Water safety plan enhancements with improved drinking water quality detection techniques.

Drinking water quality has been regulated in most European countries for nearly two decades by the drinking water directive 98/83/EC. The directive is now under revision with the goal of meeting stricter demands for safe water for all citizens, as safe water has been recognized as a human right by the United Nations. An important change to the directive is the implementation of a risk-based approach in all regulated water supplies. The European Union Framework Seventh Programme Aquavalens project has developed several new detection technologies for pathogens and indicators and tested them in water supplies in seven European countries. One of the tasks of the project was to evaluate the impact of these new techniques on water safety and on water safety management. Data were collected on risk factors to water safety for five large supplies in Denmark, Germany, Spain and the UK, and for fifteen small water supplies in Scotland, Portugal and Serbia, via a questionnaire aiming to ascertain risk factors and the stage of implementation of Water Safety Plans, and via site-specific surveys known as Sanitary Site Inspection. Samples were collected from the water supplies from all stages of water production to delivery. Pathogens were detected in around 23% of the 470 samples tested. Fecal contamination was high in raw water and even in treated water at the small supplies. Old infrastructure was considered a challenge at all the water supplies. The results showed that some of the technique, if implemented as part of the water safety management, can detect rapidly the most common waterborne pathogens and fecal pollution indicators and therefore have a great early warning potential; can improve water safety for the consumer; can validate whether mitigation methods are working as intended; and can confirm the quality of the water at source and at the tap.

Removal of Surrogate Bacteriophages and Enteric Viruses from Seeded Environmental Waters Using a Semi-technical Ultrafiltration Unit.

Experiments to determine the removal of viruses in different types of water (surface water from two reservoirs for drinking water treatment, treated groundwater and groundwater contaminated with either 5 or 30 % of wastewater) by ultrafiltration were performed with a semi-technical ultrafiltration unit. Concentrations of human adenoviruses (HAdVs), murine norovirus (MNV), and the bacteriophages MS2, ΦX174 and PRD1 were measured in the feed water and the filtrate, and log removal values were calculated. Bacteria added to the feed water were not detected in the filtrates. In contrast, in most cases viruses and bacteriophages were still present in the filtrates: log removal values were in the range of 1.4-6.3 depending on virus sizes and water qualities. Best removals were observed with bacteriophage PRD1 and HAdVs, followed by MNV and phages MS2 and ΦX174. Virus size, however, was not the only criterion for efficient removal. In diluted wastewater as compared to drinking water and uncontaminated environmental waters, virus removal was clearly higher for all viruses, most likely due to higher membrane fouling. For quality assessment purposes of membrane filtration efficiencies with regard to the elimination of human viruses the small bacteriophages MS2 and ΦX174 should be used as conservative viral indicators.

Inactivation of F-specific bacteriophages during flocculation with polyaluminum chloride - a mechanistic study.

Bacteriophages are often used as surrogates for enteric viruses in spiking experiments to determine the efficiencies of virus removal of certain water treatment measures, like e.g. flocculation or filtration steps. Such spiking experiments with bacteriophages are indispensable if the natural virus concentrations in the raw water of water treatment plants are too low to allow the determination of elimination levels over several orders of magnitude. In order to obtain reliable results from such spiking tests, it is essential that bacteriophages behave comparable to viruses and remain stable during the experiments. To test this, the influence of flocculation parameters on the bacteriophages MS2, Qß and phiX174 was examined. Notably, the F-specific phages MS2 and Qß were found to be inactivated in flocculation processes with polyaluminum chloride (PACl). In contrast, other aluminum coagulants like AlCl3 or Al2(SO4)3 did not show a comparable effect on MS2 in this study. In experiments testing the influence of different PACl species on MS2 and Qß inactivation during flocculation, it could be shown that cationic dissolved PACl species (Al13) interacted with the MS2 surface and hereby reduced the surviving phage fraction to c/c0 values below 1*10(-4) even at very low PACl concentrations of 7 µmol Al/L. Other inactivation mechanisms like the irreversible adsorption of phages to the floc structure or the damage of phage surfaces due to entrapment into the floc during coagulation and floc formation do not seem to contribute to the low surviving fraction found for both F-specific bacteriophages. Furthermore, no influence of phage agglomeration or pH drops during the flocculation process on phage inactivation could be observed. The somatic coliphage phiX174 in contrast did not show sensitivity to chemical stress and in accordance only slight interaction between Al13 and the phage surface was observed. Consequently, F-specific phages like MS2 should not be used as surrogate for viruses in flocculation experiments with PACl to determine the removal rates of viruses, as the results are influenced by a strong inactivation of the bacteriophages due to the experimental conditions.

