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Fragiadakis M.,University of Cyprus | Christodoulou S.E.,University of Cyprus | Christodoulou S.E.,Nireas International Water Research Center
Earthquake Engineering and Structural Dynamics | Year: 2014

We present a framework for the seismic risk assessment of water supply networks, operating in either normal or abnormal conditions. We propose a methodology for assessing the reliability of water pipe networks combining data of past non-seismic damage and the vulnerability of the network components against seismic loading. Historical data are obtained using records of damages that occur on a daily basis throughout the network and are processed to produce'survival curves', depicting their estimated survival rate over time. The fragility of the network components is assessed using the approach suggested in the American Lifelines Alliance guidelines. The network reliability is assessed using graph theory, whereas the system network reliability is calculated using Monte Carlo simulation. The methodology proposed is demonstrated both on a simple, small-scale, network and also on a real-scale district metered area from the water network of the city of Limassol, Cyprus. The proposed approach allows the estimation of the probability that the network fails to provide the desired level of service and allows the prioritization of retrofit interventions and of capacity-upgrade actions pertaining to existing water pipe networks. © 2013 John Wiley & Sons, Ltd. Source


Vasquez M.I.,Cyprus University of Technology | Vasquez M.I.,Nireas International Water Research Center | Michael I.,University of Cyprus | Kummerer K.,Luneburg University | Fatta-Kassinos D.,University of Cyprus
Handbook of Environmental Chemistry | Year: 2016

Water deprivation with regard to quantity and quality is one of the most important environmental problems of the century. The increasing demand of water resources puts pressure on the utilization of alternative sources such as treated wastewater. In the context of "reduce, reuse, and recycle," the inclusion of treated wastewater in the water cycle seems a promising practice for water management. The lack of general acceptance of stakeholders and public, however, still hinders the widespread application of wastewater reuse. A reason for this is, among others, the presence of contaminants of emerging concern in treated wastewater. This has led to an increased concern about direct and indirect effects to the environment and possible implications to human health. The development and application of bioassays able to identify and quantify the biological potency of treated wastewater is an ongoing research effort, especially when taking into consideration that a plethora of contaminants exist and interact in this complex matrix. This chapter summarizes available literature regarding the sensitivity of currently applied bioassays for assessing biological effects of treated wastewater and their correlation with chemical analysis. The focus is on pharmaceuticals since they represent one of the major groups of contaminants of emerging concern with many unanswered questions currently in place. © 2016 Springer International Publishing Switzerland. Source


Fragiadakis M.,University of Cyprus | Fragiadakis M.,Nireas International Water Research Center | Christodoulou S.E.,University of Cyprus | Christodoulou S.E.,Nireas International Water Research Center | Vamvatsikos D.,National Technical University of Athens
Water Resources Management | Year: 2013

Presented herein is a methodology for the seismic assessment of the reliability of urban water distribution networks (UWDN) based on general seismic assessment standards, as per the American Lifelines Alliance (ALA) guidelines, and localized historical records of critical risk-of-failure metrics pertaining to the specific UWDN under assessment. The proposed methodology is applicable to UWDN under both normal or abnormal operating conditions (such as intermittent water supply), and the assessment of reliability incorporates data of past non-seismic damage, the vulnerabilities of the network components against seismic loading, and the topology of a UWDN. Historical data obtained using records of pipe burst incidents are processed to produce clustered 'survival curves', depicting the pipes' estimated survival rate over time. The survival curves are then used to localize the generalized fragility values of the network components (primarily pipes), as assessed using the approach suggested by the ALA guidelines. The network reliability is subsequently assessed using Graph Theory (Djikstra's shortest path algorithm), while the system reliability is calculated using Monte Carlo simulation. The methodology proposed is demonstrated on a simple small-scale network and on a real-scale district metered area (DMA). The proposed approach allows the estimation of the probability that a network fails to provide the desired level of service and allows for the prioritization of retrofit interventions and of capacity-upgrade actions pertaining to existing water pipe networks. © 2013 Springer Science+Business Media Dordrecht. Source


Christodoulou S.E.,University of Cyprus | Christodoulou S.E.,Nireas International Water Research Center | Gagatsis A.,Nireas International Water Research Center | Xanthos S.,Nireas International Water Research Center | And 4 more authors.
Water Resources Management | Year: 2013

The work presented herein addresses the problem of sensor placement optimization in urban water distribution networks by use of an entropy-based approach, for the purpose of efficient and economically viable waterloss incident detection. The proposed method is applicable to longitudinal rather than spatial sensing, thus to devices such as acoustic, pressure, or flow sensors acting on pipe segments. The method utilizes the maximality, subadditivity and equivocation properties of entropy, coupled with a statistical definition of the probability of sensing within a pipe segment, to assign an entropy metric to each pipe segment and subsequently optimize the location of sensors in the network based on maximizing the total entropy in the network. The method proposed is a greedy-search heuristic. © 2013 Springer Science+Business Media Dordrecht. Source

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