Risk Assessment of Factors Influencing Non-Revenue Water Using Bayesian Networks and Fuzzy Logic

This paper aims to initially, identify effective factors of Non Revenue Water (NRW) and its three major components: apparent losses, real losses and non-revenue authorized consumptions in water distribution networks. In the next step, they should be ranked according to their potential in the reduction of the amount of NRW. Besides, incidence of each NRW components imposes some special economic and social impacts. In the present study, by considering data scarcity and uncertainty of the available data and information, risk assessment of NRW and its components has been done through two stages. The first stage is initiated by designing a questionnaire so as to collect data and information about 41 identified parameters in part of Tehran Water and Wastewater Company as the research pilot. Then, in order to demonstrate the probability relationships between factors influencing NRW components, Bayesian Network (BN) is used. At the end of this stage, the parameters are prioritized in terms of their impact. Through the following stage, consequences of NRW components existence are identified and fuzzified, to consider their uncertainty. After that, based on the risk definition and Fuzzy Inference Systems )FIS( concept, fuzzified probability and consequences are combined and NRW components’ risk is calculated. In this study, the calculated risk of NRW components in the study area are “Moderately High” and equal to 7.05, 6.95 and 6.4 for apparent loss, real loss and non-revenue authorized consumptions, respectively which means that decision makers and managers of this district should take serious actions to reduce the amount of risk.     

An Integrated Model to Evaluate Losses in Water Distribution Systems

To evaluate non revenue water (NRW) and losses in water distribution networks a methodology is developed by applying “annual water balance” and “minimum night flow” analyses. In this approach the main NRW components such as leakage from reported and un-reported bursts and background leakage, with real or estimated data, enabling assessment of indices of leakage performance are evaluated. Also, a novel procedure is introduced in this paper that can determine the nodal and pipe leakage by using a hydraulic simulation model. Recognising the pressure dependency of leakage the total consumption is divided into two parts, one pressure dependent and the other independent of local pressure, and the hydraulic behaviour of the network is analyzed. A computer code is developed to evaluate all components of water losses based on the proposed methodology. For better representation of the results and management of the system, the outputs are exported to a GIS model. Using the capabilities of this GIS model, the network map and attribute data are linked and factors affecting network leakage are identified. In addition, the effects of pressure reduction are investigated. The model is illustrated by a real case study. The results show that the suggested model has overcome the shortcomings of the existing methodologies by accounting for the leakage and other NRW components in water distribution networks more realistically.     

Apparent Losses Analysis in District Metered Areas of Water Distribution Systems

As one of the most important component of Non-Revenue Water (NRW), apparent loss exists in all kinds of water distribution system but hardly can be assessed due to its complexity and invisibility. Aimed to analyze the different component of apparent loss on the basis of the characteristic of flow meters in district metered areas (DMA), an effective methodology to calculate the three primary parts of NRW is presented in this paper. In particular, the real loss assessment can be carried out by Minimum Night Flow (MNF) analysis; while the unauthorized consumption can be identified by consuming variation curve; finally, the metering error is calculated by the genetic algorithm with the integrated model based on IWA water balance audit. Application of this method in water distribution network of a steel-making enterprise improves its significance in controlling NRW of DMA.     

Leakage Detection Using Smart Water System: Combination of Water Balance and Automated Minimum Night Flow

This paper presents a methodology for the application of the Smart Water technology to detect water leakage. This methodology consists in the use of the traditional water balance method together with the minimum night flow approach. This procedure has been applied to a large-scale pilot project conducted at the Scientific Campus of the University of Lille, which is the size of a small town. The water network of the campus is monitored by a set of sensors that record and transmit, in real-time, the hydraulic parameters of the water system. Analysis of real-time data has allowed the verification of water balance and the estimation of water losses level in the network. The paper presents an improvement of the application of the minimum night flow method, which is based on the determination of flow thresholds. A leak alarm is generated if the night flow exceeds the thresholds. This data analysis methodology provides the capability to detect the pipe bursts quickly, thereby reducing the runtime of leakage. The application of the improved method allowed the detection of 25 unreported leaks and decreased the Non-Revenue Water (NRW) level by 36%.     

Methods of Assessment of Water Losses in Water Supply Systems: a Review

This paper reviews Water Loss Assessment methods in water supply systems. There’re three main methods: Minimum Night Flow (MNF) analysis, Bursts And Background Estimates (BABE), and Top-Down Water Balance. MNF analysis provides actual measurements whose accuracy can be evaluated. It requires intensive field work, though. The limitation of MNF application is the sensitivity of two parameters; average pressure which is rarely accurate, and estimation of the night consumption. Assessing real losses with the factors generated by the BABE model should not be conducted unless there is no other option due to its excessive assumptions. Instead, the method should be a supplementary tool to break down the volume of real losses into its sub-components. The Top-Down Water Balance is neither pressure-dependent nor extensive-field-work method. However, its assumptions of apparent losses aren’t appropriate for all utilities. The lack of an objective methodology for estimating unauthorized consumption is a major limitation, and research on its estimation is demanding.     

