An Approach to Determine Risk Indices for Drinking Water–Study Investigation

Method for Determining the Probability of a Lack of Water Supply to Consumers

The water distribution subsystem is the most failing subsystem included in the water supply system. One of the main consequences of water supply failures is the lack of water supply to consumers, which is always very onerous. The paper presents a method of determining the conditional probability that a break in the supply of water to consumers of a certain duration will be caused by a specific type of failure. The result of the work was to identify water supply network failures that result in the longest water supply suspension time. The method was presented on a real water supply system. In order to reduce the incidence of long-term interruptions in water supply, water supply companies should mainly continue replacing gray cast iron pipes with thermoplastic materials. Actions taken to increase the safety of drinking water supply meet the current standards for the safety of drinking water, developed by the World Health Organization and the European Union.

Use of the Life Cycle Methodology to Calculate Energy Consumption of Urban Water Cycle: A Case Study of Ordos City

Water resources and energy constitute two broad categories of resources required for social and economic development. The water-energy nexus has become a focus of research in recent years. Although water resources are closely related to energy systems, the processes involved remain incompletely understood due to the diversity and complexity of energy types, processes, and consumption sectors. This study aimed to accurately calculate the energy demand of water resources and to identify an effective method of improving the energy utilization efficiency of water. The life cycle of water resources was divided into five stages based on the life cycle methodology: (1) extraction, (2) purification, (3) transportation, (4) utilization, (5) sewage treatment. The quantity and characteristics of energy consumed in each stage were studied, and an equation to calculate energy consumption for each stage was proposed. Using the city of Ordos in Northwest China as an example, energy consumption of water resources from 2013 to 2017 was analyzed. The results showed that from 2013 to 2017, energy consumption and per unit energy consumption of water resources in Ordos decreased by 33.3% and 30.6% from 1.62 × 108 kWh to 1.08 × 108 kWh and from 10.11 kWh·m−3 to 7.02 kWh·m−3, respectively. The majority of energy consumption over the entire life cycle of water resources occurred during the utilization stage at a proportion of total energy consumed of ~95%. Use of water for thermal power generation was identified as the single largest consumer of energy and, therefore, has the greatest potential for energy saving.

A randomized, double-blind water taste test to evaluate the equivalence of taste between tap water and filtered water in the Taipei metropolis

High water quality and sufficient water availability are the main concerns of water users. Promoting the efficient use of tap water can contribute to sustainable drinking water management and progress towards Sustainable Development Goals. In many metropolises, water suppliers treat municipal water with appropriate treatment processes and well-maintained distribution infrastructure. Under this circumstance, it is acceptable that municipal water can be a source of drinking water. The presence of residual chlorine in tap water, connected to municipal water supply, inactivates pathogenic microorganisms and prevents recontamination. However, adding chlorine to tap water may affect the organoleptic properties of drinking water. On the other hand, the use of point-of-use (POU) water dispensers, which provides an additional treatment step on tap water, is not energy-efficient. A randomized, double-blind water taste test was conducted in the Taipei metropolis to assess whether tap water from public drinking fountains and filtered water from POU water dispensers have similar organoleptic properties. An odds ratio (OR) and the area under the receiver operating characteristic curve (AUC) were used to measure the participants' ability to distinguish between the two water varieties. A five-region hypothesis test was conducted to test the OR, and a 95% bootstrap confidence interval of the AUC was calculated. The results of the study showed that the 95% five-region confidence interval of OR equal to (0.5, 1.49), and the 95% bootstrap confidence interval of AUC equal to (0.42, 0.56). These results implied that people in the Taipei metropolis could not distinguish between tap water and filtered water. It is recommended that more drinking fountains be installed and maintained fully functional and clean to achieve excellence in tap water access.

