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Drinking water microbiology has emerged from decades of relative complacency to recognize there can be major concerns with potable water quality. Many of these issues are a result of an explosion of information on new waterborne agents, treatment problems with raw-source water qualities, biofilm development in some distribution systems and specialized requirements in water quality unique to hospitals and industries. Protozoan cyst survival after some disinfection practices involving surface water impoundments and virus occurrence in poorly protected groundwaters have provided reasons for expanding minimum treatment of surface waters and for requiring disinfection of all groundwaters unless there is a demonstrative data base to support exceptions in treatment requirements. Official monitoring of small water supplies must be increased on a monthly basis and a rapid alert established to inform water plant operators of unsatisfactory water qualities. As an option, application of operational tests to analyse water quality in terms of chlorine residual, turbidity, total coliforms and heterotrophic bacterial counts in small water plant operations should be encouraged. This would provide the operator at remote locations with the opportunity to utilize the information to make necessary treatment adjustments or corrections in water distribution deficiencies promptly and be a supplement to the official regional monitoring program. Application of drinking water alternative sources (bottled water and water from point-of-use treatment devices) should be viewed by the health authorities as only a temporary solution, not as a permanent fix for a public water supply known to present some established health risk to consumers. The public must also recognize that bottled water is not frequently monitored by health laboratories for acceptable quality and the use of home treatment devices places the responsibility of proper maintenance on the user. Microbial quality improvements in drinking water to hospitals and food industries can frequently be achieved through a routine, systematic flushing program for building plumbing networks and associated attachment devices. In other situations, use of booster disinfection or point-of-use devices may provide the important special water quality requirements for certain industrial applications. In any event, these supplemental treatment measures will require careful in-plant monitoring and maintenance to prevent reversals in water quality enhancement.
OBJECTIVE: To assess the contamination level of total and faecal coliforms in water wells and distribution networks, and their association with human health in Gaza Governorate, Gaza Strip. METHODS: Data were obtained from the Palestinian Ministry of Health on contamination of total and faecal coliforms in water wells and distribution networks, and on the incidence of water-related diseases in Gaza Governorate. An interview questionnaire was conducted with 150 residents of Gaza. RESULTS: The contamination level of total and faecal coliforms exceeded that of the World Health Organization (WHO) limit for water wells and networks. However, the contamination percentages in networks were higher than that in wells. Giardiasis was strongly correlated with faecal coliform contamination in water networks (r=0.7) compared with diarrhoeal diseases and hepatitis A (r=0.3 and 0.1, respectively). Diarrhoeal diseases were the highest self-reported diseases among interviewees in Gaza city. Such diseases were more prevalent among people using municipal water than people using desalinated water and water filtered at home for drinking (OR=1.6). Intermittent water supply and sewage flooding seemed to contribute largely to self-reported diseases. People in Gaza Strip have good knowledge on drinking water contamination, and this is reflected in good practice. CONCLUSIONS: Water quality has deteriorated in Gaza Strip. This may contribute to the prevalence of water-related diseases. Self-reported diseases among interviewees in Gaza City were associated with source of drinking water, intermittent water supply, sewage flooding and age of water, and wastewater networks.
Water reuse is a widespread practice in most Mediterranean countries. Some countries have no wastewater treatment facilities and direct reuse of raw wastewater is occurring while others have a well-established national reuse policy. Water reuse microbiological standards, when existing, significantly differ from one country to another. Some countries have adopted regulations close to the California's Water Recycling Criteria whereas other countries have chosen criteria based on the World Health Organisation (WHO) guidelines. California standards are technologically based requirements aimed at eliminating the presence of pathogens. The WHO guidelines relied on epidemiological evidences though few were available. Their revision on the basis of new epidemiological investigations and quantitative microbiological risk assessment (QMRA) provided by Blumenthal et al., together with added QMRA data, helped proposing Mediterranean guidelines. Acceptable annual risks related to bathing and potable water drinking were taken as benchmarks. This proposal is designed to protect individuals against realistic maximum exposures and to provide minimum and affordable requirements which should constitute the basis of water reuse regulations in every country of the region. Inadequacies of the actual knowledge do not allow a definitive position regarding the guideline limits; other scientific and technical basis are still required.
