Assessment of Water Quality for Drinking Purpose in District Pauri of Uttarakhand, India

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These sources are being used for drinking water supply in the district through water supply department of the state (Uttarakhand Jal Sansthan) to cater the mass population of the district. Water samples were collected from each site during pre-monsoon (April-May) and post-monsoon (October-November) seasons of the year 2011. Grab sampling was preferred for sample collection.

Water samples were collected in high-density polyethylene ‘Tarson’ brand bottles after 2-3 times rinsing with the sample. For trace metal analysis, water samples were collected in acid-leached polyethylene bottles and preserved by adding ultra pure nitric acid (5 ml/l) to minimize the adsorption and precipitation by reducing pH <2. While for bacteriological analysis, samples were taken in sterilized Tarson bottles covered with aluminum foils. pH and turbidity parameters were measured on site while for other parameters, water samples were brought to the laboratory at 4°C in sampling box. Sample preservation and physico-chemical analysis were performed as per standard methods of APHA ^[17]. Colorimetric analysis was performed by UV-VIS spectrophotometer of Merck, Germany (Model: Pharo300). Metal ion concentrations were determined using flame atomic absorption spectrometer (FAAS) of Varian (Australia; Model AA240) ^[18]. All the chemicals and reagents of analytical grade were purchased from Merck, India. Analytical grade water from Millipore water purification system (Make: Millipore, USA; Model: Elix and Synergy) was used for the preparation of all standards and solutions.

3. Results and Discussion

The detailed discussion of analysed physico-chemical characteristics of collected water samples from Pauri district is presented under the Table 2. These results are also compared with Bureau of Indian Standard IS 10500 ^[19] recommended for drinking purpose.

3.1. Turbidity and pH

The turbidity values fluctuated from 1.0 to 24 NTU and 7.8 to 9.8 NTU, respectively during pre- and post-monsoon seasons. Site no.1 (i.e. Srinagar) has higher turbidity value as 24 NTU than the permissible limit of 5 NTU during pre-monsoon season. The higher turbidity values in water sources of Pauri district has also been verified by the monitoring study of Govt. of India ^{[20, 21]}. The pH values ranged from 7.10 to 8.26 and from 7.38 to 7.87 during pre- and post-monsoon seasons, respectively. The pH values in all drinking water sources were found within the recommended limit of BIS as 6.5 to 8.5.

Table 2. Hydrochemical data of water samples of Pauri district

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3.2. Total Hardness and Alkalinity

The range of total hardness were found in between 41 to 152 mg/l and 21 to 69 mg/l, respectively during pre- and post-monsoon seasons for all the samples falling within the desirable limit of 200 mg/l of BIS. Alkalinity values in the analyzed water samples were obtained from 27 to 114 mg/l and 18 to 52 mg/l, respectively during pre- and post-monsoon seasons. The results show that all concentrations were found to be within the desirable limit of 200 mg/l.

3.3. Total Dissolved Solids (TDS)

TDS values fluctuated from 68 to 236 mg/l and 49 to 116 mg/l, respectively in pre- and post-monsoon seasons. TDS content in all the samples were well within the desirable range of 500 mg/l of BIS.

3.4. Calcium and Magnesium

The calcium contents in water samples ranged within 9.45 to 36 mg/l during pre-monsoon season and 4.45 to 15 mg/l during post-monsoon season. The magnesium content varied from 4.28 to 15 mg/l and 1.80 to 7.39 mg/l, respectively for pre- and post-monsoon seasons. The results indicate that no site exceeded the concentration of calcium and magnesium from their desirable limits as per BIS 10500 of 75 and 30 mg/l, respectively.

3.5. Sodium and Potassium

The values of sodium were quite lower in analysed water samples, which fluctuated from 2.86 to 3.87 mg/l and 2.62 to 6.73 mg/l, respectively in pre- and post-monsoon seasons. The sodium values in all samples were well within the prescribed limit of WHO as 20 mg/l. The potassium ion concentration oscillated within 0.88 to 1.72 mg/l during pre-monsoon season and 0.39 to 2.43 mg/l during post-monsoon season. BIS and WHO have not prescribed any limit for potassium ions in drinking water but it is useful for total ionic balance as well as important nutrient for human body. The seasonal variations for potassium ion were negligible during study.

3.6. Chloride and Fluoride

The chloride concentrations were found from 12 to 18 mg/l and 8 to 12 mg/l in analysed samples during pre- and post-monsoon seasons. Fluoride concentration ranged from 0.34 to 0.43 and 0.05 to 0.23 mg/l, respectively during pre- and post-monsoon seasons. No sample exceeded the desirable limit of 250 mg/l for chloride and 1.0 mg/l for fluoride.

