A Graph-Theory Based PRV Placement Algorithm for Reducing Water Age in Water Distribution Systems

Water age is the time taking the water to travel through a distribution system and reach the consumer. Generally, there is a trade-off between water pressure and water age in a water distribution system - higher pressure results in higher flow velocity, which often means shorter travelling time for the water, while lower pressure leads to slower flow and thus higher water age. Low pressure is a desired objective in a distribution system, as it reduces the physical stress on its components and minimizes water losses in an event of a leak. Low water age is a desired objective as well, as increased age is regarded as low water quality. Therefore, the two objectives compete with one another. The problem of trying to minimize both water pressure and age is a common problem in water distribution system design and management. This paper introduces an algorithm for pressure reducing valve (PRV) placement for reducing water age in water distribution systems. The algorithm is based on graph-theory elements and uses EPANET 2.2 for simulation and analysis. The method is demonstrated on a small-scale example, and the results present relatively significant improvements in respect to water age.