ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT AZOJETE June 2023. Vol. 19(2):183-196 Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria. Print ISSN: 1596-2490, Electronic ISSN: 2545-5818 www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 183 ORIGINAL RESEARCH ARTICLE EVALUATION OF GROUNDWATER QUALITY FOR DRINKING PURPOSES USING WATER QUALITY INDEX, IN KEFFI CENTRAL TOWN OF NASARAWA STATE A. A. Sodangi, O. J. Akinyeye, W. E. Esuabanga and C. O. Nwafor Nigerian Building and Road Research Institute, Ota, Ogun State, Nigeria *Corresponding author’s email address: sodangiali2020@gmail.com 1.0 Introduction Water is a transparent, tasteless, odourless, and colorless chemical substance that is the main constituent of the earth's hydrosphere and is the fluid of living organisms. The expansion of economic activities and the increasing population are leading to increased demand for water. Water has played a vital role throughout the history in the development of human civilization. Groundwater is the water that lies beneath the earth’s surface, filling the pore space between grains in bodies of sediment and elastic sedimentary rock and filling cracks and crevices in all types of rock (Abdullahi and Iheakanwa, 2013). About 98% of the World's freshwater is from groundwater and is distributed throughout the world (Tijani, 2016). Demand for groundwater has been on the increase because of rapid growth in population as well as the accelerated pace of industrialization and urbanization. The groundwater quality depends on several chemical constituents and their concentration, which are derived from geological data. Environmental and industrial solid wastes have emerged as one of the leading factors of groundwater pollution. ARTICLE INFORMATION ABSTRACT In Nigeria, access to fresh drinking water has become serious challenges to both rural and urban areas.The aim of this study was to evaluate groundwater quality in Keffi central town of Nasarawa State for drinking purposes using the water quality index technique. Eight groundwater samples (four from both boreholes and dug wells) were collected from the study areaduring the wet season in October 2019. The water quality index is a mathematical method used to facilitate water quality explanation. The pH, Electric Conductivity, Total Dissolved Solids, Total Hardness, Calcium, Magnesium, Sodium, Chloride, Sulphate and Bicarbonate were determined according to standard methods. pH ranged from 5.7 to 7.1(mg/l), Electric conductivity ranged from 256 to 1591(µs/cm), Magnesium ranged from 2.6 to 29(mg/l), Calcium ranged from 3.7 to 34(mg/l), Sodium ranged from 22 to 56(mg/l), Chloride ranged from 8.4 to 63(mg/l), Bicarbonate ranged from 54.3 to 219.6(mg/l), Sulphate ranged from 0.1 to 32.4(mg/l), Total Dissolved Solids ranged from 95.2 to 302.94(mg/l) and Total Hardness ranged from 23.8 to 204.23(mg/l). The water quality index obtained from different locations was found to vary from 44.32 to 61.60 for boreholes and 72.55 to 97.77 for dug wells. The results for the water quality index indicated that borehole locations 2, 4, and 8were safe for human consumption, while dug well locations 3,5,6 and 7were not suitable for drinking purposes, compared with Nigerian industrial standard drinking water. The reasons for the high water quality index values of some study areas were attributed to the lithological variation and anthropogenic activities in the region. Therefore, some of the well water required treatment such as demineralization. © 2023 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved. Submitted 14 October, 2022 Revised 12 December, 2022 Accepted 12 February, 2023 Keywords: Groundwater water quality index water quality parameters Keffi central http://www.azojete.com.ng/ file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com sodangiali2020@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June, 2023; Vol. 