Real Water Supply System Research Articles

New methods based on a genetic algorithm back propagation (GABP) neural network and general regression neural network (GRNN) for predicting the occurrence of trihalomethanes in tap water

Monitoring trihalomethanes (THMs) levels in water supply systems is of great significance in ensuring drinking water safety. However, THMs detection is a time-consuming task. Developing predictive THMs models using parameters that are easier to obtain is an alternative. To date, there is still no application of optimization algorithms and general regression neural networks in predicting disinfection by-products levels. This study was to explore the feasibility of back propagation neural network (BPNN), genetic algorithm back propagation (GABP) neural network and general regression neural network (GRNN) for predicting THMs occurrence in real water supply systems. The results showed that the BPNN models' prediction ability was limited (test rp = 0.571–0.857, N25 = 61.5 %–91.5 %). Optimized by the genetic algorithm (GA), GABP models were generated and exhibited better prediction performance (test rp = 0.573 and 0.696–0.863, N25 = 68.2 %–93.6 %). However, GABP models took a lot of time and their prediction performance was unstable. A GRNN was then used to generate simpler neural network models, and the resulting prediction performance was excellent (total trihalomethanes and bromodichloromethane: test rp = 0.657–0.824, N25 = 81.8 %–100 %). In general, GRNN was the best at predicting THMs concentrations among the three models. However, it is worth noting that the prediction accuracy of bromodichloromethane (BDCM) was not high, which may be due to the absence of key parameters affecting BDCM formation. Accurate predictions of THMs by GRNN with these nine water parameters made THMs monitoring in real water supply systems possible and practical.

Switched-Delay Smith Predictor for the Control of Plants with Response-Delay Asymmetry

The modification of a Smith predictor for the control of plants with response-delay asymmetry has been proposed. It was developed for application in frequency converters for the control of the speed of the AC induction motor drives of pumps used in water- and liquefied-petroleum-gas-supply systems. Such plants are characterized by long response delays, and often these delays are asymmetric, i.e., the response delay to the rising and falling plant-control signal is different. A distinctive feature of the proposed modification is that the value of the response delay in the model of the plant used for the realization of the Smith predictor is switched. The operation of the proposed switched-delay Smith predictor, which was used with the proportional-integral controller, was analyzed using a simulation and experimentally in a real water-supply system. The obtained results prove an advantage of the suggested solution.

Using simple and easy water quality parameters to predict trihalomethane occurrence in tap water

Monitoring of disinfection by-products (DBPs) in water supply system is important to ensure safety of drinking water. Yet it is a laborious job. Developing predictive DBPs models using simple and easy parameters is a promising way. Yet current models could not be well applied into practice because of the improper dataset (e.g. not from real tap water) they used or involving the parameters that are difficult to measure or require expensive instruments. In this study, four simple and easy water quality parameters (temperature, pH, UVA254 and Cl2) were used to predict trihalomethane (THMs) occurrence in tap water. Linear/log linear regression models (LRM) and radial basis function artificial neural network (RBF ANN) were adopted to develop the THMs models. 64 observations from tap water samples were used to develop and test models. Results showed that only one or two parameters entered LRMs, and their prediction ability was very limited (testing datasets: N25 = 46–69%, rp = 0.334–0.459). Different from LRM, the prediction accuracy of RBF ANNs developed with pH, temperature, UVA254 and Cl2 can be improved continuously by tweaking the maximum number of neuron (MN) and Gaussian function spread (S) until it reached best. The optimum RBF ANNs of T-THMs, TCM and BDCM were obtained when setting MN = 20, S = 100, 100.1 and 60, respectively, where the N25 and rp values for testing datasets reached 85–92% and 0.813–0.886, respectively. Accurate predictions of THMs by RBF ANNs with these four simple and easy parameters paved an economic and convenient way for THMs monitoring in real water supply system.

