WASH and drinking water quality considerations in schools in reflection of the sustainable development goals – a review

A large proportion of communicable diseases in the world are related to contaminated drinking water. Contaminated drinking water causes morbidity and mortality worldwide, especially in low- and middle-income countries (Shilunga et al. 2018; Bain et al. 2021; Bolatova et al. 2021; Morgan et al. 2021; Ahmed et al. 2022). WASH refers to the provision of safe drinking water, effective disposal of faeces, and the promotion of healthy behaviour among impacted individuals (Antwi-agyei et al. 2017; World Health Organisation [WHO] 2017; Cronk et al. 2021; Williams et al. 2021). Safe WASH facilities are critical factors of human dignity and good health, and quality of life (Agol & Harvey 2018; Ngwenya et al. 2018; Morgan et al. 2021; Bolatova et al. 2021).

Drinking water quality is an essential part of WASH provision in schools (Scheili et al. 2015; Wen et al. 2020; Anthonj et al. 2021; Bolatova et al. 2021; Morgan et al. 2021). To ensure good health habits and a high quality of life for learners in school, it is critical that schools provide a favourable environment that includes safe WASH facilities (Maroneze et al. 2014; Bolatova et al. 2021). Since learners spend a significant amount of time each day on the school premises, adequate WASH facilities in schools are crucial for their well-being (Anthonj et al. 2021). Additionally, learners spend more of their formative years in school, which means that giving them basic access to sustainable WASH is not only necessary at home but also in their schools (WHO & the United Nations Children's Fund [UNICEF] 2018). The provision of safe WASH facilities in schools is linked with the achievement of sustainable development goals (SGDs) in particular, SDG 6, (Antwi-agyei et al. 2017). The global initiative aimed at achieving SDG 6 by 2030 has expanded beyond the household to institutional settings which includes schools. Global education for all approaches has reinforced this by emphasizing how WASH in schools increases access to education and learning outcomes, particularly for girls, by establishing a safe and equal learning environment for everyone (WHO & UNICEF 2018, 2021). Safe WASH facilities include access to safe drinking water for all and is among the first target of SDG 6 (Hung et al. 2020). When providing safe WASH facilities, one of the environmental health factors that should be considered is drinking water quality. The provision of safe drinking water is associated with global indicator 6.1.1, which means the use of well-managed water services (Bain et al. 2021).

Despite remarkable progress since the declaration of SDG 6 in 2015, ensuring access of all to safe drinking water quality worldwide still remains a concern (Nanseu-njiki et al. 2019; Winter et al. 2021). Drinking water quality continues to be a global issue (Addisie 2022), and this might affect the world's ambition to achieve universal access to safe drinking water by 2030 (Scheili et al. 2015; Wen et al. 2020; Anthonj et al. 2021; Bolatova et al. 2021). There is a consensus on a lack of capacity in the developing world to achieve the SDGs, among them, SDG 6 on ensuring the availability and sustainable management of water and sanitation for all (Nanseu-njiki et al. 2019). Access to clean and safe drinking water quality is a basic human need and a basic human right. However, utilization of contaminated water is increasing particularly in developing countries (Akram 2020). Because it is necessary to make sure that learners have access to safe drinking water at school, monitoring drinking water quality is essential during WASH assessments in schools. This is to determine whether water is safe for consumption and hygienic purposes (Scheili et al. 2015; Wen et al. 2020; Anthonj et al. 2021; Bolatova et al. 2021; Morgan et al. 2021). In addition, the assessment of drinking water quality in schools, specifically, microbial quality, is critical since it is linked to the prevention of infectious diseases. However, it is unclear whether water quality is always assessed as part of WASH in schools.

The purpose of this article is to examine through systematic literature review, the consideration of water quality aspects during the assessment of WASH in schools since the declaration of the SDGs. This study should stimulate a discussion on the subject to highlight the importance of providing safe WASH in schools in all of its forms focusing on the three objectives which include; to determine if drinking water quality is included during the assessment of WASH in schools, to identify the drinking water quality parameters that are mostly included during the assessment of WASH in schools, and to identify if there are any gaps that need to be addressed during the assessment of WASH in schools.

A systematic search which included data selection, screening, eligibility, and the final selection of journal articles was performed. Three online databases (ScienceDirect, ProQuest and Google Scholar) and manual search (Google, Bing, and Yahoo) were used to identify studies that reported assessment of WASH facilities in schools. The literature search was restricted to articles and papers published in English. The search strategy included the keywords ‘Assessment of water, sanitation, and hygiene facilities in schools,’ or ‘WASH’ in ‘schools’ or ‘WaSH in schools’ or ‘water, sanitation and hygiene’ or ‘drinking water quality in schools’ or ‘drinking water quality’ or ‘drinking water and schools.’ The data were firstly selected based on title and abstract (Pahlevan-sharif et al. 2019), thereafter, full-text articles were downloaded for further screening. The duplications of the articles and papers from all search engines were removed (Pahlevan-sharif et al. 2019; Anthonj et al. 2020). The total number of articles and papers after removing duplication was 1,430 (n = 1,430) as presented in Figure 1.

