Role of public attitude, knowledge, and trust in shaping the acceptance of recycled wastewater for potable and non-potable uses

Sustainable management of water resources has emerged as a critical concern in the face of growing urbanization, population expansion, and the depletion of freshwater reserves. Within this context, the recycling and reuse of wastewater have garnered substantial attention as viable strategies to address water scarcity and enhance water security (Daigger et al. 2020; Chen et al. 2021). The successful implementation of wastewater recycling schemes, however, hinges on the acceptance and engagement of the public, a crucial determinant that shapes the dynamics of water management policies and practices (Morris et al. 2021).

Numerous studies have emphasized the significance of public acceptance in influencing the effectiveness of recycled wastewater projects (Asano et al. 1996; Duong & Saphores 2015; Chfadi et al. 2021). Public attitudes, knowledge, and behaviors toward recycled wastewater play a pivotal role in shaping the outcomes of such initiatives. A comprehensive understanding of these aspects is crucial for devising tailored strategies to promote the acceptance and adoption of recycled wastewater systems. The support of the public toward recycling of wastewater for non-potable uses is reported to be more than for recycling it for drinking purposes (Hurlimann & Dolnicar 2016). The resistance is not only to recycling wastewater for drinking but also for uses in which the exposure levels are higher. For example, recycling wastewater in swimming pools can be less acceptable to the public than using it for flushing toilets (Dolnicar & Schäfer 2009). The explanation of the difference in attitudes is drawn from the fear of health risk, which sometimes can even be perceived from non-potable uses such as irrigation. For example, Wu et al. (2015) reported health risk as a factor of recycling wastewater for irrigation. This indicates that public attitude toward potable and non-potable uses of recycled wastewater have evolved due to the context of recycling in which it is important to understand those factors that can reduce public resistance toward wastewater recycling. Goodwin et al. (2018) investigated how public attitude is influenced by framing the message to the public in different forms. The study concluded that information related to compliance of treated wastewater has a positive influence on the public attitudes toward recycling.

Another key factor to increase the positive attitude toward the acceptance of recycled wastewater is the realization of the water scarcity. Prins et al. (2022) reported that the studies that investigated the influence of knowledge on the public acceptance of water reuse are carried out in a framework where the participants were given a suite of water resources. However, public attitude can change if there is acceptance of water scarcity as a global challenge. For example, Prins et al. (2022) reported that majority of survey participants in South Africa accepted recycled wastewater as a viable drinking water source in drought situations. Therefore, it is necessary that the importance of information toward the acceptance of recycled wastewater should be investigated in the context of whether the participant perceives challenges of water scarcity. Previous literature highlights the intricate interplay between knowledge, attitudes, and behaviors regarding recycled wastewater (Baghapour et al. 2017; Abdelrahman et al. 2020; Msaki et al. 2022). Studies have emphasized that knowledge of the benefits, risks, and technical processes associated with recycled wastewater directly influences public acceptance (Mu'azu et al. 2020). Moreover, research underscores the critical role of education in enhancing public awareness and understanding of wastewater recycling schemes (Wester et al. 2015). While the literature has addressed the importance of knowledge in shaping attitudes, research gaps remain in understanding the specific areas of knowledge deficit that hinder acceptance as well as the most effective educational strategies to bridge these gaps.

Public attitudes toward the use of recycled wastewater have also been extensively studied. Studies indicate that positive attitudes toward recycled wastewater are closely associated with perceptions of water scarcity, environmental consciousness, and trust in water authorities (Baghapour et al. 2017; Abdelrahman et al. 2020). However, there is limited research that delves into the underlying factors that drive preferences for non-potable versus potable applications of recycled wastewater. Furthermore, studies that explore the potential influence of cultural and religious considerations on these preferences remain scarce.

Behavioral aspects, including willingness to adopt recycled wastewater practices, have garnered attention due to their direct impact on system success. Previous research has examined factors that encourage the adoption of recycled water for non-potable applications, such as gardening and toilet flushing (Adewumi et al. 2014; Duong & Saphores 2015). Yet, a comprehensive assessment of the drivers behind behavioral choices, considering both non-potable and potable applications, remains necessary.

