• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 123
  • 65
  • 18
  • 10
  • 8
  • 4
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 296
  • 296
  • 81
  • 72
  • 64
  • 62
  • 56
  • 46
  • 45
  • 43
  • 38
  • 38
  • 33
  • 33
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Avaliação do controle de perdas físicas em redes de distribuição de água da região metropolitana de São Paulo / Evaluation of control physical losses in water distribution networks in the metropolitan region of São Paulo

Diniz, Aldo Roberto Silva 09 March 2012 (has links)
Orientador: José Gilberto Dalfre Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-21T12:04:12Z (GMT). No. of bitstreams: 1 Diniz_AldoRobertoSilva_M.pdf: 2375146 bytes, checksum: 0af05ce5634ce83e9d2b7af8c30a2179 (MD5) Previous issue date: 2012 / Resumo: O presente trabalho apresenta uma avaliação de um método para o controle de perdas físicas de água, caracterizando-as, de maneira a priorizar as ações de combate e redução de perdas físicas. Para o desenvolvimento do trabalho, foi realizada uma ampla revisão bibliográfica, em que é apresentada a conceituação geral sobre perdas de água, suas causas e ocorrências, indicadores, ações para redução, e uma abordagem detalhada quanto aos métodos existentes para avaliação de perdas e as ferramentas disponíveis. O método de avaliação para o controle das perdas físicas baseia-se no balanço hídrico, utilizando o software gratuito desenvolvido pela AWWA (American Water Works Association, Water Audit 4.0) e foi aplicada no estudo de caso do sistema de abastecimento de água da Região Metropolitana de São Paulo (RMSP), denominado setor Casa Verde. Foram levantados os dados de controle do sistema e realizados os ensaios de campo, com medições de pressão para determinação do local dos vazamentos não visíveis, auxiliando na sua caracterização e permitindo a priorização das ações de combate às perdas físicas. Os resultados do diagnóstico da localização das perdas foram analisados, desenvolvendo-se uma estratégia para a redução de perdas físicas / Abstract: This paper presents an evaluation method for the control of physical losses of water, aiding in determining the profile of losses, allowing for better prioritization of actions to combat and reduce physical losses. For the development of this evaluation was performed an extensive literature review, where it shows a general concept on water loss, its causes and events, indicators, actions to reduce, and as a comprehensive approach to existing methodologies to assess losses and tools available. The assessment of physical losses presented here is the beginning through the water balance, using free software developed by AWWA (American Water Works Association, Water Audit 4.0), was applied to the water supply system in the Metropolitan Region of São Paulo (MRSP) industry called Casa Verde. Data were the basic control system and field trials carried out with pressure measurements and tests to determine the location of leaks not visible. The assessment was applied in a supply sector of the northern area of the metropolitan region, with characteristics of controlled pressure. Diagnostic results of the losses were consistent with expectations. Depending on the results for this sector should be developed a specific strategy for the reduction of physical losses and method for controlling physical losses of water, aiding in determining the profile of losses, allowing for better prioritization of actions to combat and reduce physical loss / Mestrado / Recursos Hidricos, Energeticos e Ambientais / Mestre em Engenharia Civil
222

