Search

The separate sewer system has led to severe river pollution because of domestic sewage infiltrations and initial rainfall pollution. Therefore, interception wells (IWs) are installed to divert sewage to the wastewater treatment plant but similarly contribute to overflow-induced river pollution on rainy days. The aim of the present study is to propose a control strategy for the regulation of IWs' overflow based on the online monitoring data, control measures, and software simulation. The results indicate that during light rain, overflow from the IWs is minimal, requiring no control measures. However during heavy rainfall, the overflow of sewage leads to an increase in the river's concentration of NH3-N from 0.25 to 3.04 mg/L. Finally, Simulations demonstrate a reduction in river NH3-N levels from 2.27 to 1.33 mg/L after implementation. The results indicated the substantial effectiveness of measures in mitigating the pollution originating from IWs' overflows during rainfall events. [ABSTRACT FROM AUTHOR]

Entrapped air pockets in water pipelines play a significant role in influencing transient over-pressures during filling procedures. Several research is focused on highlighting the attenuation of pressure peaks in pipes with single air pockets. This research studies the air-water interaction during rapid water filling processes in an irregular pipeline and air pockets in different branches, and how the trapped air can attenuate the over-pressure peaks. A three-dimensional computational fluid dynamics (CFD) model was developed, and numerical results of the model were validated through experimental measurements. For a given initial air pocket condition upstream of the high point, the maximum air pocket over-pressure was 11% to 32% lower when the descending pipe segment initially contains air compared to when it contains water. In sum, it was found that entrapped air pockets at high points of water pipelines can help mitigate transient over-pressures considering specific initial hydraulic conditions prior to filling operations. [ABSTRACT FROM AUTHOR]

Intermittent water supply systems are prone to air entrapments during the pipe filling phase. This work aims to analyse and discuss the numerical results obtained by applying the recently developed AirSWMM model, an extension of SWMM incorporating air phase, to a laboratory network. Experimental data consisting of pressure-head at multiple locations and video recordings of air entrapments are collected in a single loop network with a high point, for different pipe-filling conditions, system layouts and node elevations. Experimental tests have shown that the air entrapment occurred not only at the high point but also throughout the pipe network, creating air pockets with elongated shapes and larger volumes than for single pipes. AirSWWM model with air-entrapment formation, growth and transport is tested in the pipe network, and results are compared with measurements. AirSWWM model can correctly locate large air pockets but underestimates their volume. [ABSTRACT FROM AUTHOR]

This paper presents a novel decision support framework for water utilities to automatically create yearly pipeline rehabilitation plans while considering multiple parameters, including pipeline physical properties and other factors like transportation and urban space. The average age of urban water pipelines is growing, and the annual rehabilitation volumes are often lower than needed to improve or even preserve the level of service quality. The existing rehabilitation strategies range from simple pipe-age-based approaches to complex multiparameter strategies. The needed input of specific and detailed data, which are usually not available for water utilities, impedes a straightforward implementation of the latter strategies. Therefore, this study presents a two-step pipe rehabilitation strategy that enables the utility to automatically prioritise the pipes and related street areas/sections based on condition ranking. The strategy was validated on an operational water network in Tallinn, Estonia. [ABSTRACT FROM AUTHOR]

This study investigates the various components of groundwater recharge in an urban hard-rock aquifer system of Bengaluru, India. Groundwater meets more than fifty percent of the water demand in the city. This has led to an endangered situation of groundwater. Urbanization changes the source and path of groundwater recharge. Understanding the components of groundwater recharge is the foremost important step in groundwater management in an urban environment. Rotated empirical orthogonal function (REOF) analysis of ground water level data was used to identify the significant components of ground water level variation in the study area. Rainfall and pipeline leakage were identified as the major components of groundwater recharge in the study area. The stochastic interpolation method of ordinary kriging was used to regionalise the identified significant empirical orthogonal functions. [ABSTRACT FROM AUTHOR]