Prior to conducting the full review of selected studies, further screening was conducted. Six hundred and sixty studies were screened to avoid bias (Pahlevan-sharif et al. 2019). Further screening was conducted considering inclusion and exclusion criteria (Table 1). Only journal articles and papers were included in this process. Guidelines, manuals, news stories, and blog posts were not included.

The authors independently appraised the included studies for methodological quality using the upgraded version of Assessment of Multiple Systematic Reviews (AMSTAR) which is called AMSTAR 2 (Shea et al. 2017). The AMSTAR 2 appraisal checklist was adopted (https://amstar.ca/). A rating of high, moderate, low, and critically low was awarded to each study according to the number of ‘yes’, ‘can't tell’, and ‘no’ responses (Table 2). Where high means No or one non-critical weakness: the systematic review provides an accurate and comprehensive summary of the results of the available studies that address the question of interest. Critically low indicates that the review has numerous significant faults or omissions, making it unreliable for giving a precise and thorough summary of the studies that are currently available (Perry et al. 2021).

Using a standardized checklist, data related to study characteristics were extracted. Data were collected from studies that met the inclusion criteria. Data on WASH variables, drinking water quality information, and drinking water quality parameters were gathered. Extracted data were manually entered into a Microsoft Excel database. The documents were coded into two cycles for the following: the consideration of drinking water quality during the assessment and drinking water variables that were included in the selected studies. Thereafter, statistical analysis in terms of percentage was calculated.

A total of 2, 560 studies were identified, but after de-duplication, only 1,430 remained (Figure 1). After title and abstract screening, 356 studies were included for full-text screening. Finally, 75 studies were identified for inclusion. Most studies were excluded because they did not meet the criteria for inclusion based on full-text review.

The 75 studies that were included in the analysis were classified by country, subregion, and country income level as determined by the World Bank (https://datatopics.worldbank.org/world-development-indicators/the-world-by-income-and-region.html) (Tables 3 and 4). Most studies were carried out in the sub-Saharan Africa region (49%) in lower middle-income countries.