Risk assessment of contaminant intrusion into water distribution system

Yan, Jimin January 2006 (has links)
It is recognised through current literature that contaminantin trusion is a primary threat leading to degradation of water quality and threat to human health. The problem is more serious in developing countries where the water supply is intermittent and water distribution system crisscross with sanitary systems. Therefore there is a need to develop the methodology that enables the decision makers and engineers to undertake actions to minimise the risk of contamination of water. The researchs tudy presentedin this thesis addresses these water quality issues by developing the appropriate modelling tools to minimize the risk of contaminant intrusion. The conceptual framework proposed in this study consists of a risk based approach where the process of contaminant intrusion into the systems is traced to know the hazards of contaminant intrusion and vulnerability of the system. The risk of contaminant intrusion into the pipes of a water distribution system is then estimated as the function of hazards and vulnerability. A suit of four models is developed based on this framework. The first model is a water distribution pipe condition assessment model that simulates the potential pathway for contaminant ingress into water pipes by relating it to the deterioration/condition of the pipes. The condition of each pipe is assessed by means of numerous factors related to physical, environmental and operational aspects of the water distribution system. These factors are grouped into different indicators at three levels, depending on the nature of influence of each factor on the deterioration process of the pipe. The uncertainties inherent in these pipe condition indicators are described with fuzzy set theory. A distance based multi-criteria decision making method-fuzzy composite programming has been applied to combine the multilevel pipe condition indicators to form a single indicator to rank the condition of the pipes. The second model is a water flow and contaminant transport modelling tool. This model predicts the envelope of pollution emanating from pollution sources (contaminant zone) and simulates the seepage and contaminant transport in this zone. It is assumed that the seepage of contaminant from pollution sources such as unlined canal/drains and surface water bodies follow saturated flow while from pollution sources such as sewer pipelines, lined canals/drains follow unsaturated flow. Accordingly Richard/Green Ampt equations (unsaturated flow) and Darcy's equation (saturatedf lows) are coupled with advection-diffusion equations that account for water flow and contaminant transport respectively. The third model, the contaminant ingress model, identifies sections of pipe of water distribution system within contaminant zone by combining the outputs from the contaminant seepage model with spatial analysis. The fourth model, the risk assessment model, identifies the risk of contaminant intrusion into a water distribution system from the outputs of the above three models, namely the vulnerability of the water distribution pipe (pipe condition assessment model), the contaminant concentration(contaminant seepage model) and section of pipe in contaminant zone (contaminant ingress model). All these models have been integrated into ArcView GIS to form a decision support system (Improved Risk Assessment of Water Distribution System) and applied to a real water distribution system in Guntur, India for which water pipe network data and data for pollution sources were collected. The modelling results are presented as risk maps that show the potential areas that are under threat of contamination with relative risk scores. It is envisaged that the developed modelling tools will be used by water utilities in developing countries to improve the water quality management by identifying vulnerable areas and understanding threats that exist to the water distribution systems.
223

Prioritization of Potable Water Infrastructure Investments on the Navajo Nation

Chee, Ronson Riley, Chee, Ronson Riley January 2017 (has links)
Notorious for its high poverty levels and low socio-economic status, the Navajo Nation’s socio-economic well-being is hindered greatly in part by the lack of an adequate potable water infrastructure which has resulted in health disparities and has attributed to stunted economic growth within the Nation. Large candidate regional water transmission pipelines projects aimed to meet these needs have been identified. With capital costs exceeding their fiscal capability, decision-makers must choose projects that generate the most bang for the buck. To address these challenges, three (3) interconnected planning tools have been developed: (1) a water pipe installation construction cost estimation model (WaterCOSTE) to improve the accuracy of capital cost estimates; (2) a hydraulic optimization model (WaterTRANS) that improves design efficiency for branched water transmission systems; and (3) a decision support system (DSS) that allows candidate water transmission projects to be ranked while considering economic development, health improvement and environmental protection objectives. Estimates derived from WaterCOSTE are used as input into WaterTRANS to find least-cost system designs. The system costs along with other project data are then input into the DSS to determine project rankings. To demonstrate how the DSS can be used and applied, two candidate projects on the Navajo Nation are evaluated. The tools developed will enable decision-makers to improve planning processes and make wiser investment decisions that will lead to expanding the water infrastructure coverage and living conditions on the Navajo Nation.
224

Optimisation des tours d’eau sur un réseau de canaux d’irrigation / Optimization of water distribution schedules for open-channel irrigation networks

