Water Distribution Pipelines Research Articles

Protective measures against waterhammer in run-of-river hydropower plants

Waterhammer is an unsteady hydraulic problem which is commonly found in the penstocks of hydropower plants, water distribution networks and pipeline systems. Due to either a malfunction of the system or inadequate operation conditions, pipeline may collapse or burst. In this paper protective measures against waterhammer problems in the penstocks of small hydropower plants are investigated. In the study, a computer program employing method of characteristics is used to solve nonlinear partial differential equations of transient flow. In a case study, waterhammer response of a run-of-river hydropower plant under instant load rejection without a protective measure and with three different protective measures are analyzed. It is observed that, by means of protective measures waterhammer pressures in the penstock are substantially diminished, and it is shown that these measures are effective and practicable.

모형 재이용관을 이용한 하수재이용수의 부식 및 수질영향 연구

모형 재이용관을 이용한 하수재이용수의 부식 및 수질영향 연구

Recovering the Release History of a Pollutant Intrusion into a Water Supply System through a Geostatistical Approach

AbstractThis work addresses the issue of recovering the release history of a pollutant injection in water distribution systems through the application of geostatistical tools. Geostatistical tools are applied to the inverse problem of recovering the release history of a pollutant injected into a water distribution pipeline network in this paper. This application assesses the uncertainty in the concentration measurements and the release function by considering them as random variables characterized by their statistical moments. Performance of the geostatistical application to steady and unsteady flow conditions hinges on numerical modelling of the hydraulic behavior of the water distribution system and evaluation of a transfer function that characterizes the probability of contaminant migration at control points in the network. A sensitivity analysis is carried out and it proves that the methodology is stable with respect to measurement errors and uncertainty in the network description (roughness coefficie...

Criticality Analysis of Water Distribution Pipelines

An approach to evaluate the relative criticality of different pipes in a water distribution system is presented. To quantify the relative criticality of pipelines, a term, relative criticality index (RCI), has been defined and measured. RCI was developed by summing up the effects of reliability, cost of break repairs, and energy required to repair breaks in pipelines. These three components have been quantified and added appropriately to obtain an overall criticality index of pipelines in water distribution systems. The model is demonstrated by using a 9.4-square-mile area of a water distribution system comprising downtown Phoenix, Arizona. The overall system availability of the selected land use is found to be 46.6%, and the relative criticality index clearly indicates that galvanized steel pipes followed by regular steel and ductile iron pipes in the system are most critical (i.e., vulnerable). The analysis also presents predicted future costs and energy requirements to repair breaks in the water distribution system for a 20-year analysis period. The results indicate that the expenditures to repair system breaks for the analysis period is estimated to be $17.1 million. The energy required to repair breaks during the same time frame would be 2,486 MW·h. A relative criticality index, along with future requirements of critical resources, should aid cities in better planning and management of their water distribution systems.

Damage Ratio of Water Pipes during the 2007 Niigata-Ken Chuetsu-Oki, Japan, Earthquake

This study investigates the relationship between damage ratios of water pipes and seismic motion intensity after the 2007 Niigata-ken Chuetsu-oki, Japan, earthquake. The damage ratios of water distribution pipelines within a 2km radius from the seismic observation stations are calculated in Kashiwazaki City, Niigata Prefecture. The damage ratios are compared with the fragility curves that were empirically obtained after the 1995 Kobe earthquake. On the other hand, the damage ratios for the greater area are obtained with respect to the estimated seismic motion intensities. Based on the results, regression analyses are performed to reveal the characteristics of damage incidents to water pipes during the event.

Water Supply Performance and Fire Suppression during the World Trade Center Disaster

This paper describes the New York City water supply performance and suppression of fire during the World Trade Center (WTC) disaster. The water losses sustained by damaged water distribution pipelines are discussed and their impacts on emergency response and telecommunications and transportation infrastructure are noted. The results of hydraulic network analyses are presented to quantify the performance of hose and engine relay systems from fireboats to the WTC site. The results of an analytical study of firefighting relay systems are summarized to provide guidance on the most effective selection of hose size, number of hose lines, and engines for future use of fireboats for landside fire protection. The fire department response to the WTC disaster is compared with similar response to the 1989 Loma Prieta earthquake. Drawing on lessons from both events, recommendations are made for improved emergency planning and services.