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 184 Available water is rendered non-portable in many parts of the country like Somalia because of the presence of heavy metals. In urban areas fresh water accessibility is more than the rural areas, because the urban areas have a lot of public water supply infrastructure for fresh water consumption. However, this statement is in contrast with the studies of Durowojo et al. (2022) as thy averred that in urban areas, fresh water accessibility issues are really the same with the rural areas, owing to the inadequate investigation in public water supply infrastructure that lay down pipe-bone water consumption undependable. In urban areas, fresh water accessibility issues are really the same with the rural areas, owing to the inadequate investigation in public water supply infrastructure that lay down pipe-borne water consumption undependable (Durowojo et al., 2022). In Keffi central, access to clean water is a major challenge to the residents. The consequence of water scarcity in some communities in the area, most especially during the middle of the dry season often results in the outbreak of water-borne diseases such as typhoid, cholera, diarrhoea, and guinea worm. With the efforts of government agencies and international agencies like Nasarawa State Ministry of Water Resources (NSMWR), United Nations International Children Emergency Fund (UNICEF), and The European Union (EU), some significant successes have been recorded in making safe drinking water available to few communities and therefore, curbing the menace of these diseases (Chiroma et al., 2018). Water quality index (WQI) provides a single number that signifies the overall water quality at a certain location based on several water quality parameters. It is an effective tools and important parameters in the evaluation and management of groundwater quality (Wu Jianhau et al., 2011). The objective of WQI is to transform complex water quality data into information that is understandable and useful to the stakeholders and the general public. Several indices have been developed to summarize water quality data in an easily expressible and understood format. The WQI which was first developed by Horton in the early 1970s, is a mathematical method of calculating a single value from multiple test results (Etim et al., 2013). The quality and availability of groundwater have deteriorated due to some factors such as increasing industrialization, population, and urbanization. The frequency of monitoring and assessment of water quality helps to develop management strategies to control groundwater pollution (Yao et al., 2010). The water quality of any specific area can be assessed using physical, chemical, and biological parameters. If the values of these parameters occurred more than the defined limit, they become harmful to human health (Shweta et al., 2013). The traditional approaches to assessing water quality are based on a comparison of experimentally determined parameters with local or international standards. While, these procedures allow the good recognition of contamination sources and may be necessary for checking legitimate compliance, but they don’t give a comprehensive vision of the spacial and temporal trends in the overall water quality (Shaif et al., 2017). This work aims to evaluate the suitability of groundwater quality in Keffi central town using a water quality index for drinking purposes. Water quality index was first proposed by Horton (Palwasha et al., 2020). It is a rating given to the water sample on the basis of calculated chemical parameters. WQI is a compilation of a number of variables which can be used to determine the overall quality of river and ground water file:///C:/user/Downloads/azojete143/www.azojete.com.ng file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Sodangi et al: Evaluation of Groundwater Quality for Drinking Purposes using Water Quality Index, in Keffi Central Town of Nasarawa State. AZOJETE, 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 185 (Ashwani and Anish, 2009). Ten parameters were used for calculation of WQI as suggested by Fadhil et al. (2013). These includes: Magnesium, Sodium, Calcium, Chloride, Sulphate, Bicarbonate, pH, Total Dissolved Solids, Total Hardness, and Electric Conductivity. Water quality index (WQI) provides a single number that signifies the overall water quality at a certain location based on several water quality parameters. It is an effective tools and important parameters in the evaluation and management of groundwater quality (Wu et al., 2011). The objective of WQI is to transform complex water quality data into information that is understandable and useful to the stakeholders and the general public. Several indices have been developed to summarize water quality data in an easily expressible and understood format. The frequency