Hong, Sothea 11 July 2014 (has links)
La plupart des réseaux d'irrigation gravitaire traditionnels, encore majoritaires dans le monde, distribuent l'eau aux parcelles agricoles à travers un réseau de canaux à surface libre. La distribution de l'eau sur ce type de réseau suit en général le mode de distribution au tour d'eau (tour d'eau fixe, modulé, arrangé ou mixte) et nécessite de définir un planning de manœuvre des vannes et un calendrier d'arrosage. La performance de la distribution d'eau est généralement très faible, du fait de contraintes de l'infrastructure, de main d'œuvre et d'évolutions des demandes en eau.La thèse propose une méthode générique permettant d'optimiser les manœuvres des vannes et le calendrier d'arrosage, ainsi que des stratégies de modernisation basées sur la mise en place de vannes automatiques et réservoirs tampon.La méthode est basée sur la programmation linéaire en variables mixtes (MILP). La définition des contraintes et des objectifs s'appuie sur l'analyse de deux périmètres traditionnels du Sud de la France, ainsi que sur une description des principales caractéristiques hydrauliques des systèmes de transport d'eau. Les méthodes prennent en compte trois critères d'optimisation : l'adéquation, la main d'œuvre et l'efficience hydraulique, ces critères pouvant être pondérés pour tenir compte de priorités.La méthode développée est testée sur un réseau virtuel, puis appliquée à un système réel où les évolutions récentes ont profondément dégradé l'adéquation offre-demande. La méthode permet alors de réduire fortement les volumes d'eau prélevés en tête de réseau mais non utilisés par les usagers, tout en assurant une très bonne adéquation offre-demande.L'enjeu de la modernisation des réseaux traditionnels est abordé sur un réseau au tour d'eau fixe, fortement contraint par la charge de travail pour manœuvrer les ouvrages. On montre, sur un site réel, comment définir des priorités de mise en place de vannes automatiques. Dans d'autres cas, la modernisation peut se faire par la mise en place de réservoirs tampon dont l'emplacement et le volume peuvent être optimisés. / Most traditional gravity irrigation networks, still the majority in the world, deliver water to farm field (offtakes) through an open channel network. Water distribution on this type of network is generally based on irrigation schedule/delivery methods (fixed rotation, central system, arranged or mixed schedule) and requires two schedules: one for irrigation and another for gate operations. Water distribution performance of this system is low due to hydraulics infrastructures constraints, manpower and water demand evolution.The thesis proposes a generic method for optimizing gate operations and irrigation schedules, as well as modernization strategies based on the development of automated gates and buffer reservoirs.The method uses mixed integer linear programming (MILP). The definition of constraints and objectives is based on the analysis of two traditional irrigation networks of Southern France, as well as a description of the main characteristics of hydraulic systems for water delivery. Methods take into account three optimization criteria: adequacy, hydraulic efficiency and manpower. These criteria can be weighted for setting the priorities.The developed method is tested on a virtual network, and then applied to a real system where recent evolution have profoundly damaged the adequacy between supply and demand. We show that the method can greatly reduce the volume of water withdrawn by the network, and not used by users, for ensuring a good adequacy between supply and demand.The challenge of modernization is taken into account for an open channel network which is strongly constrained by manpower for gates operations. It is shown on a real network, how to set priorities for implementation of automatic gates. In other cases, the modernization may be achieved by the implementation of the buffer reservoir which location and volume can be optimized.
225

Multikriteriální hodnocení technického stavu vybraných částí vodovodů / Multi-objective condition assessment of selected parts of water distribution systems

Tauš, Miloslav Unknown Date (has links)
The topic of the thesis is multi objective condition assessment of water supply systems. The state of the art of condition assessment of water supply systems and the state of the art of multi objective optimization methods are presented within the thesis. Based on these recherches, the uniform methodology of condition assessment of water supply systems and its 7 modules was designed. The thesis deals with the selected modules to condition assessment of water pumping stations, water networks and pipe sections. The output of the methodology is the assignment of a category of the technical condition to the rated object. The proposed methodology was tested on real water facilities and proves the ability of a fair presentation of the technical condition of the object.
226

Vliv tlakových poměrů ve vodovodní síti na spotřebu vody / Impact of pressure condition on water consuption in water distribution network

Straňák, Petr January 2019 (has links)
The diploma thesis deals with effect of pressure conditions in the water supply network on consumption of drinking water. The introductory part describes how pressures affect water consumption and six studies from different countries carried out on real network are presented. Further, the work is devoted to other factors influencing water consumption and distribution of domestic water consumption. The practical part deals with the laboratory measurement of the influence of pressure change on tested discharge fittings for flowing and dripping water. The results are also expressed in annual costs and a method is presented how the effect of pressure change can be quantified if we know the average daily consumption and its distribution.
227

