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  • 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.

Incorporating Environmental Impacts into Multi-Objective Optimization of Water Distribution Systems

HERSTEIN, LESLEY 25 August 2009 (has links)
Municipal water distribution system (WDS) expansion is often focused on increasing system capacity with designs that best meet hydraulic requirements at the least cost. Increasing public awareness regarding global warming and environmental degradation is making environmental impact an important factor in decision-making for municipalities. There is thus a growing need to consider environmental impacts alongside cost and hydraulic requirements in the expansion and design of WDSs. As a result, the multiplicity of environmental impacts to consider in WDS expansion can complicate the decisions faced by water utilities. For example, a water utility may wish to consider environmental policy issues such as greenhouse gas emissions, non-renewable resource use, and releases to land, water, and air in WDS expansion planning. This thesis outlines a multi-objective optimization approach for WDS design and expansion that balances the objectives of capital cost, annual pumping energy use, and environmental impact minimization, while meeting hydraulic constraints. An environmental impact index that aggregates multiple environmental measures was incorporated as an environmental impact objective function in the multi-objective non-dominated sorting genetic algorithm-II (NSGA-II) optimization algorithm. The environmental impact index was developed to reflect stakeholder prioritization of specific environmental policy issues. The evaluation of the environmental impact index and its application to the WDS expansion problem was demonstrated with a water transmission system example. The environmental impact index and multi-objective non-dominated sorting genetic algorithm-II (NSGA-II) optimization algorithm were applied to the “Anytown” network expansion problem. Preliminary results suggest that solutions obtained with the triple-objective capital cost/energy/EI index optimization minimize a number of environmental impact measures while producing results that are comparable in pumping energy use and, in some instances, slightly higher in capital cost when compared to solutions obtained with a double cost/energy optimization in which environmental impact was not considered. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-08-25 16:08:33.636

Evaluating the Impact of Climate Change Mitigation Strategies on Water Distribution System Design and Optimization

MacLeod, Stephanie Patricia 27 August 2010 (has links)
In response to growing environmental concerns, policy makers in Canada have been developing climate change mitigation strategies that will enable Canada to meet medium and long-term greenhouse gas (GHG) emission reduction targets. The water industry is energy- and carbon-intensive, thus the magnitude and long-term uncertainty of proposed carbon mitigation policies could have implications for water distribution system capital planning decisions that are made today. The intent of this thesis was to examine the implications of discount rate and carbon price uncertainty on cost, energy use and GHG emissions in the design/optimization of the Amherstview water distribution system in Loyalist Township, Ontario, Canada. A non-dominated sorting genetic algorithm is coupled with the hydraulic solver EPANET2 in a single-objective optimization approach to identify network expansion designs that minimize total cost as the sum of: i) capital cost of installing new and parallel pipes and of cleaning and lining existing pipes; ii) operation cost of electricity for pumping water; and iii) carbon cost levied on electricity used for pumping water. The Amherstview system was optimized for a range of discount rates and carbon prices reflective of possible climate change mitigation strategies in Canada over the next 50 years. The problem formulation framework was developed according to a “real-world” municipal approach to water distribution system design and expansion. Decision variables such as pipe sizes are restricted to “real-world” commercially-available pipe diameters and parameter values are chosen according to engineering judgment and best-estimates. Parameter uncertainty is characterized by sensitivity analysis rather than the more computationally-demanding and data-intensive Monte Carlo simulation method. The impact of pipe material selection on energy use and GHG emissions was investigated for polyvinyl chloride and cement-mortar lined ductile iron pipes. Results from this first-ever study indicate that the discount rate and carbon prices investigated had no significant influence on energy use and GHG emissions in the Amherstview system. Pipe material selection was also found to minimally affect the amount of GHG emitted in the Amherstview system. / Thesis (Master, Civil Engineering) -- Queen's University, 2010-08-26 15:01:27.174

Risk Analysis and Adaptive Response Planning for Water Distribution Systems Contamination Emergency Management

