Rainwater harvesting in Brazil: investigating the viability of rainwater harvesting for a household in Brasília

Abstract

This paper addresses the issue of harvesting rain for later use, as part of a decentralised sustainable urban water management scheme, by adapting an existing house in order to study the viability of rainwater harvesting (RWH) systems. The goal of this study was to investigate the potential solutions for the application of a domestic RWH system for a household in Brasilia and identify the most favourable system for such, considering water conservation and its economic viability. Based on the investigated the household’s total annual water consumption and rainwater yield capacity, two RWH systems were proposed: a treated and a potable indirectly pumped system. The treated RWH system, used for toilet flushing, dish washing, clothes washing and sink washing, is capable of conserving 222.65m/yr of potable water. Considering the total annual savings of R$1,962.54 (US$882.71), this system has a payback period of approximately 11 years. The potable RWH system, applied to the existing plumbing, supplies potable rainwater into a pre-existing water tank for all uses. This system presented a lower payback period of 91⁄2 years, is able to conserve 456.25m/yr of mains water and contains a total annual savings of R$3,659.29 (US$1,645.88). The potable RWH system conserves more water, and has a lower payback period than the treated RWH system because it harvests and uses more rainwater. Although, there is a setback, the potable system contains a much higher capital cost and operational cost, requiring a higher initial investment capital and annual expenses.