Monitoring and Control of Intermittent Water Distribution Network

Abstract

Millions of people in low and middle-income countries worldwide receive water only for a small fraction of the time in a day through piped networks. Even though the percentage of the world’s population with access to piped water has increased, the number of individuals receiving water intermittently is projected to rise. Water supply systems are designed for a continuous supply of water to consumers with a standard demand pattern. However, an unforeseen increase in demand, reduced network capacity, ease of operation and climate change results in Intermittent Water Supply. Because the intermittent water supply goes through filling and draining cycles regularly, the water is not always safe to drink. Due to ageing infrastructure, poor management, and system operation, the amount of Unaccounted For Water in these cities is extremely high and leads to inequitable water distribution. The water supply in developing countries is insufficient to meet demand, and there is a significant imbalance between supply and demand. This thesis examines the influence of intermittently supplied piped water on water inequity, the impact on the quality of water delivered, and possible solutions to intermittent supply. A framework for understanding the effect of inequitable distribution due to intermittent supply is developed first. Economic and geographical characteristics of the DMA, such as insufficient infrastructure, high Unaccounted For Water, socio-economic status, and so on, all contribute to inequity in the intermittent water supply. The inequality in intermittent water supply between 10 divisions and 83 DMAs in the South division of Bangalore, India, are examined in this study. The inequity is divided into four categories, namely: (i) inequity in water sharing, (ii) inequity in time of supply, (iii) inequity in the duration of supply and (iv) inequity in alternate supply. The supply, UFW, and consumption data were collected for a period of 36 months. The presence of inequity in water sharing was indicated by the Lorenz curve and Gini coefficient. The Kullback-Leibler divergence, Cauchy-Schwarz inequality, and Euclidean distance among supply zones revealed inequity in supply time and duration. Inequity in the supply duration and an alternate source of supply was also discussed using the Lorenz curve and Gini coefficient. The current analysis revealed a severe disparity in all four categories, showing that the IWS with poor infrastructure leads to inequitable water distribution. It was also clear that, despite significant savings in UFW, inequity remained largely unchanged. The most efficient way to counter the inequity in IWS is to move towards a continuous system. We study this phenomenon of Intermittent Water Supply with the city of Mysore, India, as an example, understand the issues therein and address them with a systematic procedure to achieve Continuous Water Supply. It is essential to solve the problem of Intermittent Water Supply due to the adverse effects caused. IWS can create inequity at various levels: command areas, DMAs, supply and sub-supply zones. On the contrary Continuous Water Supply has additional benefits like improved water quality, increased customer satisfaction, and better supply and demand man- agement. To achieve CWS, we formulate a convex cost minimisation problem with appropriate penalties to i) maintain the reservoirs at the desired level, ii) obtain a periodic solution and iii) avoid frequent changes in the valve configuration. The network-wide problem formulation helps vii compensate local infrastructure limitations using the excess infrastructure available elsewhere in the network. We then optimally control the water inflow into the reservoirs and meet daily demand. We propose a Simultaneous Perturbation Stochastic Approximation (SPSA) based gradient algorithm on solving the optimisation problem. A hydraulic modelling toolkit EPANET is used to compute the flows in the water network. We then initialise the reservoirs to their desired target levels using a similar approach, starting from arbitrary initial levels. The proposed algorithm was applied to two water networks in Mysore, India. The essential contribution here is to verify the possible enhancement of water supply systems by network-wide control. Risks to water quality are exacerbated due to intermittency of supply, mainly due to intrusion and back-flow, as well as variation in bio-film, deposits, and microbial growth. Chlorine is a widely used disinfectant in the drinking water treatment process, mostly in developing countries, due to its efficiency and affordability. Therefore, assessing the effect of intermittency in the drinking water supply on chlorine decay is needed to ensure safe drinking water delivery through piped networks in these countries. In this work, field sampling for chlorine decay measurement was carried out in adjoining continuous and intermittent water supply networks in Bangalore, India. The two networks received water from the same source. The first-order model was used to calculate chlorine decay rate in different pipe segments distributed across the networks. The effect of network parameters such as pipe velocity, pipe material, and pipe diameter on chlorine degradation rate was investigated. Further chlorine decay rates in continuous and intermittent networks were compared, considering the influence of these network properties. The analysis indicates that decay rates varied significantly with velocity in both networks, with reactive ma- terials being more sensitive to velocity variation than non-reactive materials. Reactive materials had higher decay rates than non-reactive materials, and decay rates increased with a decrease in pipe diameter, concurring with trends found in previous literature. The comparison of decay rates across networks showed that the average decay rate in the intermittent network was 1.5 times higher than the average decay rate in the continuous network, indicating that intermittency in the water supply has a long-term effect on chlorine decay. Contaminants can infiltrate a water distribution network at any time or location due to the ageing infrastructure, accidental discharge, or malicious actors. Contaminants such as total coliform bacteria, organic compounds, and others create serious health issues in a large population served by the WDS. This is especially prevalent in intermittent water supply, and it can lead to a loss of faith in the water utility. The detection of intentional or accidental contamination in a water distribution system (WDS) is necessary to ensure that society has access to adequate safe drinking water. One of the techniques for detecting contamination in WDS is to install the sensor. In the literature, determining the best location for the sensor is still a work in progress. We proposed ”EQ-water,” a new method for identifying sensor location which works for both continuous and intermittent water distribution systems. The EQ-water is based on complex network theory and utilizes very little hydraulic information. We evaluated the proposed method’s performance on four real networks, BWSN 1, BWSN 2, JPN, and D2B Bangalore networks. Furthermore, we compared the results to all of the BWSN’s proposed approaches and existing complex network-based methods. We employed TEVA-SPOT to assess the methods’ performance on four different objective functions, as well as the cumulative objective function. EQ-Water has the best performance in BWSN 1, JPN, D2B Bangalore and average performance in BWSN 2. Utility boards in India are ill-equipped to deal with Unaccounted For Water (UFW) in intermittent water supply, with leakage being the primary cause of UFW. Conducting controlled independent experiments in the field to detect leaks or study water quality is a time-consuming process. It is relatively difficult to interfere with a running water supply to conduct experiments and collect measurement data. As a result, at our R&D centre in IISc, Bangalore, we developed an experimental water supply setup. Detecting leaks in intermittent water supplies have not been studied in the literature; thus, in this study, we created such scenarios and used a data-driven approach to detect leaks in laboratory conditions. The goal of the work is to create an intermittent supply in the lab that mimics the real-world water supply of Bangalore, south, and to introduce various leak scenarios. Using the proposed data analytic approach using a log-likelihood model in conjunction with CUSUM, we then use this data to train the model. The testing data results show that leaks in intermittent supply systems can be detected and localised.