Trust in water authorities is another cornerstone of public acceptance. Previous research has identified the importance of trust in influencing public attitudes toward recycled wastewater (Gul et al. 2021). However, the specific dimensions of trust that contribute to public acceptance and the factors that erode this trust need further exploration.

Despite the extensive literature on public acceptance of recycled wastewater, several research gaps persist. First, there is limited insight into the precise domains of knowledge that contribute to public misunderstanding and skepticism regarding recycled wastewater schemes. Second, while the existing literature acknowledges the importance of cultural and religious considerations in shaping public attitudes, there is a dearth of studies that systematically investigate the impact of religious affiliations on attitudes toward direct-contact applications of recycled wastewater. Furthermore, the link between trust in water authorities and specific factors that bolster or undermine trust has not been extensively explored.

The objective of this study is to understand the factors influencing public acceptance of recycled wastewater. The factors focused in this study that influence public acceptance of recycled wastewater systems are knowledge, attitudes, behaviors, religious considerations, and trust. Quantitative survey-based data were collected in this study regarding these factors to investigate their influence on the public acceptance of recycled wastewater.

Data collection was facilitated through a structured questionnaire. The initial section of the questionnaire focused on demographic information such as age, gender, education, and income. In addition, to quantify responses, Rensis Likert's technique was employed throughout the study, whereby participants were prompted to indicate their agreement or disagreement with statements using a five-point scale (strongly disagree = 1, strongly agree = 5) (Likert 2017). To gauge knowledge and marketing strategies, questions were designed to provide insights into respondents' perspectives.

A pilot test was conducted to assess the clarity of variables, response formats, and question comprehension. A random sample of 60 participants was chosen separate from the main group, and no significant issues were reported. Cronbach's alpha coefficient exceeded 0.75, validating the scale's reliability. The finalized questionnaire, following pilot testing, was administered online using Google Forms. Emails were sent to residents, resulting in 352 responses from the total sample, corresponding to a 91.6% response rate. Among these, 298 participants fully completed the required questions, while 54 responses were incomplete. The survey form settings limited the users to single, and instead of making the survey public, participation in the survey was asked via emails, which made it easier to reduce multiple responses from a single participant. The demographic data of the sample are shown in Table 1.

The authors engaged with community representatives through meetings held at the Remix demonstration wastewater reuse plant in Bluff, Durban. These gatherings, facilitated by the eThekwini Municipality's Department of Water and Sanitation, aimed to involve the public in wastewater reuse discussions. The study's objectives were presented, and participation was solicited. In addition, employees from various organizations and universities in Durban were invited via email, and university students were engaged through their online student groups.

Research involving human participants is contingent upon ethical considerations (Sekaran & Bougie 2016). Data collection respects the confidentiality and privacy of participants, safeguarding their self-esteem and dignity. Participants were informed about the study details, objectives, and approach during introductory sessions and data collection. An information letter, approved by the university, was shared, outlining the study's particulars. Risks associated with participation, anonymity maintenance, and data confidentiality were clarified prior to data collection. The online questionnaire was designed to prevent participants from viewing other respondents' answers, aligning with ethical protocols established by the university's ethical department.

The queries presented to the participants for evaluating their comprehension of water and recycled wastewater, along with the corresponding replies, are summarized in Table 2. Proficiency in knowledge serves as a primary factor influencing the acceptance of recycled wastewater. Analysis of the response rates revealed that a significant majority of participants provided inaccurate answers to most questions, underscoring the necessity to educate the residents about water-related topics. Notably, only 23.8% of participants accurately responded to the inquiry regarding the definition of recycled wastewater. A total of 64% of respondents equated conventional drinking water treatment and rainwater harvesting with recycled water. This observation suggests a crucial need for water authorities to engage the public prior to executing any recycled wastewater initiatives.