Water supply pipeline leakage is a major issue around the world. Leak detection and remediation can prevent water scarcity and some other problems. As a result, investigating pipeline leak-detecting technology has a high practical value. This study employs a promising technique for detecting pipeline leaks using Acoustic Emission (AE) signals. A dytran acceleration sensor was used to collect leakage signals in the time domain. The time-domain signal is transformed into a frequency domain by employing Fast Fourier Transform (FFT). The produced frequency signal has many dimensions which can be reduced to 17 by Principal Component Analysis (PCA). Intelligent leakage diagnosis techniques should eliminate time, and human intervention, and increase effectiveness. Machine learning (ML) models come into play at this point. To detect leakage, the hybrid ML model is proposed and it is compared with the conventional ML models. The best model for detecting water leakage is identified using the classification metrics. [ABSTRACT FROM AUTHOR]

This study examines the impact of sub-atmospheric pressures in water pipelines during emptying manoeuvres with air admitted. Previous research has looked at this issue but has not studied it in detail. This research presents a two-dimensional model using the OpenFOAM software to analyse different emptying manoeuvres in a single pipeline with entrapped air. The results show the sensitivity of the ball valve opening percentage, which show that absolute pressure drop can reduce to 23% for each 5% of ball valve opening percentage. The influence of the size of the entrapped air pocket and different air-admission orifices was also analysed. The numerical model showed that the selection of the percentage and times of opening drainage valves in pipelines with air-admission orifices is crucial in controlling sub-atmospheric pressure conditions. Finally, this study demonstrates the ability of the two-dimensional model to show the sensitivity of hydraulic drainage parameters in pipelines with entrapped air. [ABSTRACT FROM AUTHOR]

Water is one of the essential natural resources for survival, but the water transportation system faces significant challenges because of huge water loss due to leaky pipeline systems. An IoT based novel SWG prototype has been developed and reported in this work. The SWG comprises sensors and devices that can continuously and remotely monitor the pressure, temperature, flow, pH, turbidity, etc., of the water being transported. Moreover, a novel 1-D CNN model has been developed by creating an artificial leak on the pipeline that takes input data points as a chunk of 5-minute time series to the network and gives output in leak detection, location and size estimation simultaneously. Further, the developed model is compared with other state of the art machine learning techniques and the proposed model is found better in terms of accuracy which is 94.32%, 91.91% and 89.85% for leak detection, size estimation and location respectively. [ABSTRACT FROM AUTHOR]

In this research, the nonlinear behavior of a viscoelastic pipe during water hammer is investigated. To this end, the creep coefficients of the multiple element Kelvin–Voigt model have been determined for different flow rates and then they are incorporated to derive a holistic relation for the creep compliance. A linear interpolation scheme has been adopted to arrive at the holistic generalized Kelvin–Voigt model as a function of flow rates. The proposed relation is then applied in the established mathematical model and corresponding numerical solution to predict pressure fluctuations. The proposed approach in the application of the creep functions could capture the nonlinear material behavior during transients. Specifically, it revealed a higher creep behavior for higher loading rates (Joukowsky pressures) which was consistent with the experimental observations. Several numerical and experimental results were analyzed and investigated and to demonstrate the performance of the proposed approach. [ABSTRACT FROM AUTHOR]

A technical solution is developed to control stormwater runoff from plots in order to mitigate pluvial flood risk. Climate change alters precipitation patterns, which increase a risk for urban drainage systems (UDS) operating above their design limits. Therefore, feasible solutions are needed to retrofit UDSs to new climate conditions. In this study, street storage units (SSU) are coupled with a predictive real-time control algorithm to temporarily accumulate stormwater and thus minimise the risk of UDS surcharge. SSUs are operated in distributive mode and do not directly affect the flow in the pipeline, which makes the system less vulnerable to failures. SSUs are fully usable for citizens in dry periods. The results showed that control of 6% key inflows with SSUs reduced the number of flood nodes by 30% during an extreme weather event. The solution was successfully tested in Rakvere town, Estonia. [ABSTRACT FROM AUTHOR]

