Drinking water quality parameters from groundwater source was assessed in Bhajani and Chuha VDCs in Kailali district. A total of 24 groundwater samples were assessed following standard procedures and the results were compared with the national standard. Most of the parameters such as colour, pH, turbidity, TDS, EC and total hardness were within the prescribed limit. Some heavy metals such as Al, Pb, Cd, Fe, As and Mn exceeded in some of the samples indicating possible risk to the community.
Keywords: Groundwater Quality; Permissible Limit; NDWQS; Heavy Metal Contamination
Groundwater is a significant water supply source contributing as much as 75% of overall drinking water supply in the world . It is a major source of drinking water in Nepal as well, particularly in the lowland regions of Terai [2, 3], since the highest proportion of the population in the country live in this region . Accordingly, majority (90%) of the people in the Terai region depends on dug wells and tube wells as their primary source of potable water . However, deterioration of ground water resources due to a variety of anthropogenic activities has become a growing concern in many parts of the world [6- 9] including Nepal [10,11].
A number of studies have been conducted on the ground water quality in Nepal; however they have been mostly conducted in Kathmandu Valley. These studies have dealt with physico-chemical analysis of water and bacterial contamination [10-14]; Arsenic contamination . These investigations have shown the groundwater in the valley contaminated with Ammonia, Nitrate, Iron as well as coliform [10,12,14].Studies in the Terai region have also focused mainly on Arsenic contamination [2,3,5,16,17]. The findings revealed that most of the samples contained arsenic concentration below 10 μg-1 however some of the samples did exceed this limit with concentration ranging from 10- 50μg-1 and ˃ 50μg-1 .The studies have further shown that Arsenic contamination in this region is of geogenic origin [5,18]. Similarly, most of the studies in the Terai of the Far- Western Development Region of Nepal have also focused on groundwater arsenic contamination. This has resulted in the lack of adequate data on the health parameters for groundwater quality for drinking purposes and since groundwater is the major source of drinking water in Kailali and with only few studies being conducted on other heavy metals which could also have as serious health implications as arsenic. Therefore, there is a need to address the gap on research on the other health parameters for groundwater quality.
Methods and Materials
The study was conducted in Bhajani and Chuha VDCs of Kailali district, which lies in the Terai region of Far Western Nepal (Figure 1). Bhajani and Chuha VDCs cover an area of 28.98 and 81 square km respectively. The area has sub- tropical, temperate and cool temperate type of climate with maximum and minimum temperature of 44°C and 23.5°C respectively.
Figure 1: Kailali district showing Bhajani and Chuha VDCs
For the quantitative determination of different physico-chemical parameters, 12 water samples from each VDC were collected randomly from 12 hand-pumps from Chuha; 9 water samples from hand pump, 2 from taps and one from reservoir from Bhajani. The source of the tap water and the reservoir was also groundwater. Thus a total of 24 water samples were collected in March 2014. The field analysis was carried out on some selected physico- chemical parameters that required immediate analysis, and for the presence-absence test for bacteriological contamination. The physico-chemical parameters that were measured in the field were pH using a calibrated pH meter (Eco Sense pH.10 A), electrical conductivity(EC) and Total Dissloved SolidsTDS (Wagtech conductivity/ TDS meter). All these tests were performed on the spot.
A presence-absence test (P/A test kit developed by Environment and Public Health Organization ENPHO, Nepal) was performed for the detection of faecal coliform in the water samples. Water samples were filled up to the mark prescribed in the test bottles and incubated at temperatures between 2245⁰C for a period of 48 hours for subsequent colour change as indicated on the manual.
