Assessing the groundwater quality in Ghana's Nanton District: comprehensive evaluation and implications for sustainable management

Access to clean and safe groundwater is essential for the well-being of communities, agricultural productivity, and overall development. Groundwater serves as the primary freshwater source in regions where surface water is scarce or contaminated, such as Northern Ghana's Nanton District, where it is crucial for meeting the population's water needs (District Planning Coordinating Unit 2021). However, concerns persist about the district's groundwater quality and its suitability for drinking. To ensure sustainable groundwater management, it is imperative to assess both the physicochemical and microbial qualities of the water.

While previous studies by Iddrisu et al. (,2023b) provided insights into groundwater's suitability for irrigation in the district, they did not investigate its hydrochemical properties or fitness for drinking. Similarly, Ampofo et al. (2018) extensively examined groundwater quality in an adjacent area but did not consider the specific conditions in the Nanton District. Although various studies across Ghana have addressed hydrochemical properties and microbial quality of groundwater for public health and sustainable water resource management, research within the Nanton District has been conspicuously lacking. Therefore, this research aims to fill this knowledge gap by conducting a comprehensive evaluation of groundwater quality and hydrochemical properties in the Nanton District of Ghana.

The Nanton District, centered around Nanton town, relies heavily on groundwater sources like boreholes, wells, dugouts, and rainwater for domestic and agricultural water needs (District Planning Coordinating Unit 2021). This study focuses on assessing groundwater quality by evaluating its physicochemical, microbial parameters, and hydrochemical processes. Thirty groundwater samples were collected from 30 different communities throughout the district and thoroughly analyzed for their physicochemical, microbial content, and hydrochemical properties.

Assessing groundwater quality involves various analytical methods and techniques. The weighted arithmetic water quality index (WQI), previously used by Ibrahim (2019), Nguyen et al. (2022), and other researchers, was employed to determine the suitability of groundwater for drinking. Additionally, graphical tools, including Gibbs diagrams, Piper trilinear diagrams, Stiff plots, scatter plots, Schoeller indices, and correlation matrices, previously employed by Salifu et al. (2017), Iddrisu et al. (2023a), and others, were adopted to enhance our understanding of groundwater quality, hydrochemical characteristics, microbial–physicochemical correlations, and major ion distributions. Physicochemical analysis focused on parameters such as pH, electrical conductivity, total dissolved salts (TDS), major and trace element concentrations, turbidity, and potential contaminants like heavy metals. The microbial assessment identified and quantified indicator organisms like Salmonella, Escherichia coli, and total coliform bacteria to assess microbial contamination in the groundwater samples.

The research findings provided valuable insights into groundwater quality in the area. It identified areas where groundwater is safe for drinking without pretreatment and areas where treatment measures are necessary due to physicochemical or microbial contaminants. Additionally, the hydrochemical analysis shed light on the distribution of major ions and factors influencing groundwater chemistry within the district. Addressing the knowledge gap regarding groundwater quality in the Nanton District aims to inform decision-making in water resource management and development, benefiting policymakers, water resource managers, and local communities in ensuring sustainable groundwater use and public health protection.

In conclusion, this research aims to assess the physicochemical and microbial characteristics of groundwater in the Nanton District of Ghana using various analytical techniques. The results not only enhance our understanding of groundwater quality but also provide critical insights for long-term water resource management planning.

The Nanton District is the research area, and it is in the northern part of Ghana, with its capital as Nanton. The district is predominantly rural and was formed out of the then Savelugu-Nanton municipal by the legislative instrument 1988 under the PNDC Law 207 (District Planning Coordinating Unit 2021). The district has a total population of 50,767, with 25,257 (49.7%) males and 25,510 (50.2%) females, as reported in the 2021 population and housing census (District Planning Coordinating Unit 2021).

The district has two distinct climate seasons: dry and rainy. The district's daily temperatures were feverish, with an average temperature of 34 °C. Minimum temperatures as low as 16 °C and maximum temperatures as high as 42 °C were recorded in the district (District Planning Coordinating Unit 2021). Low temperatures are common in the district from early December to late February and are influenced by northeast trade winds (Harmattan).

Nanton District has a single farming season and receives an average of 600 mm of precipitation per year. According to the District Planning Coordinating Unit (2021), the annual precipitation pattern is erratic in early April and intensifies as the season progresses, occasionally increasing the average from 600 to 1,000 mm.

Approximately 76% of the people in Nanton District have access to potable water for drinking and other domestic activities. This increases the district's access to potable water. However, many district communities were spread out in a dispersed pattern of settlement. Because people must walk long distances in search of potable water, many communities in the district do not have immediate access to it (District Planning Coordinating Unit 2021). The district currently has three small-town water supply systems, only one of which is operational (District Planning Coordinating Unit 2021). As a result of Ghana Water Company Limited's lack of potable water supply systems in the district, communities in the district rely solely on boreholes and wells for potable water supply for drinking and other domestic activities.