This paper introduces a new method for model calibration. The model calibration procedure is applied on water networks for leak detection and can be used for other inverse and model calibration problems. The calibration process uses Artificial Neural Networks to transform the measurements to a fixed network. This technique is compared to the conventional strategy where Artificial Neural Networks are used to predict the model parameters. The two techniques are compared on three networks of increasing complexity. The first is a fundamental single pipe network, the second is a numerical distribution network simulated using EPANET and the third is an experimental network. The results show that the newly introduced approach outperforms the other techniques. The presented technique is shown to perform well for the calibration of models. [ABSTRACT FROM AUTHOR]

A novel pressure-based leakage assessment and characterisation method was applied to a range of bulk pipelines in the field to evaluate the practical application of the method. With this method, the testing equipment, which consists of a variable speed pump unit, a water tank and measuring equipment, all mounted on a trailer, was connected to a bulk pipe which could be isolated. Flow was then introduced and regulated to maintain a range of set pressures, resulting in a pressure-leakage characteristic of the pipe. The test data was then interpreted using the modified orifice equation or FAVAD (Fixed and Varying Areas Discharges) concept. Fifteen pipes were assessed of which most showed significant or excessive leakage. By characterising the leakage of these pipes, useful information was obtained on the most likely leak types, sizes and possible locations. It was demonstrated that this is an effective, simple, quick and cost-effective leakage assessment method. [ABSTRACT FROM AUTHOR]

Filling and emptying processes are common maneuvers while operating, controlling and managing water pipeline systems. Currently, these operations are executed following recommendations from technical manuals and pipe manufacturers; however, these recommendations have a lack of understanding about the behavior of these processes. The application of mathematical models considering transient flows with entrapped air pockets is necessary because a rapid filling operation can cause pressure surges due to air pocket compressions, while an uncontrolled emptying operation can generate troughs of sub-atmospheric pressure caused by air pocket expansion. Depending on pipe and installation conditions, either situation can produce a rupture of pipe systems. Recently, reliable mathematical models have been developed by different researchers. This paper reviews and compares various mathematical models to simulate these processes. Water columns can be analyzed using a rigid water column model, an elastic water model, or 2D/3D CFD models; air–water interfaces using a piston-flow model or more complex models; air pockets through a polytropic model; and air valves using an isentropic nozzle flow or similar approaches. This work can be used as a starting point for planning filling and emptying operations in pressurized pipelines. Uncertainties of mathematical models of two-phases flow concerning to a non-variable friction factor, a polytropic coefficient, an air pocket sizes and an air valve behavior are identified. [ABSTRACT FROM AUTHOR]

The prediction of the pressure inside the air pocket in water pipelines has been the topic for a lot of research works. Several aspects in this field have been discussed, such as the filling and the emptying procedures. The emptying process can affect the safety and the efficiency of water systems. Current research presents an analysis of the emptying process using experimental and computational results. The phenomenon is simulated using the two-dimensional computational fluid dynamics (2D CFD) and the one-dimensional mathematical (1D) models. A backflow air analysis is also provided based on CFD simulations. The developed models show good ability in the prediction of the sub-atmospheric pressure and the flow velocity in the system. In most of the cases, the 1D and 2D CFD models show similar performance in the prediction of the pressure and the velocity results. The backflow air development can be accurately explained using the CFD model. [ABSTRACT FROM AUTHOR]

Small leaks in buried water distribution pipelines run continuously for long periods of time without being detected. They do not produce any appreciable flow or pressure changes at the monitored locations. The non-stationarity of the monitoring data, background noise, and the uncertainties in interpreting sensory information adds complexity to detecting leaks. This paper explores the application of singular spectrum analysis (SSA) in extracting leak components from noisy measurements. SSA is a non-parametric and adaptive method, able to decompose a signal into interpretable components without making linearity or stationarity assumptions. When applied to noisy hydro-acoustic signals, it is shown that the leak signatures are extracted efficiently. A semi-supervised approach for leak detection is presented, in which the SSA decomposition of leak-free historical data is combined with ensemble one-class support vector machine. The results demonstrate the effectiveness of SSA for leak detection in water distribution pipelines. [ABSTRACT FROM AUTHOR]