OBJECTIVE: Point-of-use (POU) water treatment systems are self-contained units that can be used by recreational enthusiasts who normally obtain drinking water from untreated sources (i.e., rivers, lakes, etc). Microbiological water purifier units are capable of removing all waterborne pathogens. The purpose of this study was to evaluate a new technology (Structured Matrix) capable of micro-biologically purifying the water without the use of chemical disinfectants or an external power requirement. METHODS: Each of 3 identical portable water filtration units were evaluated for their ability to remove Klebsiella terrigena, poliovirus type 1, rotavirus SA-11, and Cryptosporidium parvum oocysts. Units were operated according to the manufacturer's instructions to process 378 L of water. Each unit was challenged with test organisms after 0, 94, 190, 227, 284, 340, and 378 L had passed through it. For the 227-L and 284-L challenges, a "worst-case" water quality (4 degrees C, pH 9, and turbidity 30 NTU) was used that contained 1500 mg/L dissolved solids and 10 mg/L humid acid. At 340-L and 378-L challenges, worst-case water quality was adjusted to pH 5.0. Units were tested after stagnation for 48 hours following passage of 190, 340, and 378 L of water. RESULTS: The geometric average removal exceeded 99.9999% for bacteria, 99.99% for viruses, and 99.9% for Cryptosporidium parvum oocysts. CONCLUSION: These units comply with the criteria guidelines for microbial removal under the United States Environmental Protection Agency's "Guide Standard and Protocol for Testing Microbiological Water Purifiers."
The World Health Organization (WHO) recently produced draft guidelines for safe recreational water environments. The microbiological standards proposed in the guidelines are expected to overestimate the degree of water quality required to provide given levels of public health protection. The WHO standards were obtained by means of a risk assessment which featured a dose-response model derived from a series of randomised controlled trials. The trials have many strengths but biases and problems with statistical analysis are likely to have led to over-estimation of the risks from bathing in the dose-response model. In addition, the WHO risk assessment failed to consider the effects of uncertainty and variability in risk estimates and sensitivity to model assumptions. Improved standards could be obtained by extending the risk assessment to examine these effects and by incorporating a suitably revised dose-response model.
The microbial quality of livestock drinking water was evaluated in 473 cattle water troughs located at 99 different cattle operations. The mean log10-transformed coliform and Escherichia coli concentrations per milliliter of trough water were 1.76 +/- 1.25 (SD) and 0.98 +/- 1.06 (SD), respectively. The degree of E. coli contamination was positively associated with the proximity of the water trough to the feedbunk, protection of the trough from direct sunlight, lower concentrations of protozoa in the water, and warmer weather. Salmonella sp. were isolated from 2/235 (0.8%) troughs and shigatoxigenic-E. coli O157 was recovered from 6/473 (1.3%) troughs. Four experimental microcosms simulating cattle water troughs were used to further evaluate the effects of protozoal populations on the survival of E. coli O157 in cattle water troughs. Escherichia coli O157 of bovine fecal origin proliferated in all microcosms. Reduction of protozoal populations by treatment with cycloheximide was associated with increased persistence of E. coli O157 concentrations in the microcosms. Water troughs are a major source of exposure of cattle to enteric bacteria, including a number of foodborne pathogens, and this degree of bacterial contamination appeared to be associated with potentially controllable factors.
In the summer 2001, the microbiological water quality of two contiguous urban coastal beaches (Porto, Portugal) was surveyed for 18 consecutive days. The sampling strategy consisted in sampling surface water in early morning, noon and afternoon. A total of 184 samples were processed at Pastoras beach, a confined area between two jetties, and Ourigo Beach more open to the ocean. At the first beach site, all samples exceeded fecal contamination above guide values (GV) and 82.6% above mandatory values (MV) set out in the EU Bathing Water Directive; whereas at Pastoras Beach, the figures were 93.5% for GV and 26.1% for MV, showing a potential health risk. The periodicity of fecal indicators in raw sewage, the tidal status and wind conditions dramatically influenced the water quality. The quality decreased in the morning regardless of tide conditions, but improved subsequently during the day, particularly during high tide and under the influence of afternoon NW winds. These dynamics are incompatible with the fortnight routine sampling according to the recommendations of the EU Bathing Water Directive, and the strategy should be revised on a beach-to-beach basis, having in mind the profile for the coastal zone.