Rasekh, Amin 2012 August 1900 (has links)
Drinking water distribution systems (WDSs) hold a particularly critical and strategic position in preserving public health and industrial growth. Despite the ubiquity of this infrastructure, its importance for public health, and increased risk of terrorism, several aspects of emergency management for WDSs remain at an undeveloped stage. A set of methods is developed to analyze the risk and consequences of WDS contamination events and develop emergency response support tools. Monte Carlo and optimization schemes are developed to evaluate contamination risk of WDSs for generation of critical contamination scenarios. A multicriteria optimization approach is proposed that treats likelihood and consequences as independent risk measures to find an ensemble of uniformly-distributed critical scenarios. This approach provides insight into system risk and potential mitigation options not available under maximum risk or maximum consequences analyses. Static multiobjective simulation-optimization schemes are developed for generation of optimal response mechanisms for contamination incidents with twoconflicting objectives of minimization of health consequences and impacts on non-consumptive water uses. Performance of contaminant flushing and containment are investigated. Pressure-driven hydraulic analysis is performed to simulate the complicated system hydraulics under pressure-deficit conditions. Performance of a novel preventive response action ? injection of food-grade dye directly into drinking water ? for mitigation of health impacts as a contamination threat unfolds is explored. The emergency response is formulated as a multiobjective optimization problem for the minimization of risks to life with minimum false warning and cost. A multiobjective optimization scheme is used for the management of contamination events for diverse contaminant agents without interruption of firefighting. A dynamic modeling scheme is developed that accounts for the time-varying behavior of the system during an emergency. Effects of actions taken by the managers and consumers as well as the changing perceived contaminant source attributes are included in the simulation model to provide a realistic picture of the dynamic environment. A dynamic optimization scheme is coupled with the simulation model to identify and update the optimal response recommendations during the emergency. Machine learning approaches are employed for real-time characterization of contaminant sources and identification of effective response strategies for a timely and effective response to contamination incidents and threats. In contrast to traditional approaches that perform whole analysis after a contamination event occurs, proposed machine learning methods gain system knowledge in advance and use this extracted information to identify contamination attributes after an incident occurs.


SUBRAMANIAM, PRATHIBA 03 December 2001 (has links)
No description available.


COPELAND, RACHEL C. January 2005 (has links)
No description available.

Disinfection By-Product Formation in the Water Distribution System of Morehead, Kentucky

Sekhar, Megan W. 11 October 2001 (has links)
No description available.

An Optimal Pipe Replacement Scheduling Model for Water Distribution Systems

Park, Suwan 16 February 2000 (has links)
While the idea of critical break rate of water distribution pipeline (defined as the break rate after which it is no longer economical to continuously repair) has been accepted in the literature and among the practicing engineers, the formula to obtain the critical break rate has remained elusive. In this dissertation, an equation for identifying the threshold break rate of a pipe is developed. The threshold break rate equation gives a rule of thumb for pipe replacement decision. Input parameters to obtain the threshold break rate of a pipe are repair and replacement costs, interest rate, and the length of the pipe. In addition, a methodology that enables the use of threshold break rate with the failure intensity and hazard functions is developed. The methodology is drawn by considering the relationships of the definitions of the threshold break rate with intensity and hazard functions in the context of a repairable system's failure process modeling. As a result, the newly developed threshold break rate equation can be coupled with any appropriate intensity and hazard function to obtain economically optimal replacement time of a pipe. Also, practical usage of the threshold break rate is demonstrated with a number of numerical examples. Design aids in the form of charts and tables are provided. The threshold break rate can be easily obtained either graphically or with the aid of the tables. The methodology that links the threshold break rate and failure rate (intensity and hazard) functions is extended to accommodate stress multiplying environmental factors in the form of the proportional intensity and hazards model. The two models consist of an age dependent failure rate function and a covariate structure. They are applied to a case study area pipe system to obtain optimal replacement times for individual pipes in the system. As a result, important hazard characteristics of water distribution pipes are drawn, and implications on the optimal replacement analysis are discussed. A pipe break prediction model is also developed in this research. The model spans the space between the linear and exponential break trends. The model is applied to the case study area pipe system with various cost options. The results from this analysis are discussed in terms of practical implementation of the replacement strategies. / Ph. D.