Modeling Future Streamflow for Adaptive Water Allocation under Climate Change for the Tanjung Karang Rice Irrigation Scheme Malaysia

Spatial and temporal climatic variability influence on the productivity of agricultural watershed and irrigation systems. In a large irrigation system, the quantification and regulation of the flow at different locations of the channel is quite difficult manually, leading to a poor delivery of supply and demand. Water shortage is a crucial issue due to mismatch between available water and demand at intake point of Tanjung-Karang Irrigation Scheme. This study assessed the potential impacts of climate change on basin outflow for 2010–2039, 2040–2069, and 2070–2099 to the baseline period (1976–2005) and used it as input hydrograph to simulate river discharge. A Hydrologic Engineering Corps Hydrologic Modeling System (HEC-HMS) model driven by projections from ten global climate models (GCMs) with three scenarios (Representative Concentration Pathways (RCPs) 4.5, 6.0, and 8.5) used to simulate the outflow and the Hydrologic Engineering Centers River Analysis System (HEC-RAS) model applied for hydraulic modeling. The projected seasonal streamflow showed a decreasing trend for future periods. The average available irrigation supply for historical period is 15.97 m3/s, which would decrease by 12%, 18%, and 21% under RCPs 4.5, 6.0, and 8.5, respectively. Projected irrigation supply showed oversupply and undersupply to the required supply during the growing season. Simulated discharge could therefore be incorporated into cropping practices to boost the sustainable distribution of water under the new realities of climate change in the future.

Assessment of Ecological Efficiency and Environmental Sustainability of the Minjiang-Source in China

Ecological sustainability is treated as a main reflection of the synergy among social development, economic growth and environmental protection, while ecological efficiency is an index used to reflect the sustainable development of the ecological environment. The super efficiency model with undesirable outputs (SE-SBM) model was applied to measure the eco-efficiency of the 12 counties in the Minjiang-Source, China, in 2005–2017. The spatial and temporal evolution and spatial differentiation of the eco-efficiency were analyzed. The results showed that the eco-efficiency of 67.7% of the 12 counties remains at a low level but with an increasing trend. A typical spatial aggregation effect was found with the characteristics of “high in the east and low in the west”. The Malmquist-Luenberger index shows a trend of fluctuation with the same trend between scale efficiency and technical efficiency changes. The results proved the positive effect of technological progress on local eco-efficiency. Environmental regulation has a positive impact on eco-efficiency in the short term and an inhibition effect in the long run. Hence, technological innovation and industrial adjustment will be an effective way to improve the eco-efficiency of the Minjiang-Source and promote its sustainability.

Water Network-Failure Data Assessment

The water-supply system is one of the basic and most important critical infrastructures. Water supply service disruption (water quality or quantity) may have serious consequences in modern societies. Water supply service is subject to various failure modes. Failure modes are specified by their degradation mechanisms, criticality, occurrence frequency and intensity. These failure modes have a random nature that impacts on the network disruption indicators, such as disruption frequency, network downtime, network repair time and network back-to-service time, i.e., the network resilience. This paper focuses on the water leakage failure mode. The water leakage failure mode assessment considers the unavoidable annual real water losses and the infrastructure leakage index recommended by the International Water Association’s Water Loss Task Force specialist group. Probabilistic statistical modelling was implemented to assess the seasonal index, the failure rates and the expectation value of the “mean time between failures.” The assessment is based on real operational data of the network. Specific attention is paid to the sensitivity of failures to seasonal variations. The presented methodology of the analysis of the water leakage failure mode is extendable to other failure modes and can help in developing new strategies in the management of the water-supply system in normal operation and crisis situations.

Pressure Regulation vs. Water Aging in Water Distribution Networks

In this paper, the effects of pressure regulation in a water distribution network (WDN) are being examined. Quality is hammered the most when pressure is reduced in a WDN and this occurs due to the increase in the age of water flowing inside the network pipes (water age is actually the total time the water remains inside the pipes before reaching the customer’s tap). Kos town WDN is used as the case study network. Kos town is the capital of the homonymous Greek island, among the most famous and popular of the Greek islands. The specific WDN is quite typical but very interesting, as it is extended along the seafront. The network’s hydraulic simulation model was developed through the WaterCad V8i software. As Kos experiences too high-water demand peaks and lows during summer and winter time, respectively, its WDN has already been thoroughly studied, in order to regulate the pressure and reduce its annual water loss rates. Nevertheless, these scenarios have never been examined regarding the impact on water quality. In the current study, the division of the WDN in District Metered Areas (DMAs) and the use of a Pressure Reducing Valve (PRV) in the entering node of each DMA are being evaluated in terms of water age. Additionally, a swift optimization process takes place to produce different DMAs’ borders, based on the criteria of minimum nodal water age, instead of optimal pressure. Different scenarios were tested on the calibrated and validated hydraulic model of Kos town WDN.

