Calculation Of Water Quality Index Research Articles

An appraisal of the drinking water quality of groundwater sources in Ogbomoso, Oyo state, Nigeria

A total of one hundred and twenty-two water samples were obtained from hand-dug wells and boreholes in Ogbomoso metropolis, Oyo State, Nigeria. Physico-chemical, most probable number technique, direct culture methods, and water quality index were used to assess the drinking water quality in this region. Some of the physicochemical parameters were within the acceptable limits, with the exemption of conductivity (940 μscm−1), total dissolved solids (1120 mgL−1) total hardness (404 mg CaCO3L−1), and Cl− ion (220 mg/L). Escherichia coli, Klebsiella sp, Staphylococcus aureus, Shigella dysenteriae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella sp, and Serratia sp are some of the isolates obtained from the water samples. Total coliform count in the well water samples was higher than those from boreholes, with E. coli having up to 180 and 45 CFU/mL for well and borehole water samples respectively. The calculated water quality index indicated poor drinking water quality. Some of the isolates were resistant to nothing less than three antibiotics and a maximum of ten antibiotics. All approaches used for assessing the water samples emphasize the need for improvement in water quality to safeguard public health. Drinking water from hand-dug wells and boreholes in this region requires treatment by chlorination, filtration, and boiling before consumption. Government bodies saddled with environmental and health responsibilities in the region should provide a potable water supply.

Assessment of water quality index of different water bodies of Pusa, Bihar

Water quality of river (Budhi Dandak), ponds, hand pump and deep tube wells of Pusa village were evaluated by Water Quality Index (WQI) technique.Water quality is directly related to the physical, chemical and biological property of water. These properties of water were affected by the human activities such as disposal of pollutant in the water bodies that changes the standard quantity parameters of water. The objective of an index is to turn complex water quality data into information that is understandable and useable by the public. Seven most important parameters such as pH, total dissolved solids (TDS), sodium (Na), Chloride (Cl-), calcium (Ca), magnesium (Mg), and electrical conductivity (EC) were taken for the calculation of WQI. WQI obtained from different water sources such as river, pond, hand pump & deep tube well were found to be 30.60, 33.19, 44.41 and 41.05 respectively. The different values of various parameters were analyzed and found that pH was in the range of 7.2-7, Cl- ions concentration ranged from 42.55-99.29 (mg/l), TDS concentration 186-494 (mg/L), and Ca + Mg concentration 130-257 (mg/l), Na 56-118 (mg/l) and EC concentration 387-882 (µS/cm) respectively. We concluded that pH, Cl-, TDS and Ca + Mg were found in permissible limit but EC and Na+ were excess from permissible limit.Water quality index level shows that the water of water bodies in Pusa were not fit for direct use or drinking purpose, but good for domestic, irrigation, and industrial purposes.

Assessing surface water quality under anthropological influences in the Caí River, Rio Grande Do Sul, Brazil

ABSTRACT The Caí River plays a fundamental role in the hydrologic systems of Rio Grande do Sul (RS), the southernmost state in Brazil, and significantly contributes to maintaining the environmental quality of the region through which it flows. This study aims to examine the surface water quality of the Caí River basin in its middle section, based on a water quality index calculation, and to apply a qualitative protocol to the environmental conditions of the water resource and its environment. Nine physicochemical and microbiological parameters were monitored at five collection points located upstream, downstream, and in the central area of Feliz City for a year. The results showed water quality index (WQI) values between 51 and 78 during the evaluation period. Of the samples collected and analyzed, 36% were on the ‘good’ quality scale and 64% indicated ‘reasonable’ water quality. The results showed that water quality was considered good in the studied area. However, some parameters, such as biochemical oxygen demand (BOD) and total phosphorus, did not meet standards recommended by current legislation.