New methods based on back propagation (BP) and radial basis function (RBF) artificial neural networks (ANNs) for predicting the occurrence of haloketones in tap water

Haloketones (HKs) is one class of disinfection by-products (DBPs) which is genetically toxic and mutagenic. Monitoring HKs in drinking water is important for drinking water safety, yet it is a time-consuming and laborious job. Developing predictive models of HKs to estimate their occurrence in drinking water is a good alternative, but to date no study was available for HKs modeling. This study was to explore the feasibility of linear, log linear regression models, back propagation (BP) as well as radial basis function (RBF) artificial neural networks (ANNs) for predicting HKs occurrence (including dichloropropanone, trichloropropanone and total HKs) in real water supply systems. Results showed that the overall prediction ability of RBF and BP ANNs was better than linear/log linear models. Though the BP ANN showed excellent prediction performance in internal validation (N25 = 98–100%, R2 = 0.99–1.00), it could not well predict HKs occurrence in external validation (N25 = 62–69%, R2 = 0.202–0.848). Prediction ability of RBF ANN in external validation (N25 = 85%, R2 = 0.692–0.909) was quite good, which was comparable to that in internal validation (N25 = 74–88%, R2 = 0.799–0.870). These results demonstrated RBF ANN could well recognized the complex nonlinear relationship between HKs occurrence and the related water quality, and paved a new way for HKs prediction and monitoring in practice.

Method for Determining the Probability of a Lack of Water Supply to Consumers

The water distribution subsystem is the most failing subsystem included in the water supply system. One of the main consequences of water supply failures is the lack of water supply to consumers, which is always very onerous. The paper presents a method of determining the conditional probability that a break in the supply of water to consumers of a certain duration will be caused by a specific type of failure. The result of the work was to identify water supply network failures that result in the longest water supply suspension time. The method was presented on a real water supply system. In order to reduce the incidence of long-term interruptions in water supply, water supply companies should mainly continue replacing gray cast iron pipes with thermoplastic materials. Actions taken to increase the safety of drinking water supply meet the current standards for the safety of drinking water, developed by the World Health Organization and the European Union.

Propagation of uncertainty in the water balance calculation in urban water supply systems – A new approach based on high-density regions

The water balance calculation is a well-known procedure that allows the water loss performance assessment in urban water supply systems. The International Water Association recommends it for a systematic assessment of non-revenue water volumes, where water losses are, in general, the most significant component. After water balance components calculation, a set of performance indicators can be obtained to support diagnosis and decision-making. Water balance components and performance indicators result from operations between multiple variables with uncertainties associated. Moreover, measurements of input and output volumes are not always available and estimations based on indirect data should be obtained and considered as “best estimates”. Therefore, the analysis of propagation is fundamental to ensure that the water utilities become more confident about the use of water balance outputs in decision-making. Additionally, since water balance is usually calculated using a single measurement or estimate for the annual input and output volumes, the estimation of the uncertainty through the standard deviation is not applicable. Hence, in this study, the uncertainties may be either given by a band, i.e., a minimum and a maximum value for the uncertainty, or may be calculated based on the minimum and maximum values for the variables. Thus, to study uncertainty propagation in the water balance calculation, three methods were explored: Delta method, Monte Carlo simulations and a new proposal based on high-density regions. This novel approach allows the association of an uncertainty measure for the uncertainty values. These methods were tested with water balance data published in previous studies and using data from two real water supply systems. The high-density regions with the uncertainty bands produced the best results as regards to the computation of the total uncertainty. This approach is suitable for general propagation of uncertainty in the annual calculation of the water balance and related performance indicators.

Optimizing Re-Chlorination Injection Points for Water Supply Networks Using Harmony Search Algorithm

In order to achieve the required residual chlorine concentration at the end of a water network, the installation of a re-chlorination facility for a high-quality water supply system is necessary. In this study, the optimal re-chlorination facility locations and doses were determined for real water supply systems, which require maintenance in ord3r to ensure proper residual chlorine concentrations at the pipeline under the present and future conditions. The harmony search algorithm (HSA), which is a meta-heuristic optimization technique, was used for the optimization model. This method was applied to two water supply systems in South Korea and was verified through case studies using different numbers of re-chlorination points. The results show that the proposed model can be used as an efficient water quality analysis and decision making tool, which showed the optimal re-chlorination dose and little deviation in the spatial distribution. In addition, the HSA results are superior to those of the genetic algorithm (GA) in terms of the total injection mass with the same number of evaluations.