Table 3

Identified studies that included drinking water quality

No. .	Author, Year .	Country .	Country income level .	Region .	WASH variables .	Drinking water quality variable .
1.	Ahmed et al. (2020)	Pakistan	Lower middle-income	South Asia	WASH provision Drinking water quality	Microbial:E. coli, Shigella, Salmonella, Vibrio cholerae, Campylobacter, and Rotavirus.
2.	Ahmed et al. (2022)	Pakistan	Lower middle-income	South Asia	WASH provision	Physical: pH, turbidity, temperature, conductivity, and hardness Chemical: F−, TDS, pH, ⁠, Cl−, As, Cd, Pb, DO, Fe, Mn, and ⁠. Microbial: Faecal coliforms.
3.	Al-saleh (1996)	Saudi Arabia	High income	Middle East & North Africa	Water quality analysis	Chemical: Al, Be, Cd, Co, Cr, Cu, Fe, Mn, MO, Ni, Si, Sr, V, and Zn.
4.	Cronk et al. (2021)	Ethiopia, Ghana, Honduras, India, Kenya, Malawi, Mali, Mozambique, Niger, Rwanda, Tanzania, Uganda, Zambia, and Zimbabwe.	Lower middle-income, low income	Sub-Saharan Africa; Latin America & Caribbean; South Asia	WASH facilities	Microbial:E. coli
5.	Bah et al. (2022)	Guinea	Low income	Sub-Saharan Africa	WASH facilities and practices	Physical: Water quality made their choices mainly in terms of the clarity of the water, i.e., if the water is clear, it was considered drinkable.
6.	Bolatova et al. (2021)	Kazakhstan	Upper middle-income	Europe & Central Asia	WASH provision	Physical: Turbidity, colour, odour, and pH. Chemical: Fe. Microbial: Total coliforms and faecal coliforms.
7.	Banu et al. (2018)	Ghana	Lower middle-income	Sub-Saharan Africa	Drinking water quality	Microbial: Heterotrophic bacteria, Pseudomonas, and total coliforms.
8.	Bouchard et al. (2018)	Canada.	High income	North America	Drinking water quality	Chemical: Mn, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb.
9.	Bouchard et al. (2011)	Canada	High income	North America	Drinking water quality.	Chemical: Mn, Pb, Fe, As, Zn, and Cu.
10.	Buajitti et al. (2021)	Canada	High income	North America	Drinking water quality.	Chemical: Pb.
11.	Cradock et al. (2019)	United States of America (USA)	High income	North America	Drinking water quality, availability, and education- related practices.	Microbial: Bacteria and coliforms (no specific details provided).
12.	Ekenga et al. (2018)	USA	High income	North America	Drinking water analysis	Chemical: Pb.
13.	Hood et al. (2014)	USA	High income	North America	Drinking water availability and water quality.	Physical: Water analysis was based on physical appearance of drinking fountains. Chemical: Pb. Microbial: Bacteria (name not specified).
14.	Hossain et al. (2022)	Bangladesh	Lower middle-income	South Asia	Drinking water quality.	Physical: pH and salinity. Chemical: DO, NH3, ⁠, ⁠, and ⁠. Microbial:E. coli and total coliforms.
15.	Hu et al. (2021)	China	Upper middle-income	East Asia & Pacific	Drinking water quality.	Physical: Turbidity. Chemical: FRC and COD. Microbial: CFU.
16.	Huang et al. (2018)	China	Upper middle-income	East Asia & Pacific	Drinking water quality.	Physical: Conductivity and hardness. Chemical: Ca+2, Mn, and ⁠.
17.	Hung et al. (2020)	Vietnam	Lower middle-income	East Asia & Pacific	Drinking water quality.	Physical: Colour, taste, odour, turbidity, pH, and hardness. Chemical:⁠, ⁠, ⁠, Fe, KMnO₄, Cl-, Mn, ⁠, As. Microbial: Total coliforms, and E. coli.
18.	Alam & Mukarrom (2022)	Bangladesh	Lower middle-income	South Asia	Drinking water quality	Microbial: Total coliforms and faecal coliforms
19.	Borges-pedro et al. (2018)	Brazil	Upper middle-income	Latin America & Caribbean	WASH services	Microbial:E. coli and total coliforms.
20.	Khan et al. (2011)	Bangladesh	Lower middle-income	South Asia	Drinking water quality	Chemical: Mn and As.
21.	Lobo et al. (2022)	USA	High income	North America	Drinking water quality	Chemical: Pb.
22.	Machado et al. (2022)	Guinea-Bissau	Low income	Sub-Saharan Africa	Drinking water quality	Physical: Conductivity, DO, colour, and pH Chemical:⁠, ⁠, ⁠, Al, As, Cu, Cr, CN − , and Fe. Microbial: Faecal coliforms and intestinal enterococci.
23.	Samie et al. (2011)	South Africa	Upper middle-income	Sub-Saharan Africa	Drinking water quality	Microbial: Faecal coliforms, total coliform, heterotrophic bacteria.
24.	Meschede et al. (2018)	Brazil,	Upper middle-income	Latin America & Caribbean	Drinking water quality	Physical: pH, turbidity, conductivity, and alkalinity. Microbial: Total coliform, E. coli, heterotrophic bacteria, and parasites. Chemical: Anions and trace elements (names not specified).
25.	Moreno et al. (2021)	USA	High income	North America	Drinking water access	Chemical: Pb.
26.	Morgan et al. (2021)	Mozambique and Uganda	Low income	Sub-Saharan Africa	Drinking water quality	Microbial:E. coli.
27.	Patel et al. (2011)	USA	High income	North America	Availability and consumption of water	Chemical: Pb
28.	Rahman & Hashem (2019)	Bangladesh	Low income	Sub-Saharan Africa	Drinking water quality	Chemical: As, Fe and Cl-
29.	Ribeiro et al. (2018)	Brazil	Upper middle-income	Latin America & Caribbean	Drinking water quality	Physical: Turbidity. Chemical: FRC. Microbial:E. coli and faecal coliforms.
30.	Sangalang et al. (2022)	Philippines	Lower middle-income	East Asia & Pacific	WASH facilities and hygiene practices.	Microbial: Total coliforms and E. coli.
31.	Yani et al. (2021)	Palu, Indonesia	Lower middle-income	East Asia & Pacific	Drinking water quality	Chemical: F−.
32.	Kouamé et al. (2021)	Côte d'Ivoire	Lower middle-income	Sub-Saharan Africa	WASH accessibility	Microbial:E. coli and total coliforms.