Recognizing the scarcity of water emerges as a pivotal motivator in fostering public interest to recycled wastewater. A mere 46.3% of respondents demonstrated awareness about water scarcity in Durban, while 24.5% erroneously believed in the sufficiency of water and 29.2% admitted to lacking knowledge about the city's water scarcity situation. Without a genuine understanding of water scarcity in a region, the adoption of alternative water sources like recycled wastewater might encounter resistance among citizens. Equally noteworthy, fewer than half of the participants (45.3%) correctly identified the largest water consumer in Durban. A smaller percentage (22%) mistakenly attributed this role to industries.

Water scarcity emerges as a key motivational factor in fostering public receptivity to recycled wastewater. The findings highlight that a substantial portion of participants lacked awareness about water scarcity in Durban. This lack of awareness could potentially impede the adoption of recycled wastewater as an alternative water source. Previous studies have also stressed the importance of creating a sense of urgency regarding water scarcity to enhance the acceptability of recycled wastewater (Garcia & Pargament 2015).

Inquiring about the water source in a Drinking Water Treatment Plant (DWTP), 55% of respondents correctly indicated ‘dams’ as the source, whereas 12% incorrectly thought of groundwater as the primary raw water source for a DWTP and 20% expressed uncertainty. The study's knowledge criterion was set at a 75% accuracy rate; however, none of the questions achieved this threshold. Despite 90% of participants possessing an education beyond high school – comprising 41.6% bachelor's degree holders, 33.2% postgraduates, and 14.4% high-school graduates – the failure to meet the 75% accuracy benchmark in knowledge inquiries indicates a pressing need for comprehensive public enlightenment regarding various facets of the water industry in Durban.

The study highlights the crucial role of knowledge and awareness in influencing public acceptance of recycled wastewater. The findings emphasize that participants exhibited a lack of accurate comprehension regarding water-related topics, indicating a need for improved education and public engagement. The data suggest that misconceptions about recycled wastewater, including its definition and differentiation from conventional drinking water treatment and rainwater harvesting, are prevalent among the surveyed participants. This lack of understanding could potentially hinder the successful implementation of recycled wastewater initiatives. Engaging the public prior to launching recycled wastewater projects becomes essential to prevent misconceptions and resistance. This point is supported by previous research that emphasizes the role of effective communication and community involvement in the success of water reuse programs (Smith et al. 2018).

Moreover, the study underscores the significance of accurate knowledge about water sources and consumption patterns in influencing public perceptions. The fact that less than half of the participants correctly identified the largest water consumer in Durban suggests a gap in understanding water usage patterns. This lack of awareness could be addressed through targeted awareness campaigns to inform citizens about water consumption patterns and associated challenges.

The study's finding that education level did not necessarily correlate with accurate knowledge about water-related topics suggests that simply having higher education does not guarantee comprehensive understanding about the wastewater reuse. This observation aligns with the literature, which highlights the need for tailored and accessible educational campaigns to bridge knowledge gaps and promote informed decision-making among diverse segments of the population (Msaki et al. 2022).

However, as the degree of contact with recycled wastewater applications escalated, the percentage of ‘strongly agree’ and ‘agree’ responses diminished. Participants' favorability toward applications followed a hierarchy: toilet flushing > garden irrigation > clothes laundering > dishwashing > cultivating food crops > swimming > drinking. It is worth noting that preferences varied for specific applications within distinct religious groups. For instance, the agreement percentages for using recycled wastewater in swimming and drinking were approximately 42–50% among Christians, 42–46% among Muslims, and 42–46% among adherents of traditional African religion. Collectively, the data underscore that direct-contact applications of recycled wastewater garner less acceptance across all religious communities. This divergence in consideration levels for direct-contact applications suggests the necessity for tailored engagement initiatives based on specific religious communities when contemplating the implementation of recycled wastewater for applications like swimming and drinking.

