Water temperature is often monitored at water sources and treatment works; however, there is limited monitoring of the water temperature in the drinking water distribution system (DWDS), despite a ...known impact on physical, chemical and microbial reactions which impact water quality. A key parameter influencing drinking water temperature is soil temperature, which is influenced by the urban heat island effects. This paper provides critique and comprehensive summary of the current knowledge, policies and challenges regarding drinking water temperature research and presents the findings from a survey of international stakeholders. Knowledge gaps as well as challenges and opportunities for monitoring and research are identified. The conclusion of the study is that temperature in the DWDS is an emerging concern in various countries regardless of the water source and treatment, climate conditions, or network characteristics such as topology, pipe material or diameter. More research is needed, especially to determine (i) the effect of higher temperatures, (ii) a legislative limit on temperature and (iii) measures to comply with this limit.
At the international level, the term “water security” (WS) has gained increasing attention in recent decades. At the operational level, WS is assessed using tools that define the concept using a ...variety of dimensions and sub-dimensions, with qualitative and quantitative indicators and parameters. The breadth of tools and concepts is an obstacle to the operationalisation of the concept of water security (WS). Clearly, we need a range of diverse data to evaluate water security (WS). However, there are several barriers to designing an optimal Data Gathering Strategy (DGS). Such a strategy must strike a balance between a wide range of competing and overlapping data requirements and characteristics including: resources, information, and impact. The proposed framework aims at filling the existing gaps, not by providing a strict procedure, but instead acting as a “compass”: five interfaces between data and context are identified to orient practitioners towards an optimal DGS. The conceptual aim of the framework can be summarised as shifting the focus of the DGS from a “data-to-information approach” to a “data-to-action approach,” therefore stressing the importance of reaching key stakeholders with information. The specific aims of this paper are to: identify the key issues that should be addressed in designing a Data Gathering Strategy for Water Security (DGSxWS); communicate the key issues with a clear conceptual framework; and suggest approaches and activities that could help water practitioners in dealing with the issues identified.
This study investigated the state of a service reservoir of a drinking water distribution network. Numerical simulation was applied to establish its flow pattern, mixing conditions, and free residual ...chlorine decay. The influence of the change in the water inlet configuration on these characteristics was evaluated. Four scenarios were established with different water level and flow rate as the differences between the first three scenarios. The fourth scenario was evaluated to assess the influence of the inlet configuration, momentum flow and water level on hydrodynamic conditions within the service reservoir. The distribution of four nozzles of 152.4mm diameter was identified as a viable measure to preserve the water quality in this type of hydraulic structures.
Operation and maintenance (O&M) of drinking water distribution networks (DWDNs) in tropical countries simultaneously face the control of acute and chronic risks due to the presence of microorganisms ...and disinfection by-products, respectively. In this study, results from a detailed field characterization of microbiological, chemical and infrastructural parameters of a tropical-climate DWDN are presented. Water physicochemical parameters and the characteristics of the network were assessed to evaluate the relationship between abiotic and microbiological factors and their association with the presence of total trihalomethanes (TTHMs). Illumina sequencing of the bacterial 16s rRNA gene revealed significant differences in the composition of biofilm and planktonic communities. The highly diverse biofilm communities showed the presence of methylotrophic bacteria, which suggest the presence of methyl radicals such as THMs within this habitat. Microbiological parameters correlated with water age, pH, temperature and free residual chlorine. The results from this study are necessary to increase the awareness of O&M practices in DWDNs required to reduce biofilm formation and maintain appropriate microbiological and chemical water quality, in relation to biofilm detachment and DBP formation.
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•Biofilms are not routinely monitored in drinking water networks.•The microbial ecology of a tropical water network was characterised by molecular methods.•In this study, key engineered factors and microbiological parameters correlated•Bacterial communities in bulk water were different from those in biofilms.•Biofilms must be monitored and controlled to preserve drinking water quality.
Nontuberculous mycobacteria (NTM) are ubiquitous microorganisms naturally resistant to antibiotics and disinfectants that can colonize drinking water supply systems. Information regarding the spread ...of NTM in specifically South America and Colombia is limited. We aimed to identify and characterize NTM present in tap water samples from Cali, Colombia. Drinking water samples and faucet biofilm swabs were collected in 18 places, including the city's three main water treatment plants (WTPs). Filter-trapped material and eluates (0.45 μm) from swab washes were plated in 7H11 agar plates. Suspected colonies were evaluated microscopically, and NTM species were identified based on the
gene. Antibiotic susceptibility testing was also performed. Fifty percent (9/18) of sampling points were positive for NTM (including two WTPs), from which 16 different isolates were identified:
(8/16),
(3/16),
(2/16),
(2/16), and
(1/16), all rapidly growing mycobacteria. A susceptibility profile was obtained from 68.75% (11/16) of the isolates.
was the most resistant species. All NTM isolated are potentially responsible for human diseases; our findings might provide a baseline for exploring NTM transmission dynamics and clinical characterization, as well as potential associations between NTM species found in drinking water and isolates from patients.
Biofilms in drinking water distribution networks (DWDNs) are recognized as potential pathogen reservoirs. Recent experiments have found that biofilm can also act as precursors for the formation of ...disinfection by-products (DBPs). This project aimed to better understand the impact of the presence of biofilms and improve prediction of DBPs in DWDNs. To study the microbial significance of biofilms in water pipes, bacterial communities in biofilm and bulk water were identified in a DWDN in a tropical climate country. Drinking water and biofilms were characterised by physico-chemical parameters. Relationships between biotic, physico-chemical parameters and engineered factors (i.e., pipe age, material and diameter; and water age) were explored by the application of statistical tests. Additionally, improvement of DBP prediction in DWDNs was approached by modelling the role of biofilms as DBP precursors. Two models for predicting DBP formation potentials were developed from chlorination of cells and extracellular polymeric substances. The first model corresponded to stagnant conditions and a second more complex model was produced for transitional and turbulent flow. The models were implemented in the software COMSOL Multiphysics 5.2a and sensitivity analysis was carried out to screen the parameters influence on the response variables. Field-work assessment allowed determining that biofilms are richer habitats than bulk water. Pipe age, pipe material, water age, free chlorine, pH and temperature can be key to the composition of bacterial communities. Model simulations suggested that the important DBP exposure is related to dichloroacetronitrile, stagnant bulk, and slow flow. The microbial and chemical significance of biofilms is important in the context of climate change and developing countries because water managers can face multiple challenges under these conditions. Alterations of raw water properties, increasing occurrence of extreme weather events and poor capacity to mitigate such events may rise the chemical and microbiological risk associated to biofilms in DWDNs in tropical countries.
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