Intermittent Water Supply Systems Research Articles

Study of domestic water consumption in intermittent supply of the Riberas de Sacramento sector in Chihuahua, Mexico

Abstract User water demand can be met in intermittent water supply systems, and normally it is met if they have sufficient capacity to store water in their homes to be used in the hours when it is not supplied from the public pipe network. The situation in many intermittent water supply systems is that they have enough water to cover the demand of the users but are supplying it intermittently, and the challenge is to achieve a transfer from intermittent to continuous supply. If the delivery of water is continuous, which supplies drinking water 24/7, it covers not only the basic needs of the user, but all the needs for water they may have. The present study was carried out using smart domestic water meters to obtain consumption information in an intermittently supplied pilot sector. The electromagnetic meters record the water flow through pulses and generate consumption information, which gives us the consumption pattern in volume of water and in the time it is used. During the study, multivariate statistical methods were applied to obtain information from the domestic meters and to identify, as realistically as possible, the consumption of drinking water and the relationship between consumption and specific characteristics of the users and thus anticipate future demand. The results showed a close relationship between consumption and the size of the residence. The most influential factors were the number of bathrooms and the number of occupants. A direct relationship between the pressure and the volume supplied was presumed at the beginning of the study but the opposite was found. Equipment was installed to measure the pressure in the network at the time of establishing the continuous supply of drinking water. The multivariate analysis provides a selection of the most important variables that influence and explain the behavior of the water use and consumption pattern, with the operation determined by the operating agency.

Mapping and Visualizing Global Knowledge on Intermittent Water Supply Systems

Intermittent water supply systems (IWSSs) are prevalent in most developing countries and some developed ones. Their usage is driven by necessity rather than as a principal objective, mostly due to technical and economic deficiencies. Major health risks and socio-economic inequities are associated with such systems. Their impacts are aggravated by climate changes and the COVID-19 crisis. These are likely to have profound implications on progress toward advancing sustainable development goals (SDGs). Motivated by providing a comprehensive overview of global knowledge on IWSSs, the present work proposed to track and analyze research works on IWSSs utilizing bibliometric techniques and visual mapping tools. This includes investigating the trends and growth trajectories of research works on IWSSs and analyzing the various approaches proposed to expand our understanding with respect to the management, modeling, optimization, and impacts of IWSSs. The national and international contributions and collaboration figures are further analyzed at country, institution, author, and source levels. This analysis indicates that research works conducted on IWSSs have certain expectations in terms of productivity (total global productivity; 197 documents). The United States was the best country in terms of productivity (58 documents; 29.4%), while the Water Switzerland journal was the most productive journal (19 documents; 9.6%). The impacts of IWSSs on health and well-being have attracted considerable attention. The outcomes showed deep and justified worries in relation to the transition from intermittent to continuous supply, equity, and mitigating the health risks associated with IWSSs in the foreseen future. The utilization of artificial intelligence techniques and expert systems will drive and shape future IWSS-related research activities. Therefore, investments in this regard are crucial.

Development of scenarios for evaluating conversion from intermittent to continuous water supply strategies’ sustainability implications

ABSTRACT Planning the conversion from intermittent to continuous water supply (CWS) is rife with uncertainties. Although scenarios can be used to incorporate uncertainties in planning processes, their development and application to intermittent water supply systems are uncommon. Using drivers of water demand in water supply systems, this study developed four scenarios (business-as-usual, consumption demand management, non-revenue water (NRW) management, and holistic) for water supply systems. The scenarios were applied to the Lusaka water supply network in Zambia. The results showed that the NRW management scenario, which used the projections in the water supply investment master plan for Lusaka, is unsustainable because of insufficient water as the 15% NRW target is practically unattainable by 2035. The holistic scenario is the most sustainable, but the commitment to ensure its occurrence in Zambia is currently lacking. Possibly, donors’ directives can instil the commitment needed to attain the holistic scenario and the conversion to CWS.

Wireless Sensors for Measuring Drinking Water Quality in Building Plumbing: Deployments and Insights from Continuous and Intermittent Water Supply Systems

Wireless Sensors for Measuring Drinking Water Quality in Building Plumbing: Deployments and Insights from Continuous and Intermittent Water Supply Systems

Effect of operational strategies on microbial water quality in small scale intermittent water supply systems: The case of Moamba, Mozambique.