of monitoring and assessment of water quality helps to develop management strategies to control groundwater pollution (Yao et al., 2010). The water quality of any specific area can be assessed using physical, chemical, and biological parameters. If the values of these parameters occurred more than the defined limit, they become harmful to human health (Shweta et al., 2013). The traditional approaches to assessing water quality are based on a comparison of experimentally determined parameters with local or international standards. While, these procedures allow the good recognition of contamination sources and may be necessary for checking legitimate compliance, but they don’t give a comprehensive vision of the spatial and temporal trends in the overall water quality (Shaif et al., 2019). This work aims to evaluate the suitability of groundwater quality in Keffi central town using a water quality index for drinking purposes. 2. Materials and methods 2.1 Study area Keffi Central lies between latitudes 8o 50l and 8o 52lN and longitude 7o 52l and 7o 54lE (Figure1). The area is within north-central Nigeria and is characterized by wet and dry seasons. The temperature ranged from 21.3oC to 31.6oC. The area was drained River Antau, River Kodo, and River Mannu. The area falls within the North-central Nigeria basement complex, precisely within the migmatite gneiss complex. The Nigeria’s basement complex consists of migmatites and migmatitic gneisses, slightly migmatized to unmigmatized paraschists with interbeds of meta and non meta Igneous rocks, also referred to as the younger metasediments or the Schist belts (Ajibade, 1976, and Turner, 1983). In the Keffi area, there are not many records of the detailed work carried out on the various units of the basement complex. Most parts of the area studied had already been mapped as underlain by the migmatites and migmatitic gneisses. The occurrence of a schist belt was only shown in parts of the area in the geological map of Nigeria produced by the geological survey of Nigeria (NGSA, 1994). Using their geochemistry and rare-earth element analysis, Onyeagocha (1986), pointed out that the granite is younger than the granite-gneiss; that Al/(Na+K+Ca) ranges from 0.92 to 1.09, indicating that the rocks are aluminium rich to aluminium excess. The availability of groundwater would depend on the presence and extent of the weather overburden regolith and the presence of faults and fractures in the underlying bedrock http://www.azojete.com.ng/ file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June, 2023; Vol. 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 186 (Olayinka et al., 1999). Dissolution of minerals and leaching tends to increase porosity, permeability, and specific yield. However, the decomposition of secondary clay minerals tends to reverse the process (Tijani, 1994). Figure 1: Map of the study area showing Groundwater sampling locations. 2.2 Sample collection Groundwater samples were collected from8 locations of central part of Keffi town in the month of October 2019. Groundwater samples were collected in new dry clean plastic bottles after rinsed three times with the samples to be collected, using standard procedures recommended by Amadi et al. (2013) method. Physicochemical parameters including electrical conductivity (EC) and pH were measured in situ using HANNA EC and pH meter respectively. The collected samples were labeled, transported to The Bells University laboratory Ota, Ogun State for further analysis. The chemical parameters analyzed include: calcium, magnesium, sodium, chloride, sulphate and bicarbonate. Total Dissolved Solids (TDS) was determined according to Tripathi et al. (2012). Total hardness (TH) was determined using standard procedures recommended by Nematollah et al. (2016). In the present study water quality index were determined. All chemical concentrations were expressed in mg/l. Coordinates of each well location were identified using Global Positioning System (GPS) as shown in Table 1. Table 1: Geographical locations of the studied Wells. Well L a t i t u d e Longi tude Elevation (m) 1 8050 l10.614 l l 7 052 l30.027 l l 3 0 9 . 5 2 8o50 l38.074 l l 7 052 l21.110 l l 3 0 2 . 3 3 8 0 50 l 42 . 38 l l 7 052 l12.075 l l 3 0 2 . 1 4 8 0 50 l 19 . 37 l l 7 052 l40.056 l l 3 0 5 . 2 5 8050 l59.013 l l 7 052 l28.108 l l 3 1 1 . 4 6 8 050 l 58.34 l l 7 052 l58.026 l l 3 0 3 . 