Download Assessment of Water Quality Index of Small Lake in South Gujarat

Assessment of Water Quality Index of Small
Lake in South Gujarat Region, India
Bhaven N. Tandel, Dr. JEM Macwan, and Chirag K. Soni
Abstract—The water quality index is a single number that
expresses the quality of water by integrating the water quality
variables. Its purpose is to provide a simple and concise method for
expressing the water quality for different usage. The present work
deals with the monitoring of variation of seasonal water quality index
of some strategically selected surface water bodies. The index
improves the comprehension of general water quality issues,
communicates water quality status and illustrates the need for and the
effectiveness of protective practices. It is found that in all cases the
change in WQI value follow a similar trend throughout the study
period. The lake water is found of good quality (WQI - 67.7 to 78.5)
during both seasons. However, it is found that water quality of lake
deteriorates slightly from winter to summer season on account of the
increase in microbial activity as well as increase in pollutants
concentration due to water evaporation.
Keywords—Water Quality, Water Quality Index, Water Quality
Parameters.
I. INTRODUCTION
T
HE availability of water both in terms of quality and
quantity is essential for the very existence of mankind.
Water, though indispensable and plays a pivotal role in our
lives, yet is one of the most badly abused resources. Lack of
awareness and civic sense, use of inefficient methods and
technology lead to more than 50% of water wastage in the
domestic, agriculture & industrial sectors. Water pollution is
rendering much of the available water unsafe for consumption.
There is heavy extraction of water for domestic, industrial and
agricultural purpose. Age-old customs and habits of
community, cattle bathing and washing in rivers are
responsible for rampant pollution of river water. The release of
domestic waste water, agricultural runoff water & industrial
effluents promote excessive growth of algae in water bodies,
which results in their eutrophication.
Several states in the country are facing problems due to over
exploitation of ground water resources and pollution of surface
water. Its manifestations are declining per capita water
availability, falling water tables and deterioration of water
Bhaven N Tandel is with S. V. National Institute of Technology, Surat,
Gujarat State, 395 007, INDIA (corresponding author) phone: +91-98255
53175; fax: +91-261-2201624; e-mail: [email protected]
Dr. JEM Macwan, is with S. V. National Institute of Technology, Surat,
Gujarat State, 395 007, INDIA phone: +91-94271 48108; fax: +91-2612201624; e-mail: [email protected]
Chirag K. Soni was a M. Tech. (Scholar) at S. V. National Institute of
Technology, Surat, Gujarat State, 395 007, INDIA
quality. Unfortunately, the inability of the authorities to keep a
check on the issue is also to blame for this state of affairs.
These increasing imbalances and anomalies shed doubt on the
long term availability of water resources. Accurate information
on the condition and trends of water resources quantity and
quality is required as a basis for economic and social
development, and for the development and maintenance of
environmental quality.
There has been increased interest and work over the past
few years on the use of indicators to monitor change. Water
quality index is one of the most effective tools to communicate
information on the quality of water to the concerned citizens
and policy makers. It, thus, becomes an important parameter
for the assessment and management of surface water.
II. OBJECTIVES OF PRESENT WORK
The objective of the present research is to provide
information on the physico-chemical characteristics of lake
water in order to discuss it’s suitability for human consumption
based on computed water quality index values.
A. Parameters of water quality analyzed
For the assessment of water pollution status of the water
bodies, the following water quality parameters were analyzed:
(1) pH (2) Specific Conductance (3) Temperature (4) Total
dissolved solid (TDS) (5) Total Solids (TS) (6) Total
Alkalinity (7) Dissolved oxygen (DO) (8) Chemical oxygen
demand (COD) (9) Biochemical oxygen demand (BOD) (10)
Total Hardness.
B. Materials and Methods
1. Study area:
The study was carried out at lake which is a balancing
reservoir maintained to serve water requirement for irrigation
in region and operation of two Pressurized Heavy Water
Reactors (PHWRs) having capacity of 220 MWe each.
Nuclear Atomic Power Station is located on the southern bank
of Lake. Area of lake is about 8.5 km2 and Average depth 2 to
3 meter.
NPP is in commercial operation since last 17 years. Unit-I
of the NPP is in commercial operation since 1992 and Unit-II
is in commercial operation since 1995. Huge water
requirement of the plant for the process of cooling and raw
water system is met from the Lake.
NPP draws 2.77 m3/sec of water from the Lake through
intake point and after utilization in plant system it discharges
2.08 m3/sec of water through discharge point into the Lake.
The discharged water is further diluted and regulated at
downstream regulator, which further on its en-route is being
used for drinking, bathing, washing, and irrigation purpose in
different part of surrounding villages.
The sampling locations are based on the following criteria
and utilization of water. They are (1) Locations where
principal feeder tributary meets the lake (Upstream of the lake)
(2) at a central place of lake. (3) At a place from where water
is regulated for irrigation and human habitat for bathing and
washing. (Downstream of lake)
The sampling locations and their respective longitude /
latitude are given below:
Upstream location:
LONGITUDE
LATITUDE
1) S1 (feeder canal)
21º 15’ 37.3”
73º 21’ 12.3”
2) S2 (intake of NPP)
21º 14’ 23.5”
73º 20’ 59.9”
Downstream location:
1) S3 (discharge of NPP) 21º 14’ 15.7”
73º 20’ 35.6”
2) S4 (d/s regulator)
21º 13’ 41.7”
73º 19’ 17.5”
3) S5 (d/s location)
21º 13’ 49”
73º 17’ 33.8”
2. Laboratory Analysis:
Collected samples were subjected to filtration prior to
chemical analysis while temperature was determined in the
field. The water samples were then analyzed for 10
parameters: pH, total dissolved solids, conductivity, total
solids, chloride, dissolved oxygen, chemical oxygen demand,
biochemical oxygen demand, total hardness, and total
alkalinity using standard procedures of analysis (American
Public Health Association, 1995).