No. .	Author, Year .	Country .	Country income level .	Region .	WASH variables .	Drinking water quality variable .
1.	Ahmed et al. (2020)	Pakistan	Lower middle-income	South Asia	WASH provision Drinking water quality	Microbial:E. coli, Shigella, Salmonella, Vibrio cholerae, Campylobacter, and Rotavirus.
2.	Ahmed et al. (2022)	Pakistan	Lower middle-income	South Asia	WASH provision	Physical: pH, turbidity, temperature, conductivity, and hardness Chemical: F−, TDS, pH, ⁠, Cl−, As, Cd, Pb, DO, Fe, Mn, and ⁠. Microbial: Faecal coliforms.
3.	Al-saleh (1996)	Saudi Arabia	High income	Middle East & North Africa	Water quality analysis	Chemical: Al, Be, Cd, Co, Cr, Cu, Fe, Mn, MO, Ni, Si, Sr, V, and Zn.
4.	Cronk et al. (2021)	Ethiopia, Ghana, Honduras, India, Kenya, Malawi, Mali, Mozambique, Niger, Rwanda, Tanzania, Uganda, Zambia, and Zimbabwe.	Lower middle-income, low income	Sub-Saharan Africa; Latin America & Caribbean; South Asia	WASH facilities	Microbial:E. coli
5.	Bah et al. (2022)	Guinea	Low income	Sub-Saharan Africa	WASH facilities and practices	Physical: Water quality made their choices mainly in terms of the clarity of the water, i.e., if the water is clear, it was considered drinkable.
6.	Bolatova et al. (2021)	Kazakhstan	Upper middle-income	Europe & Central Asia	WASH provision	Physical: Turbidity, colour, odour, and pH. Chemical: Fe. Microbial: Total coliforms and faecal coliforms.
7.	Banu et al. (2018)	Ghana	Lower middle-income	Sub-Saharan Africa	Drinking water quality	Microbial: Heterotrophic bacteria, Pseudomonas, and total coliforms.
8.	Bouchard et al. (2018)	Canada.	High income	North America	Drinking water quality	Chemical: Mn, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb.
9.	Bouchard et al. (2011)	Canada	High income	North America	Drinking water quality.	Chemical: Mn, Pb, Fe, As, Zn, and Cu.
10.	Buajitti et al. (2021)	Canada	High income	North America	Drinking water quality.	Chemical: Pb.
11.	Cradock et al. (2019)	United States of America (USA)	High income	North America	Drinking water quality, availability, and education- related practices.	Microbial: Bacteria and coliforms (no specific details provided).
12.	Ekenga et al. (2018)	USA	High income	North America	Drinking water analysis	Chemical: Pb.
13.	Hood et al. (2014)	USA	High income	North America	Drinking water availability and water quality.	Physical: Water analysis was based on physical appearance of drinking fountains. Chemical: Pb. Microbial: Bacteria (name not specified).
14.	Hossain et al. (2022)	Bangladesh	Lower middle-income	South Asia	Drinking water quality.	Physical: pH and salinity. Chemical: DO, NH3, ⁠, ⁠, and ⁠. Microbial:E. coli and total coliforms.
15.	Hu et al. (2021)	China	Upper middle-income	East Asia & Pacific	Drinking water quality.	Physical: Turbidity. Chemical: FRC and COD. Microbial: CFU.
16.	Huang et al. (2018)	China	Upper middle-income	East Asia & Pacific	Drinking water quality.	Physical: Conductivity and hardness. Chemical: Ca+2, Mn, and ⁠.
17.	Hung et al. (2020)	Vietnam	Lower middle-income	East Asia & Pacific	Drinking water quality.	Physical: Colour, taste, odour, turbidity, pH, and hardness. Chemical:⁠, ⁠, ⁠, Fe, KMnO₄, Cl-, Mn, ⁠, As. Microbial: Total coliforms, and E. coli.
18.	Alam & Mukarrom (2022)	Bangladesh	Lower middle-income	South Asia	Drinking water quality	Microbial: Total coliforms and faecal coliforms
19.	Borges-pedro et al. (2018)	Brazil	Upper middle-income	Latin America & Caribbean	WASH services	Microbial:E. coli and total coliforms.
20.	Khan et al. (2011)	Bangladesh	Lower middle-income	South Asia	Drinking water quality	Chemical: Mn and As.
21.	Lobo et al. (2022)	USA	High income	North America	Drinking water quality	Chemical: Pb.
22.	Machado et al. (2022)	Guinea-Bissau	Low income	Sub-Saharan Africa	Drinking water quality	Physical: Conductivity, DO, colour, and pH Chemical:⁠, ⁠, ⁠, Al, As, Cu, Cr, CN − , and Fe. Microbial: Faecal coliforms and intestinal enterococci.
23.	Samie et al. (2011)	South Africa	Upper middle-income	Sub-Saharan Africa	Drinking water quality	Microbial: Faecal coliforms, total coliform, heterotrophic bacteria.
24.	Meschede et al. (2018)	Brazil,	Upper middle-income	Latin America & Caribbean	Drinking water quality	Physical: pH, turbidity, conductivity, and alkalinity. Microbial: Total coliform, E. coli, heterotrophic bacteria, and parasites. Chemical: Anions and trace elements (names not specified).
25.	Moreno et al. (2021)	USA	High income	North America	Drinking water access	Chemical: Pb.
26.	Morgan et al. (2021)	Mozambique and Uganda	Low income	Sub-Saharan Africa	Drinking water quality	Microbial:E. coli.
27.	Patel et al. (2011)	USA	High income	North America	Availability and consumption of water	Chemical: Pb
28.	Rahman & Hashem (2019)	Bangladesh	Low income	Sub-Saharan Africa	Drinking water quality	Chemical: As, Fe and Cl-
29.	Ribeiro et al. (2018)	Brazil	Upper middle-income	Latin America & Caribbean	Drinking water quality	Physical: Turbidity. Chemical: FRC. Microbial:E. coli and faecal coliforms.
30.	Sangalang et al. (2022)	Philippines	Lower middle-income	East Asia & Pacific	WASH facilities and hygiene practices.	Microbial: Total coliforms and E. coli.
31.	Yani et al. (2021)	Palu, Indonesia	Lower middle-income	East Asia & Pacific	Drinking water quality	Chemical: F−.
32.	Kouamé et al. (2021)	Côte d'Ivoire	Lower middle-income	Sub-Saharan Africa	WASH accessibility	Microbial:E. coli and total coliforms.

