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Chapter 3
MATERIALS AND METHODOLOGY
The general description of the physical location and other characteristics of the study
area, detailed information of sampling points along with their geographical location and
the methods adopted to monitor the drinking water quality parameters have been
discussed in this chapter.
3.1 Study area
3.1.1 Physical location
Dhemaji district in one of the districts situated in the remote corner of North East India on
the north bank of river Brahmaputra, is located between the latitudes of 270 05
/ 27
// N and
270 57
/ 16
// N and longitudes of 94
0 12
/ 18
// E and 95
0 41
/ 32
// E (Map 3.1). The district is
a basically plain area lying at an altitude of 104 m above the mean sea level. The
boundaries of the district are the hilly ranges of Arunachal Pradesh to the North and the
East, Lakhimpur district in the West and the river Brahmaputra covers the Southern
border of the district. The district is divided into 2 sub-divisions viz. Dhemaji and Jonai,
comprising of 5 development blocks (Dhemaji, Sissiborgaon, Bordoloni, Machkhowa and
Morkong selek). The district head quarter is at Dhemaji. Further the district is divided
into 65 gaon panchyat comprising of 1, 315 villages. The district covers 3, 237 sq. km of
area. As per census report 2001, total population of the district is 5, 71, 944 (rural: 5, 33,
112 & urban: 38, 832) bearing literacy rate 64.48 % (Statistical hand book, Assam, 2004;
Assam at a glance, 2005).
3.1.2 Soil morphology
Physiographically, the district is more or less flat and the area can be divided into high-
level plain of Brahmaputra river (between altitudes 107 m & 122 m AMSL) and flat flood
plain area (between altitudes 89 m & 96 m AMSL). Geologically, older and newer
alluvium occupies the area. Piedmont deposits of older alluvium consist of boulders,
cobbles, gravel, sand and silt. Flood plain and younger alluvial plains of newer alluvium
consist of gravel, pebble, coarse to medium sand, silt and clay. Ground water occurs
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under phreatic condition in the shallow aquifer zone and under semi-confined condition in
the deeper aquifer. Flow of ground water is from north to south. Pre-monsoon water level
varies from 0.01 to 9.40 mbgl and during post-monsoon period, water level varies from
0.56 to 8.26 mgbl. In locales, Long-term water level shows no significant change in the
area.
The general geochemical characteristics of the soil are highly acidic. However,
new alluvial soils formed due to inundation of land by river at intervals contain more
percentages of fine sand fine silt and are less acidic. Such soils are often neutral and even
alkaline. The soils of this district can be broadly classified into three different zones viz.
the foothill soils, active flood plain soils near the river Bramhaputra and the low-lying
marshy lands. Piedmont deposits comprising of coarse clastic sediments like boulder,
pebble, cobble, gravel associated with minor fraction of sand and silt are the main
repository in the foothill zone. The piedmont zone extends up to 4–6 km from the
foothills. The floodplain area comprising sand, silt, clay, gravel and pebble received from
the rivers coming from the upper reaches are the main deposits next to the piedmont
deposits. All these formations act as good reservoirs of ground water in the area. Ground
water in the floodplain area occurs under phreatic condition in the shallow aquifer zone
and under semi-confined condition in the deeper aquifer. The flow of ground water is
from north to the south. The occurrence and movement of ground water is controlled by
topogragraphy, geomorphology, climate, geology etc. Rainfall is the main source of
ground water recharge, although seepage from canal, return flow from applied irrigation,
seepage from surface water body etc. takes place. The soil of the district is broadly
classified into four groups, namely new alluvial, old alluvial, red loamy and lateritic soil.
The new alluvial soil is found in the flood plain areas subjected to occasional flood and
consequently receives annual silt deposit when the flood recedes. The old alluvial soils
are developed at higher level and are not subjected to flooding. Red loamy soils are
formed on hill slopes under high rainfall conditions (Ground Water Information Booklet,
2008).