Laboratory Analysis of the Water Samples
For the laboratory analysis, different water quality chemical parameters were chosen as prescribed by Nepal Drinking Water Quality Standard (NDWQS) . For the cations, the water samples were collected in pre-acidified 125 ml plastic containers. Concentrated Hydrochloric acid was used as a preservative for Arsenic (As), while concentrated Nitric acid was used in case of other cations viz. Calcium (Ca), Iron (Fe), Manganese (Mn), Aluminum (Al), Copper (Cu), Zinc (Zn), Lead (Pb), Chromium (Cr), and Ammonium (NH4+). For anions such as Sulfate (SO4-), Nitrate (NO3-), Chloride (Cl-), Fluoride (F-); water samples were collected in non-acidified 500 ml plastic containers. The samples were refrigerated immediately in an ice box and brought to Aquatic Ecology Centre, Kathmandu University for laboratory analysis. Analysis of samples was performed following standard procedures . The obtained results were compared with the NDWQS .
To test whether the different parameters varied between the two VDCs and to account for the skewed distribution of the data, non-parametric statistical analysis Mann Whitney Rank Sum test was carried out. Pearson’s correlation was applied to determine the relationship among the different water quality parameters. All the statistical tests were performed at p˂ 0.05 level of probability. Statistical software Sigma Plot Version 12 was used for the statistical analyses.
Results and Discussion
Different parameters such as colour, pH, turbidity, TDS, EC and total hardness in all the water samples were within the permissible limits of the National Standard (Table 1 and Table 2) . The taste and odour of all the samples were unobjectionable. In Bhajani, the turbidity values in the samples were variable and ranged from <1 to 4 Nephelometric Turbidity Unit (NTU), with an average of 2.81± 0.90 NTU, whereas in Chuha, the turbidity values ranged greatly from 2.8 to 78 NTU, with
an average of 22.13± 27.5 NTU. Mann Whitney Rank Sum Test revealed that turbidity and colour showed significant variation between the water samples collected from the two VDCs. Turbidity in samples from Chuha VDC was significantly higher than those from Bhajani (p ˂ 0.001).A number of factors are responsible for turbidity in surface and ground waters such as inert clay or chalk particles, precipitation of non-soluble reduced iron and other oxides . High turbidity may indicate the presence of disease causing organisms, as it can interfere with disinfection and provide a medium for microbial growth . Thus, turbid water is considered unfit for domestic and many other purposes . The colour showed significant variation between the water samples (p ˂ 0.05).All the water samples collected from Bhajani showed ˂2 TCU (Total Colour Unit) whereas in samples collected from Chuha, it ranged from ˂2 TCU to ˂10 TCU. A number of factors such as humic acids, fulvic acids, metallic ions such as iron and manganese, suspended matter, phytoplankton, weeds and industrial wastes impart colour to natural water bodies .
In Bhajani, the mean pH value was 6.96±0.35. The highest pH was 7.6 (BR6) and the lowest pH was 6.56 (BP4).In Chuha, the average pH was 6.71 ±0.47 ranging from 5.9 to 7.05. The lowest value was observed in two stations (CR2 and CP1), while the highest value was observed in one station (CR6). The mean value was similar to the values obtained in the groundwater of Terai basin  and in the groundwater of Kathmandu valley . Presence of organic and inorganic solutes together with the reaction of carbon dioxide brings about changes in water pH . High concentrations of bicarbonate (HCO3-) and low concentrations of sulfate (SO42-) and nitrate (NO3-) in the ground waters of the Terai region are responsible for neutral to alkaline pH  .
The TDS in the samples ranged from 242 mgL-1to 671 mgL-1, with an average value of 418.92±136.20 mgL-1 in Bhajani whereas in Chuha, the TDS in the samples ranged from 294 mgL-1to 350 mgL-1, with an average of 316.58±14.32 mgL-1. The taste of water with a TDS level of less than about 600 mgL-1 is generally considered to be good and drinking-water becomes significantly and increasingly unpalatable at TDS levels greater than about 1000 mgL-1.
Table 1: Water Quality result (Bhajani)
The presence of high levels of TDS may also be objectionable to consumers  and higher levels of TDS in water can cause significant health impacts to people with hypertension and diabetes [25,26]. Furthermore, TDS concentration exceeding 2000 mgL-1 is known to produce a laxative effect [27,28].