A futures approach to water distribution and sewer network (re)design

Atkinson, Stuart January 2013 (has links)
When designing urban water systems (i.e. water distribution and sewer systems) it is imperative that uncertainty is taken into consideration. However, this is a challenging problem due to the inherent uncertainty associated with both system loading requirements and the potential for physical components failure. It is therefore desirable to improve the reliability of each system in order to account for these uncertainties. Although it is possible to directly evaluate the reliability of a water distribution systems (WDS) (using reliability measures), the calculation processes involved are computationally intensive and therefore unsuitable for some state-of-the-art, iterative design approaches (such as optimisation). Consequently, interest has recently grown in the use of reliability indicators, which are simpler and faster to evaluate than conventional direct reliability methods. In this thesis, a novel measure (the RUF) is developed to quantify reliability in urban water systems with a view to enhance their robustness under a range of future scenarios (Policy Reform, Market Forces, Fortress World and New-Sustainability Paradigm). The considered four future scenarios were synthesized in the EPSRC supported multidisciplinary 4 year project: Urban Futures. Each investigated urban future scenario is characterised by a distinct household water demand and local demand distribution (emerging due to different urban forms evolving in future scenarios). In order to assess the impact of urban futures, RUF has been incorporated into Urban Water System (UWS) dynamic simulations for both WDSs and Foul Sewer Systems (FSSs) using open source codes of EPANET and SWMM. Additionally, in order to overcome extensive computational effort, resulting from the use of traditional reliability measures, a new holistic reliability indicator, the hydraulic power entropy (IHPE) has been developed and compared to existing reliability indicators. Additionally, the relationship between the new reliability indicator and the above mentioned RUF reliability measure is investigated. Results suggest that the magnitude of the IHPE in network solutions provides a holistic indication of the hydraulic performance and reliability for a WDS. However, the performance of optimal solutions under some Urban Futures indicates that additional design interventions are required in order to achieve desired future operation. This thesis also proposes a new holistic foul sewer system (FSS) reliability indicator (the IFSR). The IFSR represents sewer performance as a function of excess pipe capacity (in terms of available increase and also decrease in inflow). The indicator has been tested for two case studies (i.e. different sewer network layouts). Results suggest that the magnitude of IFSR has positive correlations with a number of identified key performance indicators (i.e. relating to capacity, velocity, blockages). Finally, an Integrated Design Approach (IDA) has been developed in order to assess the implications of applying design interventions on both a WDS and downstream FSS. The approach holistically considers present and future operation of each interconnected system. The approach was subsequently demonstrated using two proposed design interventions. Results suggest that, for the considered design interventions, there is trade-off between the simultaneous improvement of both WDS and FSS operation and reliability.

Interdependent infrastructures and multi-mode attacks and failures: improving the security of urban water systems and fire response