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The drinking water quality was not considered by many studies that looked at WASH in schools. Only 42% (32 studies) considered drinking water quality (Table 3). However, most of the studies focused on water supply in terms of availability and sufficiency (Table 4). The studies that considered drinking water quality were conducted mostly in lower middle-income countries (33%) and high-income countries (30%). Less studies were conducted in the upper middle-income and low-income countries. The physical, chemical, and microbial quality of drinking water was considered by all studies that considered drinking water quality.

The physical drinking water quality parameters that were examined were colour, taste, odour, pH, turbidity, temperature, electric conductivity, hardness, and salinity. The chemical drinking water quality parameters that were examined by the selected studies were aluminium (Al), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), Fe, Mn, molybdenum (MO), nickel (Ni), silicon (Si), strontium (Sr), vanadium (V), and zinc (Zn), fluoride (F⁻), total dissolved solids (TDS), phosphate (⁠⁠), chloride (Cl−), arsenic (As), cadmium (Cd), lead (Pb), dissolved oxygen (DO), iron (Fe), manganese (Mn), nitrates (⁠⁠), ammonia (NH3), nitrate (⁠⁠), phosphate (⁠⁠) and sulphate (⁠⁠), nitrite (⁠⁠), ammonium (⁠⁠), permanganate (KMnO₄), free residual chlorine (FRC), cyanide (CN⁻), chemical oxygen demand (COD), calcium (Ca⁺²), and bicarbonate (⁠⁠). The microbial water quality parameters that were analysed by the selected studies included E. coli, Shigella, Salmonella, Vibrio cholerae, Campylobacter, rotavirus, faecal coliforms, total coliforms, heterotrophic bacteria, Pseudomonas, colony-forming units (CFU), and parasites.

Of all the studies that considered drinking water quality, 66% of the studies included chemical parameters together with microbial and physical parameters, while 34% of the studies included chemical parameters only (Table 3). About 28% of the studies included microbial parameters alone, whereas the specific number of studies that used microbial parameters together with chemical and physical parameters was 59%. In 38% of the studies, physical parameters were included together with chemical and microbial parameters, while in 3% of the studies, physical parameters were included alone (Table 3). Only 16% of the studies were conducted in low-income countries and 9% of these studies included microbial parameters. This study revealed that lower middle-income countries considered the analysis of the microbial water quality, especially E. coli or faecal coliform. While the high-income countries focused primarily on chemical parameters, particularly Pb.

Several studies reported that improved WASH in schools is crucial in improving health and education efficiency in schools (Olukanni 2013; Appiah-brempong et al. 2018; Cronk et al. 2021; Ahmed et al. 2022; Akoteyon 2022; Toleubekov et al. 2022). Facilitating the implementation of WASH interventions in schools settings is of particular importance because most of the children's time is spent in school and they are more susceptible to various WASH-related diseases than adults (Agol & Harvey 2018; Banu et al. 2018; Ahmed et al. 2020, 2022; Bolatova et al. 2021). Therefore, to reduce the prevalence of WASH-related diseases, effective interventions for adequate safe WASH in schools should be implemented (Patel et al. 2014; Chard et al. 2019; Pandey et al. 2020; Wada et al. 2022). Furthermore, safe WASH inclusive of water of good quality in schools is not only a prerequisite to health but contributes to livelihoods, school attendance, and dignity (Bolatova et al. 2021; Ahmed et al. 2022).