15
Map 3.1: A cross sectional view of the study area, Dhemaji district in Assam, India
16
3.1.3 Drainage system of rivers
The district is in a strategic location where steep slope of Eastern Himalayas abruptly
drop forming a narrow valley, which widens towards the western side. Numerous
drainage systems originating from the hills of Arunachal Pradesh flow through this
narrow valley ending at the mighty river Brahmaputra. In general the slope of the
triangular district drops from northern and eastern corners towards south and western
sides. After the confluence the three mighty rivers i.e. Dihing, Dibang and Lohit from
their hilly course to the valley exert tremendous impact of peak runoff at the eastern most
corner of Dhemaji district, making the district vulnerable to annual flooding. After the
great earthquake in 1950 the Brahmaputra riverbed is rising continuously due to
deposition of sand carried down from upstream. This has led to the formation of a saucer
shaped low-lying zone in the plains of the district. The river Brahmaputra flows from East
to West in the Southern part of the district. Different tributaries originating from
Arunachal Pradesh in the North, flow South-West carrying enormous amount of alluvium
through the district before meeting the river Brahmaputra. The tributaries of the region
are- Silley, Sibia, Leko, Jonai Korong, Dikhari, Narod, Somkhong, Tongani, Burisuti,
Simen, Dimow, Gai-nadi, Moridhal, Jiadhal/Kumotia, Korha/Sila, Charikaria, Na-noi,
Sampara Suti, Subansiri. This region covers one of the heaviest rainfall areas in Assam
due to which these areas experience regular annual floods. Nearly 27% of the net cropped
is flood prone as well as flood affected. The intensity of floods can well be imagined
during the months when the waters of the Brahmaputra synchronize with that of the other
tributaries (Ground Water Information Booklet, 2008).
3.1.4 Meteorological data
The district is located near the foothills of Arunachal Pradesh; it exhibits difference in
temperature, rainfall, fog, wind etc. The climate of the district is characterized by high
rainfall, mild summer and winter and falls under cool to warm sub-humid thermic-agro
ecological sub-zone. The district experiences a dry and hot season of maximum
temperature of 39.90C. Summer rain in heavy and is principally caused from late June to
early September by the moisture- laden south west monsoon, on striking the Himalayan
foothills of the North. The annual rainfall of the district ranges from 2,600 mm to 3,200
mm with an average of 3,459.2 mm. Rainfall generally begins from April and continues
till the end of September. On an average there are about 200 days with 3.5 mm or more
rain in a year. It gets cooler as the months progress. Winters extend from the month of
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October to February, and are cold and generally dry, with minimum temperature of 5.90C.
In general temperature varies from 100C to 37
0C and during winter, temperature goes
down to as low as 20C to 5
0C. The relative humidity varies from 90 to 73 per cent. It gets
quite chilling in late December and early January, in account of snowfall in the upper
reaches of Arunachal Pradesh. Springs are cool and pleasant, occurring in the months of
late March and April. Of course during these months, flash rains and thunder stroms are
at times caused by cyclonic winds, known in local parlance as ‘Bordoichila’ (Ground
Water Information Booklet, 2008).
3.2 Sampling information
3.2.1 Collection and storage of water samples
Water samples were collected in pre-cleaned polythene containers of five litre capacity.
The containers were pre-washed with chromic acid solution, rinsed with distilled water
several times and dried thoroughly before use. For bacteriological analysis, water samples
were collected in sterilized glass bottles. The containers in all cases were filled as much
as possible and tightly closed to avoid contact with air or to prevent agitation during
transport. Water samples collected in this work were of the nature of integrated samples.
A number of grab samples were collected and then mixed together to obtain an integrated
sample. Necessary precautions were taken to collect sample from a well mixed zone
avoiding floating materials. Preservation and storage of samples were done following
standard procedure. The parameters like pH, conductivity and turbidity of the water
samples were measured immediately after collection. The dissolved oxygen (DO) and
temperatures were determined at the time of collection itself. For estimating metals, the
samples after collection, were acidified with nitric acid to pH 2.0 and then kept at - 40C in
a refrigerator. The microbiological analysis of the water samples were carried out
immediately after sample collection to prevent death of micro-organisms. The locations
of the sampling points were obtained with a hand held global positioning system (GPS,
Germin 72 model) with position accuracy of less than 10m.
3.2.2 Selection of sampling seasons
On the basis of the average rainfall and other climatic conditions, the water samples were
collected from different sampling stations during a year – Dry season (November - April)
and Wet season (May - October) and repeated for three years (November 2007 – October
2010).
