Doctor of Philosophy, Case Western Reserve University, 2020, Civil Engineering

Water Distribution Systems (WDSs) are the most essential civil infrastructure systems for the functioning of communities. Economic prosperity and social wellbeing of modern society depend on reliable, robust, and resilient WDSs. Unfortunately, a majority of water pipelines in the United States (U.S.) are in service beyond their intended design life and have experienced a high failure rate. Aged metallic pipelines are susceptible to failure due to corrosion deterioration, traffic loading, excessive water pressure, seismic loading, and other factors. These failures result in enormous direct and indirect economic and societal consequences. Moreover, water pipe failures often lead to cascading consequences to other interconnecting infrastructure, especially road networks. In the face of these frequent failures, water utilities are struggling to maintain their assets with limited budget and resource constraints. There is a clear need to develop a comprehensive framework to assess and mitigate the risk posed by combined external loading (e.g., water pressure, traffic loading, earthquakes) and corrosion deterioration to WDSs. This research presents a risk-based asset management decision-support framework for WDSs subjected to combined corrosion and external loading, considering both component-level and system-level risk. A critical literature review of existing literature on various aspects of asset management is performed to establish the knowledge gap between current practice and theory in WDS research. Various fragility models of pipelines and systems are developed considering the effect of corrosion deterioration. Uncertainties involved in fragility and restoration models are accounted for using the probabilistic approaches. The seismic restoration process is modeled considering the repair activities overtimes. Next, a framework is proposed that incorporates topological and hydraulic reliability model, seismic functionality and resilience model, scenario-based seismi (open full item for complete abstract)

Committee: Yue Li Dr. (Advisor); Wojbor Woyczynski Dr. (Committee Member); Xiong Yu Dr. (Committee Member); Christian Carloni Dr. (Committee Member) Subjects: Civil Engineering

MS, University of Cincinnati, 2001, Engineering : Environmental Engineering

A framework is developed to quantify the susceptibility of drinking water distribution systems to intrusion events. The framework integrates infrastructure information, hydraulic modeling, and demographic data. These elements are managed within a geographic information system (GIS). Using criteria that reflect system pressure, hydraulic intrusion pathways, and contaminant sources, the framework identifies locations within the distribution system susceptible to intrusion events. Locations found to be susceptible to intrusions are prioritized for attention based on proximity to sensitive populations, such as young children and the elderly. The proposed method is demonstrated with a case study based on a real distribution system. The study area encompasses approximately 38 square miles, includes three service areas, contains over 280 miles of water main serving 18,900 connections with a total average demand of five to six million gallons per day. Susceptibility conditions exist at some locations throughout the system; however, only rarely do all three conditions coincide. Hence very few locations were deemed susceptible to intrusion events. The framework may support capital improvement programs, operational decisions, and distribution system sampling designs. Methods such as this have been suggested as part of a larger distribution system management approach to improve water quality and at the same time reduce regulatory sampling requirements.

Committee: Steven Buchberger (Advisor) Subjects:

MS, University of Cincinnati, 2001, Engineering : Environmental Engineering

The effect of the distribution system on water quality seems complex. Water demands and average residence times change continually, and chlorine residuals depend on these changing residence times as well as changes in temperature, pH, and organic matter characteristics caused by distribution system hydraulic dynamics. Furthermore, these changing physical/chemical conditions inherently affect the formation of regulated disinfection by-products (DBPs). The research focuses on a water distribution system in eastern Kentucky, which is fed by a 5 MGD conventional treatment plant. The field study was conducted in two phases. A 24-hour hydraulic field sampling event was performed to provide basic data for characterizing the system hydraulics and for understanding the kinetics of chlorine decay and DBP formation. A 48-hour water quality sampling event was conducted using the utility's four regulatory sampling locations, augmented by 15 locations designed to sample representative water from storage tanks, dead-ends, and different pipe materials and ages.

Committee: Dr. James Uber (Advisor) Subjects: Engineering, Environmental

MS, University of Cincinnati, 2012, Engineering and Applied Science: Environmental Engineering

Common problems in drinking water distribution systems, such as pipe breakages and negative pressure events, can lead to the instant contamination of the system from sewage or groundwater sources. Due to the continued use of these distribution systems, potentially, very dangerous waterborne diseases can spread throughout entire systems very quickly and pose a major concern to public health. Considering this condition, drinking water distribution systems are still fragile despite their designed closed system structure. EPANET is a widely used software that contains the ability to run hydraulic and water quality simulations on a drinking water distribution system. However, it is difficult to use in order to analyze complex intrusion events and various intrusion scenarios simultaneously in full-scale distribution systems. This creates the need for a simplified, yet efficient way of analyzing these complex systems. The linear superposition algorithm (LSA) is an algorithm that is able to analyze these complex systems by being able to run component water quality simulations based on an existing EPANET Results Database. This database contains the desirable water quality concentrations for different nodes during a single time period. This paper looks to use the LSA as an extension of the EPANET Results Database API library to verify the validity and efficiency of the whole framework being analyzed. Three case studies, two of which are combined with the Monte Carlo method, are examined using the LSA. Furthermore, the methodology demonstrated in this thesis can be included in a comprehensive risk assessment framework in order to strengthen water quality simulation and management of distribution systems.