Integrated Urban Water Management (IUWM) approach is an important strategy for urban water utilities to improve water security and system resilience. This study proposes a novel approach to combine recycled water and stormwater. This novel mixing method of capturing and treating stormwater at various locations along the recycled water pipeline and injecting treated stormwater in to the recycled water pipe line is unknown to have been practiced anywhere in the world. Water quality control of combined water is a vital factor for the safe use, as mixing percentage of stormwater is decided based on availability. A method to determine the water quality before mixing is required. Therefore, this paper investigates the appropriateness of the mass balance method to compute combined water quality and proposes a guideline for water quality of combined water. [ABSTRACT FROM AUTHOR]

This paper presents the validation of a novel leak detection method for water distribution pipelines, although it could be applied to any buried pressurized fluid flow pipe. The detection method is based on a relative pressure sensor attached non-invasively to the outside of the pipe combined with temperature difference measurements between the pipe wall and the soil. Moreover, this paper proposes an anomaly detection algorithm, originally developed for monitoring website traffic data, which differentiates a ‘leak’ event from ‘normal’ pressure change events. It is compared to two more commonly used methods based on a fixed threshold and a moving average. The validation of the new system in a field trial over a 6-month period showed that all the known leaks were identified with 98.45% accuracy, with the anomaly detection algorithm performing best, making this system a real contender for leak detection in pipes. [ABSTRACT FROM AUTHOR]

Automatic leak localization has been suggested to reduce the time and personnel efforts needed to localize (small) leaks. Yet, the available methods require a detailed demand distribution model for successful calibration and good leak localization performance. The main aim of this work was to analyze whether such a detailed demand distribution is needed. Two demand distributions were used: a factorized distribution that distributes the inflow demand proportionally across the consumption nodes according to individual billing data, and a uniform distribution that equally distributes demand across all consumption nodes. The performance of the automatic leak localization method, using both demand distribution models, was compared. A new measure for leak localization performance that is based on the percentage of false positive nodes is proposed. It was possible to localize the leaks with both demand distribution models, although performance varied depending on the timing and duration of the measurement. [ABSTRACT FROM PUBLISHER]

This paper provides an overview of the work performed in the last 13 years to predict the failure of large-diameter trunk water mains. Large-diameter water mains, defined as water mains with a diameter greater than 500 mm, form the main transmission lines in most water distribution systems. The consequences of their failure can be severe and costly. In order for predictive models to be applicable to large-diameter water mains, all models reviewed are capable of analysing individual pipes or pipe segments and calculate either an absolute probability of failure or the hazard of failure relative to other pipes in the system. These models can be divided into two broad categories: physical and statistical models. This review provides a description and a brief critique for each model presented. [ABSTRACT FROM AUTHOR]

This paper approaches the optimisation of looped water distribution networks supplied from one or more sources, according to demand variation. The pipe networks have concentrated outflows or uniform outflow along the length of each pipe. An optimisation model coupled with a computational iterative procedure of optimal discharges through pipes is developed on the basis of linear programming for the design of new or partially extended water distribution networks. The optimum solution obtained by this model consists of one or two pipe segments of different discrete sizes between each pair of nodes. The improved linear optimisation model guarantees a high reliability. Also, it is possible to take into account the network pipes with variable discharge on route. Additionally, the paper compares the linear optimisation model to some others, such as the classic model of economical velocities, the Moshnin model and a nonlinear model. This shows a good performance of the proposed model. [ABSTRACT FROM PUBLISHER]

Water pipelines need to be systematically monitored in order to minimize losses from possible leakages. In this paper, remote sensing techniques have been exploited in semiarid areas of Cyprus. In addition, ground spectroradiometer has been used to define the leakage's threshold values. The data were analysed in a GIS environment. Two known leakage problems have been examined. In the first case study, a high resolution QuickBird image was used for the detection of the exact point of leakage. In the second case study a multi-temporal analysis was performed using SPOT images. This methodology was able to record 10 possible leakage points along the pipeline. Throughout the 25 km length of the pipeline, the in-situ observations were minimized to only 0.4%. In both studies the Normalised Difference Vegetation Index (NDVI) was applied. The final outcomes highlight the contribution of remote sensing to the early detection of leakages especially in difficult and near inaccessible areas. [ABSTRACT FROM AUTHOR]