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In this study six seasons were covered as shown below:-
S1 (Dry) : November 2007 --- April 2008
S2 (Wet) : May 2008 ---October 2008
S3 (Dry) : November 2008 --- April 2009
S4 (Wet) : May 2009 --- October 2009
S5 (Dry) : November 2009 --- April 2010
S6 (Wet) : May 2010 --- October 2010
3.2.3 Demarcation of study area
After a careful study of the topography and other aspects of the Dhemaji district, 240
drinking water samples were collected from 40 different sampling stations, namely tube
wells (120 samples), ring wells (60 samples), public water supplies (48 samples) and
rivers (12 samples) at different sites from each of the five development blocks of the
district during November 2007 – October 2010. In each set, samples were collected from
the same location of the site as far as practicable. All the tubewells are shallow in depth
(6m -10m) as the water level is very high in the whole district. The source and block-wise
sample collection summary is given in Table 3.1
Table 3.1: Source wise and block wise sample collection summary
Block wise sample identification number Sampling
Source Dhemaji Sissiborgaon Machkhowa
Bordoloni Morkongselek
Total
Sampling
points
TW A1, A2,
A7, A8
B1, B2,
B7, B8
C1, C2,
C7, C8
D1, D2,
D7, D8
E1, E2,
E7, E820
RW A3, A4 B3, B4 C3, C4 D3, D4 E3, E4 10
PWS A5, A6 B5 C5, C6 D5 E5, E6 08
R --- B6 --- D6 --- 02
Total 08 08 08 08 08 40
(TW: tubewell, RW: ringwell, PWS: public water supply and R: river)
19
3.2.4. Geographical location of sampling stations
The physical locations of different sampling stations along with their location map
are given in Table 3.2 and Map 3.2. Moreover, photographs of some of the water
sampling sources of tubewell, ringwell, public water supply and river are given in Plate
3.1(a) and Plate 3.1 (b)
Table 3.2: Physical location of sampling stations in the study area
Sampling Location Geographical Location Sample No.
(Source)
Name of G.P. Name of Village North (N) East (E)
A1 (TW)Bishnupur No.2 Tekjuri 27
0 29.546
/ 94
0 32.426
/
A2 (TW)Lakhipathar Jamuguri 27
0 31.342
/ 94
0 35.479
/
A3 (RW)
Chamarajan Kekuri 270 25.690
/ 94
0 29.345
/
A4 (RW)Naruathan Balijan 27
0 24.601
/ 94
0 25.267
/
A5 (PWS)
Aradhal Kulapathar 270 28.792
/ 94
0 32.949
/
A6 (PWS)
Moridhal Perabhari 27
0 32.353
/ 94
0 35.776
/
A7 (TW)Jiadhal Tinigharia 27
0 26.189
/ 94
0 30.915
/
A8 (TW) Hatigor Telijan 270 26.939
/ 94
0 32.829
/
B1(TW)Sissiborgaon Takaobari 27
0 33.567
/ 94
0 40.267
/
B2 (TW) Silasuti Silagaon 270 35.475
/ 94
0 44.219
/
B3 (RW)Siripani Siripani 27
0 34.156
/ 94
0 38.387
/
B4 (RW)
Malinipur Khanamukh 270 37.602
/ 94
0 45.314
/
B5 (PWS) Akajan Akajan 270 34.603
/ 94
0 40.326
/
B6 (River) Nilakh Baligaon 27
0 34.074
/ 94
0 41.252
/
B7 (TW)Dimow Dizmur Miri 27
0 41.052
/ 94
0 48.639
/
B8 (TW)Muktiar Thekeraguri 27
0 38.764
/ 94
0 49.603
/
C1 (TW)Machkhowa Borpak 27
0 18.806
/ 94
0 32.608
/
C2 (TW)
Begenagara Kaitog 27
0 21.363
/ 94
0 32.471
/
20
C3 (RW)
Jorkata Kathgaon 270 12.416
/ 94
0 35.237
/
C4 (RW)
Sissimukh Sisi-Nepali 27
0 13.623
/ 94
0 36.706
/
C5 (PWS)
Machkhowa Majgaon 270
19.623/ 94
0 33.347
/
C6 (PWS)
Jorkata Jorkata-Nepali 27
0 30.023
/ 94
0 35.932
/
C7 (TW)Machkhowa Depwaguri 27
0 22.064
/ 94
0 35.017
/
C8 (TW)
Machkhowa Deogharia 27
0 21.786
/ 94
0 34.240
/
D1 (TW)Bordoloni Kalitagaon 27
0 24.829
/ 94
0 25.117
/
D2 (TW)
Gogamukh Silimpur 27
0 25.477
/ 94
0 19.058
/
D3 (RW)
Borbam Salmari 270
43.037/ 94
0 26.012
/
D4 (RW)
Gugamukh Tajik Nepali 27
0 24.489
/ 94
0 19.882
/
D5 (PWS) Bhebeli Bhebeli 270
24.983/ 94
0 22.354
/
D6 (River) Mingmang Mingmang 270
48.643/ 94
0 19.012
/
D7 (TW)Nalbari Sontapur 27
0 49.732
/ 94
0 26.437
/
D8 (TW)Misamari Bokulbari 27
0 42.563
/ 94
