Research On Reliability Of Water Quality And Contamination Source Determination Of Water Distribution Networks

Water distribution networks are important urban infrastructures, whose safe andreliable operation is the most important guarantee for people’s normal production andliving. In the research field of the security of water distribution networks, researchersmostly focus on the hydraulic safety performance of networks, but always ignore thewater quality safety performance. Therefore, this paper studied on three aspects,which including the reliability assessment of water quality, optimizing water qualitymonitoring stations and contamination source determination. The outcome of thisstudy could provide a theoretical basis and decision support for the management andscheduling under different conditions.Firstly, the main purpose of this paper is to explore reliability assessment ofwater quality in water distribution networks using the path entropy method. The waterquality entropy was interpreted and defined by means of the concept of probabilityspace. This paper derived the calculation formula of water quality entropy, and on thisbasis, the calculation model of water quality entropy was built. Meanwhile, theconcepts of maximum water quality entropy and relative water quality entropy wereraised, and water quality reliability in single-source networks was characterized by thevalue of relative water quality entropy. The analysis of a network of developing areain a city shows that this assessment method can be used to search the area with lowervalue of water quality reliability in water distribution networks according to thedistribution map of equal water quality reliability. The method can also providescientific guidance for the special reconstruction and expansion of networks.Secondly, a new method of optimal location of water quality monitoring stationshas been proposed. The concept of upstream nodes set has been defined. Theupstream nodes set of each node could be found out using this concept. And then, theupstream nodes should be selected in order to make sure that the abnormality of waterquality could be found by monitoring stations in several hours after pollution accidenthappened. Using the concept of water quality sensitivity defined in this paper, thesensitivity of all nodes could be solved. Meanwhile, in each extent of water works, allnodes should be compared and selected according to the water quality sensitivityvalues of nodes in descending order. During the process of comparing and selecting, several factors, such as the monitoring range, installation conditions, the difficulties ofconstruction, user important level, and so on, should be taken into consideration. Atlast, under the condition of the combination of theoretical calculation and actualsituation, a set of optimal monitoring station scheme could be determined.Finally, based on the theory of the distribution path, a relatively perfect modelfor contamination source determination has been proposed studied with inertcontaminants as subject. When monitoring stations measured the abnormal value, thepollution accident simulated for each node within the monitoring range. Then, thecontamination source could be found by error analysis between simulation results andactual monitoring data. The pollution accident were simulated again in the existedsimulation results using the next moment abnormal water quality data afterwards. Thenew results in this process could be much closer to the monitoring data at second time.After the locating at several moments, the location, occurrence time, and theconcentration of the unique contamination source could be determined at last.