Urban villages are unique residential neighborhoods in urban areas in China. Roof tanks are their main form of water supply, and water quality deterioration might occur in this system because of poor ...hygienic conditions and maintenance. In this study, water samples were seasonally collected from an urban village to investigate the influence of roof tanks as an additional water storage device on the variation in the microbial community structure and pathogenic gene markers. Water stagnation in the roof tank induced significant decreases in chlorine (p < 0.05), residual chlorine was as low as 0.02 mg/L in spring. Propidium monoazide (PMA)-qPCR revealed a one-magnitude higher level of total viable bacterial concentration in roof tank water samples (2.14 ± 1.81 × 105 gene copies/mL) than that in input water samples (3.57 ± 2.90 × 104 gene copies/mL, p < 0.05), especially in spring and summer. In addition, pathogenic fungi, Mycobacterium spp., and Legionella spp. were frequently detected in the roof tanks. Terminal users might be exposed to higher microbial risk induced by high abundance of Legionella gene marker. Spearman's rank correlation and redundancy analysis showed that residual chlorine was the driving force that promoted bacterial colonization and shaped the microbial community. It is worth noted that the sediment in the pipe will be agitated when the water supply is restored after the water outages, which can trigger an increase in turbidity and bacterial biomass. Overall, the findings provide practical suggestions for controlling microbiological health risks in roof tanks in urban villages.
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Small water supply systems (SWSSs) are often more vulnerable to waterborne disease outbreaks. In Japan, many SWSSs operate without regulation under the Waterworks Law, yet there is limited ...investigation into microbial contamination and the associated health risks. In this study, the microbiological water quality of four SWSSs that utilize mountain streams as water sources and do not install water treatment facilities were monitored for over 2 years. In investigated SWSSs, the mean heterotrophic plate counts were below 350 CFU/mL, and the total bacterial loads (16S rDNA concentration) ranged from 4.71 to 5.35 log
copies/mL. The results also showed the consistent presence of fecal indicator bacteria (FIB), i.e., Escherichia coli and Clostridium perfringens, suggesting the potential of fecal pollution. E. coli was then utilized as an indicator to assess the health risk posed by E. coli O157:H7 and Campylobacter jejuni. The results indicated that the estimated mean annual risk of infection and disability-adjusted life years (DALYs) exceeded acceptable levels in all SWSSs for the two reference pathogens. To ensure microbial water safety, implementing appropriate water treatment facilities with an estimated mean required reduction of 5-6 log
was necessary. This study highlighted the potential microbial contamination and health risk level in SWSSs that utilize mountain streams as water sources, even though the water sources were almost not affected by human activities. Furthermore, this study would also be helpful in supporting risk-based water management to ensure a safe water supply in SWSSs.
Faecal pollution of water and the resulting potential presence of human enteric pathogens is a predominant threat to public health. Microbiological water quality can be assessed by the detection of ...standard faecal indicator bacteria (SFIB) such as E. coli or certain Enterococcus species. In recent years, isothermal amplification methods have become a useful alternative to polymerase chain reaction (PCR), allowing molecular diagnostics with simple or no instrumentation. In this study, a novel screening method for the molecular detection of Enterococcus spp. by loop-mediated isothermal amplification (LAMP) is described. A set of six specific LAMP primers was designed to amplify a diagnostic fragment of the Enterococcus 23S rRNA gene, which is present in several enterococcal species targeted by quantitative PCR (qPCR), which is the standard technique recommended by the US Environmental Protection Agency. Sensitivity and specificity tests were performed using a set of 30 Enterococcus and non-target bacterial reference strains. It is shown that LAMP is equally sensitive and even more specific than the qPCR assay. A dilution series of Enterococcus faecalis DNA revealed that the LAMP method can reliably detect 130 DNA target copies per reaction within 45 min. Additionally, enterococci isolated from Austrian surface waterbodies, as well as a set of DNA extracts from environmental waters, were tested. Contingency analysis demonstrated a highly significant correlation between the results of the developed LAMP assay and the reference qPCR method. Furthermore, a simple staining procedure with a fluorescence dye demonstrated the identification of amplified products by eye. In conclusion, this method is an important component for the efficient screening and testing of water samples in low-resource settings lacking sophisticated laboratory equipment and highly trained personnel, requiring only a simple heating block.
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•A rapid method for the molecular detection of enterococci in water is presented.•The developed LAMP assay is equally sensitive and specific as the reference qPCR.•The reaction takes place at a constant temperature provided by a heating block.•Results can be visualised within 1 min.