0 25.780
/
E1 (TW)Simen Chapari Baghagaon
270
41.672/ 94
0 50.436
/
E2 (TW)Laimekuri Adikata 27
0 44.719
/ 95
0 05.241
/
E3 (RW)
Telem Telem-pathar 270
45.865/ 95
0 00.611
/
E4 (RW)
Jonai Jonai Bazar 270
49.493/ 95
0 13.735
/
E5 (PWS)
Silley No.1 Jelem 270
50.618/ 95
0 14.726
/
E6 (PWS)
Dekapam Bijoypur 27
0 45.218
/ 94
0 55.934
/
E7 (TW)Somkong Apsora 27
0 43.014
/ 94
0 52.921
/
E8 (TW)Galisikari Bor-Camp 27
0 45.314
/ 95
0 07.437
/
21
Map 3.2: Map showing the 40 sampling stations of the study area
22
Sampling station (A8) Sampling station (C2)
Sampling station (D1) Sampling station (A3)
Sampling station (D4) Sampling station (C3)
Plate 3.1 (a): Photographs of some of the water sampling sources of tubewell and
ringwell
23
Sampling station (A5) Sampling station (C5)
Sampling station (A6)Sampling station (B6, River Gai-nadi)
Sampling station (D6, River Subansiri) Sampling station (D6, River Subansiri)
Plate 3.1(b): Photographs of some of the water sampling sources of public water supply and
river water
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3.2.5 Selection of drinking water quality parameters
The investigation was largely confined in monitoring water quality parameters. Although
the number of such parameters can be very large and new parameters have found entries
into the standard methodology in recent times, considering various factors such as
availability of analysis facilities and also due to shortage of time, the following
parameters were selected for monitoring the drinking water quality in this work.
a) Physical parameters: Temperature, Odour, Colour, Turbidity,
Conductance, pH, Total solids, Total
dissolved solid, Total suspended solids
b) Chemical parameters: Total hardness, Dissolved oxygen, Bio-
chemical oxygen demand, Chemical oxygen
demand, Chloride, Nitrate-nitrogen, Sulphate,
Fluoride, Sodium, Potassium, Calcium,
Magnesium, Iron, Lead, Copper, Aluminium,
Nickel, Cadmium, Manganese, Zinc,
Chromium and Arsenic
c) Microbial parameters: Total coliform organisms
3.2.6 Physical parameters
The Specific methodologies followed for measurement of each physical parameter are
stated below. The analyses were carried out within three months using standard methods
(APHA, 1998).
3.2.6.1 Temperature
In this work, temperatures of the water samples were determined immediately by using
mercury thermometer at the time of collection of the water samples.
3.2.6.2 Odour
In this work, odour of water sample was not measured, although some samples
particularly from tube wells had distinctive odours.
25
3.2.6.3 Colour
In the present study, the colours of the collected water samples were observed visually.
3.2.6.4 Turbidity
Turbidity of water samples was measured with a Nephelo-Turbidimeter (Model CL-52D,
ELICO, India) which works on the basis of light scattering by turbidity causing
substances. The volumes were calibrated with respect to a set of formazinsuspentions of
known turbidity and are given in Nephelometric Turbidity Units (NTU).
3.2.6.5 Conductance
Conductance was measured using a digital conductivity meter (Model: ACM-340913-R,
India), calibrated with 0.01 M KCl solution (of conductivity 1287 µS/cm at 298 K).
3.2.6.6 pH
All pH measurements were done using a digital pH meter (Model LT-120, ELICO, India).
The instrument was calibrated for each set of measurements with standard buffer
solutions.
3.2.6.7 Total solids
Total solids (TS) content of the water samples was determined as the residue left after
evaporation of the unfiltered sample. 50 ml of the unfiltered sample was taken in a pre-
weighted borosil beaker and evaporated carefully to dryness in a water bath. The residue
and the beaker were kept in an oven at 103-1050C till a constant weight was obtained.