Study on failure rate analysis for water distribution pipelines

Many of the waterworks facilities in Japan were constructed during the rapid economic growth period. Today, the deterioration and renovation of these aged facilities have become a pressing issue. There are approximately 600,000km worth of water pipelines laid out across Japan, accounting for about 70% of the nation's water-related assets (totalling ¥40 trillion). To provide water that is safe to use, it is necessary to improve and innovate water purification technologies; not only that, it is also vital to properly maintain and manage the pipelines. The current research aims to apply reliability engineering in the waterworks field as one possible approach and to show its viability; it will also obtain vital messages revealed within pipeline incident data. In other words, we collected the information concerning water distribution pipeline incidents through questionnaire surveys and then analysed the cumulative failure distribution (unreliability) by pipeline material, the failure probability density and failure rate, among others.

Bacteriological challenges to asbestos cement water distribution pipelines

Asbestos cement (AC) pipes were commonly installed in the drinking water distribution systems from the mid 1920s to the late 1980s. In recent years, an increase in the number of water main breaks has occurred in the AC portions of some pipe networks, which can be partially attributed to the corrosion of the aged pipes. This study evaluated the potential role that microorganisms may have played in the degeneration and failure of AC pipes. In this study, a fresh AC pipe section was collected from the distribution network of the City of Regina, Canada and examined for microbiological activities and growth on inside surfaces of pipe sample. Black slime bacterial growths were found to be attached to inner pipe surfaces and a distinctively fibrous internal coating (patina) with iron oxides was formed over the time. The microbial populations inside the patina and the black slime were tested with BART(tm) testers. Heterotrophic aerobic bacteria (HAB) and slime forming bacteria (SLYM) dominated in both the black growths and inside the patina. Iron related bacteria, denitrification bacteria and sulfate reducing bacteria were also commonly present. Microbial challenge assays were conducted by submerging the cut segments of the AC pipe into selected bacterial cultures for a period of 10 days under both aerobic and anaerobic environments. Weight changes were determined and the surface morphology was examined for each of the assayed pipe segments. Results indicated that acid producing bacteria, SLYM and HAB could facilitate the pipe weight loss under anaerobic environments.

Rapid Detection of Naegleria Fowleri in Water Distribution Pipeline Biofilms and Drinking Water Samples

Rapid detection of pathogenic Naegleria fowler in water distribution networks is critical for water utilities. Current detection methods rely on sampling drinking water followed by culturing and molecular identification of purified strains. This culture-based method takes an extended amount of time (days), detects both nonpathogenic and pathogenic species, and does not account for N. fowleri cells associated with pipe wall biofilms. In this study, a total DNA extraction technique coupled with a real-time PCR method using primers specific for N. fowleri was developed and validated. The method readily detected N. fowleri without preculturing with the lowest detection limit for N. fowleri cells spiked in biofilm being one cell (66% detection rate) and five cells (100% detection rate). For drinking water, the detection limit was five cells (66% detection rate) and 10 cells (100% detection rate). By comparison, culture-based methods were less sensitive for detection of cells spiked into both biofilm (66% detection for <10 cells) and drinking water (0% detection for <10 cells). In mixed cultures of N. fowleri and nonpathogenic Naegleria, the method identified N. fowleri in 100% of all replicates, whereastests with the current consensus primers detected N. fowleri in only 5% of all replicates. Application of the new method to drinking water and pipe wall biofilm samples obtained from a distribution network enabled the detection of N. fowleri in under 6 h, versus 3+ daysforthe culture based method. Further, comparison of the real-time PCR data from the field samples and the standard curves enabled an approximation of N. fowleri cells in the biofilm and drinking water. The use of such a method will further aid water utilities in detecting and managing the persistence of N. fowleri in water distribution networks.

Modeling of biofilm in the water distribution system

In order to understand the growth of biofilm and to serve as the basis of cleaning the water distribution pipeline, this study used a multi-attachment dynamic model to simulate the growth of microorganisms' attachment to the pipe wall. The model had considered attachment, detachment, and propagating factors. The attachment and detachment factors are divided into “cell to cell” and “cell to substratum”. Factors for biofilm growth included two possibilities, which was “lateral growth” and “vertical growth”. Data set of the biofilm biomass from a laboratory scale water distribution system was measured. The data and the model simulation curves were compared so as to justify the performance of the model. The results show that several sets of parameters could be identified. From the simulation of biofilm biomass in the pipeline, the microbial growth related with the incubation time. Due to nutrients being restricted, the biomass of biofilm in the water distribution system did not continue to grow and reached a maximum at about Day 40. From the simulation results, it was suggested the time of cleaning the water distribution pipeline be shortened to one or two months. The model was applied to simulate the tap water biofilm in the pipeline of Kaohsiung city, the second largest in Taiwan with 1.5 million population. The results revealed various levels of risks and the proportionality between the biomass in the water and the growth rate of biofilm. However, most households had the purifying facility of a reverse osmosis system. From the simulation, the facility proved its effectiveness for preventing the intervention of bacteria from the biofilm formation in the distribution pipelines.

