water Article Potential for Potable Water Savings Due to Rainwater Use in a Precast Concrete Factory Giovanna Bertuzzi and Enedir Ghisi *   Citation: Bertuzzi, G.; Ghisi, E. Potential for Potable Water Savings Due to Rainwater Use in a Precast Concrete Factory. Water 2021, 13, 448. https://doi.org/10.3390/w13040448 Academic Editors: Fernando A. L. Pacheco and Warish Ahmed Received: 4 January 2021 Accepted: 5 February 2021 Published: 9 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Laboratory of Energy Efficiency in Buildings, Department of Civil Engineering, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil; giovannakbertuzzi@gmail.com * Correspondence: enedir.ghisi@ufsc.br; Tel.: +55-48-3721-2115; Fax: +55-48-3721-5191 Abstract: The objective of this paper was to assess the potential for potable water savings due to rainwater use in a precast concrete factory in southern Brazil. The economic feasibility and the rainwater quality were also assessed. The current water consumption, future water demand, and rainwater demand in the factory were estimated. The future demand considered was two times higher than the current water consumption since there were plans to increase the production. Three scenarios were then simulated using the computer programme Netuno. The ideal rainwater tank capacity, the potential for potable water savings, and the economic feasibility analysis for each scenario were estimated. Samples of rainwater were collected in the factory and tested for quality for manufacturing precast concrete. For a rainwater tank capacity equal to 25,000 L, the potential for potable water savings for the first scenario was 55.4%, but the first scenario was considered economically unfeasible. For the same tank capacity, the second and third scenarios presented viable results regarding potable water savings and payback. As for the rainwater quality, it was proven to be adequate for manufacturing precast concrete. The main conclusion was that rainwater can be used to manufacture precast concrete in the factory studied herein. Keywords: rainwater harvesting; rainwater quality; precast concrete; financial analysis; com- puter simulation 1. Introduction Rainwater harvesting systems may be installed in different kinds of buildings, such as houses, commercial and residential buildings, factories, and many others. The economic benefit of the installation of the system is still a matter of concern among specialists. The economic feasibility varies significantly for each region, being highly dependent on the water tariff charged by the local water company, the rainfall, and the adequate sizing of the rainwater tanks [1]. A study carried out by Ghisi and Schondermark [2] about the installation of rainwa- ter harvesting systems in houses in the state of Santa Catarina (Brazil) showed that the economic benefits of these systems depend on the water demand. Although there would be environmental benefits due to the installation of rainwater harvesting systems in all houses, there would be economic feasibility only in those with higher water demands or a higher number of occupants. The use of rainwater can also be applied to situations that demand low volumes of water. Fernandes et al. [3] projected a rainwater harvesting system in a waste treatment installation close to the city of Mirandela (Portugal). Rainwater would be used to wash cars and other equipment, clean outdoor concrete and asphalt floors, and irrigate green areas. Fernandes et al. [3] pointed out that for installations that demand small amount of water, the water harvesting systems would be efficient even if the tank capacity did not supply 100% of the demand. The tank capacity supplied 90% of the water demand. After going through adequate treatment, rainwater can be used in different applica- tions that do not require potable water. The Brazilian standard NBR 15527 [4] presents Water 2021, 13, 448. https://doi.org/10.3390/w13040448 https://www.mdpi.com/journal/water