Optimization of the Design of Water Distribution Systems for Variable Pumping Flow Rates

Water supply systems need to be designed in an efficient way, accounting for both construction costs and operational energy expenditures when pumping is required. Since water demand varies depending on the moment’s necessities, especially when it comes to agricultural purposes, water supply systems should also be designed to adequately handle this. This paper presents a straightforward design methodology that using a constant flow rate, the total cost is equivalent to that of the variable demand flow. The methodology is based on the Granados System, which is a very intuitive and practical gradient based procedure. To adapt it to seasonal demand, the concepts of Equivalent Flow Rate and Equivalent Volume are presented and applied in a simple case study. These concepts are computationally straightforward and facilitate the design process of hydraulic drives under demand variability and can be used in multiple methodologies, aside from the Granados System. The Equivalent Flow Rate and Equivalent Volume offer a solution to design procedures that require a constant flow regime, adapting them to more realistic design situations and therefore widening their practical scope.

Chloramine Disinfection-Induced Nitrification Activities and Their Potential Public Health Risk Indications within Deposits of a Drinking Water Supply System

Microsensors were applied to study the diffusion reaction and activity of a nitrogen species of deposit sediment from a drinking water supply system. Microprofiles of dissolved oxygen (DO), NH₄⁺-N, NO₃^--N, and NO₂^-N in the sediment indicated that the DO concentration decreased from the highest at the sediment surface to zero at the bottom of the sediment. Similarly, with the increase of depth, NH₄⁺-N initially increased rapidly and then decreased slowly, while the concentration of NO₃^--N reached a maximum at around 6000 μm and then decreased to about 0.1 mg·L^-1 near the bottom of the sediment. Almost no change was observed for NO₂^--N. The decrease of NH₄⁺-N and DO corresponded well with the increase of NO₃^--N. Furthermore, based on a consumption and production rate analysis, DO has always been consumed; the NH₄⁺-N consumption rate increased rapidly within 0-1000 μm, reaching about 14 mg·L^-1·S^-1·10^-9. A small amount of NH₄⁺-N was produced in 2000-6000 μm, which could be attributed to denitrification activity. There was no change deeper than 6000 μm, while NO₃^--N was produced at a depth between 0 and 6000 μm and was consumed in the deeper zone. At the depth of 9000 μm, the NO₃^--N consumption reached a maximum of 5 mg·L^-1·S^-1·10^-9. The consumption of DO and NH₄⁺-N, which corresponded with the production of NO₃^--N in a specific microscale range within the sediment, demonstrated nitrification and denitrification activities. In addition, the time required for the diffusion of only DO, NH₄⁺-N, NO₃^--N, and NO₂^--N was estimated as 14 days; however, in the practical, even after 60 days of operation, there was still a continuous reaction, which provided further evidence towards microbial activities within the sediment.

Efficiency Analysis of the Input for Water-Saving Agriculture in China

To optimize the installation distribution of water-saving techniques and improve the efficiency of water-saving agricultural inputs, we used a three-stage data envelopment analysis (DEA) model and Chinese provincial panel data from 2014 to 2016 to analyze the input efficiency of the water-saving irrigation. This study explores the efficiency derived from the efforts of water-saving initiatives in the agricultural sector in China. We present the impacts of factors such as technology, scale, diminishing marginal revenue, and crop water requirements on the research results. We found overall efficiency of water-saving irrigation is increasing nationally. The efficiency of water-saving irrigation input will significantly increase if management and organization of the input improve. Increasing the investment in areas with increasing marginal revenue would improve the local agricultural water-saving input efficiency in areas such as Hainan, Chongqing, Guizhou, Tibet, and Qinghai; although in areas with large water requirement for major crops, such as Inner Mongolia and Xinjiang, the efficiency of water-saving irrigation is generally high. Shanxi requires a large amount of water as the efficiency of agricultural water-saving input is 0.07, which is relatively lower than the average efficiency of all regions (0.39). The cultivated area index and the GDP per capita had no significant effect on the irrigation input efficiency.