3. Calculation of WQI:
The Water Quality Index (WQI) was calculated using the
Weighted Arithmetic Index method. The quality rating scale
for each parameter qi was calculated by using this expression:
Quality rating, Qi = 100 [(Vn -Vi) / (Vs -Vi)]
Where, Vn: actual amount of nth parameter
Vi: the ideal value of this parameter
Vi = 0, except for pH and D.O. Vi = 7.0 for pH; Vi = 14.6
mg/L for D.O.
Vs: recommended WHO standard of corresponding
parameter
Relative weight (Wi) was calculated by a value inversely
proportional to the recommended standard (Si) of the
corresponding parameter:
Wi = 1 / Si
Generally, WQI are discussed for a specific and intended
use of water. In this study the WQI for human consumption is
considered and permissible WQI for the drinking water is
taken as 100. The overall WQI was calculated by using
Equation:
Water Quality Index (WQI ) = ∑ (Qi)Wi / ∑ Wi (WQI)
III. RESULTS AND DISCUSSION
TABLE I
SAMPLE CALCULATION OF WQI FOR S2 LOCATION IN SUMMER
Parameter
Mean
Test
Results
(Ci)
pH
BOD
COD
TS
8.3
2.9
9.4
224.8
TDS
DO
Total
Alkalinity
Conductiv
ity
Chlorides
Total
Hardness
Standard
Permissible
Value (Si)
Relative
weight
Wi
Qualit
y
Rating
Qi
Weighted
Qi Value
Units
mg/l
mg/l
mg/l
8.5
6.0
10
500.0
0.1176
0.1667
0.1000
0.0020
86.67
47.50
93.75
44.95
10.43
7.92
9.38
0.09
187.5
6.1
175.0
mg/l
mg/l
mg/l
500.0
5.0
200.0
0.0020
0.2000
0.0050
37.50
88.54
87.50
0.08
17.65
0.44
324.5
µs/cm
300.0
0.0033
108.17
0.36
29.5
mg/l
250.0
0.0040
11.80
0.05
115.0
mg/l
300.0
0.0033
38.33
0.13
Unit
∑Wi:
0.60
∑Wi Qi:
46.51
WQI : ∑ Wi Qi / ∑ Wi = 46.51 / 0.60 = 77.0
TABLE II
WATER QUALITY CLASSIFICATION BASED ON WQI VALUE
WQI Value
Water Quality
<50
Excellent
50-100
Good water
100-200
Poor water
200-300
Very poor water
>300
Water unsuitable for drinking
TABLE III
COMPUTED WQI VALUES FOR ALL SAMPLING LOCATION IN WINTER AND
WINTER
SUMMER
LOCATION
WQI
LOCATION
WQI
S1
72.82
S1
75.40
S2
71.34
S2
77.00
S3
73.25
S3
78.85
S4
67.79
S4
72.00
S5
70.25
S5
77.76
SUMMER
Fig. 1 Graphical Representation Of WQI
The water quality indices that were found in three different
seasons have been tabulated in Table III. Table I represents
calculation of Water Quality Index (WQI) of upstream
location S2 (NPP intake) in summer season which is 77. Water
Quality Index of all five sampling locations were calculated
for both season, winter and summer which is shown in Table
III, For better understanding of the variation, the result was
also represented graphically in Figure 1.
Also, Table II explains water quality classification based on
WQI criteria, which in turn, indicates that Water Quality Index
(WQI) of all sampling locations is within category of good
water (50-100) in both season.
From the comparative analysis of WQI values for all
sampling location in both summer and winter season, it was
observed that WQI values for upstream location S1 varied
from 72.82 in winter to 75.40 in summer season. In upstream
location S2, it varied by 71.34 in winter to 77 in summer
season. At NPP discharge location S3, WQI varied from 73.25
to 78.85. For downstream location S4 and S5, it varied from
67.79 and 70.25 in winter to 72 and 77.76 summer season
respectively.
Hence, it can be seen that water quality of lake system
around NPP deteriorates slightly from winter season to
summer season. This could be due to the fact that the
microbial activity get reduced due to low temperature, thereby
keeping DO level at a very satisfactory range during entire
winter season. Also during summer, the water quality
deteriorates on account of the increase in microbial activity as
well as increase in pollutants concentration due water
evaporation.
IV. CONCLUSION
At the outset, the study clearly indicates that the lake water
can be used for public consumption without any treatment.
From the WQI values obtained during the study, there seems
to be no significance change in water quality from upstream
location to downstream location, which in turn, reveals that
lake water is of good quality (WQI – 50 to 100). Further, the
seasonal values of WQI indicate that during summer season,
lake water is more affected than during winter. This could be
due to the fact that the microbial activity get reduced due to
low temperature, thereby keeping DO level at a very
satisfactory range during entire winter season. Also during
summer, the water quality deteriorated on account of the
increase in microbial activity as well as increase in pollutants
concentration due water evaporation.
Application of Water Quality Index (WQI) in this study has
been found useful in assessing the overall quality of water and
to get ride of judgment on quality of the water. This method
appears to be more systematic and gives comparative
evaluation of the water quality of sampling stations. It is also
helpful for public to understand the quality of water as well as
being a useful tool in many ways in the field of water quality
management.
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Bhaven N. Tandel, B.E. (Civil Engineering) 1996, M.E. (Environmental
Engineering) 1998. Both Under Graduation and Post Graduation degrees
from S.V. Regional College of Engineering & Technology, Surat, Gujarat,
INDIA affiliated to South Gujarat University, Surat, Gujarat, INDIA.