Microbiological quality of drinking water from three flood-prone communities along the Odaw River in Accra, Ghana

Over the past two decades, Ghana has made significant progress in providing access to safe drinking water, yet there are still areas with limited access. In most developing countries, inaccessibility of safe drinking water, coupled with pollution and poor sanitation and hygiene practices, directly impacts the overall quality of drinking water, the consumption of which may pose serious health risks to the consumer. Populations in inner cities and poor urban communities are often the most affected. According to the World Health Organization (WHO), diarrhoea was responsible for approximately 370,000 fatalities in children under the age of five years globally (WHO 2019). As of 2020, 1.3–4.0 million cases of cholera were projected each year, with approximately 21,000–143,000 reported deaths in all WHO regions due to infections linked to poor water, sanitation, hygiene, and other contributing drivers.

Despite the overwhelming importance of water, global access to safe drinking water has been impacted by a myriad of both natural and anthropogenic activities. Given how essential water is to human health and development, strict regulations must always be established to guarantee that every individual has access to safe drinking water. In recent times, plans to guarantee access to clean water in Ghana have mostly concentrated on pipeline supply and shared water sources (Fisher et al. 2015).

Rapid urbanization, excessive resource use, and poor waste-disposal practices or management have further impacted on water quality (McGrane 2016). The state of drinking water quality in metropolitan settings has been documented by several researchers (Edokpayi et al. 2018; Irda Sari et al. 2018) from various regions of the world. A period of substantial urbanization and population growth has been observed in Ghana (Machdar et al. 2013), significantly impacting on safe drinking water supplies. This rapid urban and population increase has had a noteworthy effect on access to safe drinking water.

Interventions to improve drinking water quality provide significant health benefits. As a result, most people now use sachet water for their everyday domestic needs. Packaged/sachet water is the leading source of drinking water in most homes in Ghana. Census data from the Ghana Statistical Service showed 37.4% of all households in the country use sachet water as drinking water, followed by pipe-borne water (31.7%) and boreholes (17.7%) (Ghana Statistical Service 2021). According to the Ghana Statistical Service (2021), the Greater Accra region has the highest percentage of sachet-water use, up to 70.7% in Ghana. Informally vented water is an essential water source for low-income people who do not have access to formal or public sources of water (Manjaya et al. 2019).

Unfortunately, quality drinking water has become a scarce commodity in many developing countries such as Ghana. Given that water quality evaluation is a continual process, information on water quality updates is required for water quality assessment due to the negative impact of contaminated water on health. Considering the fact that the physical appearance of water is not the primary predictor of its health or wholesomeness, determining the quality of water before consumption is crucial to reducing microbial contamination. This study aimed to conduct a microbiological assessment of water (community-shared pipe-borne or tap water and locally manufactured sachet-water) in three flood-prone communities in Accra, Ghana. These three communities, namely, Alajo, Avenor, and Agbogbloshie, are settlements along the Odaw River known for their poor waste-disposal and hygiene practices and incidents of flooding.

Three communities, Alajo, Avenor, and Agbogbloshie, were purposefully selected for this study based on their proximity to the Odaw River. These communities are also known for their poor sanitation, poor waste disposal and hygiene practices, and incidents of flooding. The microbiological quality of the two main sources of drinking water, as described by the 2021 population census of Ghana, i.e. pipe-borne (tap) and sachet water, was investigated. Community-shared tap water or locally produced sachet-water samples were selected based on availability.

A total of 68 water samples were collected as follows: Alajo = 28, Avenor = 21, and Agbogbloshie = 19. The names of the sachet-water brands are not stated due to confidentiality and market/social implications. For community tap water, Global Positioning System (GPS) coordinates were first recorded, followed by the measurement of physicochemical parameters on site. The GPS coordinates of sampling sites and maps of Alajo, Avenor and Agbogbloshie are shown in Figure 1. Water samples meant for microbiological analysis were collected in appropriately labelled sterile bottles and kept in an ice-cold chest. Before collecting water samples from community-shared taps, both hands were first washed thoroughly with soap and clean water, and then sanitized with 70% alcohol. The taps were not disinfected before sampling because the aim was to mimic the everyday practice of community members. However, before sample collection from taps, they were made to run for several seconds to naturally flush out any contaminants before sampling. To avoid external contamination or degradation, the samples were kept in the refrigerator upon arrival at the laboratory until the time of analysis.

This method reports an exact count of bacteria in water by measuring the growth of colonies on the surface of membrane filters. An already prepared m-FC medium was poured into sterile Petri plates and allowed to set. Next, sterile membrane filters were placed over porous plates or receptacles with sterile forceps. Carefully matched sterile funnel units were then placed over the receptacles without touching the rims and locked in place. The manifold valve was closed, and the vacuum turned on. Each tap-water sample was shaken well and poured aseptically into the funnel, up to the 100 mL mark. For sachet water, a pair of scissors was sterilized (with alcohol and flaming) and a corner of the sachet was cleaned with an alcohol wipe. The sterile corner was cut, and the content was poured as above. The manifold valve was opened, and the sample was filtered under partial vacuum. After all the samples were filtered, the valve was closed, unlocked, and the funnel was removed. The membrane filter was immediately removed carefully with sterile forceps, making sure not to disturb the inner area of the filter. The membrane filter was then placed on the designated medium in a rolling gesture to avoid entrapment of air. Note, incorrect membrane filter placement was at once obvious because of lack of staining of the membrane indicating entrapment of air. Where such patches occurred, the filter was carefully reset on the agar surface. Finally, Petri dish lids were replaced and incubated at 44°C for 18–24 h by inverting the culture plate. All blue colonies were counted and recorded as faecal coliform bacteria.

