Lost in optimisation of water distribution systems? A literature review of system operation

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified

Wastewater irrigation and health: assessing and mitigating risk in low-income countries

Wastewater irrigation / Public health / Health hazards / Risk assessment / Epidemiology / Sewage sludge / Excreta / Diseases / Vegetables / Leaf vegetables / Economic impact / Wastewater treatment / Irrigation methods / Developing countries

Developing Multi-Scale Models for Water Quality Management in Drinking Water Distribution Systems

Drinking water supply systems belong to the group of critical infrastructure systems that support the socioeconomic development of our modern societies. In addition, drinking water infrastructure plays a key role in the protection of public health by providing a common access to clean and safe water for all our municipal, industrial, and firefighting purposes. Yet, in the United States, much of our national water infrastructure is now approaching the end of its useful life while investments in its replacement and rehabilitation have been consistently inadequate. Furthermore, the aging water infrastructure has often been operated empirically, and the embracement of modern technologies in infrastructure monitoring and management has been limited. Deterioration of the water infrastructure and poor water quality management practices both have serious impacts on public health due to the increased likelihood of contamination events and waterborne disease outbreaks. Water quality reaching the consumers’ taps is largely dependent on a group of physical, chemical, and biological interactions that take place as the water transports through the pipes of the distribution system and inside premise plumbing. These interactions include the decay of disinfectant residuals, the formation of disinfection by-products (DBPs), the corrosion of pipe materials, and the growth and accumulation of microbial species. In addition, the highly dynamic nature of the system’s hydraulics adds another layer of complexity as they control the fate and transport of the various constituents. On the other hand, the huge scale of water distribution systems contributes dramatically to this deterioration mainly due to the long transport times between treatment and consumption points. Hence, utilities face a considerable challenge to efficiently manage the water quality in their aging distribution systems, and to stay in compliance with all regulatory standards. By integrating on-line monitoring with real-time simulation and control, smart water networks offer a promising paradigm shift to the way utilities manage water quality in their systems. Yet, multiple scientific gaps and engineering challenges still stand in the way towards the successful implementation of such advanced systems. In general, a fundamental understanding of the different physical, chemical, and biological processes that control the water quality is a crucial first step towards developing useful modeling tools. Furthermore, water quality models need to be accurate; to properly simulate the concentrations of the different constituents at the points of consumption, and fast; to allow their implementation in real-time optimization algorithms that sample different operational scenarios in real-time. On-line water quality monitoring tools need be both reliable and inexpensive to enable the ubiquitous surveillance of the system at all times. The main objective of this dissertation is to create advanced computational tools for water quality management in water distribution systems through the development and application of a multi-scale modeling framework. Since the above-mentioned interactions take place at different length and time scales, this work aims at developing computational models that are capable of providing the best description of each of the processes of interest by properly simulating each of its underlying phenomena at its appropriate scale of resolution. Molecular scale modeling using tools of ab-initio quantum chemical calculations and molecular dynamics simulations is employed to provide detailed descriptions of the chemical reactions happening at the atomistic level with the aim of investigating reaction mechanisms and developing novel materials for environmental sensing. Continuum scale reactive-transport models are developed for simulating the spatial and temporal distributions of the different compounds at the pipe level considering the effects of the dynamic hydraulics in the system driven by the spatiotemporal variability in water demands. System scale models are designed to optimize the operation of the different elements of the system by performing large-scale simulations coupled with optimization algorithms to identify the optimal operational strategies as a basis for accurate decision-making and superior water quality management. In conclusion, the computational models developed in this study can either be implemented as stand-alone tools for simulating the fundamental processes dictating the water quality at different scales of resolution, or be integrated into a unified framework in which information from the small scale models are propagated into the larger scale models to render a high fidelity representation of these processes