Intermittent drinking water supply affects the health of over 300 million people globally. In Mozambique, it is largely practiced in cities and small towns. This results in frequent microbial contamination of the supplied drinking water posing a health risk to consumers. In Moamba, a small town in Southern Mozambique with 2,500 water connections, the impact of changes in operational strategies, namely increased chlorine dosage, increased supply duration and first-flush, on the microbial water quality was studied to determine best practices. To that aim, water quality monitoring was enhanced to provide sufficient data on the microbial contamination from 452 samples under the different strategies. The water at the outlet of the water treatment plant during all strategies was free of E. coli complying to the national standards. However, E. coli could be detected at household level. By increasing the chlorine dosage, the number of samples that showed E. coli absence increased at the two sampling locations in the distribution network: in Cimento from 72% to 83% and in Matadouro from 52% to 86%. Modifying the number and duration of supply cycles showed a different impact on the water quality at both locations in the distribution network. A positive effect was shown in Cimento, where the mean concentrations decreased slightly from 0.54 to 0.23CFU/100mL and 16.7 to 7.3CFU/100mL for E. coli and total coliforms respectively. The percentage of samples positive for bacteria was, however, similar. In contrast, a negative effect was shown in Matadouro where the percentage of positive samples increased and the mean bacterial concentrations increased slightly: E. coli from 0.9 to 1.5CFU/100mL and total coliforms 17.6 to 23.0CFU/100mL. Enhanced water quality monitoring improved operational strategies safeguarding the microbial water quality. The E. coli contamination of the drinking water at household level could point at recontamination in the distribution or unsafe hygienic practices at household level. Presence of faecal contamination at household level indicates potential presence of pathogens posing a health risk to consumers. Increasing chlorine dosage ensured good microbiological drinking water quality but changing the number of supply cycles had no such effect.

Multivariate analysis of the pressure variation in intermittent water supply systems and the impact on demand satisfaction

Abstract In intermittent drinking water distribution systems, large volumes of the water are wasted due to leaks in the distribution networks. Similarly, user service is not always satisfied in the time required to fill the storage, nor with sufficient pressure. Hence the importance of this study. Measuring the variability of pressure in the distribution network and determining the factors that influence the definition of a sufficient minimum hours of service, is a first step to change to a continuous service 24/7, in order to minimize the volumes of lost water and meet demand. In total, 347 pressure sensors were placed in a network to detect changes in pressure and obtain data for 3 years. This study presents a new approach to determine the operating policy of the operating agency that provides the service intermittently. Two objectives are pursued: pressure variability – to minimize leaks – and define the minimum hours of service. The analysis was performed using multivariate statistical techniques, including principal component analysis, correlation matrix and ANOVAs, to explore the association between objectives. The results obtained show that the pressure distribution has a Gaussian behavior and that the hours of service have a Poisson distribution.

Intermittent water supply systems and their resilience to COVID-19: IWA IWS SG survey

Abstract There is limited information about the current state of intermittent water supply (IWS) systems at the global level. A survey was carried out by the Intermittent Water Supply Specialist Group of the International Water Association (IWA IWS SG) to better understand the current state of these systems and challenges that water companies may have faced under COVID-19 pandemic and to capture successful management strategies applied by water utilities. The survey consisted of three parts: (1) general information about IWS systems, (2) current state of IWS and (3) resilience of IWS under COVID-19 conditions, as well as some questions about potential interventions in order to improve system performance in general and under future uncertain conditions. The survey responses were evaluated based on the Safe & SuRe resilience framework, assessing measures of mitigation, adaptation, coping and learning, and exploring organisational and operational responses of IWS utilities. Infrastructure capacity and water resources availability were identified as the main causes of intermittency in most water distribution systems, while intermittent electricity was considered as the main external cause. Participants indicated that some risk assessment process was in place; however, COVID-19 has surpassed any provisions made to address the risks. Lessons learnt highlighted the importance of financial resources, e-infrastructure for efficient system operation and communication with consumers, and the critical role of international knowledge transfer and the sharing of best practice guidelines for improving resilience and transitioning towards continuous water supply.

Source to Tap Risk Assessment for Intermittent Water Supply Systems in Arid Regions: An Integrated FTA-Fuzzy FMEA Methodology.

