1 Introduction

Vended sachet water has become a dominant source of drinking water in Ghana over the years, and the industry is expected to continue growing, with many new sachet brands emerging [1, 2]. Consequently, water security along the sachet water value chain has become an important topic among water researchers and stakeholders. Water security is crucial for preventing waterborne disease and protecting consumer health of consumers [3, 4]. Ideally, high-quality water should be colourless, tasteless, odourless, and free from pathogens and other chemical contaminants [5,6,7].

According to the GSS 2021 report, the three main sources of drinking water in Ghana are sachet water (37.4%), pipe-borne water (31.7%), and borehole water (37.4%) [8]. In the Greater Accra Region, sachet water packaged in 500 mL polyethylene bags serves most of the population (70.7%) [8]. This is mainly due to its affordability, availability, and role in providing safe, accessible drinking water for middle and low-income citizens [9, 10]. The water vending industry in Ghana has evolved over time. It began with hawkers selling water in plastic plastic cups [2], which raised health concerns due to cup reuse [11,12,13]. Later, water was sold in hand-tied plastic bags, known as ‘ice water [14].’ This method raised questions about water quality and hygiene practices [14], Sachet water, or ‘pure water,’ was introduced in the mid-1990s to provide safe, affordable, and accessible drinking water in Ghana [11, 13].

Sachet water is considered an improved water source compared to boreholes, streams, and pipe water from the Ghana Water Company Limited (GWCL), which has struggled to meet household water needs [14,15,16]. Poor perceived quality from the GWCL piped water, due to infrastructure issues, has further increased sachet water usage [13, 17, 18]. As Ghana works towards achieving Sustainable Development Goal 6.1 (universal access to safe and affordable drinking water) by 2030, the sachet water industry plays a crucial role [2]. Population growth and urbanization have driven increased reliance on sachet water, as demand for improved water sources rises due to stress on existing resources. This suggests sachet water will likely remain a primary source of drinking water source for many Ghanaian households in the coming years [11, 19]. Sachet water production involves various treatment techniques, including filtration, chlorination, reverse osmosis, distillation, and UV treatment [20]. The treated water is then sealed using rubber sealing machines and distributed to retailers for sale to consumers. Polyethylene is the preferred packaging material due to its cost-effectiveness, heat-sealing capability, inertness, and lack of odor [21,22,23,24]. The reliance on treated packaged water is expected to grow, with many consumers believing it to be free from contamination and more hygienic [25, 26]. However, there is a risk of recontamination during production, transport, distribution, retailing, and consumer storage [9, 27]. Recent research suggests that exposing sachet water to direct sunlight or prolonged room temperature storage can lead to water quality deterioration making it unsafe for consumption [28,29,30]. According to GS 175: 2021 water quality assessment protocol, finished water should be free from human enteroviruses and have TC counts of < 1 CFU/mL [31]. Some studies suggest that packaged water in Ghana does not consistently meet this requirement [13, 32]. Factors contributing to packaged water contamination include source water quality, treatment methods, packaging materials, storage conditions, and distribution.

This study aims to address two questions:

  1. 1)

    Does the mode of storage affect sachet water quality?

  2. 2)

    What is the optimal storage method to maintain packaged water quality until consumption?

2 Materials and methods

2.1 Sample collection and storage

Two commonly consumed sachet water brands (polyethylene bagged drinking water) from the Adentan Municipal Assembly were purchased from factories on their production day and transported to the laboratory for analysis. They were labeled SWA and SWB. Two bags of each brand were stored in two different conditions:

  1. 1.

    On a wooden pallet in a room, with an average temperature of 27 °C (Fig. 1a),

  2. 2.

    In a cage outside, exposed to sunlight, with an average temperature of about 33 °C (Fig. 1b).

Fig. 1
figure 1

Sachet water storage conditions in Accra, Ghana

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Six sachets were randomly sampled monthly for 3 months and sent to the laboratory for physicochemical and microbial analysis. The analysis followed Ghana Standard Authority Protocols for drinking water [31].

2.2 Physicochemical and microbial analysis

Water quality analysis followed methods prescribed by the American Public Health Association [33]. Physicochemical indicators were measured as follows:

  • pH: using a pH meter,

  • Total dissolved solids: using an electrical conductivity meter,

  • Turbidity: using a turbidity meter,

  • Total hardness, total alkalinity, calcium, magnesium, and chloride: using titrimetric methods,

  • Nitrate, phosphate, fluoride, and sulfate: using a UV/visible spectrophotometer (APHA 4500 standard) [33].