Nine novel biological stability parameters for drinking water have been developed recently. Here, we report data for these nine parameters in treated water from 34 treatment plants in the Netherlands ...to deduce guidance values for these parameters. Most parameters did not show a strong correlation with another biological stability parameter in the same sample, demonstrating that most parameters hold different information on the biological stability of drinking water. Furthermore, the novel biological stability parameters in treated water varied considerably between plants and five parameters in treated water were significantly lower for drinking water produced from groundwater than surface water. The maximum biomass concentration (MBC7), cumulative biomass potential (CBP14) from the biomass production potential test (BPP-W) and the total organic carbon concentration in treated water from groundwater were predictive parameters for HPC22 and Aeromonas regrowth in the distribution system. Guidance values of 8.6 ng ATP L−1, 110 d·ng ATP L−1 and 4.1 mg C L−1 were deduced for these parameters, under which the HPC22 and Aeromonas numbers remain at regulatory level. The maximum biomass growth (MBG7) from the BPP-W test, the particulate and/or high molecular organic carbon and the iron accumulation rate in treated water from surface water were predictive parameters for HPC22 and Aeromonas regrowth in the distribution system. Deduced guidance values for these biological stability parameters were 4.5 ng ATP L−1, 47 μg C L−1 and 0.34 mg Fe m−2 day−1, respectively. We conclude from our study that a multiple parameter assessment is required to reliable describe the biological stability of drinking water, that the biological stability of drinking water produced from groundwater is described with other parameters than the biological stability of drinking water produced from surface water, and that guidance values for predictive biological stability parameters were inferred under which HPC22 and Aeromonas regrowth is under control.
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•Guidance values for novel biostability parameters for drinking water were deduced.•Treated water of 34 different treatment plants in the Netherlands were analysed.•Guidance values for TOC, MBC7 and CPB14 define biostable water from groundwater.•Guidance values for MBG7, PHMOC and FeAR define biostable water from surface water.•Multiple parameters are needed to reliable define biostability of drinking water.
Microbiological quality of waters must be assessed to ensure that no health risk due to pathogenic microorganisms is associated with its use. As it is impossible to measure the abundance of all ...possible pathogens, it is general practice to quantify the abundance only of one or a few fecal indicator bacteria (FIB), organisms which are selected to be indicative of fecal pollution and can therefore serve as general indicators of microbiological water quality. Yet, even by focusing on this limited number of indicator organisms, it is still unfeasible to experimentally monitor their levels at the high spatiotemporal resolution often needed in real applications. Therefore, direct FIB measurements are increasingly combined with the use of models. The aim of this review is to present and evaluate the wide variety of models used so far in the scientific literature to simulate and predict FIB concentrations in natural surface waters. First, the distinction is made between regression-based and mechanistic models. While the first are particularly useful in operational contexts and indeed can produce reliable short-term predictions, they do not allow an in-depth understanding of the processes. Because the sources and processes are not modeled explicitly, they cannot be used to test the effect of changes in these internal and external forcings, e.g., to evaluate the impact of different management options. These questions can only be addressed by the use of mechanistic models, which are often based on rather complex computational methods. These models explicitly consider the effect on FIB concentrations due to horizontal transport, external sources, decay, and/or sediment-related processes. It is not possible to make statements about "best" practices, given the broad range of study domains and questions. Instead, we attempted to compile the modeling approaches published so far in a comprehensive and transparent way, hoping that the resulting overview would help to better understand current models and more efficiently set up future ones.
Bacterial concentration is one of the most important aspects of water quality. Many regions in the world are affected by increasing urbanization and a potential increase in bacterial concentrations ...in waters. We used long-term data from 68 stations in eight watersheds in Eastern Thailand to quantify the temporal and geographical variation in total and fecal coliform bacteria. Descriptive statistics showed considerable seasonal, inter-annual, and geographical variation. In order to quantify this multi-level variation, we built a predictive model of bacterial loads. Using fixed- and mixed-effects regression models, we built a model including the effects of urbanization and other significant variables. The best model, fitted by restricted maximum likelihood, included the effects of season, year, urbanization as fixed effects, and of watershed and station as nested, random effects. Temporal variation was related to seasonal and annual variations. Spatial variation had a very significant impact on the bacterial concentrations. Urbanization was an important factor controlling concentrations of bacteria in rivers: we found that the proportion of urban area around a station had a statistically significant effect on log-transformed total coliform bacterial concentration with a slope equal to 1.3 (SE = 0.3), and on log-transformed fecal coliform bacterial concentration with a slope equal to 1.4 (SE = 0.3). Our model predicts that bacterial concentrations would be multiplied by 20 if land is transformed from non-urban to fully urban.
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•A predictive model of bacterial concentrations in rivers in response to urbanization was built using data from 68 stations over 10 years.•Bacterial concentrations varied considerably through time, seasons, and among stations.•Linear models with fixed and random effects explained up to 66% of the variance in bacterial concentrations.•Urbanization is predicted to multiply bacterial concentrations by 20.
Drinking water quality deteriorates from treatment plant to customer taps, especially in the plumbing system. There is no direct evidence about what the differences are contributed by plumbing ...system. This study compared the water quality in the water main and at customer tap by preparing a sampling tap on the water main. The biomass was quantified by adenosine triphosphate (ATP) and the microbial community was profiled by 454 pyrosequencing. The results showed that in distribution pipes, biofilm contributed >94% of the total biomass, while loose deposits showed little contribution (< 2%) because of the low amount of loose deposits. The distribution of biological stable water had minor effects on the microbiocidal water quality regarding both quantity (ATP 1 ng/L vs. 1.7 ng/L) and community of the bacteria. Whereas the plumbing system has significant contribution to the increase of active biomass (1.7 ng/L vs. 2.9 ng/L) and the changes of bacterial community. The relative abundance of Sphingomonas spp. at tap (22%) was higher than that at water main (2%), while the relative abundance of Pseudomonas spp. in tap water (15%) was lower than that in the water from street water main (29%). Though only one location was prepared and studied, the present study showed that the protocol of making sampling tap on water main offered directly evidences about the impacts of plumbing system on tap water quality, which makes it possible to distinguish and study the processes in distribution system and plumbing system separately.
