Public Drinking Water Systems Research Articles

A hierarchical modeling approach for estimating national distributions of chemicals in public drinking water systems.

Water quality studies often include the analytical challenge of incorporating censored data and quantifying error of estimation. Many analytical methods exist for estimating distribution parameters when censored data are present. This paper presents a Bayesian-based hierarchical model for estimating the national distribution of the mean concentrations of chemicals occurring in U.S. public drinking water systems using fluoride and thallium as examples. The data used are Safe Drinking Water Act compliance monitoring data (with a significant proportion of left-censored data). The model, which assumes log-normality, was evaluated using simulated data sets generated from a series of Weibull distributions to illustrate the robustness of the model. The hierarchical model is easily implemented using the Markov chain Monte Carlo simulation method. In addition, the Bayesian method is able to quantify the uncertainty in the estimated cumulative density function. The estimated fluoride and thallium national distributions are presented. Results from this study can be used to develop prior distributions for future U.S. drinking water regulatory studies of contaminant occurrence.

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.

Nanocrystalline Coatings in Copper Pipes for Cold Water Plumbing Systems

Copper is the most important raw material for cold-water plumbing systems in private and public buildings. One disadvantage of copper pipes is that small amounts of copper dissolve into the drinking water. Protective layers of cuprite (anodic coatings industrially applied) typically have lattice imperfections that can facilitate general corrosion. In this study, cuprite coatings were applied cathodically using electrolysis. The galvanic deposition at fixed voltage resulted in a coarse crystalline coating; the crystallites had a [111] fibre texture. Pulsed electrodeposition (PED) resulted in a variety of layers with different semiconducting characteristics. With this procedure, nanocrystalline arrangements could also be produced. In this case however, it was only possible to coat short sections of piping, which led to increased disorder at the edges. All coated pipes, together with untreated control pipes, were connected for a period of one to three years to the public drinking water system. During this time, nearly all of the coated pipes demonstrated a lower level of copper solubility than the control pipes.

Formation and bacterial composition of young, natural biofilms obtained from public bank-filtered drinking water systems

In Germany, bank-filtered raw water and ground water is mainly used for drinking water conditioning. Microorganisms, which are neither retarded by the subsoil passage of the bank-filtration, nor by the different filtration and disinfection steps at the water works, cause the growth of biofilms on different materials originally used in drinking water distribution systems. The development, the phylogenetical diversity and the bacterial metabolic activities of biofilms on polyethylen (PE-HD), polyvinylchlorid (PVC), steel and copper were analyzed at different sampling points. The incubation experiments were performed under natural conditions using a flow device technique. The devices were installed after the activated carbon filters and disinfection step at the water works and at two different house branch connections within the distribution system of the conditioned drinking water of the water works. The synthetic materials were colonized very rapidly within a few days in significant higher densities than steel and copper. The total bacterial cell counts of the biofilms were measured by DAPI (4′,6-diamidino-2-phenylindole) staining. The metabolic activities of the bacteria were quantified by the use of the redox dye CTC (5-cyano-2,3-ditolyl tetrazolium chloride), which is frequently described as an indicator for respiration. The highest respiratory activities were observed in biofilms from synthetic materials grown after the activated carbon filters at the water works. A significant reduction of the total bacterial cell counts and respiratory activities of about 80% was measured due to the disinfection at the water works. A time dependent growth of bacteria in biofilms was observed at the two sampling points within the distribution system, whereas the percentage of CTC-reducing cells stabilized at 35%. The in situ-hybridizations with fluorescence labelled, group-specific rRNA targeted oligonucleotide probes revealed the following: (i) bacteria of the Beta- and Gamma-subclass of Proteobacteria were found most frequently within the biofilm population, (ii) the percentage of the different subclasses depended on the used material, (iii) there were no significant changes in bacterial subclass composition of the biofilms taken from the water works and house branch connections. In addition, polymerase chain reaction (PCR), southern blot hybridization and in situ hybridization were used to detect facultative pathogenic bacteria in biofilms. Non-pneumophila Legionella were found in a relative high percentage up to about 7% in many biofilms, whereas fecal streptococci were detected only in few biofilms of the drinking water distribution systems