Development and validation of a FISH-based method for the detection and quantification of E. coli and coliform bacteria in water samples.

Monitoring of microbiological contaminants in water supplies requires fast and sensitive methods for the specific detection of indicator organisms or pathogens. We developed a protocol for the simultaneous detection of E. coli and coliform bacteria based on the Fluorescence in situ Hybridization (FISH) technology. This protocol consists of two approaches. The first allows the direct detection of single E. coli and coliform bacterial cells on the filter membranes. The second approach includes incubation of the filter membranes on a nutrient agar plate and subsequent detection of the grown micro-colonies. Both approaches were validated using drinking water samples spiked with pure cultures and naturally contaminated water samples. The effects of heat, chlorine and UV disinfection were also investigated. The micro-colony approach yielded very good results for all samples and conditions tested, and thus can be thoroughly recommended for usage as an alternative method to detect E. coli and coliform bacteria in water samples. However, during this study, some limitations became visible for the single cell approach. The method cannot be applied for water samples which have been disinfected by UV irradiation. In addition, our results indicated that green fluorescent dyes are not suitable to be used with chlorine disinfected samples.

Incidence of faecal contaminations in chlorinated and non-chlorinated distribution systems of neighbouring European countries.

Data on E. coli incidence in drinking water samples have been evaluated for 4 European countries. Within the EC project MicroRisk, large volume sampling was done in the United Kingdom (with disinfectant residual), the Netherlands (mainly without disinfectant residual) and Germany (without disinfectant residual). No E. coli were found and very low background concentrations (<10(-4) per L) were calculated. Furthermore, data of 280,000 water samples collected in France (with disinfectant residual), the Netherlands and Germany (both with and without disinfectant residual) were evaluated for E. coli incidence. In total, similar results were obtained for Germany and the Netherlands. In France, significantly higher incidences occurred as more small rural supply systems were included. The detailed data evaluation revealed a slight increase of mean E. coli concentrations during distribution in Germany and the Netherlands, for both disinfected and non-disinfected supply zones. This suggests that, if technical measures are taken to avoid contamination during distribution, non-disinfected supply zones can be regarded as being as safe as disinfected supply zones. Furthermore, the indicator principle of E. coli for faecal contaminations is valid in non-disinfected supply zones. In chlorinated systems, on-line-monitoring of chlorine residuals represents a good means to detect ingress of organic material.

Heterotrophic plate count and consumer's health under special consideration of water softeners.

The phenomenon of bacterial growth in water softeners is well known since years. To upgrade the hygienic safety of water softeners, the German DIN Standard 19636 was developed, to assure that the distribution system could not be contaminated by these devices and that the drinking water to be used in the household still meets the microbiological standards according to the German drinking water guidelines, i.e. among others heterotrophic plate count (HPC) below 100 CFU/ml. Moreover, the standard for the water softeners includes a test for contamination with Pseudomonas aeruginosa which has to be disinfected during the regeneration phase. This is possible by sanitizing the resin bed during regeneration by producing chlorine. The results of the last 10 years of tests of water softeners according to DIN 19636 showed that it is possible to produce water softeners that comply with that standard. Approximately 60% of the tested models were accepted. P. aeruginosa is used as an indicator for potentially pathogenic bacteria being able to grow also in low nutrient conditions which normally prevail in drinking water. Like other heterotrophs, the numbers of P. aeruginosa increase rapidly as stagnation occurs. Normally P. aeruginosa is not present in the distributed drinking water. However, under certain conditions, P. aeruginosa can be introduced into the drinking water distribution system, for instance, during construction work. The occurrence of P. aeruginosa is shown in different cases in treatment plants, public drinking water systems and in-house installations. The compliance with DIN 19636 provides assurance that a water softener will not be a constant source of contamination, even if it is once inoculated with a potentially pathogenic bacterium like P. aeruginosa.