Zunehmende Wasserknappheit und rasches Bevölkerungswachstum in Städten machen es erforderlich, den Trinkwasserverbrauch zu senken und alternative Wege der Abwasserbehandlung zu entwickeln, zum Beispiel durch dezentrale Wasser- und Abwassersysteme (so genannte Wings-Systeme). Um die Nutzung von Wings-Systemen zu fördern, haben die Kommunalverwaltungen von Bangalore und San Francisco Gesetze erlassen, die die Einführung von Wings-Systemen für einen Teil der Bevölkerung vorschreiben, während für den restlichen Teil der Bevölkerung ein zentrales System beibehalten wird. Eine solche Politik kann die Nutzung von Wings-Systemen erfolgreich erhöhen, kann aber gleichzeitig auch die gerechte Verteilung von Kosten und Nutzen von Wasser- und Abwassersystemen in der Gesellschaft gefährden. Beispielsweise werden die Wings-Systeme in beiden Städten nicht vom Wasserversorgungsunternehmen, sondern vom Gebäudeverwalter verwaltet und gewartet, was zu Ungleichheiten bei der Wasserqualität zwischen den Nutzern und dem Rest der Gesellschaft führen könnte. Darüber hinaus sind die Installation und Wartung von Wings-Systemen mit erheblichen Kosten verbunden, die die Nutzer finanziell belasten. Andererseits sind in San Francisco Projekte für erschwinglichen Wohnraum von diesem Gesetz ausgenommen, was die unbeabsichtigte Folge haben kann, dass einkommensschwache Bevölkerungsgruppen von der erhöhten Wassersicherheit, die Wings-Systeme mit sich bringen können, ausgeschlossen werden. Dieser potentielle Mangel an Verteilungsgerechtigkeit könnte die öffentliche Akzeptanz der Maßnahmen und der entsprechenden Wings-Systeme beeinträchtigen. Daher ist ein besseres Verständnis darüber notwendig, wie die Verteilungsgerechtigkeit von Wings-Systemen und Gesetzen zur verpflichtenden Anschaffung von der Öffentlichkeit wahrgenommen wird und wie dies die Akzeptanz der Gesetze und der Wings-Systeme beeinflusst.
Das Fair Wings-Projekt
Das Fair Wings-Projekt zielt auf ein besseres Verständnis davon ab, wie die Bevölkerung Bangalores und San Franciscos die Verteilungsgerechtigkeit dieser Gesetze wahrnimmt. Anhand von qualitativen Interviews und Online-Befragungen werden die wahrgenommenen Kosten, Risiken und Vorteile der Gesetze und der jeweiligen Systeme sowie ihre wahrgenommene Verteilung in der Gesellschaft untersucht. Zudem wird die Rolle der wahrgenommenen Verteilungsgerechtigkeit für die öffentliche Akzeptanz dieser Systeme und der jeweiligen politischen Maßnahmen untersucht.
Die im Rahmen des Fair Wings-Projekts gewonnenen Erkenntnisse können dazu beitragen, künftige politische Maßnahmen so zu gestalten, dass die Fairness bei der Gestaltung und Umsetzung städtischer Wassersysteme gefördert wird, und sich die Akzeptanz der Gesetze in der Bevölkerung erhöht.
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Mandated on-site wastewater reuse in San Francisco: the role of distributive fairness for policy acceptance
With increasing water scarcity worldwide, policies regulating wastewater reuse are becoming increasingly important. In San Francisco, on-site wastewater treatment and reuse is mandatory for large residential buildings, while other buildings continue using centralised systems without reuse. This disparity may affect perceived fairness and policy acceptance. In an online survey (N = 176), policy acceptance, perceived fairness, and perceptions of a range of policy implications were assessed for five societal groups and one entity: residents and owners of buildings with mandated on-site systems, San Francisco’s population, low-income residents, future generations, and the environment. Regression analyses showed that both positive and negative policy implications explained perceived fairness. Policy acceptance was explained by perceived fairness for future generations, San Francisco’s population, and building owners, but not other groups or entities. Results suggest that collective fairness considerations and impacts on most-affected groups are key to policy acceptance, indicating policymakers should consider implications across different societal groups when designing water reuse policies.