Microbial indicators were assessed using the membrane filtration technique:

  • Total and fecal coliforms: APHA method 9221,

  • Escherichia coli: APAHA method 9221,

  • Total heterotrophic bacteria: APHA method 9215.

Each 100 mL water sample was filtered through a 0.45 µm pore size membrane filter [33]. For total coliforms, E. coli, and fecal coliforms, samples were incubated on specific media [M-endo, Hicrome (Difco) Media, SS agar, and M-FC] in Petri dishes at 37 °C ± 0.5 °C and 44 °C for 16–24 h. Total Heterotrophic bacteria were determined using the pour plate method, incubated at 37 °C ± 0.5 °C for 48 h, with colonies counted using a colony counter [33].

3 Results

The quality of the sachet water was evaluated using both physicochemical and microbiological procedures. The results are shown in Tables 1, 2, and 3. For the unexposed samples, pH ranged from 7.21 to 7.66, with a mean of 7.372 ± 0.1862; total dissolved solids (TDS) ranged from 42.40 to 56.8 with a mean of 49.56 ± 6.6583 mg/L (represented in Fig. 2). Chloride (Cl−) ranged from 3.57 to 10.9 mg/L with a mean of 6.03 mg/L. Flouride (F−) ranged from 0.00 to 0.065 with a mean of 0.014 mg/L; Sulphate (SO42−) ranged from 0.00 to 1.04 mg/L with a mean of 0.408 mg/L; Phosphate (PO3−) ranged from 0.00 to 3.00 mg/L with a mean of 1.014 mg/L: Potassium (K), ranged from 0.50 to 3.0 mg/L with a mean of 2.02 mg/L; Calcium (Ca) ranged from 0.72 to 6.4 mg/L with a mean of 3.382 mg/L; Magnesium (Mg) ranged from 0.83 to 3.3 mg/L, with a mean of 2.057 mg/L; Bicarbonate (HCO3−) ranged from 30.50 to 46.4 mg/L with a mean of 40.28 mg/L.

Table 1 Comparison between physicochemical water quality parameters for unexposed sachet water
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Table 2 Comparison between physicochemical water quality parameters for exposed sachet water
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Table 3 Correlation studies between pH, nitrate, and nitrite results
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Fig. 2
figure 2

Graph showing changes in TDS concentration of sachet water over 90 days

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For the exposed samples, the results were as follows; pH ranged from 7.06 to 7.67; total dissolved solids ranged from 43.1 to 57.5 mg/L with a mean of 49.46 mg/L; Calcium ranged from 0.802 to 6.41 mg/L, with a mean of 3.4784 mg/L, Magnesium ranged from 0.825 to 3.35 mg/L with a mean of 2.037 mg/L; Bicarbonate ranged from 30.5 to 47.3 mg/L with a mean of 39.96 mg/L; Sodium ranged from5 to18.5 mg/L) with a mean of 10.02 mg/L; Potassium ranged from, 0.5 to 3.1 mg/L with a mean of 2 mg/L; Nitrate ranged from 0.052 to 0.148 mg/L with a mean of 0.0818 mg/L; Flouride ranged from 0 to 0.4 mg/L with a mean of 0.081 mg/L, Sulphate ranged from 0 to 0.947 mg/L with a mean of 0.1894 mg/L, Phosphate ranged from 0 to 0.021 mg/L with a mean of 0.01 mg/L. Figure 3 shows a scatter plot of changing Nitrate and Nitrite levels with pH.

Fig. 3
figure 3

Plot of pH versus nitrate concentration (mg/L) and nitrite concentration (mg/L)

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The microbial analysis results were as follows; month 1; one exposed sample showed a total coliform count of 93 CFU/mL and total heterotrophic bacteria (THB) count of 416 CFU/mL; month 2; no microbial growth was detected for any of the measured indicators; month 3; all water samples showed THB counts ranging from 25 to 884 CFU/mL, with a mean of 326.6 CFU/mL.