A Comparison of Risk Assessment Models for Pipe Replacement and Rehabilitation in a Water Distribution System

Nemeth, Lyle John 01 June 2016 (has links)
A water distribution system is composed of thousands of pipes of varying materials, sizes, and ages. These pipes experience physical, environmental, and operational factors that cause deterioration and ultimately lead to their failure. Pipe deterioration results in increased break rates, decreased hydraulic capacity, and adverse effects on water quality. Pipe failures result in economic losses to the governing municipality due to loss of service, cost of pipe repair/replacement, damage incurred due to flooding, and disruptions to normal business operations. Inspecting the entire water distribution system for deterioration is difficult and economically unfeasible; therefore, it benefits municipalities to utilize a risk assessment model to identify the most critical components of the system and develop an effective rehabilitation or replacement schedule. This study compared two risk assessment models, a statistically complex model and a simplified model. Based on the physical, environmental, and operational conditions of each pipe, these models estimate the probability of failure, quantify the consequences of a failure, and ultimately determine the risk of failure of a pipe. The models differ in their calculation of the probability of failure. The statistically complex model calculates the probability of failure based on pipe material, diameter, length, internal pressure, land use, and age. The simplified model only accounts for pipe material and age in its calculation of probability of failure. Consequences of a pipe failure include the cost to replace the pipe, service interruption, traffic impact, and customer criticality impact. The risk of failure of a pipe is determined as the combination of the probability of failure and the consequences of a failure. Based on the risk of failure of each pipe within the water distribution system, a ranking system is developed, which identifies the pipes with the most critical risk. Utilization of this ranking system allows municipalities to effectively allocate funds for rehabilitation. This study analyzed the 628-pipe water distribution system in the City of Buellton, California. Four analyses were completed on the system, an original analysis and three sensitivity analyses. The sensitivity analyses displayed the worst-case scenarios for the water distribution system for each assumed variable. The results of the four analyses are provided below. Risk Analysis Simplified Model Complex Model Original Analysis All pipes were low risk All pipes were low risk Sensitivity Analysis: Older Pipe Age Identified 2 medium risk pipes Identified 2 medium risk pipes Sensitivity Analysis: Lower Anticipated Service Life Identified 2 medium risk pipes Identified 9 high risk pipes and 283 medium risk pipes Sensitivity Analysis: Older Pipe Age and Lower Anticipated Service Life Identified 1 high risk pipe and 330 medium risk pipes Identified 111 critical risk pipes, 149 high risk pipes, and 137 medium risk pipes Although the results appeared similar in the original analysis, it was clear that the statistically complex model incorporated additional deterioration factors into its analysis, which increased the probability of failure and ultimately the risk of failure of each pipe. With sufficient data, it is recommended that the complex model be utilized to more accurately account for the factors that cause pipe failures. This study proved that a risk assessment model is effective in identifying critical components and developing a pipe maintenance schedule. Utilization of a risk assessment model will allow municipalities to effectively allocate funds and optimize their water distribution system. Keywords: Water Distribution System/Network, Risk of Failure, Monte Carlo Simulation, Normal Random Variable, Conditional Assessment, Sensitivity Analysis.
228

A simulation-based multi-criteria management system for optimal water supply under uncertainty

