A relatively short list of reference viral, bacterial and protozoan pathogens appears adequate to assess microbial risks and inform a system-based management of drinking waters. Nonetheless, there are data gaps, e.g. human enteric viruses resulting in endemic infection levels if poorly performing disinfection and/or distribution systems are used, and the risks from fungi. Where disinfection is the only treatment and/or filtration is poor, cryptosporidiosis is the most likely enteric disease to be identified during waterborne outbreaks, but generally non-human-infectious genotypes are present in the absence of human or calf fecal contamination. Enteric bacteria may dominate risks during major fecal contamination events that are ineffectively managed. Reliance on culture-based methods exaggerates treatment efficacy and reduces our ability to identify pathogens/indicators; however, next-generation sequencing and polymerase chain reaction approaches are on the cusp of changing that. Overall, water-based Legionella and non-tuberculous mycobacteria probably dominate health burden at exposure points following the various societal uses of drinking water.

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Microbial Contamination of Drinking Water and Human Health from Community Water Systems

Antibiotic resistance in drinking water systems: Occurrence, removal, and human health risks.

Biological stability of drinking water refers to the concept of providing consumers with drinking water of same microbial quality at the tap as produced at the water treatment facility. However, uncontrolled growth of bacteria can occur during distribution in water mains and premise plumbing, and can lead to hygienic (e.g., development of opportunistic pathogens), aesthetic (e.g., deterioration of taste, odor, color) or operational (e.g., fouling or biocorrosion of pipes) problems. Drinking water contains diverse microorganisms competing for limited available nutrients for growth. Bacterial growth and interactions are regulated by factors, such as (i) type and concentration of available organic and inorganic nutrients, (ii) type and concentration of residual disinfectant, (iii) presence of predators, such as protozoa and invertebrates, (iv) environmental conditions, such as water temperature, and (v) spatial location of microorganisms (bulk water, sediment, or biofilm). Water treatment and distribution conditions in water mains and premise plumbing affect each of these factors and shape bacterial community characteristics (abundance, composition, viability) in distribution systems. Improved understanding of bacterial interactions in distribution systems and of environmental conditions impact is needed for better control of bacterial communities during drinking water production and distribution. This article reviews (i) existing knowledge on biological stability controlling factors and (ii) how these factors are affected by drinking water production and distribution conditions. In addition, (iii) the concept of biological stability is discussed in light of experience with well-established and new analytical methods, enabling high throughput analysis and in-depth characterization of bacterial communities in drinking water. We discussed, how knowledge gained from novel techniques will improve design and monitoring of water treatment and distribution systems in order to maintain good drinking water microbial quality up to consumer’s tap. A new definition and methodological approach for biological stability is proposed.

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Biological Stability of Drinking Water: Controlling Factors, Methods, and Challenges

A water demand end-use model was developed to predict water demand patterns with a small time scale (1 s) and small spatial scale (residence level). The end-use model is based on statistical inform...

Simulating Residential Water Demand with a Stochastic End-Use Model

In drinking water distribution systems (DWDS), biofilms are the predominant mode of microbial growth, with the presence of extracellular polymeric substance (EPS) protecting the biomass from environmental and shear stresses. Biofilm formation poses a significant problem to the drinking water industry as a potential source of bacterial contamination, including pathogens, and, in many cases, also affecting the taste and odor of drinking water and promoting the corrosion of pipes. This article critically reviews important research findings on biofilm growth in DWDS, examining the factors affecting their formation and characteristics as well as the various technologies to characterize and monitor and, ultimately, to control their growth. Research indicates that temperature fluctuations potentially affect not only the initial bacteria-to-surface attachment but also the growth rates of biofilms. For the latter, the effect is unique for each type of biofilm-forming bacteria; ammonia-oxidizing bacteria, for examp...

