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Water quality in distribution systems
\"Distribution systems represent the last barrier available to water systems to maintain safe and high-quality water, and this manual provides a 'first stop' for common distribution system water quality challenges. M68 offers practical guidance and best management practices for maintaining and improving distribution system water quality. It will help drinking water utilities and professionals understand the factors that affect water quality, ways to address them and best practices for optimizing distribution system water quality.\"-- Page [4] of cover.
Book
Graph Neural Networks for Pressure Estimation in Water Distribution Systems
Pressure and flow estimation in water distribution networks (WDNs) allows water management companies to optimize their control operations. For many years, mathematical simulation tools have been the most common approach to reconstructing an estimate of the WDNs hydraulics. However, pure physics‐based simulations involve several challenges, for example, partially observable data, high uncertainty, and extensive manual calibration. Thus, data‐driven approaches have gained traction to overcome such limitations. In this work, we combine physics‐based modeling and graph neural networks (GNN), a data‐driven approach, to address the pressure estimation problem. Our work has two main contributions. First, a training strategy that relies on random sensor placement making our GNN‐based estimation model robust to unexpected sensor location changes. Second, a realistic evaluation protocol that considers real temporal patterns and noise injection to mimic the uncertainties intrinsic to real‐world scenarios. As a result, a new state‐of‐the‐art model, GAT with Residual Connections, for pressure estimation is available. Our model surpasses the performance of previous studies on several WDNs benchmarks, showing a reduction of absolute error of ≈40% on average. Plain Language Summary Water management practitioners have resorted to mathematical simulation tools to reconstruct pressure, flow, and demand in order to improve their control operations. However, pure physics‐based methods need to deal with partially observable data, high uncertainty, and extensive manual calibration. We combine physics‐based modeling and graph neural networks, a data‐driven approach, to address the pressure estimation problem and overcome those limitations. Our work has two main contributions. First, a random sensor placement strategy makes our estimation model resilient to unexpected sensor location changes. Second, a realistic evaluation protocol that considers real temporal patterns and noise injection to mimic the uncertainties of real‐world scenarios. As a result, a new state‐of‐the‐art model, GAT with Residual Connections, for pressure estimation is available. Our model surpasses the performance of previous studies on several water distribution networks benchmarks, showing a reduction of absolute error of ≈40% on average. Key Points Mathematical Simulation Tools and graph neural networks were combined for pressure estimation in water distribution networks Random sensor placement during model training is a good strategy for robustness against unexpected sensors' location changes Time‐dependent patterns and Gaussian noise injection enable a realistic evaluation protocol for pressure estimation models
Journal Article
Seasonal Variation of Drinking Water Quality and Human Health Risk Assessment in Hancheng City of Guanzhong Plain, China
This research was conducted to understand the seasonal characteristics of water quality for domestic purpose in Hancheng City of the Guanzhong plain, China. The health risks were also assessed using the water quality monitoring data collected from the Hancheng Center for Disease Control and Prevention. For this study, 48 samples were collected from the drinking water distribution system (chlorinated water and terminal tap water) in the dry and wet seasons, and were analyzed for pH, total hardness (TH), total dissolved solids (TDS), Cl
−
, SO
4
2−
, F
−
, NH
4
-N, NO
3
-N, Cr
6+
, As, Hg and Mn. The water quality was assessed using the entropy water quality index (EWQI) and the results show that above 80% of the water samples are of good quality which is suitable for drinking and other domestic purposes. The potential non-carcinogenic risks of Cr
6+
, As, F
−
, and NO
3
-N and carcinogenic risks of Cr
6+
and As to consumers were assessed by the model recommended by the US Environmental Protection Agency (USEPA). The non-carcinogenic health risks in the dry season are higher than the risks in the wet season for both adults and children. Water quality indicators considered in the risk assessment contribute with different degrees to the total non-carcinogenic risk during the dry and wet seasons. The order of the average non-carcinogenic risk values of the chlorinated water and terminal tap water in the dry season was F
−
> As > NO
3
-N > Cr
6+
, while that in the wet season was F
−
> NO
3
-N > Cr
6+
> As. People face higher carcinogenic risk in the wet season in terms of terminal tap water consumption, while they face higher carcinogenic risk in the dry season in terms of the chlorinated water. Children face almost twice higher the carcinogenic risks than the adults.
