Avaliação do potencial regional de reúso de água para fins não potáveis em bacias hidrográficas

Abstract

In Brazil, due to population growth and extreme weather events, there is increasing pressure on the water matrix, leading to more frequent scenarios of scarcity and conflicts over water use. Therefore, there is an increasing need to enhance water resources management with initiatives aimed at sustainability. The planned reuse of water can be an effective strategy in managing the water matrix, bringing benefits in cultural, social, environmental, and economic dimensions. In this sense, studies on the potential for water reuse are essential as they provide relevant information on the subject. The objective of the study was to develop a multicriteria methodology to assess the potential for water reuse from treated effluents from Sewage Treatment Plants (STPs), using the Rio do Sinos (G20) and Rio Sapucaí (GD5) watersheds as case studies. The methodology was divided into four stages. The first stage involved the Characterization of the study areas, the second referred to the Reuse potential, presenting the basic steps to assess the potential for reuse. The third stage involved the Evaluation of legislation and management instruments for water resources and sanitation, including an analysis of the existence of plans, projects, actions, and laws related to the practice, and the fourth was the Evaluation matrix of the STPs with a multicriteria analysis of the potential for reuse of treatment units. Through the study, it was possible to estimate the potential for water reuse in the watersheds and indicate regions with the greatest potential. The main results indicated that in G20 the greatest potential for reuse is in Band 1 of the offer with a flow rate of 245.7 L/s and the capacity to meet 46% of the industry demand or 17% for irrigation, and in the municipalities of Esteio, São Leopoldo, and Sapucaia do Sul, there is a region with high potential for industrial demands. In GD5, the greatest potential for reuse is in Band 2 of the offer, with a flow rate of 394.8 L/s and the possibility of meeting more than 100% of the industry demand or 68% of irrigation, and only in the municipality of Pouso Alegre, a region with high potential was indicated. The watersheds are located in States with their own legislation for water reuse, a positive factor for the implementation of the practice, but the absence of municipal legislation and plans that address the issue was evident. Finally, given the methodology employed, the results achieved, and the proposed Product, the study can contribute to enhancing the management and planning of water resources and sanitation in watersheds, fostering more assertive decision-making.