Environmental toxicology and chemistry studies have found that household consumption of cosmetics, detergents, and pharmaceutical products may account for the increasing occurrence and fate of chemicals of emerging concern namely micropollutants (MPs) in aquatic ecosystems. This highlights the relevance of the precautionary principle and the upgrading of wastewater treatment plants (WWTPs) to improve water quality and avoid potential negative ecological effects by MPs. However, for European countries, as requested by the Water Framework Directive, cost-benefit analysis has to be performed, to prevent choice of disproportionately expensive mitigation measure. The valuation of the environmental benefits emanating from upgrading wastewater treatment are needed to make efficient decisions about the preservation of water resources, as modernizing (WWTPs) with new technologies may require substantial investments. Measuring the benefits generated by WWTPs upgrading programmes in terms of use and non-use values of aquatic ecosystem that underlie households' support for achieving good ecological and chemical status of waterbodies, is essential. Households are the main users of water infrastructure services and the existence of such benefits may suggest that they are willing to pay additional charges for higher water quality resulting from reduced levels of micropollutants (Logar et al., 2014). However, from a technological standpoint, selection of WWTPs for upgrading is based on consideration of feasibility and performance, but also on the anticipated MPs load. This is why source control has become a major part of policy scenarios for reducing the emissions of MPs from domestic sewage discharge, while their success can only be expected on the long-term (Eggen et al., 2014). As such, the economic valuation of the benefit of alternative scenarios for removing MPs from domestic sources involves trade-off between the usage of source control devices (education program, awareness campaigns) that lead to behavioural change, and modernisation of wastewater treatment. This study aims to address this trade-off when estimating welfare gains (social benefits) from MPs removal policy scenarios. However, MPs removal from wastewater will mainly involve non-use values related to the preservation of aquatic species and ecosystem functions and services, as drinking water is not supplied from surface waters. This highlights the relevance of the Choice Experiment method to inform on this trade-off through the preferences of the main beneficiaries (households as citizens) of improved water resource quality and aquatic ecosystem health. However, where the technique is the most useful (assessing non-use value) is also where it is likely to be less convincing for decision-making analysis (Atkinson et al., 2012). Non-use value may arise from altruism and ethical consideration, providing support to moral satisfaction and insensitivity to scope (Jacobsen et al., 2008). Therefore, it is not obvious that respondents can or will make reliable trade-offs between the expected benefits from different policy scenarios, when faced with this question during the survey. We thus develop a choice experiment process that gives careful consideration to this purpose in order to obtain the economic value of MPs removal policy from the domestic wastewater discharge of households served by the municipal sewer network of Bordeaux metropolitan area, based on the preferences of these households. Specific attention would be paid to the heterogeneous nature of psychological and ethical foundation of non-use values and to test the influences of respondents' environmental attitudes on their preferences. We select as scenario's attributes : MPs to be targeted by treatment plant, or by source control devices (education program, information dissemination) that favour behavioural change, to insure that our scenarios give a clear picture of the trade-offs between the two options and their outcomes (Birol et al., 2006). We also introduce the time schedule for the implementation of advanced WWTP as a scenarios' attribute, to allow direct estimation of the effect of individuals' time preference (Faccioli et al., 2016) with regard to precautionary approach to environmental policy. We choose to consider the ecological status of the waterbody as an attribute in the scenario to remind unfamiliar respondent that the main political challenge (Barkmann et al. 2008) of each scenario is the preservation of biodiversity and aquatic ecosystem health. Our monetary attribute is based on a proposed rate increase for water service fees. Therefore, the efficient design was applied to obtain 48 alternative scenarios, split into 24 choice sets composed of three alternatives. In order to reduce the cognitive burden placed on respondents during the choice exercise, the 24 choice sets were further divided into six separate blocks. Each respondent answered four choice sets. The opt-out option was defined as neither Option A nor Option B, meaning that respondent may opt for "laissez-faire la nature - let Mother nature do the work", for a specific choice set. We opt for a web-based survey to yield a sample of 500 individuals. To examine the existence of hypothetical bias, respondent is invited to express their uncertainty after each choice task. We approach respondents' ethical and moral motivations in the form of environmental awareness and concern. We thus use the New Ecological Paradigm (NEP) scale (Dunlap et al., 2000) to assess respondents' core beliefs about the relationship between human, technology and nature. This is an ongoing study, and data collection is in very early stage. The trial run of the survey will start in April. We will discuss the findings of our study in terms of scope issues and moral motivations. Latent class modelling will be developed to address these questions empirically and assess the influences of respondents 'environmental attitudes on preferences. We hypothesise that in the presence of warm-glow effect, survey participants with a higher level of environmental concern will express positive but constant willingness to pay for MPs removal scenarios, just for signalling support to do "the right thing". However, we have little idea of how "ecological citizens" who display a sense of environmental responsibility and consciousness will vote. Indeed, the socio-psychological literature provides conflicting answers to this question. According to the NEP, a participant with higher environmental concern may express higher preference for radical change in behaviour and will favour source control devices. At the same time, we cannot exclude the possibility that more individual ecological consciousness may translate into demand for advanced wastewater treatment technology. The most fruitful result of this study is probably the impetus it gives for testing the impact of "additional information" on the stability of preferences, during a follow-up survey.