For the microbiological assessment of total coliforms and Escherichia coli (E. coli), sterile hicrome coliform medium was poured into Petri dishes and allowed to set after thorough disinfection of hands and equipment.

Tap-water samples were shaken and poured into the funnel up to the 100 mL mark. For sachet water, their corners were first cleaned with alcohol, before cutting them with a sterilized pair of scissors. The content was then poured as above, and the valve opened to allow for filtering of the sample under partial vacuum. The valve was then closed, and the funnel removed. The membrane filter was carefully lifted and placed on the culture medium using sterile forceps. The Petri dish was then closed, and the plates were incubated at 37°C for 18–24 h. Dark blue to violet colonies were counted as E. coli. Salmon red and dark blue to violet colonies were counted as total coliforms.

Analytical-grade reagents were utilized throughout the experiment. Plastic and glassware were soaked in 10% HNO₃ for 24 h, then cleaned and dried overnight in the oven. Standard operating procedures were strictly followed during microbiological assessment of water in the laboratory regarding safety procedures, usage of reagents, and disposal of cultures. There were no water particles on the membrane filter surfaces after filtration and placement on the medium. Patches of unstained membrane were avoided, as they could be an indication of entrapped air. Only evenly distributed colonies were counted. For every batch of ten samples analysed, blanks (sterile distilled water) were examined and utilized as negative control.

A quality rating scale (q_i) for each parameter is assigned by dividing its concentration in each water sample by its respective standard and the result multiplied by 100: q_i = (C_iS_i) × 100, where C_i is the concentration of the parameter in the water sample and S_i is its standard value (Ramakrishnaiah et al. 2009).

The unit weight (W_i) for each parameter is calculated as described by Ramakrishnaiah et al. (2009).

The overall water quality index (WQI) is calculated by summing the product of the quality rating (q_i) and unit weight (W_i) as follows: WQI = ∑(W_i × q_i).

The WQI result is compared with the following classification (Tiwari & Mishra 1985; Ramakrishnaiah et al. 2009):

• < 50: Poor

• 51–70: Good

• 71–90: Very Good

• 91–100: Excellent

The WQI is used to assess the quality of water samples collected in the research, helping to determine the level of risk based on the water's condition.

The microbial and physicochemical parameters were used to generate mean values and standard deviations, indicating water quality. Statistical analyses of data from the sample sites as well as the laboratory analyses were done using Microsoft Excel and STATA 15.0. To illustrate and explain the physicochemical and microbiological characteristics of water samples, summary statistics of mean values and standard deviations were carried out. The data were checked for normality before the mean values were calculated.

According to the WHO, water meant for drinking purposes should not have any microbiological origin and coliform counts. Although total coliforms can come from sources other than faecal matter, a positive total coliform sample is considered an indication of pollution and may increase the risk of contracting waterborne diseases. The mean total coliform count in tap-water samples from Alajo was 438 ± 18.35 SD cfu/100 mL as presented in Table 1. However, faecal coliform and E. coli were not detected in these samples. Also, none of the locally manufactured sachet-water samples showed evidence of microbiological contamination.

The mean total coliform, faecal coliform, and E. coli counts in tap water from Avenor were 592 ± 19.47 SD cfu/100 mL, 25 ± 3.91 cfu/100 mL, and 25 ± 3.19 cfu/100 mL, respectively, as presented in Table 2. The mean bacteria count for tap water far exceeded the WHO guideline limit of 0 cfu/100 mL. However, none of the locally manufactured sachet-water showed evidence of microbiological contamination.

Mean total coliform, faecal coliform, and E. coli counts in tap water from Agbogbloshie were 328 ± 12.92 SD cfu/100 mL, 79 ± 4.28 SD cfu/100 mL, and 41 ± 3.27 cfu/100 mL, respectively, as presented in Table 3. The mean bacteria count for tap water far exceeded the WHO guideline limit of 0 cfu/100 mL. By contrast, none of the locally manufactured sachets showed evidence of microbiological contamination.

The mean total coliform, faecal coliform, and E. coli counts in tap water from Alajo, Avenor and Agbogbloshie are presented in Table 4. Apart from Alajo, tap-water samples from Avenor and Agbogbloshie were contaminated with faecal coliforms and E. coli, which may reflect on the poor sanitation and waste-disposal practices in these communities.