4 7 8050 l11.022 l l 7 052 l26.528 l l 3 1 2 . 8 8 8050 l39.161 l l 7 052 l24.341 l l 3 0 5 . 9 Location file:///C:/user/Downloads/azojete143/www.azojete.com.ng file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Sodangi et al: Evaluation of Groundwater Quality for Drinking Purposes using Water Quality Index, in Keffi Central Town of Nasarawa State. AZOJETE, 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 187 2.1. Water quality index calculation Water quality index was first proposed by Horton (Palwasha et al., 2020). It is a rating given to the water sample on the basis of calculated chemical parameters. WQI is a compilation of a number of variables which can be used to determine the overall quality of river and ground water (Ashwani and Anish, 2009).The WQI Water quality index was calculated for each well location by using ten parameters namely: TDS, TH, pH, EC, Mg2+, Na+, Ca2+, SO2- 4, Cl-, and HCO- 3 according to Nigeria’s drinking water standard for each chemical parameter. The weighted arithmetic index method as applied by Brown et al. (1972) and Dhirendra et al. (2009) was used, and presented below: The constant of proportionality was calculated by finding the inverse of Nigeria Industrial Standard (NIS) limit for each parameter (Fadhil et al., 2013). Then sum the results of the inverse, finally find the inverse of the summation of the result. k = 1 ∑ 1 𝑆𝑖 𝑛 𝑖=1 (1) Where: K= constant of proportionality Si= permissible limit of Nigerian Standard for Drinking Water Quality for the ith parameter n=number of parameters Calculating the weightage of ith parameter (relative weight) Wi by using equation as shown in Table 3 The expression means the relative weight equation: The relative weight was calculated by dividing the constant of proportionality by NIS limit for each parameter (Fadhil et al., 2013). (2) Calculating of the quality rating scale (Qi) by the expression due to Fadhil et al. (2013): (3) In which Ci is the concentration of the ith parameter Ci is the concentration for each chemical parameter in each water sample (mg/l) Calculating water quality index (WQI) as follows (Fadhil et al., 2013): Water quality index is given as: (4) The data collected was substituted into the equations above for computation of water quality index values, with the help of statistical method. Si k Wi = Si Ci Qi 100 =   = == n i n i Wi QiWi WQI 1 1 http://www.azojete.com.ng/ file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June, 2023; Vol. 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 188 The physicochemical parameters of Keffi central town with their NIS water quality prescribed values corresponding weightage factor (Wi), assigned with the help of equation 1 and 2 and the values are presented in Table 2. Table 2: Relative weight for each parameter Chemica l parameters Highest permitted value for water (1/Si) 1 / S i K W i P h 8.5 0.117647 0.556733 EC 1 0 0 0 0.001 0.004732 Hardness 150 0.00667 0.031548 T D S 500 0.002 0.009464 Calcium 2 0 0 0.005 4.732227 0.023661 Magnesium 2 0 0.05 0.236611 Sodium 2 0 0 0.005 0.023661 Bicarbonate 1 0 0 0 . 0 1 0.047322 Su l f a t e 1 0 0 0 . 0 1 0.047322 Chloride 2 5 0 0.004 0.018929 Total 0.211317 1 .0 3. Results and Discussion 3.1 Water Quality Characteristics The concentration of all water quality parameters of Keffi central town are presented in Table 3. The pH ranged from 5.7 to 7.1 mg/l with an average of 6.3mg/l which indicated that the ground water is slightly acidic to neutral. All the values fell below the acceptable limit being prescribed in Nigerian industrial standard (NIS 2015) for drinking water. Electrical conductivity (EC) measures the salt concentration and provides indication of ionic concentration in the water. EC varied between 256 to 1591 µs/cm with an average of 812.25 µs/cm. Only locations 5 and 7 had their EC values above the acceptable limit (>1000) of Nigerian drinking water standards. It may be attributed to high dissolution of ions in the locations (Figure 2). The concentration of all water quality parameters of Keffi central town are presented in Table 2 The pH ranges from 5.7 to 7.1 mg/l with an average of 6.3mg/l which indicated that the ground water is slightly acidic to neutral. All the values fell below the acceptable limit being prescribed in Nigeria industrial standard (NIS 2015) for drinking water. The pH of most natural water bodies