An integrated modelling concept for immission-based management of sewer system, wastewater treatment plant and river.

Today's planning standards deal with the individual urban drainage components (sewer system, wastewater treatment plant and receiving water) separately, i.e. they are often designed and operated as single components. As opposed to this, an integral handling considers the drainage components jointly. This novel approach allows a holistic and more sustainable planning of urban drainage systems. This paper presents an integrated modelling concept. The aim is to analyse fluxes through the total wastewater system and to integrate pollution-based control in the upstream direction, that is, e.g., managing the combined water retention tanks as a function of state variables in the WWTP or the receiving water. All models of the different subsystems are based on the Activated Sludge Model (ASM) concept of IWA, including River Water Quality Model No. 1 (RWOM). Simulations can be done in truly parallel mode using the simulation environment SIMBA. The integrated modelling concept is applied to the river Dhuenn and the urban wastewater system of the municipality of Odenthal (Germany). An optimised operation of the system using RTC proves to be a very effective measure.     

WEAP21—A Demand-, Priority-, and Preference-Driven Water Planning Model

Abstract

The Water Evaluation and Planning Version 21 (WEAP21) Integrated Water Resource Management (IWRM) model seamlessly integrates water supplies generated through watershed-scale hydrologic processes with a water management model driven by water demands and environmental requirements and is governed by the natural watershed and physical network of reservoirs, canals, and diversions. This version (WEAP21) extends the previous WEAP model by introducing the concept of demand priorities and supply preferences, which are used in a linear programming heuristic to solve the water allocation problem as an alternative to multi-criteria weighting or rule-based logic approaches. WEAP21 introduces a transparent set of model objects and procedures that can be used to analyze a full range of issues faced by water planners through a scenario-based approach. These issues include climate variability and change, watershed condition, anticipated demands, ecosystem needs, the regulatory environment, operational objectives, and available infrastructure.     

New mathematical procedure for the automatic estimation of influent characteristics in WWTPs.

This paper proposes a new methodology for the automatic characterization of the influent wastewater in WWTP. With this methodology, model components are automatically estimated by means of optimization algorithms combining a-priori knowledge of the expected wastewater composition with experimental information from the available measurement data. The characterization is carried out based on an extended model components list in which components are described by means their elemental mass fractions. This allows an easy establishment of relationships between model components with experimental data and also, to obtain a general methodology applicable to any model used for wastewater biological treatments. The characterization of the wastewater influent of Galindo-Bilbao according this methodology has demonstrated its validity and the easy application to the ASM1 model influent characterization.     

An integrated approach for improving the wastewater discharge and treatment systems

Since treatment plants have been built all over Germany during the last decades, the water quality of receiving streams has been improved remarkably. But there are still a lot of quality problems left, which are caused e.g. by combined sewer overflows (CSO), treatment plant effluents or rainwater discharges from separate sewer systems. At present different efforts are undertaken to control sewer systems in order to improve the operation of urban drainage systems or more generally, design processes. The Emschergenossenschaft and Lippeverband (EG/LV) are carrying out research studies, which are focusing on a minimization of total emissions from sewer systems both from wastewater treatment plant (WWTP) effluents and from CSO. They consider dynamic interactions between rainfall, resultant wastewater, combined sewers, WWTP and receiving streams. Therefore, in an advanced wastewater treatment, a model-based improvement of WWTP operation becomes more and more essential, and consequently a highly qualified operational staff is needed. Some aspects of the current research studies are presented in this report. The need and the use of an integrated approach to combine existing model components in order to optimize dynamic management of combined sewer systems (CSS) with a benefit for nature are outlined.     

A knowledge management methodology for the integrated assessment of WWTP configurations during conceptual design

The current complexity involved in wastewater management projects is arising as the XXI century sets new challenges leading towards a more integrated plant design. In this context, the growing number of innovative technologies, stricter legislation and the development of new methodological approaches make it difficult to design appropriate flow schemes for new wastewater projects. Thus, new tools are needed for the wastewater treatment plant (WWTP) conceptual design using integrated assessment methods in order to include different types of objectives at the same time i.e. environmental, economical, technical, and legal. Previous experiences used the decision support system (DSS) methodology to handle the specific issues related to wastewater management, for example, the design of treatment facilities for small communities. However, tools developed for addressing the whole treatment process independently of the plant size, capable of integrating knowledge from many different areas, including both conventional and innovative technologies are not available. Therefore, the aim of this paper is to present and describe an innovative knowledge-based methodology that handles the conceptual design of WWTP process flow-diagrams (PFDs), satisfying a vast number of different criteria. This global approach is based on a hierarchy of decisions that uses the information contained in knowledge bases (KBs) with the aim of automating the generation of suitable WWTP configurations for a specific scenario. Expert interviews, legislation, specialized literature and engineering experience have been integrated within the different KBs, which indeed constitute one of the main highlights of this work. Therefore, the methodology is presented as a valuable tool which provides customized PFD for each specific case, taking into account process unit interactions and the user specified requirements and objectives.     