The sanitary conditions in Nanton District are alarming. Houses in the district indiscriminately dump their solid waste. Of the many houses, only 2.3% of households are served with solid waste management services, as stated in the District Planning Coordinating Unit (2021). In addition, sewage from household chores, bathhouses, and other sources is indiscriminately disposed of. The gutters in the district for wastewater drainage systems were created using natural running water. Furthermore, inadequate household and public pit latrine facilities have made open defecation a common practice in the district (District Planning Coordinating Unit 2021).

Before beginning sampling, the sampling materials and equipment were cleaned. The sampling and storage materials included 1-L preconditioned polyethylene bottles, light-proof ice chest containers, and ice packs. Equipment such as steel tape, masking tapes, GPS coordinate application 1.17, and a bailer were used. Masking tapes were designed and used to record and label sample details. Preconditioned polyethylene bottles to be used for samples responsible for physicochemical and heavy metal analyses were first washed with dilute nitric acid, followed by rinsing with distilled water.

The Nanton District, where the samples were collected, was categorized into three clusters: Naton, Tampion, and Zogu traditional areas. A simple random sampling of 10 different communities from each cluster was adopted for groundwater sample collection. Two groundwater samples from active boreholes were collected at each sampling point from the 10 different communities in each cluster. The two samples taken at each sampling point were used for physicochemical and trace element determination, whereas the other samples were used for microbial quality parameter determination. In total, 60 samples were obtained. At each sampling point, the names of different communities were used to label the samples for easy identification.

A preliminary visual inspection was conducted to understand the in situ conditions of the study area, as described by Barcelona et al. (1985). This was performed to identify the possible sources of contaminants in the groundwater. A steel measuring tape was used to measure the distance between the sampling points and sources of contamination, such as liquid and solid waste dumping sites, farms, animal pens, stagnant waters, and open defecation sites. The measurements were performed in the range of 10–100 m. The Global Positioning System Coordinates (GPS) application version 1.17 was used to establish sampling locations, as described by Barcelona et al. (1985). Sampling locations were established to facilitate the easy identification of each sampling point. Furthermore, it was also done to attain one of the major characteristics of scientific research, ‘reproducibility.’

The boreholes at each sampling point were purged for about 20 min to remove the stagnant volume of water within the bore tubes. This was done to ensure that the groundwater sample was representative of the aquifer formation sampled. Purging was performed continuously until the temperature, electrical conductivity, and pH were stabilized. Measurements of these parameters at each sampling point were recorded in a field logbook.

Water samples were sent to the laboratories of the Water Research Institute, Environmental Chemistry, and Sanitation Engineering Division of the CSIR to assess their physicochemical and trace element compositions. An OAKTON PC 450 multimeter was used to measure various physicochemical parameters, including pH, electrical conductivity, temperature, and total dissolved solids. Turbidity was determined using a HACH TU 5200 turbidimeter, and the color of the water samples was assessed using a HACH DR/2010 portable data-acquisition spectrophotometer. A Jenway PFP7 flame photometer was used to determine the concentrations of the sodium and potassium cations. The classical EDTA titrimetric method was used to measure the levels of magnesium and calcium ions. The UV spectrophotometer DR 6000 was used to analyze the anions, namely, nitrate, nitrite, phosphate, sulfate, ammonium, and fluoride. The concentration of chloride was determined using the argentometric method with potassium dichromate (K₂CrO₇) as the indicator. Various water parameters such as total alkalinity, total hardness, magnesium hardness, calcium hardness, and bicarbonate were determined using titrimetric methods. Trace elements were analyzed using atomic absorption spectroscopy (AAS) with the model 240FS AA. Lastly, microbial contaminants were assessed using the membrane filtration technique at the Quality Assurance Laboratories of the Ghana Water Company Limited. Sample analysis techniques described by APHA (2012) and adopted by Iddrisu et al. (2023a, 2023b) were used.

The WQI used in the present study was adopted by Boah et al. (2015), and Ibrahim (2019), the developed weighted arithmetic water quality index. According to Ibrahim (2019), the World Health Organization (WHO) recommended that parameters with significant health implications and that are commonly detected in drinking water at significant concentrations be used as the bases for any drinking water quality assessment. Because of their direct and indirect health significance, 16 parameters were considered in the current study: pH, TDS, TH, turbidity, ⁠, ⁠, ⁠, ⁠, Cl⁻, Mn, Fe, F⁻, Na⁺, K⁺, Ca²⁺, and Mg²⁺. Table 1 shows the method of general classification of drinking water based on WQI values.

Table 2 shows the parameters, standard limit (S_i) values, unit weights (w_i), and relative weights (W_i) used in the mathematical calculation of general groundwater quality.

