Rainwater Harvesting System for Industrial Buildings: The Case Study of Continental Advanced Antenna, Vila Real, Portugal

Large industrial units generally consume considerable volumes of water for use by workers and sometimes in the manufacturing process, but on the other hand, they generally have large coverage areas that facilitate and enable the capture of large quantities of rainwater. Rainwater harvesting systems (RWHSs) are an alternative water supply with high potential for significant water and economic savings in buildings of this type, also with benefits for water resource sustainability. This paper presents a case study that refers to the design and economic viability determination of an RWHS to be installed in the industrial building of Continental Advanced Antenna Portugal, using an innovative tool called SAPRA—a rainwater harvesting and greywater reuse system in buildings. The main goal was to understand water consumption patterns in social areas (common to most of the industrial typologies) and determine whether RWHSs are feasible in such uses (discarding the production chain). The case study allowed for verification that the assumptions regarding the calculation period design flow significantly interfere with the design flow and the storage capacity. The analysis of the 10-year period yields the most realistic results, and can be framed, if necessary, within the range provided by the analysis of the driest and wettest years. The investment costs should between EUR 90 and 95 million, with annual savings of EUR 7 to 12 million, respectively. The expected payback period is between 7 and 11 years, which is quite feasible and very relevant. This may be an excellent example of how, even within the industries that do not need water for production, this may save significant volumes of water, contributing to the efficient use of this valuable resource.