Assessment of groundwater quality using water quality index (WQI): A case study of a hard rock terrain in Sri Lanka

Chronic Kidney Disease of uncertain etiology (CKDu) is a widespread health issue in rural dry zone regions in Sri Lanka. Monaragala region, located in eastern Sri Lanka is one of the hardest hit areas with CKDu. In order to investigate the possible relationship between the incidence of CKDu and drinking water quality, 99 groundwater samples from deep boreholes and shallow wells in hard rock aquifers in the Monaragala region, were collected and analysed for major cations and anions, and some selected trace element contents. The results revealed that over 65% of the groundwater samples from Monaragala area were alkaline. The anions in groundwater varied as HCO3− > Cl− > SO42− > F− while cations varied in the order of Na > Ca > Mg > K. The Majority of the samples (75%) belong to the Ca2+-Mg2+- HCO3− type. Among the studied parameters, electrical conductivity, chloride, sulphate, hardness, fluoride exceeded the WHO recommended values for drinking water in most cases. For instance, 76% of wells in the study area showed fluoride levels higher than the recommended levels (0.5 mg/L) for Sri Lanka. The higher ion contents in groundwater were mainly due to dissolution of aquifer minerals and a higher rate of evaporation. The calculation of Water Quality Index (WQI) indicated that over 50% of groundwater samples of the study area are poor in quality. The higher values of WQI also overlap with high prevalence areas of CKDu. This work revealed that groundwater quality has a direct effect on the etiology of CKDu in the region.

Improving prediction of water quality indices using novel hybrid machine-learning algorithms

River water quality assessment is one of the most important tasks to enhance water resources management plans. A water quality index (WQI) considers several water quality variables simultaneously. Traditionally WQI calculations consume time and are often fraught with errors during derivations of sub-indices. In this study, 4 standalone (random forest (RF), M5P, random tree (RT), and reduced error pruning tree (REPT)) and 12 hybrid data-mining algorithms (combinations of standalones with bagging (BA), CV parameter selection (CVPS) and randomizable filtered classification (RFC)) were used to create Iran WQI (IRWQIsc) predictions. Six years (2012 to 2018) of monthly data from two water quality monitoring stations within the Talar catchment were compiled. Using Pearson correlation coefficients, 10 different input combinations were constructed. The data were divided into two groups (ratio 70:30) for model building (training dataset) and model validation (testing dataset) using a 10-fold cross-validation technique. The models were evaluated using several statistical and visual evaluation metrics. Result show that fecal coliform (FC) and total solids (TS) had the greatest and least effect on the prediction of IRWQIsc. The best input combinations varied among the algorithms; generally variables with very low correlations displayed weaker performance. Hybrid algorithms improved the prediction power of several of the standalone models, but not all. Hybrid BA-RT outperformed the other models (R2 = 0.941, RMSE = 2.71, MAE = 1.87, NSE = 0.941, PBIAS = 0.500). PBIAS indicated that all algorithms, with the exceptions of RT, BA-RT and CVPS-REPT, overestimated WQI values.

Assessment of potability of spring water and its health implication in a hilly village of Uttarakhand, India

Water quality assessment of different sources of water in a village was carried out by taking selected significant parameters, namely temperature, pH, conductivity, total dissolved solids (TDS), dissolved oxygen (DO), free carbon dioxide (free CO2), alkalinity, hardness, calcium, phosphate, nitrate, chloride and coliform count. All these parameters were analyzed as per the standard protocol of American Public Health Association. Further, seven parameters (pH, TDS, alkalinity, hardness, calcium, nitrates and chloride) were used to calculate water quality index for assessing overall drinking water status of sampling sites. A survey of health status of population of the village was also conducted with the help of questionnaire and interview method to draw the relationship of water quality and health. All selected physicochemical parameters were found under prescribed limits as stated by Indian Standard 10500 and Central Pollution Control Board guidelines. The values for most probable number count were found above the permissible limit of drinking water indicating contamination of coliform at all sites. Further, water quality index for SN1, SN2, SN3, SN4 and SN5 was 17.61, 30.11, 69.73, 25.60 and 47.15, respectively. As per the water quality index, the water samples of natural springs which were away from village were classified under ‘excellent’ category as compared to supply water samples. The result of survey recorded 38% population suffered from dysentery, 23% from diarrhea and 17% from typhoid. The report of the survey and the presence of coliform suggest that drinking water contamination is leading to waterborne diseases like cholera, dysentery and typhoid. It is also suggested that water quality of all sites except SN3 was suitable for drinking purpose, but disinfection of coliform before use is warranted.