Table 2

The parameters, standard limits, unit, and relative weights used for general groundwater quality computation

Parameter .	Standard limit (Si) .	Unit weight (wi) .	Relative weight (Wi) .
pH	6.5–8.5	4	0.07
Na+	200	4	0.07
Mg2+	30	3	0.05
K+	30	2	0.03
Ca2+	75	3	0.05
F−	1.5	5	0.09
Cl−	250	5	0.09
	400	5	0.09
	500	1	0.02
	10	5	0.09
Mn	0.1	4	0.07
Fe	1	4	0.07
TH	200	2	0.03
TDS	500	4	0.07
	0.7	4	0.07
Turbidity	5	3	0.05

Parameter .	Standard limit (Si) .	Unit weight (wi) .	Relative weight (Wi) .
pH	6.5–8.5	4	0.07
Na+	200	4	0.07
Mg2+	30	3	0.05
K+	30	2	0.03
Ca2+	75	3	0.05
F−	1.5	5	0.09
Cl−	250	5	0.09
	400	5	0.09
	500	1	0.02
	10	5	0.09
Mn	0.1	4	0.07
Fe	1	4	0.07
TH	200	2	0.03
TDS	500	4	0.07
	0.7	4	0.07
Turbidity	5	3	0.05

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The laboratory analytical data of groundwater samples were handled and analyzed using appropriate software. Microsoft Excel version 2019, Python version 3.10.9, SPSS 2022 version, and Grapher version 20 were the software used in the analysis and handling of groundwater laboratory analytical data.

Table 4 presents a statistical summary of the physicochemical parameters analyzed in the groundwater samples used for this study. The considerable variations observed in these parameters indicate the influence of various factors within the district. This result is in line with the findings of a prior study conducted by Chegbeleh et al. (2020) in the Upper East region of Ghana, which corroborates the existence of similar patterns.

The pH levels of the groundwater samples exhibited a range from 5.61 (slightly acidic) to 8.44 (slightly basic), with an average pH value of 7.51 (see Table 3). It is important to note that, according to the WHO report from 2011, the pH of drinking water is not directly linked to consumer health concerns. However, lower pH levels can potentially lead to corrosive effects. Additionally, as highlighted by Chegbeleh et al. in their 2020 study, pH plays a significant role in influencing the dissolution of mineral elements within groundwater. Owing to this, the WHO (2011) recommends a pH range for drinking water falling between 6.5 and 8.5. Thus, it becomes apparent that not all groundwater samples collected within the Nanton District conform to this optimal pH range suitable for drinking water.

Table 3

A statistical summary of physicochemical parameters and trace elements

Parameter .	Minimum .	Maximum .	Mean .	Std. error .	WHO guidelines .
pH	5.61	8.44	7.51	0.12	6.5–8.5
Temperature (°C)	20.90	26.10	23.55	0.31	N/A
Conductivity (μS/cm)	135.00	2,240.00	782.27	91.73	1,400.00
Color (HU)	2.50	25.00	3.75	0.85	15.00
Turbidity (NTU)	1.00	39.50	3.61	1.62	5.00
Total alkalinity (mg/L)	50.00	452.00	226.91	18.43	N/A
Total hardness (mg/L)	27.20	182.60	108.43	6.33	200
Total dissolved salts (mg/L)	81.00	1,344.00	469.36	55.04	500.0
Na+ (mg/L)	15.00	380.00	108.60	16.95	200
K+ (mg/L)	1.10	8.00	2.59	0.24	30
Mg2+ (mg/L)	1.20	28.69	11.36	1.05	150.00
Ca2+ (mg/L)	6.01	54.35	24.67	1.82	200.00
Mn (mg/L)	0.01	0.27	0.04	0.01	0.4
Fe (mg/L)	0.01	1.77	0.11	0.06	0.30
(mg/L)	0.00	0.00	0.00	0.00	1.50
F− (mg/L)	0.01	1.56	0.26	0.09	1.50
Cl− (mg/L)	2.58	556.85	66.71	20.61	250.00
(mg/L)	0.00	137.00	24.68	5.31	400.00
(mg/L)	61.00	551.44	267.61	21.38	500
(mg/L)	0.00	33.18	4.12	1.82	N/A
(mg/L)	0.03	2.67	0.56	0.13	10.00
(mg/L)	0.00	0.92	0.17	0.04	0.7
Ca. hardness (mg/L)	15.00	136.00	61.67	4.55	N/A
Mg. hardness (mg/L)	4.93	118.00	46.76	4.30	N/A
Total suspended solids (mg/L)	1.00	28.00	2.70	1.06	N/A

Parameter .	Minimum .	Maximum .	Mean .	Std. error .	WHO guidelines .
pH	5.61	8.44	7.51	0.12	6.5–8.5
Temperature (°C)	20.90	26.10	23.55	0.31	N/A
Conductivity (μS/cm)	135.00	2,240.00	782.27	91.73	1,400.00
Color (HU)	2.50	25.00	3.75	0.85	15.00
Turbidity (NTU)	1.00	39.50	3.61	1.62	5.00
Total alkalinity (mg/L)	50.00	452.00	226.91	18.43	N/A
Total hardness (mg/L)	27.20	182.60	108.43	6.33	200
Total dissolved salts (mg/L)	81.00	1,344.00	469.36	55.04	500.0
Na+ (mg/L)	15.00	380.00	108.60	16.95	200
K+ (mg/L)	1.10	8.00	2.59	0.24	30
Mg2+ (mg/L)	1.20	28.69	11.36	1.05	150.00
Ca2+ (mg/L)	6.01	54.35	24.67	1.82	200.00
Mn (mg/L)	0.01	0.27	0.04	0.01	0.4
Fe (mg/L)	0.01	1.77	0.11	0.06	0.30
(mg/L)	0.00	0.00	0.00	0.00	1.50
F− (mg/L)	0.01	1.56	0.26	0.09	1.50
Cl− (mg/L)	2.58	556.85	66.71	20.61	250.00
(mg/L)	0.00	137.00	24.68	5.31	400.00
(mg/L)	61.00	551.44	267.61	21.38	500
(mg/L)	0.00	33.18	4.12	1.82	N/A
(mg/L)	0.03	2.67	0.56	0.13	10.00
(mg/L)	0.00	0.92	0.17	0.04	0.7
Ca. hardness (mg/L)	15.00	136.00	61.67	4.55	N/A
Mg. hardness (mg/L)	4.93	118.00	46.76	4.30	N/A
Total suspended solids (mg/L)	1.00	28.00	2.70	1.06	N/A