Intelligent system for control of water distribution networks

Abstract The objective of this research study was the development of an intelligent system based on artificial neural networks for water distribution networks that operate with parallel pumps. The purpose of the system is to automate the process and to define the operating state of the electric motors (on, off or with partial rotation speed). The intelligent system developed is generic, which allows the application of its control structure in similar processes, and it was applied in an experimental setup that simulates a real water supply system. The performance of the network was tested experimentally under different operating conditions, including in the presence of disturbances. The settling time was, in all experiments, less than 30 seconds, the tests did not show overshoot and the maximum error was 2.9%. Results showed excellent performance in terms of pressure regulation, and it is hoped that the controller can be successfully implemented in real water distribution systems, in order to reduce water and electricity consumption, decrease maintenance costs and increase the reliability of operating procedures.

상수도관내 중금속 용출에 대한 수소이온농도의 영향 평가 연구

우리나라 상수도 기반시설 설비에 관련된 기존의 인증평가는 경제적 측면과 내구성 등 물리적 측면에 초점을 맞추어 사용되어 왔다. 그러나 경제수준이 상승하면서 상수도에 대한 위생, 보건, 안전성, 삶의 질에 대한 국민의식이 향상됨에 따라 상수도 서비스의 위생보건학적 품질향상이 요구되고 있다. 지난 5년간 국내 497개 정수장의 수질분석 자료를 고찰한 결과 pH는 5.8~8.5의 범위로 나타났다. 하지만, 현재 우리나라 수도용 자재 및 제품의 위생안전기준 공정시험방법(위생안전시험법)은 pH 7.0에서만 평가하고 있어, 실제 상수도 pH 조건에서 관내 중금속용출에 대한 기초정보가 부족하다. 이러한 배경으로 본 연구에서는 국내에서 대표적으로 사용되는 관에 대하여 pH변화가 중금속용출에 미치는 영향을 실험적으로 분석연구하였다. 본 연구 결과, pH가 낮아질수록 일부 금속의 용출정도가 증가하는 것을 확인하였다. 특히 pH 5.8일 경우, 구리재질의 관에서 Cu가 보정계수(Normalization Factor) 적용 후에도 위생안전기준을 상회하였다. 스테인레스 재질의 관에서는 Cr, Cu가, 구리재질의 이음관에서는 Cd, Pb, Cu, Zn이, 아연재질의 이음관에서는 Zn이 기준치를 각각 상회하였으나 보정계수를 적용하면 기준치를 만족하였다. 본 연구의 결과로 현행 위생안전시험법에서 pH조건을 7.0 이외의 낮은 pH 조건을 포함하는 개정의 필요성이 제안되었다. 추후 상수도관으로 사용되는 다른 종류의 관에 대한 추가 연구의 필요성도 제시되었다. 본 연구는 차후 우리나라 위생안전기준의 개정연구에 필요한 기초자료 제시에 기여를 하였다. In Korea, previous certification of water supply infrastructure was mainly focused on economical and physical aspects. Recently, hygienic safety of water supply service has become a sensitive and important issue to our people for evaluating the water quality with growth of economy and education system. According on water quality in 497 Korean water supply facilities, pH values in the supplied water have ranged between 5.8-8.5. However, little is known about metal leachability at the pH conditions observed in the real water supply systems because a fixed pH condition (pH 7.0) has been used in the current standard method, 'Hygienic Safety Testing Method', in water supply. In this work, we examined the effects on heavy metal leachability with pH differences in the water supply pipes which are typically used in Korea. As a result, the amounts of metal leachability were tended to increase when pH levels were decreased. Especially at pH 5.8, Cu leachability from Cu pipes was found to exceed the public health standard level even after applying a normalization factor (NF) given by the current Korea standard method. The Cr and Cu leached from stainless steel pipes, Cd, Pb, Cu, and Zn from Cu-based pipe fittings, and Zn from Zn-based pipe fittings were exceeded the Korean hygienic safety standards while, after applying the NF, concentrations of the leached metals were satisfied with the current Korean standard. The findings from this work provide implications on the needs of reforming the current hygienic safety standard methodology.

Dynamic response behind an accident occurred in a main WSS

This paper states an accident occurred in a real main water supply system where the pipe system suffered movements provoking major displacements and leading to the rupture of concrete support blocks. A slow closure of an isolation valve installed in a large suction pipe was the main action. During the inspection procedure after the accident it was found that one valve was slightly corroded (a very small leakage was noticed) and the non-return valve was not isolating well enough. Two numerical models are presented to get approximated solutions for 3D fluid-structure interaction problems by implementing the Galerkin method. The boundary conditions are properly defined for the pipe branch end by applying a spring-damper to suppress part of the pipe system. The one-way model was compared with the two-way model, being equally emphasised which type of integrated analysis (one-way or two-way) is more appropriate, depending on the system characteristics.