Several studies have demonstrated an important exposure pathway between WASH services and health outcomes (Jordanova et al. 2015; Ahmed et al. 2020, 2022; Cronk et al. 2021; Morgan et al. 2021; Sangalang et al. 2022). The assessment and monitoring of water quality, particularly the microbial and chemical quality, is necessary for preventing potential human risks associated with exposure to contaminated water. To protect learner's health, it is recommended that water quality, particularly microbial quality, monitoring be included in schools’ WASH or routine water quality monitoring studies (Ahmed et al. 2020; Hung et al. 2020; Hossain et al. 2022).

This review identified few studies that support the role of safe WASH in school's primary role of providing education and essential life skills to children (Chard et al. 2019; Cradock et al. 2019; Komarulzaman et al. 2019; Tadesse & Hagos 2009; Bolatova et al. 2021; Toleubekov et al. 2022). Approximately 443 million school days are lost each year due to water-related illnesses, making this a leading factor for school absences in the developing world (Karon et al. 2017; Agol & Harvey 2018; Chard et al. 2019; Komarulzaman et al. 2019). Tadesse & Hagos (2009) suggests that access to adequate WASH services in schools may contribute to improved education and health of children by reducing the number of days missed in schools due to menstrual periods or illness. Moreover, poor provision of WASH in schools can result in lower enrolment, absenteeism, and dropout among girls (Jordanova et al. 2015; Habtegiorgis et al. 2021). Therefore, the provision of safe WASH in schools is not only a prerequisite to health but also to promote educational performance (Karon et al. 2017; Chard et al. 2019; Komarulzaman et al. 2019). A correlation between water quality and educational outcomes has been shown in several studies (Ahmed et al. 2020; Bolatova et al. 2021; Buajitti et al. 2021; Cronk et al. 2021). These studies have demonstrated that providing schools with improved water quality can contribute to improved educational performance (Hood et al. 2014; Borges-pedro et al. 2018; Ribeiro et al. 2018; Rahman & Hashem 2019; Hu et al. 2021; Kouamé et al. 2021; Yani et al. 2021; Ahmed et al. 2022; Bah et al. 2022; Hossain et al. 2022).

A global initiative has focused on improving access to WASH by increasing access to drinking water and sanitation (Erhard et al. 2013; Karon et al. 2017; Cronk et al. 2021). Yet studies also revealed that a lot of people in developing countries still do not have access to potable water and sanitation services (Ohwo 2019; Ahmed et al. 2020; Bolatova et al. 2021; Wada et al. 2022). While WASH provision has improved significantly over the world, progress in Sub-Saharan Africa has lagged that of other regions since Sub-Saharan Africa's rural areas have lower rates of access to WASH services and poorer health outcomes than metropolitan areas (Winter et al. 2021; Zerbo et al. 2021). This is because only 6% of the urban population in Sub-Saharan Africa uses unimproved sources of drinking water compared to more than 25% of the rural population (Winter et al. 2021; Zerbo et al. 2021; Wada et al. 2022). Consequently, many schools in low-income countries, especially sub-Saharan Africa, have inadequate access to WASH provision (Ohwo 2019; Akoteyon 2022). A study conducted in 14 low- and middle-income countries (Ethiopia, Ghana, Honduras, India, Kenya, Malawi, Mali, Mozambique, Niger, Rwanda, Tanzania, Uganda, Zambia, and Zimbabwe), revealed that not all schools have all three WASH facilities. Of the 2,690 rural schools, only 4% of schools had all basic water, sanitation, and hygiene facilities in all 14 low and middle-income countries (Bolatova et al. 2021; Cronk et al. 2021).

The deterioration in the drinking water quality in schools is mostly related to microbial water contamination. Several studies showed that schools in low- and middle-income countries are often deprived of microbial safe water (Banu et al. 2018; Ahmed et al. 2020, 2022; Bolatova et al. 2021; Cronk et al. 2021; Hossain et al. 2022). Some studies highlight that the supply of safe drinking water quality in schools has been compromised by the absence of adequate sanitary infrastructure (Cronk et al. 2021; Kouamé et al. 2021; Morgan et al. 2021). Whereas safe and adequate drinking water supply in schools is prerequisite aspects of the right to basic education for learners. Because contaminated drinking water poses health risks and lower level of academic success among learners (Meschede et al. 2018; Hung et al. 2020; Kouamé et al. 2021). Six of the selected studies (Borges-Pedro et al. 2018; Ahmed et al. 2020; Hung et al. 2020; Hossain et al. 2022; Kouamé et al. 2021; Alam & Mukarrom 2022) demonstrated through regular monitoring, poor water quality in schools. According to these investigations, the drinking water quality test results from the schools showed microbial contamination, primarily with E. coli and total coliforms.