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Greenhouse gas (GHG) emissions contribute to climate change. The public water utility of Amsterdam wants to operate climate neutrally in 2020 to reduce its GHG emissions. Energy recovery from the ...water cycle has a large potential to contribute to this goal: the recovered energy is an alternative for fossil fuel and thus contributes to the reduction of GHG emissions. One of the options concerns thermal energy recovery from drinking water. In Amsterdam, drinking water is produced from surface water, resulting in high drinking water temperatures in summer and low drinking water temperatures in winter. This makes it possible to apply both cold recovery and heat recovery from drinking water. For a specific case, the effects of cold recovery from drinking water were analyzed on three decisive criteria: the effect on the GHG emissions, the financial implications, and the effect on the microbiological drinking water quality. It is shown that cold recovery from drinking water results in a 90% reduction of GHG emissions, and that it has a positive financial business case: Total Cost of Ownership reduced with 17%. The microbial drinking water quality is not affected, but biofilm formation in the drinking water pipes increased after cold recovery.
•Thermal energy can be recovered from drinking water.•Both heat and cold can be recovered from drinking water.•Cold recovery did not affect the microbiological water quality negatively.•Cold recovery reduced GHG emissions with 90%.•Cold recovery showed a 17% lower TCO compared with traditional cooling.
This study developed a model simulating the seasonal and spatial variations of microbiological water quality (expressed in terms of Escherichia coli concentrations) in rivers. The model (SENEQUE-EC) ...consists of a microbiological module appended to a hydro-ecological model describing the functioning of the entire Scheldt drainage network. The microbiological module describes the sources of E. coli, their transport and the processes responsible for the fate of E. coli once released into the natural environment (mortality, settling and resuspension). This model differentiates the dynamics of three types of E. coli: free-floating E. coli, E. coli attached to suspended solids in the water column and E. coli present in sediments. The model was verified by comparison of its results with temporal and spatial distributions of field data in different stretches of rivers of the Scheldt drainage network. It was then used to test various scenarios involving diverse modifications in wastewater management, which was shown to be the most determining factor of microbiological water quality. Due to its low temporal resolution, the SENEQUE-EC is poorly adapted to describing the microbiological quality in areas under tidal influence. Therefore, the data of the SENEQUE-EC model were used as upstream boundary conditions to run a microbiological model with a high temporal resolution devoted to the tidal Scheldt River and Estuary (the SLIM-EC2 model).
► We modelled microbiological water quality (Escherichia coli concentrations) in rivers. ► The model was applied to the rivers of the Scheldt drainage network. ► The predictions of the model were validated by comparison with field data. ► The model was used to test scenarios of wastewater management on water quality. ► Model data were used as boundary conditions to run a model of the Scheldt estuary.
Microbial water quality assessment currently relies on cultivation-based methods. Nucleic acid-based techniques such as quantitative PCR (qPCR) enable more rapid and specific detection of target ...organisms and propidium monoazide (PMA) treatment facilitates the exclusion of false positive results caused by DNA from dead cells.
Established molecular assays (qPCR and PMA-qPCR) for legally defined microbial quality parameters (Escherichia coli, Enterococcus spp. and Pseudomonas aeruginosa) and indicator organism group of coliforms (implemented on the molecular detection of Enterobacteriaceae) were comparatively evaluated to conventional microbiological methods. The evaluation of an extended set of drinking and process water samples showed that PMA-qPCR for E. coli, Enterococcus spp. and P. aeruginosa resulted in higher specificity because substantial or complete reduction of false positive signals in comparison to qPCR were obtained. Complete compliance to reference method was achieved for E. coli PMA-qPCR and 100% specificity for Enterococcus spp. and P. aeruginosa in the evaluation of process water samples. A major challenge remained in sensitivity of the assays, exhibited through false negative results (7–23%), which is presumably due to insufficient sample preparation (i.e. concentration of bacteria and DNA extraction), rather than the qPCR limit of detection. For the detection of the indicator group of coliforms, the evaluation study revealed that the utilization of alternative molecular assays based on the taxonomic group of Enterobacteriaceae was not adequate.
Given the careful optimization of the sensitivity, the highly specific PMA-qPCR could be a valuable tool for rapid detection of hygienic parameters such as E. coli, Enterococcus spp. and P. aeruginosa.
•PMA treatment in combination with quantitative PCR resulted in substantial or complete reduction of false positivesignals raised from DNA of dead cells.•Functional markers achieved higher specificity than universal markers.•Escherichia coli PMA-RT-PCR in process water exhibited 100% specificity and sensitivity.
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