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ArticleMarch 26, 2024

Reinforcing Feedbacks for Sustainable Implementation of Rural Drinking-Water Treatment Technology
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Merel Laauwen*
Merel Laauwen
School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, U.K.
*Email: [email protected]
More by Merel Laauwen
https://orcid.org/0009-0009-5245-5959
Saskia Nowicki*
Saskia Nowicki
School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, U.K.
*Email: [email protected]
More by Saskia Nowicki
https://orcid.org/0000-0001-9011-6901

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ACS ES&T Water

Cite this: ACS EST Water 2024, 4, 4, 1763–1774

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https://doi.org/10.1021/acsestwater.3c00779

Published March 26, 2024

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Abstract

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Progress toward universal access to safe drinking water depends on rural water service delivery models that incorporate water safety management. Water supplies of all types have high rates of fecal contamination unless water safety risks are actively managed through water source protection, treatment, distribution, and storage. Recognizing the role of treatment within this broader risk-based framework, this study focuses on the implementation of passive chlorination and ultraviolet (UV) disinfection technologies in rural settings. These technologies can reduce the health risk from microbiological contaminants in drinking water; however, technology-focused treatment interventions have had limited sustainability in rural settings. This study examines the requirements for sustainable implementation of rural water treatment through qualitative content analysis of 26 key informant interviews, representing passive chlorination and UV disinfection projects in rural areas in South America, Africa, and Asia. The analysis is aligned with the RE-AIM framework and delivers insight into 18 principal enablers and barriers to rural water treatment sustainability. Analysis of the interrelationships among these factors identifies leverage points and encourages fit-for-purpose intervention design reinforced by collaboration between facilitating actors through hybrid service delivery models. Further work should prioritize health impact evidence, water quality reporting guidance, and technological capabilities that optimize trade-offs in fit-for-purpose treatment design.

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Synopsis

Improvements in rural water safety management are needed to achieve universal access to safe drinking water. This study identifies leverage points to sustain rural water treatment implementation.

1. Introduction

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Inadequate access to safe drinking water leads to serious health impacts and deepens social and economic inequalities. (1,2) Access to safe drinking-water is essential to human health and it is a basic human right. (3,4) However, in 2020, one in four people lacked access to safely managed drinking water, and eight out of ten people who lacked even basic drinking water services were living in rural areas. (5) Rural coverage of safely managed water services is lower than urban coverage in all of the United Nations Sustainable Development Goals (SDGs) country grouping regions. (5) Microbial contaminants from human or animal feces are the primary threat to drinking water safety. (3) Piped water supplies, boreholes, rainwater collection systems, and protected wells and springs (“improved” water supply infrastructure as defined for the Millennium Development Goals) have high rates of fecal contamination unless water safety risks are actively managed. (6) Human and animal feces can spread pathogenic bacteria, viruses, protozoa, and helminths; therefore, to ensure the safety of drinking water, a series of barriers to fecal contamination should be implemented. (3) The World Health Organization (WHO) recommends a risk-based approach that considers the need for water source protection, appropriate selection of water treatment technologies, and sound management of water distribution. (3)

Within the broader risk-based framing of water safety management, technological innovations may offer promising avenues to improve water safety. However, across the water, sanitation and hygiene (WASH) sector, a growing body of evidence shows that the expected improvements in health outcomes from technology-focused interventions are often elusive. (7−17) This is due to the complexity of the links between WASH and health and also due to challenges of sustaining adherence to interventions. (18,19) Here we focus specifically on drinking water treatment interventions. To increase drinking water safety in rural areas, decentralized water treatment approaches generally focus on either the household level [point-of-use, (PoU)] or the water-supply level [prior to the point-of-collection, (PoC)].

Household-level water treatment, including the use of filters, solar disinfection, boiling, or chlorination, has been widely promoted for years. (20) While technologically effective, high adherence to PoU water treatment is required for positive health impacts to be realized. (21,22) Yet, household-level water treatment methods have low uptake and sustainability in many contexts. (17,21) Focusing on the household as the locus of responsibility for ensuring safe drinking water places an additional burden on individuals, often women, who may be limited in their ability to take-on this burden by poverty, gender norms, and the need to balance their effort across multiple priorities. (2,23−25)

Transformative advancements are needed in the rural water sector to develop service delivery models that shift the burden of water treatment away from households. (23) Applying systems thinking to examine the challenges of safe water service delivery provides insight for the design of such models. (26,27) In this study, we use an implementation science framework to explore a complex adaptive system (CAS) in which supply level rural water treatment interventions are embedded. We focus specifically on the implementation of passive chlorination and ultraviolet-C light-emitting diode (UV–C LED) disinfection. These two disinfection approaches were chosen due to their widespread uptake and technological advancements in recent years. (28−32) Both approaches reduce health risk from microbiological contaminants in drinking water; both require ongoing maintenance by a local party; both are installed in-line so that they act on water flowing through a pipe, tap, or pump, either at the PoC or upstream; (33−35) and both may require pretreatment filtration steps to be implemented if water has high turbidity (which reduces the disinfection efficiency for both UV and chlorine (36−38)). Beyond these commonalities, the two approaches have several important differences.

Passive chlorination is a form of water treatment that continuously and automatically doses chlorine, while operating without electricity (although electricity is intermittently required for on-site chlorine generation if adequate chlorine supply chains are not accessible). There are commercially available passive chlorination devices (e.g., Aquatabs Flo, Aquatabs Inline), or basic designs can be constructed from common materials that are used for building and maintaining small piped water schemes (e.g., AkvoTur, T-shaped chlorinator, pot chlorinator). Passive chlorination technologies vary widely, (39) and factors that differentiate chlorine technologies include the form of chlorine used, cost, maintenance requirements, and compatibility with water supply infrastructure parameters like pipe sizes and flow rates. (39−41) The mechanisms and advantages of different types of passive chlorinators were explored by Dössegger et al. (34) Passive chlorinators are operated at the water supply level, but they can provide ongoing protection at the household level if dosing is sufficient to have adequate residual chlorine concentration. (34,39,42) This is an important advantage of passive chlorination over UV-based disinfection, which provides no residual protection. Using chlorine for disinfection also has several disadvantages. Chlorine has varying levels of effectiveness against different microorganisms; (43) it can be ineffective against hardy protozoa like cryptosporidium (44) or some viruses. (45) Implementation challenges can arise if water users object to chlorination because of changes in water taste/odor, for cultural or religious reasons, (46) or due to concerns about disinfection byproducts (DBPs) that form when chlorine reacts with organic matter. (47)

Ultraviolet (UV) irradiation is capable of inactivating a broad spectrum of microorganisms without the use of chemical consumables (therefore, without taste/odor or DBP concerns). With UV, the mechanism of disinfection is agnostic to the taxa of the microorganism. (32) However, microorganisms do have varying susceptibilities to UV irradiation: for example, cryptosporidium is easily inactivated but viruses are more difficult to inactivate. (48,49) With treatment at high UV fluences, microorganisms are inactivated through the absorption of UV photons by proteins in the outer cell membranes, leading to disruption and consequent death of the cell. (50) At lower fluences, microorganisms can no longer cause infection as the ability to replicate is disrupted. (50) UV–C LED technologies are advancing at an unprecedented speed. Lui et al. found, in 2016, that commercially available UV–C LEDs were already technically effective in inactivating Escherichia coli and Enterococcus faecalis, and offered advantages in terms of speed and energy demand. (28) Simons et al. calculated a 39% compound annual growth rate in commercial single-chip LED output power between 2005 and 2022. (51) While conventional mercury-based bulbs require a warm-up time and thus must be in continual operation, LEDs may remain in low-power standby mode and only need to be engaged on-demand. (51) The rapid advancement of LED efficiencies suggests that UV–C LED disinfection can open-up opportunities for more affordable, effective water treatment. (51) However, the UV–C LED approach also has important disadvantages to consider. Unlike passive chlorination, UV-based disinfection relies on energy access, which is not reliable or affordable in many resource-constrained rural settings. The advancement of solar power technologies may alleviate this issue, (28,29) but UV–C LED disinfection is still complicated compared to passive chlorination, particularly with regards to accessing specialized spare-parts. (28) For example, supply chain issues related to microchip acquisition persist globally due to the dependence on several countries to coordinate materials and manufacturing. (52)

Current research priorities for UV-based water disinfection center on improving inactivation levels of microbial contaminants (53−55) and developing technologies that are compatible with decentralized energy supply. (28) However, implementation of UV–C LEDs in full-scale centralized or decentralized water treatment systems remains poorly characterized and understood. (56) For passive chlorination, a 2022 critical review (30) outlined key components needed for scalability: electricity access for on-site chlorine generation, (53,57) residual disinfection, consistent water supply, (58) low user burden, (59) local manufacturing capacity, and affordable cost of technology and operations and maintenance (O&M). The review identified four research priorities including (i) strengthening supply chains, (ii) context-specific financial sustainability, (iii) remote monitoring and sensors, and (iv) handpump-compatible passive chlorinators. (30)

This study aligns with the research priorities for both UV–C LED and passive chlorination treatment approaches by using an implementation science framework. This framework guides our exploration of the barriers and facilitators for sustainable implementation of supply level water treatment in rural, resource-constrained settings. It enables development of a rich comparison of the implementation environment for passive chlorination compared to UV–C LED technologies.

2. Methods

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Implementation science focuses on the gap between efficacy studies and real-world interventions at scale. (60,61) Research examining the factors and processes that make WASH or other environmental health interventions successful is included within this scope. (27,62) Intervention implementation studies use varying and overlapping theoretical, analytical and experimental methods that also draw on the aligned fields of translational research and systems science, (26,61,63−65) with some key successes in improved health outcomes. (66−68) In this study, we use an implementation science conceptual framework and system mapping method to guide and analyze key informant interviews. Our approach is an application of systems thinking, where “system” refers to the components and dynamic interactions of local context, management, supply chains, and other factors that collectively constitute the CAS of rural water supply. (26) Thus, this study aims to understand the complexity of water treatment interventions beyond technical components. To avoid confusion, physical water supply and treatment “systems” are referred to as “technologies” or “infrastructure”.

2.1. An Implementation Science Framing

The RE-AIM framework evaluates public health interventions according to five key dimensions: Reach, Effectiveness, Adoption, Implementation, and Maintenance/Sustainability, with long-term sustainability and health equity concerns having been added recently (69−74) (Figure 1). The Reach dimension directs focus to the intervention target population and factors, such as user/customer profiles and collaboration between actors. It is most relevant during the planning stages of an intervention and is heavily influenced by costs, resources, and capacity considerations. The Effectiveness dimension includes consideration of factors that impact how well an intervention achieves the desired outcomes when implemented according to guidelines and protocols in the real world (as opposed to how efficacious it may be under controlled circumstances). This is a priority during the early stages of implementing an intervention. The Adoption dimension is about communication with the actors that are the intended adopters of the intervention and working to understand their perception of the intervention. It is heavily influenced by context and culture and dominates focus in the midimplementation phase. The Implementation dimension evaluates the extent to which the intervention is carried forward as intended, prompting considerations of financing, person-power, and roles and responsibilities. Within the framework, it is positioned for primary focus during the late implementation stage and is influenced by context, culture, and healthy equity considerations. Finally, the maintenance/sustainability dimension prompts consideration of long-term monitoring, stability of implementation models, climate resilience, and supply chains. This sustainment phase of an intervention is oriented toward advancing health equity, where all members of a population have fair opportunity for good health and well-being through a reduction of health risks that negatively impact marginalized groups and through provision of protective measures and care that is accessible to all. (74,75) All five dimensions are intended to be explored within a broader and continuous focus on sustainability through all stages of an intervention, from planning to sustainment.

Figure 1. Updated RE-AIM Framework as presented by Shelton, Chambers and Glasgow 2020 [CC BY]. (74)

The initial development of the RE-AIM framework sought to improve public health interventions by promoting more efficient use of resources and by aligning different stages of development. (73) More than 20 years later, the framework was adapted to include the longer-term perspective, (74) which reflects a growing recognition of the dynamic, complex, systemic nature of public health interventions. Thus, RE-AIM provides a useful framing for our investigation of rural water treatment by positioning treatment technologies within the complex systems that they aim to change. (74) RE-AIM is also preferred because it substantially prioritizes sustainability and health equity, which receive more limited consideration in many other implementation science frameworks and theories. (69−71,76)

2.2. Key Informant Interviews

Semistructured interviews were conducted in June and July 2022 with key informants who work in academia, NGOs, commercial companies, research institutes, public health institutes, or a combination (Table 1). An interview guide was developed based on the components of the RE-AIM framework and interviewees were asked about general facilitators and barriers to implementation, water user perceptions, communication, management and financing structures, supply chains, health impacts, long-term resilience, and key future improvements. Interviews were conducted via Zoom and lasted between 26 and 105 min.

Table 1. Summary of Key Informant Characteristics

actor category	technology		role		country of organization		country of operations
	passive chlorination	UV–C LED disinfection	operational	managerial	low- or middle- income country	high income country	low- or middle- income country	high income country
academia	5	6	0	11	0	11	8	2
academia and NGO involvement	2	1	1	2	0	3	4	0
NGO	6	1	4	3	3	4	9	0
research institute	3	0	0	3	0	3	5	0
public health institute	2	0	0	2	0	2	1	1
total	18	8	5	21	3	23	27	3

The main criteria for inclusion as a key informant was involvement in at least one project to implement passive chlorination or UV–C LED water disinfection technologies in rural areas of low- or lower-middle-income countries. Academic and research institute actors were included because a large portion of the ongoing work on passive chlorination and UV–C LED technology implementation is experimental; thus, researchers are heavily involved. Eighteen key informants were experts in passive chlorination and 8 in UV–C LED technologies. They work on treatment implementation projects that deal with a range of technology maturity levels including established/mass manufactured devices, “build-your-own” devices, and novel innovative design development. Three projects were identified initially through the authors’ existing networks from previous research on rural drinking water safety in Kenya, Nepal, Guatemala, Honduras, and Nicaragua. An additional 13 projects from rural areas in Australia, Bangladesh, Japan, Philippines, Vietnam, Haiti, United States, Uganda, Malawi, Tanzania, and Ghana were identified through snowball sampling. (77) In 7 cases, multiple key informants from the same project were interviewed to comprehensively cover activities pertaining to all five dimensions of the RE-AIM framework. Snowballing continued until new thematic content plateaued (78) and referrals for key informants from different projects stalled, with a total of 26 interviews completed.

The broad geographical scope of this study was suitable for the exploratory nature of the research, particularly due to the narrow technological scope. Of the 26 key informants, 17 work at either an academic institution, have both academic and NGO roles, or work at a research institute. These key informants provide a broad perspective of the systems analyzed in this study because they have consolidated sets of experiences through multiple case studies over many years. This broad perspective is valuable for developing systems maps that are more generalizable across different contexts. However, the use of this broad perspective has several important limitations. First, the perspective of implementers with a more direct and highly context-specific implementation experience is underrepresented. Second, research on passive chlorination and UV–C LED technologies has predominantly been led by institutions in high-income countries, so 88% of the key informants are based in high-income countries despite 90% of the water treatment implementation projects that they spoke about being in low- or middle-income countries. Third, the key informants of this study are at least one degree removed from water users, limiting a comprehensive understanding of the entire network of actors involved in water treatment implementation. In future work, a more granular geographic focus with better representation of implementers and potentially water users would allow for more detailed, context-specific mapping of decentralized water treatment implementation.

The University of Oxford Central University Research Ethics Committee (CUREC) approved the research based on the study’s CUREC application (SOGE1A2021–031).

2.3. Content Analysis and Systems Mapping

Audio recordings of the interviews were transcribed verbatim using Trint transcription software, followed by manual correction. The transcripts were then analyzed following the qualitative content analysis method described by Drisko and Maschi, 2015. (79) All transcripts were initially coded to a node framework structured according to the five dimensions of the RE-AIM framework: Reach, Effectiveness, Adoption, Implementation, and Maintenance/Sustainability, which were further separated into subnodes to classify facilitators and barriers to successful implementation of passive chlorination and UV–C LED water treatment technologies. In this way, the five dimensions of the framework were used as the foundation for the “open coding” component of the qualitative content analysis. (79) To synthesize the coding results, a conceptual map was produced to represent the breadth of implementation factors organized into categories corresponding to the RE-AIM framework (Supporting Information Figure 1). These factors were summarized into principal topics that encompass enablers or barriers to sustainable rural water treatment (Table 2). To give a sense of the extent to which topics were explored in the interviews, Table 2 reports (i) the number of interviews in which the topic was discussed and (ii) the percentage of those interviews in which the topic was discussed, i.e., the coding coverage expressed as average and range.