A UK-based scheme of water microbiology assessment requires participants to record counts of relevant organisms. Not every sample will contain the target number of organisms because of natural variation and therefore a range of results is acceptable. Results which are tail-end (i.e. at the extreme low or high end of this range) could occasionally be reported by any individual laboratory by chance. Several tail-end results might imply a laboratory problem. Statistical assessment is done in two stages. A non-parametric test of the distribution of tail-end counts amongst laboratories is performed (Cochran's Q) and, if they are not random, then observed and expected frequencies of tail-end counts are compared to identify participants who may have reported excessive numbers of low or high results. Analyses so far have shown that laboratories find high counts no more frequently than would be expected by chance, but that significant clusters of low counts can be detected among participants. These findings have been observed both in short-term and in long-term assessments, thus allowing detection of new episodes of poor performance and intermittent problems. The analysis relies on an objective definition of tail-end results. Working definitions are presented which should identify poor performance in terms of microbiological significance, and which allow fair comparison between membrane-filtration and multiple-tube techniques. Smaller differences between laboratories, which may be statistically significant, will not be detected. Different definitions of poor performance could be incorporated into future assessments.
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In a 3-year period, four series of simulated water samples containing selected test strains were distributed to more than 50 laboratories in The Netherlands for bacteriological testing. Participating laboratories examined the samples by enrichment or membrane filtration methods, or both, for total coliform organisms, thermotolerant coliform organisms, faecal streptococci and standard plate counts (37 degrees and 22 degrees C) according to Dutch standard methods. The results were quantitatively satisfactory: the distribution of positive and negative results with subsamples conformed to stochastic variation; the standard deviation of membrane or plate counts was usually in the range which may be expected from a Poisson distribution, and there was good correspondence between average counts in participating laboratories and those expected from controls in the organizing laboratory. Problems of a qualitative nature were frequently encountered, however. Among them were a false positive response with a strain of Enterobacter cloacae in the thermotolerant coliform test; a false positive result with Clostridium perfringens in enrichment tests for total or thermotolerant coliform organisms and false positive results with Micrococcus varians in the faecal streptococcus test by membrane filtration. It is concluded that quality assessment should be a consistent activity in water microbiology laboratories. For this purpose, stable and well characterized reference materials are needed.
The Thames Water recycling plant at the Millennium Dome, London, reclaimed three sources of water: greywater from the washbasins, rainwater from the Dome roof and groundwater from a borehole on site. These were pre-treated separately, and the mixed stream filtered using ultrafiltration and reverse osmosis membranes. Monitoring for indicator microorganisms was undertaken throughout the plant and in the reclaimed water distribution system, as well as ad-hoc monitoring for the presence of pathogens in the raw waters. Treatment to the level of ultrafiltration was more than adequate to produce a water quality meeting existing worldwide reclaimed water guidelines for toilet flushing. Owing to the excellent quality of the water leaving the plant, no significant microbiological growth was observed in the reclaimed water distribution system during the year. The raw greywater exhibited a higher faecal bacterial load than the rainwater and groundwater, as predicted from more human contact (i.e. hand washing). Environmental strains of Legionella were observed in the three raw greywater samples analysed for pathogens, as was Cryptosporidium, Giardia and faecal enterococci. The rainwater had relatively high levels of faecal bacteria, probably of avian origin. Giardia was detected in one rainwater sample confirming the potential for this water source to contain pathogens.