ranged from 6.5 to 8.5 while the disparity from neutral pH is as a result of free carbon dioxide or bicarbonate in the water bodies (Etim et al., 2013). The lowest value of pH was recorded in borehole location 4 and 8 because they were closed to the dumpsite. The result was presented in Figure 2. Electrical conductivity (EC) measures the salt concentration and provides indication of ionic concentration in the water. EC varied from 256 to 1591 µs/cm with an average of 812.25µs/cm. In the study area only dug well locations 5 and 7 have their EC values above the acceptable limit (>1000) of Nigeria drinking water standards. Higher values of the two locations were attributed to high dissolution of ions in the region (Figure 2). A lower EC value indicated less concentration of the dissolved ions and organic matter in the water. file:///C:/user/Downloads/azojete143/www.azojete.com.ng file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Sodangi et al: Evaluation of Groundwater Quality for Drinking Purposes using Water Quality Index, in Keffi Central Town of Nasarawa State. AZOJETE, 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 189 Table 3: Values of some water quality parameters of Keffi central. W e l l p H E C T H T D S C a M g N a CHO3 1 6 . 8 2 5 6 3 9 . 4 1 8 0 6 . 9 5.4 38 1 8 3 2 5 . 7 7 3 1 4 5 . 3 6 99.85 8 . 2 6.05 35.1 5 8 3 7 . 1 9 4 1 204 .23 277.8 3 4 29 56 219.6 4 5 . 8 6 1 7 2 3 . 7 5 95.2 4 . 9 2.8 27.2 6 2 5 6 1 0 8 5 121 .36 166.5 1 4 21 39 7 5 6 6 . 7 8 5 4 201 .59 226.7 2 8 22 22 125 7 6 . 9 1 5 9 1 162 .04 302.94 2 7 23 55 170.8 8 5 . 7 4 1 6 1 9 . 9 3 80.28 3 . 7 2.6 30.2 54 .3 Figure 2: The values of PH and electrical conductivity for all wells. Total dissolved solid (TDS) ranged from 80.28 to 302.9 mg/l with an average of 178.57 mg/l. This is far below the permissible limits (<500) being prescribed in (NIS 2015) for drinking water. Hence, the water is not harmful in view of these parameters, and this agrees with Afolabi and Olutomilola (2017). Hardness due to bicarbonate of calcium and magnesium is temporary hardness but hardness due chloride and sulphate of calcium and magnesium is permanent hardness. Due to permanent hardness soap consumption will be more. Total dissolved solid (TDS) is a measure of the inorganic salts and little amount of the organic matter present in solution. TDS ranged from 80.28 to 302.9 mg/l with an average of 178.57 mg/l. This is far below the permissible limits (<500) being prescribed in (NIS 2015) for drinking water. Hence, the water is not harmful in view of these parameters, and this agrees with Afolabi and Olutomilola (2017). Again, TDS in drinking water has been associated with natural source, sewage and industrial waste water (Figure 3). Hardness due to bicarbonate of calcium and magnesium is temporary hardness but hardness due to chloride and sulphate of calcium and magnesium is permanent hardness. Due to permanent hardness soap consumption will be more. The highest TH value was observed to be 204.23mg/l at dug well location 3 and lowest value was observed to be 19.93mg/l at borehole location 8. However, the TH at dug well locations 3, 6 and 7 were found to be above the allowable limit (>150) being prescribed in NIS (2015) for safe drinking 0 200 400 600 800 1000 1200 1400 1600 1800 1 2 3 4 5 6 7 8 P H /E le ct ri c co n d u ct iv it y( µ S/ cm ) Well number PH EC http://www.azojete.com.ng/ file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June, 2023; Vol. 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 190 water. The reasons for the high TH values of the three samples were attributed to the lithological variation and anthropogenic activities in the area. The values indicate soft to moderately hard type of groundwater (Ashwani and Abhay, 2014). Hard water is mainly account of the unpleasant taste and reduces the ability of soap to produce lather (Figure 3). Figure 3: The values of Total dissolve solid and Total hardness for all wells Calcium is naturally present in water. It serves in our body as muscle contractor and blood clothing. Calcium is a cation found in water which makes water hard. The concentration of calcium ranged from 3.7 to 34mg/l with a mean of 15.8mg/l. The result indicated that all the values were below the acceptable limit (<200) being prescribed in (NIS, 2015) for safe drinking water. Inadequate intake of Calcium may lead to