In Bhajani, the EC ranged from 485μScm-1 to 1340 μScm-1, with an average of 838.25±272.57μScm-1, whereas in Chuha, the EC ranged from 582 μScm-1 to 706 μScm-1, with an average of 638.92±35.61 μScm-1 indicating high conductivity values. Although EC does not indicate the presence of an element in particular , it is however a measure of the total amount of dissolved minerals and ions in water [26,30] and thus indicates the presence of ions such as Sodium, Potassium, Chloride or Sulfate . Correlation between EC and TDS showed a significant positive correlation (r2= 0.999 and r2= 0.718 in Bhajani and Chuha respectively) (Figure 2) between the two variables, which can be ascribed to the fact that EC is directly affected by the total number of the dissolved ions in the solution . Similar range of conductivity has also been reported in other parts of the Terai  and groundwater of Kathmandu valley . High conductivity value in ground waters is attributed to the high salinity and mineral contents and dissolved solids occurring naturally in the groundwater.
In Bhajani, the average total hardness was 280.17±91.32 mgL-1. The maximum value of hardness was 454 mgL-1 (BR2H) and lowest hardness value was 194 mgL-1 (BP2) whereas in samples from Chuha, the total hardness ranged from 292 mgL-1 to 364 mgL-1 with a mean of 323±18.48 mgL-1. Hardness in water is known to be caused by a variety of dissolved polyvalent metallic ions, predominantly Calcium and Magnesium, although other cations such as Aluminium, Barium, Iron,
Figure 2. Correlation between EC and TDS Bhajani (a) and Chuha (b).
Table 2: Water quality results (Chuha)
Table 3: Descriptive statistics of the water quality variables.
Table 4: Pearson’s correlation coefficient for the parameters studied
Manganese, Strontium and Zinc also contribute to total hardness . Hardness in the water samples can be attributed to the Calcium concentration in the samples. Pearson correlation showed that Calcium showed a highly significant positive correlation with hardness, TDS and EC (p˂0.01) (Table4).
The concentrations of the anions in all the samples were within the permissible limit prescribed by the NDWQS . Nitrate was present below the detection limit in 20 samples (Table 1and Table 2). One sample in particular (CR2), had a relatively high Sulfate concentration (33.69 mgL-1). Similarly, a relatively higher concentration of Chloride (30 mgL-1) was seen in one sample (CR3) which could be attributed to contamination of the groundwater with waste water.
The concentrations of different cations in the water samples were in the order of Ca2+>Al3+> Fe3+ >Mn2+>Zn2+> Pb2+>As3+>- Cu2+> Cd2+>Cr3+in Bhajani whereas in Chuha it was in the order of Ca2+>Al3+> Fe3+ >Mn2+>Zn2+> As3+>Cu2+> Pb2+>Cd2+>Cr3+.In all the samples, concentrations of Ca, Zn and Cr were within the permissible limit of the NDWQS . Besides these, As, Cr and Pb concentrations in samples from Bhajani and Cu and Cr concentrations in samples from Chuha were within the permissible limit. The concentration of Aluminum exceeded the national standard in 22 samples ( BP2, BP3, BP4, BP5, BP6, BR1T, BR2H, BR3H, BR4T, BR5H and BR6 from Bhajani CR1, CR2, CR3 CR4, CR5,CR6, CP1,CP2, CP4 ,CP5 andCP6 from Chuha); Iron in eighteen samples (BP2, BP4, BP5, BP6, BR3H, BR5H and BR6 from Bhajani and CR1, CR2, CR3, CR4, CR5, CR6, CP1, CP2, CP3, CP4 and CP6 from Chuha); Manganese in nine samples (BP1, BP2, BP3, BP4, BP5, BP6, and BR5Hfrom BhajaniCP3 and CP6 from Chuha); Lead in four samples (BP4 from Bhajani and CR1 and CR3 from Chuha); Arsenic in two samples(BR4T from Bhajani and CP5 from Chuha) and Cadmium in one sample (BR2H) exceeded the prescribed limit.