Water utilities in arid regions deal with multifaceted issues of natural groundwater contamination, high treatment costs, and low water rates. These utilities rely on intermittent supplies resulting in numerous water quality failures at source, treatment, distribution, and in-house plumbing systems. The present research presents an inclusive risk assessment methodology for managing water quality from source to tap. Three-year monitoring data for turbidity, TDS, pH, iron, ammonia, nitrates, residual chlorine, Coliform group, E. coli, and Fecal Streptococci identified the root causes of failures. The cause-effect relationships in the form of a fault tree were solved using multiple failure modes and effect analysis (FMEA) to handle both the Boolean operations. The fuzzy sets addressed the uncertainties associated with data limitations in calculating exceedance probabilities (Pe) and vagueness in expert opinion for subjective evaluation of severity and detectability. The methodology was applied on a smaller system serving 18,000 consumers in Qassim, Saudi Arabia. Potable supplied water underwent reoccurrence of TDS (Pe = 20%), turbidity (Pe = 10%), and Fe (Pe = 2%) failures in distribution that further increased up to 44%, 33%, and 11% at the consumer end. The Pe for residual chlorine failure soared up to 89%. Economic controls reduced the cumulative risk to 50%, while the shift to continuous supply can limit the remaining failures under the acceptable risk. The framework will help utilities manage water quality in intermittent systems from source to tap in Saudi Arabia, the Gulf, and elsewhere.

Intermittent Water Supply Management, Household Adaptation, and Drinking Water Quality: A Comparative Study in Two Chinese Provinces

Intermittent water supply (IWS) is a relatively common phenomenon across the world as well as in rural and peri-urban areas across China, though there has been little IWS-focused research from China published to date. IWS consumers typically adopt a range of strategies to cope with insufficient water supply, poor drinking water quality, and associated inconveniences. In this study, we collected a range of data from small-scale utilities and households in two IWS systems and two continuous water supply (CWS) systems, as well as from comparison groups, in Shandong and Hubei provinces. Data collection included water quality testing, interviews, and surveys on behavioral adaptations, coping strategies, water-related health perceptions, and other metrics of consumer satisfaction. Overall, we found that the IWS coping strategies employed in northern China (Shandong) were associated with generally safe, but inconvenient, water access, whereas adaptation strategies observed in southern China (Hubei) appeared to improve convenience, but not water quality. Compared to the CWS comparison groups, we did not observe significant differences in water- and sanitation-related behaviors in the IWS groups, suggesting interventions to increase adaptive and protective behaviors at the household level might further improve safe water access for households living with IWS. Overall, although the water supply infrastructure in these study areas appeared to be in relatively good condition, in contrast to reported data on IWS systems in other countries, we observed multiple risk factors associated with the water treatment and distribution processes in these IWS systems. Among policy recommendations, our results suggest that the implementation of Water Safety Plans in China would likely improve the management of drinking water treatment and, by extension, safe drinking water supply under conditions of IWS.

Multi-objective optimization for improving equity and reliability in intermittent water supply systems

Abstract Intermittent water systems suffer from several drawbacks such as unfair distribution among users, low reliability and poor water quality. Given limited water and financial resources, making decisions for improving intermittent water supply (IWS) becomes a complex process. The paths to continuous supply are a priori undefined, however, the provision of efficient service is crucial. In the scientific literature, limited research addresses how to improve intermittent systems, to enhance the current service while transitioning to continuous supply. A multi-objective optimization (MOO) tool using a genetic algorithm has been developed to assist in investment decision-making. This approach uses multiple cost-effective intervention options to maximize equity and reliability while minimizing cost implications in an IWS system. The costs in such interventions include expenditure on pipe replacement, booster pump and elevated tank installation. The approach was first tested on a benchmark Hanoi synthetic network, and then applied to the water distribution network of Milagro (Ecuador). The developed tool reveals the extent to which equity and reliability can be driving objectives, and how they can be factored into decision-making. The application of the MOO tool in intermittent systems in order to improve existing distribution networks with strategic infrastructure addition can provide greater equity and reliability.

Managing Water Quality in Intermittent Supply Systems: The Case of Mukono Town, Uganda

Intermittent water supply networks risk microbial and chemical contamination through multiple mechanisms. In particular, in the cities of developing countries, where intrusion through leaky pipes are more prevalent and the sanitation systems coverage is low, contaminated water can be a public health hazard. Although countries using intermittent water supply systems aim to change to continuous water supply systems—for example, Kampala city is targeting to change to continuous water supply by 2025 through an expansion and rehabilitation of the pipe infrastructure—it is unlikely that this transition will happen soon because of rapid urbanisation and economic feasibility challenges. Therefore, water utilities need to find ways to supply safe drinking water using existing systems until gradually changing to a continuous supply system. This study describes solutions for improving water quality in Mukono town in Uganda through a combination of water quality monitoring (e.g., identifying potential intrusion hotspots into the pipeline using field measurements) and interventions (e.g., booster chlorination). In addition to measuring and analyses of multiple chemical and microbial water quality parameters, we used EPANET 2.0 to simulate the water quality dynamics in the transport pipeline to assess the impact of interventions.