Tap water discolouration occurs due to resuspension of loose deposits (LD) that accumulate in drinking water distribution systems. Strategies for discolouration control involve network pipe cleaning and replacement of cast-iron pipes. However, the sole application of such measures is not generally effective. Therefore, a deeper understanding on processes associated with LD origin and development is required. Transparent (but covered) test rig pipes (Ø = 23 mm) continuously supplied with drinking water at steady flow through mode (7–9 months) were used to investigate LD build-up under laminar flow (0.2–4.1 cm/s) conditions. Rather than continuously and homogeneously, LD developed as spots, and predominantly at the pipes' bottom. Results suggested that particle attachment may be added to settling as a LD build-up process. This is consistent with LD cohesive–adhesive properties, as shown by LD repose angle tests, as well as to the occurrence of flocculent extracellular polymeric substances-EPS in LD. [ABSTRACT FROM AUTHOR]

This paper intends to provide a detailed methodology on the development of the optimization model including reliability for design of water distribution networks using genetic algorithms (GA) and EPANET in the MATLAB environment. The coding developed is easy to use and also flexible. A new parameter is proposed to determine the overall network reliability using network nodal demands and their corresponding satisfaction indices and is incorporated in the optimization model. The proposed methodology is tested on a standard Hanoi network. After several runs and out of many optimal solutions obtained, the solution with a total cost of 7.78 million associated with a reliability of 0.7323 is considered as the best and the corresponding results are presented and compared with previous research. [ABSTRACT FROM PUBLISHER]

Pressure measurements provide valuable insights for managing water supply systems by tracking time-dependent hydraulic transients. In this study, we report on two pressure-monitoring issues – sampling location and sampling interval – by analyzing a valve-induced transient event that was not recorded in the 1-min timestamp pressure generated by the existing supervisory control and data acquisition (SCADA) system of a real water transmission line in the southern part of Korea. Field measurement data show that the measured pressure magnitude is influenced by the sampling location, which depends on pipe connectivity and distance from automatic control valve, and by the sampling interval, which is sensitive to network size for wave propagation. Based on the findings of the field experiments, a pressure-measurement method is proposed by employing numerical transient simulation and spectral analysis of pressure waves. [ABSTRACT FROM PUBLISHER]

This paper shows how it is possible to represent the link between the leakage from a pipe and the internal pipe pressure by relying on the classical Torricelli equation, which is valid for a thin-walled orifice with complete contraction, provided that a correction is introduced to take account both of the potential deformation of the leak opening and hydraulic factors which alter the coefficient of discharge. The quantities that contribute to determining this correction coefficient and its form are identified by means of the Buckingum π theorem combined with an evolutionary technique. The Buckingum π theorem enables the dimensionless outflow to be placed in relation with potential quantities describing the material, the leak size and shape, etc., all of which are dimensionless so as to lend the relationship general validity. The evolutionary technique used to define the form, or equation, of this corrective coefficient is the Evolutionary Polynomial Regression (EPR), which enables the form and parameters of the equation searched for to be defined simultaneously. The data necessary for the study were drawn from laboratory tests using two different elastic materials (steel and u-PVC), two diameters and two different leak shapes, each with different dimensions. The results obtained confirm the validity of the theoretical approach and support the possibility of writing a singleQ-hrelationship that is valid for varying materials, diameters and leak shapes and sizes. [ABSTRACT FROM PUBLISHER]

Ultrasound, closed-circuit television (CCTV) and Panoramo®are capable of inspecting drinking water pipes and joints of any pipe material. The three tools were tested for their accuracy and reproducibility for gap width sizing in double-socket push-fit joints. The tests were performed at laboratory scale (PVC pipes and joints) in the field (asbestos cement pipes and joints) and in three full-scale tests (PVC) inside pipes used to supply drinking water. In the laboratory tests both accuracy and reproducibility were evaluated. In the field and full-scale tests only reproducibility of the tools was tested. CCTV proved to be the most accurate and reproducible for the application. This straightforward approach is considered to be a surrogate measure for joint's condition. [ABSTRACT FROM PUBLISHER]

