Optimization of Water Distribution Networks Using Integer Linear Programming

In this study optimum design of municipal water distribution networks for a single loading condition is determined by the branch and bound integer linear programming technique. The hydraulic and optimization analyses are linked through an iterative procedure. This procedure enables us to design a water distribution system that satisfies all required constraints with a minimum total cost. The constraints include pipe sizes, which are limited to the commercially available sizes, reservoir levels, pipe flow velocities, and nodal pressures. Accuracy of the developed model has been assessed using a network with limited solution alternatives, the optimal solution of which can be determined without employing optimization techniques. The proposed model has also been applied to a network solved by others. Comparison of the results indicates that the accuracy and convergence of the proposed method is quite satisfactory.     

正确解决“管网叠压”供水技术推广难题的途径

“管网叠压”供水技术目前正在大面积推广,但绝大多数管网叠压供水设备并没有发挥出应有的作用。原因是供水设备的运行方式不节能、不科学。实践证明：“管网叠压恒压水泵＋屋顶水箱”全自动供水设备是管网叠压供水技术推广的正确途径。     

Water Delivery System Planning Considering Irrigation Simultaneity

Time should be considered in carrying out the design and management of demand irrigation distribution systems. In this paper, a method to characterize the pumping flow in demand pressurized systems throughout the day and irrigation season is presented. This method considers the temporal evolution of water requirements during the irrigation season and water demand concentration in certain periods of the irrigation day due to different electrical energy charges. The model was established based on data from an actual water distribution network of an irrigation district in southern Spain. The results differed significantly from those obtained using approaches based on establishing a uniform working probability for the outlets of the water distribution network at all hours of the irrigation day, which underestimated the circulating flows or system capacity. The most probable pumping flow with uniform probability was 3.1 m3/s, a smaller value than those obtained in the off-peak and average energy tariff times (4 and 3.4 m3/s, respectively). The total energy head required at the booster pumping in each period of the irrigation season was simulated. 10,000 randomly chosen scenarios were simulated for each irrigation day and each energy tariff time. The heterogeneous vertical stratification between 50 and 103 m of the required piezometric head was obtained as a function of the demanded flow for the water distribution system. This paper includes a pump selection algorithm for recommending least cost or optimum pump combinations in the distribution network and to evaluate the system’s energy cost. The pump recommendations show that the optimal solution could have saved 41% of the pumping cost of the Fuente Palmera irrigation district.     

Water Distribution Network Renewal Planning

This paper provides an overview of the writers' previous work in formulating a comprehensive approach to the important problem of water distribution network renewal planning, with a particular emphasis on the computing aspects involved. As pipes in a water distribution network age in service, they are characterized by increased frequency of breakage and decreased hydraulic capacity. The resulting service failures incur utility costs for the repair or rehabilitation of the pipe systems and consumer costs for degraded system performance. The challenge to the decision maker is to determine the most cost-effective plan in terms of what pipes in the network to rehabilitate, by which rehabilitation alternative and at what time in the planning horizon, subject to the constraints of service requirements (system reliability, service pressure, etc.) A dynamic programming approach, combined with partial and implicit enumeration schemes, was used to search the vast combinatorial solution space that this problem presents. A computer program was written to implement these concepts. A hydraulic network solver is used by the program to assure the network conformance to hydraulic constraints during the search for a solution. The outcome is a strategy that identifies, for each pipe in the network, the optimal rehabilitation∕renewal alternative and its optimal time of implementation. The significance of this method is in its ability to identify an optimal rehabilitation strategy while considering the deterioration of both structural integrity and hydraulic capacity of the entire network. The best current heuristic method is limited in practical studies to a network of up to 15–20 pipe links. A more efficient heuristic method is required for implementing these principles in a larger-scale water distribution system and is the subject of current research.     

南北方工业给排水设计差异

从给水和排水管网、消防给水系统和工业循环冷却水系统4个方面介绍了南方地区及北方地区工业给排水设计的不同及其注意事项。     

Simulation of Hydropneumatic Tanks in Computer Pipe Network Models

Pipe network computer models of water systems that include hydropneumatic tanks can be used to evaluate performance of existing water systems or in the design of new distribution facilities. Pipe network models allow the modeling of storage tanks in which the free water surface is variable with the inflow and outflow. Most existing pipe network models do not allow direct input of hydropneumatic tanks. Some writers describe modeling of hydropneumatic tanks as a fixed diameter tank of an equivalent area based on the maximum and minimum operating pressures of the tank. In real hydropneumatic tanks, the pressure change due to input or output of water is greater as more water is stored in the tank. A relationship to define the geometry of a free water surface tank that would exactly simulate a hydropneumatic tank was derived which can be input into a pipe network model using the variable area tank feature.     

