6.3.1 Overall Groundwater Quality
The household groundwater sample collection in the study area commenced in November 2013 and continued till September 2014. The samples were collected, brought to the laboratory
sodium, potassium, calcium, alkalinity and hardness values were within WHO guidelines (Table 6.2) (WHO, 2008). It can be observed that iron was present in all the collected samples with least value of 0.02 mg/L in W12, whereas, concentration of iron exceeding WHO guidelines (WHO, 2008) was observed in all wards/zones. In case of fluoride, few samples found with no fluoride and instances of fluoride exceeding WHO guidelines (WHO, 2008) were observed in multiple wards except W1, W8, W9 and W14. Similarly, arsenic concentrations exceeded WHO guidelines (WHO, 2008) at many instances in wards W6, W7, W8, W9, W11, Z2, Z3 and Z4 (Table 6.2).
Hence, these three contaminants were considered as critical parameters. The ward/zone wise number of samples exceeding WHO guidelines (WHO, 2008) are shown in Table 6.3. The collected groundwater samples showed ample variation in concentrations of iron, fluoride and arsenic. Basically, iron and arsenic contamination is reported to be high in Bengal Delta Plain formed by the Ganga-Padma-Meghna-Brahmaputra river basin and the contamination is reported to spread across West Bengal, Bangladesh and extends to Indian states viz. Jharkhand, Bihar, Uttar Pradesh, Assam, and other Northeastern states of India along with the neighboring Nepal (Chakraborti et al., 2013; Chetia et al., 2011; Sengupta et al., 2003). Analogously, the overall groundwater quality in the study area was found to be in line with these reports and was unfit for drinking in most of the households.
6.3.2 Iron
As per WHO guidelines and BIS permissible limits, iron in drinking water should be below 0.3 mg/L (BIS 10500, 2012; WHO, 2008). Most of the samples were observed to have exceeded the WHO guideline/BIS permissible limits. Figure 6.1 shows sample locations exceeding (> 0.3 mg/L) and within (< 0.3 mg/L) the permissible limit. It was observed that none of the wards/zones recorded 100% compliance with WHO guidelines on iron content (Table 6.3). The highest percentage of samples exceeding the guideline/permissible limit was observed in W9, followed by W8 and W2. The overall percentage exceeding required guideline/permissible limit for iron was observed to be 52%. The results of present study were in line with literature that reported similar results on concentration of iron exceeding guideline/permissible limit in Greater Guwahati, reflecting the water quality to be unsafe for drinking directly from the source (Jain et al., 2000;