Table 2. Summary of Principal Enablers of and Barriers to Sustaining Rural Water Treatment, Identified From 26 Key Informant Interviews

topic	description	quote(s)	interviews	% coding coverage
REACH
R1 user/customer base (enabler)	The customers of UV and passive chlorination technologies range from NGOs, private companies, and local governments to individual homeowners. In most settings, these technologies are installed to serve small communities, schools, or healthcare facilities. The profile and proportion of populations reached (and potentially reached) by interventions was identified as a determinant of their scope for impact and whether they can advance health equity, and was mentioned explicitly as an enabler in a subset of the interviews.	“The customers could be NGOs that are partnering with healthcare facilities or the local government that is providing water at schools and other institutions. It could be individual homeowners. It could be private. The device itself could work in a lot of settings. So, I think it’s going to be kind of a wide range of customers.” (Cl_04)	5	1.5 (0.9–2.3)
R2 collaboration between facilitating actors (enabler)	Various actors, including manufacturing companies, research organizations, service providers, NGOs, government, regulators, donors, and investors have actual or potential roles in facilitating rural water treatment implementation. Collaboration and information sharing between these facilitating actors was deemed as important or essential in many interviews: the nature of this collaboration influences the profile and proportion of populations that are reached by interventions, and has impacts on technology development and the sustainability of financing.	“I feel like there’s a couple of bad eggs that like are not about collaboration. It’s all about touting their best design and their best approach. But a lot of us on the other side, we’re connected··· You know, we love information, we have a lot to share, but we learn as well.” (Cl_18)	19	3.4 (0.4–9.7)
EFFECTIVENESS
E1 dosing/fluence calibration and reliability (enabler)	For both UV disinfection and chlorination, correct fluence/dosing is a core performance issue. The capacity to adapt to variability in water flow rates and water quality is important in most rural systems, which are often characterized by intermittent flow and minimal or no pretreatment stages before disinfection. Dosing/fluence must be designed to balance efficient use of resources, organoleptic issues, disinfection sufficiency, and recontamination risks.	“I think one of the biggest barriers we have is the difficulty of ensuring a consistent chlorine dose with inconsistent flows of water.” (Cl_05)	22	5.2 (0.6–17.1)
E2 fit-for-purpose technology design (enabler)	In the past decade, many new decentralised water treatment technology options have been developed. These are intended for use in a wide range of settings. There are trade-offs to consider when selecting between a chlorination or UV treatment approach, when selecting particular design options within these approaches, and when deciding whether and how to include source protection and predisinfection steps.	“You can’t say inline chlorinator A is going to be the same as B, they could be completely different products. So, I think understanding products that provide more consistent quality dose is really crucial. . . Inline chlorinators have a place. . . but that place is not the entire world.” (Cl_05)	24	9.4 (1.0–24.1)
E3 disinfection byproduct (DBP) risk (barrier)	DBPs present a potential health risk and associated acceptability risk for chlorination interventions. The evidence of DBP health impacts is inconclusive, but there are also regulatory requirements and water user acceptability factors to consider. Variability in the concentration of organic matter in pretreatment water makes DBP management more complex.	“It should be really clear to mention that the risk of these byproducts, as compared to the risk of infectious disease, is just so much lower that we shouldn’t avoid chlorine for fear of exposure to various chemicals.” (Cl_07)	3	2.0 (0.8–2.9)
E4 technology development (enabler)	Key areas of decentralized water treatment technology development relate to energy consumption and material characteristics such as recyclability, lifetime, and availability. For example, the cost of UV–C LED bulbs has reduced 100-fold in the past decade, driving rapid development of UV–C LED technologies, which have become more electrically efficient, more powerful, cheaper, longer-lasting, more compact, and easier to operate. Water quality sensor technology is also advancing with important implications for monitoring capabilities.	“LEDs have sparked interest, and I think that’s spurred more interest in implementation and also advances in solar power as an option for powering UV systems.” (UV_04)	17	5.8 (1.1–20.7)
ADOPTION
A1 water user acceptance of water treatment (enabler)	Acceptance of treatment interventions is influenced by education, prior experience, local norms, information dissemination and other factors. Water users that are closer to the point of chlorination receive water with higher chlorine residual concentration and may have more taste/odor complaints. Besides organoleptic aspects, knowledge about disinfection varies and myths, suspicions, and religious positioning can impact acceptance. Labour and cost are also key factors: treatment implemented within the water supply prior to point of collection has advantages over household-level treatment because of economies of scale and no household labor requirement.	“If people are unhappy with you putting the chlorine, you know, forcing them to get chlorine, they can switch sources. They can go to a very polluted source because they dislike your chlorine. And myths about chlorine are very prevalent in rural areas. In Uganda, for example, it is common to believe that it leads to fertility issues.” (Cl_11)	25	6.5 (0.3–12.4)
A2 communication with water users (enabler)	Communication with water users is perceived to be beneficial for water treatment interventions. Differences in how engagement is done and what is communicated are important. Water users must know that chlorination or UV disinfection is occurring, and there must be space for them to ask questions or express concerns. There are mixed opinions on whether researchers or other foreign actors should have direct contact with water users. Language and cultural barriers may hinder effective communication, and in such settings in-country collaborators or uptake partners should take the lead.	“I’m very adverse to having some outsider come tell you what you need. So, if you can have people established in that community, working alongside community members, that’s the only way, the best way, to engage and exchange knowledge on those types of opportunities.” (Cl_14)	24	4.9 (0.3–9.1)
A3 participatory planning (enabler)	The involvement of water users and other local actors in the implementation process is an important factor in implementation adoption. Key informants emphasized the importance of collaboration with local institutions. Roundtable discussions and community meetings for information dissemination are common, but codesign and participatory planning is uncommon and is considered to have good potential to improve the design and acceptability of treatment interventions.	“I feel like really starting with engaging the community you’ve actually impacted and using participatory research methods where you are actively conducting needs assessments or asking the community to work on the research in terms of designing experimental studies or the actual implementation plan.” (Cl_04)	4	1.0 (0.3–2.2)
IMPLEMENTATION
I1 long-term financing (enabler)	Sustained long-term financing is required to enable ongoing operations and maintenance of rural water treatment. Securing initial and ongoing sources of financing is a key challenge for technology implementation efforts.	“I mean, I hate to keep repeating myself, but I think it really sort of comes back to the education, economic issues and business issues. I think those are really the biggest barriers.” (UV_09)	25	8.2 (0.9–33.4)
I2 burden on households and community (barrier)	The distribution of the labor and other operating costs that are required to sustain water treatment is a key consideration. Where this labor is distributed to households, as with household-level water treatment technologies, or to community water management committees that have no external support, it represents a burden, often borne by women and girls, that has been found to be widely untenable in impoverished communities.	“Whether you’re talking about household, community, institutional utility, if you assume that the users are going to take ownership and maintain the system on their own, you might be ignoring a large part of the financial and time and cost burden which are often gendered, that are associated with this long-term operation and maintenance.” (Cl_04)	19	4.4 (0.9–16.2)
I3 costs of installation and operations (barrier)	The costs of chlorination and UV technology products, including consumables, spare parts, maintenance, and monitoring costs are a consistent challenge for projects that are focused on rural areas of LICs and LMICs. Introducing new costs in resource constrained settings is challenging and projects are looking to fit-for-purpose technology design and innovative service delivery models for ways forward.	“I think that’s the biggest challenge, really, is if you want to make it financially self-sustainable. How do you do that? People can’t afford it basically. Or if it’s not priority for people’s money.” (Cl_01)	19	1.9 (0.5–5.9)
I4 supported service delivery (enabler)	Operation and maintenance (O&M) services must be in place to ensure that treatment technologies remain functional after installation. Water committees or boards, consisting of local resident members who are responsible for operating the technologies through nonpaid positions, are widely cited as having a role in O&M. However, hybrid institutional arrangements are sought to support communities with technical capabilities, supply chains, and long-term financing. Interviewees emphasize the importance of engaging with the “right” partners, stating that these should either be local entities or actors that will work locally for a long time.	“You really need some sort of outside organization support for the maintenance of these chlorination technologies or, you know, whether it’s just having some sort of technical support, like to consult if something goes wrong to help, you know, maintain the supply chain, get replacement parts, either some local NGO or just as much more buy in from local governments is something that I think is going to be required.” (Cl_02)	17	5.5 (0.4–20.1)
MAINTENANCE/SUSTAINABILITY
M1 evidence of improvement in health outcomes (enabler)	Ultimately, the purpose of drinking-water treatment is to reduce health risk and improve health outcomes. Interviewees discussed the challenges of measuring the health impacts of treatment implementation. Understanding and evidence of health impacts is important to sustain the justification for treatment and motivation to collaborate on development and implementation of treatment technologies.	“When it comes to measurable health impacts, a lot of the big studies that look at various interventions are showing that water is quite a small piece of that puzzle. It has a lot to do with malnutrition, also with hand hygiene.” (Cl_07)	16	3.7 (1.4–8.1)
M2 supply chain challenges (barrier)	For chlorine and UV treatment, as well as water quality monitoring, nascent or nonexistent markets and the remoteness of rural localities creates challenges for the consistency and affordability of access to components and consumables. These supply chain issues are a key consideration for fit-for-purpose design and a key limitation on technology selection.	“We, let’s say, pushed to most (to choose) the locally, locally built chlorinators, I mean the parts are quite easily available. Sometimes they had to go to the capital to get parts, but most of them were available on the local markets.” (Cl_08)	26	9.1 (0.6–17.6)
M3 complex pretreatment water quality (barrier)	UV radiation and chlorine are less effective when applied to turbid waters. High concentrations of dissolved organic matter react problematically with chlorine, increasing DBP risk. Furthermore, disinfection does not reduce risks from chemical contamination which must also be considered for full drinking water safety to be achieved. In cases where turbidity and water chemistry challenges are substantial, pretreatment may be warranted before disinfection with chlorine or UV.	“I think what would make sense if you have higher turbid water or other chemical or biological contaminants would be to pre-treat the water that is coming in.” (Cl_04)	18	4.7 (1.0–16.9)
M4 climate change and climate variability risks (barrier)	Climate change and climate variability influence the complexity and predictability of pretreatment water quality challenges. They are also associated with wider risks to WASH infrastructure from extreme events, particularly drought and flooding.	“So, you know, I think we’re gonna see more and more WASH related challenges with climate, flooding, for example, or drought. I mean, it’s weird because it’s kind of at the extremes.” (Cl_15)	18	3.0 (0.1–8.2)
M5 water quality monitoring (enabler)	Water quality monitoring is complementary to water treatment implementation, it is required to calibrate dosing/fluence, manage DBP risk, and to develop the design and operation of treatment technology to improve effectiveness. In 3 interviews, informants also discussed the role of water quality monitoring for identifying emerging contaminants that affect the complexity of pretreatment water quality.	“Climate change is a challenge because it changes the quality of our source waters. And that can make it harder to treat them. It can add new pathogens or new contaminants to the water that old UV systems are not designed to handle. And so, monitoring of source of water and monitoring of the performance of UV systems against those sorts of waters, I think will be important.” (UV_04)	6	2.3 (0.3–4.8)

To further explore the systemic complexity of rural water treatment implementation, a network diagram was then produced by using a modified fuzzy cognitive mapping (FCM) technique to synthesize the key relationships between enablers and barriers (Figure 2). FCM is a form of systems mapping that uses nodes and edges to explore how causal influences propagate through a dynamic system. (80) Traditionally, FCM includes assigning numerical values to both the nodes and edges in the system map to represent either confidence in or magnitude of causal effects. (80) Given the qualitative nature of the data in our study and because we did not ask key informants to rank the importance of different enables and barriers, we did not make numerical assignments in this way. Instead, we assigned node sizes by calculating the natural logarithm of the number of interviews that discussed each topic multiplied by the average coding coverage for that topic. Links (edges) between topics (nodes) are shown where any key informant discussed causal connections between the topics, and we assigned edges as a binary of having either a strengthening or weakening influence. Thus, the network diagram in Figure 2 visualizes the collective response from our key informants, with node size roughly representing the depth of content for each topic. Figure 2 is intended to be used as a conceptual tool, to represent the complexity of rural water treatment implementation, and to generate discussion. It should be understood as a partial representation of an evolving CAS.

Figure 2. Network diagram showing relationships between the principal enablers and barriers to sustained rural water treatment. Each node is described in Table 2. The node size is the natural logarithm of the number of interviews that discussed each topic multiplied by the average coding coverage for that topic. Links between nodes are shown, where key informants discussed connections between the topics. The diagram layout is generated by the Fruchterman-Reingold force-directed layout algorithm in the R “igraph” package.

3. Results and Discussion

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Content analysis of the 26 interviews conducted for this research produced a set of 110 factors that influence the implementation of rural water treatment with passive chlorination or UV technology. Organized by the dimensions of the RE-AIM framework: reach (12 factors), effectiveness (15), adoption (19), implementation (31), and maintenance/sustainability (33), these factors demonstrate the breadth of considerations for rural water treatment initiatives (Supporting Information Figure 1). The factors can be grouped into 18 principal enablers of or barriers to sustaining rural water treatment (Table 2). The label of enabler or barrier is allocated based on whether the presence of the factor in question is enabling or inhibiting. Thus, enablers are beneficial when they are present but can be barriers or have neutral influence in their absence. Barriers are problematic when they are present, but their absence can be neutral or enabling.

The enablers and barriers described in Table 2 are components of a CAS for rural water supply. Seven of the key informants spoke about technology implementation with explicit systems-language. For example, one key informant said:

“There’s a lot of confounding variables, because it is very hard just to put this technology in and then walk away and let it run. It definitely has to be a systems approach for the technology to succeed at all. So then if there is a decrease in disease, it’s attributable to both the technology but also the system that has been created” (Cl_03).

Most informants discussed technology implementation in more linear terms of siloed causes and effects. However, analysis of the relationships between the 18 principal enablers and barriers identified from the interviews provides insight into the propagation of causal influence within a system (Figure 2), which is key to understanding the dynamics of a CAS.

The demography and characteristics of a technology user/customer base determine whether interventions advance health equity or reinforce inequities. In 5 interviews, we were told that the potential user/customer base for decentralized water treatment technologies is vast and diverse (Table 2: R1). This is supported by a recent study that estimates 1.2 billion people living in rural areas globally are using microbially contaminated water sources that are compatible with passive chlorination treatment technology. (81) Our key informants indicated that the two most prominent enablers of more extensive technology reach are collaboration between facilitating actors (R2) and water user acceptance of water treatment (A1). We examined how these enablers are reinforced or undermined.

3.1. Evidence of Health Improvements Catalyzes Collaboration Around a Shared Purpose

The intended purpose of rural water treatment is to sustain improvements in health. In keeping with this positioning, a key principal enabler in the maintenance/sustainability category of our results is measurable improvement in health outcomes (Table 2: M1). Evidence and perception of positive health impacts were found to promote collaboration between facilitating actors (R2), particularly between funders and implementers. For example, in July 2022, GiveWell recommended an Open Philanthropy grant of up to 5.6 million USD to fund an in-line chlorination program in Malawi. (82) Their recommendation relied on an evaluation of cost-effectiveness in improving health outcomes and emphasized the value of high-quality data to improve the precision of cost-effectiveness estimates. Health impact evidence can thus support funding partnerships that enable water treatment interventions to have a more extensive reach (R1), including reaching people who are vulnerable in marginalized contexts. Thus, a reinforcing feedback is described where evidence of health improvements (M1) reinforces collaboration (R2) and financing (I1), which increases the scale of the user base (R1) and reinforces health improvements and the potential to provide evidence of health improvements (M1).

