Viabilidade de implantação de sistema de reúso de águas cinzas em edificação residencial multifamiliar

Abstract

Facing the growing demand for water, society seeks solutions that promote the rational and efficient use of this scarce resource. The northeastern region of Brazil, which experiences prolonged periods of drought and water stress, is heavily affected by water scarcity. Water reuse emerges as an alternative to mitigate these effects by directing treated effluents to activities that require lower-quality water, thereby freeing up potable water for more essential uses, such as human consumption. Non-potable urban water reuse encompasses various applications, including irrigation of green areas, pipe cleaning, and road washing. In residential condominiums, where water consumption is significant, there is great potential for water reuse. Implementing systems that utilize graywater can lead to savings in potable water and enhanced environmental sustainability in buildings. Although still in its early stages in Brazil, it is crucial to encourage the implementation of these systems through economic and technical feasibility studies, which assess the cost-benefit relationship and the potential for saving potable water. In this context, the main objective of this study is to determine the payback period for investing in a non-potable graywater reuse system in a multifamily residential building to be implemented in Natal, Brazil. To achieve this, a graywater collection, distribution, and treatment system was installed in the building to estimate the costs of implementation, operation, and maintenance of the reuse system. The payback period for the invested capital was calculated at 8,7 years, which, although considered a medium-to-long-term financial return, is viable due to the invaluable benefits generated for the environment and society, as well as the resulting cost savings. It is worth noting that Law No. 11.332/2022, recently enacted, provides discounts on water bills based on the quantity of water reused through these systems, further enhancing the potential savings.