Understanding the preferences for different types of urban greywater uses and the impact of qualitative attributes

Greywater reuse can allow substantial improvements in the efficiency of potable water systems. However, widespread uptake of greywater reuse depends on its acceptability by the population. Previous studies have assessed the implementation costs of greywater reuse technology, and considered its acceptability in principle. Although cost is clearly very important in terms of adopting/installing the technology, the actual perception of greywater reuse is crucial in driving the acceptability of use and the long-term success of the technology. This study uses discrete choice models to quantify, for the first time, the preferences of different socio-economic groups for greywater of different quality (colour, odour) and for different uses inside homes. A stated choice survey that removed the influence of installation costs was developed, and implemented in Santiago, Chile. Although legislation allows greywater use in Santiago, it does not take place at any meaningful scale. Results show that, in decreasing order of preference, there is an overall acceptance for using high quality treated greywater for toilet flushing, laundry, garden irrigation, hand washing and, shower/bathtub use, but not for drinking. When the quality of appearance in terms of colour and odour gets worse, monetary incentives could be needed even for those uses that do not involve human contact. Gender, age, educational level, water expenditure level, and in particular previous knowledge about greywater reuse, are important determinants of acceptability and thus willingness to pay for greywater use; however, their importance varies according to the type of use. Our results provide important insights for understanding the conditions that would precipitate rapid and wide uptake of greywater reuse in cities, and thereby make better use of limited water resources

An integrated analysis of the March 2015 Atacama floods

In March 2015 unusual ocean and atmospheric conditions produced many years' worth of rainfall in a ~48 h period over northern Chile's Atacama Desert, one of Earth's driest regions, resulting in catastrophic flooding. Here we describe the hydrologic and geomorphic drivers of and responses to the 2015 Atacama floods. In the Salado River, we estimated a flood peak discharge of approximately 1000 m3/s, which caused widespread damage and high sediment loads that were primarily derived from valley‐fill erosion; hillslopes remained surprisingly intact despite their lack of vegetation. In the coastal city of Chañaral, flooding of the Salado River produced maximum water depths over 4.5 m, meters thick mud deposition in buildings and along city streets, and coastal erosion. The Atacama flooding has broad implications in the context of hazard reduction, erosion of contaminated legacy mine tailings, and the Atacama's status as a terrestrial analog for Mars

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

To legally permit greywater reuse as a management strategy, it is necessary to establish allowed uses, as well as guarantee legitimacy, safety and maintain public trust. Cities with previous experience in greywater reuse have reconfigured their regulations according to their own evidence with decentralized water reuse systems. This has allowed them to encourage or restrict certain indoor uses of treated greywater. However, cities starting to use these residential schemes lack the experience to reconfigure their water and sanitation regulation, and thus need “blindly” decide on the type of greywater uses to allow in order to achieve a balance between users’ acceptability and avoiding public health problems. In this research, we analyse hypothetical situations of greywater reuse based on real evidence related to decentralized water systems. The main objective of this study is to evaluate the heterogeneity of individuals' preferences regarding residential greywater reuse for six intended indoor uses, using stated choice experiments and a latent class model. Hence, we obtain preliminary evidence about the direction that the regulation or pilot tests should take. We use the context of Santiago (Chile) as a reference, where although allowed, greywater reuse is not taking place widely. Our results show that survey respondents can be classified into four classes (enthusiasts, greywater sceptics, appearance conscious and water expenditure conscious), according to the preferences for the different types of indoor greywater reuse and the appearance of the treated greywater. From a policy perspective, our results show differences across classes as a function of socioeconomic characteristics and previous greywater reuse knowledge, as well as wider household characteristics, including the presence of sensitive individuals (under 15 and over 74 years old), number of residents, number of sanitary devices, and location and type of garden

Using hybrid choice models to capture the impact of attitudes on residential greywater reuse preferences

The reuse of treated greywater in a residential setting could contribute substantially to easing problems with water scarcity. This paper argues that preferences in relation to reusing greywater for different uses within the home vary across households and can be driven at least in part by psychological constructs, such as attitudes and perceptions, which might appear irrational at face value from an economic perspective. To better understand heterogeneity in behaviour in a greywater reuse context, data from a stated choice survey were analysed using a hybrid choice model with latent variables, allowing us to incorporate measurable characteristics of the decision makers as well as other elements that cannot be measured directly (e.g. attitudes towards greywater reuse). Our results provide evidence on the preferences for different uses of treated greywater, and about the heterogeneity of choices among individuals and uses. The model suggests that heterogeneity in the acceptance of greywater reuse can be linked back mainly to underlying attitudes, for all uses except drinking. This knowledge can be used as an input to evaluate diffusion strategies to increase greywater reuse acceptability focused on messages about its direct (i.e. water bill savings) and indirect benefits (environmental benefits, water security, autonomy)

From mathematical models to policy design: Predicting greywater reuse scheme effectiveness and water reclamation benefits based on individuals’ preferences

The residential reuse of greywater has attracted interest in recent years as a strategy to face water security problems. Nowadays, some cities such as Santiago de Chile are seeking to promote new laws that allow residential greywater reuse and make the incorporation of the necessary infrastructure (machinery and a parallel pipe system) mandatory for new buildings. The success of any such schemes, in terms of the amount of mains water that can be saved, is clearly influenced by the decision that individual consumers make on whether or not to use the parallel system, as they will also be the ones to face the potential externalities produced by the system (e.g., odours, noise from technology). Understanding and anticipating the behaviour of individuals is not an easy task, especially in the context of systems not yet widely implemented, but the groundwork has been laid with the application of approaches that allow analysts to determine the heterogeneity in consumer preferences based on the qualities of the product or service. However, there has been a lack of focus on making predictions that quantify the impact of acceptability on the volume of water recovered, driven in part by methods that been applied. This paper presents a way of predicting policy effectiveness and potential greywater reclaim benefits based on individuals' preferences. For this, we use two existing models that allow us to make predictions of greywater reuse for different domestic purposes. In a case study application to the city of Santiago de Chile, we carry out scenario tests to predict the potential uptake under potential future policy settings and show how allowing for an additional permitted use of greywater could save several hundred litres of water per month per household