Our key informants pointed to water quality complexity (M3), climate risks (M4), and DBP risk (E3) as influences that weaken or contravene the usefulness of health improvement evidence (M1). More specifically, it was acknowledged that the complexity of confounding factors makes it difficult and expensive to evaluate health outcomes from drinking-water treatment interventions. Research has shown that the presence of passive chlorinators in rural communities resulted in significantly improved water quality, (2) but few studies have linked to health outcomes. Our key informants discussed perceived health improvements based on anecdotal evidence of reduced gastrointestinal symptoms among water users, and there is some systematic evidence of impact–for example, a randomized controlled trial in Dhaka showed evidence of a reduction in childhood diarrheal disease due to passive chlorination interventions. (31) Overall, however, this is an area for further work that could be used to leverage funding for rural water treatment implementation.

3.2. Communication and Service Delivery Approaches Drive Acceptability

Acceptance of a water treatment intervention by water users (Table 2: A1) is an adoption-related enabler that was discussed in all but one of the interviews as a major determinant of the user/customer base (R1). Specifically, acceptability of taste, odor and perceived risk is important to ensure continued consumption or willingness to pay for treated water sources, indicating the need for well-calibrated, reliable dosing (E1) and site-specific acceptability research. (30,46) Collaboration between facilitating actors (R2) has a role here in facilitating access, resources, and appropriate messaging for communication with communities (A2). Interviewees said that the results from water quality monitoring, another enabler (M5), can be used to communicate the benefits of water treatment to water users. However, uncertainty in interpretations of water-related health risk and the relative sparsity of rural water quality monitoring means that communicating water quality results can be difficult and there is limited precedent to draw upon. (83) Reporting approaches need to contextualize water quality results to mitigate the risk of maladaptive cognitive, behavioral, and institutional response outcomes. (24,83)

Beyond communication efforts, in 4 cases, interviewees also spoke about the value of engaging with communities and local institutions in participatory planning processes (A3). A key consideration for planning implementation of water treatment is the distribution of costs (I3). Costs, including labor, reduce water users’ acceptance of treatment implementation (A1) when they are borne by the community (I2). In contexts of poverty, by definition, people are vulnerable, and meeting basic needs is a daily struggle. Allocation of water treatment costs exclusively to community-level is problematic for the same reasons that have been extensively explicated for the widespread failure of unsupported community-based management to sustain water supply functionality. (84,85) In developing beyond the community-based management model, the rural water sector is experiencing rapid innovation and proliferation of service delivery models. Seventeen key informants discussed this topic, highlighting the need for hybrid institutional arrangements to sustain the operation and maintenance (O&M) of treatment technologies (I4). Hybrid service delivery approaches were noted as a means to consolidate operating costs and labor that would otherwise be borne by households or communities alone (I2), facilitate water quality monitoring (M5), buffer against supply chain volatility (M2), and leverage multiple funding sources for long-term financing (I1).

Key informants spoke about challenges with introducing additional cost to water service delivery in resource constrained settings (I3). Most of the focus was on operating costs, recognizing that capital expenditure for small-scale, decentralized water treatment is typically low relative to the overall capital expenditure for water supply systems. All but one key informant raised the importance of long-term financing (I1). Specific funding arrangements and service delivery models vary by the context. Based on our interviews, external funding has most commonly been acquired through research grants and development project funding from foundations, international development organizations, and government development funding. Several of the professionalized water service delivery organizations that we engaged with in this research are trialing results-based funding arrangements to encourage further investment in rural water service provision. Professionalized service delivery (I4) and long-term financing (I1) were discussed as mutually reinforcing enablers of rural water treatment. Additionally, commercial entities, such as manufacturers, were found to collaborate on projects by donating devices or refills in-kind. Two key informants also spoke about the funding potential from carbon credit schemes. Since passive chlorination is an alternative to boiling water, which is done by burning wood, there is an indirect reduction in carbon emissions; however, carbon credits are not a predictable or stable source of finance as regulations change on a yearly basis and the verification process can take several years.

3.3. Fit-For-Purpose Technology Mitigates Implementation and Maintenance Barriers

In the previous sections, collaboration of facilitating actors (R2) is discussed primarily in relation to financing (I1) and a technology’s user/customer base (R1). Actor collaboration also has an important influence on technology development (E4). There remains a division between research and practice within drinking water treatment. Research, and the experimentation involved are essential for technology development (Table 2: E4), but research timelines and funding are often limited to only a few years. NGOs and other implementers, on the other hand, seek to roll out programs that will have benefits for as many people as possible, and thus may not have the capacity for rigorous data collection and experimentation, which is very expensive. To bridge this gap, key informants highlighted a need for more collaboration between facilitating actors (R2), particularly knowledge exchange across research, implementation, and commercial spaces.

A key objective of collaborative technology development is to improve fit-for-purpose design (E2). “Fit-for-purpose” simply means that something does what it is intended to do. The challenge is to design treatment technologies that are fit-for-purpose in different contexts. Interviewees emphasized that the effectiveness of water treatment technologies in a particular context is determined by their appropriateness for the water supply infrastructure and pretreatment water quality. Fit-for-purpose technology design is strongly linked to two principal topics: costs of installation, O&M (I3) and dosing/fluence calibration and reliability (E1), which is further linked to management of DBP risk (E3). Many design options exist, (8,34,86−89) with a multitude of trade-offs to consider. However, there is still room for product design growth, particularly regarding trade-offs between precise dosing, device complexity, and affordability. There are also key trade-offs to consider when choosing between chlorination and UV disinfection approaches. Ongoing technology development (E4)─especially in UV–C LED capabilities–means that these trade-offs are evolving and fit-for-purpose design is improving. Two key fixed considerations, however, are that UV treatment is more effective against a broader range of pathogens, (54) but provides no residual disinfection capacity, making it potentially best applied together with chlorination for a better overall performance.

Irrespective of treatment design, water quality monitoring provides critical information feedback to understand the effectiveness of disinfection (M5). Although this topic was only raised by 6 key informants, they highlighted links between water quality monitoring and many other nodes in our systems analysis, thus M5 has more links than any other topic (Figure 2). An increase in water quality monitoring leads to increased costs (I3), which (as a barrier to sustaining treatment and related activities) could lead to a subsequent roll-back of monitoring. However, this simple balancing feedback loop is made more complex because through several causal connections (Figure 2), monitoring can become a strengthening force for financing arrangements that offset the costs of doing the monitoring. This applies to the extent that information from monitoring is useful to improve the effectiveness, acceptability, and perceived value of treatment. Excessive monitoring should still be counteracted by the associated cost. Development in water quality monitoring capabilities is another area that can reinforce fit-for-purpose design (E2) to reduce costs (I3) while strengthening water users’ acceptance of water treatment (A1) through improved dosing (E1) and communication (A2). Research is ongoing in this space, focusing particularly on regulatory compliance, indicators for microbial activity, and sensor development. (28,30,90,91)

3.4. Leverage Points for Sustainable Rural Water Treatment

The results of this study demonstrate the systemic complexity of decentralized water treatment implementation in resource-constrained settings. Beyond the ability of a technology to improve the microbial safety of a water supply, the sustainability of treatment is dependent on a broad set of socio-economic and environmental factors. By distilling the principal enablers and barriers discussed in key informant interviews and by exploring their interrelationships, we identify multiple forms of leverage through which the sustainability of water treatment can be reinforced. In CAS, leverage points are processes or activities wherein a discrete intervention will influence wider system behavior toward an intended purpose. (92) Meadows categorized 12 types of leverage points that scale from the positional leverage of mindsets/paradigms, which have the broadest influence but are most difficult to change, to the physical leverage of system component parameters, which are easier to change but have more localized influence. (92) Our analysis, as laid out in the previous sections, identifies physical, feedback, and institutional forms of leverage for water treatment sustainability.

The results encourage an orientation toward fit-for-purpose technology design. Rather than looking for a “silver bullet” technology, the sector can develop a portfolio of treatment designs and implementation protocols that are suited to different environmental and institutional settings, even within a single service area. Technology development grapples with trade-offs between dosing effectiveness and device simplicity, with strong implications for health impacts, user acceptance, ease of O&M, supply chain reliability, and affordability. The specific form of these trade-offs varies extensively between contexts, so locally informed design and O&M decisions are warranted. Hybrid service delivery models are found to support the feasibility of a fit-for-purpose approach by (a) strengthening financing and monitoring and (b) mitigating challenges of distributing monetary and labor costs and buffering supply chain volatility. With reference to Meadows’ framework, (92) this can be understood as localized leverage (from modification of physical events and infrastructure) that is reinforced and scaled by feedback and institutional leverage from efficient structuring of information flows, financing, and management.

At a structural level, collaboration between actors is found to influence the sustainability of rural water treatment through multiple pathways. Knowledge exchange on the development of technological capabilities, service delivery, and related financing models is a key area for cooperation that aligns with a fit-for-purpose approach. In contrast, seeking “silver-bullets” and market dominance can create a competitive orientation that hampers knowledge exchange. Improved communication will ensure a faster progression of best practices to make interventions more accessible and locally appropriate. Working groups, knowledge exchange platforms, and communities of practice are facilitating the sharing of innovation and best practice. The International Ultraviolet Association (IUVA), formed an SDG Task Force that meets regularly to share research and practitioners’ experiences. With similar intentions of networking learning, an online Community of Practice on Decentralized Chlorine Use has formed under the leadership of PATH and EOS International (see the Community terms of reference and contact details in Supporting Information Annex 1).

Beyond knowledge exchange between facilitating actors, engagement with water user communities is highlighted as a priority in the mapping of our results (Figure 2). The nodes representing communication with water users (A2) and water users’ acceptance of water treatment (A1) are among the largest in the map because they were discussed in more than 90% of the interviews with average coding coverages of 4.9 and 6.5%, respectively. In comparison, participatory planning (A3) was discussed only in 15% of interviews with an average coding coverage of 1%. Despite its relatively small size, the participatory planning node is situated as an enabler of communication, acceptance, and fit-for-purpose design–it may represent an overlooked area for strengthening that could leverage substantial improvement in the sustainability of treatment implementation.

4. Conclusions

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In summary, taking a siloed approach to decentralized water treatment, solely through a technological lens, results in failed projects and stranded assets. To avoid this, systems-based analysis reveals the broader socioenvironmental factors and feedback loops that determine the sustainability of water treatment implementation. While this study focuses on passive chlorination and UV–C LED disinfection as its case studies, many of the identified enablers and barriers are generally applicable to other WASH interventions as well. Water treatment at the water-supply level (as opposed to household-level) is always an addition to an existing water service; therefore, an enabler or barrier to water services may also be an enabler or barrier to water treatment. The results of this study encourage a fit-for-purpose approach to intervention design that is reinforced and scaled through hybrid water service delivery models. Key information flows, financing, and management arrangements can be strengthened by collaboration among facilitating actors and with water users. Further attention is also encouraged to invest in and develop new forms of evidence of the health impacts and wider benefits of water treatment (Section 3.1), guidance for appropriate water quality reporting practices (Section 3.2), and technological capabilities that mitigate or help to optimally balance trade-offs in fit-for-purpose treatment design (Section 3.3).

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsestwater.3c00779.

Terms of reference of the community of practice on decentralized chlorine use (PDF)
Conceptual visualization of key categories and factors (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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Corresponding Authors
- Merel Laauwen - School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, U.K.; https://orcid.org/0009-0009-5245-5959; Email: [email protected]
- Saskia Nowicki - School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, U.K.; https://orcid.org/0000-0001-9011-6901; Email: [email protected]
Author Contributions
CRediT: Merel Laauwen conceptualization, data curation, formal analysis, investigation, methodology, project administration, validation, visualization, writing-original draft, writing-review & editing; Saskia Nowicki conceptualization, formal analysis, funding acquisition, investigation, methodology, supervision, validation, visualization, writing-original draft, writing-review & editing.
Notes
The authors declare no competing financial interest.

Acknowledgments

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This research was supported by the REACH program funded by UK Aid from the UK Foreign, Commonwealth and Development Office (FCDO) for the benefit of developing countries (Program Code 201880). It was also supported by the UK Medical Research Council (MRC) from the Public Health Intervention Development program (Award Reference MR/Y503174/1). M.L. was further supported in conducting this work by Brasenose College and the School of Geography and the Environment at the University of Oxford. The views expressed and information contained in this article are not necessarily those of or endorsed by the funders, which can accept no responsibility for such views or information, or for any reliance placed on them.

