Comparative Study of Eutrophication of Two Urban Ponds and Suggestive Restoration Measures
Alpana Saha
Sub-Editor (DBT Communication Cell)
Vigyan Prasar, C-24, Qutub Institutional Area, New Delhi
Abstract
Water pollution means when physical, chemical and/or
biological characteristics or quality of water body becomes harmful to human
for domestic needs or aquatic life or to a balanced functioning of the water
ecosystem.
When sewage and organic wastes are broken down,
inorganic nutrients enrich the water in the water body. The problem of
excessive nutrient load in water bodies is called eutrophication.
To know about pollution and eutrophication level of
inland stagnant water bodies in India in my
study I have taken the comparative study of two ponds of Bhagalpur .
The names of the two ponds are Mukhra pond and Lalbagh pond respectively.
In eutrophic water body constant decomposition of
blooms, lead to oxygen depletion in water. Thus, in poorly oxygenated water
with higher CO2 level where fishes and other animals begin to die
and clean water body is turned into a stinking water body. Many pathogenic
microorganisms begin to grow on products of nutrients rich water body under
anaerobic conditions.
In comparative study of Eutrophication of Two Ponds of
Bhagalpur were selected. One of the pond name Mukhra is perennial fresh water
pond and the other one that is the Lalbagh pond is more or less seasonal
freshwater pond.
The water samples were collected from February 2013 to
July 2013.
The periodic fluctuations in physical chemical
properties of the ponds water and its inter-relationship with human activities
on the eutrophication of the system are illustratively studied. The chemical
reading indisputably indicate the two ponds are marching towards
hyper-eutrophication.
It is primarily
suggested that the performance of sewage system at the close vicinity of the
water body should be regularly monitored and the environmentalist and other
governing body should have regular check on the water system.
Keywords: blooms, body, eutrophication, inland, pond,
system
Introduction
Water pollution can be implied as follows: “if
physical, chemical and/or biological characteristics or quality of water body
becomes harmful to human for domestic needs or aquatic life or to a balanced
functioning of the freshwater ecosystem. Such a situation is referred to as
freshwater pollution” Varshney CK (1981).
When sewage and organic wastes are broken down,
inorganic nutrients enrich the water in the water body. This nutrient load
greatly increases the productivity of the water and an algal bloom occurs in
such water bodies. In such situation, the water body appears green. This
problem of excessive nutrient load in water bodies is called eutrophication. It
has because a serious problem for many inland water bodies in India .
To know about pollution and eutrophication level of
inland stagnant water bodies in India in my
study I have taken the comparative study of two ponds of Bhagalpur .
The names of the two ponds are Mukhra pond and Lalbagh pond respectively.
Materials and
Methods
In comparative study of Eutrophication, two ponds of Bhagalpur were selected. One of the pond name Mukhra is
perennial fresh water pond and the other one that is the Lalbagh pond is more
or less seasonal freshwater pond.
The water samples were collected from February 2013 to
July 2013.
Physical and Chemical analysis of water
Water samples from fixed spots were collected between
8:30 and 11:00 hours and preserved for the estimation of different chemical
constituents. Analyses of water temperature, dissolved O2, free CO2,
CO3, HCO3 and alkalinity were done at the spot immediately
after collection of the samples.
Following standard methods were used for the analysis
of various physical and chemical variables.
Temperature
Atmospheric as well as surface water temperature was
measured with the help of mercury thermometer of graduated upto 110ºC.
Transparency
Transparency of the pond water was measured lay secchi
disc which is circular disc of metal 20 cm in diameter painted with black and
white colour and is fixed to a rope. It was lowered into water until
disappeared from sight and then raised slowly until it was just visible again.
Secchi disc transparency = A+B/2; where A = depth at which secchi disappear, B
= depth at which secchi disc reappear.
Hydrogen ion concentration (pH)
The pH was determined by the use of pH test paper with
a range of 1 to 10. The pH paper strip was dipped into the water sample and the
colour appeared was compared with the standard colour available with the pH
paper.
Dissolved O2
Dissolved O2 was measured by modified
Winkler’s method. In this method, 250 ml pond water and 2 ml of SO4 solution
was taken in another conical flask and few drops of starch indicator was mixed with,
as a result sample solution become light blue in colour. This sample solution
was nitrated against 4/40 Na2S2O3 (Solution
Thiosulphate) solution, which was kept in burette till the colour of sample
water just appear this difference of initial and final reading gave value of
dissolved O2, which was measured in ppm.
Free Carbon dioxide
Free CO2 was estimated in ppm by the method
described by Welch. In this method, 100 ml of sample water was nitrated against
N/44 sodium hydroxide solution using phenolphthalein as indicator and the value
was multiplied by 10.
Carbonate Alkalinity (CO3)
It was measured in ppm by the method given by Welch.
In this method, 100 ml sample water was titrated against N/50 sulphuric acid
using phenolphthalein as an indicator and the value was multiplied by 10.
Bicarbonate Alkalinity (HCO3)
It was estimated in ppm by the method described by
Welch. In this process, 100 ml of sample water was titrated against n/50
sulphuric acid. Methyl range was used as indicator and the titrant value was
multiplied by 10.
Chloride (Cl)
Chloride was analyzed by titrating 50 ml sample water,
0.014/N silver nitrate solution, using potassium chromate as indicator. The
titrant value was multiplied by 39.57 total the amount of chloride in ppm. This
is the Argento metric method.