The TS is given by-
V
B)x1000-(Amg/Lin TS =
Where, A= Final weight of the beaker and residue in gm
B= Initial weight of the beaker in gm
V= Volume of sample in ml
3.2.6.8 Total dissolved solids
Total dissolved solids (TDS) content of the water samples was determined as the residue
left after evaporation of the measured volume of the filtered sample. 50 ml of the filtered
sample was evaporated carefully to dryness in a water bath in a pre-weighted borosil
beaker. The residue and the beaker were further dried in an oven at 103-1050C till a
constant weight was obtained. The TDS is given by-
26
V
B)x1000-(Amg/Lin TDS =
Where, A= Final weight of the beaker and residue in gm
B= Initial weight of the beaker in gm
V= Volume of sample taken in ml
3.2.6.9 Total suspended solids
Total suspended solids (TSS) content of the water samples was obtained by subtracting
total dissolved solids from total solids.
TSS = TS – TDS
3.2.7 Chemical parameters
Chemical Parameters were measured by adopting the specific methods stated below. The
analyses were carried out within three months using standard methods. Analytical grade
reagents were used all throughout and all solutions were made in double distilled water.
Calibration of equipments was done carefully using standards methods possible
contamination from containers, beakers, flasks, etc. was avoided by taking adequate
precautions.
3.2.7.1 Total hardness
In this study the total hardness (TH) of the water sample were determined by using EDTA
titrimetric method, using Eriochrome Black-T (EBT) as an indicator.
Calculation:
TH as CaCO3 mg/L = (ml of EDTA used x 1000)/ml of sample
3.2.7.2 Dissolved oxygen
In this study dissolved oxygen (DO) of the collected water samples were measured by
Winkler’s iodometric method. In this method DO was allowed to react with iodide
solution to form I2 which was then titrated against standard sodium thiosulphate solution
(0.025N) adding Mn(II) salts in strong alkaline medium. The DO value is given by-
DO in mg/L = volume of thiosulphate solution (0.025 N) in ml
3.2.7.3 Bio-chemical oxygen demand
The method for determining Bio-chemical oxygen demand (BOD) consists in incubating
300 ml of water sample in a BOD- bottle at 200C for 5 days. The value is represented
27
BOD520
. DO was measured both before and after incubation. The pH of the water sample
was also maintained at around 7.2 by means of a phosphate buffer. Calculations were
expressed as-
P
mg/Lin BODif DODO −
=
Where, DOf = the final dissolved oxygen value
DOi = initial dissolved oxygen value
P = decimal volumetric fraction of dilution
In this study a BOD incubator (SICO, India) was used for incubation.
3.2.7.4 Chemical oxygen demand
In this study for evaluating the chemical oxygen demand (COD) values, the open reflux
method was used using dichromate as the oxidizer. Dichromate has superior oxidizing
ability and is suitable for almost all types of water samples. The essential technique
involves refluxing a water sample with an excess of potassium dichromate in a strongly
acidic medium. The excess of potassium dichromate is titrated against ferrous ammonium
sulphate using ferroin as an indicator. This procedure was repeated with blank taking
distilled water as the sample. Calculations are made as follows:
mlin sampleof Volume
8]A)xNx1000x[(Bmg/Lin COD
−=
Where, A= volume of ferrous ammonium sulphate required for the sample
B= volume of ferrous ammonium sulphate required for the blank
N=normality of ferrous ammonium sulphate solution
3.2.7.5 Chloride
Chloride (Cl-) in drinking water was estimated by the silver nitrate method, when silver
nitrate is allowed to react with a chloride in a neutral or slightly acidic medium, in
presence of potassium chromate, (which is added as an indicator) silver chloride is
quantitatively precipitated before silver chromate and appearance of red precipitate of red
silver chromate indicates the completion of the reaction. Chloride content is then
calculated as-
Cl- in mg/L
sampleof mL
100035.45NB)(A ×××−=
Where, A = Volume in ml of Ag NO3 required to titrate the water sample
28
B = Volume in ml of Ag NO3 required to titrate the same volume of
blank (distilled water)
N = Normality of Ag NO3 solution
As the presence of thiosulphate, cyanide, sulphite and sulphide interferes with this
method, these were removed by oxidation with 30% H2O2 solution prior to titration with
silver nitrate, Ag NO3
3.2.7.6 Nitrate-nitrogen
Nitrate-nitrogen (NO3- - N) in water sample was determined using UV spectrophotometric
technique (ELICO SL-159) by measuring the absorbance of the phenol-di-sulphonic acid
nitrate complex at 410 nm. Water samples were filtered and then 50 ml was evaporated to
dryness. The residue was dissolved in phenol-di-sulphonic acid. The content was diluted
to 50 ml and liquor ammonia was added to develop a yellow colour. The nitrate content
was read directly by operating the instrument in photometry mode calibrating against a
standard and a blank.