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Background: Safe drinking water is crit. for health. Household water treatment (HWT) has been recommended for improving access to potable water where existing sources are unsafe. Reports of low adherence to HWT may limit the usefulness of this approach, however. Methods and Findings: We constructed a quant. microbial risk model to predict gains in health attributable to water quality interventions based on a range of assumptions about pre-treatment water quality; treatment effectiveness in reducing bacteria, viruses, and protozoan parasites; adherence to treatment interventions; vol. of water consumed per person per day; and other variables. According to mean ests., greater than 500 DALYs may be averted per 100,000 person-years with increased access to safe water, assuming moderately poor pre-treatment water quality that is a source of risk and high treatment adherence (>90% of water consumed is treated). A decline in adherence from 100% to 90% reduces predicted health gains by up to 96%, with sharpest declines when pre-treatment water quality is of higher risk. Conclusions: Results suggest that high adherence is essential in order to realize potential health gains from HWT.
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Enger, K. S.; Nelson, K. L.; Rose, J. B.; Eisenberg, J. N. S. The joint effects of efficacy and compliance: A study of household water treatment effectiveness against childhood diarrhea. Water Res. 2013, 47, 1181– 1190, DOI: 10.1016/j.watres.2012.11.034
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The joint effects of efficacy and compliance: A study of household water treatment effectiveness against childhood diarrhea
Enger, Kyle S.; Nelson, Kara L.; Rose, Joan B.; Eisenberg, Joseph N. S.
Water Research (2013), 47 (3), 1181-1190CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
The effectiveness of household water treatment (HWT) at reducing diarrheal disease is related to the efficacy of the HWT method at removing pathogens, how people comply with HWT, and the relative contributions of other pathogen exposure routes. We define compliance with HWT as the proportion of drinking water treated by a community. Although many HWT methods are efficacious at removing or inactivating pathogens, their effectiveness within actual communities is decreased by imperfect compliance. However, the quant. relation between compliance and effectiveness is poorly understood. To assess the effectiveness of HWT on childhood diarrhea incidence via drinking water for 3 pathogen types (bacterial, viral, and protozoan), we developed a quant. microbial risk assessment (QMRA) model. We examd. the relation between log10 removal values (LRVs) and compliance with HWT for scenarios varying by: baseline incidence of diarrhea; etiol. fraction of diarrhea by pathogen type; pattern of compliance within a community; and size of contamination spikes in source water. Benefits from increasing LRVs strongly depend on compliance. For perfect compliance, diarrheal incidence decreases as LRVs increase. However, if compliance is incomplete, there are diminishing returns from increasing LRVs in most of the scenarios we considered. Higher LRVs are more beneficial if: contamination spikes are large; contamination levels are generally high; or some people comply perfectly. The effectiveness of HWT interventions at the community level may be limited by imperfect compliance, such that the benefits of high LRVs are not realized. Compliance with HWT should be carefully measured during HWT field studies and HWT dissemination programs. Studies of pathogen concns. in a variety of developing-country source waters are also needed. Guidelines are needed for measuring and promoting compliance with HWT.
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Luoto, J.; Najnin, N.; Mahmud, M.; Albert, J.; Islam, M. S.; Luby, S.; Unicomb, L.; Levine, D. I. What point-of-use water treatment products do consumers use? Evidence from a randomized controlled trial among the urban poor in Bangladesh. PLoS One 2011, 6, e26132 DOI: 10.1371/journal.pone.0026132
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What point-of-use water treatment products do consumers use? Evidence from a randomized controlled trial among the urban poor in Bangladesh
Luoto, Jill; Najnin, Nusrat; Mahmud, Minhaj; Albert, Jeff; Islam, M. Sirajul; Luby, Stephen; Unicomb, Leanne; Levine, David I.
PLoS One (2011), 6 (10), e26132CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)
Background: There is evidence that household point-of-use (POU) water treatment products can reduce the enormous burden of water-borne illness. Nevertheless, adoption among the global poor is very low, and little evidence exists on why. Methods: We gave 600 households in poor communities in Dhaka, Bangladesh randomly-ordered two-month free trials of four water treatment products: dil. liq. chlorine (sodium hypochlorite soln., marketed locally as Water Guard), sodium dichloroisocyanurate tablets (branded as Aquatabs), a combined flocculant-disinfectant powd. mixt. (the PUR Purifier of Water), and a silver-coated ceramic siphon filter. Consumers also received education on the dangers of untreated drinking water. We measured which products consumers used with self-reports, observation (for the filter), and chlorine tests (for the other products). We also measured drinking water's contamination with E. coli (compared to 200 control households). Findings: Households reported highest usage of the filter, although no product had even 30% usage. E. coli concns. in stored drinking water were generally lowest when households had Water Guard. Households that self-reported product usage had large redns. in E. coli concns. with any product as compared to controls. Conclusion: Traditional arguments for the low adoption of POU products focus on affordability, consumers' lack of information about germs and the dangers of unsafe water, and specific products not meshing with a household's preferences. In this study we provided free trials, repeated informational messages explaining the dangers of untreated water, and a variety of product designs. The low usage of all products despite such efforts makes clear that important barriers exist beyond cost, information, and variation among these four product designs. Without a better understanding of the choices and aspirations of the target end-users, household-based water treatment is unlikely to reduce morbidity and mortality substantially in urban Bangladesh and similar populations.
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Ray, I.; Smith, K. R. Towards safe drinking water and clean cooking for all. Lancet Glob. Health 2021, 9, e361– e365, DOI: 10.1016/s2214-109x(20)30476-9
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Nowicki, S.; Bukachi, S. A.; Hoque, S. F.; Katuva, J.; Musyoka, M. M.; Sammy, M. M.; Mwaniki, M.; Omia, D. O.; Wambua, F.; Charles, K. J. Fear, Efficacy, and Environmental Health Risk Reporting: Complex Responses to Water Quality Test Results in Low-Income Communities. Int. J. Environ. Res. Public Health 2022, 19, 597, DOI: 10.3390/ijerph19010597
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Fisher, J. Women in water supply, sanitation and hygiene programmes. Proc. Inst. Civ. Eng. Munic. Eng. 2008, 161, 223– 229, DOI: 10.1680/muen.2008.161.4.223
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Neely, K. Systems Thinking and WASH : Tools and Case Studies for a Sustainable Water Supply; Practical Action Publishing, 2019.
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Haque, S. S.; Freeman, M. C. The applications of implementation science in water, sanitation, and hygiene (Wash) research and practice. Environ. Health Perspect. 2021, 129, 1– 10, DOI: 10.1289/ehp7762
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Lui, G. Y.; Roser, D.; Corkish, R.; Ashbolt, N. J.; Stuetz, R. Point-of-use water disinfection using ultraviolet and visible light-emitting diodes. Sci. Total Environ. 2016, 553, 626– 635, DOI: 10.1016/j.scitotenv.2016.02.039
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Point-of-use water disinfection using ultraviolet and visible light-emitting diodes
Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas J.; Stuetz, Richard
Science of the Total Environment (2016), 553 (), 626-635CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different com. or semi-com. LED arrays (270-740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6 h. Five log10 and greater redns. were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log10s E. coli and E. faecalis over the 6 h). No significant disinfection was obsd. with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were obsd., particularly with UV-A wavelengths. The radiation doses required for > 3-log10 redn. of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5-2.5 fold at 365-455 nm. Action spectra, consistent with the literature, were obsd. with both indicators. The design process revealed cost and tech. constraints pertaining to LED elec. efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technol. is already tech. possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work.
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Lui, G. Y.; Roser, D.; Corkish, R.; Ashbolt, N.; Jagals, P.; Stuetz, R. Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters. Sci. Total Environ. 2014, 493, 185– 196, DOI: 10.1016/j.scitotenv.2014.05.104
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Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters
Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas; Jagals, Paul; Stuetz, Richard
Science of the Total Environment (2014), 493 (), 185-196CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
A review. For many decades, populations in rural and remote developing regions will be unable to access centralized piped potable water supplies, and indeed, decentralized options may be more sustainable. Accordingly, improved household point-of-use (POU) disinfection technologies are urgently needed. Compared to alternatives, UV light disinfection is very attractive because of its efficacy against all pathogen groups and minimal operational consumables. Though mercury arc lamp technol. is very efficient, it requires frequent lamp replacement, involves a toxic heavy metal, and their quartz envelopes and sleeves are expensive, fragile and require regular cleaning. An emerging alternative is semiconductor-based units where UV light emitting diodes (UV-LEDs) are powered by photovoltaics (PV). This review charts the development of these two technologies, their current status, and challenges to their integration and POU application. It explores the themes of UV-C-LEDs, non-UV-C LED technol. (e.g. UV-A, visible light, Advanced Oxidn.), PV power supplies, PV/LED integration and POU suitability. While UV-C LED technol. should mature in the next 10 years, research is also needed to address other unresolved barriers to in situ application as well as emerging research opportunities esp. UV-A, photocatalyst/photosensitizer use and pulsed emission options.
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Lindmark, M.; Cherukumilli, K.; Crider, Y. S.; Marcenac, P.; Lozier, M.; Voth-Gaeddert, L.; Lantagne, D. S.; Mihelcic, J. R.; Zhang, Q. M.; Just, C. Passive In-Line Chlorination for Drinking Water Disinfection: A Critical Review. Environ. Sci. Technol. 2022, 56, 9164– 9181, DOI: 10.1021/acs.est.1c08580
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Passive in-line chlorination for drinking water disinfection: a critical review
Lindmark, Megan; Cherukumilli, Katya; Crider, Yoshika S.; Marcenac, Perrine; Lozier, Matthew; Voth-Gaeddert, Lee; Lantagne, Daniele S.; Mihelcic, James R.; Zhang, Qianjin Marina; Just, Craig; Pickering, Amy J.
Environmental Science & Technology (2022), 56 (13), 9164-9181CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
A review. The world is not on track to meet Sustainable Development Goal 6.1 to provide universal access to safely managed drinking water by 2030. Removal of priority microbial contaminants by disinfection is one aspect of ensuring water is safely managed. Passive chlorination (also called in-line chlorination) represents one approach to disinfecting drinking water before or at the point of collection (POC), without requiring daily user input or electricity. In contrast to manual household chlorination methods typically implemented at the point of use (POU), passive chlorinators can reduce the user burden for chlorine dosing and enable treatment at scales ranging from communities to small municipalities. In this review, we synthesized evidence from 27 evaluations of passive chlorinators (in 19 articles, 3 NGO reports, and 5 theses) conducted across 16 countries in communities, schools, health care facilities, and refugee camps. Of the 27 passive chlorinators we identified, the majority (22/27) were solid tablet or granular chlorine dosers, and the remaining devices were liq. chlorine dosers. We identified the following research priorities to address existing barriers to scaled deployment of passive chlorinators: (i) strengthening local chlorine supply chains through decentralized liq. chlorine prodn., (ii) validating context-specific business models and financial sustainability, (iii) leveraging remote monitoring and sensing tools to monitor real-time chlorine levels and potential system failures, and (iv) designing handpump-compatible passive chlorinators to serve the many communities reliant on handpumps as a primary drinking water source. We also propose a set of reporting indicators for future studies to facilitate standardized evaluations of the tech. performance and financial sustainability of passive chlorinators. In addn., we discuss the limitations of chlorine-based disinfection and recognize the importance of addressing chem. contamination in drinking water supplies. Passive chlorinators deployed and managed at-scale have the potential to elevate the quality of existing accessible and available water services to meet "safely managed" requirements.
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Pickering, A. J.; Crider, Y.; Sultana, S.; Swarthout, J.; Goddard, F. G.; Anjerul Islam, S.; Sen, S.; Ayyagari, R.; Luby, S. P. Effect of in-line drinking water chlorination at the point of collection on child diarrhoea in urban Bangladesh: a double-blind, cluster-randomised controlled trial. Lancet Glob. Health 2019, 7, e1247– e1256, DOI: 10.1016/s2214-109x(19)30315-8
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Oguma, K.; Watanabe, S. Field Test of Ultraviolet Light-Emitting Diode (UV-LED) Apparatuses as an Option of Decentralized Water Treatment Technologies. J. Jpn. Soc. Water Environ. 2020, 43, 119– 126, DOI: 10.2965/jswe.43.119
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Amin, N.; Crider, Y. S.; Unicomb, L.; Das, K. K.; Gope, P. S.; Mahmud, Z. H.; Islam, M. S.; Davis, J.; Luby, S. P.; Pickering, A. J. Field trial of an automated batch chlorinator system at shared water points in an urban community of Dhaka, Bangladesh. J. Water Sanit. Hyg. Dev. 2016, 6, 32– 41, DOI: 10.2166/washdev.2016.027
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Dössegger, L.; Tournefier, A.; Germann, L.; Gärtner, N.; Huonder, T.; Etenu, C.; Wanyama, K.; Ouma, H.; Meierhofer, R. Assessment of low-cost, non-electrically powered chlorination devices for gravity-driven membrane water kiosks in eastern Uganda. Waterlines 2021, 40, 92– 106, DOI: 10.3362/1756-3488.20-00014
