An Analysis of the Effectiveness of Two Rainwater Harvesting Systems Located in Central Eastern Europe

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.

Opportunities and Threats of Implementing Drain Water Heat Recovery Units in Poland

“…Poland is an example of such a country, where the conventional sources of energy, mainly coal and lignite, cover more than 80% of total energy demand [10]. The consequence of such an approach is deteriorating geological conditions related to mining of fossil fuels and excessive emissions to the atmosphere of the products of fuel combustion, particularly carbon dioxide [11].Buildings are particularly dependent on the availability of natural resources [12,13]. According to previously published data [14], it is estimated that the total energy consumption in residential and commercial buildings accounts for over 20% of global demand.…”

“…Buildings are particularly dependent on the availability of natural resources [12,13]. According to previously published data [14], it is estimated that the total energy consumption in residential and commercial buildings accounts for over 20% of global demand.…”

The Quality of Stored Rainwater for Washing Purposes

“…The RWH is an alternative, widely available, ecological and beneficial source of fresh water suitable for an entire range of uses and areas [2]. Rainwater harvesting increases water self-sufficiency and delays the need to build new centralized water infrastructure [3][4][5]. Globally implemented RWH systems could cover up to 90% of household water consumption [6] and the RWH plays a critical role in solving the world's problem of increased water stress [7,8].…”

Reduction of Potable Water Consumption and Sewage Generation on a City Scale: A Case Study in Brazil

“…In order to promote potable water savings in buildings, several studies about water-saving plumbing fixtures, greywater reuse, and rainwater harvesting have been carried out [2,[4][5][6][7][8][9][10][11][12]. In these studies, the authors determined potable water savings in buildings due to the adoption of one or more of these strategies.…”

“…In a dwelling, water savings could be 28.9% by replacing conventional plumbing fixtures with water-saving ones, 21.0% with greywater reuse, and 30.7% with rainwater harvesting [2]. The combination of greywater reuse and rainwater harvesting systems could reduce water consumption by up to 46.3% in a public school [6], 48% in a university campus [8], and 29% in a university dormitory [11]. The use of water-saving plumbing fixtures combined with rainwater harvesting systems reduced the water consumption by approximately 15% in residential buildings [12].…”