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

Wave-Induced Mass Transport Affects Daily Escherichia coli Fluctuations in Nearshore Water

Effects of salinity and temperature on inactivation and repair potential of Enterococcus faecalis following medium- and low-pressure ultraviolet irradiation

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