Viabilidade econômica para implantação de sistema de aproveitamento de água pluvial em residência unifamiliar

Abstract

Among the several technologies disseminated in the last decades, the reuse of rainwater has been shown to be a simple and effective alternative for the reduction of drinking water consumption. The most common system for reuse of rainwater consists of capturing water from roofs, followed by the necessary treatments and storage in reservoirs for later distribution at points where it is not necessary to use potable water. Studies are therefore needed to verify the possibility of applying rainfall in different regions and buildings of different categories, and in this context the research in question has developed. The application of the system was analyzed in a single-family residence in the city of Uberlândia-MG, with the objective of verifying the possibility of implantation of the system under the quantitative and economic points of view. For this purpose, the water regime of the region was first analyzed, showing the viability of the system from a quantitative point of view, and it was able to supply a large part of the non-potable demands. Then, each of the components of the system was dimensioned for later budgeting and economic analysis. The sizing of the reservoirs was done using the methods present in the Brazilian standard that regulates the abstraction and storage of rainwater for non-potable uses, ABNT 15527: 2007. The results were compared among themselves and also with the computational method presented in the Neptune 4.0 program. These comparisons showed that the methods of German Iteration and Practice, together with the Neptune 4.0 method, presented better values for the reservoirs from the economic point of view, as smaller volumes returned. The analysis was done for a residence with a catchment area equal to 150.4 m² and considered 3 demands: A, B and C, equal to 4.5 m³, 5.8 m³ and 11.6 m³. Total reserve volumes of 3.5 m³, 6m³ and 8.5m³ were found for demands A, B and C, respectively. The economic analysis was done using the software Netuno, taking into account the costs of implementation, operation and maintenance of the system, and for that, none of the systems A, B and C presented economic feasibility, not obtaining an expectation of return of investment in the 20-year useful life of the system. The non-viability of the system is possibly due to the city's low water tariffs and the high cost of implementation, combined with the region's large rainfall variation.