Metabolism-based modelling for performance assessment of a water supply system: a case study of Reggio Emilia, Italy

A new class of conceptual simulation tools, as a complement to physically based models, is becoming available to simulate the whole water cycle in urban areas for strategic planning, often involving the allocation of a great amount of financial resources. These simulation tools are required to estimate the impact of the today's decisions on the system performance over the next decades and to compare and rank different intervention strategies. To achieve this, this paper aims to build the metabolism-based modelling of a real water supply system using the recently developed WaterMet2 model in order to evaluate long-term performance metrics for possible intervention strategies. This metabolism-based approach was demonstrated for evaluation of the water supply system of Reggio Emilia, Italy, which is one of the demonstration case studies in the EU TRUST (TRansitions to the Urban water Services of Tomorrow) project. Based on the strains imposed by pressing challenges (here population growth) two intervention strategies were analysed. The results obtained show that the built and calibrated WaterMet2 model allows a broader understanding of the impacts of alternative intervention strategies taking into account multidimensional aspects of the sustainability beside conventional service performance.

A convex mathematical program for pump scheduling in a class of branched water networks

We address the day-ahead pump scheduling problem for a class of branched water networks with one pumping station raising water to tanks at different places and levels. This common class is representative of rural drinking water distribution networks, though not exclusively so. Many sophisticated heuristic algorithms have been designed to tackle the challenging general problem. By focusing on a class of networks, we show that a pure model-based approach relying on a tractable mathematical program is pertinent for real-size applications. The practical advantages of this approach are that it produces optimal or near-optimal solutions with performance guarantees in near real-time, and that it is replicable without algorithmic development. We apply the approach to a real drinking water supply system and compare it to the current operational strategy based on historical data. An extensive empirical analysis assesses the financial and practical benefits: (1) it achieves significant savings in terms of operation costs and energy consumption, (2) its robustness to dynamic pricing means that demand-response can be efficiently implemented in this type of energy-intensive utility.

Energy Auditing as a Tool for Outlining Major Inefficiencies: Results from a Real Water Supply System

The application of a novel energy auditing scheme in a real water supply system and its sub-systems to determine major sources of energy inefficiency is presented. This scheme has been consolidated in the Portuguese National Initiative for the management of water-energy losses (www.iperdas.org). Within this initiative, 17 water utilities have carried out energy audits following a two-step procedure: (i) simplified energy auditing and calculation of efficiency metrics for the global system and for sub-systems and (ii) detailed energy auditing for critical sub-systems. The case-study of Águas do Sado water utility is presented to illustrate the application of this approach. This system has 25% of non-revenue waterand consumes 5.5 GWh per year, which is approximately twice the minimum energy required. The analysis of therespective 17 sub-systems has shown that the major inefficiencies are due to topography constraints, to water losses and to the lack of intermediate service pressure levels.

Real Time Water Supply System Hydraulic and Quality Modeling – A Case Study

This paper presents a real time water supply system hydraulic and quality modeling framework that is applied in a case study. The simulated quality parameters include age, traced water source, temperature, pH, hardness and free chlorine.A full-scale and well-calibrated hydraulic model of the whole water supply system is built using an extended version of EPANET, allowing storing and restoring the state of plug flow in links. Once an hour, the simulator is updated with the previous hour's hydraulic and quality state from the utility's supervisory control and data acquisition (SCADA) system and a simulation is performed. The results are stored both in GeoJSON format for geographic information systems (GIS) and in a relational database for later use. Some results are presented to the general public in a geographically aggregated form over a web user interface and as open data using Representational State Transfer (REST) web service interface.

Pressure Changes Evaluation for Valve Replacement Condition Based on a Micro-Scope Hydraulic Model

Abstract The pressure change of whole water supply system is studied in this paper. Some areas are isolated by closing isolation valves. The schemes of valve shutdown are made based on the valve arrangement principles and the methods of the valve closing. The whole water supply system is divided into 8457 segments, of which two segments are closed to prevent the water entering the area. Therefore, the valve can be replaced in that two areas. The micro-scope hydraulic model is closest to the real water supply system is used to simulate the pressure changes. The color coding is used to show the pressure of the whole water supply system. The simulation in different water consumption conditions is also conducted.

