Abstract
Decentralized water systems are perceived as solutions that not only save water, but also as a way to partially or completely become independent from centralized suppliers. Taking this into account, an analysis of the effectiveness of rainwater harvesting systems (RWHS) for toilet flushing in existing academic facilities located in Poland and in Slovakia was carried out. The tests took into account the different volumes of storage tanks collecting rainwater. On the basis of two financial ratios, namely Net Present Value and Discounted Payback Period, the profitability of these systems was also assessed. The research was extended by the sensitivity analysis, which allowed determination of the impact of changes in individual cost components on the financial effectiveness of the investments considered. The results obtained clearly showed that the implementation of RWHS in the dormitory in Rzeszów was unprofitable for all tank capacities tested, and the payback period significantly exceeded the period of 30 years accepted for the analysis. Completely different results were obtained for RWHS in a dormitory located in the city of Košice, for which the financial ratios NPV (Net Present Value) and DPP (Discounted Payback Period) were very favorable. It was also confirmed by the results of the sensitivity analysis. The use of rainwater for toilet flushing caused that it was possible to achieve water savings of an average of 29% and 18%, respectively, for facilities located in Slovakia and Poland. The results of the research have a practical aspect and can provide an indication for potential investors and managers of academic facilities, similar to those analyzed in the article. Taking into account that in many countries water and sewage rates are significantly higher than in Poland and Slovakia, the cost-effectiveness of using the analyzed installation options in these countries could be even higher.
Highlights
Sustainable exploitation of natural resources and their protection is of key importance for smart development [1,2]
The use of rainwater for toilet flushing caused that it was possible to achieve water savings of an average of 29% and 18%, respectively, for facilities located in Slovakia and Poland
Student dormitories located in Poland and Slovakia were selected for the study
Summary
Sustainable exploitation of natural resources and their protection is of key importance for smart development [1,2]. An increase in the world’s population, industrialization, and an accompanying increase in the level of environmental pollution cause some deterioration of the quality of water resources and limits their availability [6,7,8]. Water resources are affected by climate change and the intensification of the urbanization process, which causes significant hydrological changes in catchment areas. These changes have a negative impact primarily on the quantity and quality of rainwater, causing an increase in the speed and volume of runoff, a reduction in infiltration, an increased risk of flooding, and the hydraulic overload of sewage systems [9,10,11]
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