Unveiling socio-psychological determinants behind residential treated greywater adoption: Integrating theory of planned behavior and norm activation model.

Persistent water scarcity and resource degradation threaten urban water security, driving water utilities to promote alternative sources such as residential treated greywater (RTG) as a sustainable solution. However, public resistance remains the primary barrier to the long-term and widespread implementation of any water reuse initiative. Hence, it is paramount to gain exhaustive insights into the motivations and mechanisms behind voluntary RTG adoption behavior, contributing to devising more impactful strategies for promoting such initiatives. Although environmental psychology has laid a robust groundwork in understanding pro-environmental behaviors and identifying entry points of behavioral intervention, a notable gap persists in RTG research, particularly in the Middle East, such as Iran. Hence, this research sought to explore the psychosocial drivers underlying households' RTG adoption through introducing an innovative theoretical framework that integrates the theory of planned behavior with the norm activation model, further extended by perceived risk and anticipated emotions (guilt and pride). A questionnaire was developed based on an extensive literature review and distributed in Isfahan City via an online self-administered survey, utilizing a blend of convenience sampling and cluster sampling techniques (N = 375). Data analysis was conducted using PLS-SEM with SmartPLS software, revealing that: (1) the framework explained 74.7 % and 73.3 % of the variance in intention and behavior; (2) attitude manifested as the most significant determinant of intention, followed by moral norms, subjective norms, perceived behavioral control (PBC), and perceived risk; and (3) behavior was predicted by intention, perceived risk, and PBC. Beyond its novel theoretical contributions, the findings laid a solid foundation for policies promoting RTG adoption: (1) launching awareness campaigns to raise public knowledge of water scarcity and its associated risks; (2) enhancing individuals' sense of control through financial incentives and education programs; and (3) emphasizing the benefits of RTG adoption and the moral duty to protect water resources.