Impact of rapid urbanization on the surface water's quality: a long-term environmental and physicochemical investigation of Tajan river, Iran (2007-2017).

Sustainable development of our society requires protection and monitoring of aquatic environments, as they are the pivotal water resources and niche for wildlife animals. In this research, physicochemical parameters of Tajan river's water were determined and compared with standards to assess the rural and human activity impact on water quality. First, monitoring and analyzing the water quality of the river were performed for 11years (from 2007 to 2017). Based on calculated water quality index (WQI) values, Tajan river's water quality falls into four categories: good water with WQI less than 30 at upstream and middle of the river, poor water, and very poor to even unsuitable water (WQI ranges from 86 to 134) at the more urbanized locations. The high values of WQI are due to an elevated concentration of sulfate, nitrate, total dissolved solids (TDS), and chloride substances. The source of contaminations, according to the geochemistry of the area and having more than 90% growth rate in the population near to the most polluted location, is probably anthropogenic activities. Then, the long-term experimental data set has been utilized for developing a statistical model to be used for prediction of water quality with a few chemical analyses, generating a rapid and low-cost water quality evaluation for this river. The model was developed based on the stepwise multiple linear regression (MLR) approach and confirmed the experimental observation data of the most defective elements on WQI were respectively SO4, NO3, TDS, Cl, pH, and EC. This study presents a long-term evaluation of changes in surface water quality at a region with a recent rapid urban and civil development providing a suitable case to understand better human-water relations.

Water Quality of the Trstionica River (Bosnia and Herzegovina)

The present study was conducted to investigate the water quality of the Trstionica River, Bosnia and Herzegovina. The physicochemical properties (temperature, pH, conductivity, total solids after evaporation at 105 °C), content of metals (calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb) and zinc (Zn)), and anions (chloride (Cl–), and phosphate (PO43–)) were determined in water samples collected at seven locations during two sampling periods: unstable weather conditions (precipitation), and stable weather conditions (without precipitation). There was a significant difference in the content of individual parameters in the river water depending on the sampling time. For determination of metals concentrations, which were below the limit of detection, a preconcentration method using an ion-exchange resin was applied. The metals concentrations during the rainy day were in the order Ca > Mg > Na > Fe > Cu > Zn > Pb > Mn with mean values of 343, 6.03, 1.94, 0.18, 0.20, 0.03, 0.02, 0.01 mg dm–3, respectively, and during stable weather conditions: Ca > Mg > Na > Cu > Fe > Mn > Zn with mean values of 288, 7.62, 2.38, 0.11, 0.10, 0.01, 0.01 mg dm–3, respectively. Cd, Cr, and Ni concentrations were below limit of detection in both cases. Obtained values were compared with World Health Organization (WHO) regulations. The results showed that the Trstionica River in the investigated part of the stream meets most of the parameters required by the regulations. The correlation between analysed parameters was assessed, as well. Based on the calculated water quality index values, the water of Trstionica River falls into the category of excellent water.

Evaluation of Groundwater Quality for Drinking Purpose using Different Water Quality Indices in Parts of Gautam Budh Nagar District, India