Biofilm growth and chlorine stability in the recycled water distribution system

Wastewater recycling is widely practiced to solve water crises created by increasing demand due to rapid population growth and scarcity of resources arising from climate change. Certain treatment is always provided to meet the appropriate health guidelines of the recycled water. When water is distributed over the pipelines and tanks, microbes can regrow and deteriorate water quality, and hence a disinfectant, usually chlorine, is added to the water. Chlorine can still decay while in transport and the problem can exist. Optimal chlorine levels are therefore to be maintained after the treatment to ensure the water quality does not deteriorate. For such fundamental understanding of factors impacting chlorine residuals are needed in the recycled water. While there are a lot of studies on drinking water systems, there is a scarcity of information on recycled water chlorine stability. This work is aimed to fill the knowledge gap by investigating the Sydney Olympic Park Authority (SOPA) recycled water pipelines and pilot-scale biofilm reactor system set up at the water treatment plant to elucidate the fundamentals. An investigation was carried out to examine the water quality parameters that may degrade chlorine residuals in the recycled water distribution system of SOPA. Physicochemical parameters such as free chlorine, total chlorine, DOC, ammonia, nitrite, nitrate and pH were measured in the bulk water samples. Biofilm growth potential of two different pipe materials under the similar environment, especially chlorine residuals of the storage reservoir before supplying to the distribution system was investigated to determine the role of biofilm components in decaying chlorine. Three flow cell columns of bioreactors containing biofilm coupons of polyvinyl chloride (PVC) and high-density polyethylene (HDPE) pipes were continuously operated for 105 days. Results were obtained from the examination of chlorine stability in the bulk water samples shows organic chloramine has reduced the effectiveness of chlorination. Chlorine decay in the water system occurred mainly due to inorganic and organic compounds such as metals deposition and bacterial activities, which were supported by the results of biofilm development data from the pilot-scale bioreactor system. Biofilm thickness, volume, mass and visualized images contribute an important role on understanding the decay of chlorine residuals. Over 15 weeks of biofilm development, the fluctuating chlorine trend of the recycled water in Sydney Olympic Park system has an adverse impact on biofilm constituents, bacteria cells and extracellular polymeric substance (EPS) production. As compared to traditional measurements, confocal laser scanning microscope (CLSM) provided different recording of multiple biofilm parameters with their subsequent visualization and quantification. In addition, discoloured water factors such as metals such as Fe, Mn deposition within biofilms were observed and the results illustrate that the discoloured water event could be related to presence of Fe and Mn in the recycled chlorinated systems. In all the samples, organic chloramine was found to be the dominant chlorine species in the recycled water distribution system. According to monitoring data, biofilms did not grow as fast as expected due to the presence of chlorine, organic chloramine, other unknown inhibitors and/or high flow rate. Free chlorine and slow-growing biofilms may oxidise Fe or Mn and influence the retention of these elements within the biofilm. Both PVC and HDPE had the same trend of increasing biofilm thickness as well as the biomass. HDPE pipe surfaces were more susceptible towards biofouling than PVC. EPS volume was usually higher than the bacterial cell volume in both pipe materials whereas EPS volume was higher in HDPE than PVC. The highest volume of EPS was approximately 4000 μm3/m2 compared to the highest volume of the bacterial cell about 2400 μm3/m2. The biofilm is not enough in the pipe materials to show the impact on decaying chlorine at concentrations range between 1 - 3 mg/L. Organic chloramine possibly plays a critical, but an unknown, role in determining the growth of biofilm and dirty water complaints through release of metals

IMPACTS OF EXTREME WEATHER ON THE VARIABILITY OF CRITICAL PARAMETERS IN DRINKING WATER SUPPLY SYSTEMS: INSIGHTS FROM OPERATIONAL EXPERIENCE