Journal Article
Graph-Theoretic Framework for Assessing the Resilience of Sectorised Water Distribution Networks
Water utilities face a challenge in maintaining a good quality of service under a wide range of operational management and failure conditions. Tools for assessing the resilience of water distribution networks are therefore essential for both operational and maintenance optimization. In this paper, a novel graph-theoretic approach for the assessment of resilience for large scale water distribution networks is presented. This is of great importance for the management of large scale water distribution systems, most models containing up to hundreds of thousands of pipes and nodes. The proposed framework is mainly based on quantifying the redundancy and capacity of all possible routes from demand nodes to their supply sources. This approach works well with large network sizes since it does not rely on precise hydraulic simulations, which require complex calibration processes and computation, while remaining meaningful from a physical and a topological point of view. The proposal is also tailored for the analysis of sectorised networks through a novel multiscale method for analysing connectivity, which is successfully tested in operational utility network models made of more than 100,000 nodes and 110,000 pipes.
Journal Article
Review of model-based and data-driven approaches for leak detection and location in water distribution systems
Leak detection and location in water distribution systems (WDSs) is of utmost importance for reducing water loss, which is, however, a major challenge for water utility companies. To this end, researchers have proposed a multitude of methods to detect such leaks in WDSs. Model-based and data-driven approaches, in particular, have found widespread uses in this area. In this paper, we reviewed both these approaches and classified the techniques used by them according to their leak detection methods. It is seen that model-based approaches require highly calibrated hydraulic models, and their accuracies are sensitive to modeling and measurement uncertainties. On the contrary, data-driven approaches do not require an in-depth understanding of the WDS. However, they tend to result in high false positive rates. Furthermore, neither of these approaches can handle anomalous variations caused by unexpected water demands.
Journal Article
Out of the mainstream : water rights, politics and identity
\"Water is not only a source of life and culture. It is also a source of power, conflicting interests and identity battles. Rights to materially access, culturally organize and politically control water resources are poorly understood by mainstream scientific approaches and hardly addressed by current normative frameworks. These issues become even more challenging when law and policy-makers and dominant power groups try to grasp, contain and handle them in multicultural societies. The struggles over the uses, meanings and appropriation of water are especially well-illustrated in Andean communities and local water systems of Peru, Chile, Ecuador, and Bolivia, as well as in Native American communities in south-western USA. The problem is that throughout history, these nation-states have attempted to 'civilize' and bring into the mainstream the different cultures and peoples within their borders instead of understanding 'context' and harnessing the strengths and potentials of diversity. This book examines the multi-scale struggles for cultural justice and socio-economic re-distribution that arise as Latin American communities and user federations seek access to water resources and decision-making power regarding their control and management. It is set in the dynamic context of unequal, globalizing power relations, politics of scale and identity, environmental encroachment and the increasing presence of extractive industries that are creating additional pressures on local livelihoods. While much of the focus of the book is on the Andean Region, a number of comparative chapters are also included. These address issues such as water rights and defence strategies in neighbouring countries and those of Native American people in the southern USA, as well as state reform and multi-culturalism across Latin and Native America and the use of international standards in struggles for indigenous water rights. This book shows that, against all odds, people are actively contesting neoliberal globalization and water power plays. In doing so, they construct new, hybrid water rights systems, livelihoods, cultures and hydro-political networks, and dynamically challenge the mainstream powers and politics.\"--Publisher's description.
Book
Microbial analysis of in situ biofilm formation in drinking water distribution systems: implications for monitoring and control of drinking water quality
Biofilm formation in drinking water distribution systems (DWDS) is influenced by the source water, the supply infrastructure and the operation of the system. A holistic approach was used to advance knowledge on the development of mixed species biofilms in situ, by using biofilm sampling devices installed in chlorinated networks. Key physico-chemical parameters and conventional microbial indicators for drinking water quality were analysed. Biofilm coverage on pipes was evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The microbial community structure, bacteria and fungi, of water and biofilms was assessed using pyrosequencing. Conventional wisdom leads to an expectation for less microbial diversity in groundwater supplied systems. However, the analysis of bulk water showed higher microbial diversity in groundwater site samples compared with the surface water site. Conversely, higher diversity and richness were detected in biofilms from the surface water site. The average biofilm coverage was similar among sites. Disinfection residual and other key variables were similar between the two sites, other than nitrates, alkalinity and the hydraulic conditions which were extremely low at the groundwater site. Thus, the unexpected result of an exceptionally low diversity with few dominant genera (Pseudomonas and Basidiobolus) in groundwater biofilm samples, despite the more diverse community in the bulk water, is attributed to the low-flow hydraulic conditions. This finding evidences that the local environmental conditions are shaping biofilm formation, composition and amount, and hence managing these is critical for the best operation of DWDS to safeguard water quality.
Journal Article