Tinh, Pham Van 28 April 2015 (has links)
For cost and reliability efficiency, optimal design and operation of pressurized water distribution networks is highly important. However, optimizing such networks is still a challenge since it requires an appropriate determination of: (1) dimension of pipe / pump / tank - decision variables (2) cost / network reliability - objective functions and (3) limits or restrictions within which the network must operate - a given set of constraints. The costs mentioned here consist in general of capital, construction, and operation costs. The reliability of a network mainly refers to the intrinsic capability of providing water with adequate volume and a certain pressure to consumers under normal and extreme conditions. These contradicting objective functions are functions of network configuration regarding component sizes and network layout. Because considerable uncertainties finally render the overall task to a highly complex problem, most recent approaches mainly focus only on finding a trade-off between minimizing cost and maximizing network reliability. To overcome these limitations, a novel model system that simultaneously considers network configuration, its operation and the relevant uncertainties is proposed in this study. For solving this multi-objective design problem, a simulation-based optimization approach has been developed and applied. The approach couples a hydraulic model (Epanet) with the covariance matrix adaptation evolution strategy (CMA-ES) and can be operated in two different modes. These modes are (1) simulation–based Single-objective optimization and (2) simulation-based multi-objective optimization. Single-objective optimization yields the single best solution with respect to cost or network reliability, whereas multi-objective optimization produces a set of non-dominated solutions called Pareto optimal solutions which are trade-offs between cost and reliability. In addition, to prevent a seriously under-designed network, demand uncertainties was also taken into account through a so called “robustness probability” of the network. This consideration may become useful for a more reliable water distribution network. In order to verify the performance of the proposed approach, it was systematically tested on a number of different benchmark water distribution networks ranging from simple to complex. These benchmark networks are either gravity-fed or pumped networks which need to be optimally designed to supply urban or irrigation water demand under specific constraints. The results show that the new approach is able: • to solve optimization problems of pressurized water distribution network design and operation regarding cost and network reliability; • to directly determine the pumping discharge and head, thus allowing to select pumps more adequately; • to simulate time series of tank water level; • to eliminate redundant pipes and pumps to generate an optimal network layout; • to respond well to complex networks other than only to simple networks; • to perform with multiple demand loading; • to produce reliable Pareto optimal solutions regarding multi-objective optimization. In conclusion, the new technique can be successfully applied for optimization problems in pressurized water distribution network design and operation. The new approach has been demonstrated to be a powerful tool for optimal network design not only for irrigation but also for an urban water supply.
229

Drinking Water Microbial Communities

El-Chakhtoura, Joline 11 1900 (has links)
Water crises are predicted to be amongst the risks of highest concern for the next ten years, due to availability, accessibility, quality and management issues. Knowledge of the microbial communities indigenous to drinking water is essential for treatment and distribution process control, risk assessment and infrastructure design. Drinking water distribution systems (DWDSs) ideally should deliver to the consumer water of the same microbial quality as that leaving a treatment plant (“biologically stable” according to WHO). At the start of this Ph.D. program water microbiology comprised conventional culturedependent methods, and no studies were available on microbial communities from source to tap. A method combining 16S rRNA gene pyrosequencing with flow cytometry was developed to accurately detect, characterize, and enumerate the microorganisms found in a water sample. Studies were conducted in seven fullscale Dutch DWDSs which transport low-AOC water without disinfectant residuals, produced from fresh water applying conventional treatment. Full-scale studies were also conducted at the desalination plant and DWDS of KAUST, Saudi Arabia where drinking water is produced from seawater applying RO membrane treatment and then transported with chlorine residual. Furthermore, biological stability was evaluated in a wastewater reuse application in the Netherlands. When low-AOC water was distributed without disinfectant residuals, greater bacterial richness was detected in the networks, however, temporal and spatial variations in the bacterial community were insignificant and a substantial fraction of the microbiome was still shared between the treated and transported water. This shared fraction was lower in the system transporting water with chlorine residual, where the eukaryotic community changed with residence time. The core microbiome was characterized and dominant members varied between the two systems. Biofilm and deposit-associated communities were found to drive tap water microbiology regardless of water source and treatment scheme. Network flushing was found to be a simple method to assess water microbiology. Biological stability was not associated with safety. The biological stability concept needs to be revised and quantified. Further research is needed to understand microbial functions and processes, how water communities affect the human microbiome, and what the “drinking” water microbiome is like in undeveloped countries. / The research presented in this doctoral dissertation was financially supported by and conducted in collaboration with Delft University of Technology (TU Delft) and Evides Waterbedrijf in the Netherlands.
230

In-plant And Distribution System Corrosion Control For Reverse Osmosis, Nanofiltration, And Anion Exchange Process Blends