Considering Actual Pipe Connections in Water Distribution Network Analysis

The classical assumption of representing total demand along a pipe as two lumped withdrawals at its terminal nodes is hitherto common. It is a simplification of the network topology which is useful in order to drastically reduce the number of nodes during network simulation. Conversely, this simplification does not preserve energy balance equation of pipes and, for this reason, it is an approximation that could generate significant head loss errors. This paper presents a modification of the global gradient algorithm (GGA) which entails an enhancing of GGA (EGGA) permitting the effective introduction of the lumped nodal demands, without forfeiting correctness of energy balance, by means of a pipe hydraulic resistance correction. The robustness and convergence properties of the algorithm are compared with those of the classical GGA. Furthermore, the effectiveness of EGGA is demonstrated by computing the network pressure status under different configurations of the connections along the pipes of a test network.     

球墨铸铁管在工程中的应用与分析

近几年来，球墨铸铁管在企业工程建设供水管网中已被广泛应用。分析了该管材在济钢工程中的应用情况，认为它具有强度高、韧性好、抗腐蚀能力强、寿命长、安装方便等优点，是一种比较理想的管材。     

对小城镇给水工程规划的几点认识

通过东莞市洪梅镇给水工程规划的实例，提出对小城镇给水工程规划中用水量预测、给水系统布局、管网规划等问题的几点认识。     

广钢居住区饮用水二次污染的防治

通过对广钢居住区饮用水二次污染的原因进行分析,在管网、水池、供水系统等方面提出了改进方法,并介绍后续深度处理工艺,此工艺是未来供水模式的发展方向.     

Comparison of SS 304 LN and 316 LN as choice of structural material for primary pipe in fast breeder reactors

In pool type FBRs primary sodium pumps (PSP), operating in parallel, circulate the sodium through the core to remove the nuclear heat. The pumps suck the sodium from cold pool and supply it to a spherical header at the bottom; subsequently the sodium flows through pipes from the spherical header into the grid plate, before entering the core subassemblies. Under normal operating condition, each pipe is subjected to 0.8 MPa internal pressure of sodium flowing at 670 K. As the pipe is located in the cold pool, it is at an isothermal temperature of 670 K during normal operation. The pipe is subjected to hot shock during two thermal transients Viz. offsite power failure (160 times) and loss of Steam water system (47 times). Both these events lead to Safety Grade Decay Heat Removal (SGDHR) operation and the cold pool reaches 791 K during offsite power failure and 816 K during loss of steam water system. Even though the normal operating temperature for the primary pipes conveying sodium from spherical header to grid plate is below creep regime, creep damage occurs due to the governing hot shocks discussed above. One of the criteria for selecting the material is the creep fatigue damage for the longer design life (40 years for the Prototype Fast Breeder Reactor under construction and 60 years for the future reactors). The material choice for out of core reactor assembly components are generally austenitic stainless steels (SS316LN or SS304LN) except for the top shield. In this paper, the choice between SS 304 LN Vs SS 316 LN for primary sodium pipe with respect to the governing failure mode of creep-fatigue interaction is addressed.     

管线探测仪对测量供水管道漏损的作用

供水管道在供水过程中出现渗漏和破损,如何及时发现漏损的水量以减少供水的损失,减少漏失率,全功能管线探测仪在供水管道测漏上起了至关重要的作用。     

Water Distribution Network Design Using Heuristics-Based Algorithm

Water distribution network that includes supply reservoirs, overhead tanks, consumer demand nodes, interconnecting pipes, lifting pumps, and control valves is the main mode of water supply for majority of the communities especially in urban areas. Supply of required quantity of water and at right time is the primary objective of water distribution network analysis. The analysis of water distribution networks can be broadly classified into design and operation problems and both problems have been the focus of many researchers over the past three decades. In the water distribution network design problems, the target is attaining the cost effective configuration that satisfies the minimum hydraulic head requirement at the demand nodes. In this paper, a new algorithm for design of water distribution network namely “heuristics-based algorithm” which completely utilizes the implicit information associated with the water distribution network to be designed has been proposed and validated with two water distribution networks. It is found that the proposed algorithm performs well for the least-cost design of water distribution networks.     

万立制氧机组增加氮气产量实践

在分子筛流程中,为了将制氧机组中空气预冷系统水冷塔的氮气替换出来并送入管网,采取了增设水冷机组冷却经污氮冷却的低温水的措施。采取措施后,出塔水温在不使用氮气的条件下达到了设计要求,满足了生产工艺条件,从而增加了氮气产量。     

Algorithm for Automatic Detection of Topological Changes in Water Distribution Networks

Topological and pressure-driven analyses are an integral part of reliability/risk considerations for a water distribution system. For example, it is often necessary to identify which parts of the distribution network are isolated from water sources after the valves have been closed in response to a mechanical pipe failure. Pressure-driven analysis is then necessary to ascertain the consequences of pipe failures in terms of the performance of the functioning subsystem while pipe breaks are being fixed in the isolated area. Therefore, it is extremely useful to have an algorithm for the automatic identification of nodes/pipes disconnected from the water source(s). However, this is a complex problem because valves sometimes significantly modify the network topology. Furthermore, the use of isolation valves can cause a demand shortage to some customers (due to pressure reduction) during the abnormal operating conditions in the system. Thus, pressure-driven simulation of the network behavior is required. For these reasons, a novel algorithm capable of automatic detection of topological network changes is coupled with a robust pressure-driven simulation model. This algorithm is tested on two case studies involving a small artificial water distribution system and a larger, real-life network. The results obtained clearly demonstrate the robustness of the algorithm developed.     

