The potential of alternative water sources for potable water savings in Ukraine's residential areas

Universal access to safe drinking water is not only a fundamental need but also a basic human right. Water reuse and rainwater harvesting systems provide essential technical alternatives for water supply management. There are several alternative water sources available for reuse after some needed treatment: rainwater, stormwater, greywater, drainage water etc. The integration of on-site non-potable water reuse enhances the environmental goals of a green building by lowering the consumption of potable water and decreasing the volume of storm-water and wastewater that must be sent to the City's Wastewater Treatment Plants for treatment. The purpose of the article is to analyze two approaches for partially replacing tap water (rainwater harvesting and treated greywater reuse), to compare the constructive characteristics of these systems and calculate annual volume the potential water savings in Ukraine's residential areas using each option. Both methods offer sustainable solutions to alleviate water scarcity but differ significantly in construction, application, and operational mechanisms. For a comparative analysis of the two indicated alternative sources, are present the constructive features of water supply in the context of rainwater collection and use, and greywater. The volume of greywater generated in low-rise residential areas and rainwater that can be harvested from roofs was counted using Ukranian normative documents. The result shows at a building density of 0.4, the greywater volume is 1.45 times greater than that of rainwater; at a density of 0.54, it is 1.49 times greater under Ukraine's maximum annual precipitation of 750 mm. With comprehensive water recycling systems, it is possible to reduce freshwater demand by approximately 30% through greywater reuse and by around 10% with rainwater harvesting. These savings offer both economic and environmental benefits, making water recycling especially advantageous for water-scarce regions seeking to mitigate the impacts of climate change.