Optimal design of water reuse networks in cities through decision support tool development and testing

Water scarcity and droughts are an increasing issue in many parts of the world. In the context of urban water systems, the transition to circularity may imply wastewater treatment and reuse. Planning and assessment of water reuse projects require decision-makers evaluating the cost and benefits of alternative scenarios. Manual or semi-automatic approaches are still common practice for planning both drinking and reclaimed water distribution networks. This work illustrates a decision support tool that, based on open data sources and graph theory coupled to greedy optimization algorithms, is able to automatically compute the optimal reclaimed water network for a given scenario. The tool provides not only the maximum amount of served reclaimed water per unit of invested cost, but also the length and diameters of the pipes required, the location and size of storage tanks, the population served, and the construction costs, i.e., everything under the same architecture. The usefulness of the tool is illustrated in two different but complementary cities in terms of size, density, and topography. The construction cost of the optimal water reclaimed network for a city of approximately 100,000 inhabitants is estimated to be in the range of euro0.17-0.22/m(3) (for a payback period of 30 years).

Automated summary

Water scarcity and droughts are becoming more serious issues globally. This study presents a decision support tool that can automatically compute the optimal reclaimed water network for a given scenario, utilizing open data sources, graph theory, and greedy optimization algorithms. The tool provides information on reclaimed water quantity, pipe lengths and diameters, storage tank locations and sizes, population served, and construction costs. The tool's usefulness is demonstrated in two different cities. The estimated construction cost of the optimal water reclaimed network for a city with approximately 100,000 inhabitants is in the range of euro0.17-0.22/m(3) (with a payback period of 30 years).