3.2.7.7 Sulphate
Sulphate (SO42-
) ion is precipitated in an acetic acid medium with barium chloride
(BaCl2) so as to form barium sulphate (BaSO4) crystals of uniform size. Light absorbance
of the BaSO4 suspension was measured by UV-Visible spectrophotometry ((ELICO SL-
159) and the concentration of the SO42-
ions were determined by comparison of the
reading with a standard curve. In this study 6 standards (5ppm, 10ppm, 20ppm, 30ppm,
40ppm and 50ppm) of SO42-
were prepared by exact dilution of the stock sulphate
solution for the preparation of the standard curve. The reliability of the calibration curve
was checked by running a standard with every three or four samples. In this study, 20ml
buffer solution was mixed with 100ml sample solution in Erlenmeyer flask; mixed the
solution in stirring apparatus. While stirring, a spoonful of BaCl2 crystals mixed and
stirred for 60±2 s. After the stirring period ended, the solution was taken in absorption
cell of the photometer and measured turbidity at 5 ± 0.5 min.
3.2.7.8 Fluoride
Fluoride (F-) in water sample was determined colorimetrically by SPADNS method,
[Sodium -2- (Parasulphopherylaze)-1, 8-dihydroxy-3, 6- naphthalene disulphonate] by
using a U.V. visible spectrophotometer (ELICO SL-159) at 570 nm. Sodium fluoride was
29
used to prepare the standard solution. The method is based on the reaction between F-
and a Zirconium dye lake. F- reacts with the dye lake, dissociating a portion into a
colourless complex anion (ZrF62-
) and the dye. Intensity of colour decreases with increase
in F- concentration.
3.2.7.9 Sodium
The concentrations of sodium (Na) were analysed flame photometrically by using
systronic flame photometer (Model: ELICO CL 22D) at a wavelength of 589 nm. The
sample was sprayed into a gas flame and excitation was carried out under controlled and
reproducible conditions. The desired spectral line was isolated by a suitable slit
arrangement in light-dispersing devices such as prisms or gratings. The intensity of light
(measured by phototube potentiometer or other appropriate circuit) was approximately
proportional to the concentration of the element. For the preparation of calibration curve,
the stock Na solution was prepared by dissolving 2.542 g of NaCl (dried at 1400C) and
diluted the solution to 1000 ml by adding distilled water (1.00 ml=1.00 mg Na).
Intermediate Na solution, was prepared by dissolving 10 ml standard (1000 ppm) Na
solution into 100 ml distilled water. 1ppm, 5ppm, 10ppm, 20ppm, 30ppm, 40ppm Na
solutions were prepared from the 100ppm solution and a blank was taken for the
preparation of the calibration curve. Starting with the highest calibration standard and
working toward the most dilute, the emission was observed at 589nm. The process was
repeated with both calibration standards and samples enough time to secure a reliable
average reading for each solution. After the determination of the calibration curve the
concentration of Na of the collected water samples were determined from the calibration
curve as given by the equation:
A]xDa)(b
a)A)(s(B[mg/Lin Na +
−
−−
=
Where, B= Na mg /L in upper bracketing standard
A= Na mg /L in lower bracketing standard
b= emission intensity of upper bracketing standard
a= emission intensity of lower bracketing standard
s= emission intensity of sample and
30
D= dilution ratio= (ml sample + ml distilled water)/ml sample
3.2.7.10 Potassium
The concentrations of potassium (K) were analysed flame photometrically by using
systronic flame photometer (Model: ELICO CL 22D) at a wavelength of 766.5 nm. To
prepare the calibration curve 1.907g KCl (dried at 1100C) was dissolved into 1000 ml
distilled water and it become a stock solution of 1000 mg/L 10 ml of the stock solution
was dissolved into 100ml distilled water to prepare the 100 ppm intermediate solution.