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Smith, D. W.; Sultana, S.; Crider, Y. S.; Islam, S. A.; Swarthout, J. M.; Goddard, F. G. B.; Rabbani, A.; Luby, S. P.; Pickering, A. J.; Davis, J. Effective Demand for In-Line Chlorination Bundled with Rental Housing in Dhaka, Bangladesh. Environ. Sci. Technol. 2021, 55, 12471– 12482, DOI: 10.1021/acs.est.1c01308
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Effective Demand for In-Line Chlorination Bundled with Rental Housing in Dhaka, Bangladesh
Smith, Daniel W.; Sultana, Sonia; Crider, Yoshika S.; Islam, Syed Anjerul; Swarthout, Jenna M.; Goddard, Frederick G. B.; Rabbani, Atonu; Luby, Stephen P.; Pickering, Amy J.; Davis, Jennifer
Environmental Science & Technology (2021), 55 (18), 12471-12482CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
Delivering safe water in cities of lower- and middle-income countries remains elusive even where there is a piped supply. Passive, in-line chlorination upstream of the point of water collection reduces child diarrhea without the behavior change required for point-of-use water treatment products or manual chlorine dispensers. We conducted a price expt. to measure effective demand (willingness and ability to pay) for an in-line chlorination service using tablet chlorinators among 196 landlords of rental housing properties in Dhaka, Bangladesh. We offered a 12-mo subscription using Becker-DeGroot-Marschak auctions with real money payments. The service consistently delivered chlorinated water and satisfied tenants. Landlords' effective demand for in-line chlorination was similar to or greater than that for point-of-use treatment products and manual chlorine dispensers previously documented among Dhaka households. Over the service period, landlords renting to low-income households had lower effective demand than those renting to middle-income households despite similar initial rates of payment across both groups. Making in-line chlorination financially viable for the lowest-income consumers would likely require service cost redns., subsidies, or both. Our findings suggest that even revealed preference expts. may overestimate the effective demand needed to sustain water supply improvements, esp. in low-income populations, if they only measure demand once.
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Adhikari, A.; Parraga Estrada, K. J.; Chhetri, V. S.; Janes, M.; Fontenot, K.; Beaulieu, J. C. Evaluation of ultraviolet (UV-C) light treatment for microbial inactivation in agricultural waters with different levels of turbidity. Food Sci. Nutr. 2020, 8, 1237– 1243, DOI: 10.1002/fsn3.1412
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Farrell, C.; Hassard, F.; Jefferson, B.; Leziart, T.; Nocker, A.; Jarvis, P. Turbidity composition and the relationship with microbial attachment and UV inactivation efficacy. Sci. Total Environ. 2018, 624, 638– 647, DOI: 10.1016/j.scitotenv.2017.12.173
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Turbidity composition and the relationship with microbial attachment and UV inactivation efficacy
Farrell, Charlotte; Hassard, Francis; Jefferson, Bruce; Leziart, Tangui; Nocker, Andreas; Jarvis, Peter
Science of the Total Environment (2018), 624 (), 638-647CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
Turbidity in water can be caused by a range of different turbidity causing materials (TCM). Here the characteristics and attachment of bacteria to TCMs was assessed and the resultant impact on UV disinfection detd. TCMs represent potential vehicles for bacterial penetration of water treatment barriers, contamination of potable supplies and impact on subsequent human health. The TCMs under investigation were representative of those that may be present in surface and ground waters, both from the source and formed in the treatment process. The TCMs were chalk, Fe (III) hydroxide ppt., kaolin clay, manganese dioxide and humic acids, at different turbidity levels representative of source waters (0, 0.1, 0.2, 0.4, 1, 2, and 5 NTU). Escherichia coli and Enterococcus faecalis attachment followed the order of Fe(III) > chalk, with little to no attachment seen for MnO2, humic acids and clay. The attachment was postulated to be due to chalk and Fe(III) particles having a more neutral surface charge resulting in elevated aggregation with bacteria compared to other TCMs. The humic acids and Fe(III) were the TCMs which influenced inactivation of E. coli and E. faecalis due to decreasing UV transmittance (UVT) with increasing TCM concn. The presence of the Fe(III) TCM at 0.2 NTU resulted in the poorest E. coli inactivation, with 2.5 log10 redn. at UV dose of 10 mJ cm- 2 (kd of - 0.23 cm2 mJ- 1) compared to a 3.9 log10 redn. in the absence of TCMs. E. faecalis had a greater resistance to UV irradn. than E. coli for all TCMs. Effective disinfection of drinking water is a priority for ensuring high public health stds. Uniform regulations for turbidity levels for waters pre-disinfection by UV light set by regulators may not always be appropriate and efficacy is dependent on the type, as well as the amt., of turbidity present in the water.
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Mitro, B.; Wolfe, M. K.; Galeano, M.; Sikder, M.; Gallandat, K.; Lantagne, D. Barriers and facilitators to chlorine tablet distribution and use in emergencies: A qualitative assessment. Water 2019, 11, 1121, DOI: 10.3390/w11061121
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Barriers and facilitators to chlorine tablet distribution and use in emergencies: a qualitative assessment
Mitro, Brittany; Wolfe, Marlene K.; Galeano, Mateo; Sikder, Mustafa; Gallandat, Karin; Lantagne, Daniele
Water (Basel, Switzerland) (2019), 11 (6), 1121CODEN: WATEGH; ISSN:2073-4441. (MDPI AG)
Chlorine tablets are commonly distributed for household water treatment in emergencies. However, confirmed use after distribution ranges widely (from 7-87%), which raises concerns about chlorine tablet effectiveness, as measured by acceptance and appropriate use. To investigate chlorine tablet effectiveness, we conducted nine key informant interviews (KIIs) on tablet distribution in emergencies in general, five KIIs on chlorine taste and odor acceptance and rejection specifically, and a literature review on chlorine taste and odor concerns. We found: (1) chlorine tablets are regarded as one of the most effective water treatment methods and are often considered appropriate in emergency response, (2) dosing confusion and taste and odor rejection are perceived as the main problems limiting effectiveness, and (3) the primary solns. suggested for these problems were social and behavioral. We recommend that social and behavioral scientists are routinely integrated into chlorine tablet programming to improve user feedback and behavioral interventions for chlorine tablet promotion in emergencies. We also suggest that more research is conducted on chlorine taste and odor rejection in vulnerable populations, and that improved guidance is developed to facilitate intra-agency coordination and select, promote, and monitor tablets appropriate for each context.
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Crider, Y.; System-level, Automatic Chlorination in Community-managed Water Systems. Water Supply Treat. 2019, 26– 27.
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Aumeier, B. M. The Hydrothermal Solution for Decentralized Drinking Water Purification The Hydrothermal Solution for Decentralized Drinking Water Purification. Ph.D. Thesis, Rheinisch-Westfälische Technische Hochschule Aachen, Germany, 2020. DOI: 10.18154/RWTH-2020-09122 .
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Aumeier, B. M.; Jiang, X.; Djeljadini, S.; Smeets, P.; Yüce, S.; Kazner, C.; Wessling, M. Evaluating water purification at household level in India. Desalin. Water Treat. 2017, 91, 311– 319, DOI: 10.5004/dwt.2017.20802
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Pickering, A. J.; Crider, Y.; Amin, N.; Bauza, V.; Unicomb, L.; Davis, J.; Luby, S. P. Differences in field effectiveness and adoption between a novel automated chlorination system and household manual chlorination of drinking water in Dhaka, Bangladesh: A randomized controlled trial. PLoS One 2015, 10, e1183977 DOI: 10.1371/journal.pone.0118397
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Cervero-Aragó, S.; Rodríguez-Martínez, S.; Puertas-Bennasar, A.; Araujo, R. M. Effect of common drinking water disinfectants, chlorine and heat, on free Legionella and amoebae-associated Legionella. PLoS One 2015, 10, 1– 18
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Chalmers, R. M.; Davies, A. P.; Tyler, K. Cryptosporidium. Microbiology 2019, 165, 500– 502, DOI: 10.1099/mic.0.000764
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Adeyemo, F. E.; Singh, G.; Reddy, P.; Bux, F.; Stenström, T. A. Efficiency of chlorine and UV in the inactivation of Cryptosporidium and Giardia in wastewater. PLoS One 2019, 14, e02160400 DOI: 10.1371/journal.pone.0216040
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Crider, Y.; Sultana, S.; Unicomb, L.; Davis, J.; Luby, S. P.; Pickering, A. J. Can you taste it? Taste detection and acceptability thresholds for chlorine residual in drinking water in Dhaka, Bangladesh. Sci. Total Environ. 2018, 613–614, 840– 846, DOI: 10.1016/j.scitotenv.2017.09.135
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Can you taste it? Taste detection and acceptability thresholds for chlorine residual in drinking water in Dhaka, Bangladesh
Crider, Yoshika; Sultana, Sonia; Unicomb, Leanne; Davis, Jennifer; Luby, Stephen P.; Pickering, Amy J.
Science of the Total Environment (2018), 613-614 (), 840-846CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
Chlorination is a low-cost, effective method for drinking water treatment, but aversion to the taste or smell of chlorinated water can limit use of chlorine treatment products. Forced choice triangle tests were used to evaluate chlorine detection and acceptability thresholds for two common types of chlorine among adults in Dhaka, Bangladesh, where previous studies have found low sustained uptake of chlorine water treatment products. The median detection threshold was 0.70 mg/L (n = 25, SD = 0.57) for water dosed with liq. sodium hypochlorite (NaOCl) and 0.73 mg/L (n = 25, SD = 0.83) for water dosed with solid sodium dichloroisocyanurate (NaDCC). Median acceptability thresholds (based on user report) were 1.16 mg/L (SD = 0.70) for NaOCl and 1.26 mg/L (SD = 0.67) for NaDCC. There was no significant difference in detection or acceptability thresholds for dosing with NaOCl vs. NaDCC. Although users are willing to accept treated water in which they can detect the taste of chlorine, their acceptability limit is well below the 2.0 mg/L that chlorine water treatment products are often designed to dose. For some settings, reducing dose may increase adoption of chlorinated water while still providing effective disinfection.
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Li, X. F.; Mitch, W. A. Drinking Water Disinfection Byproducts (DBPs) and Human Health Effects: Multidisciplinary Challenges and Opportunities. Environ. Sci. Technol. 2018, 52, 1681– 1689, DOI: 10.1021/acs.est.7b05440
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Drinking Water Disinfection Byproducts (DBPs) and Human Health Effects: Multidisciplinary Challenges and Opportunities
Li, Xing-Fang; Mitch, William A.
Environmental Science & Technology (2018), 52 (4), 1681-1689CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
A review. While drinking water disinfection has effectively prevented waterborne diseases, an unintended consequence is the generation of disinfection byproducts (DBPs). Epidemiol. studies have consistently obsd. an assocn. between consumption of chlorinated drinking water with an increased risk of bladder cancer. Out of the >600 DBPs identified, regulations focus on a few classes, such as trihalomethanes (THMs), whose concns. were hypothesized to correlate with the DBPs driving the toxicity of disinfected waters. However, the DBPs responsible for the bladder cancer assocn. remain unclear. Utilities are switching away from a reliance on chlorination of pristine drinking water supplies to the application of new disinfectant combinations to waters impaired by wastewater effluents and algal blooms. In light of these changes in disinfection practice, this article discusses new approaches being taken by anal. chemists, engineers, toxicologists and epidemiologists to characterize the DBP classes driving disinfected water toxicity, and suggests that DBP exposure should be measured using other DBP classes in addn. to THMs.
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Malayeri, A. H.; Mohseni, M.; Cairns, B. R.; B, J. UV Dose Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa and Viruses. IUVA News 2006, 8, 38– 45
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Water Research Foundation. WRF 4376: Guidance for Implementing Action Spectra Correction with Medium Pressure UV Disinfection; Water Research Foundation, 2015.
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Bolton, J. R.; Cotton, C. A. Ultraviolet Disinfection Handbook; American Water Works Association (AWWA), 2008.
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Simons, R.; Lawal, O.; Pagán, J. 2022 State of the Industry: UV-C LEDs and Their Applications. UV Solutions Mag , 2022. Available at: https://uvsolutionsmag.com/articles/2022/2022-state-of-the-industry-uv-c-leds-and-their-applications/ (accessed 18 August, 2022).
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Wu, H. Impact of the global chip shortage on the development of in-memory chips. Nat. Commun. 2022, 13, 4055
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Linden, K. G.; Hull, N.; Speight, V. Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection. Acc. Chem. Res. 2019, 52, 1226– 1233, DOI: 10.1021/acs.accounts.9b00060
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Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection
Linden, Karl G.; Hull, Natalie; Speight, Vanessa
Accounts of Chemical Research (2019), 52 (5), 1226-1233CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
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A review is given. Intermittent water supplies (IWS), in which water is provided through pipes for only limited durations, serve ≥300 million people around the world. However, providing water intermittently can compromise water quality in the distribution system. In IWS systems, the pipes do not supply water for periods of time, supply periods are shortened, and pipes experience regular flow restarting and draining. These unique behaviors affect distribution system water quality in ways that are different than during normal operations in continuous water supplies (CWS). A better understanding of the influence of IWS on mechanisms causing contamination can help lead to incremental steps that protect water quality and minimize health risks. This review examines the status and nature of IWS practices throughout the world, the evidence of the effect of IWS on water quality, and how the typical contexts in which IWS systems often exist-low-income countries with under-resourced utilities and inadequate sanitation infrastructure-can exacerbate mechanisms causing contamination. We then highlight knowledge gaps for further research to improve our understanding of water quality in IWS.
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Caroline Delaire, Katherine Marshall, Michal Usowicz, Tom Mahin, Daniel Kwaah, Bashiru Yachori, Bastian Schnabel, Ranjiv Khush, Rachel Peletz, . Comparison of passive and manual chlorination in small piped water networks in rural Ghana: Technical performance, ease-of-use, and cost. PLOS Water 2024, 3 (10) , e0000295. https://doi.org/10.1371/journal.pwat.0000295