hypertension, stroke and kidney stone (Farhad et al., 2017). The concentration of Magnesium ranged from 2.6 to 29 mg/l with an average of 13.95 mg/l. This showed that all the values analyzed fell below permissible limit (<20) being prescribed in (NIS 2015) for safe drinking water. The high values of magnesium in these four samples may be as a result of dissolution of magnesium bearing mineral, example Aragonite in the location. Both Calcium and Magnesium concentrations have been originated from the dissolution of carbonate minerals such as dolomite and calcite (Figure 4). Sodium is an essential element for keeping human body in good working condition and help in maintaining blood pressure. Concentration of sodium varied from 22 to 56 mg/l with a mean of 37.8mg/l. This signified that all the values were below the acceptable limit (<200) being prescribed in (NIS, 2015) for drinking water. Also indicated little or lack of salt bearing mineral in the locations. Excess sodium in water can affect person suffering from heart and kidney problems (Gupta et al. 2004) as showed in Figure 4. In the study area the different of the Sodium concentration indicated weathering of feldspar bearing mineral. 0 50 100 150 200 250 300 350 1 2 3 4 5 6 7 8 To ta l D is so lv e d S o lid s/ To ta l H ar d n e ss (M g/ l) Well number TDS TH file:///C:/user/Downloads/azojete143/www.azojete.com.ng file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Sodangi et al: Evaluation of Groundwater Quality for Drinking Purposes using Water Quality Index, in Keffi Central Town of Nasarawa State. AZOJETE, 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 191 Figure 4: The values of Calcium, Magnesium Sodium for all wells Chloride concentration in the water may be result from the evaporation of Chloride bearing mineral which are soluble to the water. Chloride concentration ranged from 8.4 to 63 mg/l with average of 2 5.59mg/l, which indicated that all locations were found to be below the acceptable limit (<250) being prescribed in (NIS, 2015) for drinking water. The low values of chloride in the study area were attributed to lack of deposition of salt spray. Most water contains Chloride and the amount present could be caused by fertilizer, air, industrial and domestic waste. In addition weathering of halite and evaporate were the major lithologic source of Chloride in the groundwater. High Sulphate (SO4 2-) concentration in groundwater could be as a result of contamination of untreated industrial and domestic waste. Sulphate concentration varied from 0.1 to 32.4 mg/l with mean of 12.4 mg/l. This showed that no abnormal value was present in the water samples. This occurred because of low dissolution of sulphate bearing mineral (Gypsum) in the location. All the values fell below the acceptable limit being prescribed in (NIS 2015) for safe drinking water. Water containing high concentration of SO4 2-, caused by the leaching of natural deposits of Magnesium Sulphate (MgSO4) or Sodium Sulphate (NaSO4) and may be undesirable because of their laxative effect. Higher concentration of Sulphate may lead to gastrointestinal irritation especially when Magnesium and Sodium are present in drinking water resources (Farhad et al., 2017). The concentration of Bicarbonate (HCO3 -) varied from 54.3 to 219.6 mg/l with the mean of 118.46 mg/l. All the water samples in the locations were below permissible limit (<100), except borehole location 1 and dug well location 3, 6 and 7 values were higher than the permissible limit being prescribed in NIS 2015 for safe drinking water, this could be attributed to the weathering of carbonate minerals in rain water, example limestone (Figure 5). In addition, weathering of carbonate and alumino-silicate minerals with secondary contribution from dissolution of CO2 gasses are primary source of HCO3 in the groundwater. 0 10 20 30 40 50 60 1 2 3 4 5 6 7 8 C al ci u m /M ag n e si u m /S o d iu m (M g/ l) Well number Ca Mg Na http://www.azojete.com.ng/ file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June, 2023; Vol. 