Networks for water and wastewater transport represent large capital assets and material stocks within cities. A better understanding of how their material content changes with population and size of the city may help to design networks with lower resource demand and lower construction and maintenance costs. We estimated the total length and mass for the wastewater networks of 25 cities in five different countries using a fractal network model that only requires the cities' size and population as input data. We found that most of the network mass is concentrated in the main trunk lines. The model results showed efficiency of scale: For a catchment area of constant size, both network length and mass per capita would decline if population grew. However, if the population of a city grew while the population density remained constant or decreased (urban sprawl), the per-capita network mass would increase. [ABSTRACT FROM PUBLISHER]

New experimental results obtained from a high density polyethylene (HDPE) pipeline for transient conditions are presented and discussed. Transient pressure data at different pipe sections were collected. Peculiar features were observed, which are typical of viscoelastic pipes, in particular, a significant damping of extreme pressures was observed in comparison to what is typically obtained for metal pipes. Physical constraints of the pipe are important to describe some vibrations observed in the system. The viscoelastic transient solver developed by Covaset al.(2005) was used to carry out numerical simulations of experimental tests. The comparison of numerical results with experimental data has shown that the viscoelastic model accurately predicts observed transient pressures. Additional considerations are carried out about the calibrated creep function for this test case in comparison with the ones obtained in previous researches. [ABSTRACT FROM AUTHOR]

A key objective of water supply systems is to provide potable water to consumers at an appropriate quality, however, through distribution networks, water quality can be compromised. One of the avenues through which this can happen is contaminant intrusion into the network. Through hydraulic modelling, this paper examines how potential intrusion into water distribution networks can be established and also predicts the magnitude of intrusion that is expected to occur, given particular conditions. The paper further suggests possible preventive measures that can be taken in order to avert the occurrence of this phenomenon. Results indicate that for potable water pipelines flowing through high pressure areas, if the pressure of the surrounding environment can be established then by ensuring that network pressures are above the surrounding pressures in those sections of the network, intrusion can be overcome. [ABSTRACT FROM AUTHOR]

In this paper, a new method is proposed to detect leaks in the presence of the non-leak noise inside or outside a pipeline. Due to the ability to analyze the coherent structure of time series, the autocorrelation function is used to describe the self-similarity feature of the leak signal. The values of the autocorrelation function for the laglarger than the correlation length of the signal, not the signal itself or the entire autocorrelation function, are used to extract or evaluate the self-similarity degree of the signal by the approximate entropy. Based on feature extraction, a new detection function related to autocorrelation functions of the acquired signals is built to detect leak. Then a neural-network approach is utilised as a classifier to discriminate the leak signals from the non-leak signals inside and outside pipes. The proposed method has been employed to detect leak in the presence of the non-leak noises inside and outside pipes, and achieved a 93.8% and 86.3% correct detection rate, respectively. [ABSTRACT FROM AUTHOR]

Water saving is not just the responsibility of the consumer. While demand-side management prescribes several good practices for water-consumers, the supplier also understands that leakage reduction on its part is a more effective mode of saving large quantities of water, by having to abstract, treat and supply less. It is not just water which is saved, but money spent on chemicals and energy expended on treatment and pumping. The economic aspect apart, this also means that there are possibilities of significant reductions of environmental impacts upstream in the chemicals production and energy generation processes. However, it is not an easy task to perform a comprehensive cost-benefit analysis, by taking into account all the direct and indirect costs and benefits. Benefits besides are not just multi-pronged but also distributed over time. In this paper, the author compares the direct costs incurred in rehabilitating old water pipelines in Oslo, with the direct benefits of leakage reduction which accrue therefrom, for the period 2011–2020. Avoided greenhouse gas emissions by virtue of savings in energy and chemicals are compared with the greenhouse gas emissions which occur due to the rehabilitation operations. It is seen that it often becomes difficult to justify rehabilitation economically, if the direct and indirect monetary benefits in addition those accruing from leakage reduction alone are not taken into consideration. Interestingly, the net savings in GHG emissions are significant, even over the 10-year study period. [ABSTRACT FROM AUTHOR]