Water cycle management for building water-wise cities

Abstract

Water is a chemical substance with a simple but stable molecular structure of H 2 O. It cannot be generated or eliminated under normal conditions, so the total mass of water in the whole world is constant. Water itself is transparent, tasteless, odorless, and nearly colorless, but can dissolve various inorganic and organic solutes, and carry fine particulate solids as it flows. All these foreign substances the water carries are called 'impurities' which can enter the water mass and conversely be removed through various natural or artificial actions. Water is essential to human and all living organisms, but any consumption and utilization of water cannot result in any true loss of the water mass. This means that after water use, the water molecules are still there and the only alteration is in their quality, location of existence, and existing state (liquid, gaseous or even solid forms). However, the usability of water may not merely depend on its quantity, but more importantly its quality. Contaminated water cannot be directly supplied for most purposes of water use. In this sense, the problem of water shortage we

Safe water reuse through a quasi-natural water cycle

“…water bodies) over the world, such as rivers, lakes, and groundwater aquifers, not to mention the vast oceans which are viewed as the original 'source' where a water circulation starts by evaporation, and the ultimate 'sink' where a water circulation ends; another is to secure the water quality in each waterbody through a series of physical, physicochemical, chemical, and biological actions that naturally occur in the whole water cycle. Since the hydrological cycle is solely driven by solar energy and gravitational energy, and can spontaneously maintain a dynamic equilibrium condition without any unnatural interference, it is virtually a thermodynamically sound system (Wang & Luo 2021).…”