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 192 Figure 5: The values of Chloride, Sulphate and Bicarbonate for all wells 3.2 Water quality index analysis The physicochemical parameters of Keffi central town with their NIS water quality prescribed values corresponding weightage factor (Wi), assigned with the help of equation 1 and 2 and the values are presented in Table 3. WQI were calculated from Equations 3 and 4. The WQI results are shown in Table 4. Classification of all the water samples were categorized by taking the standard water quality index bases which are shown in Table 5. Obtained results revealed that location 2, 4 and 8 met the requirement of safe drinking purpose as agreed with the standard proposed by Mishra and Patel (2001). However, location 1, 3, 5, 6 and 7 could not meet the requirement, due to the lithological variation and leachate from solid waste disposal site in the area. Therefore, the water cannot be used for human consumption. The WQI values of the 8 locations were found range from good to very poor-quality, or from 26-50 and 76-100.The statistical summary of the physicochemical parameters analyzed are showed in Table 6. Table 4: Details of the index rate and type of water for the various samples obtained in the analysis Location T y p e Index rate Type of water 1 Bore we l l 6 1 . 6 0 Poor water 2 Bore we l l 4 9 . 6 4 Good water 3 D u g w e l l 9 7 . 7 7 Very poor water 4 Bore we l l 4 6 . 1 7 Good water 5 D u g w e l l 7 2 . 5 5 Poor water 6 D u g w e l l 9 5 . 0 6 Very poor water 7 D u g w e l l 8 8 . 1 9 Very poor water 8 Bore we l l 4 4 . 3 2 Good water 0 50 100 150 200 250 1 2 3 4 5 6 7 8 C h lo ri d e /S u lp h at e /B ic ar b o n at e (M g/ l) Well number Cl SO4 CHO3 file:///C:/user/Downloads/azojete143/www.azojete.com.ng file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Sodangi et al: Evaluation of Groundwater Quality for Drinking Purposes using Water Quality Index, in Keffi Central Town of Nasarawa State. AZOJETE, 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 193 Table 5: Range of water quality index for drinking purpose (Mishra and Patel, 2001) S / n R a n g e Type of water 1 0 - 2 5 E x c e l l e n t 2 2 6 - 5 0 Good 3 5 1 - 7 5 Poor 4 7 6 - 1 0 0 Very poor 5 > 1 0 0 Unsuitable for drinking purpose Table 6: Statistical summary of chemical data of groundwater in keffi central town (2019) Chemical Parameter U n i t R a n g e Mean NIS(2015) HPL p H ¯ 5 . 7 - 7 . 1 6 . 3 6.5-8.5 E C µ S / c m 2 5 6 - 1 5 9 1 812.25 1000 Magnesium m g / l 2 . 6 - 2 9 13.95 2 0 Calcium m g / l 3 . 7 - 3 4 1 5 . 8 2 0 0 Sodium m g / l s 2 2 - 5 6 3 7 . 8 2 0 0 Chloride m g / l 8 . 4 - 6 3 25.59 2 5 0 Bicarbonate m g / l 5 4 . 3 - 2 1 9 . 6 118.46 1 0 0 Sulphate m g / l 0 . 1 - 3 2 . 4 1 2 . 4 1 0 0 TDS m g / l 9 5 . 2 - 3 0 2 . 9 4 178.57 5 0 0 T H M g / l 2 3 . 8 - 2 0 4 . 2 3 102.21 1 5 0 4. Conclusion In the present study, WQI has been computed to evaluate the suitability of groundwater for drinking purpose in Keffi central town. After analysis of various physiochemical parameters, the results obtained for the WQI were found to be varied from 44.32 to 61.60 for bore holes and 72.55 to 97.77 for dug wells respectively. This indicated that location 2,4 and 8 of the water samples are safe for drinking purposed. While borehole location 1, and dug well 3,5, 6 and 7 were not suitable for human consumption. It can be said from this finding that groundwater in the study area were found to be good, poor and very poor quality respectively. Therefore, Public awareness campaign on the dangers of ground water contamination is encouraged. The high values of the water quality index at the study area was due to the higher values of electric conductivities, total hardness, Magnesium and bicarbonate as well as: anthropogenic activity, poor site sanitation and soak away. From water quality index values, it is recommended that further improvement is required to treat the poor and very poor-quality wells (such as demineralization and water softening) for using as safe drinking purpose. In addition, bole holes should be provided for other communities within the study area. Moreover, there should be quality control standard for all the bore holes, so as to meet up with the Nigerian Industrial Standard (NIS). http://www.azojete.com.ng/ file:///C:/Users/Engr.%20Samuel/Documents/Engr%20Oyeniyi/azojete/AZOJETE%20ARCHIVE/UPLOAD/VOL%2019%20NO%202/AZOJETE%20VOL%2019%20NO%202/sodangiali2020@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June, 2023; Vol. 19(2):183-196. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: sodangiali2020@gmail.com 194 References Abdullahi, NK. and Iheankawa, A. 2013. 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