Kollmann, J.; Harris-Lovett, S.; Nelson, K. L.; Contzen, N. (2025) Mandated on-site wastewater reuse in San Francisco: the role of distributive fairness for policy acceptance, npj Urban Sustainability, 5(1), 93 (10 pp.), doi:10.1038/s42949-025-00283-z, Institutional Repository
Perceived distributive fairness and public acceptance of a policy mandating on-site wastewater treatment and reuse
Throughout the world, climate change, rapid population growth, and urbanisation raise the need for reducing freshwater consumption. One solution are on-site systems that treat wastewater for non-potable reuse near its source of generation, for example within a building. Policies mandating their installation can effectively increase installation rates and have been implemented in several cities. Yet, such policies have the potential to impair distributive fairness in society and therefore also policy acceptance, because usually they cover only part of the population, which then has to carry most costs and risks. On the example of Bengaluru, India, where such a policy exists, this online study (N = 350) analysed whether policy acceptance can be explained by the perceived policy outcome for different groups of society (i.e. the distribution of the policy's costs, risks, and benefits among these groups), and whether this relation is mediated by perceived fairness. We further investigated whether these relations differed between participants covered and those not covered by the policy, since being personally affected may influence perceptions. Specifically, the outcomes for the following six groups were included: 1) participants themselves, 2) people covered by the policy, 3) people with a low income who are covered by the policy, 4) people vulnerable to water insecurity who are covered by the policy, 5) all inhabitants of Bengaluru taken together, and 6) the environment and future generations. A moderated mediation analysis showed that higher acceptance of the policy was explained by a higher perceived fairness, which, in turn, was explained by a better perceived outcome of the policy for different groups of society. Covered and non-covered participants differed with regard to which groups of society they considered for evaluating fairness. While a better perceived outcome for residents covered by the policy (compared with the outcome for those not covered) explained perceived fairness among all participants, it explained acceptance only among participants not covered by the policy. Further, and only among participants covered by the policy, perceived fairness was additionally explained by better perceived outcomes for the environment and future generations, which also explained higher acceptance among covered participants. It is discussed whether in the specific context, collective considerations may be more relevant than self-centred considerations to the perception of fairness and acceptance of the policy.
Kollmann, J.; Nath, S.; Singh, S.; Balasubramanian, S.; Scheidegger, A.; Contzen, N. (2024) Perceived distributive fairness and public acceptance of a policy mandating on-site wastewater treatment and reuse, Journal of Environmental Psychology, 96, 102292 (11 pp.), doi:10.1016/j.jenvp.2024.102292, Institutional Repository
The importance of user acceptance, support, and behaviour change for the implementation of decentralized water technologies
Decentralized water treatment technologies could help in addressing global key water issues. Their successful implementation, however, depends on users' positive valuation and, depending on the technology, 'passive' use (rooted in acceptance), 'engaged' use (rooted in support) or 'active' use (rooted in behaviour change). Although users' valuation of a technology is contingent on its characteristics, positive valuation and use usually also require supporting promotion activities. Here we review the literature on psychological determinants of use as well as change techniques to promote use, and propose a user-focused theory of change to guide promotions. Our review highlights a lack of (conclusive) evidence on both psychological determinants and effective change techniques. We call on environmental and health psychologists to intensify their research on 'passive', 'engaged' and 'active' use of decentralized water treatment technologies and encourage engineers, practitioners and psychologists to intensify collaboration to ensure that technologies, implementation and promotions are optimally integrated.
Contzen, N.; Kollmann, J.; Mosler, H.-J. (2023) The importance of user acceptance, support, and behaviour change for the implementation of decentralized water technologies, Nature Water, 1, 138-150, doi:10.1038/s44221-022-00015-y, Institutional Repository
Acceptance of on-site wastewater treatment and reuse in Bengaluru, India: the role of perceived costs, risks, and benefits
In dealing with water pollution and freshwater scarcity, on-site treatment and reuse of domestic wastewater has shown to be a promising solution. To increase on-site wastewater treatment and reuse, some cities, among them Bengaluru in India, have mandated the installation and use of the necessary technology in certain building types. However, even with a mandate, a successful and sustainable implementation of the technology, including reliable operation, monitoring, and maintenance, depends on the acceptance (i.e. positive valuation) of the technology and its use by the (prospective) users. Literature on technology acceptance indicates perceived costs, risks, and benefits of the respective technology as key predictors of acceptance. Therefore, the present online study assessed this relationship for on-site systems in Bengaluru. The relation was analysed separately for mandated users of on-site systems (N = 103) and current non-users (i.e. potential prospective users, should the mandate be expanded; N = 232), as the perceptions might differ between the two groups, due to the personal experience with the technology among users. The results show that for mandated users and non-users, acceptance of on-site systems is explained by perceived benefits only, namely a positive image of users, environmental benefits, and, only for non-users, also financial benefits for the city. The findings suggest that interventions aimed at promoting on-site systems should include emphasis on the benefits of on-site systems. Whenever possible, interventions should be tailored to the target group's individual cost, risk, and benefit perception.
Kollmann, J.; Nath, S.; Singh, S.; Balasubramanian, S.; Reynaert, E.; Morgenroth, E.; Contzen, N. (2023) Acceptance of on-site wastewater treatment and reuse in Bengaluru, India: the role of perceived costs, risks, and benefits, Science of the Total Environment, 895, 165042 (11 pp.), doi:10.1016/j.scitotenv.2023.165042, Institutional Repository
Outputs
Perceived distributive fairness of alternative systems
Despite the many benefits that alternative, i.e. novel and decentralized, water and sanitation systems bring to society, adoption rates are low. Therefore, a few governments have issued policies that mandate the adoption of alternative systems for a part of the population, while keeping the centralized system for the rest of the population. Read more
Fair or Unfair? Mandatory Decentralised Sewage Treatment in Bangalore
Bangalore is one of the fastest growing cities worldwide. This challenges the population’s water supply and pushes the central wastewater system to its limits, leading to environmental pollution and resource degradation. Read more
Fair Wings Poster [3 MB]