Water Quality Index (WQI) is a mathematical value for quality of water, which includes the concentration of a number of constituents present in it. Chemical and biological measures of water quality are used to represent water quality index. Measured value of the selected parameters, ideal concentration of that parameter in pure water and standard value given by different quality control organizations are used to determine this number. In the present study, three indexing methods; Weighted Arithmetic Water Quality Index (WAWQI), Groundwater Quality Index (GWQI) and Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) were used to calculate water quality index of groundwater. A hydrochemical analysis of 22 groundwater samples was conducted to evaluate the quality of groundwater for drinking purpose. Ten hydrochemical parameters were selected for computing WQIs of groundwater samples and BIS standards were used for standardization. Analytical results show that 100 % of samples have magnesium and total hardness above the acceptable limit of BIS (10500, 2012). The mean concentration of nitrate was found 196.96 ± 9.3.18 mg/L. Spatial distribution of various parameters shows that south-east part of study area has contaminated groundwater. The results of water quality index shows that drinking water quality of 82 % (WAWQI), 95 % (GWQI) and 77 % (CCME WQI) of groundwater samples were poor to unsuitable type. Water quality index map also reveals that groundwater of village Badhpura, Dhoom Manikpur, Dairy Maccha, Khera Dharampura, Bisrakh road, Duryai and Dujana of district Gautam Budh Nagar of India, was not fit for human consumption.

Assessment of Water Quality Evolution in the Pearl River Estuary (South Guangzhou) from 2008 to 2017

To control the water pollution in the Pearl River Estuary (PRE), a series of measures have been enacted in recent years. The efficacy of these measures on water quality improvement is, however, currently unknown. To evaluate the variation of water quality in response to the pollution control measures in the PRE during the last decade (2008–2017), our study conducted a long-term monitoring program of estuarine water in the representative city Guangzhou that targeted fecal coliform (F. Coli), biochemical oxygen demand (BOD5), chemical oxygen demand (CODCr), potassium permanganate index (CODMn), petroleum, total nitrogen (TN), ammonia nitrogen (NH3–N) and total phosphorus (TP). In the last decade, F. Coli, BOD5, CODCr and CODMn, petroleum and NH3–N have shown a significant reduction by 78.8%, 50.9%, 37.5%, 18.9%, 75.0% and 25.0%, respectively. In contrast, TN and TP remained stable. Water quality index calculations indicated that the water quality was elevated from the marginal–fair level to the good level, particularly after 2012. The biochemical pollutants and nutrients in the estuarine water most likely originated from the upper river due to the wastewater discharge, fecal pollution and agricultural input. The success of pollutant reduction could thus be attributed to industrial upgrading and relocation, as well as the improvement of the sewage treatment system in Guangzhou. However, efficient approaches to reduce TN pollution should be implemented in the future.

Application of Water Quality Index (WQI) and Regression Analysis of Groundwater in Budigumma Village, Anantapur District, Andhra Pradesh

The research work is aimed at assessing the subsurface or groundwater suitability for human use or consumption depends upon the calculated water quality index values, correlation coefficient and regression analysis. The water quality index (WQI) is main important tool to calculate the characteristics of drinking water quality in rural, urban and industrial area. Different parameters which is measured and determination of the water quality index for selecting parameters. Further to study the correlation and regression method in this research work. Totally fifteen groundwater samples were collected from the Budigumma Village Anantapur district in the state Andhra Pradesh in India. Nine water quality parameters has been considered for the computation of water quality index such as pH, total dissolved solid (TDS), total hardness (TH), calcium (Ca), magnesium (Mg), nitrates (NO3), chlorides (Cl ), sulphates (SO4), fluorides (F ). The World Health Organization (WHO) has been assessed to the suitability of groundwater for drinking purposes or other uses for public and determining of WQI. This WQI index values ranged from 97.78 to 108.37. The study shows that 87% area comes under the poor category of drinking purposes and the remaining 13% comes under as good water for drinking purposes as per the WQI classification. The correlation and regression analysis gives as an outstanding device for the calculation of different parameter values within realistic degree of precision. The subsistence of strong correlation or relationship between the total hardness and magnesium is determined. The analysis of selected parameters revealed that proper treatment before use or consumption and protected from more contamination.

