Identification of Suitable Locations in a Small Water Supply Network for the Placement of Water Quality Sensors Based on Different Criteria under Demand-Driven Conditions

Drinking water quality monitoring in real time is of utmost importance to ensure public health. Although water utilities, following the related legislative framework, monitor drinking water quality through samplings, the likelihood of detecting contaminants in consumers’ taps is low, depending on the scale of the monitoring programme. Additionally, even if the monitoring frequency is high, there is a time delay since sampling and analysis processes take some time. The selection of suitable locations for the installation of online water quality sensors is a hard task for a water utility due to the complexity of the water distribution system, the limitations of certain network junctions which are not easily accessible, and the computational burden involved. This topic has been extensively studied in recent years and sophisticated methods have been developed using optimization techniques. However, small water utilities do not have the means to implement such tools. This paper applies a methodology to identify the suitable junctions for the installation of online water quality sensors based on different objectives and under demand-driven conditions. This paper utilizes the hydraulic simulation model of a standard network to set up the water quality simulation model. A thorough analysis of various contamination scenarios takes place with different injection nodes and at different starting injection times for 24 h. The latter relates to the contaminant’s spread due to varying water demand. After a thorough analysis of 816 scenarios, a prioritized list of the most suitable nodes for the installation of the sensors is available for each optimization objective. Comparing the prioritized list of nodes achieved from each single or multi-objective function, the detection probability is almost the same. The analysis revealed that, due to varying water demand conditions, the ranking of the proposed nodes suitable for the installation of water quality monitoring sensors differs. Thus, varying hourly water demand should be part of analyses seeking to get reliable results. © 2022 by the authors

Evaluating the performance level of a water distribution network under unbalanced operating conditions - The case of Kos Town (GR)

The need for a common international terminology is growing the last few years regarding the performance evaluation of urban water distribution systems, due to the wide diversity of definitions used across the word (even within the same country). Thus, the IWA Task Forces on Water Losses developed an international standard approach to calculate the water balance of an water distribution system utilizing best practices around the world. In Greece the need for a common approach is even more urgent as the country faces severe water shortage problems and there is no place for water losses due to ignorance. Greek Water Utilities are far behind in applying appropriate indicators to safely calculate the water losses level and therefore design effective strategies to reduce it. The paper presents the results of the Kos Town (Kos island) project regarding the performance evaluation of its water network. The project's goals were to develop the system's water balance (based on the IWA guidelines), calculate several performance indicators and compare them to national and international relative data available. The final outputs were to: a) estimate the apparent and real losses levels; b) calculate the non-revenue water level and its cost; and c) provide solid proposals targeted to an effective water losses reduction policy. The difficulties faced during the whole attempt are also presented. © 2010 Taylor & Francis Group, London

Socially fair domestic water pricing: who is going to pay for the non-revenue water?

To plan and develop a socially fair water pricing policy is a difficult task to do since many factors need to be taken into consideration. Usually, a significant part of a water tariff structure is the fixed charge that should be associated to the opportunity cost the consumers have to pay. In many cases though, it is set just to balance the water utility’s revenues and expenses. This weird billing practice results in the underestimation of the Non-Revenue Water (NRW) and in the minimization of water use efficiency. The application of the IWA Standard International Water Balance 2nd modification and its element, the Minimum Charge Difference (MCD) can reveal how big this “underestimation” is. MCD represents the water volume that although not consumed, generates revenues to the water utility. Another element towards a socially fair pricing policy is the allocation of the NRW-related cost. In every water network, two main water users are identified: the actual water consumers and the network itself due to the real water losses occurring. The paper presents a novel methodology to estimate the MCD and a new approach regarding a socially fair allocation of the NRW-related cost. © 2015 Balaban Desalination Publications. All rights reserved

Urban water services public infrastructure projects: Turning the high level of the NRW into an attractive financing opportunity using the PBSC tool

Today, the public sector worldwide is facing many difficulties in financing several public infrastructure projects. Therefore, the public-private partnerships (PPPs) became a very popular project-providing-tool. One of the sectors where this tool is being rapidly expanding today is the environmental sector. This sector is very important for the public health and the protection of the environment (especially projects concerning water supply, sanitation and solid waste management). Such projects are being implemented through PPPs all over the world. These projects have to do with the reduction of the non revenue water (NRW) and the provision of better services regarding water supply and sanitation. The present paper is a discussion paper about successful and not successful examples of PPPs implementation in the environmental sector. After introducing the basic principals of PPP projects, several problems concerning their implementation are discussed in this paper. Although the PPPs are implemented in big projects today, the challenge is their implementation in small-medium projects. Finally, a number of key factors are being identified and analysed regarding the performance based service contracts (PBSC), being the latest introduced tool regarding the implementation of PPP projects concerning the urban water services sector

Predicting the behavior of a pipe network using the "critical Z-score" as its performance indicator

The paper deals with pipe reliability assessment in two networks using the Discriminant Analysis and classification (DAC) method. The pipes of each network are divided in two groups based on whether they failed at least once (failures group) or not (successes group). Several scenarios resulting from combining pipe characteristics (such as length, diameter, wall thickness, operating pressure, grade, and product (fluid in the pipe), lifetime) are being analyzed. A sensitivity analysis of the data available takes place to check the stability of the results. The criterion of the "critical Z-score" is finally used as an indicator predicting the pipe's future state (fail or not). The goals for each network are to develop a model that can correctly classify network pipes to successes or failures; define the pipe characteristics to be "blamed" for the pipes' behavior; and predict whether a pipe will fail or not. Studying the results of the DAC method application at the case study networks, a SWOT analysis is attempted in order to find out whether and under which presuppositions DAC can be successfully applied to water pipe networks. (C) 2009 Elsevier B.V. All rights reserved

On-going evaluation of the WFD 2000/60/EC implementation process in the European Union, seven years after its launch: are we behind schedule?