The consideration of religion as a potential determinant in the acceptance of recycled wastewater originated from the Muslim community, which may view the use of recycled wastewater as conflicting with their religious principles of cleanliness. Initial studies on the role of religion in the acceptance of recycled wastewater were conducted by Wilson & Pfaff (2008) in Durban, South Africa, where a significant population follows the Islamic faith. There are conflicting reports on whether wastewater reuse aligns with Islamic law. For instance, Faruqui et al. (2001) reported that wastewater reuse is not acceptable among Muslim communities, while the Council of leading Islamic scholars in Saudi Arabia declared that recycled wastewater can be used for drinking and other Islamic rituals as long as there are no associated health risks (Wilson & Pfaff 2008). The crux of the religious barrier to wastewater recycling lies in the Islamic ruling that considers urine and feces as impure, requiring their removal before engaging in religious rituals. The Council of Muslim theologians asserts that the Muslim community will be sensitive to recycled wastewater, and religious considerations become critical if there are even slight variations in water quality. Thus, religious factors should be considered and weighted in recycled wastewater projects, especially given the sensitivity of the Muslim community to variations in water quality. The study's results indicated similar acceptance rates across different religious groups, suggesting awareness within the Muslim community in Durban about recycled wastewater. In response to the protest against the eThekwini municipality's 2012 recycling plans, the Water Research Commission in South Africa addressed the concerns through engagement with religious scholars, as reported by Tayob et al. (2015), concluding that there is no fundamental religious reason to reject recycled water in Islam. However, the engagement of various community stakeholders remains crucial during project implementation. The survey results of our study indicated comparable acceptance levels across all religions, contributing valuable insights into the acceptance levels of religions not previously investigated.

Establishing trust in water authorities constitutes a pivotal determinant for fostering the acceptance of recycled wastewater projects, as highlighted by previous research (Gul et al. 2021). To gauge the extent of trust in water authorities within the Durban context and explore plausible explanations for its deficiency, participants were presented with four trust-related statements and four potential factors, as depicted in Table 3. Responses were recorded on a five-point scale, ranging from ‘strongly agree’ to ‘strongly disagree’. Employing regression coefficient analysis, the relationship between trust statements and underlying factors was examined, with the results documented in Table 3. The statistical significance of the regression analysis, as determined through t-test analysis, demonstrated a robust outcome with a significance level of p < 0.05.

Two primary factors, Factor 1 and Factor 4, exhibited positive regression coefficients exceeding 0.5 in connection with all four trust statements. This pattern indicates that participants' mistrust could stem from perceived shortcomings in the competence of local municipalities to manage water supply and a perceived failure to act in alignment with public interests. Factor 2, encompassing the provision of necessary water-related information, displayed a significant correlation (Pearson coefficient of 0.52) with trust statement 4, which pertained to trust in the municipality's ability to deliver high-quality water. This highlights the importance of transparent communication from local municipalities to update citizens about water quality, a practice that holds the potential to elevate trust levels.

On the contrary, Factor 3, representing the municipality's responsiveness to citizen concerns, exhibited a negative correlation with all trust statements (as detailed in Table 3). This observation underscores the significance of promptly addressing citizens' apprehensions regarding water supply. Any deficiencies in this area could have adverse consequences, eroding trust among citizens and potentially impeding the successful execution of wastewater recycling initiatives.

In sum, the study reinforces the critical role of trust in water authorities in driving the acceptance of recycled wastewater schemes. Findings indicate that enhancing trust involves addressing concerns about water management competence, aligning actions with public interests, providing transparent water quality information, and promptly responding to citizen concerns. These insights, resonating with prior literature, underscore the need for proactive measures in ensuring successful implementation of recycled wastewater projects.

In order to enhance public receptivity toward recycled water, the development of effective strategies is imperative. One approach with potential to drive acceptance of recycled wastewater for potable purposes is offering discounted water supply connections. This incentive holds the promise of motivating the public to embrace recycled water. Survey participants considered a discounted water bill as a pivotal condition for endorsing recycled wastewater (as indicated in Table 4). Notably, 44% of participants favored the idea of a discounted water bill, while 45% remained open to the possibility (‘maybe’ option). Additional preferences for benefits were also solicited from participants, revealing that 46.6% viewed discounts on municipality services as a viable alternative to reduced water bills (Table 4). These results highlight the potential of offering discounted water supply connections as an incentive to drive the acceptance of recycled wastewater for potable purposes. This approach aligns with behavioral economics, where providing tangible benefits can influence decision-making (Thaler & Sunstein 2009). The findings suggest that a discounted water bill is a key factor influencing participants' endorsement of recycled wastewater. Investigating further into marketing approaches, participants were questioned about their response if no tangible benefits were attached to the recycled wastewater scheme. A significant 61% of participants highlighted transparency in services and effective customer care from water authorities as prerequisites for accepting recycled wastewater without direct incentives. This reveals the importance of intangible factors in driving acceptance when direct incentives are not provided. The emphasis on transparency in services and effective customer care as prerequisites for accepting recycled wastewater highlights the significance of trust and communication in building public confidence in water reuse programs.

