scholarly journals A comparison of DNA repair and survival of Escherichia coli O157:H7 following exposure to both low- and medium-pressure UV irradiation

2007 ◽  
Vol 5 (3) ◽  
pp. 407-415 ◽  
Author(s):  
J. L. Zimmer-Thomas ◽  
R. M. Slawson ◽  
P. M. Huck
Keyword(s):  
Dna Repair ◽  
Drinking Water ◽  
Water Treatment ◽  
Uv Irradiation ◽  
Drinking Water Treatment ◽  
Uv Exposure ◽  
E Coli ◽  
Medium Pressure ◽  
Treatment Conditions ◽  
Low Levels

DNA repair and survival of pathogenic E. coli O157:H7 was investigated following exposure to ultraviolet (UV) radiation from both low-pressure (LP) and medium-pressure (MP) lamps. This study included irradiation at UV doses used in drinking water treatment and lower doses indicative of potential treatment problems. Immediately following UV exposure, an average log inactivation of 4.5 or greater was observed following all tested doses of LP (5, 8, 20 and 40 mJ/cm2) or MP UV (5 and 8 mJ/cm2) indicating the sensitivity of E. coli O157:H7 to UV irradiation. Following conditions conducive to repair, maximum photo repair occurred rapidly within 30 minutes after low doses (5 and 8 mJ/cm2) of LP UV. The rate of repair was much higher than reported previously in non-pathogenic E. coli (which occurred within 2 hours). In contrast to LP UV, limited photo repair of E. coli O157:H7 was observed following MP UV exposure at reduced doses (5 and 8 mJ/cm2). At these lower doses, low levels of light independant repair were observed following LP UV, but not following exposure of MP UV irradiation. This study indicates that MP UV may enhance UV disinfection of E. coli O157:H7 by reducing the ability to repair following non-ideal treatment conditions. Following doses used in drinking water treatment (20 and 40 mJ/cm2), low levels of photo repair following LP UV were evident.

A novel low-cost multi-barrier system for drinking water treatment in rural and suburban areas

2019 ◽  
Vol 15 (1) ◽  
pp. 48-65 ◽  
Author(s):  
Stephen Siwila ◽  
Isobel C. Brink
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Granular Media ◽  
Low Cost ◽  
Water System ◽  
Drinking Water Treatment ◽  
Fecal Coliforms ◽  
E Coli ◽  
Suburban Areas ◽  
Novel Concept

Abstract A low-cost multi-barrier drinking water system incorporating geotextile fabric for pre-filtration, silver-coated ceramic granular media (SCCGM) for filtration and disinfection, granular activated carbon (GAC) as an adsorption media and a safe storage compartment for treated water has been developed and tested. The developed system offers a novel concept of point-of-use drinking water treatment in rural and suburban areas of developing countries. The system is primarily aimed at bacterial and aesthetic improvement and has been optimised to produce >99.99% E. coli and fecal coliforms removal. Although particular emphasis was placed on the elimination of bacteria, improvement of the acceptability aspects of water was also given high priority so that users are not motivated to use more appealing but potentially unsafe sources. This paper discusses key system features and contaminant removal performance. A system using SCCGM only was also tested alongside the multi-barrier system. Strengths and weaknesses of the system are also presented. Both the developed and SCCGM-only systems consistently provided >99.99% E. coli and fecal coliforms removal at an optimum flow of 2 L/h. The developed system significantly recorded improvements of aesthetic aspects (turbidity, color, taste and odor). Average turbidity removals were 99.2% and 90.2% by the multi-barrier and SCCGM-only systems respectively.

Perfluorooctane sulphonate and perfluorooctanoic acid in drinking and environmental waters

2009 ◽  
Vol 367 (1904) ◽  
pp. 4119-4136 ◽  
Author(s):  
Paul C. Rumsby ◽  
Clare L. McLaughlin ◽  
Tom Hall
Keyword(s):  
Drinking Water ◽  
Activated Carbon ◽  
Water Treatment ◽  
Degradation Products ◽  
Drinking Water Treatment ◽  
Perfluorooctanoic Acid ◽  
Consumer Products ◽  
Environmental Waters ◽  
Perfluorinated Chemicals ◽  
Low Levels

Perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA) are chemicals that have been used for many years as surfactants in a variety of industrial and consumer products. Owing to their persistent, bioaccumulative and toxic (PBT) characteristics, PFOS has been phased out by its principal producer and the use of PFOA has been reduced. This PBT potential and a number of pollution incidents have led in recent years to an increase in studies surveying the concentrations of PFOS and PFOA in environmental waters worldwide. This paper reviews the results of these studies, as well as the monitoring that was conducted after the pollution incidents. The results of surveys suggest that PFOS and PFOA are found in environmental waters worldwide at low levels. In general, these levels are below health-based values set by international authoritative bodies for drinking water. There have been limited measurements of these chemicals in drinking water, but again these are below health-based values, except in some cases following pollution incidents. Monitoring studies suggested that where PFOS and PFOA were detected, they were at similar levels in both source and drinking water, suggesting that drinking water treatment does not remove these chemicals. However, new data show that PFOS and PFOA are effectively removed by granular activated carbon absorbers in practice. Further research is required on the newer perfluorinated chemicals that appear to be safer, but their degradation products have not as yet been fully studied.