Although the European Union (EU) has made some considerable progress regarding protection of water resources (tackling significant problems at national and at EU level), increased efforts are still needed to get and keep its waters clean. After 30 years of developing EU water legislation, all the involved stakeholders express this demand. In 2000, the Water Framework Directive (WFD) 2000/60/EC, establishing a framework for Community actions regarding protection of water resources, was adopted. Its implementation is now well underway, as most of the EU-Member States have fulfilled their current obligations of submitting their reports. An on-going evaluation of the WFD implementation process is attempted here, based on all available data seven years after its launch. Special focus is given to Greece regarding problems that have occurred

Potable water security assessment – a review on monitoring, modelling and optimization techniques, applied to water distribution networks

The paper tries to investigate some of the most important issues that need to be addressed to provide an integrated system for potable water security, in developed countries. It can be understood that in developing countries both supplied water quantity and quality are important for water security. According to the US Environmental Protection Agency, “water security is defined as prevention and protection against contamination and terrorism.” Water quality safeguarding has been addressed by many researchers during the last decades trying to define ways to ensure water of proper quality for the public. As unexpected contamination events may occur in water distribution systems, early warning systems providing the water managers with enough time to act effectively need to be developed. These systems should include interconnected: (a) monitoring tools to monitor in real time at least the most crucial water quality characteristics; (b) modelling tools to simulate the transport of any harmful contaminant and calculate the variations of its concentration; and (c) optimization tools to define the optimal locations and density of the monitoring sensors and disinfection stations. The drinking water supply system addressed in this paper consists of the supply system after the water treatment plant and until the consumers’ taps, with special emphasis on the water distribution system. Drinking water security is addressed in cases other than normal operating conditions. Specifically, the paper examines contamination phenomena due to operational failures (e.g., during the disinfection process), natural disasters, pollution accidents and malicious actions. Contamination phenomena due to other factors, such as lead contamination are not included in this paper. It reviews the literature on monitoring, modelling and optimization techniques used in water distribution systems while at the same time proposes an integrated approach consisting of risk assessment methods and the use of “simheuristics” to deal with drinking water security. © 2017 Desalination Publications. All rights reserved

Developing THMs' predictive models in two water supply systems in Greece

Disinfection is a very significant water treatment process for drinking water safety, as it inactivates pathogens from drinking water. However, disinfection-by-products (DBPs) are formed which are accused of contributing to cancer and reproductive/developmental effects. Research has provided many predictive models for the formation of DBPs based on various water quality parameters and following different methodologies. The present study aims at developing predictive models for the formation of DBPs in two drinking water supply systems in Greece. Data from the water supply systems are used. A statistical analysis took place to identify the predictive models for the formation of Total trihalomethanes (TTHMs). The results showed that some of the developed models are more reliable than others. However, further study is necessary in order to obtain more data on variables that are affecting trihalomethanes (THMs) formation. Such models can be used mainly locally. © 2020 by the authors

Sustainable management of the water cycle in terms of quality, quantity and economy

[No abstract available

Assessing the impact of dmas and the use of boosters on chlorination in a water distribution network in Greece

Disinfection is one of the most important water treatment processes as it inactivates pathogens providing safe drinking water to the consumers. A fresh-water distribution network is a complex system where constant monitoring of several parameters and related managerial decisions take place in order for the network to operate in the most efficient way. However, there are cases where some of the decisions made to improve the network’s performance level, such as reduction of water losses, may have negative impacts on other significant operational processes such as the disinfection. In particular, the division of a water distribution network into district metered areas (DMAs) and the application of various pressure management measures may impact the effectiveness of the water chlorination process. Two operational measures are assessed in this paper: (a) the use of inline chlorination boosters to achieve more efficient chlorination; and (b) how the DMAs formation impacts the chlorination process. To achieve this, the water distribution network of a Greek town is chosen as a case study where several scenarios are being thoroughly analyzed. The assessment process utilizes the network’s hydraulic simulation model, which is set up in Watergems V8i software, forming the baseline to develop the network’s water quality model. The results proved that inline chlorination boosters ensure a more efficient disinfection, especially at the most remote parts/nodes of the network, compared to conventional chlorination processes (e.g., at the water tanks), achieving 100% safe water volume and consuming almost 50% less chlorine mass. DMAs’ formation results in increased water age values up to 8.27%, especially at the remote parts/nodes of the network and require more time to achieve the necessary minimum effective chlorine concentration of 0.2 mg/L. However, DMAs formation and pressure management measures do not threaten the chlorination’s efficiency. It is important to include water age and residual chlorine as criteria when optimizing water pressure and the division of DMAs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/)