Tariffs are used as a tool in managing drinking water demand. Marketers use tariffs to change the behavior of consumers. The consumer decides whether to use less or pay more as tariffs increase. According to the study conducted by Adewumi et al. (2014), if the tariff for wastewater reuse is lower than the tariff for drinking water, 71% were willing to accept recycled wastewater. This is also based on the ‘nudge theory’ proposed by Thaler & Sunstein (2009) that suggested the implementation of policies can be successful if there are incentives, which can change the behavior of an induvial. A discounted water bill may be considered an incentive influencing participants' endorsement of recycled wastewater.

To achieve transparency and superior customer care favored by participants, a range of media platforms could be harnessed. The study revealed that participants identified social media as effective channels for both information dissemination and customer services. Specifically, 48% of participants favored Facebook and 44% expressed preference for WhatsApp. In contrast, platforms such as Twitter, Instagram, and Snapchat garnered preference from less than 5% of participants. This underscores the need for local municipalities to transition toward contemporary media platforms when sharing water-related information and catering to customer needs. The participants' platform preferences were congruent with the accessibility and widespread adoption of Facebook and WhatsApp, suggesting that aligning with these platforms could yield optimal results.

The Internet, social media, and television are the main sources of information (Abdelrahman et al. 2020). The most dominant method of informing the community about recycled wastewater reuse is social media (Buyukkamaci & Alkan 2013). Akpan et al. (2020) studied that most respondents (85.4%) get information regarding environmental issues from the Internet sources. Online sources (Internet 61%) followed by social media (38%) were found as the leading information sources (Chfadi et al. 2021).

The findings from this study suggested the possible aspects for exploration in the domain of recycled wastewater acceptance and utilization. First, future research could focus into the design and implementation of targeted educational interventions aimed at bridging the identified knowledge gap among public about wastewater recycling. In addition, the efficacy of educational campaigns in enhancing public understanding of wastewater treatment processes and safety measures would be instrumental in fostering confidence and acceptance of recycled wastewater. Future investigations should also focus into assessing how factors such as climate change awareness and sustainable water management practices influence public attitude toward recycling of wastewater. This could provide insights about the factors that can shape positive attitudes toward recycled wastewater, guiding the development of effective attitude-shaping initiatives. Further studies should also focus on the dynamics of trust-building in the context of recycled wastewater initiatives. Understanding the specific elements and communication strategies that contribute to trust formation in municipal water services could guide policymakers and project managers in fostering community trust, thereby facilitating the successful implementation of recycled wastewater projects.

The findings of this study focused on key aspects regarding the public's knowledge, attitudes, and behaviors toward recycled wastewater and its applications. Despite higher participant education among survey participants, knowledge deficiency about wastewater reuse may persist, suggesting that knowledge about wastewater reuse is important that may create a sense of confidence in public that the wastewater has been treated enough to produce potable water. The positive attitude can influence the acceptance of recycled wastewater. The survey results indicated that the feeling of water scarcity can have a positive effect on the attitude toward the importance of recycled wastewater and improve its public acceptance. Religious affiliations are important to consider and tailored engagement strategies that consider religious beliefs should be adopted in planning recycled water projects. The study indicated that trust in municipal services also influence acceptance of recycled wastewater. The survey results indicate that trust can be fostered through transparent communication, addressing competence concerns, and prompt response to citizen inquiries. The survey results also indicate more preference of contemporary media platforms like Facebook and WhatsApp for information dissemination and customer services in scenarios using recycled wastewater as a source of water.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.