A safe and adequate drinking water supply in schools is crucial (Antwi-agyei et al. 2017) and is essential for health and assisting learners in maintaining daily water intake. Several studies have shown that increasing water intake may improve hydration and cognitive performance among learners (Hood et al. 2014; Borges-pedro et al. 2018; Cradock et al. 2019; Rahman & Hashem 2019; Ahmed et al. 2020; Bolatova et al. 2021; Hu et al. 2021; Moreno et al. 2021; Morgan et al. 2021; Sangalang et al. 2022).

To ensure a safe water supply in schools, drinking water quality should be included during the evaluation of WASH provision (Bolatova et al. 2021). However, this study showed that there has only been a limited amount of research on drinking water quality in schools and that drinking water quality has not been fully researched in the context of WASH (Meschede et al. 2018; Cradock et al. 2019; Sangalang et al. 2022). Some studies have focused on the availability of water without determining the water the safety quality (Cronk et al. 2021; Morgan et al. 2021). However, it is necessary to make sure that students have access to safe drinking water at school. As mitigation intervention to improve drinking water quality, Ahmed et al. (2020), Hu et al. (2021), Cronk et al. (2021) and Bah et al. (2022), suggested that schools establish a routine water quality monitoring programme, as well as the implementation of cost-effective drinking water treatment methods such as solar disinfection and chlorination. Ahmed et al. (2022) suggested that Educational Monitoring and Information System (EMIS) should be implemented in schools to improve WASH. In addition, the assessment of drinking water quality in schools, in particular, microbial quality, is critical since it is linked to the prevention of infectious diseases. However, this study showed that in high-income countries, chemical analysis is given a greater priority than microbial and physical analysis. Since drinking water is a source of Pb exposure in North America, Pb has been primarily monitored in these schools. Leaching from plumbing system components has been identified as the main contributor to Pb water contamination in educational facilities (Al-saleh 1996; Bouchard et al. 2011, 2018; Patel et al. 2011; Ekenga et al. 2018; Buajitti et al. 2021).

Population growth and challenges in terms of water infrastructure coverage and portable water supply reliability, access to WASH provisions is lacking or limited, particularly in schools in rural areas in most developing countries (Ngwenya et al. 2018; Bolatova et al. 2021; Kouamé et al. 2021). Poor availability and access to water and sanitation are major health concerns and constitute a principal barrier to the achievement of quality education in schools (Agol & Harvey 2018). A study by Ngwenya et al. (2018) found that the three surveyed schools in northwest Botswana's Ngamiland District had unreliable water supply issues because they depended on the local water authority for water supply which also supplied water to many other educational institutions, small businesses, and residential areas. As a result, the three schools that were surveyed suffered from poor sanitation and hygiene. Moreover, a study by Garn et al. (2017) revealed a slight decline in the sustainability of the WASH programme in Mali over the 3-year period covered by the study (2012–2014) as evidenced that some of the schools appeared to face some challenges in sustaining their WASH programmes over time, and thus indicating the need for further improvements in ensuring that schools have the motivation and resources to maintain their WASH systems over time. Gaps in several vital aspects of WASH in schools, such as accessibility, maintenance, operation, lack of knowledge, and poor hygiene practices are noted occurrences (Bolatova et al. 2021). These gaps affect the achievement of SDGs, especially SDG 6, which focuses on ensuring ‘the availability and sustainable management of water and sanitation for all’ by 2030 (Bain et al. 2021; Cronk et al. 2021; Morgan et al. 2021; Asumah et al. 2022).

Significant global improvements in WASH access have been reported in some studies in the past two decades (Garn et al. 2017; Appiah-brempong et al. 2018; Winter et al. 2021). Efforts to increase access to improved water, sanitation, and hygiene globally including in rural areas have been noticed (Appiah-brempong et al. 2018). Since the 1990s, prior to the first adoption of WASH in 2001, a study by Al-Saleh (1996) revealed that learners in schools were at risk of ingesting chemically polluted water, and early intervention was suggested for remedial action. Even now during the 2020s, a study by Winter et al. (2021) has also reflected a significantly increased percentage of people worldwide who have access to improved water sources and adequate sanitation. It is noted however, the efforts have been primarily focused on WASH in the household or community, rather than at the institutional level, particularly in school settings (Cronk et al. 2021; Morgan et al. 2021; Winter et al. 2021). One of the successes of WASH is that WHO and UNICEF have produced the ‘Surveillance of water, sanitation, and hygiene in schools’ tool which could be used at the local and national level to monitor the holistic view of access to WASH and consequently could be used to cover SDG 6 in schools (Garn et al. 2017; Bolatova et al. 2021). The tool has primarily been used by the WHO/UNICEF Joint Monitoring Programme (JMP) to provide ongoing updates on the provision of WASH in schools around the world and is also available for use by researchers at the local level (Winter et al. 2021; Toleubekov et al. 2022). The JMP developed WASH service ladders for monitoring WASH services in schools around the world, classifying them as basic, limited, and no service. The service ladders are beneficial even locally, as researchers utilize them to evaluate the WASH status of schools (Toleubekov et al. 2022).