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Temperatures ranged from 20.90 to 26.10 °C, with an average of 23.60 °C. Groundwater in the Nanton District is within the natural water range for temperature. This observation could be due to the time of sampling (morning).

The WHO (2011) recommends that drinking water be colorless. The presence of color in water is typically attributed to organic matter, iron, and other corrosive substances. The presence of color in drinking water can degrade its aesthetic quality. Although there is no specific health guideline for color in drinking water, most individuals can detect colors above 15 true color units (TCU), as indicated in a WHO report (2011). Therefore, it is evident that not all groundwater samples from the Nanton District consistently meet the requirement of staying below 15 TCU for color, as observed in Table 3.

As per the WHO (2011), turbidity in water is a result of the existence of suspended particles or colloidal substances that hinder the transmission of light through the water. According to the WHO (2011), turbidity in certain groundwater sources can be caused by the presence of inert clay or chalk particles, while in anaerobic sources, it can be due to the precipitation of insoluble reduced iron and other oxides. The turbidity of groundwater samples in the Nanton District varied, with the lowest and highest recorded values being 1.00 and 39.5 nephelometric turbidity units (NTU), respectively, and an average value of 3.61 NTU. The WHO (2011) establishes the acceptable threshold for turbidity in drinking water as 5 NTU. Consequently, it is clear that not all groundwater samples from the Nanton District consistently adhere to the permissible turbidity limit.

According to the findings of Oyelude et al. (2013), a clear relationship exists between the total amount of suspended solids and turbidity. The analysis carried out in this investigation revealed a variety of values for total suspended solids, ranging from 1 to 28 mg/L, with an average concentration of 2.7 mg/L (Table 3).

Water is considered satisfactory and desirable when the TDS concentration is less than 600 mg/L, according to the WHO guidelines from 2011. However, when the TDS level exceeds around 1,000 mg/L, the taste of drinking water is affected significantly (WHO 2011). High TDS levels in drinking water can cause the accumulation of minerals in household appliances like water pipes, boilers, and heaters, which may raise concerns for consumers. However, the WHO has not established specific health guidelines for TDS (WHO 2011). TDS levels in this study ranged from 81 to 1,344 mg/L, with an average of 469.36 mg/L. (Table 3). Therefore, not all groundwater samples remained consistently within the desirable range of TDS for palatable drinking water.

The measurement of conductivity, which is also referred to as electrical conductivity, is proportional to the concentration of TDS in water (Oyelude et al. 2013). In this specific study conducted in the Nanton District, the groundwater displayed a range of conductivity values, with the lowest and highest recorded values being 135 and 2,240 μS/cm, respectively. The average conductivity value obtained was 782.27 μS/cm (Table 3). According to the WHO report (2011), the acceptable guidelines limit for conductivity in drinking water is 1,400 μS/cm. The Nanton District's groundwater samples clearly do not meet the prescribed limit for drinking water in terms of conductivity on a consistent basis.

Furthermore, the total alkalinity of groundwater recorded minimum and maximum values of 50 and 452 mg/L, with a mean value of 226.91 mg/L in the current study (Table 3). There is no established acceptable limit for total alkalinity in water for portability, according to Oyelude et al. (2013). This could be because total alkalinity is less of a health concern. Based on this, the groundwater in the Nanton District is consistently potable.

The groundwater in the Nanton District exhibited a range of total hardness values, with the minimum and maximum recorded values being 27.2 and 182.6 mg/L, respectively. The average total hardness concentration was determined to be 108.43 mg/L (Table 4). The minimum and maximum calcium and magnesium hardness values were 15 and 136 mg/L, and 4.93 and 118 mg/L, respectively (Table 3). Calcium and magnesium hardness mean concentrations were 61.67 and 46.7 mg/L, respectively (Table 4).

According to the findings of a study conducted by Oyelude et al. (2013), the palatability of water is affected by hardness, and moderately hard water, which contains calcium, is important for normal health and growth. However, water hardness caused by high levels of magnesium sulfate is considered undesirable. According to WHO, hardness in drinking water is not a health concern, and there is no specific guideline value for hardness. Based on this information, it can be concluded that the groundwater in the Nanton District is safe to drink.