Singh et al., 2017). In another study carried out by Haloi & Sarma (2012) in Barpeta district,
Table 6.2: Variations in water quality parameter analysis carried out in wards/zones of the study area
Ward(W) / Zones(Z)
Sample
size pH Conductivity (mmho/cm)
Sodium (mg/L)
Potassium (mg/L)
Calcium (mg/L)
Iron (mg/L)
Fluoride (mg/L)
Arsenic (µg/L)
Nitrate (mg/L as NO3- -N)
Alkalinity (mg/L as
CaCO3)
Hardness (mg/L as CaCO3) W 1 94 6.54 ↔ 7.96 0.18 ↔ 1.59 8.25 ↔ 85.63 0.38 ↔ 8.29 4.03 ↔ 128.43 0.16 ↔ 2.03 0.02 ↔ 0.96 0.00 ↔ 9.79 0.00 ↔ 9.25 2.00 ↔ 18.00 14.00 ↔ 326.00 W 2 94 6.48 ↔ 8.43 0.12 ↔ 1.14 1.25 ↔ 71.26 0.25 ↔ 36.02 1.68 ↔ 118.13 0.12 ↔ 1.01 0.12 ↔ 2.76 0.00 ↔ 3.74 0.00 ↔ 8.51 2.00 ↔ 10.00 24 .00↔ 286.00 W 3 93 6.39 ↔ 7.77 0.06 ↔ 1.41 6.23 ↔ 61.63 0.37 ↔ 29.33 1.58 ↔ 119.56 0.12 ↔ 0.95 0.09 ↔ 1.51 0.00 ↔ 9.86 0.00 ↔ 7.16 2.00 ↔ 12.00 40.00 ↔ 294.00 W 4 93 6.68 ↔ 8.39 0.13 ↔ 5.57 2.30 ↔ 35.31 0.08 ↔ 7.58 0.61 ↔ 137.47 0.09 ↔ 0.49 0.03 ↔ 1.96 0.00 ↔ 8.33 0.00 ↔ 9.12 2.00 ↔ 20.00 28.00 ↔ 202.00 W 5 93 6.84 ↔ 8.50 0.13 ↔ 5.57 2.30 ↔ 35.31 0.08 ↔ 7.58 0.61 ↔ 137.47 0.05 ↔ 2.94 0.04 ↔ 7.93 0.00 ↔ 4.69 0.00 ↔ 34.00 0.00 ↔ 24.00 20.00 ↔ 202.00 W 6 92 6.34 ↔ 8.03 0.06 ↔ 1.65 6.23 ↔ 61.63 0.48 ↔ 11.33 0.66 ↔ 119.56 0.11 ↔ 1.19 0.01 ↔ 2.02 0.00 ↔ 28.36 0.00 ↔ 8.92 2.00 ↔ 10.00 54.00 ↔ 286.00 W 7 94 6.67 ↔ 8.27 0.15 ↔ 2.39 2.99 ↔ 42.53 0.25 ↔ 12.17 2.82 ↔ 75.53 0.09 ↔ 1.22 0.34 ↔ 1.84 0.00 ↔ 35.70 0.00 ↔ 10.29 2.00 ↔ 16.00 28.00 ↔ 262.00 W 8 91 6.56 ↔ 8.12 0.09 ↔ 1.78 6.23 ↔ 62.53 0.71 ↔ 30.23 8.74 ↔ 122.82 0.18 ↔ 0.93 0.57 ↔ 1.09 0.00 ↔ 28.36 0.00 ↔ 8.31 2.00 ↔ 10.00 28.00 ↔ 286.00 W 9 91 6.56 ↔ 8.12 0.09 ↔ 1.78 6.23 ↔ 62.53 0.71 ↔ 30.23 8.74 ↔ 122.82 0.18 ↔ 0.93 0.32 ↔ 1.09 0.00 ↔ 28.66 0.00 ↔ 8.31 2.00 ↔ 10.00 20.00 ↔ 286.00 W 10 92 6.77 ↔ 8.28 0.19 ↔ 1.41 7.73 ↔ 40.88 0.60 ↔ 52.51 0.23 ↔ 225.79 0.03 ↔ 0.69 0.48 ↔ 2.04 0.00 ↔ 2.40 0.00 ↔ 8.85 2.00 ↔ 10.00 16.00 ↔ 264.00 W 11 94 6.52 ↔ 8.51 0.12 ↔ 1.69 2.10 ↔ 60.28 0.60 ↔ 14.61 0.03 ↔ 103.24 0.03 ↔ 0.48 0.02 ↔ 2.21 0.09 ↔ 17.47 0.00 ↔ 8.52 0.00 ↔ 104.00 36.00 ↔ 374.00 W 12 95 7.04 ↔ 8.55 0.23 ↔ 1.17 10.46 ↔ 46.13 2.49 ↔ 63.52 0.83 ↔ 106.74 0.02 ↔ 0.78 0.16 ↔ 2.58 0.00 ↔ 4.57 0.00 ↔ 8.99 2.00 ↔ 12.00 20.00 ↔ 224.00 W 13 95 6.74 ↔ 8.4 0.20 ↔ 47.13 5.54 ↔ 38.28 0.60 ↔ 6.30 18.45 ↔ 101.31 0.06 ↔ 8.42 0.50 ↔ 3.06 0.00 ↔ 5.45 0.00 ↔ 8.79 0.00 ↔ 10.00 14.00 ↔ 210.00 Z 1 83 6.56 ↔ 8.37 0.29 ↔ 1.51 9.33 ↔ 42.48 1.27 ↔ 52.81 1.78 ↔ 227.95 0.13 ↔ 1.67 0.10 ↔ 2.10 0.30 ↔ 2.70 0.00 ↔ 8.67 2.00 ↔ 10.00 17.60 ↔ 379.20 Z 2 90 6.78 ↔ 8.09 0.3 ↔ 47.12 5.11 ↔ 33.09 0.61 ↔ 22.64 13.03 ↔ 92.53 0.11 ↔ 21.00 0.05 ↔ 1.95 0.50 ↔ 17.70 0.00 ↔ 9.64 0.00 ↔ 10.00 28.00 ↔ 124.00 Z 3 93 6.64 ↔ 6.99 0.11 ↔ 25 6.60 ↔ 23.58 0.86 ↔ 12.63 2.36 ↔ 32.67 0.06 ↔ 1.43 0.00 ↔ 2.00 0.10 ↔ 16.80 0.00 ↔ 8.90 2.00 ↔ 10.00 22.80 ↔ 374.80 Z 4 91 6.53 ↔ 7.12 0.12 ↔ 0.95 9.28 ↔ 22.56 0.48 ↔ 11.33 0.66 ↔ 44.55 0.11 ↔ 1.65 0.01 ↔ 2.02 0.00 ↔ 12.30 0.00 ↔ 9.42 2.00 ↔ 10.00 28.00 ↔ 124.00 Note: The data is presented in XX ↔ YY format where XX is the minimum value and YY is the maximum value
Page 6-5
Table 6.3: Percentage of samples exceeding WHO guidelines in respective wards/zones
Wards(W)/
Zones(Z) Sample size
% of samples exceeding WHO guidelines (WHO, 2008) Iron Fluoride Arsenic
W 1 94 88 0 0
W 2 94 89 32 0
W 3 93 67 1 0
W 4 93 23 14 0
W 5 93 6 12 0
W 6 92 58 3 14
W 7 94 15 7 73
W 8 91 92 0 22
W 9 91 96 0 23
W 10 92 62 12 0
W 11 94 12 15 6
W 12 95 18 58 0
W 13 95 15 31 0
Z 1 83 65 18 0
Z 2 90 78 22 11
Z 3 93 55 3 1
Z 4 91 58 1 2
Total 1568 52 14 9
guideline value of 0.3 mg/L.
Iron effect
Consumption of iron contaminated water has no direct adverse health effect (Idoko, 2010;
Naser et al., 2018). However, it imparts color to water, bitter taste to food and causes staining of clothes and utensils (Idoko, 2010). The thumb rule followed by researchers to recognize iron contamination is by physical observations i.e. taste, staining on containers, red coloration nearby hand pumps. It is reported that concentrations of iron >0.3 mg/L impart bitter taste and produces reddish-brown rust-colored stains on storage containers and utensils, further higher concentrations may also cause coloration of surroundings of water source (Naser et al., 2018). On the same line, household owners in the study area reported experiences of bitter taste and staining of water storage containers as well as surrounding of groundwater sources e.g. hand pump, water filters, etc. The percentage households reporting staining of water storage containers and hand pump
Figure 6.1: Location map of iron concentration in the study area with respect to WHO limit of 0.3 mg/L.
Figure 6.2: Precipitated iron besides groundwater sources.
10.65%. The photographs showing alarming levels of iron staining surrounding hand pumps and in filters were captured during sample collection and presented in Figure 6.2. Similar studies in
taste in 42% of household groundwater sources and staining of storage containers in 37%
household groundwater sources (Naser et al., 2018).