Committee: James Uber PhD (Committee Chair); Robert Janke MS (Committee Member); Dominic Boccelli PhD (Committee Member) Subjects: Environmental Engineering

MS, University of Cincinnati, 2008, Engineering : Environmental Engineering

Residual chlorines are provided in water distribution systems to maintain the inactivation of pathogens intruded into network. The effectiveness of chlorine residuals on pathogen removal can be determined using system vulnerability assessment. The effectiveness of chlorination was determined separately and it was determined as higher than that of the distribution and dilution for two case networks studied.CT (Chlorine Residual Concentration x Contact Time) value which is used as an important criterion to assess the inactivation of pathogens, is complicated to be determined for distribution networks due to varying residence times and chlorine concentrations. The relation of CT value with the removal ratio of pathogens was used to estimate CT value for distribution networks. The results of case studies indicate that CT value determined for a distribution network does not only depend on concentration and contact time of chlorine residuals but also temperature, pH and intrusion location and duration.

Committee: James Uber (Committee Chair); Dominic Boccelli (Committee Member); Feng Shang (Committee Member) Subjects: Environmental Engineering

MS, University of Cincinnati, 2005, Engineering : Environmental Engineering

Previous work has shown that arsenic does accumulate in drinking water distribution system (DWDS) solids when arsenic is present in the water. The release of arsenic back into the water through particulate transport and/or chemical release (e.g. desorption, dissolution) could result in elevated arsenic levels at the consumers' tap. The primary objective of this work was to examine the impact of pH and orthophosphate (used for corrosion control) on the chemical release (i.e. desorption) of arsenic from nine DWDS solids collected from four actual utilities in the Midwest. Arsenic release comparisons were based on the examination of arsenic and other water quality parameters in leach water after contact with the solids over the course of 168 hours. Results showed that arsenic did release from solids and suggested that arsenic release was a result of desorption rather than dissolution. Arsenic release generally increased with increasing initial arsenic concentration in the solid and increasing pH levels (in the test range of 7 to 9). Finally, the presence of orthophosphate (3 and 5 mg PO 4 /L) increased arsenic release at all pH values examined. Based on the study results, utilities with measurable levels of arsenic present in their water should be aware that some water quality changes can cause arsenic release in the DWDS potentially resulting in elevated levels at the consumer's tap.

Committee: Dr. Dionysios Dionysiou (Advisor) Subjects: Engineering, Environmental

MS, University of Cincinnati, 2003, Engineering : Environmental Engineering

Leakage in water distribution pipes is a major problem faced by the water industry. Water utilities often employ traditional audit methods to estimate water lost as leakage. Many hydraulic models have also been developed in the recent past to estimate leakage rates and locate leaks. However, water audits give an approximate estimate of the leakage rates and the mathematical models can be applied under certain hydraulic conditions only. In this thesis, a new method is presented for detecting the magnitude of leaks in residential service zones of a drinking water distribution system. It is assumed that continuous measurements of flow rates through the main supply line into a residential service zone are available during periods of low use. The procedure involves computing the sample mean and variance from the set of measured flow rates as these flows are truncated progressively from below. Trajectories of the sample statistics and their derivatives are plotted versus the level of data truncation. In the presence of leaks, these trajectories diverge from their expected theoretical path when plotted on a standardized graph derived from a mixed truncated normal distribution. The point of departure on the standardized graph indicates where the truncation threshold matches the maximum rate of network leakage. A performance limit for the proposed method is derived to account for spatial constraints reflecting network size and time constraints arising from interval averaging. A simple example is presented first where the leakage is assumed to be of constant magnitude. The leak analysis is then extended to a more complicated case where pressure fluctuations in the distribution system add a statistical noise to the flow measurements. Results show that the method developed in this thesis estimates leakage rates quite accurately even in the presence of statistical noise. The method can be used to estimate leakage rates in branching mainlines or residential District Metering Area (open full item for complete abstract)

Committee: Dr. Steven G. Buchberger (Advisor) Subjects:

MS, University of Cincinnati, 2001, Engineering : Environmental Engineering

Disinfectant residual maintenance has been always a concern to the utilities. Booster disinfection is a strategy that is being applied to add disinfectants at strategic locations throughout a water distribution system. A designer needs information about the network for the location and operation of booster stations. This thesis describes the development and investigation of a method that would be able to estimate and identify, with some degree of accuracy, minimum location of booster stations that are practicable for real distribution networks. The model formulation is related to a general facility location problem, which uses a branch and bound solution procedure. The design objectives considered are (1) minimize the number of booster stations and (2) maximize the uniformity of the residual demand in the network. The random inputs to the model are set of potential booster locations and desired residual demand for a given system. The design method is applied to a real distribution network. Results illustrationg the tradeoffs between the objectives suggest that to maintain a higher and uniform residual demand in the network, more number of booster stations are required. For varied input set of potential booster stations, different solution sets of optimal booster locations can achieve the same residual demand. The designer has to consider the extent of residual coverage that each booster station attains and the amount of overlapping influences that takes place between the operation of the booster stations. These tradeoffs are an important factor in the network design unless the cost is of limited concern.

Committee: Dr. James G. Uber (Advisor) Subjects: Engineering, Environmental