Schools as learning environments have the potential to be places where pupils learn safe WASH practices (Morgan et al. 2021). WASH services alone are often not sufficient, they need to be combined with educational programmes (Mushota et al. 2021). Although often taken for granted, hand washing education is the most simple, effective, and inexpensive measure for interrupting the transmission of micro-organisms and slowing the spread of diseases (Ngwenya et al. 2018). Hence, most school-based WASH programmes are to increase student knowledge and practice of behaviours such as washing hands with soap (Winter et al. 2021). However, evidence of good WASH-related practices and knowledge at schools is scarce (Kouamé et al. 2021). This discrepancy of knowledge and practice might arise due to the lack of handwashing facilities or the unavailability of clean water. A study by Kouamé et al. (2021) in the south-central part of Côte d'Ivoire revealed that, although learners had knowledge about WASH, however, they do not practice hygiene. Therefore, effective hygiene education should be incorporated into the school curriculum, as this will help promote long-term positive behavioural changes among pupils (Mogaji et al. 2018). According to a study conducted by Egbinola & Amanambu (2015) and Thakadu et al. (2018), despite the fact that hygiene education was incorporated into the curriculum, learners did not practice hygiene.

Several studies are done and as reviewed here contribute to information and practices towards the achievement of SDGs 3, 4, and 6, which are essential for ensuring safe WASH in schools (Karon et al. 2017; Agol & Harvey 2018; Appiah-brempong et al. 2018; Ngwenya et al. 2018; Bolatova et al. 2021; Cronk et al. 2021; Kouamé et al. 2021; Toleubekov et al. 2022). The SDGs 4 and 6 have to address the provision of safe water and sanitation for schools and increase schools' ability to offer an effective learning environment, including essential drinking water, sanitation, and hygiene (Appiah-brempong et al. 2018; Ngwenya et al. 2018; Bolatova et al. 2021; Cronk et al. 2021). SDG 3 aims to ensure healthier lives and encourage well-being at all ages to achieve sustainable growth. While Goal 4 seeks to improve the proportion of education facilities with access to an appropriate learning environment, including essential WASH. At the same time, Goal 6 aims at achieving access for all to potable water, sanitation, and hygiene (Karon et al. 2017; Ngwenya et al. 2018; Bolatova et al. 2021; Kouamé et al. 2021; Toleubekov et al. 2022). One notable strategy for achieving the related SDGs to safe water supply and sanitation by 2030 is to provide schools with sustainable, safe WASH (Agol & Harvey 2018). A study by Kouamé et al. (2021), indicates achieving SDG 6 will be difficult to reach by 2030 in 20 schools surveyed in the Taabo health and demographic surveillance systems in the south-central part of Côte d'Ivoire. This is because the findings of their study revealed that the drinking water of the surveyed schools did not comply with the set water quality standards, and sanitation infrastructure is lacking to a large extent and inadequate. Moreover, there was no provision of hygiene infrastructure such as handwashing stations, soaps, and menstrual hygiene management facilities.

The SDGs place a strong emphasis on ensuring that everyone has access to clean and safe water, sanitation, and hygiene as well as improving schools' ability to create a positive learning environment. This study, however, identified a gap where most studies just consider water availability and neglect including drinking water quality analyses, whereas, drinking water quality analysis are necessary to establish whether the water is safe to drink or not. Some investigations have also shown that drinking water quality in schools was microbially compromised by E. coli and total coliforms. Therefore, effective school-based WASH interventions are needed to better protect children's health. This must include drinking water quality assessment programmes in schools.

This study also revealed that most middle-income countries considered the analysis of the microbial water quality, especially E. coli or faecal coliforms. While the high-income countries focused primarily on chemical analysis, particularly, Pb. This suggests that the priorities of developing and developed countries differ in relation to the supply of WASH facilities. This does, however, show that there are concerns with drinking water quality in both developed and developing countries.

Drinking water quality has an impact on the availability of safe WASH. Even if water is provided in adequate quantities, if the quality is poor, it will still contribute to negative health effects and affect safe WASH. From the literature study as presented, as part of safe WASH, it is recommended that routine drinking water quality monitoring programmes be incorporated in schools, and that cost-effective water treatment procedures be implemented where appropriate. This should involve the implementation of EMIS. This study also discovered that there were limited studies that covered drinking water quality analysis in schools; as a result, this study recommends that additional water quality analysis studies be undertaken in schools to improve academic awareness and help the world achieve the SDGs by 2030.

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

The authors declare there is no conflict.