Demand Satisfaction as a Framework for Understanding Intermittent Water Supply Systems

AbstractNearly one billion people worldwide receive water through piped networks that are not continually pressurized and operate intermittently. The prevalence and persistence of these Intermittent Water Supplies (IWS) is surprising as this mode of operation induces water contamination and customer equity issues. Shortages of source water, customers' water demand, and leaking pipes are frequently cited as necessitating IWS. We propose a framework for understanding the persistence and operation of IWS. The supply system is represented by an average customer and a spatially averaged leakage rate. With this macroscopic hydraulic model, we relate customer demand satisfaction, source water availability, customer demand, and leakage. While this approach ignores the complexities of network topology, we find that the model approximates real systems well (calibrating to four intermittent reference networks achieved R2>0.94). The calibrated model is robust to moderate changes in demand and leakage (maintaining R2>0.83). Using the model, we show that the tipping point between satisfied demand and unsatisfied demand is a local optimum for utilities, which may explain the persistence of IWS. Beyond this point, the volume received by customers does not increase, but utilities must supply more water to the network. The generality of the proposed model enables its use when regulating and upgrading IWS. We demonstrate the latter by critiquing a performance‐based contract that was intended to improve an intermittent supply in India. Demand satisfaction has profound implications for hydraulics and human welfare. We propose the degree of demand satisfaction as a metric for evaluating IWS and for tracking the United Nations Sustainable Development Goal 6.1.

An Assessment of Groundwater Grab Syndrome in Langata Sub County, Nairobi City-Kenya

Interest on the investigation of groundwater depletion threat is growing globally and Langata sub County in Nairobi, the capital city of the Republic of Kenya, is not an exception. Because of drought-induced water shortage, households in Langata do rely on borehole water to augment their intermittent municipal water supply system. Consequently, there is an upsurge of borehole developments as drought events unfold. Previous studies here have focused on impact of borehole depths and density yet little seems to have been done to compute the correlation coefficient between drought events data and historical borehole development records as an assessment for groundwater “grab” syndrome. This study used drought index computation method (SPI) alongside other statistical methods to seek the answer to the problem. Using 57 years of monthly rainfall data and 26 years of borehole development data, the study established that, there is a positive correlation coefficient. Similarly, a trend analysis of borehole drilling and struck water level depths indicated a positive parallel rising trend on both. Further, when the borehole distribution map and struck water level contour maps were plotted, a sign of a probable well interference during pumping was detected, which however, requires a new investigation to confirm the syndrome of groundwater depletion threat. The study has contributed to the groundwater depletion research by deploying statistical research methods for risk detection. Finally, the study has proposed for a new groundwater management policy that will encourage initiation of artificial recharge schemes for the study site and beyond.

Data logger-based measurement of household water consumption and micro-component analysis of an intermittent water supply system

Abstract Although household water consumption in intermittent water supply (IWS) systems has been estimated through retrospective surveys, structured observations, storage inventories, (limited) metered data, and flowmeters, either exclusively or in combination, these methods are resource-intensive, difficult to standardize, and/or impractical to generalize. To overcome these shortcomings, an original method that employed high-accuracy data loggers to continuously measure the water level in rooftop water tanks at intervals of 30 s for a week in 28 households in the Kathmandu Valley, Nepal was verified. The hourly and daily water consumption was calculated using the logged reduction in water level. With 98% median accuracy of determining overall water consumption, average daily water consumption was calculated as 56 L/capita/day. In addition, applying pattern recognition techniques, the water level profiles of various water uses were paired with household water use records to estimate the micro-components. The toilet (31%) was the highest water-consuming use, followed by the kitchen (27%), laundry (16%), shower (13%), and other activities (13%). Measuring water consumption using data loggers is a nondestructive method easily applicable to all IWS systems using rooftop tanks to store water. Furthermore, accuracy of determining overall water consumption is superior to existing methods.

Analytical scaling relations to evaluate leakage and intrusion in intermittent water supply systems.

