Viabilidade do aproveitamento domiciliar de águas pluviais em municípios de regimes pluviométricos distintos

Abstract

The objective with this study was to analyze the technical and economic viability of rainwater harvesting reservoirs, designed for three cities of Minas Gerais State (Lavras, Montes Claros and Uberlândia). For technical viability analysis, the methods presented by NBR 15527 were used, being Rippl, Simulation, Azevedo Netto, German, English and Australian. To this end, the historical rainfall series of each city were used for the period from 01/01/1988 to 12/31/2018. The adopted harvesting area was 100 m2, and drinking water demands of 100, 150 and 300 L per capita were considered in houses occupied by three inhabitants, with the percentage of substitution of drinking water for rainwater equivalent to 30%. For economic viability analysis, Discounted Payback and Profitability Index methodologies were used. These were based on the fares charged by the water supply companies and on the acquisition costs of the designed reservoirs. The results showed that the reservoirs dimensioned by the Simulation Method had better technical viability compared to the others. With this one, the simulation of the reservoirs' behavior in every month of the year proved their effectiveness including months of low rainfall. In addition, the time required to return the investment was within the adopted 30-year horizon, varying from 4.31 to 25.98 years. The investment was also considered profitable when analyzing the Profitability Indexes, which were all higher than one, with values oscillating from 1.16 to 15.79. Lavras, the second city with the highest average annual precipitation value among the evaluated, was the most economically viable for the implantation of reservoirs, highlighting the water and sewage treatment cost as a great relevance factor in the analysis.