The average sodium concentration in the groundwater of the study area was found to be 108.60 mg/L, with a range spanning from 15 to 380 mg/L (Table 3). The minimum and maximum potassium concentrations were measured at 1.1 and 8 mg/L, respectively, with an average value of 2.59 mg/L. While sodium and potassium do not directly impact human health, they do influence the taste and acceptability of drinking water. Elevated levels of sodium can result in a salty taste in the water. According to Chegbeleh et al. (2020), the standard limit for sodium in drinking water is 200 mg/L. Based on this standard, groundwater samples in the Nanton District consistently exceed the recommended sodium limit for drinking water. However, all potassium levels were found to be within the acceptable range for drinking water.

The groundwater samples analyzed in the study showed a diverse range of calcium concentrations, ranging from 6.01 mg/L (lowest) to 54.35 mg/L (highest). The average calcium concentration was found to be 24.67 mg/L (Table 3). Conversely, the measured magnesium concentrations are between 1.28 and 28.69 mg/L, with a mean concentration of 11.36 mg/L. Oyelude et al. (2013) emphasized that calcium and magnesium are vital elements for animal nutrition. Calcium is essential for blood clotting and bone development in all animals, while magnesium is an essential cofactor and activator for numerous enzymatic reactions. Although excess concentrations of calcium and magnesium in water can pose challenges, there is limited evidence suggesting significant health effects associated with these ions in drinking water, as reported by Oyelude et al. (2013). Thus, considering the observed calcium and magnesium concentrations, the groundwater from the Nanton District is deemed suitable for consumption in terms of these elements.

According to the WHO guidelines (WHO 2011), the acceptable limit for iron concentration in drinking water is 0.3 mg/L. This is because elevated levels of iron can result in water having an unfavorable color and taste. While iron in its iron (II) state holds significance for animal nutrition, Oyelude et al. (2013) have indicated that it does not have health implications for consumers at concentrations up to 2 mg/L. However, when iron concentrations surpass 0.3 mg/L, it can introduce objectionable color and flavor to drinking water, rendering it less appealing to consumers. In the Nanton District, the groundwater samples exhibited diverse levels of concentration of iron, ranging from 0.01 to 1.77 mg/L, with an average of 0.11 mg/L. Consequently, not all groundwater in the Nanton District adheres to the drinking water standards concerning iron content, as certain samples surpass the recommended limit of 0.3 mg/L.

The groundwater in the Nanton District shows varying manganese concentrations, ranging from 0.01 to 0.27 mg/L, with a mean concentration of 0.04 mg/L (Table 3). Based on the guidelines of the WHO (2011), the acceptable standard value for manganese in drinking water is 0.4 mg/L. Regarding manganese levels, all groundwater samples in the Nanton District consistently remain below the recommended standard for drinking water.

According to the findings of Chegbeleh et al. (2020), bicarbonate is the most abundant anion in natural waters with a pH range of 4.5–9. This observation helps explain the measured bicarbonate concentrations in this study. The bicarbonate concentrations in the groundwater samples analyzed in this study ranged from 61 to 551.44 mg/L, with a mean concentration of 267.61 mg/L. The WHO guidelines establish an acceptable standard of 500 mg/L for bicarbonate in water used for domestic purposes. Therefore, it is clear that not all groundwater samples from the Nanton District consistently meet the acceptable limits for domestic use. The higher bicarbonate levels detected could be attributed to microbial contaminants' respiratory activities or the dissolution of carbonate rocks.

Water containing elevated levels of nitrates and nitrites can pose significant health risks, especially for vulnerable populations like infants, pregnant women, and individuals with specific enzyme deficiencies. In this particular study, the measured concentrations of nitrates ranged from 0.03 to 2.67 mg/L, with a mean concentration of 0.56 mg/L. According to the WHO (2011) report, the acceptable limit for nitrate concentration in drinking water is 10 mg/L. It is clear that groundwater in the Nanton District consistently exhibits low nitrate concentrations, indicating its suitability for consumption.

The phosphate values measured in the Nanton District span from 0 to 0.92 mg/L, with a mean concentration of 0.17 mg/L. Similarly, sulfate concentrations in groundwater varied between 0 to 137 mg/L, with a mean concentration of 24.68 mg/L. According to Oyelude et al. (2013), these ions found in drinking water do not pose a direct threat to consumer health. However, at higher concentrations, they may contribute to a bitter taste in the water. The recommended phosphate and sulfate standards for drinking water are 0.7 and 400 mg/L, respectively. In this context, the groundwater in the Nanton District meets the standard for sulfate, indicating its suitability for consumption. However, the phosphate concentrations do not consistently fall within the acceptable levels for drinking water. The elevated phosphate levels could be attributed to agricultural activities in the area.

Moreover, elevated concentrations of anions such as chloride, phosphate, and sulfate can affect the flavor of drinking water. The WHO recommends a chloride level of 250 mg/L in drinking water. In the Nanton District, the range of chloride concentrations observed was from 2.58 to 556.85 mg/L, with an average concentration of 66.71 mg/L. Therefore, the chloride concentrations in the groundwater samples do not consistently meet the acceptable range for domestic use. The increased levels of chloride may be due to human activities or the dissolution of halide rocks.