Performance indices for water network partitioning and sectorization

Water network partitioning in district metering areas, or sectorization, is an important process for improving water network management. It can help water utilities to implement active leakage control, conduct pressure management, and prevent network contamination. It is generally achieved by closing some network pipes, thus reducing pipe redundancy and affecting system performance. No systematic set of performance indices has been defined to evaluate a sectorization design and thus allow for a comparison of different possible sectorizations on a formal basis. In this paper, several performance indices for water network partitioning are proposed and tested using two real water supply systems: Parete in Italy and Matamoros in Mexico. Both systems' sectorizations were previously designed by a novel effective automatic technique recently developed by the authors. For both the original and sectorized networks, the proposed performance indices considered energy dissipated in the network, network resilience, pressure variation, fire-fighting capacity, water age, and mechanical redundancy. Network resilience appears to be the most representative index for the entire network, whereas pressure variation indices are more appropriate for describing individual districts. Except for fire-fighting capacity in one network, system performance did not appear to be affected significantly after sectorization.

Efficiency estimation of water supply systems control depending on the volume and content of the controlled object operational information

The efficiency of realized control depends on the degree of the adequacy of using simulation models of the object. In the article the criteria that characterize the degree of the received solutions proximity are suggested using various forms of the water supply systems model. The algorithm of efficiency estimation of water supply systems control depending on the volume and content of the controlled object operational information is suggested. It is shown that to provide the optimum values of these criteria it is sufficient to have the pressure measures at all the local dictating points of the network. It is demonstrated that further increase of the numbers of measurements do not result in improvement of the criteria meaning. The research is carried out using the method of imitation modeling of the real water supply systems functioning.

Water network sectorization based on a genetic algorithm and minimum dissipated power paths

Water Network Sectorization (WNS) consists of dividing a water system into sectors with an independent water supply. When each district is supplied by its only water source the districts can be defined as i-DMAs (isolated District Meter Areas) because they are completely cut off from the rest of the water network. This isolation of the i-DMAs may decrease hydraulic performance of the water system reducing its topologic (network loops) and hydraulic (diameter sections) redundancy. Traditionally the design of WNS is carried out by empirical or simulation assisted trial-and-error approaches that are difficult to apply to large water distribution systems. In this paper an original methodology for automatic sectorization of water networks is proposed. The methodology is based on Shortest Path techniques that allow defining a tree graph of the network with dissipated power used as weight of the pipes (or links). Once the districts are found, a swapping phase follows which is achieved by using a genetic algorithm (GA) that allows refining the choice of nodes that belong to each district. The objective function of the GA is based on network mean pressure. The methodology was tested, using different performance indices, on two real water supply systems.

상수관망의 에너지 평가기법에 관한 연구

The systematic analysis and evaluation of required energy in the processes of drinking water production and supply have attracted considerable interest considering the need to overcome electricity shortage and control greenhouse gas emissions. On the basis of a review of existing research results, a practical method is developed in this study for evaluating energy in water supply networks. The proposed method can be applied to real water supply systems. A model based on the proposed method is developed by combining the hydraulic analysis results that are obtained using the EPANET2 software with a mathematical energy model on the MATLAB platform. It is suggested that performance indicators can evaluate the inherent efficiency of water supply facilities as well as their operational efficiency depending on the pipeline layout, pipe condition, and leakage level. The developed model is validated by applying it to virtual and real water supply systems. It is expected that the management of electric power demand on the peak time of water supply and the planning of an energy-efficient water supply system can be effectively achieved by the optimal management of energy by the proposed method in this study.

Utilização de um algoritmo genético híbrido para operação ótima de sistemas de abastecimento de água

A operação dos Sistemas de Abastecimento de Água é realizada por profissionais que usam a sua experiência como um meio de avaliação no controle de equipamentos hidromecânicos com o objetivo de garantir o fornecimento de água à população. Geralmente, as regras operacionais utilizadas visam à garantia da continuidade do abastecimento público, sem a preocupação com a economia de energia elétrica dos motores em funcionamento. Neste trabalho, apresenta-se um algoritmo genético híbrido que permite determinar as estratégias de operações com custos energéticos reduzidos. A análise do modelo é feita em um estudo de caso real localizado na cidade de Ourém (Portugal). O novo modelo reduz consideravelmente o tempo computacional em comparação aos modelos utilizados na literatura especializada.