Assessment of Bangladesh groundwater for drinking and irrigation using weighted overlay analysis

A weighted overlay analysis was conducted to calculate Water Quality Index (WQI) for drinking water using WHO and Bangladesh drinking water standards (BDWS) and for irrigation using irrigation water quality standards. The method used a normalized quality rating scale (qi) and relative weight (wi) for several water quality parameters to calculate WQI. This index-based suitability analysis was carried out to assess the overall water quality of groundwater in Bangladesh used for drinking and irrigation purposes.Drinking water quality index (DWQI) calculation was done based on As, Mn and hardness concentrations. For irrigation water quality index (IWQI) As, B, Cu, Fe, Li, Mn, Na, Zn and sodium adsorption ratio (SAR) were used. WQIs were calculated separately for the shallow tube wells (STW) (depth <150 m) and deep tube wells (DTW) (depth >150 m). The results revealed that 40.4% STWs and 88.7% DTWs have safe drinking water according to BDWS 57.6% STWs and 90% DTWs have safe drinking water based on WHO drinking water standards. Irrigation water quality index shows that 8.1% STWs and 23.1% DTWs have safe water quality. It has also been found that majority of deep tube wells have better water quality than shallow tube wells due to lower concentrations of contaminants in the deep tube wells compared to shallow tube wells. Some of the dissolved constituents in the groundwater of Bangladesh can potentially be great source of nutrients supplements required for plant growth. If the nutrients dissolved in groundwater replace the nutrients in fertilizers needed for plant growth, an average of US$12.61(BDT 1069) could be saved, which is approximately 19% of the total fertilizer cost.

Development of a Computer Application for the Calculation of Water Quality Index in Morocco

Water quality indices are generally a combination of biological, chemical, physical parameters to form a numerical composite index that can be easily interpreted and shared. Their efficiency and usefulness in managing and monitoring water quality have been appreciated by management organizations around the world. The integration of these tools into computer applications can be a major asset. The main purpose of this article is to present a computer application that integrates a water quality index developed in Morocco to facilitate its use and avoid manual errors related to users. The application entirely developed in python language under PyCharm (Integrated Development Environment) is executable on a computer and is presented as a GUI (Graphical User Interface) containing two sub-interfaces to calculate the surface and groundwater quality index according to the type of water analyzed.

EVALUATION OF SURFACE WATER QUALITY OF THE AREA OF INFLUENCE OF THE LANDFILL OF THE CITY OF MANAUS/AM

This work aimed to evaluate the quality of surface water around the Manaus Solid Waste Landfill (ARSM), in which it is located near important waterways in a growing urban expansion area. During the collection period, the parameters pH, T, fecal coliforms, OD, DBO5, nitrate, phosphate, turbidity and total solids were monitored, where these are the main parameters for performing water quality index calculations. The results analyzed indicate contamination in the streams near the perimeter of the Landfill, where the possible origins for non-conformities can be problems in draining the leached and waterproofing system of the landfill ponds. The recovery of the quality of these water resources is essential, since it is an area with flora and fauna that are heritage, not only of the residents who occupy their surroundings, but also the population of Manaus who in the past enjoyed bathing and fishing areas in the streams currently affected by the slurry produced in the landfill.

Application of Water Quality Index (WQI) For Ground Water Quality Interpretation

Water Quality Index (WQI) is a widely used technique in defining the quality of groundwater and finding whether it is advisable for human use. It is utmost necessary steps to understand the physical and chemical parameters defining the water quality for particular period and location using WQI calculation as it gives information in a single value. WQI has been calculated in twenty ground water samples collected from selected sampling stations at Madurai in the pre-monsoon, monsoon and post monsoon seasons. The water quality index values suggested that almost all the ground water samples were above 150, which indicated that they were unfit for drinking and one sample from Vilangudi had WQI less than 100 which indicated the water as poor category for drinking but could be used for irrigation purposes. The groundwater quality is also defined to be little better during post monsoon season in all the samples than during pre-monsoon and monsoon season.