Disinfection By-Product Formation during Long-Term Water Storage in Alaska

In many areas of Northern and Western Alaska, small streams and shallow lakes serve as community raw water supplies. These water supplies freeze completely during winter. In order to supply drinking water during the 6–9 month winter, communities store water that was treated during summer. A chlorine residual is maintained in the stored water. Raw water sources derived from surface water may be heavily laden with dissolved organic matter. At utilities where organic matter escapes treatment, the potential for accumulation of disinfection by-products (DBPs) during storage is a significant health concern. The following study was performed to evaluate this potential threat. Water was collected from five operating utilities, four that normally store water for 6–9 months and one that produces drinking water year-round. Raw, filtered (i.e., unchlorinated) and “finished” (i.e., filtered and chlorinated) water samples were collected during the summer pumping season and stored in the laboratory for 8 months. In order to mimic practice in the field, the chlorine residual was maintained in the finished water for the full storage period. While the concentration of DBPs in the finished water varied over the study period, there was not a statistically significant trend from the third to the eighth month of storage. The observed DBP values were strongly a function of the type of treatment system used. Those systems passing more organic matter had higher DBP values throughout the storage period. The ultraviolet absorbance at 254 nanometers ?start(UV254)end? decreased continuously in the finished water coincident with chlorine consumption. ?startUV254end?, often used as a surrogate for DBPs, remained constant during the entire storage periodin raw and filtered water samples. Filtered water that was stored prior to chlorination accumulated fewer DBPs than finished water that was continuously chlorinated during the storage period. This result suggests that storing filtered water instead of finished water for long periods would limit DBP exposure to consumers. This conclusion was based on a comparison of DBP formation potentials (i.e., raw and filtered water) to DBPs (i.e., finished water). It is important to note that DBP formation potentials are based on a ?start24?hend?chlorine contact time. If long term storage were provided for filtered water, a smaller volume of secondary storage would still be needed to provide contact time for disinfection.     

国内老钢铁企业的节水途径探索

国内老钢铁企业大部分都经历由小到大的发展过程,由于在起步阶段及后续的发展阶段,缺乏统一的总体规划,造成布局不合理,尤其是给排水设施及管网的布置,往往随着主体工艺的改造而因陋就简的同步扩展,造成整个系统存在诸多问题,如耗水量大、安全性差等,给水资源造成极大的浪费且造成环境污染。分析了国内几个老钢铁企业的水系统,从中找出一些共性问题,并提出了一些改造思路。     

给水管网爆管原因分析及防治对策

从邯钢历年爆管事故统计分析入手，详细论述了爆管原因，从而在管材的选用、排气系统的完善、水锤作用的消除、接口工艺的改进、温度应力的防止、施工质量的提高、给水管道的更新等方面提出了防止爆管的对策。     

给水管网爆管原因分析及防治对策

从邯钢历年爆管事故统计分析入手,阐述了爆管原因,从管材的选用、排气系统的完善、水锤作用的消除、接口工艺的改进、温度应力的防止、施工质量的提高、给水管道的更新等方面提出了防止爆管的对策。     

Real-Time Demand Estimation and Confidence Limit Analysis for Water Distribution Systems

A real-time estimation of water distribution system state variables such as nodal pressures and chlorine concentrations can lead to savings in time and money and provide better customer service. While a good knowledge of nodal demands is prerequisite for pressure and water quality prediction, little effort has been placed in real-time demand estimation. This study presents a real-time demand estimation method using field measurement provided by supervisory control and data acquisition systems. For real-time demand estimation, a recursive state estimator based on weighted least-squares scheme and Kalman filter are applied. Furthermore, based on estimated demands, real-time nodal pressures and chlorine concentrations are predicted. The uncertainties in demand estimates and predicted state variables are quantified in terms of confidence limits. The approximate methods such as first-order second-moment analysis and Latin hypercube sampling are used for uncertainty quantification and verified by Monte Carlo simulation. Application to a real network with synthetically generated data gives good demand estimations and reliable predictions of nodal pressure and chlorine concentration. Alternative measurement data sets are compared to assess the value of measurement types for demand estimation. With the defined measurement error magnitudes, pipe flow data are significantly more important than pressure head measurements in estimating demands with a high degree of confidence.