Capturing and analysing heterogeneity in residential greywater reuse preferences using a latent class model

Economics of household preferences for water-saving technologies in urban South Africa

Drought severity is expected to increase in South Africa in the coming years, given the deteriorating effects of climate change on rainfall patterns, global temperature, and evaporation. A common mitigation strategy adopted by households is to promote water demand management initiatives to reduce water consumption volume and complement existing water supply management approaches implemented by suppliers. This study contributes to the discussion on adaptation strategies by investigating household preference heterogeneity for water-saving technologies through empirical evidence from urban Cape Town, South Africa. Using a choice modelling framework, we collected primary survey data from 512 urban households in five of the city's major suburbs and investigated heterogeneity among the households based on their preferences for characteristics embedded in four water-saving technologies. Four preference classes were identified by accounting for taste heterogeneity. Overall, respondents had the highest marginal willingness to pay (MWTP) for the greywater technology alternative at 17,025 ZAR (US$ 1142) while rainwater technology has the least willingness to pay value at 5206 ZAR (US$ 349). In addition, the results show that respondents in classes 1 and 2 have a high interest in technologies that save a large quantity of water, whereas members of classes 3 and 4 rely on inexpensive conservation and behavioral habits as climate adaptation measures. This study has important policy implications for many water-stressed and arid cities within and outside South Africa since like Cape Town, many large cities require long-lasting measures that help reduce the pressure on their strained water systems.

Life cycle assessment of greywater treatment systems for water-reuse management in rural areas

Water scarcity is a major concern worldwide. Population growth, as well as the intensive use of water resources for industrial and agricultural activities, among others, have caused water stress in various regions of the world. Rural areas are usually more affected due to water scarcity and a lack of sanitary infrastructure. The current practices associated with urban water management have been considered inefficient to respond to these problems. In recent years, the reuse of greywater has emerged as a promising and sustainable alternative. Several pilot greywater treatment systems have been implemented in rural areas of different countries, however, studies about the environmental impacts of these decentralized systems under different scenarios are lacking. In this work, the life cycle assessment of greywater treatment systems considering several scenarios was studied. Our results showed that the decrease in environmental impacts due to the saving of drinking water is more evident when the water supply is carried out through cistern trucks. This occurs because the environmental impact of land transport of water is extremely high and represents over 89% of the global warming indicator [kg CO₂ eq] and 96% ozone depletion [kg CFC-11 eq] contributions of the system. Greywater treatment systems with backwashing and solar panels as a source of energy have lower environmental impacts, reducing CO₂ and CFC emissions by 50% for the maintenance phase and by 85% (CO₂) and 47% (CFC) for the operation phase. Furthermore, the acquisition of solar panels was economically feasible, with a payback of 19.7 years. This analysis showed the environmental feasibility of small-scale greywater treatment systems in rural areas affected by water scarcity. Furthermore, the proposed approach has contributed to understand the impact of greywater treatment systems in rural areas, which could become a support tool to integrate greywater reuse practices in different communities.