Effluent treatment by multi-media filtration, microfiltration and ultrafiltration: results of a pilot investigation at WWTP Hoek van Holland.

Upgrading of wastewater treatment plant (WWTP) effluent as a part of the Dutch governmental policy to close the water cycle has increasing interest now. The Water Board Hoogheemraadschap van Delfland together with the project team of Witteveen + Bos Consulting Engineers, Delft University of Technology and Rossmark water treatment investigated the reuse possibilities of WWTP effluent in the region of Delfland. Therefore pilot research was carried out at WWTP Hoek van Holland applying different filtration techniques: multi-media filtration, micro- and ultrafiltration. The results show stable process performances of the different filtration techniques when proper pre-treatment was applied. For microfiltration the filtration characteristics were strongly influenced by particles which were not retained in the multi-media filter. For ultrafiltration the filtration characteristics were strongly influenced by organic components < 0.2 microm. The upgraded WWTP effluent could not be used directly as process water or for agriculture purposes, due to high concentrations of COD and salts in the WWTP effluent and filtrates. However WWTP effluent or floc filtrate could be applied directly as water for the washing of sea-sand.     

Environmental Assessment of a Wastewater System under Water demand management policies

Water demand management policies (WDMPs) are considered necessary for sustainable water supplies to affect urban water infrastructures from various aspects, which has less attention in previous studies. Hence, this study is focused on proposing a comprehensive novel approach to provide helpful insight for researchers and policy-makers towards the environmental effects of applying WDMPs on wastewater systems. The life cycle assessment (LCA) method assesses the environmental burdens of utilizing WDMPs in the operation stage of a real wastewater system in Baharestan city, Iran. A detailed inventory is considered, including maintenance of sewer pipelines, replacement of manhole covers, civil works, road rehabilitation, energy consumption, chemical usage, transportation, and air emissions of the WWCN and WWTP using SimaPro software. Results show that a significant part of the environmental impacts accounts for energy consumption, which has strong effects on most midpoint categories and has a great change in different scenarios. For example, energy’s impact on the global warming category is reduced from around 18.4 to 8.5 million kg CO₂ eq. from scenario 0 to scenario 4 with an average of 165.4 to 94 L/capita/day of wastewater production, respectively. Besides, the results demonstrate that the environmental effects driven by the WWTP are eightfold the corresponding WWCN’s impacts. Overall, the outcomes from the present study reveals that implementing WDMPs can lead to diminishing environmental impacts. For instance, reducing wastewater production up to 68% can decrease 18% of the WDMPs’ environmental impacts of the wastewater system in the operation stage.

     

Vulnerability Analysis of Future Public Water Supply Under Changing Climate Conditions: A Study of the Moy Catchment,Western Ireland

An application of the Water Evaluation and Planning tool Version 21 (WEAP21) is developed to analyse the vulnerability of the future public water supply in the River Moy catchment, western Ireland. The River Moy’s future hydrology is modelled using the WEAP21 integrated rainfall runoff module and an ensemble of statistically downscaled future climate series. This approach facilitates the identification of the most vulnerable future public water supplies without being constrained by the availability of historically observed streamflow records. The model is calibrated by linking the model-independent parameter estimation tool (PEST) with the hydrological model and verified by reproducing observed streamflow records. This research suggests an emerging vulnerability to water stress of the public water supply sector under the four modelled scenarios, for areas which currently have plenty of water available. These results present a basis for future planning and management of the Moy catchment and its water resources.     

Integrated operation of sewer system and WWTP by simulation-based control of the WWTP inflow.

In recent years numerical modelling became a standard procedure to optimise urban wastewater systems design and operation by integration. For dynamic control of the wastewater teatment plant (WWTP) inflow, a model-based predictive concept is introduced aiming at improving the receiving water quality. An on-line simulator running parallel to the real WWTP operation reflects the actual state of operation and provides this model information to a prognosis tool which determines the best option for the WWTP inflow. The investigations showed that it is possible to reduce the NH4-N peak concentrations in the receiving water by dynamic WWTP inflow control based on predictive scenario analysis.     

Membrane bio-reactor for textile wastewater treatment plant upgrading.