Eventi meteorologici estremi come ondate di calore, forti piogge, siccità prolungate e inondazioni hanno un impatto significativo sulle fonti idriche, sui processi di trattamento e sulle reti di distribuzione, determinando cambiamenti nei parametri di qualità dell'acqua e aumentando le sfide operative. Questa tesi indaga l'impatto degli eventi meteorologici estremi indotti dal clima sulla qualità dell'acqua potabile, concentrandosi sui cambiamenti nei parametri chiave e sulle strategie di gestione del rischio nei sistemi di approvvigionamento idrico. È stato utilizzato un approccio multi-metodo, tra cui un'approfondita revisione della letteratura, sondaggi sui gestori dei servizi idrici in Italia e Vietnam e uno studio di caso approfondito a Brescia, Italia. Lo studio evidenzia la crescente frequenza e gravità delle sfide legate al clima nei sistemi di acqua potabile. Le principali preoccupazioni includono contaminazione batterica, alti livelli di torbidità nell'acqua di sorgente e temperature dell'acqua aumentate che accelerano le reazioni chimiche e l'attività batterica nelle reti di distribuzione. Lo studio considera anche l'integrazione di sistemi di monitoraggio in tempo reale, che hanno trasformato la gestione della qualità dell'acqua consentendo una valutazione e una risposta immediate al rischio. In questo contesto, il monitoraggio operativo, come delineato nel D.Lgs. 18/2023, garantisce la conformità continua con gli standard di sicurezza concentrandosi sulla funzionalità delle misure di controllo del rischio, a differenza del monitoraggio analitico tradizionale, che fornisce valutazioni della qualità dell'acqua a lungo termine. Un progresso fondamentale in quest'area è stato lo sviluppo di sistemi di allerta precoce (EWS). Monitorando costantemente pH, conduttività e torbidità, gli EWS possono rilevare rapidamente cambiamenti imprevisti nei sistemi idrici. Ad esempio, improvvisi aumenti di torbidità possono indicare contaminazione o problemi strutturali, richiedendo un intervento immediato. Questi sistemi non solo migliorano le capacità di risposta, ma semplificano anche i programmi di monitoraggio a lungo termine dando priorità agli indicatori critici. Inoltre, gli EWS possono essere integrati con controlli automatizzati, come valvole o sistemi di lavaggio, per mitigare i rischi in tempo reale. Tuttavia, l'efficacia di tali sistemi dipende da una solida gestione e interpretazione dei dati, che richiede metodi statistici per elaborare i dati grezzi in informazioni fruibili. La creazione di database e grafici di controllo completi è essenziale per un processo decisionale informato e una maggiore affidabilità del sistema di fornitura. Attraverso sondaggi sui fornitori di servizi idrici in Italia e Vietnam, lo studio ha identificato variazioni regionali nella percezione del rischio climatico e nella capacità di adattamento. Sebbene entrambi i paesi affrontino sfide simili indotte dal clima, la loro capacità di mitigare i rischi differisce a causa delle differenze nei quadri normativi, nelle risorse finanziarie e nei progressi tecnologici. I fornitori idrici italiani sottolineano la conformità normativa con le direttive dell'Unione Europea sulla qualità dell'acqua e sui contaminanti emergenti, mentre i regolatori vietnamiti sottolineano i vincoli infrastrutturali e l'urgente necessità di investire in tecnologie di trattamento delle acque resilienti. Uno studio di caso a Brescia, in Italia, fornisce un esame dettagliato degli impatti diretti del cambiamento climatico sui sistemi di acqua potabile. L'analisi dei dati mostra che gli eventi di forti piogge sono correlati a picchi di torbidità e indicatori batterici, che richiedono maggiori sforzi di disinfezione e controlli microbiologici più rigorosi alla fonte. Per affrontare queste sfide, questa tesi propClimate change is increasingly recognized as a major threat to the safety and sustainability of drinking water systems worldwide. Extreme weather events such as heat waves, heavy rainfall, prolonged droughts and floods significantly impact water sources, treatment processes and distribution networks, leading to changes in water quality parameters and increasing operational challenges. This thesis investigates the impact of climate-induced extreme weather events on drinking water quality, focusing on changes in key parameters and risk management strategies in water supply systems. A multi-method approach was used, including an in-depth literature review, surveys of water service managers in Italy and Vietnam and an in-depth case study in Brescia, Italy. The study highlights the increasing frequency and severity of climate-related challenges in drinking water systems. Key concerns include bacterial contamination, high levels of turbidity in source water, and increased water temperatures that accelerate chemical reactions and bacterial activity in distribution networks. The study also considers the integration of real-time monitoring systems, which have transformed water quality management by enabling immediate risk assessment and response. In this context, operational monitoring, as outlined in D.Lgs. 18/2023, ensures ongoing compliance with safety standards by focusing on the functionality of risk control measures, unlike traditional analytical monitoring, which provides long-term water quality assessments. A key advance in this area has been the development of Early Warning Systems (EWS). By continuously monitoring pH, conductivity, and turbidity, EWS can quickly detect unexpected changes in water systems. For example, sudden increases in turbidity can indicate contamination or structural problems, prompting immediate intervention. These systems not only enhance response capabilities but also simplify long-term monitoring programs by prioritizing critical indicators. Furthermore, EWSs can be integrated with automated controls, such as valves or flushing systems, to mitigate risks in real time. However, the effectiveness of such systems depends on robust data management and interpretation, requiring statistical methods to process raw data into actionable insights. The creation of comprehensive databases and control charts is essential for informed decision making and increased reliability of the supply system. Through surveys of water service providers in Italy and Vietnam, the study identified regional variations in climate risk perception and adaptive capacity. While both countries face similar climate-induced challenges, their ability to mitigate risks differs due to differences in regulatory frameworks, financial resources, and technological advances. Italian water providers emphasize regulatory compliance with European Union directives on water quality and emerging contaminants, while Vietnamese regulators emphasize infrastructure constraints and the urgent need to invest in resilient water treatment technologies. A case study in Brescia, Italy, provides a detailed examination of the direct impacts of climate change on drinking water systems. Data analysis shows that heavy rainfall events are correlated with spikes in turbidity and bacterial indicators, requiring increased disinfection efforts and tighter microbiological controls at the source. To address these challenges, this thesis proposes several adaptation strategies to enhance the resilience of drinking water systems. First, real-time water quality monitoring should be integrated with advanced sensor technologies and data analytics to enable early detection of contamination and fluctuations in key parameters. Second, microbial monitoring technologies should be improved by implementing new detection tools that significantly reduce incubation times, enable faster bacterial identification, and improve response times compared to conventional methods