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Understanding, Monitoring, and Controlling Biofilm Growth in Drinking Water Distribution Systems

Robustness of the Drinking Water Distribution Network Under Changing Future Demand

Failure data are a valuable source of information on the condition of underground assets. Systematic registration of relevant items on cause, nature and circumstances of each occurring failure is, however, complicated in day-to-day practice. Moreover, in a network of limited size it takes a long time to obtain a statistically relevant amount of data. Dutch water companies in collaboration with the KWR Watercycle Research Institute have joined forces and developed a data standard and central database to store and analyse failure data. As of early 2012, 66,000 km of network are monitored, providing around 2,500 records on failure annually. All in all it provides solid information needed for strategic asset management that helps to support well established asset management plans.

Shared failure data for strategic asset management

WTP Gruszczyn supplies drinking water to a part of the city of Pozna?, in the Midwest of Poland. The conventional production flow control and pressure control of the facility was replaced by the advanced control software called OPIR. To assess the differences between conventional and advanced control, production flows and pressures of two operational periods were compared. The comparison showed that advanced control led to 83% less variation in the production flow and 29% lower pressure of the clear water pumps. The lower pressure resulted in 20% less background leakage and the overall energy costs of the system were reduced by 11.5% (337,000 kWh per year).

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Advanced control of a water supply system: A case study

Existing Dutch guidelines for the design of the drinking water and hot water system of nonresidential buildings are based on outdated assumptions on peak water demand or on unfounded assumptions on hot water demand. They generally overestimate peak demand values required for the design of an efficient and reliable water system. Recently, a procedure was developed based on the end-use model SIMDEUM to derive design-demand-equations for peak demand values of both cold and hot water during various time steps for several types and sizes of non-residential buildings, viz. offices, hotels and nursing homes. In this paper, the design-demand-equations are validated with measurements of cold and hot water patterns on a per second base and with surveys. The good correlation between the simulated water demand patterns and the measured patterns indicates that the basis of the design-demand-equations, the SIMDEUM simulated standardised buildings, is solid. Surveys were held to investigate whether the construction of the standardised buildings based on the dominant variable corresponds with practice. Surveys show that it is difficult to find relationships to equip the standardised buildings with users and appliances. However, the validation proves that with a proper estimation of the number of users and appliances in only the dominant functional room of the standardised buildings, SIMDEUM renders a realistic cold and hot water diurnal demand pattern. Furthermore, the new design-demand-equations based on these standardised buildings give a better prediction of the measured peak values for cold water flow than the existing guidelines. Moreover, the new design-demand-equations can predict hot water use well. In this paper it is illustrated that the new design-demand-equations lead to reliable and improved designs of building installations and water heater capacity, resulting in more hygienic and economical installations.

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Non-residential water demand model validated with extensive measurements and surveys

Water infrastructure is inherently a socio-technical system. Rapidly changing urban trends and long-term uncertainties make water infrastructure management complex. This paper analyses the dynamics of residential water consumption in the Netherlands since 1900. During this period, different drivers for change had an influence on residential water use. Results show that different (f)actors and trends had a role in the change of routines, perceptions, expectations, technologies and norms. Drivers of change in residential water consumption were for instance technological developments, the changing perception of comfort and external pressures, such as the oil crisis in the 1970s, and energy labelling of appliances and buildings. These changes led to transitions in the urban system by adjustments in regulative, normative, and cognitive aspects of regimes. In this paper, these transitions are analysed. For instance, full adoption of showers took 60 years, and the maximum annual adoption rate was 6.4% for washing machines. Understanding the links between physical and technological features and society can provide key information about how urban water transitions occur. This knowledge must be used in water infrastructure planning as it impacts demand and typical demand patterns.

J.H.G. Vreeburg

Papers

Robustness of the Drinking Water Distribution Network Under Changing Future Demand

Shared failure data for strategic asset management

Advanced control of a water supply system: A case study

Non-residential water demand model validated with extensive measurements and surveys

Analysing the dynamics of transitions in residential water consumption in the Netherlands