Análise crítica dos principais dispositivos legais e institucionais disponíveis no Brasil para reuso de águas cinza com fins não potáveis

Abstract

The serious hydric crisis currently affecting several regions of Brazil, in terms of both quantity and quality of available water, emphasizes the very urgency of actions to safely meet current and future water demands. In this context, the reuse of water, particularly the reuse of graywater, which represents 50-70% of the domestic sewage, is demanded in order to ensure that such needs are met. However, Brazil has a shortage of specific water reuse laws in all three administrative spheres. Hence, the goal of the present study was to gather the current legislation on graywater reuse for non-potable purposes in Brazil, analyzing them critically. For such task, a bibliographical survey, between May/2019 and April/2021, on scientific papers, public documents, norms and state and municipal laws, was accomplished. Were found 12 main publications, amongst technical standards, public documents and laws. All related to graywater reuse at federal, state and municipal level. Of these, only 4 establish quality parameters for non-potable usage of treated effluent. It is noteworthy that, so far, Brazil does not have a federal law which establishes the guidelines for graywater reuse. The publication that settled the most restrictive parameters was the Manual for Water Conservation and Reuse in Buildings (SINDUSCON, 2005). The most restrictive parameter found was the one about Thermotolerant Coliforms, required as "absent" on the SINDUSCON Manual’s (2005) class 1 of reuse waters, on the Municipal Law of Niterói No. 2.856/2011 and in the Municipal Law of Belo Horizonte No. 10.840/2015. Very restrictive parameters, especially when potable standards are adopted for non-potable purposes, make the implementation of a graywater reuse system difficult, or even impossible. The Bioágua Family System (Brazilian Semiarid) and the Royal Blue Residential Building (Vitória-ES) were the main successful cases in the implementation of graywater reuse identified in this study. In a proximate future, it’s possible to assert that, without the practice of water reuse, it shall be impossible to guarantee the water security of the population and the environment. Since water participates in a natural and cyclic process, there is no possibility of an entirely clean water in a certain region where it has already been used, and this resource might reach saturation levels when the pollution speed exceeds the recovery and self-depuration of the waterbody. Therefore, the higher the volume of treated and reused effluents, the lower the water uptake from springs and water resources pollution by the discharge of effluents.