Textile industries carry out several fiber treatments using variable quantities of water, from five to forty times the fiber weight, and consequently generate large volumes of wastewater to be disposed of. Membrane Bio-reactors (MBRs) combine membrane technology with biological reactors for the treatment of wastewater: micro or ultrafiltration membranes are used for solid-liquid separation replacing the secondary settling of the traditional activated sludge system. This paper deals with the possibility of realizing a new section of one existing WWTP (activated sludge + clariflocculation + ozonation) for the treatment of treating textile wastewater to be recycled, equipped with an MBR (76 l/s as design capacity) and running in parallel with the existing one. During a 4-month experimental period, a pilot-scale MBR proved to be very effective for wastewater reclamation. On average, removal efficiency of the pilot plant (93% for COD, and over 99% for total suspended solids) was higher than the WWTP ones. Color was removed as in the WWTP. Anionic surfactants removal of pilot plant was lower than that of the WWTP (90.5 and 93.2% respectively), while the BiAS removal was higher in the pilot plant (98.2 vs. 97.1). At the end cost analysis of the proposed upgrade is reported.     

A Water Management Support System for Amman Zarqa Basin in Jordan

A Water Management Support System for Amman Zarqa Basin in Jordan has been developed. The water management support system employs the Water Evaluation and Planning system (WEAP). The water resources and demands in the basin were modeled as a network of supply and demand nodes connected by links. The model was calibrated for the year 2005 data and then validated for the year 2006 data. Validation results showed good agreement between calculated and measured inflows to wastewater treatment plants in the basin. The model was run for the year 2005 data as well as for four scenarios for the year 2025 which are Business As Usual (BAU) scenario, Advanced Wastewater Treatment (AWWT) scenario, the Red Sea, Dead Sea Channel (RSDSC) scenario and the optimistic scenario. The BAU scenario assumes that water use trends for the year 2025 follows predictable trends, the implementation of the disi project and the Wehda dam are main components of the BAU scenario. The AWWT scenario assumes that the effluent of As Samra wastewater treatment plant is treated to a level where it can be used for unrestricted irrigation within the basin and in the highlands. The main component of the RSDSC scenario is the implementation of the RSDSC project. The optimistic scenario combines both the AWWT scenario and the RSDSC scenario. The AWWT scenario, the RSDSC scenario, and the optimistic scenario are child scenarios of the BAU scenario. The results showed that neither domestic demand nor agricultural demand is met for the year 2005. The results also showed that domestic and industrial demands can be satisfied for all the considered scenarios by proper management of the available resources. However, agricultural demand can’t be satisfied for the business as usual scenario.     

城市供水产销差率与漏损控制研究进展

针对产销差率居高不下这一供水行业问题,研究了供水产销差率的定义和组成、水平衡分析、国内外供水产销差率及漏损现状,以及当前控制产销差率、漏损率的技术和方法,如DMA(district metering area)分区、管网压力控制、检漏工具和管网建模等。降低产销差率是一项综合性的任务,需各种措施共同施用,才能有效提升供水企业的效益。     

Integrated modelling of sewer system and wastewater treatment plant for investigating the impacts of chemical dosing in sewers

Chemicals are often dosed to control the production and accumulation of hydrogen sulfide in sewers. The biological and/or chemical actions of these chemicals have profound impacts on the composition of wastewater entering a WWTP, thereby affecting its performance. In this paper, an integrated modelling methodology for simultaneously investigating the effects of dosing of chemicals in sewer network and N and P removal at the downstream WWTP is reported. The sewer system is modelled using a sewer model (SeweX), and the WWTP is modelled using ASM2d model with some modifications. The importance of integrated modelling in sewer management is also demonstrated.     

Direct precipitation on demand at large Scandinavian WWTPs reduces the effluent phosphorus load

On demand use of direct precipitation of wastewater has been successfully implemented at several large Scandinavian wastewater treatment plants (WWTPs) as a cost-efficient method of treating wastewater bypassing secondary treatment. During wet weather situations or when the capacity of secondary treatment is reduced excess wastewater can be treated through efficient direct precipitation. This increases the total capacity of the WWTP to remove phosphorus during these periods. This treatment strategy allows the WWTPs to meet stringent effluent phosphorus limits without extending secondary treatment of the main plant, despite high wet weather flows. The gain in terms of reduced phosphorus emissions varies depending on local conditions such as climate, collection system and secondary treatment capacity. It also varies from year to year depending on the weather and reductions of capacity due to planned refurbishing or unplanned breakdown of equipment. Operating chemical precipitation on demand has proved to contain challenges to operation and organisation of the WWTP. These challenges include logistics of start-up, training of staff and maintaining the system between occasions of operation. Sufficient up-stream storage capacity, reliable weather forecasts and good contracts with suppliers of chemicals are keys of success.