Jeffery, Samantha 01 January 2013 (has links)
The integration of advanced technologies into existing water treatment facilities (WTFs) can improve and enhance water quality; however, these same modifications or improvements may adversely affect finished water provided to the consumer by public water systems (PWSs) that embrace these advanced technologies. Process modification or improvements may unintentionally impact compliance with the provisions of the United States Environmental Protection Agency’s (USEPA’s) Safe Drinking Water Act (SDWA). This is especially true with respect to corrosion control, since minor changes in water quality can affect metal release. Changes in metal release can have a direct impact on a water purveyor’s compliance with the SDWA’s Lead and Copper Rule (LCR). In 2010, the Town of Jupiter (Town) decommissioned its ageing lime softening (LS) plant and integrated a nanofiltration (NF) plant into their WTF. The removal of the LS process subsequently decreased the pH in the existing reverse osmosis (RO) clearwell, leaving only RO permeate and anion exchange (AX) effluent to blend. The Town believed that the RO-AX blend was corrosive in nature and that blending with NF permeate would alleviate their concern. Consequently, a portion of the NF permeate stream was to be split between the existing RO-AX clearwell and a newly constructed NF primary clearwell. The Town requested that the University of Central Florida (UCF) conduct research evaluating how to mitigate negative impacts that may result from changing water quality, should the Town place its AX into ready-reserve. iv The research presented in this document was focused on the evaluation of corrosion control alternatives for the Town, and was segmented into two major components: 1. The first component of the research studied internal corrosion within the existing RO clearwell and appurtenances of the Town’s WTF, should the Town place the AX process on standby. Research related to WTF in-plant corrosion control focused on blending NF and RO permeate, forming a new intermediate blend, and pH-adjusting the resulting mixture to reduce corrosion in the RO clearwell. 2. The second component was implemented with respect to the Town’s potable water distribution system. The distribution system corrosion control research evaluated various phosphate-based corrosion inhibitors to determine their effectiveness in reducing mild steel, lead and copper release in order to maintain the Town’s continual compliance with the LCR. The primary objective of the in-plant corrosion control research was to determine the appropriate ratio of RO to NF permeate and the pH necessary to reduce corrosion in the RO clearwell. In this research, the Langelier saturation index (LSI) was the corrosion index used to evaluate the stability of RO:NF blends. Results indicated that a pH-adjusted blend consisting of 70% RO and 30% NF permeate at 8.8-8.9 pH units would produce an LSI of +0.1, theoretically protecting the RO clearwell from corrosion. The primary objective of the distribution system corrosion control component of the research was to identify a corrosion control inhibitor that would further reduce lead and v copper metal release observed in the Town’s distribution system to below their respective action limits (ALs) as defined in the LCR. Six alternative inhibitors composed of various orthophosphate and polyphosphate (ortho:poly) ratios were evaluated sequentially using a corrosion control test apparatus. The apparatus was designed to house mild steel, lead and copper coupons used for weight loss analysis, as well as mild steel, lead solder and copper electrodes used for linear polarization analysis. One side of the apparatus, referred to as the “control condition,” was fed potable water that did not contain the corrosion inhibitor, while the other side of the corrosion apparatus, termed the “test condition,” was fed potable water that had been dosed with a corrosion inhibitor. Corrosion rate measurements were taken twice per weekday, and water quality was measured twice per week. Inhibitor evaluations were conducted over a span of 55 to 56 days, varying with each inhibitor. Coupons and electrodes were pre-corroded to simulate existing distribution system conditions. Water flow to the apparatus was controlled with an on/off timer to represent variations in the system and homes. Inhibitor comparisons were made based on their effectiveness at reducing lead and copper release after chemical addition. Based on the results obtained from the assessment of corrosion inhibitors for distribution system corrosion control, it appears that Inhibitors 1 and 3 were more successful in reducing lead corrosion rates, and each of these inhibitors reduced copper corrosion rates. Also, it is recommended that consideration be given to use of a redundant single-loop duplicate test apparatus in lieu of a double rack corrosion control test apparatus in experiments where pre-corrosion phases are vi implemented. This recommendation is offered because statistically, the control versus test double loop may not provide relevance in data analysis. The use of the Wilcoxon signed ranks test comparing the initial pre-corroding phase to the inhibitor effectiveness phase has proven to be a more useful analytical method for corrosion studies.

Page generated in 0.1309 seconds