The analysis revealed a strong statistically significant positive correlation (r = 0.724, p = 0.008) between the concentrations of nitrate-nitrogen and nitrite-nitrogen as shown in Table 3. This indicates that as nitrite-nitrogen concentration increases, there is a corresponding increase in nitrite-nitrogen concentration.

4 Discussion

In Ghana, sachet drinking water is convenient and affordable for many, low and middle-income citizens. The two bulk sachet vending practices are; water sold in enclosed shops or containers and water sold in cages outside shops with sunlight exposure. This study evaluated how these two storage practices affect sachet water quality during vending. The key findings are that no indicators for physicochemical water quality exceeded Ghana Standards Authority (GSA) limits. pH levels decreased over time in both exposed and unexposed samples. These findings contradict previous studies suggesting sunlight exposure increases water pH [9, 29, 34]. pH values were within the required WHO (2011) guidelines [35] and showed a reverse relationship with temperature. pH changes can also influence nutrient solubility in water [36].

The results show electrical conductivity and total dissolved solids (TDS) levels increased in both sachet water brands over the 3 months. Higher conductivity, in long-stored water, may be due to ion dissolution and calcium concentrations changes [37, 38]. The results show that decreasing pH sulphate and phosphate ion dissolution affects TDS [11].

4.1 Ion concentrations

Calcium and magnesium increased after 2 months. Then decreased. Sodium and chloride ions showed varying trends. Sunshine exposure accelerated residual chlorine reduction [39].

4.2 Alkalinity and hardness

Total alkalinity and bicarbonate increased after 2 months and then declined. Fluctuations in the alkalinity results may be linked to biological activity or CO2 loss hardness fluctuated over time [40].

4.3 Nitrate and nitrite levels

Nitrate and nitrite l fluctuated throughout the trial period (Fig. 4).

Fig. 4
figure 4

Plot of nitrate concentration (mg/L) versus nitrite concentration (mg/L)

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Excess nitrate can promote algal growth and pose health risks. Sulphate and phosphate ions showed varying levels, potentially impacting microbial growth in water [41].

4.4 Bacteriological quality

The key findings were, during the first month of the study, one of the exposed sachet water sample showed a total coliform count of 93 CFU/mL, exceeding the required limits (Table 4). The high levels of total coliforms can indicate environmental contamination, treatment issues, or bacterial regrowth [27]. I the third month, which is the expiry duration for sachet water in Ghana, bacteriological analysis showed total heterotrophic bacteria (THB) counts for all samples; SWA_Unexp had a count of 884 CFU/mL, SWA_Exp had a count of 468 CFU/mL, SWB_Unexp had a count of 25 CFU/mL, and SWB_Exp had a count of 256 CFU/mL; Fig. 5. These results align with previous studies showing water quality deterioration over prolonged storage [29, 30, 39]. SWA_Unexp had THB levels exceeding the required limits (Table 4). SWB_Exp showed reduced total coliform count, likely due to solar disinfection [42, 43], but the sachet rubber had discoloured. The heterotrophic bacteria group of water quality indicators utilize organic carbon sources for growth. The colony count indicates overall presence of aerobic and facultative anaerobic bacteria [27, 35]. The increased THB counts suggest water quality [29, 39, 44]. THB multiply quickly in sachet water stored at room temperature for extended periods [29, 39, 45].

Table 4 Bacteriological water quality data
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Fig. 5
figure 5

Effect of storage conditions on the bacteriological quality of packaged water

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5 Conclusion

The study results indicates that while storing packaged sachet water outdoors in sunlight-exposed cages can reduce microbial load, it is not the best practice. The key findings are:

  1. 1.

    Overtime, sunlight exposure causes:

    • Fading of print on plastic packaging, making brand names and important information difficult to read.

    • Deterioration of packaging material, posing a risk to water quality.

  2. 2.

    Microbial water quality

    • By month 3, there was an increase in total coliform and heterotrophic bacteria counts.

  3. 3.

    Current regulations:

In Ghana, packaged sachet water has a 3-month expiry date from production.


Recommendations:

  1. 1.

    Vendors are encouraged to install UV lights in water vending shops and warehouses.

  2. 2.

    Vendors and shop owners should be sensitized to monitor batch receipt dates to ensure they do not exceed the 3-month expiry period.

  3. 3.

    Consumers should avoid buying packaged sachet water in bulk and storing if for months at home. This practice can help reduce the risk of water quality deterioration over time.