Enhanced effectiveness of medium-pressure ultraviolet lamps on human adenovirus 2 and its possible mechanism

2009 ◽  
Vol 60 (4) ◽  
pp. 851-857 ◽  
Author(s):  
Gwy-Am Shin ◽  
Jung-Keun Lee ◽  
Karl G. Linden
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Human Exposure ◽  
Drinking Water Treatment ◽  
Human Adenovirus ◽  
Repair Process ◽  
Uv Disinfection ◽  
Medium Pressure ◽  
Treatment Processes ◽  
Uv Technology

There has been growing concern over human exposure to adenoviruses through drinking water due to their apparent high resistance to UV irradiation and the anticipated widespread use of ultraviolet (UV) disinfection in drinking water treatment processes. However, most inactivation studies on adenoviruses were performed using only one type of UV technology—low-pressure (LP) UV, and little is known about the effectiveness of different UV technologies such as medium- pressure (MP) UV or other polychromatic UV technologies. In this work, the kinetics and extent of inactivation of a human adenovirus (adenovirus 2 (Ad2)) by both monochromatic LP and polychromatic MP UV were evaluated to determine the effectiveness of these UV technologies on human adenoviruses. Inactivation of Ad2 by LP UV was very slow and only 0.87 and 2.17 log10 inactivation was achieved with UV doses of 30 and 90 mJ/cm2, respectively. However, inactivation of Ad2 by MP UV was much faster and 2.19 and 5.36 log10 inactivation was observed with the same UV doses (30 and 90 mJ/cm2, respectively). It appears that MP UV is more effective against Ad2 than LP UV and the enhanced effectiveness of MP UV on Ad2 is likely due to its ability to inhibit the repair process in UV-irradiated Ad2.

scholarly journals Potential Repair of Escherichia coli DNA following Exposure to UV Radiation from Both Medium- and Low-Pressure UV Sources Used in Drinking Water Treatment

2002 ◽  
Vol 68 (7) ◽  
pp. 3293-3299 ◽  
Author(s):  
J. L. Zimmer ◽  
R. M. Slawson
Keyword(s):  
Escherichia Coli ◽  
Drinking Water ◽  
Water Treatment ◽  
Uv Radiation ◽  
Drinking Water Treatment ◽  
Low Pressure ◽  
Plate Count ◽  
Treatment Technology ◽  
Medium Pressure ◽  
Uv Lamp

ABSTRACT The increased use of UV radiation as a drinking water treatment technology has instigated studies of the repair potential of microorganisms following treatment. This study challenged the repair potential of an optimally grown nonpathogenic laboratory strain of Escherichia coli after UV radiation from low- and medium-pressure lamps. Samples were irradiated with doses of 5, 8, and 10 mJ/cm2 from a low-pressure lamp and 3, 5, 8, and 10 mJ/cm2 from a medium-pressure UV lamp housed in a bench-scale collimated beam apparatus. Following irradiation, samples were incubated at 37°C under photoreactivating light or in the dark. Sample aliquots were analyzed for up to 4 h following incubation using a standard plate count. Results of this study showed that E. coli underwent photorepair following exposure to the low-pressure UV source, but no repair was detectable following exposure to the medium-pressure UV source at the initial doses examined. Minimal repair was eventually observed upon medium-pressure UV lamp exposure when doses were lowered to 3 mJ/cm2. This study clearly indicates differences in repair potential under laboratory conditions between irradiation from low-pressure and medium-pressure UV sources of the type used in water treatment.

scholarly journals Evaluation of the microbial risk reduction due to selective closure of the raw water intake before drinking water treatment

2007 ◽  
Vol 5 (S1) ◽  
pp. 81-97 ◽  
Author(s):  
J. Åström ◽  
S. Petterson ◽  
O. Bergstedt ◽  
T. J. R. Pettersson ◽  
T. A. Stenström
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Water Intake ◽  
Drinking Water Treatment ◽  
Threshold Level ◽  
Waterborne Diseases ◽  
Raw Water ◽  
Indicator Organisms ◽  
Microbial Risk ◽  
E Coli