6.3.3 Fluoride
As per WHO guidelines and BIS permissible limits, fluoride in drinking water should be below 1.5 mg/L, however, the desirable concentration of fluoride in drinking water is within 1-1.5 mg/L (BIS 10500, 2012; WHO, 2008). The collected groundwater samples showed variable levels of fluoride in different wards/zones. Wards W1, W8 and W9 did not show any fluoride contamination, whereas highest percentage of noncomplying fluoride concentration was observed in ward W12. In fact, 14% of the samples in the study area had exceeded stipulated WHO guideline/BIS permissible limits for fluoride as shown in Table 6.3. Figure 6.3 shows the sample locations considering 1.5 mg/L as threshold fluoride concentration in the study area. The results
Figure 6.3: Location map of fluoride concentration in the study area considering 1.5 mg/L as threshold concentration.
from this study were analogous to those reported in literature and are in line with similar research findings on groundwater quality carried out for Central Guwahati, Nagaon and Karbi Anglong (Das et al., 2003; Haloi & Sarma, 2012; Singh et al., 2017). Although, concentration of fluoride
preventing dental fluorosis, especially among children. The percentage of households with groundwater concentration less than desirable (1 mg/L) were 20.03%. The wards W1, W8 and W9 showed lowest fluoride concentrations.
Figure 6.4: Effect of fluoride on children’s teeth after consumption of fluoride contaminated water.
In the present study area, 56.51% households have reported that some of their family members were observed to have yellowish colored teeth whereas pits or cavity in the teeth of children were observed in 4.72% of the households. Figure 6.4 shows yellowish colored teeth among children in W5, and W12. Similar harmful effects have also been observed in other parts of the country where the fluoride content was more than permissible limit. For example, in Siddipet (Telangana), it has been reported that fluoride contamination had resulted in large scale dental fluorosis amongst the people of that area (Narsimha & Sudarshan, 2017). Susheela et al. (1993) in their study on health complaints of 1958 peoples in Faridabad (Haryana) revealed that 58, 27 and 41% of people were affected with dental fluorosis, skeletal fluorosis and non-skeletal manifestations, respectively.
Though fluoride content was observed to be above permissible limit in the study area and cases of dental fluorosis are possibly present in the study area, however symptoms of skeletal fluorosis and non-skeletal manifestations were not observed among the people.
6.3.4 Arsenic
As per WHO guidelines, arsenic in drinking water should be below 10 µg/L (WHO, 2008)
10500, 2012). It is well documented that high-levels of arsenic exposure causes chronic health effects which includes cancer, skin pigmentation, skin lesions, respiratory, neurological and hematological effects in human (Mukherjee et al., 2006; Yoshida et al., 2004). The results of arsenic analysis revealed that the highest concentration of arsenic was 35.7 µg/L, observed in W7.
The results indicate that 9% of samples exceeded WHO guidelines limit but were well within BIS guidelines limit of 50 µg/L. Figure 6.5 shows groundwater locations in the study area exceeding (> 10 µg/L) and within (< 10 µ g/L) WHO guidelines limits. The study results are in line with the findings of literature that reports that groundwater in vicinity of the Brahmaputra river is contaminated with high concentration of arsenic (Nickson et al., 2007; Singh, 2006). A study on groundwater analysis of 5,729 government hand pumps in 22 districts of Assam reported that overall 6.3% of groundwater sources contained arsenic in concentrations greater than 50 µg/L (Nickson et al., 2007). Another study reported presence of arsenic in Dhemaji and Karimganj districts of Assam exceeding WHO guidelines limit of 10 µg/L (Bhattacharya et al., 2008).In th study area, pigmentation was observed in 2.93% households (any member of the household), however there were no occurrences of keratosis noticed in surveyed samples. Keratosis prevalence is usually observed in areas with high arsenic concentration i.e. > 10 µ g/L (Mazumder, 2003)
which is not prevalent in our study area. Of the 1568 households, 44 males and 2 females have skin pigmentation whereas no symptoms of keratosis were observed.