3.7. Nitrate and Sulphate

The values of nitrate were confined between 0.4 to 3.4 and 0.6 to 1.4 mg/l, respectively during pre- and post-monsoon seasons. Nitrate concentration in water samples of all sites were well within the prescribed limit of 45 mg/l. The sulphate concentration fluctuated in a limited range of ND (not detected) to 18 mg/l in pre-monsoon season and ND to 12 mg/l in post-monsoon season. The collected concentrations of sulphate were much lower than the desirable limit of sulphate as 200 mg/l.

3.8. Iron

In the drinking water samples, the iron content was from 0.104 to 0.364 mg/l and 0.073 to 1.777 mg/l, respectively during pre- and post-monsoon seasons. The maximum concentrations of iron as 0.364 mg/l and 1.777 mg/l were recorded at Srinagar (Alaknanda River) sampling site no.1 during both pre- and post-monsoon seasons. These concentrations of iron were higher than the permissible limit of 0.3 mg/l, which is further confirmed by another study ^[21].

3.9. Bacteriological (Total Coliform and Fecal Coliform) Analysis

In the bacteriological assessment of water sources of study area, total coliform were recorded from absent to 160 colonies/100ml during pre-monsoon season. While in post-monsoon season, these organisms were recorded as 9 colonies/100ml at Srinagar (Alaknanda River) sampling location. Fecal coliform counts were found as 75 colonies/100ml only at Srinagar sampling site during pre-monsoon season, while in post-monsoon season, all sites were free from any fecal contamination. In the study, higher total and fecal coliform contaminations were noted only at Srinagar sampling site (Site no.1).

4. Water Quality Classification Using Piper Trilinear Diagram

Piper trilinear diagrams (Piper, 1944) were prepared to classify the water quality of selected sources of study area ^[22]. The diagram classified the hydrochemical facies in account of prominent ions contributed the water quality. These diagrams graphically represent the chemical equilibrium between cations (Ca²⁺, Mg²⁺, Na⁺ and K⁺) and anions (Cl^-, SO₄^2-, CO₃^2- and HCO₃^-) in water samples and also describe the presence of main contributor ions and chemical reactions taking place in the water. The diagram composed of two lower triangles of cations and, anions and middle quadrilateral. Quadrilateral or diamond shape indicates the combined distribution of both ions (cations and anions) and final water type of sources. Such diagrams may describe various hydrochemical processes like base cation exchange, cement pollution, mixing of natural waters, sulfate reduction, saline water (end-product water) and other related hydrochemical problems.

In present study, water quality of selected sites during pre- and post-monsoon seasons has been characterized using Piper diagrams (Figure 1). These diagrams represent that water quality of all selected sources is predominantly influenced by Ca⁺², Mg⁺² and HCO₃^-ions i.e. Ca-Mg-HCO₃hydrochemical faciesduring both pre- and post-monsoon seasons. These plots represent the equal dominance of alkaline earth metals and weak acid and thus water quality shows the nature of carbonate hardness.

Figure 1. Piper diagram showing water quality classification of study area

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5. Suitability of Water for Drinking Purpose Using Water Quality Index

Weight Arithmetic Water Quality Index Method was employed in determining the water Quality Index for assessing the suitability of water sources for drinking purpose. Such WQI has been extensively used for surface and groundwater quality assessment, mainly in different regions of India and also outside ^{[9, 23, 24, 25]}. The index classifies the water quality based on the purity of sample by using the most commonly measured water quality parameters. This index was computed by using the following steps:

In the first step, water quality parameters including TDS, HCO₃, Cl, SO₄, NO₃, F, Ca, Mg, Na and K were selected to summarize the water quality, which indicate the considerable impact in the regions.

In the second step, quality rating or subindex (q_i) is computed for each of the parameter by using the given expression:

Where, V_actual is the estimated value of i^th parameter in the analysed water sample; V_ideal is the ideal value of this parameter in pure water. The ideal value is zero for all parameters except pH =7.0 and V_standard is the recommended standard value of i^th parameter given in Table 2.

In the third step, the unit weight (W_i) for each water quality parameter was determined by using the following formula:

Where, S_i is standard value of i^th parameter recommended by BIS; K is the proportionality constant which is calculated by using the following equation:

In the final step, the overall WQI is calculated by using following formula:

The water quality ratings on the basis of index value for this WQI are summarized in Table 3.

Table 3. Water quality rating and index values

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Table 4. WQI values and relative description of water samples

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