The impact of fluoride on health when present in drinking water depends on its concentration and the amount consumed. As mentioned by Oyelude et al. (2013), fluoride can have beneficial effects on infants and children under the age of eight. Within the maximum acceptable limit, fluoride aids in the development of dental enamel in these age groups. However, excessive consumption of fluoridated water can cause health problems such as dental fluorosis and skeletal abnormalities. According to WHO (2011) guidelines, the acceptable limit for fluoride in drinking water is 1.5 mg/L. Fluoride concentrations in the Nanton District ranged between 0.01 to 1.56 mg/L, with an average concentration of 0.26 mg/L. Therefore, groundwater in the Nanton District does not consistently meet the acceptable standard for drinking water. Slightly elevated fluoride levels observed in certain areas may be due to the dissolution of halide rocks or human activities.

Table 2 shows the parameters, standard limit (S_i) values, unit weights (w_i), and relative weights (W_i) used in the mathematical computation of general groundwater quality.

According to the present study in the area, 46.7% of groundwater samples meet the criteria for excellent quality for drinking purposes. Additionally, 36.7% of the samples are classified as potable. However, 13.3% of the samples are classified as poor quality, with 3.3% classified as extremely poor quality. Table 4 provides a detailed overview of the sampling stations, WQI values, and general classifications.

This followed that 83.3% of untreated Nanton groundwater in the present study is of good quality and can be used without pretreatment. However, 16.7% of untreated water in the present study is not entirely safe for consumption without pretreatment. The problem could be associated with high concentrations of fluoride, TDS, pH, iron, turbidity, chloride, and manganese recorded in those areas.

The total microbial count in cfu/100 mL is the number of visible colors under a magnified colony counter that have developed under certain conditions. The membrane filtration method was adopted in this study to determine the microbial content of all groundwater samples. No coliform count should be detected in any water used for drinking purposes, according to the Ghana standard for microbial count in drinking water. Table 5 presents the results of the microbial content of all groundwater samples.

In a research study carried out by Javaid et al. (2022), the total count of coliform bacteria is recognized as a significant indicator of the potential existence of pathogenic microorganisms in drinking water. An elevated level of total E. coli in drinking water suggests the potential presence of other detrimental organisms. The guidelines set by the Ghana Standards Authority and the WHO require that there be no detectable total coliform count in any drinking water supply source. When E. coli is found in drinking water, it indicates a higher risk of pathogenic bacteria and fecal contamination than the presence of total coliforms. While E. coli is a naturally occurring pathogen in the intestinal tracts of humans and warm-blooded animals, its presence in drinking water indicates the presence of potentially harmful pathogens. Both the WHO and Ghana's standards stipulate that no germs, including E. coli or Salmonella, should be detected in drinking water from either private or public sources. As presented in Table 5, except for sample CY, which had a zero count of E. coli, all groundwater samples tested in the Nanton District displayed microbial contamination. This clearly indicates that without pretreatment, the groundwater in Nanton is not safe for consumption. The sources of contamination are likely related to poor sanitary conditions and practices in the area. These findings align with a December 2022 report by the Ghana Ministry of Sanitation, which states that E. coli was found in 5 out of 10 springs and 8 out of 10 domestic water supplies in Ghana (Mohammed-Nurudeen 2022).

Under certain conditions, quality parameters such as pH and temperature are known to favor coliform bacteria survival and growth. As shown in Figure 4, pH shows a significant inverse relationship with all the microbial contaminants. This clearly suggests that the recorded pH in Nanton groundwater could be influencing the coliform bacteria growth and survival. This is an indication that bacteria growth and survival in groundwater are favored by a decrease in pH (slightly acidic conditions). This observation agrees with the findings of Seo et al. (2019). However, temperature correlated weakly with all the microbial contaminants. This suggests that below the prescribed optimum temperatures (35–40 °C) for bacteria growth, temperature becomes unfavorable for coliform bacteria survival in groundwater. This observation could be due to the relatively low temperatures recorded during the sampling time.

Turbidity and color are physical parameters that influence microbial survival in groundwater. High turbidity and colored water may create a conducive environment for microbial survival and growth in water. As presented in Figure 4, turbidity and color show a significant positive correlation with all the recorded microbial contaminants. This suggests an indication of the influence of turbidity and color on coliform bacteria survival and growth in water. This observation could be due to the relatively high turbidity and color recorded in some areas.

Phosphate and nitrate are known nutrient sources for coliform bacteria growth and survival in groundwater. However, inadequate availability and high competition for these nutrients among coliform bacteria in water affect their growth. Also, excess of these nutrients in water may promote the growth of other microorganisms in water. This increases competition among other microorganisms and coliform bacteria affecting their survival and growth. As illustrated in Figure 4, there is a significant negative correlation between phosphate, nitrate, and all of the recorded microbial contaminants. This observation agrees with the findings of Seo et al. (2019), who also recorded a similar trend between coliform bacteria and nitrite–nitrogen in their study. This suggests high competition for these nutrients among the recorded coliform bacteria and probably other microorganisms. This observation could be owing to the low phosphate and nitrate concentrations recorded in groundwater samples. According to Abimbola (2014), low levels of nitrates in groundwater could also be attributed to the actions of bacteria on plants, which would lead to the degradation of nitrate concentrations within the aquifer matrixes.