Spring water quality assessment using water quality index in villages of Barwari Bala, Duhok, Kurdistan Region, Iraq

Periodic quality assessment of drinking water sources is necessary to guarantee the quality and security of water supply to people. Accordingly, this study assessed the drinking water quality of spring water of some villages located in Barwari Bala region of Duhok Governorate, Kurdistan region, Iraq, using the water quality index (WQI). To realize this objective, 120 spring water samples were collected from ten villages during the dry and wet seasons in 2018 and were analyzed for major physicochemical characteristics, including: calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl−), sulfate (SO42−), nitrate (NO3−), pH, total dissolved solids (TDS), turbidity, total hardness (TH) and total alkalinity (TA). The results for pH, turbidity, sodium, potassium, chloride, sulfate and nitrate showed that the water samples at all the sampled springs were suitable for drinking and within permissible limits based on given standards. However, TDS, TA, calcium and magnesium exceeded the permissible limits at some sites. It was also observed that, except for SO42−, at almost all the sites, the majority of parameters were significantly greater during the wet season compared to the dry season. With reference to all the parameters, the WQI values ranged from 10.76 to 18.13 during the dry season and from 17.10 to 20.45 during the wet season, indicating that all water samples are classified as having “excellent” water quality for drinking purposes. The calculation of WQI based on specific parameters, where values were close to or exceeded the maximum acceptable limits, showed that the water quality status of all water samples was “good” quality, except for sites S6 and S8, which were classified as “poor” quality and are not considered suitable for drinking purposes without treatment. Water from almost all the sampled spring sites can be considered as suitable for drinking purposes, although some parameters exceed permissible limits. Simple filtration treatment of the sampled spring water before use is desirable for ensuring good quality and security of the water supply to people of these areas.

Analysis of existing water information for the applicability of water quality indices in the fluvial-littoral area of turia and Jucar Rivers, valencia, Spain

For the first time, all the water quality information gathered by an European Union water district authority between 1990 and 2016 (the Spanish Jucar River Management Authority, Confederación Hidrográfica del Júcar, CHJ) was analysed and discussed. The main goal is to evaluate the applicability of this existing physicochemical information as potential data sources for continuous evaluation with Water Quality Indices (WQIs). Specifically, the spatial and temporal representativity of available data is assessed together with the applicability of WQIs both in time and space. A list of 42 existing WQIs with type and number of variables used was compiled after literature review. The study was carried out in the fluvial-littoral area of Turia and Jucar Rivers, Valencia, Spain, which was divided into six Landscape Functional Areas (LFAs), based on the outer continental perimeter zone, the irrigation areas of main channels crossing the flood plain, and the Albufera Lake.Input information consisted of a database, provided by the CHJ, of 67 sampling points with 401 physicochemical variables from 1990 to 2016, (about 283,023 records). This information was cross-analysed using descriptive statistics to evaluate the CHJ database information, the possibility of using WQIs, and the performance of target WQIs once their possible use both in time (27 years) and space (6 LFA) was established. Finally, a map representing the six LFAs was digitised, including the 67 sampling points and their water physicochemical characteristics.Results demonstrate that, out of 42 WQIs selected, seven can be used whenever all variables required are present. None of them can be calculated simultaneously at all stations and for all years. About 31% (21) of stations provided data that can be used in some years, and only 10% (27,430 values) of the database information is required for WQIs calculation. Indices that estimate repetitiveness (constant measure of water parameters over time) and consistency (coincidence of parameters measured at the 21 sampling points) show great disparity both in time and in parameters between sampling points. These results suggest that not only is it essential to obtain information on different compounds that may alter the water quality (to fulfil basin management authority policies), but also to establish a set of mandatory physicochemical parameters based on suitable application of some indices allowing temporary monitoring and comparison between them, in an accessible and repeatable manner.