Short-term peaks in pathogen concentrations may increase the risks for waterborne diseases considerably. In this study the occurrence of indicator organisms and pathogens in the river Göta älv at the raw water intake to Göteborg was evaluated and related to risk for drinking water consumption. About half of the 24 pathogen samples, taken during event and non-event conditions, were positive for at least one of the following: Cryptosporidium, Giardia, norovirus, enterovirus, Campylobacter and E. coli O157. Positive pathogen detects were often associated with heavy rainfalls and viruses with a sewage emergency discharge. The annualised probability of infection from this type of event was calculated from pathogen concentrations in a QMRA model. Given that the water intake is not closed, the risk given present water treatment seems to be acceptable for Giardia; however, it is at a borderline for Cryptosporidium and insufficient for noro- and enteroviruses. Present results emphasise the need for an appropriate intake regulation with respect to high pathogen loads, as the risk increases with time of exposure to pathogen contaminants. Rather than a threshold level on E. coli, reports on upstream microbial discharges are valuable for quick pathogen indications.

scholarly journals Decentralized solar-powered drinking water ozonation in Western Kenya: an evaluation of disinfection efficacy

2020 ◽  
Vol 4 ◽  
pp. 56
Author(s):  
Colin Hendrickson ◽  
Jared Oremo ◽  
Oscar Oluoch Akello ◽  
Simon Bunde ◽  
Isaac Rayola ◽  
...  
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Surface Water ◽  
Drinking Water Treatment ◽  
Treatment System ◽  
Coliform Bacteria ◽  
Small Scale ◽  
Water Treatment System ◽  
E Coli ◽  
Solar Powered

 Background: Decentralized drinking water treatment methods generally apply membrane-based treatment approaches. Ozonation of drinking water, which previously has only been possible at large centralized facilities, can now be accomplished on a small-scale using microplasma technology. The efficacy of decentralized solar-powered drinking water treatment systems has not previously been described. Methods: We established a 1,000L decentralized solar-powered water treatment system located in Kisumu County, Kenya. Highly contaminated surface water is pumped to the treatment system, which includes flocculation and filtration steps prior to ozonation. Turbidity, total coliform bacteria, and E. coli were measured at various stages of water treatment, and bacterial log reduction values (LRVs) were calculated. Results: Forty-seven trials were conducted in which1000L of water were flocculated, filtered, and ozonated for 180 minutes. Baseline turbidity and E. coli concentrations were reduced from a median of 238 nephelometric turbidity units (NTU) and 2,419.7 most probable number/100mL, respectively, in surface water to 1.0 NTU and undetectable E. coli after ozonation for 180 minutes. The median E. coli LRV was 3.99. Conclusions: The solar-powered, decentralized water treatment system that utilizes ozonation for disinfection was founded to reduce E. coli by more than 3 log-orders of magnitude despite the high turbidity of the raw water. Further research is needed to characterize limitations, scalability, economic viability, and community perspectives that could help determine the role for similar systems in other settings.

scholarly journals Concentration Detection of the E. coli Bacteria in Drinking Water Treatment Plants through an E-Nose and a Volatiles Extraction System (VES)

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 774
Author(s):  
Jeniffer Carrillo-Gómez ◽  
Cristhian Durán-Acevedo ◽  
Ramón García-Rico
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Water Samples ◽  
Drinking Water Treatment ◽  
Extraction System ◽  
Water Quality Control ◽  
Potential Health ◽  
E Coli ◽  
Water Treatment Plants

Water quality control remains an important topic of public health since some diseases, such as diarrhea, hepatitis, and cholera, are caused by its consumption. The microbiological quality of drinking water relies mainly on monitoring of Escherichia coli, a bacteria indicator which serves as an early sentinel of potential health hazards for the population. In this study, an electronic nose coupled to a volatile extraction system (was evaluated for the detection of the emitted compounds by E. coli in water samples where its capacity for the quantification of the bacteria was demonstrated). To achieve this purpose, the multisensory system was subjected to control samples for training. Later, it was tested with samples from drinking water treatment plants in two locations of Colombia. For the discrimination and classification of the water samples, the principal component analysis method was implemented obtaining a discrimination variance of 98.03% of the measurements to different concentrations. For the validation of the methodology, the membrane filtration technique was used. In addition, two classification methods were applied to the dataset where a success rate of 90% of classification was obtained using the discriminant function analysis and having a probabilistic neural network coupled to the cross-validation technique (leave-one-out) where a classification rate of 80% was obtained. The application of this methodology achieved an excellent classification of the samples, discriminating the free samples of E. coli from those that contained the bacteria. In the same way, it was observed that the system could correctly estimate the concentration of this bacteria in the samples. The proposed method in this study has a high potential to be applied in the determination of E. coli in drinking water since, in addition for estimating concentration ranges and having the necessary sensitivity, it significantly reduces the time of analysis compared to traditional methods.

Sign in / Sign up

Export Citation Format

Share Document