Financial feasibility of end-user designed rainwater harvesting and greywater reuse systems for high water use households

Abstract

Water availability pressures, competing end-uses and sewers at capacity are all drivers for change in urban water management. Rainwater harvesting (RWH) and greywater reuse (GWR) systems constitute alternatives to reduce drinking water usage and in the case of RWH, reduce roof runoff entering sewers. Despite the increasing popularity of installations in commercial buildings, RWH and GWR technologies at a household scale have proved less popular, across a range of global contexts. For systems designed from the top-down, this is often due to the lack of a favourable cost-benefit (where subsidies are unavailable), though few studies have focused on performing full capital and operational financial assessments, particularly in high water consumption households. Using a bottom-up design approach, based on a questionnaire survey with 35 households in a residential complex in Bucaramanga, Colombia, this article considers the initial financial feasibility of three RWH and GWR system configurations proposed for high water using households (equivalent to >203 L per capita per day). A full capital and operational financial assessment was performed at a more detailed level for the most viable design using historic rainfall data. For the selected configuration (‘Alt 2’), the estimated potable water saving was 44% (equivalent to 131 m3/year) with a rate of return on investment of 6.5% and an estimated payback period of 23 years. As an initial end-user-driven design exercise, these results are promising and constitute a starting point for facilitating such approaches to urban water management at the household scale.

End-User Cost-Benefit Prioritization for Selecting Rainwater Harvesting and Greywater Reuse in Social Housing

“…In a study from Spain, the perception of health risks from GWR showed a high influence on acceptability. Concerning the willingness to undertake operation and maintenance activities, 86% of participants were willing to perform these activities fortnightly, 69% twice a week, and 33% daily, coinciding with findings from previous studies [14].…”

“…Although membrane filtration is more effective to achieve the required level of certain parameters, these systems have higher energy and The average water consumption was 130 + 61 litres per capita per day (lpcd) with a coefficient of variation (CV) of 47%. This consumption is similar to that reported in Colombia for stratum one households by Ángel, Rozo [26] (124 lpcd), and considerably lower than that reported by Oviedo-Ocaña, Dominguez [14] in stratum six households in the study area (203 lpcd). This value is also within the range of the indoor domestic water demand (excluding garden irrigation and other external uses) reported by Friedler and Hadari [9] and Londra, Theocharis [35] in developed countries.…”

“…Concerning the willingness to undertake operation and maintenance activities, 86% of participants were willing to perform these activities fortnightly, 69% twice a week, and 33% daily, coinciding with findings from previous studies [14]. The average water consumption was 130 + 61 litres per capita per day (lpcd) with a coefficient of variation (CV) of 47%.…”

“…For the sample of householders from the study context, the end-user acceptability for GWR and RWH was 78% and 91%, respectively (Figure 3), which aligns with the findings of Oviedo-Ocaña, Dominguez [14] (86% and 97%, respectively), in households from a higher socioeconomic stratum (stratum six) in Bucaramanga. This is also in line with other international studies such as for the UK [32] (64 and 93%, respectively), and in Oman, where the GWR acceptability was 87% [33].…”

“…Oviedo-Ocaña, Dominguez [14] set out a detailed method for the formulation of alternative RWH/GWR system designs with an integrated financial assessment. The steps in the method are:…”