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Abstract
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Figure 1
Figure 1. Updated RE-AIM Framework as presented by Shelton, Chambers and Glasgow 2020 [CC BY]. (74)
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Figure 2
Figure 2. Network diagram showing relationships between the principal enablers and barriers to sustained rural water treatment. Each node is described in Table 2. The node size is the natural logarithm of the number of interviews that discussed each topic multiplied by the average coding coverage for that topic. Links between nodes are shown, where key informants discussed connections between the topics. The diagram layout is generated by the Fruchterman-Reingold force-directed layout algorithm in the R “igraph” package.
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  Clasen, T. F.; Alexander, K. T.; Sinclair, D.; Boisson, S.; Peletz, R.; Chang, H. H.; Majorin, F.; Cairncross, S. Interventions to improve water quality for preventing diarrhoea. Cochrane Database Syst. Rev. 2015, 2015, CD004794, DOI: 10.1002/14651858.cd004794.pub3
  There is no corresponding record for this reference.
12. 12
  Luby, S. P.; Rahman, M.; Arnold, B. F.; Unicomb, L.; Ashraf, S.; Winch, P. J.; Stewart, C. P.; Begum, F.; Hussain, F.; Benjamin-Chung, J. Effects of water quality, sanitation, handwashing, and nutritional interventions on diarrhoea and child growth in rural Bangladesh: a cluster randomised controlled trial. Lancet Glob. Health 2018, 6, e302– e315, DOI: 10.1016/s2214-109x(17)30490-4
  There is no corresponding record for this reference.
13. 13
  Jh, H.; Mnn, M.; R, N.; Lh, M.; Rj, S.; Nv, T.; K, M.; F, M.; B, M.; G, M. Independent and combined effects of improved water, sanitation, and hygiene, and improved complementary feeding, on child stunting and anaemia in rural Zimbabwe: a cluster-randomised trial. Lancet Glob Health 2019, 7, 132– 179, DOI: 10.1530/ey.16.13.13
  There is no corresponding record for this reference.
14. 14
  Kirchhoff, L. V.; McClelland, K. E.; Pinho, M. D. C.; Araujo, J. G.; De Sousa, M. A.; Guerrant, R. L. Feasibility and Efficacy of In-Home Water Chlorination in Rural North-Eastern Brazil. J. Hyg. 1985, 94, 173– 180, DOI: 10.1017/s0022172400061374
  14
  Feasibility and efficacy of in-home water chlorination in rural North-eastern Brazil
  Kirchhoff L V; McClelland K E; Do Carmo Pinho M; Araujo J G; De Sousa M A; Guerrant R L
  The Journal of hygiene (1985), 94 (2), 173-80 ISSN:0022-1724.
  The purpose of this study was to assess the feasibility, acceptability and effect of an in-home water chlorination programme in a rural village. Previous studies at this site showed high levels of faecal coliforms in household water, high diarrhoea rates in children, and enterotoxigenic Escherichia coli and rotaviruses were the most common pathogens isolated from patients. Household water came from a pond and was stored in clay pots. No homes had sanitary facilities. A blind, cross-over trial of treatment of household water with inexpensive hypochlorite by a community health worker was carried out over 18 weeks among 20 families. Water in the clay pots was sampled serially, and symptom surveillance was done by medical students. The programme was generally acceptable to the villagers and no change in water use patterns were apparent. The mean faecal coliform level in the chlorinated water was significantly less than in the placebo treated samples (70 vs 16000 organisms/dl, P less than 0.001). People living in houses receiving placebo treatment had a mean of 11.2 days of diarrhoea per year, and the highest rate of 36.7 was among children less than 2 years old. Diarrhoea rates were not significantly different among the participants while exposed to water treated with hypochlorite. We conclude that a low-cost programme of this type, which utilizes community resources, is logistically feasible, appears to be culturally acceptable in this setting, and can result in a marked reduction in water contamination. The lack of effect on diarrhoea rates suggests that improvement in water quality may affect morbidity only when other variables relating to faecal-oral agent transmission are ameliorated at the same time.
15. 15
  Boisson, S.; Kiyombo, M.; Sthreshley, L.; Tumba, S.; Makambo, J.; Clasen, T. Field assessment of a novel household-based water filtration device: A randomised, placebo-controlled trial in the democratic Republic of Congo. PLoS One 2010, 5, e126133 DOI: 10.1371/journal.pone.0012613
  There is no corresponding record for this reference.
16. 16
  Jain, S.; Hoekstra, R. M.; Wannemuehler, K. A.; Schmitz, A.; Blanton, E.; Sahanoon, O. K.; Quick, R. E. Sodium dichloroisocyanurate tablets for routine treatment of household drinking water in periurban Ghana: A randomized controlled trial. Am. J. Trop. Med. Hyg. 2010, 82, 16– 22, DOI: 10.4269/ajtmh.2010.08-0584
  There is no corresponding record for this reference.
17. 17
  Boisson, S.; Stevenson, M.; Shapiro, L.; Kumar, V.; Singh, L. P.; Ward, D.; Clasen, T. Effect of Household-Based Drinking Water Chlorination on Diarrhoea among Children under Five in Orissa, India: A Double-Blind Randomised Placebo-Controlled Trial. PLoS Med. 2013, 10, e1001497 DOI: 10.1371/journal.pmed.1001497
  There is no corresponding record for this reference.
18. 18
  Pickering, A. J.; Null, C.; Winch, P. J.; Mangwadu, G.; Arnold, B. F.; Prendergast, A. J.; Njenga, S. M.; Rahman, M.; Ntozini, R.; Benjamin-Chung, J. The WASH Benefits and SHINE trials: interpretation of WASH intervention effects on linear growth and diarrhoea. Lancet Glob. Health 2019, 7, e1139– e1146, DOI: 10.1016/s2214-109x(19)30268-2
  There is no corresponding record for this reference.
19. 19
  Cumming, O.; Arnold, B. F.; Ban, R.; Clasen, T.; Esteves Mills, J.; Freeman, M. C.; Gordon, B.; Guiteras, R.; Howard, G.; Hunter, P. R. The implications of three major new trials for the effect of water, sanitation and hygiene on childhood diarrhea and stunting: A consensus statement. BMC Med. 2019, 17, 173, DOI: 10.1186/s12916-019-1410-x
  19
  The implications of three major new trials for the effect of water, sanitation and hygiene on childhood diarrhea and stunting: a consensus statement
  Cumming Oliver; Esteves Mills Joanna; Arnold Benjamin F; Colford John M Jr; Ban Radu; Rosenboom Jan Willem; Sundberg Shelly; Clasen Thomas; Freeman Matthew C; Gordon Bruce; Johnston Richard B; Pruss-Ustun Annette; Wolf Jennyfer; Guiteras Raymond; Howard Guy; Hunter Paul R; Pickering Amy J; Prendergast Andrew J; Spears Dean; Null Clair; Luby Stephen P; Humphrey Jean H
  BMC medicine (2019), 17 (1), 173 ISSN:.
  BACKGROUND: Three large new trials of unprecedented scale and cost, which included novel factorial designs, have found no effect of basic water, sanitation and hygiene (WASH) interventions on childhood stunting, and only mixed effects on childhood diarrhea. Arriving at the inception of the United Nations' Sustainable Development Goals, and the bold new target of safely managed water, sanitation and hygiene for all by 2030, these results warrant the attention of researchers, policy-makers and practitioners. MAIN BODY: Here we report the conclusions of an expert meeting convened by the World Health Organization and the Bill and Melinda Gates Foundation to discuss these findings, and present five key consensus messages as a basis for wider discussion and debate in the WASH and nutrition sectors. We judge these trials to have high internal validity, constituting good evidence that these specific interventions had no effect on childhood linear growth, and mixed effects on childhood diarrhea. These results suggest that, in settings such as these, more comprehensive or ambitious WASH interventions may be needed to achieve a major impact on child health. CONCLUSION: These results are important because such basic interventions are often deployed in low-income rural settings with the expectation of improving child health, although this is rarely the sole justification. Our view is that these three new trials do not show that WASH in general cannot influence child linear growth, but they do demonstrate that these specific interventions had no influence in settings where stunting remains an important public health challenge. We support a call for transformative WASH, in so much as it encapsulates the guiding principle that - in any context - a comprehensive package of WASH interventions is needed that is tailored to address the local exposure landscape and enteric disease burden.
20. 20
  Brown, J.; Clasen, T. High adherence is necessary to realize health gains from water quality interventions. PLoS One 2012, 7, e36735 DOI: 10.1371/journal.pone.0036735
  20
  High adherence is necessary to realize health gains from water quality interventions
  Brown, Joe; Clasen, Thomas
  PLoS One (2012), 7 (5), e36735CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)
  Background: Safe drinking water is crit. for health. Household water treatment (HWT) has been recommended for improving access to potable water where existing sources are unsafe. Reports of low adherence to HWT may limit the usefulness of this approach, however. Methods and Findings: We constructed a quant. microbial risk model to predict gains in health attributable to water quality interventions based on a range of assumptions about pre-treatment water quality; treatment effectiveness in reducing bacteria, viruses, and protozoan parasites; adherence to treatment interventions; vol. of water consumed per person per day; and other variables. According to mean ests., greater than 500 DALYs may be averted per 100,000 person-years with increased access to safe water, assuming moderately poor pre-treatment water quality that is a source of risk and high treatment adherence (>90% of water consumed is treated). A decline in adherence from 100% to 90% reduces predicted health gains by up to 96%, with sharpest declines when pre-treatment water quality is of higher risk. Conclusions: Results suggest that high adherence is essential in order to realize potential health gains from HWT.
21. 21
  Enger, K. S.; Nelson, K. L.; Rose, J. B.; Eisenberg, J. N. S. The joint effects of efficacy and compliance: A study of household water treatment effectiveness against childhood diarrhea. Water Res. 2013, 47, 1181– 1190, DOI: 10.1016/j.watres.2012.11.034
  21
  The joint effects of efficacy and compliance: A study of household water treatment effectiveness against childhood diarrhea
  Enger, Kyle S.; Nelson, Kara L.; Rose, Joan B.; Eisenberg, Joseph N. S.
  Water Research (2013), 47 (3), 1181-1190CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
  The effectiveness of household water treatment (HWT) at reducing diarrheal disease is related to the efficacy of the HWT method at removing pathogens, how people comply with HWT, and the relative contributions of other pathogen exposure routes. We define compliance with HWT as the proportion of drinking water treated by a community. Although many HWT methods are efficacious at removing or inactivating pathogens, their effectiveness within actual communities is decreased by imperfect compliance. However, the quant. relation between compliance and effectiveness is poorly understood. To assess the effectiveness of HWT on childhood diarrhea incidence via drinking water for 3 pathogen types (bacterial, viral, and protozoan), we developed a quant. microbial risk assessment (QMRA) model. We examd. the relation between log10 removal values (LRVs) and compliance with HWT for scenarios varying by: baseline incidence of diarrhea; etiol. fraction of diarrhea by pathogen type; pattern of compliance within a community; and size of contamination spikes in source water. Benefits from increasing LRVs strongly depend on compliance. For perfect compliance, diarrheal incidence decreases as LRVs increase. However, if compliance is incomplete, there are diminishing returns from increasing LRVs in most of the scenarios we considered. Higher LRVs are more beneficial if: contamination spikes are large; contamination levels are generally high; or some people comply perfectly. The effectiveness of HWT interventions at the community level may be limited by imperfect compliance, such that the benefits of high LRVs are not realized. Compliance with HWT should be carefully measured during HWT field studies and HWT dissemination programs. Studies of pathogen concns. in a variety of developing-country source waters are also needed. Guidelines are needed for measuring and promoting compliance with HWT.
22. 22
  Luoto, J.; Najnin, N.; Mahmud, M.; Albert, J.; Islam, M. S.; Luby, S.; Unicomb, L.; Levine, D. I. What point-of-use water treatment products do consumers use? Evidence from a randomized controlled trial among the urban poor in Bangladesh. PLoS One 2011, 6, e26132 DOI: 10.1371/journal.pone.0026132
  22
  What point-of-use water treatment products do consumers use? Evidence from a randomized controlled trial among the urban poor in Bangladesh
  Luoto, Jill; Najnin, Nusrat; Mahmud, Minhaj; Albert, Jeff; Islam, M. Sirajul; Luby, Stephen; Unicomb, Leanne; Levine, David I.
  PLoS One (2011), 6 (10), e26132CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)
  Background: There is evidence that household point-of-use (POU) water treatment products can reduce the enormous burden of water-borne illness. Nevertheless, adoption among the global poor is very low, and little evidence exists on why. Methods: We gave 600 households in poor communities in Dhaka, Bangladesh randomly-ordered two-month free trials of four water treatment products: dil. liq. chlorine (sodium hypochlorite soln., marketed locally as Water Guard), sodium dichloroisocyanurate tablets (branded as Aquatabs), a combined flocculant-disinfectant powd. mixt. (the PUR Purifier of Water), and a silver-coated ceramic siphon filter. Consumers also received education on the dangers of untreated drinking water. We measured which products consumers used with self-reports, observation (for the filter), and chlorine tests (for the other products). We also measured drinking water's contamination with E. coli (compared to 200 control households). Findings: Households reported highest usage of the filter, although no product had even 30% usage. E. coli concns. in stored drinking water were generally lowest when households had Water Guard. Households that self-reported product usage had large redns. in E. coli concns. with any product as compared to controls. Conclusion: Traditional arguments for the low adoption of POU products focus on affordability, consumers' lack of information about germs and the dangers of unsafe water, and specific products not meshing with a household's preferences. In this study we provided free trials, repeated informational messages explaining the dangers of untreated water, and a variety of product designs. The low usage of all products despite such efforts makes clear that important barriers exist beyond cost, information, and variation among these four product designs. Without a better understanding of the choices and aspirations of the target end-users, household-based water treatment is unlikely to reduce morbidity and mortality substantially in urban Bangladesh and similar populations.
23. 23
  Ray, I.; Smith, K. R. Towards safe drinking water and clean cooking for all. Lancet Glob. Health 2021, 9, e361– e365, DOI: 10.1016/s2214-109x(20)30476-9
  There is no corresponding record for this reference.
24. 24
  Nowicki, S.; Bukachi, S. A.; Hoque, S. F.; Katuva, J.; Musyoka, M. M.; Sammy, M. M.; Mwaniki, M.; Omia, D. O.; Wambua, F.; Charles, K. J. Fear, Efficacy, and Environmental Health Risk Reporting: Complex Responses to Water Quality Test Results in Low-Income Communities. Int. J. Environ. Res. Public Health 2022, 19, 597, DOI: 10.3390/ijerph19010597
  There is no corresponding record for this reference.
25. 25
  Fisher, J. Women in water supply, sanitation and hygiene programmes. Proc. Inst. Civ. Eng. Munic. Eng. 2008, 161, 223– 229, DOI: 10.1680/muen.2008.161.4.223
  There is no corresponding record for this reference.
26. 26
  Neely, K. Systems Thinking and WASH : Tools and Case Studies for a Sustainable Water Supply; Practical Action Publishing, 2019.
  There is no corresponding record for this reference.
27. 27
  Haque, S. S.; Freeman, M. C. The applications of implementation science in water, sanitation, and hygiene (Wash) research and practice. Environ. Health Perspect. 2021, 129, 1– 10, DOI: 10.1289/ehp7762
  There is no corresponding record for this reference.
28. 28
  Lui, G. Y.; Roser, D.; Corkish, R.; Ashbolt, N. J.; Stuetz, R. Point-of-use water disinfection using ultraviolet and visible light-emitting diodes. Sci. Total Environ. 2016, 553, 626– 635, DOI: 10.1016/j.scitotenv.2016.02.039
  28
  Point-of-use water disinfection using ultraviolet and visible light-emitting diodes
  Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas J.; Stuetz, Richard
  Science of the Total Environment (2016), 553 (), 626-635CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
  Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different com. or semi-com. LED arrays (270-740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6 h. Five log10 and greater redns. were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log10s E. coli and E. faecalis over the 6 h). No significant disinfection was obsd. with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were obsd., particularly with UV-A wavelengths. The radiation doses required for > 3-log10 redn. of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5-2.5 fold at 365-455 nm. Action spectra, consistent with the literature, were obsd. with both indicators. The design process revealed cost and tech. constraints pertaining to LED elec. efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technol. is already tech. possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work.
29. 29
  Lui, G. Y.; Roser, D.; Corkish, R.; Ashbolt, N.; Jagals, P.; Stuetz, R. Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters. Sci. Total Environ. 2014, 493, 185– 196, DOI: 10.1016/j.scitotenv.2014.05.104
  29
  Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters
  Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas; Jagals, Paul; Stuetz, Richard
  Science of the Total Environment (2014), 493 (), 185-196CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
  A review. For many decades, populations in rural and remote developing regions will be unable to access centralized piped potable water supplies, and indeed, decentralized options may be more sustainable. Accordingly, improved household point-of-use (POU) disinfection technologies are urgently needed. Compared to alternatives, UV light disinfection is very attractive because of its efficacy against all pathogen groups and minimal operational consumables. Though mercury arc lamp technol. is very efficient, it requires frequent lamp replacement, involves a toxic heavy metal, and their quartz envelopes and sleeves are expensive, fragile and require regular cleaning. An emerging alternative is semiconductor-based units where UV light emitting diodes (UV-LEDs) are powered by photovoltaics (PV). This review charts the development of these two technologies, their current status, and challenges to their integration and POU application. It explores the themes of UV-C-LEDs, non-UV-C LED technol. (e.g. UV-A, visible light, Advanced Oxidn.), PV power supplies, PV/LED integration and POU suitability. While UV-C LED technol. should mature in the next 10 years, research is also needed to address other unresolved barriers to in situ application as well as emerging research opportunities esp. UV-A, photocatalyst/photosensitizer use and pulsed emission options.
30. 30
  Lindmark, M.; Cherukumilli, K.; Crider, Y. S.; Marcenac, P.; Lozier, M.; Voth-Gaeddert, L.; Lantagne, D. S.; Mihelcic, J. R.; Zhang, Q. M.; Just, C. Passive In-Line Chlorination for Drinking Water Disinfection: A Critical Review. Environ. Sci. Technol. 2022, 56, 9164– 9181, DOI: 10.1021/acs.est.1c08580
  30
  Passive in-line chlorination for drinking water disinfection: a critical review
  Lindmark, Megan; Cherukumilli, Katya; Crider, Yoshika S.; Marcenac, Perrine; Lozier, Matthew; Voth-Gaeddert, Lee; Lantagne, Daniele S.; Mihelcic, James R.; Zhang, Qianjin Marina; Just, Craig; Pickering, Amy J.
  Environmental Science & Technology (2022), 56 (13), 9164-9181CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