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Using the membrane filtration technique to count total coliform (TC), fecal coliform (FC) and fecal streptococci (FS), the microbiological water quality of the Mfoundi River and four of its representative tributaries at Yaoundé, Cameroon, was assessed for human use and contact. Sampling was conducted so as to examine the potential origin of fecal contamination and how rainfall affects the measured concentrations of indicators organisms. Our results revealed that waters were not safe for human use or primary contact according to the standards for water quality established by the Word Health Organization (WHO). Indeed, these waters exhibited high concentrations of TC (Mean +/- SD = 5.6 x 10(8) +/- 2.5 x 10(6) CFU/100 ml), FC (Mean +/- SD = 6.8 x 10(5) +/- 2.4 x 10(3) CFU/100 ml) and FS (Mean +/- SD = 7.3 x 10(5) +/- 2.1 x 10(3) CFU/100 ml) that varied with the sampling sites and points. FC/FS ratio suggested that this contamination was more from warm-blooded animals than humans and correlation analysis points to the role of rainfall as a contributing factor, which enhanced the bacterial numbers detected. We conclude that there is a great potential risk of infection for users of waters from the Mfoundi River and its tributaries at Yaoundé.
STUDY OBJECTIVES: To evaluate the inspection grading system for water sites implemented during the Athens 2004 Olympic inspection programme. DESIGN: The relation between the standardised inspections results of 716 water supply systems and 289 public swimming pools, and microbiological test results of 2358 samples collected during inspections was examined. SETTING: Athens, Thessaloniki, Patra, Volos, and Iraklio, Greece. Inspections and sampling conducted during a two year period before the 2004 Olympics. MAIN RESULTS: Swimming pools unsatisfactory inspection grading results were significantly associated with positive water microbiological test results (relative risk = 2.5, p<0.05). One of the six violations of swimming pools and five of the seven violations of water supply systems designated as "critical" water safety hazards in the inspection reports were significantly associated with positive microbiological test results. The receiver operating characteristic analysis identified the unsatisfactory score designed in the swimming pools standardised inspection report, as the ideal score (-15), in adequately producing positive microbiological test results (sensitivity 13.2%, specificity 89%). CONCLUSIONS: This study shows the utility of standardised inspection grading systems in waterborne diseases prevention planning and implementation strategies of policy makers and regulators. Future water quality assessment should be based on the implementation of a robust standardised inspection system and reduce the need of microbiological tests.
An early warning system using a rapid enzymatic semiautomated method suitable for fecal coliform detection in recreational waters within 8 h was developed further and evaluated in this study. This rapid method was compared to the standard method followed in the United Kingdom. We used 1,011 samples originating from 206 different locations in Wales. When we assessed the presence or absence of fecal coliforms, targeting very low levels of contamination, we obtained 83.9% agreement between the rapid method and the lauryl sulfate broth-membrane filtration technique, whereas direct confirmation of the samples processed by the rapid method showed 89. 3% agreement. Environmental enzymatic background activity was found to be the main limiting factor for this method. Owing to a specific and integrated handling of the results by the software of the instrument, the percentage of false-positive results (a consequence of enzymatic background) was successfully limited to 2.9% by the direct confirmation evaluation. However, 7.8% false-negative results due to "late-growers" had to be accepted in order to produce results within a working day. At present, the method can be used in a more conservative way to assess the environmental threshold of 100 CFU of fecal coliforms per 100 ml in recreational waters. The implications of our findings with regard to the applicability of rapid enzymatic methods are discussed.
The growth in United Kingdom salad production is dependent on irrigation to maintain product quality. There are concerns that irrigation with poor-quality water could pose a disease risk. This article examines the key issues in the emerging debate on the microbiological quality of water used for salad irrigation in the United Kingdom. The links between irrigation water quality and foodborne disease, and the current international guidance on irrigation water quality, are firstly reviewed. The findings indicate that a number of recent food-poisoning outbreaks have been linked to the consumption of fresh fruits and vegetables and that unhygienic product handling is implicated as the principal source of contamination. There is also credible evidence that salads contaminated in the field, including by irrigation water, can pose a small disease risk at the point of sale. Although irrigation water-quality standards exist in various forms internationally, there is no nationally agreed on standard used in the United Kingdom. This paper then describes the results of a survey conducted in 2003 of United Kingdom irrigation practices that might influence the microbiological quality of salads. The survey showed that surface water is the principal irrigation water source, that overhead irrigation predominates, that the gap between the last irrigation and harvest may be < 24 h in many cases, and that current water-quality monitoring practices are generally very limited in scope. This paper concludes with a discussion of the issues emerging from the review and survey, including the need for improved water-quality monitoring, and the problems associated with establishing water-quality standards that could be either too strict or too lax.
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