The WQI is calculated by averaging the individual index values of some or all the parameters within five water-quality parameter categories. In this study, the WQI was calculated from the following physicochemical parameters: temperature, pH, conductivity, dissolved oxygen, total dissolved solids, and salinity. The values of physicochemical parameters used to calculate the WQI for each parameter and overall WQI are presented in the Supplementary Material, Tables S1, S2, and S3. Overall, the water quality indices of tap water from Alajo, Avenor and Agbogbloshie were 73.18, 87.9, and 71.4, respectively, which is classified as very good under the WQI table.

This study aimed at assessing the microbiological quality of two main sources of drinking water in three suburbs of Accra, namely, Alajo, Avenor, and Agbogbloshie. The Odaw River is a major river with other tributaries that originates from the Eastern Region of Ghana and flows through Accra. Along its course, it is characterized by intense human activity: industries, agricultural areas (including vegetable farms and animal ranches), transport terminals with shopping-centres, and open food-markets. The settlements along the banks, including the three under study, are mostly poor urban communities often characterized by indiscriminate waste disposal and poor sanitation. According to the WHO, no water meant for drinking purposes should have any bacterial contamination, and coliform counts should be 0 cfu/100 mL (WHO 2011, 2022). All locally manufactured sachet-water samples from the three communities had no microbial counts. The results of the study show that there has been a significant improvement in sachet-water quality, since there was no detection of live microbial cells. By contrast, several community-shared tap-water samples from the three study sites showed contamination with total coliform and faecal coliforms, as well as E. coli. It is important to note that water samples used for microbiological assessment were collected in sterile bottles. Faecal coliform bacteria are bacteria found in human and animal waste, and are the most common sources of microbial contamination in water (WHO 2011, 2019). The presence of total coliforms in water is not always harmful and does not always indicate the presence of faeces. A positive total coliform sample often points to water supply system pollution. Conversely, faecal coliforms are bacteria that indicate potential faecal or sewage contamination of drinking water. Thus, their presence often raises concerns about the water quality and suggests a higher likelihood of pathogenic organisms being present, which then increases the risk of transmission of waterborne diseases (WHO 2011, 2022). In such situations, it is advisable to constantly monitor drinking water sources to reduce the public health risk to consumers. Total coliforms are used routinely as indicators of pollution, and to assess the effectiveness of water filtration or disinfection, or the integrity and cleanliness of water distribution systems (Mengel et al. 2014). The WHO guideline for drinking water quality recommends the absence of total coliforms in drinking water (WHO 2011, 2022). Humans are more affected than aquatic organisms by the presence of faecal coliforms, which may be responsible for a number of diseases, including ear infections, cholera, dysentery, typhoid fever, and viral and bacterial gastroenteritis. Most community taps were situated close to drainage systems, improved toilet facilities, and other sanitary facilities, which could explain why bacteria concentrations varied. It is not uncommon to see polyvinyl chloride (PVC) pipes that carry pipe-borne water to various households totally exposed or crisscrossing one another. Also, the sight of burst PVC pipes gushing out water after heavy flooding is common. This breach in PVC pipes could lead to contamination of the water supply system with faecal organisms. E. coli is a type of bacteria found in the faeces of warm-blooded animals (humans, other mammals, and birds). The presence of E. coli in food or water indicates that there has been recent sewage or animal-waste contamination (Motlagh & Yang 2019; Odonkor & Mahami 2020). Untreated sewage, poorly maintained septic systems, un-scooped pet waste, and farm animals with access to water bodies can all lead to high levels of faecal coliform bacteria in the water, making it unsafe to drink. The WHO considers a zero E. coli count per 100 mL of water to be safe for drinking (WHO 2011, 2022). E. coli comes from human and animal waste, and during flooding, bacteria may be washed into rivers, streams, lakes, and groundwater. When these waters are used as drinking water sources and the water is not treated or is treated insufficiently, E. coli may end up in the drinking water.

Physicochemical parameters, including pH, salinity, electrical conductivity, dissolved oxygen, and total dissolved solids, were within WHO standards (WHO 2011, 2022). The overall computed WQI for both tap and sachet water in all three communities was between very good or good, and thus fit for human consumption.

The detection of faecal coliforms and E. coli in most community-shared tap-water samples indicates recent faecal contamination and a public health risk factor for transmission of waterborne diseases among households or communities. Community-shared tap water is a source of drinking water for most vulnerable groups in urban poor communities, and therefore there is a need for community public or environmental health services, as well as water management committees, to constantly monitor and ensure water sources do not present a risk of waterborne disease transmission.

The authors express their gratitude to the Head and staff of the Water Research Institute (WRI), Council for Scientific and Industrial Research (CSIR), Ghana, for their assistance during the microbiological analysis.

This study received funding from Water Essence Africa, Grant # QZA-21/0162.

A.A.B. and J.A.-M. conceptualized the study, and participated in its design and coordination. A.A.B. conducted all experiments and drafted the paper with J.A.-M. R.S., S.A.B., J.N.F., and J.A.-M. participated in the study design and critically reviewed important intellectual content. J.A.-M. and J.N.F. acquired the funding for this study. All authors read and approved of the final paper.

The authors declare that they have no competing interests

Our paper does not report on or involve the use of any animal or human data or tissue, so ethics approval and consent are not required.

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