Leak location using blind system identification in water distribution pipelines

This paper presents a new leak location method without knowledge of pipe length in water distribution pipes. In conventional leak location surveys using acoustic signals in buried water distribution pipelines, the most widely used techniques are based on the correlation technique. The prerequisite of the method is that the accurate length of pipeline between two detection points is known. However, in practice, this prerequisite is not always satisfied. Based on the fact that the acquired acoustic signals contain the characteristics related to the two propagation channels, the blind system identification strategy is applied to estimate the transmission performances of the two acoustic channels. Due to the long impulse response of acoustic channel, the overlap-save and cross-correlation fitting technique are utilized in blind system identification to estimate the acoustic channels under a built constraint condition. In order to avoid converging to the local minima, the genetic algorithm is adopted to optimize the channel identification. The times due to the propagation of the leak source signal traveling from the leak point to either sensor are extracted from the identified acoustic channels. Consequently, for leak location, the pipe length is no longer a prerequisite. The practical location results show the validness of the proposed scheme.

The genetic-algorithm-enhanced blind system identification for water distribution pipeline leak detection

The conventional leak location is based on the correlation of leak acoustic signals acquired spatially separately. By correlation, the time lag is estimated for localizing the leakage. In these methods, the detection distance is a prerequisite that has to be known beforehand. However, in practice, this prerequisite is not always satisfied. In this case, the correlation-based methods are not feasible. Actually, the acquired signals contain the characteristics related to the acoustic propagation channels; thus the blind system identification strategy is applied to estimate the transmission performances of acoustic channels. Then the times due to the propagation of the leak source signal travelling from the leak point to sensors are determined. In this way, for leak location, the detection distance is no longer a prerequisite. In blind system identification, due to the long impulse responses of the leak acoustic channels, the channels are inevitably ill conditioned and sensitive to the initial values. To overcome the ill conditions, the overlap-save and cross-correlation fitting techniques are utilized to identify the long impulse sequences under a built constraint. In order to avoid converging to the local minima, the genetic algorithm is used to minimize the cost functions. The practical detection results show the validity of the proposed scheme.

E.M.I Effects of Cathodic Protection on Electromagnetic Flowmeters

Electromagnetic flowmeters are used to measure the speed of water flow in water distribution systems. Corrosion problem in metal pipelines can be solved by cathodic protection methods. This paper presents a research on corruptive effects of the cathodic protection system on electromagnetic flowmeter depending on its measuring principle. Experimental measurements are realized on the water distribution pipelines of the Izmir Municipality, Department of Water and Drainage Administration (IZSU) in Turkey and measurement results are given. Experimental results proved that the values measured by the electromagnetic flowmeter (EMF) are affected by cathodic protection system current. Comments on the measurement results are made and precautions to be taken are proposed.

Design of water distribution networks using particle swarm optimization

Application of particle swarm optimization (PSO) is demonstrated through design of a water distribution pipeline network. PSO is an evolutionary algorithm that utilizes the swarm intelligence to achieve the goal of optimizing a specified objective function. This algorithm uses the cognition of individuals and social behaviour in the optimization process. For the optimization of water distribution system, a simulation – optimization model, called PSONET is developed and used in which the optimization is by PSO. This formulation is applied to two benchmark optimization design problems. The results are compared with the results obtained by other optimization methods. The results show that the PSO is more efficient than other optimization methods as it requires fewer objective function evaluations.

Ensuring the reliability of the water piping of the Moscow water supply system

The article describes the results of the investigation work carried out by Mosvodokanal Public Enterprise on improving the reliability of the water distribution pipelines in the city of Moscow. In recent years in Moscow there has been serious concern with regard to the reliability of its water supply network. This was caused by insufficient attention paid during the time of the former USSR to reliability and the operating conditions while designing and constructing the system as well as a period of increased rate of wear to the water pipes and insufficient financial resources for repairing the systems. The decrease in average daily supply, increasing capacities of the water pipelines, pumping stations and the cleanwells caused a whole series of technical problems. These included a reduction in water velocity, the formation of stagnant sections, slowdown of water renewal, and deterioration of water quality in the distribution system. This caused considerable difficulties and led to higher costs for the operation of the city water supply system. This article describes practical methods for preventing the unsatisfactory situation brought on by the decreased water consumption in Moscow. It describes the software used to evaluate water pipeline reliability and to plan the rehabilitation and renewal of the water supply system.