Bristow, Elizabeth Catherine 15 May 2009 (has links)
This dissertation examines the interdependence between urban water distribution systems and urban fire response. The focus on interdependent critical infrastructures is driven by concern for security of water systems and the effects on related infrastructures if water distribution systems are damaged by terrorist attack or natural disaster. A model of interdependent infrastructures (principally water distribution systems and fire response) is developed called the Model of Urban Fire Spread (MUFS). The model includes the capacity to simulate firefighting water demands in a community water system hydraulic model, building-to-building urban fire spread, and suppression activities. MUFS is an improvement over previous similar models because it allows simulation of urban fires at the level of individual buildings and it permits simulation of interdependent infrastructures working in concert. MUFS is used to simulate a series of multi-mode attacks and failures (MMAFs) – events which disable the water distribution system and simultaneously ignite an urban fire. The consequences of MMAF scenarios are analyzed to determine the most serious modes of infrastructure failure and urban fire ignition. Various methods to determine worst-case configurations of urban fire ignition points are also examined. These MMAF scenarios are used to inform the design of potential mitigation measures to decrease the consequences of the urban fire. The effectiveness of mitigation methods is determined using the MUFS simulation tool. Novel metrics are developed to quantify the effectiveness of the mitigation methods from the time-series development of their consequences. A cost-benefit analysis of the various mitigation measures is conducted to provide additional insight into the methods’ effectiveness and better inform the decision-making process of selecting mitigation methods. Planned future work includes further refinement of the representation of fire propagation and suppression in MUFS and investigation of historical MMAF events to validate simulation predictions. Future efforts will continue development of appropriate optimization methods for determining worst-case MMAF scenarios. This work should be of interest to water utility managers and emergency planners, who can adapt the methodology to analyze their communities’ vulnerability to MMAFs and design mitigation techniques to meet their unique needs, as well as to researchers interested in infrastructure modeling and disaster simulation.

Characterization of heterotrophic plate count (HPC) bacteria from biofilm and bulk water samples from the Potchefstroom drinking water distribution system / by S. Walter

Walter, Sunette January 2009 (has links)
The presence of heterotrophic plate count (HPC) bacteria in drinking water distribution systems is usually not considered harmful to the general consumer. However, precautions must be taken regarding the immunocompromised. All water supply authorities in South Africa are lawfully required to provide consumers with high-quality drinking water that complies with South African-and international standards. This study mainly focused on the isolation, identification and characterization of HPC and other bacteria from biofilm-and bulk water samples from two sampling points located within the Potchefstroom drinking water distribution system. Based on five main objectives set out in this study, results indicated that the bulk water at the J.S. van der Merwe building was of ideal quality fit for lifetime consumption. Application of enrichment-and selective media allowed for the isolation of 12 different bacterial morphotypes. These were identified by way of biochemical-and molecular methods as Bacillus cereus, Bacillus subtilis, Brevundimonas spp., Clostridiaceae, Corynebacterium renale, Flavobacteriaceae, Kytococcus sedentarius, Leuconostoc lactic, Lysinibacillus sphaericus, Pseudomonas spp., Staphylococcus aureus and Staphylococcus capitis. The greatest diversity of bacteria was detected early autumn 2008, while the lowest diversity occurred during mid-winter 2007. Bacillus cereus, Kytococcus sedentarius and Staphylococcus capitis displayed potential pathogenic properties on blood agar. Kytococcus sedentarius could be classified as potentially the most pathogenic among the isolates. All isolates displayed multiple-resistant patterns towards tested antibiotics. Corynebacterium renale and Staphylococcus aureus were least resistant bacterial species and Lysinibacillus sphaericus the most resistant. All isolates were susceptible to ciprofloxacin (CIP) and streptomycin (S), but most were resistant to erythromycin (E). Transmission electron microscopy (TEM) allowed for detailed examination of Brevundimonas spp., Pseudomonas spp. and Staphylococcus spp. The capability of Brevundimonas spp. to produce slime and store nutrients within inclusion bodies, suggests the ability of this bacterium to form biofilm and persist in the drinking water for prolonged periods. Despite the inhibitory or toxic effect of copper against bacterial growth, scanning electron microscopy (SEM) revealed the presence of biofilms as well as diatoms on red-copper coupons. Biofilm activity was also observed on reverse-osmosis (RO) filters. Since corrosion was evident on red-copper coupons, it is recommended that prospective studies also look into the significance of microbial induced corrosion (MIC) within the Potchefstroom drinking water distribution system. Other prospects include determining minimum inhibitory concentrations of isolates against antibiotics and the application of culture independent methods such as SSCP and DGGE to investigate biofilm development. The use of diatoms as an index of the drinking water quality is also suggested. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2010.

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