Iron and manganese are other important elements known to support coliform bacteria growth and survival. Also, iron is known to aid coliform bacteria in producing stable biofilms, which enables them to adhere to surfaces. Iron and manganese both correlated well with all the recorded microbial contaminants. This observation could explain the survival of these organisms, even though phosphate and nitrate levels recorded in groundwater are relatively low. This could also explain why some areas have relatively high levels of iron and manganese. The sources of these elements could be owing to the non-cleaning and disinfection of storage tanks used to collect groundwater water supplies. An extended period of non-cleaning and disinfection of contaminated water storage tanks can enhance the formation of biofilms by coliform bacteria. This could lead to clogging of pipes and other water supply materials.

Figure 5 illustrates the hierarchical arrangement of major cations in Nanton's groundwater, with Na⁺ being the predominant ion, followed by Ca²⁺, Mg²⁺, and K⁺. Similarly, the primary anions are presented in the sequence of ⁠, Cl⁻, ⁠, and ⁠.

The chemistry and quality of Nanton groundwater are analyzed using analytical laboratory data from groundwater samples. To identify the natural factors influencing its chemistry, the Gibbs diagram is utilized. These factors, as emphasized by Ratri et al. (2021), encompass evaporation, water–rock interaction, and precipitation.

To gain further insights into the impact of silicate weathering on groundwater, a scatter plot depicting the concentrations of chloride versus sodium ions, both measured in milliequivalents, is employed, as cited by Karunanidhi et al. (2020).

The scatter plot of versus is used to identify the dissolution of calcite or dolomite and gypsum mineral rocks in groundwater, according to Karunanidhi et al. (2020) Calcite or dolomite dissolution is suggested by samples plotted with <10 mEq/L. Samples plotted with >10 mEq/L, on the other hand, indicate gypsum dissolution.

To determine further the influence of gypsum dissolution on Nanton groundwater chemistry, a plot of Ca²⁺ versus was examined. According to Xiao & Gu (2017), a linear relationship between these ions on a scatter plot shows gypsum dissolution as the main source of calcium ions in groundwater.

As shown in Figure 9(b), most groundwater samples do not consistently show a linear relationship between calcium and sulfate ions except for a few. This clearly confirms that gypsum dissolution does not significantly contribute calcium ions in Nanton groundwater but calcite dissolution.

A plot of versus (⁠⁠) is another technique used to understand the impact of rock mineral weathering on groundwater chemistry. Gugulothu et al. (2022) used a plot of versus (⁠⁠) to understand the impact of rock mineral weathering and ion exchange on groundwater chemistry. Samples plotted above the equiline of the versus (⁠⁠) plot suggest the dominance of Ca²⁺ and Mg²⁺ ions over ions caused by rock mineral weathering or cation exchange, according to Gugulothu et al. (2022). And, as cited by Gugulothu et al. (2022), samples plotted below the equiline confirm the release of into groundwater by feldspar mineral weathering with carbonic acid. Figure 8 depicts a scatter plot of Nanton groundwater laboratory analytical data versus (⁠⁠).

In this study, it was found that 60% of groundwater samples are positioned above the equiline, suggesting that the primary source of Ca²⁺, Mg²⁺, and ions in Nanton groundwater is the dissolution of carbonate minerals. Conversely, 40% of the samples are positioned below the equiline, suggesting that feldspar mineral dissolution with carbonic acid serves as an additional source of these ions. These findings highlight the significant contribution of carbonate mineral dissolution to the presence of Ca²⁺, Mg²⁺, and ions in Nanton groundwater. According to Xiao & Gu (2017), a molar ratio of ≤0.5 signifies carbonate dissolution as the main source of calcium and magnesium ions in groundwater. In this study, the calculated molar ratio of was found to be 0.5, providing further evidence for carbonate dissolution as the primary source of calcium and magnesium ions in Nanton groundwater. This finding is supported by the scatter plot of versus depicted in Figure 9(c), as well as the geological characteristics of the study area.

According to El-Rawy et al. (2023), gaining insight into the water–rock interaction mechanism is essential for verifying the diverse variations associated with geochemical processes occurring in groundwater, whether during residence or transportation within the groundwater system. The chloro-alkaline indices (CAI1 and CAI2) introduced by Schoeller are employed to assess the influence of ion exchange between sodium or potassium and calcium or magnesium in groundwater and the aquifer matrix. As cited in other studies by researchers like Soro et al. (2019), El-Rawy et al. (2023), and Talib et al. (2019), negative values of the chloro-alkaline index (CAI) indicate the occurrence of reverse ion exchange of calcium or magnesium in aquifer matrix with sodium or potassium in the groundwater. This process decreases sodium or potassium concentration in groundwater and increases calcium or magnesium concentrations in groundwater. Conversely, positive values of the CAI indicate direct ion exchange of sodium or potassium in the groundwater with calcium or magnesium in the aquifer matrix. The phenomenon, conversely, increases sodium or potassium concentrations in groundwater while calcium or magnesium concentrations decrease in the water. Table 7 is the statistical summary of CAI values computed for the current study.