Northridge Earthquake Effects on Pipelines and Residential Buildings

This article is focused on the spatial variability of earthquake strong motion and its relationship with the performance of water-distribution pipelines provided by Los Angeles Department of Water and Power (ladwp) and residential buildings. Analyses of strong-motion characteristics and their correlations with pipeline and building damage were conducted with an immense geographical information system (gis) database for the 1994 Northridge earthquake, which was collected, digitized, and organized by researchers at Cornell. There are statistically significant correlations among pipeline repair rate (repairs/km) and peak ground velocity (pgv) for cast iron, ductile iron, asbestos cement, and steel pipe. Statistically significant regressions have been developed between damage ratio, dr (percent of existing structures with damage equal to or exceeding a particular damage factor, df [percent of building replacement cost]) and the magnitudes of seismic parameters, such as pgv and spectrum intensity (si). Regressions developed between dr and scaled seismic parameters (seismic parameters normalized with respect to df) resulted in predictive equations having a very high degree of statistical significance. Algorithms to visualize damage patterns for buildings were developed and validated to choose optimal gis mesh dimensions and contour intervals. Ordinary kriging was used to develop regressions of pipeline repair rate and residential building dr associated with 90% confidence pgv and spectrum intensity (weighted average pseudovelocity). Such regressions provide an explicit means of characterizing the uncertainty embodied in the strong-motion data.

Optimizing infrastructure network maintenance when benefits are interdependent

Network Topology Dependencies (NTD) are a class of externalities in the maintenance cost structure of infrastructure networks with applications to many network industries, including natural gas and water distribution pipelines. It is shown that the above externalities may be included to infrastructure maintenance decisions, if optimal maintenance is formulated as a Rhys-Balinski selection problem. A unique contribution is that this risk management problem is analyzed from the point of view of integrating quantitative analysis to organizational and inter-organizational decision processes. Hence, the importance of various procedural requirements is established in addition to computational efficiency and numerical accuracy. In particular, the benefits of sensitivity analysis facilitation and of avoiding manipulability are stressed. The proposed solution process achieves all four requirements. Special attention is paid to the role of submodularity and antitone differences in sensitivity analysis.

Evaluation of water supply system infested with chironomus larvae

A chironomus larvae infested water supply system was studied in detail for detecting its source and remediation. The study covered raw water source, units of water treatment plant, underground water storage reservoir, elevated service reservoir and water distribution pipeline. Since the larvae is the hatching of midge fly, the open ends in the water supply system like water treatment plant, underground storage reservoir, elevated service reservoir were studied first and found to be free from larvae. Finally excavation was carried out at the underground pipeline near the larvae infested tap ends. It was found that some residential units were discharging domestic wastewater just below the ground surface leading to contamination of drinking water. Pipe joints were opened for further study and growth of several species was found inside the pipe. However, the exact location of contamination could not be detected. The closed loop pipeline was opened at one end to scour off any contamination with clean water. After few hours of flushing, the insects were not detected at the consumer ends. This paper describes the systematic methodology that can be adopted for such investigations.

Prediction of corrosion rates of water distribution pipelines according to aggressive corrosive water in Korea

The drinking water network serving Korea has been used for almost 100 years. Therefore, pipelines have suffered various degrees of deterioration due to aggressive environments. The pipe breaks were caused by in-external corrosion, water hammer, surface loading, etc. In this paper, we focused on describing corrosion status in water distribution pipes in Korea and reviewing some methods to predict corrosion rates. Results indicate that corrosive water of lakes was more aggressive than river water and the winter was more aggressive compared to other seasons. The roughness growth rates of Dongbok lake showed 0.23 mm/year. The high variation of corrosion rates is controlled by the aging pipes and smaller diameter. Also the phenolphthalein test on a cementitious core of cement mortar lined ductile cast iron pipe indicated the pipes over 15 years old had lost 50-100% of their lime active cross sectional area.

Methodology for economically optimal replacement of pipes in water distribution systems: 1. Theory

While the idea of critical breaks rate (defined as the break rate after which it is no longer economical to continuously repair) of water distribution pipeline has been accepted in the literature and among practicing engineers, the formula to obtain the critical break rate has remained elusive. In this paper, an equation for identifying the critical break rate of a pipe is preseted. The Threshold (or critical) Break Rate equation gives an accurate criterion for pipe replacement decision. Input variables to obtain the Threshold Break Rate of a pipe are repair and replacement costs, interest rate, and the length and diameter of a pipe. The newly developed Threshold Break Rate equation does not involve time variable in its form resulting in incapability of predicting future optimal replacement time. This disadvantage of the Threshold Break Rate equation is overcome by establishing relations of equivalence between the Threshold Break Rate and other failure rate models such as the ROCOF (rate of occurrence of failure) and hazard function.