Water–energy nexus in houses in Brazil: comparing
rainwater and gray water use with a centralized system
A. S. Vieira and E. Ghisi
ABSTRACT
The objective of this paper is to assess the potential for energy savings in water and sewerage services
by means of on-site integrated water and sewage management strategies in low-income households in
Florianópolis, Brazil. The on-site water efficiency measures include reclamation of gray water and
rainwater use. The water and energy saving potential of both strategies were studied, and their energy
intensities were compared to centralized water and sewerage services. Furthermore, the water
consumption pattern for 10 low-income households was empirically determined using smart meters;
the rainwater supply was estimated by using the computer program Netuno 4.0; and the water supply
and sewage reduction potential of gray water systems were determined using a theoretical method. On
average, the gray water and rainwater supply capacities were equivalent to 24% and 43% of the total
water consumption of households, respectively. In regard to energy savings, rainwater harvesting was
the most energy intensive strategy (0.86 kWh/m³), followed by centralized systems (0.84 kWh/m³);
whereas, gray water was the most energy efficient strategy (0.54 kWh/m³). The findings suggest that
alternative water and sewerage services may promote energy savings in comparison with centralized
ones only when a concomitant reduction in sewage production is achieved.
A. S. Vieira
E. Ghisi (corresponding author)
Department of Civil Engineering, Laboratory of
Energy Efficiency in Buildings,
Federal University of Santa Catarina,
Florianópolis, SC,
88040-900,
Brazil
E-mail: enedir@labeee.ufsc.br
Key words | gray water reclamation, low-income households, rainwater harvesting,
water–energy nexus
INTRODUCTION
The water–energy nexus has been recognised as an overarch-
ing concept to improve management practices in the water
and energy sectors alike (Gleick ; Lofman et al. ;
Malik ; Retamal et al. ; Proença et al. ; Scott
et al. ; Ackerman & Fisher ). The energy sector
depends on water availability for power generation
(Glassman et al. ), and the water sector demands energy
for water pumping and treatment (Lee & Tansel ).
In Brazil, the lack of adequate sanitation and housing
facilities is common in low-income areas. From 2010 to
2014, the Brazilian government invested approximately
R$71.7 billion (US$42.9 billion in December 2010) to
address the deficit of low-income housing. In this context,
there are opportunities to build low-income houses in
which sustainable initiatives are taken into account from a
water–energy nexus perspective in order to enhance water
and energy services on an urban scale.
The objective of this study is to evaluate the potential for
energy savings in water and sewerage services by means of
gray water reclamation and rainwater harvesting in low-
income households in Florianópolis, southern Brazil.
METHOD
Overview
The study considered a period of 20 years, from 2010 to
2030. The base year (2010) corresponds to the most recent
information provided by the National Sanitation
274 © IWA Publishing 2016 Water Science & Technology: Water Supply | 16.2 | 2016
doi: 10.2166/ws.2015.137
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