A multi-objective optimization model for operation of intermittent water distribution networks

Abstract: Intermittent operation of water distribution networks (WDNs) is an undesirable yet inevitable strategy under some circumstances such as droughts, development, electricity blackouts, and water pollution, mostly in developing countries. Intermittent utilization of WDNs poses several disadvantages encompassing water quality degradation, deterioration of the water-distribution system, and extra operational and maintenance costs due to frequently interrupted supply, unfair water distribution among consumers, and reduction of system serviceability. This paper proposes a multi-objective optimization model to address the negative consequences of intermittent water shortages. The model is intended to maximize the quantitative and qualitative reliability and the fairness in water supply, and to minimize the frequency of supply interruption. The developed model also considers pragmatic limitations, water quality, water pressure, and supply reservoir's constraints to plan the operation of intermittent water distribution systems under water shortage. The model's efficiency is tested with a WDN in Iran and compared with a standard operation policy (SOP) for water distribution. According to the evaluated efficiency criteria concerning reliability, resiliency, and vulnerability of water quality and quantity of water supply, the developed model is superior to the SOP rule and improves the performance of the network under intermittent operation. In addition, the results demonstrate there is a tradeoff between the uniformity of water distribution and the frequency of supply interruption that shows operators’ and customers’ conflicting priorities