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

The majority of customer complaints for water authorities are related to dirty or discoloured water events. In the past two years, the Co-operative Research Centre for Water Quality and Treatment, (CRC), the Netherlands Kiwa Water Research (KIWA), Delft University of Technology (DUT) and Griffith University in Australia, have exchanged personnel, knowledge and resources to develop tools that allow improved understanding of processes leading to generation of discoloured water. This paper summarises the outcomes and demonstrates examples of the successful application of the Water Quality and Treatment's Particles Sediment Model (PSM) in the Netherlands and the trialling of the KIWA Re-suspension Potential Method (RPM) in several Australian water utilities.

International collaborative research on discoloured water

Real-life inline inspection of buried PVC push-fit joints

Water demand is a result of human behaviour. Human behaviour is characterized by daily and weekly cycles, and therefore water demand also shows daily and weekly cycles. The human behaviour and the short term water demand deviates from the normal cycles in 2 types of situations: 1: at special days or periods (like national holidays, or vacation periods): 2 at changes in the weather. In both situations not only the daily water consumption deviates from the normal patterns, but also the distribution of the quarter of an hourly demands over the day. The knowledge of the water demand was used to construct a water demand forecasting model. The model has been made adaptive, enabling to cope with fast variations in the water demand caused by weather conditions, slower seasonal variations in the water demand and even slower changes in the water demand caused by socio-economic changes.

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J.H.G. Vreeburg

Papers

International collaborative research on discoloured water

Real-life inline inspection of buried PVC push-fit joints

The use of an adaptive water demand prediction model

Evaluatie bevestigt effectiviteit ontwerpconcepten zelfreinigende netten

Hydrant maintenance as example of targeted asset management