Ground water chemistry is basically governed by bedrock geology [9,32,33]; seasons  and in the coastal areas, salt water intrusions is also an important contributing factor [34,35]. However, a number of anthropogenic activities such as urbanization [36,37] use of fossil fuel  also can bring about an increase in the concentration of different ions and heavy metals in groundwater. The concentration of Calcium, though within the permissible limit, was high.Calcium is often the most dominant ion in natural freshwaters . High concentration of Aluminum has been attributed to extremely low pH in the ground waters and a concentration of 290 mg-L has been observed at a pH of 1.9 in ground waters of Perth, Australia . Similarly, the concentrations of Iron and Manganese were observed to exceed the NDWQS  permissible limits in some samples indicating microbial activity in releasing these metals in the ground water [32,39,40]. Elevated levels of Iron have also been reported in the groundwater of Nawalparasi . The concentration of Arsenic was lesser than the average Arsenic level in the tube wells of Kailali district previously reported at 0.062 mgL-1 . Shown to have geogenic origin  in the Terai region, Kailali has been categorized as one of the six districts worst hit by Arsenic contamination in Nepal with Kota Tulsipur VDC being identified with the highest concentration of this heavy metal. However, in this study only two samples were known to contain the concentration exceeding the permissible limit indicating spatial variation in the concentration. A recent study in the district of Nawalparasi in Nepal has also reported spatial variation in the concentration of this element .
Presence of faecal coliform was detected in 6 samples (BR3, BR5 and BP3 from Bhajani and CP3, CP5 and CP6 from Chuha) indicating faecal contamination of the water in wells. The possible causes of faecal contamination of the groundwater are improper sewage disposal practices like pit latrine, septic tank and soakage pit system [41,42]. Faecal contamination can also be attributed to the level of nutrients like nitrite, total organic carbon and phosphate-phosphorus  available in the water. As per Nepal Drinking Water Quality Standard (NDWQS)  and WHO (2011) guidelines, water is considered acceptable if the total coliform count is zero in 95 percent of the samples. Faecal contamination of water bodies is an indication of presence of pathogenic organisms .
The major source of drinking water in the investigated sites was found to be groundwater, which was tapped from the aquifer using hand- pumps dug at household level and pipe water supply from deep boring reservoir. The average depth of the tube well in Bhajani was 41.29±18.01 feet in and 48.917 ± 11.02 feet in Chuha. The locals were found to consume the groundwater directly without any treatment. However, they are aware of the health implications of Arsenic contamination in water. When asked whether they were aware of waterborne diseases, few respondents were indeed aware of such diseases. However, they have not adopted any measures to address this issue. The community perceives that there is no scarcity of water in their VDC. However, this could be because they have been using the hand- pumps for only a little over a decade.
This study was carried out to assess the ground water quality of Bhajani and Chuha VDCs in Kailali district, in Western Nepal. Most of the water quality parameters were within the permissible limit of the national standard; however, some parameters have exceeded the permissible limit. The concentration of Aluminum was consistently high in twenty two samples far exceeding the permissible limit of the national standard. Similarly concentration of Lead also exceeded the permissible limit in few samples. These findings imply and are of concern as these heavy metals are known to have human health consequences upon long time consumption. Considering the fact that groundwater is the major source of potable water in the region and given the toxicity of the heavy metals the study indicates a possible risk to the community. A more robust assessment spanning larger areas and different seasons is recommended.
This study was funded by Voluntary Service Overseas (VSO), Nepal. The authors would like to thank Sumitra Poudel, Prassana Shrestha, and the Aasman Kailali volunteers for helping out in the field and the community of Bhajani and Chuha for giving their time and allowing us to take water samples; staff from Aquatic Ecology Centre, Kathmandu University for analyzing the samples; Prof. Subodh Sharma and Prof. Roshan Man Bajracharya for their advice and suggestions. Finally, we would like to acknowledge the anonymous reviewer for constructive suggestions and comments.