The CAI-I values in groundwater vary significantly, ranging from −38.88 to 14.71. The mean CAI-I values of −5.0513 indicate an overall negative trend. Similarly, the CAI-II values have a narrower range, with a minimum of −0.58 and a maximum of 10.74. The mean CAI-II value of 0.9642 indicates a slightly positive trend.

Based on Figure 10(b), the groundwater samples exhibit clear placement in the positive and negative regions of the CAI values I and II, with only a few samples positioned near the origin. This indicates the significant involvement of both direct and reverse ion exchange processes in shaping the chemistry of Nanton groundwater, except in specific areas where the impact of ion exchange is minimal. While sodium is identified as the dominant cation in this study, certain regions demonstrate low sodium concentrations, suggesting the occurrence of reverse ion exchange. This observation is further supported by the low levels of potassium. Conversely, the relatively elevated presence of calcium and magnesium substantiates the influence of direct cation exchange, where these ions are released into the groundwater at exchangeable sites like soil or aquifer matrices, subsequently adsorbing sodium ions at these locations. This mechanism effectively decreases the concentrations of sodium or potassium ions while increasing the concentration of calcium or magnesium, a process commonly known as natural hardening. These findings highlight the diversity of groundwater conditions and provide valuable insights into the impact of ion exchange in Nanton groundwater geochemical processes.

Karunanidhi et al. (2020) studied the relationship between ions and TDS using a correlation matrix. A strong positive correlation between ions and TDS indicates anthropogenic sources of such ions, as cited by Karunanidhi et al. (2020).

Madhav et al. (2020) also adopted this method to study the input of anthropogenic activities as a factor influencing groundwater chemistry. Anthropogenic activities such as farming and disposal of liquid, solid, and animal wastes around groundwater sources were observed during the hygiene survey. As presented in Figure 4, sodium correlated strongly with TDS, suggesting anthropogenic activities as a significant source of sodium ions in Nanton groundwater. Other cations, such as calcium, magnesium, and potassium, correlated significantly well with TDS. This suggests anthropogenic activities contribute partly as sources of these ions in Nanton groundwater. This observation is further confirmed by the observed strong correlation between total alkalinity and total dissolved solids and well correlated with pH and total hardness of groundwater. The anions, such as carbonate, bicarbonate, fluoride, chloride, and sulfate, correlated weakly with TDS. This suggests that anthropogenic activities are minor sources of these ions in Nanton groundwater. The positive correlation between fluoride and phosphate also suggests fertilizer application as one of the minor anthropogenic sources of fluoride in groundwater. Also, the good correlation between chloride and fluoride, as well as magnesium and fluoride, could be a result of halide dissolution or anthropogenic activities, as cited by Madhav et al. (2020). However, the strong correlation between nitrate and phosphate shows they could be coming from the same source, such as fertilizer application or domestic and animal wastes. This suggests anthropogenic activities as significant sources of nitrate and phosphate ions in Nanton groundwater.

This study aimed to assess groundwater quality in Ghana's Nanton District, providing crucial insights for sustainable water management and public health. Physicochemical analysis indicated that most groundwater is suitable for drinking without treatment, except in specific areas with elevated levels of contaminants such as turbidity, sulfate, color, bicarbonate, fluoride, iron, sodium, TDS, and pH. However, all groundwater samples were found unfit for direct consumption due to microbial contaminants, including total coliform, E. coli, and Salmonella bacteria, highlighting sanitation concerns in the area. The study also identified specific physicochemical parameters, including pH, iron, manganese, nitrate, sulfate, turbidity, and color, as influencing the presence of microbial contaminants in groundwater. Hydrochemical analysis revealed the distribution of major ions in Nanton's groundwater, with predominant cations being Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and anions being > Cl⁻ > > ⁠. Various water types were identified, including ⁠, ⁠, ⁠, and mixed water. The study elucidated the principal factors governing groundwater chemistry, including rock mineral weathering, evaporation, ion exchange, and human activities, as confirmed by Gibbs diagrams and scatter plots. Pearson's correlation matrix reaffirmed the influence of anthropogenic sources on ion presence in Nanton's groundwater. However, the study has limitations, primarily its focus on groundwater quality at the time of sampling without accounting for seasonal variations. Additionally, it primarily examines physicochemical and microbial aspects, leaving room for further research on other potential contaminants and sources in the groundwater. The findings underscore the need for targeted interventions, including waterborne disease awareness campaigns and pretreatment of point-source and household water, particularly in areas with suboptimal water quality. Also, education on good sanitary practices and water resource protection in the area should be intensified. Transparent storage tanks for boreholes directly connected to storage facilities can enhance water quality. Further research is recommended to explore the relationship between coliform bacteria and physicochemical water parameters. Additionally, a comprehensive investigation into contaminant sources in the groundwater is crucial for effective strategies to protect the region's water resources. This study's insights are valuable for policymakers, water resource managers, researchers, and stakeholders in the water and sanitation industry, guiding efforts toward sustainable water resource management in the Nanton District.

The authors are grateful to the School of Chemical and Biochemical Sciences, C.K. Tedam University of Technology and Applied Sciences and Water Research Institute, Environmental Chemistry and Sanitation Engineering Division, Ghana, for making their laboratories available for this research to be carried out.

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

The authors declare there is no conflict.