Oregon's SDWRLF gets under way

Oregon takes a step‐by‐step approach to setting up a state drinking water revolving loan fund.The 1996 Safe Drinking Water Act amendments established a Drinking Water State Revolving Fund (DWSRF) to help states and their community drinking water systems meet regulations. Oregon's efforts to secure and administer its share of the DWSRF led to the design and development of the state Safe Drinking Water Revolving Loan Fund (SDWRLF). The SDWRLF program was developed over the course of 18 months in close cooperation with the Oregon Drinking Water Advisory Committee, the Oregon Health Division, the Oregon Economic Development Department, and the Oregon Department of Environmental Quality. The design that emerged from their collaborative contributions represents a significant effort to improve and protect public drinking water systems in the state.

Biochemical fingerprinting for typing of Aeromonas strains from food and water

The PhenePlate (PhP) system for biochemical fingerprinting is based on analysis of the kinetics of biochemical tests in microplates. This was evaluated for typing Aeromonas spp. isolates from drinking water and food and 78 Aeromonas strains isolated on different occasions over 6 months from three public drinking water systems. The system was highly discriminating and the diversity index, as calculated from 65 unrelated isolates, was 0.993, and 53 different biochemical phenotypes (BPTs) were found. Food isolates were more homogeneous than random Aeromonas strains and identical isolates were sometimes found in food of different origin. Each public drinking water system contained several BPTs but some of these were dominant at several sampling sites and on several sampling occasions in a system. The PhP system is suitable for typing Aeromonas strains from food and water. It is simple to handle and can be used with large numbers of isolates.

Determining Internal Corrosion Potential in Water Supply Systems

The monitoring requirements for corrosion control in public drinking water systems established in 1980 placed responsibility with individual water purveyors, in conjunction with state regulation. The monitoring deadline was February 1983. Once data were gathered, their usefulness in addressing corrosion problems depended on how they were compiled. This report provides guidance for water purveyors in organizing these data, suggests laboratory and field investigations, and outlines a corrosion control strategy.

National policy to control hazardous drinking water constituents in The Netherlands

Stimulated by cholera epidemics in The Netherlands in the second half of the nineteenth century, it was for reasons of public health that public drinking water systems were established. At that stage it was still possible to select unpolluted water resources for the drinking water supply. Even since, the people got an almost unlimited confidence in the quality of their drinking water. Nowadays it becomes more and more difficult for the water companies notto betray this confidence because of the increased pollution of ground and surface water and the technical limitations in purifying this water. In our attempts to remove or to reduce hazardous constituents even other unwanted substance may be introduced into the drinking water. Advanced detection methods for measuring the quality of the water have made suspect nearly all water resources. However, besides getting information about the presence of a suspected constituent one has to know also which concentration in drinking water may be dangerous to public health. In this field a lot of research still has to be done. It is important to realize that in spite of our extended knowledge onpurification systems it is better to rely on wellprotected raw water resources for which ‘relatively simple’ purification methods are sufficient to produce a safe drinking water. The geographical situation of The Netherlands in the delta of the Rhine ans the Meuse does not make it easy to pursue such a policy. International cooperation in cleaning these river basins is a first requisite.

Cancer incidence and trihalomethane concentrations in a public drinking water system.

Four thousand two hundred fifty-five cases of esophageal, stomach, colon, rectal, bladder, and pancreatic cancer reported from Erie County, NY between 1973 and 1976 were analyzed in terms of their relationship to type of water source, level of trihalomethane (THM) and various social and economic parameters. Among white males, a significant positive correlation existed between pancreatic cancer incidence rates and THM level. No other significant correlations were observed. This research lends little or no support to the hypothesis that THM levels which meet present standards are related to the incidence of human cancer.