Electricity savings by reducing water consumption in a whole city: A case study in Joinville, Southern Brazil

Abstract

This paper aims to propose a method to estimate the electricity savings in water supply and sewage systems due to the reduction of potable water consumption on a city scale. The method was applied in a case study in Joinville, a city located in Southern Brazil. The strategies considered to promote water savings were: replacement of toilets, greywater reuse, rainwater harvesting and combination of these three strategies. Single-family residential, multi-family residential, public and commercial sectors were assessed. For each building sector, minimum and maximum potable water consumption and sewage generation reductions due to each strategy were determined, so the range of possible electricity savings in water supply and sewage systems were estimated. The financial feasibility of adopting these strategies was verified using data from the National Information System on Sanitation and local utility. The most significant energy savings were provided by the simultaneous adoption of the three strategies (from 2136.8 MWh/year to 8951.5 MWh/year). However, greywater reuse and rainwater harvesting presented savings similar to those provided by the three strategies. The single-family residential sector led to the highest energy savings, corresponding to more than 50% of total electricity savings in seven of eight cases analysed, while the smallest contribution was from the public sector. The local utility would not fail to profit in any of the scenarios analysed. Thus, in addition to the environmental benefits of water savings, lower sewage generation and electricity savings, the local utility would also profit from adopting these strategies on a city scale.