6.3.5 Combined Presence of Iron, Fluoride and Arsenic
The severity of household groundwater contamination in simultaneous occurrences of iron, fluoride and arsenic was investigated, compared with WHO guidelines and results are shown in Table 6.4 (WHO, 2008). It can be observed that considering iron and fluoride contamination at the same time 7% i.e. 106 samples exceeded WHO limits. The samples locations showing the iron and fluoride concentrations considering 0.3 and 1.5 mg/L respectively as threshold values are shown in Figure 6.6. Altogether 63 samples showed simultaneous occurrence of iron and arsenic beyond prescribed limits. The sampling locations exceeding iron and fluoride beyond permissible limits were in W3, W5, W6, W7, W11, Z2 and Z4 as shown in Figure 6.7. However, only 12 samples reported simultaneous occurrence of fluoride and arsenic, which was found in W5, W7, W11 and Z2 as shown in Figure 6.8. Simultaneous occurrence of these three contaminants (iron, fluoride and arsenic) was observed only in 1% of the total samples (Figure 6.9) in W5, W7, W11 and Z2.
Although simultaneous occurrence of the contaminants was not very severe in the study area, it is reported to be more often in other parts of the region. Groundwater quality analysis in Lakhimpur district of Assam reported that 6 out of 8 locations showed simultaneous occurrence of iron and arsenic, whereas fluoride was absent in all the samples (Hazarika & Bhuyan, 2013). A study carried out at Darrang district of Assam analyzed 25 samples at different locations and observed that 11 samples exceeded WHO guidelines limit for iron, whereas only one sample exceeded arsenic limit and reported no fluoride contamination (Borah et al., 2010). However, in our study fluoride contamination was detected with simultaneous occurrences of arsenic and iron at many instances as shown in Table 6.4.
Table 6.4: Number of samples contaminated by combined contaminants and its compilation with WHO guidelines
Combination of contaminants Exceeding WHO guidelines limit (out of 1568 samples) No of samples exceeding Percentage of samples
Iron & Fluoride 106 7
Fluoride & Arsenic 12 1
Arsenic & Iron 63 4
Figure 6.6: Simultaneous occurrences of iron and fluoride in study area considering 0.3 and 1.5 mg/L as threshold concentration, respectively.
Figure 6.7: Simultaneous occurrences of iron and arsenic in study area considering 0.3 mg/L and
Figure 6.8: Simultaneous occurrences of fluoride and arsenic in study area considering 1.5 mg/L and 10 µg/L as threshold concentration, respectively.
Figure 6.9: Simultaneous occurrences of iron, fluoride and arsenic in study area considering 0.3
6.3.6 Groundwater Contamination and Topography/Geology of Region
The analogy in groundwater quality and topography/geology of the region was investigated.
The parameters chosen were elevations of sampling locations and mineralogy of soil. The investigation revealed an interesting pattern of groundwater contamination showing higher contamination at foot hills and reducing radially outwards. The laboratory analysis of fluoride and arsenic gave higher values at foothills of Kamakhya, Ganeshpara hill (near Maligaon), and Assam Engineering College hill. It was further observed that the level of groundwater contamination reduced as one moves away from the hills. Similar observations for whole Northeast India including Assam were reported by Singh (2004) and Ramanathan et al. (2009) wherein the concentration of arsenic contaminant was reported to be prevalent near the foothills. The groundwater contamination in this region is reported to be due to dissolution of particular bedrock layer at a certain depth (Ramanathan et al., 2009). The dissolution is expected to be higher at foothills at certain depth contributing fluoride, arsenic and iron contamination of aquifers in its vicinity. In addition, the study region has two types of rocks viz. horneblende diorite and amphibolites that contributed to the contamination of groundwater (Chakrabarty & Sarma, 2011b;
Sharma et al., 2012).