Intermittent water supplies (IWS) deliver piped water to one billion people; this water is often microbially contaminated. Contaminants that accumulate while IWS are depressurized are flushed into customers’ homes when these systems become pressurized. In addition, during the steady-state phase of IWS, contaminants from higher-pressure sources (e.g., sewers) may continue to intrude where pipe pressure is low. To guide the operation and improvement of IWS, this paper proposes an analytic model relating supply pressure, supply duration, leakage, and the volume of intruded, potentially-contaminated, fluids present during flushing and steady-state. The proposed model suggests that increasing the supply duration may improve water quality during the flushing phase, but decrease the subsequent steady-state water quality. As such, regulators and academics should take more care in reporting if water quality samples are taken during flushing or steady-state operational conditions. Pipe leakage increases with increased supply pressure and/or duration. We propose using an equivalent orifice area (EOA) to quantify pipe quality. This provides a more stable metric for regulators and utilities tracking pipe repairs. Finally, we show that the volume of intruded fluid decreases in proportion to reductions in EOA. The proposed relationships are applied to self-reported performance indicators for IWS serving 108 million people described in the IBNET database and in the Benchmarking and Data Book of Water Utilities in India. This application shows that current high-pressure, continuous water supply targets will require extensive EOA reductions. For example, in order to achieve national targets, utilities in India will need to reduce their EOA by a median of at least 90%.

Transforming an Intermittent Into 24x7 Water Supply System in Sector No. 4 & 6 of Pcmc Pune

Transforming an Intermittent Into 24x7 Water Supply System in Sector No. 4 & 6 of Pcmc Pune

Water Quality Change from Source to the Point-of-Consumption in an Intermittent Water Supply System

Water Quality Change from Source to the Point-of-Consumption in an Intermittent Water Supply System

Utilizing analytic hierarchy process (AHP) for decision making in water loss management of intermittent water supply systems

Increasing water demands, in parallel with water scarcity, force water utilities in developing countries to follow complex operation techniques for the distribution of the available amounts of water. The reduction of water losses from water supply systems can help fill the gap between supply and demand. This strategy is characterized by the variety of options, and identification of the most appropriate option is a demanding process. An integrated multi-criteria decision making framework, precisely analytic hierarchy process (AHP) is applied to prioritize water loss reduction options for a typical intermittent water supply network in Palestine. The AHP was applied to structure the decision problem into a hierarchy framework, and four groups of decision makers were engaged to evaluate the elements. The results show that the strategic plan, which comprises controlling and managing operational pressure, was the best option. The selection of this option was highly connected to the conditions of the case study and to the well-known advantages of this strategy to reduce losses. It is anticipated that the developed methodology will help water utilities to identify integrated water loss management plans that will guide utility managers to conduct better control for water losses.

Multi-criteria optimization of supply schedules in intermittent water supply systems

One of the problems for water supply systems with intermittent supply is the peak flow produced at some hours of the day, which is usually much larger than that in a system with continuous supply. The main consequence is the reduction of pressure and flow at the ends or highest points of the system network. This, in turn, generates inequity in water supply and complaints from users. To reduce the peak flow, some sectors of the system must be assigned a different supply schedule. As a result, the supply curve is modified, and the peak flow is reduced. This reorganization seeks some optimal allocation schedule and must be based on various quantitative and qualitative technical criteria. This paper hybridizes integer linear programming and multi-criteria analysis to contribute with a solution proposal to the technical management of intermittent water supply systems, which provides short-term results and requires little investment for implementation. This solution does not seek perpetuating intermittent water supply. On the contrary, this methodology can be a useful tool in gradual transition processes from intermittent to continuous supply.

The supply and quality of urban water in arid island environments: a case study from the prefecture of Larnaka, Cyprus

In the present study, the residents of Larnaka Province in Cyprus assessed the quality and quantity of the water provided for urban use, the water supply network serving Larnaka city, and the adoption of water conservation methods. The survey was conducted using simple random sampling and included 426 individuals. The locals consider the water quality to be fair and the water consumption charges to be neither expensive nor inexpensive, while the majority disapprove of any increase to the water rates in relation to high consumption levels. People in Larnaka are fairly satisfied with the local water supply, and assess the water losses through the distribution network as being fair. Their three main sources of drinking water are tanks, bottled water and the mains water, with or without filtering. They do not consider operating an intermittent water supply system a useful measure and most of them have water storage tanks at home for mains water, but not for rainwater.