The K standards 1 mg/L, 5 mg/L, 10 mg/L, 20 mg/L, 30 mg/L and 40 mg/L were
prepared by appropriate dilution of the intermediate K solution. A blank and the standards
were taken for the preparation of the calibration curve. Starting with the highest
calibration standard and working toward the most dilute, the emission was observed at
766.5 nm. The process was repeated with both calibration standards and samples enough
time to secure a reliable average reading for each solution. After the determination of the
calibration curve the concentration of K of the collected water samples were determined
from the calibration curve as given by the equation:
A]xDa)(b
a)A)(s(B[mg/Lin K +
−
−−
=
Where, B= K in mg/L in upper bracketing standard
A= K in mg/L in lower bracketing standard
b= emission intensity of upper bracketing standard
a= emission intensity of lower bracketing standard
s= emission intensity of sample and
D= dilution ratio = (ml sample + ml distilled water)/ml sample
3.2.7.11 Calcium
EDTA-forms a complex with both calcium (Ca) and magnesium (Mg), but if the pH is
sufficiently high (12 to 13), Mg is precipitated as hydroxide and Ca-EDTA complex gives
a colour change with a suitable indicator (Murexide) when the complex formation is
complete. At the end point of the reaction colour of the solution changes from pink to
purple. In this study 100ml of the water samples were taken in 250 ml conical flask with
1ml sodium hydroxide (NaOH) solution and 0.6gm of murexide indicator. The solutions
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were titrated against 0.02 M standard EDTA solution. When reaction completed, the
colour changes from pink to purple and then EDTA reading were noted down for
determination of Ca concentration in the samples. The following equation is followed for
the calculations of Ca in water samples.
a) Calcium (as Ca) in mg/L= 400 V1/ V2
b) Calcium (as CaCO3) in mg/L = 1000 V1/ V2
Where V1 is the volume of the standard EDTA solution (0.02 M) used in the
titration and V2 is the volume in ml of the sample taken for titration.
3.2.7.12 Magnesium
In this study, the Mg concentrations of the water samples were calculated by using a
simple method from TH and Ca content. The following equation is followed for the
calculations of Mg.
Magnesium (as Mg) in ppm = 0.243 [TH (as CaCO3 ppm)] – [Calcium content
(as CaCO3 ppm)]
3.2.7.13 Iron
Iron (Fe) in water sample was measured by phenanthroline method. The detection limit is
50�g iron. In this method the ferric form of Fe is reduced to ferrous form by boiling with
HCl and hydroxylamine hydrochloride. Later 1, 10-phenanthroline is added at pH
between 3.2 and 3.3 to form soluble chelated complex of orange red colour with iron. The
resulting orange red solution was measured calorimetrically by using a UV-visible
spectrophotometer (ELICO SL-159) at 510 nm.
3.2.7.14 Lead, copper, aluminium, nickel, cadmium, manganese, zinc,
chromium and arsenic
The concentrations of Pb, Cu, Al, Ni, Cd, Mn, Zn, Cr and As were analysed by using
Atomic Absorption Spectrometer (Perkin Elmer AA- Analyst 200) with Flow Injection
Analyze Mercury Hydride Generation System (Model – FIAS-100) as per the standard
procedures (APHA, 1998). Different analytical wavelengths and slit width at which the
concentration of the respective metals were determined are given in Table 3.3
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Table 3.3: Characteristic wave lengths of measured heavy metals with their slit width
for AAS
Sl. No Elements Wave length (nm) Slit width (nm)
1 Lead (Pb) 283.3 0.7
2 Copper (Cu) 324.7 0.7
3 Aluminium (Al) 396.2 0.7
4 Nickel (Ni) 232.0 0.2
5 Cadmium (Cd) 228.8 0.7
6 Manganese (Mn) 279.5 0.2
7 Zinc (Zn) 213.9 0.7
8 Chromium (Cr) 357.9 0.2
9 Arsenic (As) 193.7 0.7
All the reagents and standards (analytical grade, purchased from Merck, India)
were prepared freshly at the time of analysis. A blank was analyzed between element
specific standard readings to verify baseline stability of the instrument. After a batch of
ten samples were analyzed, standard solution was additionally analyzed to confirm the
calibration of the instrument. The argon gas and sodium borohydrate were used for
hydride generation. The basic principle of the hydride generation AAS is the electrons of
the atoms in the atomizer can be promoted to higher orbital for a short amount of time by
absorbing a set quantity of energy (i.e. light of a given wavelength). This amount of
energy (or wavelength) is specific to a particular electron transition in a particular
element, and in general, each wavelength corresponds to only one element. This gives the
technique its elemental selectivity. As the quantity of energy (the power) put into the
flame is known, and the quantity remaining at the other side (at the detector) can be
measured, it is possible, from Beer-Lambert law, to calculate how many of these
transitions took place, and thus get a signal that is proportional to the concentration of the
element being measured.