  A review. The world is not on track to meet Sustainable Development Goal 6.1 to provide universal access to safely managed drinking water by 2030. Removal of priority microbial contaminants by disinfection is one aspect of ensuring water is safely managed. Passive chlorination (also called in-line chlorination) represents one approach to disinfecting drinking water before or at the point of collection (POC), without requiring daily user input or electricity. In contrast to manual household chlorination methods typically implemented at the point of use (POU), passive chlorinators can reduce the user burden for chlorine dosing and enable treatment at scales ranging from communities to small municipalities. In this review, we synthesized evidence from 27 evaluations of passive chlorinators (in 19 articles, 3 NGO reports, and 5 theses) conducted across 16 countries in communities, schools, health care facilities, and refugee camps. Of the 27 passive chlorinators we identified, the majority (22/27) were solid tablet or granular chlorine dosers, and the remaining devices were liq. chlorine dosers. We identified the following research priorities to address existing barriers to scaled deployment of passive chlorinators: (i) strengthening local chlorine supply chains through decentralized liq. chlorine prodn., (ii) validating context-specific business models and financial sustainability, (iii) leveraging remote monitoring and sensing tools to monitor real-time chlorine levels and potential system failures, and (iv) designing handpump-compatible passive chlorinators to serve the many communities reliant on handpumps as a primary drinking water source. We also propose a set of reporting indicators for future studies to facilitate standardized evaluations of the tech. performance and financial sustainability of passive chlorinators. In addn., we discuss the limitations of chlorine-based disinfection and recognize the importance of addressing chem. contamination in drinking water supplies. Passive chlorinators deployed and managed at-scale have the potential to elevate the quality of existing accessible and available water services to meet "safely managed" requirements.
31. 31
  Pickering, A. J.; Crider, Y.; Sultana, S.; Swarthout, J.; Goddard, F. G.; Anjerul Islam, S.; Sen, S.; Ayyagari, R.; Luby, S. P. Effect of in-line drinking water chlorination at the point of collection on child diarrhoea in urban Bangladesh: a double-blind, cluster-randomised controlled trial. Lancet Glob. Health 2019, 7, e1247– e1256, DOI: 10.1016/s2214-109x(19)30315-8
  There is no corresponding record for this reference.
32. 32
  Oguma, K.; Watanabe, S. Field Test of Ultraviolet Light-Emitting Diode (UV-LED) Apparatuses as an Option of Decentralized Water Treatment Technologies. J. Jpn. Soc. Water Environ. 2020, 43, 119– 126, DOI: 10.2965/jswe.43.119
  There is no corresponding record for this reference.
33. 33
  Amin, N.; Crider, Y. S.; Unicomb, L.; Das, K. K.; Gope, P. S.; Mahmud, Z. H.; Islam, M. S.; Davis, J.; Luby, S. P.; Pickering, A. J. Field trial of an automated batch chlorinator system at shared water points in an urban community of Dhaka, Bangladesh. J. Water Sanit. Hyg. Dev. 2016, 6, 32– 41, DOI: 10.2166/washdev.2016.027
  There is no corresponding record for this reference.
34. 34
  Dössegger, L.; Tournefier, A.; Germann, L.; Gärtner, N.; Huonder, T.; Etenu, C.; Wanyama, K.; Ouma, H.; Meierhofer, R. Assessment of low-cost, non-electrically powered chlorination devices for gravity-driven membrane water kiosks in eastern Uganda. Waterlines 2021, 40, 92– 106, DOI: 10.3362/1756-3488.20-00014
  There is no corresponding record for this reference.
35. 35
  Smith, D. W.; Sultana, S.; Crider, Y. S.; Islam, S. A.; Swarthout, J. M.; Goddard, F. G. B.; Rabbani, A.; Luby, S. P.; Pickering, A. J.; Davis, J. Effective Demand for In-Line Chlorination Bundled with Rental Housing in Dhaka, Bangladesh. Environ. Sci. Technol. 2021, 55, 12471– 12482, DOI: 10.1021/acs.est.1c01308
  35
  Effective Demand for In-Line Chlorination Bundled with Rental Housing in Dhaka, Bangladesh
  Smith, Daniel W.; Sultana, Sonia; Crider, Yoshika S.; Islam, Syed Anjerul; Swarthout, Jenna M.; Goddard, Frederick G. B.; Rabbani, Atonu; Luby, Stephen P.; Pickering, Amy J.; Davis, Jennifer
  Environmental Science & Technology (2021), 55 (18), 12471-12482CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
  Delivering safe water in cities of lower- and middle-income countries remains elusive even where there is a piped supply. Passive, in-line chlorination upstream of the point of water collection reduces child diarrhea without the behavior change required for point-of-use water treatment products or manual chlorine dispensers. We conducted a price expt. to measure effective demand (willingness and ability to pay) for an in-line chlorination service using tablet chlorinators among 196 landlords of rental housing properties in Dhaka, Bangladesh. We offered a 12-mo subscription using Becker-DeGroot-Marschak auctions with real money payments. The service consistently delivered chlorinated water and satisfied tenants. Landlords' effective demand for in-line chlorination was similar to or greater than that for point-of-use treatment products and manual chlorine dispensers previously documented among Dhaka households. Over the service period, landlords renting to low-income households had lower effective demand than those renting to middle-income households despite similar initial rates of payment across both groups. Making in-line chlorination financially viable for the lowest-income consumers would likely require service cost redns., subsidies, or both. Our findings suggest that even revealed preference expts. may overestimate the effective demand needed to sustain water supply improvements, esp. in low-income populations, if they only measure demand once.
36. 36
  Adhikari, A.; Parraga Estrada, K. J.; Chhetri, V. S.; Janes, M.; Fontenot, K.; Beaulieu, J. C. Evaluation of ultraviolet (UV-C) light treatment for microbial inactivation in agricultural waters with different levels of turbidity. Food Sci. Nutr. 2020, 8, 1237– 1243, DOI: 10.1002/fsn3.1412
  There is no corresponding record for this reference.
37. 37
  Farrell, C.; Hassard, F.; Jefferson, B.; Leziart, T.; Nocker, A.; Jarvis, P. Turbidity composition and the relationship with microbial attachment and UV inactivation efficacy. Sci. Total Environ. 2018, 624, 638– 647, DOI: 10.1016/j.scitotenv.2017.12.173
  37
  Turbidity composition and the relationship with microbial attachment and UV inactivation efficacy
  Farrell, Charlotte; Hassard, Francis; Jefferson, Bruce; Leziart, Tangui; Nocker, Andreas; Jarvis, Peter
  Science of the Total Environment (2018), 624 (), 638-647CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
  Turbidity in water can be caused by a range of different turbidity causing materials (TCM). Here the characteristics and attachment of bacteria to TCMs was assessed and the resultant impact on UV disinfection detd. TCMs represent potential vehicles for bacterial penetration of water treatment barriers, contamination of potable supplies and impact on subsequent human health. The TCMs under investigation were representative of those that may be present in surface and ground waters, both from the source and formed in the treatment process. The TCMs were chalk, Fe (III) hydroxide ppt., kaolin clay, manganese dioxide and humic acids, at different turbidity levels representative of source waters (0, 0.1, 0.2, 0.4, 1, 2, and 5 NTU). Escherichia coli and Enterococcus faecalis attachment followed the order of Fe(III) > chalk, with little to no attachment seen for MnO2, humic acids and clay. The attachment was postulated to be due to chalk and Fe(III) particles having a more neutral surface charge resulting in elevated aggregation with bacteria compared to other TCMs. The humic acids and Fe(III) were the TCMs which influenced inactivation of E. coli and E. faecalis due to decreasing UV transmittance (UVT) with increasing TCM concn. The presence of the Fe(III) TCM at 0.2 NTU resulted in the poorest E. coli inactivation, with 2.5 log10 redn. at UV dose of 10 mJ cm- 2 (kd of - 0.23 cm2 mJ- 1) compared to a 3.9 log10 redn. in the absence of TCMs. E. faecalis had a greater resistance to UV irradn. than E. coli for all TCMs. Effective disinfection of drinking water is a priority for ensuring high public health stds. Uniform regulations for turbidity levels for waters pre-disinfection by UV light set by regulators may not always be appropriate and efficacy is dependent on the type, as well as the amt., of turbidity present in the water.
38. 38
  Mitro, B.; Wolfe, M. K.; Galeano, M.; Sikder, M.; Gallandat, K.; Lantagne, D. Barriers and facilitators to chlorine tablet distribution and use in emergencies: A qualitative assessment. Water 2019, 11, 1121, DOI: 10.3390/w11061121
  38
  Barriers and facilitators to chlorine tablet distribution and use in emergencies: a qualitative assessment
  Mitro, Brittany; Wolfe, Marlene K.; Galeano, Mateo; Sikder, Mustafa; Gallandat, Karin; Lantagne, Daniele
  Water (Basel, Switzerland) (2019), 11 (6), 1121CODEN: WATEGH; ISSN:2073-4441. (MDPI AG)
  Chlorine tablets are commonly distributed for household water treatment in emergencies. However, confirmed use after distribution ranges widely (from 7-87%), which raises concerns about chlorine tablet effectiveness, as measured by acceptance and appropriate use. To investigate chlorine tablet effectiveness, we conducted nine key informant interviews (KIIs) on tablet distribution in emergencies in general, five KIIs on chlorine taste and odor acceptance and rejection specifically, and a literature review on chlorine taste and odor concerns. We found: (1) chlorine tablets are regarded as one of the most effective water treatment methods and are often considered appropriate in emergency response, (2) dosing confusion and taste and odor rejection are perceived as the main problems limiting effectiveness, and (3) the primary solns. suggested for these problems were social and behavioral. We recommend that social and behavioral scientists are routinely integrated into chlorine tablet programming to improve user feedback and behavioral interventions for chlorine tablet promotion in emergencies. We also suggest that more research is conducted on chlorine taste and odor rejection in vulnerable populations, and that improved guidance is developed to facilitate intra-agency coordination and select, promote, and monitor tablets appropriate for each context.
39. 39
  Crider, Y.; System-level, Automatic Chlorination in Community-managed Water Systems. Water Supply Treat. 2019, 26– 27.
  There is no corresponding record for this reference.
40. 40
  Aumeier, B. M. The Hydrothermal Solution for Decentralized Drinking Water Purification The Hydrothermal Solution for Decentralized Drinking Water Purification. Ph.D. Thesis, Rheinisch-Westfälische Technische Hochschule Aachen, Germany, 2020. DOI: 10.18154/RWTH-2020-09122 .
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  Aumeier, B. M.; Jiang, X.; Djeljadini, S.; Smeets, P.; Yüce, S.; Kazner, C.; Wessling, M. Evaluating water purification at household level in India. Desalin. Water Treat. 2017, 91, 311– 319, DOI: 10.5004/dwt.2017.20802
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  Pickering, A. J.; Crider, Y.; Amin, N.; Bauza, V.; Unicomb, L.; Davis, J.; Luby, S. P. Differences in field effectiveness and adoption between a novel automated chlorination system and household manual chlorination of drinking water in Dhaka, Bangladesh: A randomized controlled trial. PLoS One 2015, 10, e1183977 DOI: 10.1371/journal.pone.0118397
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43. 43
  Cervero-Aragó, S.; Rodríguez-Martínez, S.; Puertas-Bennasar, A.; Araujo, R. M. Effect of common drinking water disinfectants, chlorine and heat, on free Legionella and amoebae-associated Legionella. PLoS One 2015, 10, 1– 18
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  Chalmers, R. M.; Davies, A. P.; Tyler, K. Cryptosporidium. Microbiology 2019, 165, 500– 502, DOI: 10.1099/mic.0.000764
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  Adeyemo, F. E.; Singh, G.; Reddy, P.; Bux, F.; Stenström, T. A. Efficiency of chlorine and UV in the inactivation of Cryptosporidium and Giardia in wastewater. PLoS One 2019, 14, e02160400 DOI: 10.1371/journal.pone.0216040
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46. 46
  Crider, Y.; Sultana, S.; Unicomb, L.; Davis, J.; Luby, S. P.; Pickering, A. J. Can you taste it? Taste detection and acceptability thresholds for chlorine residual in drinking water in Dhaka, Bangladesh. Sci. Total Environ. 2018, 613–614, 840– 846, DOI: 10.1016/j.scitotenv.2017.09.135
  46
  Can you taste it? Taste detection and acceptability thresholds for chlorine residual in drinking water in Dhaka, Bangladesh
  Crider, Yoshika; Sultana, Sonia; Unicomb, Leanne; Davis, Jennifer; Luby, Stephen P.; Pickering, Amy J.
  Science of the Total Environment (2018), 613-614 (), 840-846CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
  Chlorination is a low-cost, effective method for drinking water treatment, but aversion to the taste or smell of chlorinated water can limit use of chlorine treatment products. Forced choice triangle tests were used to evaluate chlorine detection and acceptability thresholds for two common types of chlorine among adults in Dhaka, Bangladesh, where previous studies have found low sustained uptake of chlorine water treatment products. The median detection threshold was 0.70 mg/L (n = 25, SD = 0.57) for water dosed with liq. sodium hypochlorite (NaOCl) and 0.73 mg/L (n = 25, SD = 0.83) for water dosed with solid sodium dichloroisocyanurate (NaDCC). Median acceptability thresholds (based on user report) were 1.16 mg/L (SD = 0.70) for NaOCl and 1.26 mg/L (SD = 0.67) for NaDCC. There was no significant difference in detection or acceptability thresholds for dosing with NaOCl vs. NaDCC. Although users are willing to accept treated water in which they can detect the taste of chlorine, their acceptability limit is well below the 2.0 mg/L that chlorine water treatment products are often designed to dose. For some settings, reducing dose may increase adoption of chlorinated water while still providing effective disinfection.
47. 47
  Li, X. F.; Mitch, W. A. Drinking Water Disinfection Byproducts (DBPs) and Human Health Effects: Multidisciplinary Challenges and Opportunities. Environ. Sci. Technol. 2018, 52, 1681– 1689, DOI: 10.1021/acs.est.7b05440
  47
  Drinking Water Disinfection Byproducts (DBPs) and Human Health Effects: Multidisciplinary Challenges and Opportunities
  Li, Xing-Fang; Mitch, William A.
  Environmental Science & Technology (2018), 52 (4), 1681-1689CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  A review. While drinking water disinfection has effectively prevented waterborne diseases, an unintended consequence is the generation of disinfection byproducts (DBPs). Epidemiol. studies have consistently obsd. an assocn. between consumption of chlorinated drinking water with an increased risk of bladder cancer. Out of the >600 DBPs identified, regulations focus on a few classes, such as trihalomethanes (THMs), whose concns. were hypothesized to correlate with the DBPs driving the toxicity of disinfected waters. However, the DBPs responsible for the bladder cancer assocn. remain unclear. Utilities are switching away from a reliance on chlorination of pristine drinking water supplies to the application of new disinfectant combinations to waters impaired by wastewater effluents and algal blooms. In light of these changes in disinfection practice, this article discusses new approaches being taken by anal. chemists, engineers, toxicologists and epidemiologists to characterize the DBP classes driving disinfected water toxicity, and suggests that DBP exposure should be measured using other DBP classes in addn. to THMs.
48. 48
  Malayeri, A. H.; Mohseni, M.; Cairns, B. R.; B, J. UV Dose Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa and Viruses. IUVA News 2006, 8, 38– 45
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49. 49
  Water Research Foundation. WRF 4376: Guidance for Implementing Action Spectra Correction with Medium Pressure UV Disinfection; Water Research Foundation, 2015.
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50. 50
  Bolton, J. R.; Cotton, C. A. Ultraviolet Disinfection Handbook; American Water Works Association (AWWA), 2008.
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51. 51
  Simons, R.; Lawal, O.; Pagán, J. 2022 State of the Industry: UV-C LEDs and Their Applications. UV Solutions Mag , 2022. Available at: https://uvsolutionsmag.com/articles/2022/2022-state-of-the-industry-uv-c-leds-and-their-applications/ (accessed 18 August, 2022).
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  Wu, H. Impact of the global chip shortage on the development of in-memory chips. Nat. Commun. 2022, 13, 4055
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53. 53
  Linden, K. G.; Hull, N.; Speight, V. Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection. Acc. Chem. Res. 2019, 52, 1226– 1233, DOI: 10.1021/acs.accounts.9b00060
  53
  Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection
  Linden, Karl G.; Hull, Natalie; Speight, Vanessa
  Accounts of Chemical Research (2019), 52 (5), 1226-1233CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
  This work critically evaluated the current paradigm for water distribution system management, juxtaposing it with the potential benefits of UV irradn., to catalyze a judicial re-evaluation of current water distribution system management practices and spurring crit. research and a new way to think about secondary disinfection across distribution systems. A new model for secondary disinfection in water distribution systems using emerging germicidal UV light emitting diode (LED)-based disinfection is envisioned. UV irradn. in water treatment achieves high levels of disinfection of all pathogens and minimizes or eliminates formation of regulated disinfection byproducts. The logic for benefits and practicality of adding distributed UV treatment to assist in protecting distribution systems and water quality for human exposure is discussed. Possible UV irradn. distribution system locations are envisioned, including distribution system UV booster stations; UV in storage tanks or their inlet/outlet; LED distributed along pipe walls; small point-of-use/entry treatment systems for buildings/homes/taps; submersible swimming or rolling UV LED drones to reach problem pipes and provide shock treatment or sterilization following main breaks or repairs. UV application benefits include high effectiveness against Cl-resistant protozoa, no added disinfection byproducts, and compatibility of adding UV to existing secondary disinfection strategies for enhanced protection. Challenges and research needs are described, e.g., using UV-compatible pipe materials, implementing sensors to monitor distributed LED, managing waste heat from the LED rear surface, understanding the potential for opportunistic microorganism re-growth. Another challenge is the relatively stagnant regulatory environment in some countries to develop frameworks to evaluate and accept UV technol. in distribution systems requiring chem. secondary disinfectant. Rapid advances in UV LED research propelled growth of this field, but needs remain: understanding in-pipe biofilm behavior under UV irradn. (beneficial effects which may be lost); potential fouling of LED emission surfaces and monitoring points; providing a distributed power network to run LED. Regulators may want specific monitoring approaches and advances for real-time monitoring of microbial viability; engineers may need to develop new overall management approaches.
54. 54
  Hull, N. M.; Linden, K. G. Synergy of MS2 disinfection by sequential exposure to tailored UV wavelengths. Water Res. 2018, 143, 292– 300, DOI: 10.1016/j.watres.2018.06.017
  54
  Synergy of MS2 disinfection by sequential exposure to tailored UV wavelengths
  Hull, Natalie M.; Linden, Karl G.
  Water Research (2018), 143 (), 292-300CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
  The advantages of polychromatic UV light for viral disinfection can be optimized for disinfection using emerging tailored wavelength sources including KrCl excimer lamps and light emitting diodes (LEDs). Disinfection of the common viral surrogate MS2 bacteriophage was measured after exposure to these emerging sources and conventional low pressure (LP) mercury UV lamps in individual or sequential exposures. The first dose response for any virus (MS2) exposed to a KrCl excimer lamp is reported, showing the high efficiency of fluence-based disinfection because of increased viral susceptibility at the low wavelengths emitted by the excilamp. Sequential exposure dose responses indicated synergy from sequential exposures of LP and excimer lamps, which were competitive on an elec. basis at worst-and best-case scenarios of wall plug efficiency with current medium pressure (MP) disinfection. Best-case scenarios for elec. efficiency also showed all sequential exposures to be competitive with MP UV disinfection. Predictive models for sequential exposure dose responses were assessed to support the current feasibility of incorporating sequential UV exposures to optimize tailored wavelength viral disinfection.