Reduction of Potable Water Consumption and Sewage Generation on a City Scale: A Case Study in Brazil

This article aims to estimate the reduction of potable water consumption and sewage generation in the city of Joinville, southern Brazil. Four strategies were considered to promote potable water savings: replacement of conventional toilets with dual-flush ones, greywater reuse, rainwater harvesting, and the combination of these three strategies. Residential, public, and commercial sectors were assessed. The potential for potable water savings ranged from 1.7% to 50.5%, and the potential for sewage generation reduction ranged from 2.1% to 52.1%. The single-family residential sector was the most representative for water savings and sewage generation reduction. The public sector would be the least contributor to such reductions. It was found that in the city of Joinville, for low non-potable water demands, greywater reuse was the most viable strategy to save water. When non-potable demand is high and there is a large catchment area, it is recommended to install rainwater harvesting systems. It was concluded that there is a high potential for potable water savings and reduction of sewage generation if measures were adopted in Joinville, but it is necessary to evaluate which strategy is the most appropriate for each building.

Feasibility Assessment of a Water Supply Reliability Index for Water Resources Project Planning and Evaluation

In order to estimate water supply potential, the effects of shortages on water users, and the uncertainty of local headspring conditions during the planning stage of reservoir construction, the Shortage Index (SI) is often employed. However, the criterion used in the SI is difficult to adjust to satisfy local conditions and objectives. The SI also employs an ambiguous definition of value. Thus, this study adopted a water supply reliability index (WSRI) as an alternative to the SI for providing the criterion for water resources project planning. The value of the WSRI is easily understood, because it is defined according to the real water supply situation and it has a strong linear relationship with values of SI. For any given water supply system, the estimated results derived from this study could serve as an additional remark on different SI values to explain the relevant water supply considerations. In addition, for a new planning site, the estimated results of this study could provide another way for engineers to evaluate the maximum water supply capability. Consequently, an interesting avenue of investigation in future research would be the incorporation of the WSRI with the risk of deficit frequency in establishing an efficient and transparent bottom-up approach for water resources management, involving all the relevant stakeholders.

Development of Failure Cause–Impact–Duration (CID) Plots for Water Supply and Distribution System Management

Understanding the impact and duration (consequences) of different component failures (cause) in a water supply and distribution system (WSDS) is a critical task for water utilities to develop effective preparation and response plans. During the last three decades, few efforts have been devoted to developing a visualization tool to display the relationship between the failure cause and its consequences. This study proposes two visualization methods to effectively show the relationship between the two failure entities: A failure cause–impact–duration (CID) plot, and a bubble plot. The former is drawn for an effective snapshot on the range (extent) of failure duration and the impact of different failures, whereas the latter provides failure frequency information. A simple and practical failure classification system is also introduced for producing the two proposed plots effectively. To verify the visualization schemes, we collected records of 331 WSDS component failures that occurred in South Korea between 1980 and 2018. Results showed that (1) the proposed CID plot can serve as a useful tool for identifying most minor and major WSDS failures, and (2) the proposed bubble plot is useful for determining significant component failures with respect to their failure consequences and occurrence likelihoods.

Study on the Evolution of Water Resource Utilization Efficiency in Tibet Autonomous Region and Four Provinces in Tibetan Areas under Double Control Action

Tibet is the province with the largest international rivers and water resource reserves in China. However, due to its special ecological environment, the utilization of water resources has become an inevitable problem. Considering the undesirable outputs in water resource utilization, the Super-efficiency Slack-based Measure (SE-SBM) model is used to measure water utilization efficiency of Tibet and the Tibetan areas (four provinces where Tibetan areas are located) from 2006 to 2016. The mixed and random panel Tobit model is used to investigate the driving factors of water efficiency and a horizontal comparison between provinces is made on this basis. The results show that the water utilization efficiency of Tibet and the Tibetan areas in four provinces shows a “U-shaped” trend. The water utilization efficiency of most provinces is greater than or close to 1 and the water utilization efficiency of each province shows a constant convergence trend. Environmental regulation and technological innovation have a significant positive effect on water utilization efficiency. Urbanization and foreign direct investment (FDI) have a significant negative effect on water utilization efficiency. Per capita Gross Domestic Product (GDP) and water resource endowment have no significant effect on water utilization efficiency. It is necessary to select a new type of urbanization suitable for the Tibetan Plateau, eliminate the backward production capacity, high water consumption, or high emissions industries, and to strengthen the research and development of water-saving and emission-reduction technology innovation in Tibet.