Assessment of Guinea Savanna River system to evaluate water quality and water monitoring networks

The analysis of changes in water quality in a monitoring network system is important because the sources of pollution vary in time and space. This study utilized analysis of the water quality index calculation, hierarchical cluster analysis, and mapping. This was achieved by assessing the water quality parameters of the samples collected from Galma River in Zaria, Northwestern Nigeria in wet and dry seasons. The Analysis shows that sampling point number 15 located downstream of the river has the largest number of water quality index of 105.77 and 126.34, while sampling points 1 located upstream of the river has 62.71 and 78.09 in both wet and dry seasons respectively. This indicates that all the monitoring sites were polluted and the water could be utilized for industrial and irrigation specified due to the purposes only. Hierarchical cluster analysis and mapping revealed consistency and variations. For both networks, cluster 1 is located in the middle of the river watershed, while clusters 2, 3 and 4 show variations within the river watershed. 3 sampling points in wet season located at the upstream of the river were specified for Irrigation and Industrial uses, while the rest of the sampling points in both seasons were specified for irrigation purpose only. From this study, water quality index and multivariate techniques for environmental management can be employed in monitoring river resources, and research of this kind can help inadequate planning and management of the river system.

Physicochemical Assessment of Borehole Water in a Reclaimed Section of Nekede Mechanic Village, Imo State, Nigeria

The quality of borehole water in a reclaimed and about to be habited section of the Nekede mechanic village in Imo State, Nigeria, was determined. Five sampling points in this area were chosen for the study. Preliminary characterization of soil at these points using energy dispersive X-ray fluorescence method identified leachable heavy metals that can contaminate groundwater. The physical and chemical properties of the borehole water samples were analyzed using standard instrumental methods. The data obtained showed that the water samples were considerably acidic with pH ranging between 5.12 and 5.58. Lead, nickel and phosphate levels in the borehole water samples from all the sampling points were above tolerable limits and ranged between 0.22–0.42 mg/L, 1.03–1.12 mg/L and 0.14–0.34 mg/L respectively. The contamination factor model showed that all the borehole water samples were highly contaminated by lead and nickel, with values ranging between 38.00–42.00 and 14.71–16.00, respectively. The calculated Water Quality Index at all the sampling points gave values between 554.31 and 935.35 and indicated that the water samples were unsuitable for drinking. Constant consumption of borehole water from this area therefore would pose serious health risks to its intending and existing occupants.

Water Quality Index for Assessment of Potability of Groundwater Resource in Langata Sub County, Nairobi-Kenya

Water Quality Index (WQI) computation method based on quality parameters’ selection, assigning of weights, creation of sub-indices and calculation of the aggregated quality value has been used for many decades from the early 1960s to check on the pollution stati of watersheds. Today, due to rising water demand in the face of increased drought induced water shortage challenges and rampant pollution of the water sources, consumers augment their needs by using groundwater resources like in the case of Langata sub County in Nairobi city-Kenya. Little however, has been done to assess the overall potability of groundwater quality here. Accordingly, in the present study, a Water Quality Index (WQI) was developed by Weight Arithmetic Water Quality Index (WAWQI) method to fill that identified gap using a five categories’ grading scale, viz. excellent (A), very good (B), good (C), fairly good (D), suitable (E) and unsuitable (F). To realize this, chemical parameters’ concentration ranges were defined on the basis of the Kenyan Standards (KS) and International Standards of World Health Organization (WHO).Subsequently, a total of eight chemical parameters were selected based on their level of occurrence in borehole commissioning data obtained from Water Resource Management Authority’s database of the area viz; K+, Na+, Ca2+, Fe2+, F-, Cl-, SO4-2 and Ec (µS/cm). Out of a total of 137 boreholes, only 39 had complete eight chemical parameters. These 39 boreholes’ water quality assessment is taken in this study as a true representation of the entire area’s groundwater quality. The individual concentrations were spatially plotted using Surfer Software’s digital terrain model (DTM) which produced contoured maps in different chroma saturations including the overall aggregated concentration to facilitate scale ranking. The WQI for the study area is 53.18 in a scale of 1 to 100, with one being excellent. In this case, the groundwater quality was ranked as grade ‘C’. WQI calculation method is known to improve the understanding of water quality issues by integrating a suite of data into a single value which describes the status of water quality. WQI is very useful for the water management authorities because it facilitates their informing of the public on water quality in a simplified form.