55. 55
  Beck, S. E.; Hull, N. M.; Poepping, C.; Linden, K. G. Wavelength-Dependent Damage to Adenoviral Proteins Across the Germicidal UV Spectrum. Environ. Sci. Technol. 2018, 52, 223– 229, DOI: 10.1021/acs.est.7b04602
  55
  Wavelength-Dependent Damage to Adenoviral Proteins Across the Germicidal UV Spectrum
  Beck, Sara E.; Hull, Natalie M.; Poepping, Christopher; Linden, Karl G.
  Environmental Science & Technology (2018), 52 (1), 223-229CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  Adenovirus, a waterborne pathogen responsible for causing bronchitis, pneumonia, and gastrointestinal infections, is highly resistant to UV disinfection and therefore drives the virus disinfection regulations set by the U. S. Environmental Protection Agency. Polychromatic UV irradn. has been shown to be more effective at inactivating adenovirus and other viruses than traditional monochromatic irradn. emitted at 254 nm; the enhanced efficacy has been attributed to UV-induced damage to viral proteins. This research shows UV-induced damage to adenoviral proteins across the germicidal UV spectrum at wavelength intervals between 200 and 300 nm. A deuterium lamp with bandpass filters and UV light emitting diodes (UV LEDs) isolated wavelengths in approx. 10 nm intervals. SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) and image densitometry were used to detect signatures for the hexon, penton, fiber, minor capsid, and core proteins. The greatest loss of protein signature, indicating damage to viral proteins, occurred below 240 nm. Hexon and penton proteins exposed to a dose of 28 mJ/cm2 emitted at 214 nm were approx. four times as sensitive, and fiber proteins approx. three times as sensitive, as those exposed to a dose of 50 mJ/cm2 emitted at 254 nm. At 220 nm, a dose of 38 mJ/cm2 reduced the hexon and penton protein quantities to approx. 33% and 31% of the original amt., resp. In contrast, a much higher dose of 400 mJ/cm2 emitted at 261 nm, and 278 nm reduced the original protein quantity to between 66 - 89%, and 80 - 93% resp. No significant damage was seen by 400 mJ/cm2 at 254 nm. This research directly correlates enhanced inactivation at low wavelengths with adenoviral protein damage at those wavelengths, adding fundamental insight into the mechanisms of inactivation of polychromatic germicidal UV irradn. for improving UV water disinfection.
56. 56
  Jarvis, P.; Autin, O.; Goslan, E. H.; Hassard, F. Application of Ultraviolet Light-Emitting Diodes (UV-LED) to Full-Scale Drinking-Water Disinfection. Water 2019, 11, 1894, DOI: 10.3390/w11091894
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57. 57
  Hendrickson, C.; Oremo, J.; Akello, O. O.; Bunde, S.; Rayola, I.; Akello, D.; Akwiri, D.; Park, S. J.; Dorevitch, S. Decentralized solar-powered drinking water ozonation in Western Kenya: an evaluation of disinfection efficacy. Gates Open Res. 2020, 4, 56, DOI: 10.12688/gatesopenres.13138.1
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58. 58
  Kumpel, E.; Nelson, K. L. Intermittent Water Supply: Prevalence, Practice, and Microbial Water Quality. Environ. Sci. Technol. 2016, 50, 542– 553, DOI: 10.1021/acs.est.5b03973
  58
  Intermittent Water Supply: Prevalence, Practice, and Microbial Water Quality
  Kumpel, Emily; Nelson, Kara L.
  Environmental Science & Technology (2016), 50 (2), 542-553CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  A review is given. Intermittent water supplies (IWS), in which water is provided through pipes for only limited durations, serve ≥300 million people around the world. However, providing water intermittently can compromise water quality in the distribution system. In IWS systems, the pipes do not supply water for periods of time, supply periods are shortened, and pipes experience regular flow restarting and draining. These unique behaviors affect distribution system water quality in ways that are different than during normal operations in continuous water supplies (CWS). A better understanding of the influence of IWS on mechanisms causing contamination can help lead to incremental steps that protect water quality and minimize health risks. This review examines the status and nature of IWS practices throughout the world, the evidence of the effect of IWS on water quality, and how the typical contexts in which IWS systems often exist-low-income countries with under-resourced utilities and inadequate sanitation infrastructure-can exacerbate mechanisms causing contamination. We then highlight knowledge gaps for further research to improve our understanding of water quality in IWS.
59. 59
  Lantagne, D.; Meierhofer, R.; Allgood, G.; McGuigan, K. G.; Quick, R. Comment on “Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World. Environ. Sci. Technol. 2009, 43, 968– 969, DOI: 10.1021/es802252c
  59
  Comment on "Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World"
  Lantagne, Daniele; Meierhofer, Regula; Allgood, Greg; McGuigan, K. G.; Quick, Robert
  Environmental Science & Technology (2009), 43 (3), 968-969CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  A polemic to M.Sobsey, et al., ibid., 2008, concerning flaws in a proposed ranking system for point-of-use household drinking water filtration systems which have the potential to provide sustained access to safe drinking water in developing areas is given. Identified flaws include: incomplete, vague definitions of ranking system criteria making it subject to bias; scores assigned were drawn from insufficient evidence; and omission of key sustainability criteria (consumer preference, economic considerations, cultural practices, local water quality). Also, a decision tree to select appropriate household water treatment and safe storage option for given circumstances is significantly more complex than presented by Sobsey, et al.
60. 60
  Theobald, S.; Brandes, N.; Gyapong, M.; El-Saharty, S.; Proctor, E.; Diaz, T.; Wanji, S.; Elloker, S.; Raven, J.; Elsey, H. Implementation research: new imperatives and opportunities in global health. Lancet 2018, 392, 2214– 2228, DOI: 10.1016/S0140-6736(18)32205-0
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  Rosenthal, J.; Arku, R. E.; Baumgartner, J.; Brown, J.; Clasen, T.; Eisenberg, J. N.; Hovmand, P.; Jagger, P.; Luke, D. A.; Quinn, A. Systems science approaches for global environmental health research: Enhancing intervention design and implementation for household air pollution (hap) and water, sanitation, and hygiene (wash) programs. Environ. Health Perspect. 2020, 128, 1– 12, DOI: 10.1289/ehp7010
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62. 62
  Rosenthal, J.; Arku, R. E.; Baumgartner, J.; Brown, J.; Clasen, T.; Eisenberg, J. N.; Hovmand, P.; Jagger, P.; Luke, D. A.; Quinn, A. Systems Science Approaches for Global Environmental Health Research: Enhancing Intervention Design and Implementation for Household Air Pollution (HAP) and Water, Sanitation, and Hygiene (WASH) Programs. Environ. Health Perspect. 2020, 128, 1– 12, DOI: 10.1289/ehp7010
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63. 63
  Currie, D. J.; Smith, C.; Jagals, P. The application of system dynamics modelling to environmental health decision-making and policy - A scoping review. BMC Public Health 2018, 18, 402– 411, DOI: 10.1186/s12889-018-5318-8
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  Setty, K.; Cronk, R.; George, S.; Anderson, D.; O’Flaherty, G.; Bartram, J. Adapting translational research methods to water, sanitation, and hygiene. Int. J. Environ. Res. Public Health 2019, 16, 4049, DOI: 10.3390/ijerph16204049
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65. 65
  Rosenthal, J.; Balakrishnan, K.; Bruce, N.; Chambers, D.; Graham, J.; Jack, D.; Kline, L.; Masera, O.; Mehta, S.; Mercado, I. R. Implementation Science to Accelerate Clean Cooking for Public Health. Environ. Health Perspect. 2017, 125, A3– A7, DOI: 10.1289/ehp1018
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66. 66
  Freeman, M. C.; Garn, J. V.; Sclar, G. D.; Boisson, S.; Medlicott, K.; Alexander, K. T.; Penakalapati, G.; Anderson, D.; Mahtani, A. G.; Grimes, J. E. The impact of sanitation on infectious disease and nutritional status: A systematic review and meta-analysis. Int. J. Hyg. Environ. Health 2017, 220, 928– 949, DOI: 10.1016/j.ijheh.2017.05.007
  66
  The impact of sanitation on infectious disease and nutritional status: A systematic review and meta-analysis
  Freeman Matthew C; Garn Joshua V; Sclar Gloria D; Alexander Kelly T; Penakalapati Gauthami; Anderson Darcy; Mahtani Amrita G; Boisson Sophie; Medlicott Kate; Grimes Jack E T; Rehfuess Eva A; Clasen Thomas F
  International journal of hygiene and environmental health (2017), 220 (6), 928-949 ISSN:.
  BACKGROUND: Sanitation aims to sequester human feces and prevent exposure to fecal pathogens. More than 2.4 billion people worldwide lack access to improved sanitation facilities and almost one billion practice open defecation. We undertook systematic reviews and meta-analyses to compile the most recent evidence on the impact of sanitation on diarrhea, soil-transmitted helminth (STH) infections, trachoma, schistosomiasis, and nutritional status assessed using anthropometry. METHODS AND FINDINGS: We updated previously published reviews by following their search strategy and eligibility criteria. We searched from the previous review's end date to December 31, 2015. We conducted meta-analyses to estimate pooled measures of effect using random-effects models and conducted subgroup analyses to assess impact of different levels of sanitation services and to explore sources of heterogeneity. We assessed risk of bias and quality of the evidence from intervention studies using the Liverpool Quality Appraisal Tool (LQAT) and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach, respectively. A total of 171 studies met the review's inclusion criteria, including 64 studies not included in the previous reviews. Overall, the evidence suggests that sanitation is protective against diarrhea, active trachoma, some STH infections, schistosomiasis, and height-for-age, with no protective effect for other anthropometric outcomes. The evidence was generally of poor quality, heterogeneity was high, and GRADE scores ranged from very low to high. CONCLUSIONS: This review confirms positive impacts of sanitation on aspects of health. Evidence gaps remain and point to the need for research that rigorously describes sanitation implementation and type of sanitation interventions.
67. 67
  Prüss-Ustün, A.; Wolf, J.; Bartram, J.; Clasen, T.; Cumming, O.; Freeman, M. C.; Gordon, B.; Hunter, P. R.; Medlicott, K.; Johnston, R. Burden of disease from inadequate water, sanitation and hygiene for selected adverse health outcomes: An updated analysis with a focus on low- and middle-income countries. Int. J. Hyg. Environ. Health 2019, 222, 765– 777, DOI: 10.1016/j.ijheh.2019.05.004
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  Wolf, J.; Hunter, P. R.; Freeman, M. C.; Cumming, O.; Clasen, T.; Bartram, J.; Higgins, J. P. T.; Johnston, R.; Medlicott, K.; Boisson, S. Impact of drinking water, sanitation and handwashing with soap on childhood diarrhoeal disease: updated meta-analysis and meta-regression. Trop. Med. Int. Heal. 2018, 23, 508– 525, DOI: 10.1111/tmi.13051
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  Scheirer, M. A.; Dearing, J. W. An agenda for research on the sustainability of Public Health Programs. Am. J. Public Health 2011, 101, 2059– 2067, DOI: 10.2105/AJPH.2011.300193
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  Wiltsey Stirman, S.; Kimberly, J.; Cook, N.; Calloway, A.; Castro, F.; Charns, M. The sustainability of new programs and innovations: A review of the empirical literature and recommendations for future research. Implement. Sci. 2012, 7, 17– 19, DOI: 10.1186/1748-5908-7-17
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  Johnson, A. M.; Moore, J. E.; Chambers, D. A.; Rup, J.; Dinyarian, C.; Straus, S. E. How do researchers conceptualize and plan for the sustainability of their NIH R01 implementation projects?. Implement. Sci. 2019, 14, 50– 59, DOI: 10.1186/s13012-019-0895-1
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  Proctor, E.; Luke, D.; Calhoun, A.; McMillen, C.; Brownson, R.; McCrary, S.; Padek, M. Sustainability of evidence-based healthcare: Research agenda, methodological advances, and infrastructure support. Implement. Sci. 2015, 10, 88, DOI: 10.1186/s13012-015-0274-5
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  Glasgow, R. E.; Vogt, T. M.; Boles, S. M.; Glasgow, E. Evaluating the Public Health Impact of Health Promotion Interventions: The RE-AIM Framework. Am J Public Health 1999, 89, 1322– 1327, DOI: 10.2105/ajph.89.9.1322
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  Shelton, R. C.; Chambers, D. A.; Glasgow, R. E. An Extension of RE-AIM to Enhance Sustainability: Addressing Dynamic Context and Promoting Health Equity Over Time. Front. Public Heal. 2020, 8, 1– 8, DOI: 10.3389/fpubh.2020.00134
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  Braveman, P. A New Definition Of Health Equity To Guide Future Efforts And Measure Progress, Heatlh Affairs , June 22, 2017, DOI: 10.1377/FOREFRONT.20170622.060710 .
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  Proctor, E. K.; Powell, B. J.; McMillen, J. C. Implementation strategies: Recommendations for specifying and reporting. Implement. Sci. 2013, 8, 139, DOI: 10.1186/1748-5908-8-139
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  Abbott, M. L.; McKinney, J. Understanding and Applying Research Design; John Wiley and Sons Inc, 2013.
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  Guest, G.; Namey, E.; Chen, M. A simple method to assess and report thematic saturation in qualitative research. PLoS One 2020, 15, e02320766 DOI: 10.1371/journal.pone.0232076
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  Drisko, J. W.; Maschi, T. Qualitative Content Analysis. In Content Analysis; Oxford University Press, 2015, pp 81– 120. DOI: 10.1093/acprof:oso/9780190215491.003.0004 .
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  Barbrook-Johnson, P.; Penn, A. S. Systems Mapping How to Build and Use Causal Models of Systems. Palgrave Macmillan; Springer Nature, 2022. DOI: 10.1007/978-3-031-01919-7_2 .
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81. 81
  Cherukumilli, K.; Bain, R.; Chen, Y.; Pickering, A. J. Estimating the Global Target Market for Passive Chlorination. Environ. Sci. Technol. Lett. 2023, 10, 105– 110, DOI: 10.1021/acs.estlett.2c00781
  81
  Estimating the Global Target Market for Passive Chlorination
  Cherukumilli, Katya; Bain, Robert; Chen, Yiru; Pickering, Amy J.
  Environmental Science & Technology Letters (2023), 10 (1), 105-110CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
  Deploying passive (in-line) chlorinators is one strategy for improving access to microbially safe drinking water without requiring electricity or daily user input. Using Joint Monitoring Program data, we calc. the population in low- and middle-income countries (n = 135 LMICs) using drinking water sources that are compatible (piped water and kiosks) or potentially compatible (packaged and/or delivered water, rainwater, boreholes and/or tube wells, and protected springs) with passive chlorinators. Leveraging water quality data from the Multiple Indicator Cluster Surveys (n = 37 LMICs), we est. that 2.32 [95% confidence interval (CI): 2.19, 2.46] billion people use microbially contaminated water sources that are compatible [1.51 (1.42, 1.60) billion] or potentially compatible [817 (776, 858) million] with passive chlorinators. The largest target market for passive chlorinators is in South Asia [551 (532, 571) million rural users and 401 (384, 417) million urban users], where >77% of compatible drinking water sources are contaminated. However, self-reported household water treatment practices (n = 54 LMICs) indicate that chlorination is more common in the African and Latin American regions, suggesting passive chlorination would have higher acceptance in these regions than in Asia. Reaching the full potential of passive chlorinators will require establishing compatibility of technologies with hand pump chlorination and identifying financially viable implementation models.
82. 82
  Evidence Action’s In-Line Chlorination Program─General Support (July 2022) | GiveWell. Available at: https://www.givewell.org/research/grants/evidence-action-ILC-july-2022 (accessed 17 August, 2023).
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  Nowicki, S.; Koehler, J.; Charles, K. J. Including water quality monitoring in rural water services: why safe water requires challenging the quantity versus quality dichotomy. npj Clean Water 2020, 3, 14– 19, DOI: 10.1038/s41545-020-0062-x
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  Thomson, P. Remote monitoring of rural water systems: A pathway to improved performance and sustainability?. Wiley Interdiscip. Rev. Water 2021, 8, 1– 14, DOI: 10.1002/wat2.1502
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  Hope, R.; Thomson, P.; Koehler, J.; Foster, T. Rethinking the economics of rural water in Africa. Oxford Rev. Econ. Policy 2020, 36, 171– 190, DOI: 10.1093/oxrep/grz036
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  Oxfam. Oxfam Water Supply Scheme for Emergencies Instruction Manual for Coagulation and Disinfection Equipm; Oxfam: Oxford, UK, 2001; Vol. 18.
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  Orner, K. D.; Calvo, A.; Zhang, J.; Mihelcic, J. R. Effectiveness of in-line chlorination in a developing world gravity-flow water supply. Waterlines 2017, 36, 167– 182, DOI: 10.3362/1756-3488.16-00016
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  Powers, J. E.; McMurry, C.; Gannon, S.; Drolet, A.; Oremo, J.; Klein, L.; Crider, Y.; Davis, J.; Pickering, A. J. Design, performance, and demand for a novel in-line chlorine doser to increase safe water access. npj Clean Water 2021, 4, 4, DOI: 10.1038/s41545-020-00091-1
  88
  Design, performance, and demand for a novel in-line chlorine doser to increase safe water access
  Powers, Julie E.; McMurry, Cynthia; Gannon, Sarah; Drolet, Adam; Oremo, Jared; Klein, Linden; Crider, Yoshika; Davis, Jennifer; Pickering, Amy J.
  npj Clean Water (2021), 4 (1), 4CODEN: CWLACV; ISSN:2059-7037. (Nature Research)
  Financially sustainable strategies are needed to increase access to safe drinking water in low-income settings. We designed a novel in-line chlorine doser that employs the Venturi principle to automatically add liq. chlorine at the point of water collection (tap outflows). The Venturi does not require electricity or moving parts, and users do not have to change the way they typically collect water. We field-tested the Venturi and assessed its tech. performance and sales viability at water kiosks in Kisumu County, Kenya. We offered kiosk owners 6-mo service packages to lease or lease-to-own the device; 27% of kiosks given a sales pitch committed to a service package. All but one kiosk paid in full during the 6-mo service period and more than two-thirds purchased the device with payments totaling >$250 USD per kiosk. Kiosk customers could choose to purchase chlorinated or unchlorinated water from sep. taps; 66% reported buying chlorinated water. Kiosk taps fitted with the Venturi had detectable free chlorine residual 97.6% of the time. The tech. performance of the Venturi and effective demand from kiosks indicate high potential for the Venturi to increase safe water access in low-income communities.
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Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsestwater.3c00779.
- Terms of reference of the community of practice on decentralized chlorine use (PDF)
- Conceptual visualization of key categories and factors (PDF)
- ew3c00779_si_001.pdf (390.43 kb)
- ew3c00779_si_002.pdf (279.06 kb)
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Reinforcing Feedbacks for Sustainable Implementation of Rural Drinking-Water Treatment TechnologyClick to copy article linkArticle link copied!

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Synopsis

1. Introduction

2. Methods

2.1. An Implementation Science Framing

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2.2. Key Informant Interviews

2.3. Content Analysis and Systems Mapping

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3. Results and Discussion

3.1. Evidence of Health Improvements Catalyzes Collaboration Around a Shared Purpose

3.2. Communication and Service Delivery Approaches Drive Acceptability

3.3. Fit-For-Purpose Technology Mitigates Implementation and Maintenance Barriers

3.4. Leverage Points for Sustainable Rural Water Treatment

4. Conclusions

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Reinforcing Feedbacks for Sustainable Implementation of Rural Drinking-Water Treatment Technology
Click to copy article linkArticle link copied!