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3.2.8 Microbial parameters
Test for total coliform organisms (Presumptive test)
Microbiological examination for total coliforms was carried out by the multiple tube
fermentation procedure and the results have been presented as most probable number
(MPN) index. The method is based on the ability of the coliform organisms to ferment
lactose producing an aldehyde complex and carbon dioxide gas. Water samples,
immediately after collection were distributed for multiple tube fermentation according to
the following dilutions:-
a) 5- tubes of 10 ml double strength medium (Lactose broth) + 10 ml of water sample.
b) 5- tubes of 10 ml single strength medium + 0.1 ml of water sample.
Fermentation was allowed to take place in a SICO incubator at 35 ± 0.5 0C. The
tubes were shaken gently after 24 ± 2 hours and examined for gas formation. If there was
no gas, the tubes were reincubated and re-examined at the end of 48 ± 3 hours. Formation
or absence of gas was recorded as a positive or negative presumptive test and the MPN-
indices were obtained following standard procedure (ICMR, 1963).
Indole Test
The presence of E. coli was tested by the indole formation test and was confirmed by
differential test. For indole test subcultures are made from the test tubes showing acid and
gas into peptone water by means of a transferring loop in presence of spirit lamp to test
tubes containing 2 ml peptone water and 1-inch long Durham's tube (previously
sterilized) and incubated at 440C at serological water bath for 48 hours. The yielding gas
shows indole positive and is regarded as containing Escherichia coli (ICMR, 1963).
3.3 Health hazard survey
A three year survey on health status of the people in the Dhemaji district was carried out
from November 2007 to October 2010 for 40 different locations which are given in Table
3.2 and locations of sample collection sites are shown in Map 3.2. The survey was non-
experimental and descriptive research method. The researcher visited every location as
mentioned in Table 3.2 and observed the water environment used by the people for
drinking purposes. Since populations in every location are quite large, the researcher
directly inter-acted only a small proportion of the population. A randomize representative
sample size of 400 was done by personally contacting the respondents. The collected
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were related to three years. After completing the collection process, the data were
processed, classified and tabulated for analysis. To arrive at conclusions regarding health
aspect of the people in the district, questionnaires (Annexure IV and Annexure V) were
designed very carefully relating to health hazards generally occur from water
environment and these were asked to the respondents. The filled up questions were
collected and then grouped for interpretation.
3.4 Data analysis
Data analysis and presentation, together with interpretation of the results and report
writing, form the last step in the water quality assessment process. It is this phase that
shows how successful the monitoring activities have been in attaining the objectives of
the assessment. It is also the step that provides the information needed for decision
making, such as choosing the most appropriate solution to a water quality problem,
assessing the state of the environment or refining the water quality assessment process
itself.
3.4.1 Statistical approach
In the present study, the tools used for data analysis are mainly experimental, aimed at
defining possible relationships, trends, or interactions among the measured variables of
interest. The observed parameters are related graphically. Sample data are subjected to
statistical treatment using normal distribution statistic. Details of these may be found in
standard books on statistics (Meloun M. et al., 1992). Descriptive statistics in the forms of
mean, variance (V), standard deviation (SD), standard error (SE), median, mode,
skewness, std. error of skewness, kurtosis, std. error of kurtosis, range of variation, and
percentile at 75%, 50% and 25% (P75%, P50% and P25%) are calculated and
summarized in tabular form. Univariate statistics were used to test distribution normality
for each parameter. SPSS® statistical package (Window Version 10.0) was used for data
analysis.
3.4.2 GIS approach
The stress zone of selected variables for water data are delineated with curve fitting
method in arc view GIS software. The interpolation under spatial analyst tool will help to
predicts values for cells in a raster from a limited number of sample data points obtained
with a hand held global positioning system (GPS, Germin 72 model) with position
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accuracy of less than 10 m. It can be used to predict unknown values for any geographic
point data, such as elevation, rainfall, chemical concentrations, noise levels, and so on.
The interpolation for the seasonal water data had been done by using inverse distance
weighted method (IDW). Inverse distance weighted interpolation determines cell values
using a linearly weighted combination of a set of sample points. The weight is a function
of inverse distance. The surface being interpolated should be that of a locationally
dependent variable. Geographic information system (GIS) approach to develop spatial
information and knowledge based on the drinking water quality of the study area had
been found to be very useful. GIS database also helps in decision-making process by
identifying the most sensitive zones that need immediate attention.