Total Hardness (TH)
It was determined according to the method given in
APHA. In which 50 ml of sample water was titrated against N/50 EDTA (ethylene
dinitro tetra acetic acid) solution using total hardness table indicator and
ammonia buffer as reagent. NaOH (N) solution of 0.5 ml volume was also
sometimes used to raise the pH of the sample solution the titrant value was
multiplied by 20 to get the total hardness value in ppm.
Calcium Hardness
Calcium hardness was determined or measured in ppm
according to APHA. EDTA titration method was adopted using calcium hardness table
as indicator and sodium hydroxide (4N) solution as reagent.
Nitrate – Nitrogen – (NO3-N)
Phenol disulphonic acid method was used for nitrate
estimation proper care was taken for chloride removal. Water sample of 25 ml
volume was corporate to dryness in an evaporating dish over a hot water bath.
The residue was mixed thoroughly with 2 ml of phenol disuphonic acid reagent.
To ensure dissolution of solids and then diluted with 20 ml of distilled water.
The whole solution was then transferred to a 100 ml volumetric flask. After
cooling to room temperature, 6-7 ml of ammonia solution was added carefully.
Then mark with distilled water. The colour developed was measured at a
wavelength of 410 m against a reference blank. The nitrate content was then
calculated from the standard curve.
Phosphate
Addition of phosphorus contributes to rapid
eutrophication.
Filtered sample water of 50 ml transferred into a 125
ml volumetric flask and 2 ml of ammonium molybdate suphuric acid solution
followed by 0.5 ml or 10 drops of stannous chloride solution. The solution was
mixed properly and allowed to stand for 10 minutes. The
colour developed was measured at a wavelength of 660 mm using appropriate
reference black. The amount of phosphate was calculated from the standard
curve.
Observations
The observations of six month of the two ponds are
listed in the Table 1 and Table 2. Table 1 contains the physical chemical
characteristics of Mukhra Pond and Table 2 contains the physical and chemical
characteristics of Lalbagh Pond.
Table 1: Physico-chemical Characteristics of Mukhra
Pond – 2013
Months
|
February
|
March
|
April
|
May
|
June
|
July
|
Parameter
|
||||||
Water temperature
|
24°C
|
24°C
|
32°C
|
26°C
|
23°C
|
30°C
|
pH
|
7
|
8
|
8
|
8
|
8
|
8
|
D.O2 (ppm)
|
4.8
|
8
|
9.2
|
9
|
9
|
12.8
|
TDS (mg/l)
|
330.6
|
265.4
|
224.2
|
274.2
|
340.4
|
363.8
|
F. CO2
|
-
|
-
|
40
|
-
|
-
|
84
|
CO3 (ppm)
|
76
|
10
|
-
|
12
|
76
|
-
|
HCO3(ppm)
|
90
|
200
|
264
|
220
|
194
|
160
|
Calcium hardness (ppm)
|
140
|
164
|
130
|
170
|
146
|
90
|
Total hardness (ppm)
|
260
|
190
|
250
|
200
|
240
|
124
|
Chloride (ppm)
|
472
|
530
|
324
|
550
|
580
|
520
|
PO4-P (ppm)
|
0.20
|
0.26
|
0.37
|
0.28
|
0.09
|
0.28
|
NO3-N (ppm)
|
0.19
|
0.18
|
0.10
|
0.19
|
0.14
|
0.37
|
Table 2: Physico-chemical Characteristics of Lalbagh
Pond – 2013
Months
|
February
|
March
|
April
|
May
|
June
|
July
|
Parameter
|
||||||
Water temperature
|
22°C
|
25°C
|
31°C
|
24°C
|
22°C
|
28°C
|
pH
|
7
|
8
|
7
|
8
|
8
|
8
|
D.O2 (ppm)
|
4.6
|
3.6
|
4
|
3.8
|
8
|
10
|
TDS (mg/l)
|
255.5
|
344.8
|
196.5
|
209.4
|
244.4
|
304.2
|
F. CO2
|
-
|
40
|
20
|
24
|
-
|
8
|
CO3 (ppm)
|
78
|
-
|
-
|
-
|
68
|
-
|
HCO3(ppm)
|
88
|
110
|
102
|
360
|
220
|
320
|
Calcium hardness (ppm)
|
144
|
156
|
170
|
162
|
160
|
106
|
Total hardness (ppm)
|
368
|
354
|
280
|
260
|
220
|
760
|
Chloride (ppm)
|
460
|
684
|
380
|
370
|
390
|
500
|
PO4-P (ppm)
|
2.60
|
2.73
|
2.91
|
1.90
|
2.08
|
2.91
|
NO3-N (ppm)
|
0.19
|
0.37
|
0.46
|
0.73
|
0.19
|
0.37
|
Discussion and Result
It is essential to evaluate the physical and chemical
characteristics of the water system to know the pollution level or extent of
eutrophication of the pond undertaken in study.
The periodic fluctuations in physical chemical
properties of the ponds water and its inter-relationship and effect of human
activities on the eutrophication of the system are well illustration in the
tables described earlier.
Physical condition
Mukhra Pond: The water temperature varies from 23°C to 32°C. At the same
site air temperature varies from 27°C to 33°C.
Lalbagh Pond: The water temperature varies from 22°C to 31°C during the
six-month span whereas the air temperature at the same spot varied from 26°C to 35°C.
Chemical conditions
pH of Mukhra Pond: In the first month the pH of the
pond was found to be 7, that is, in February 2013. This indicated that water of
Mukhra pond was neutral at that time, which indicated good condition of the
pond. After that, the pH recorded 8. This indicated alkalinity of the water. So
alkaline nutrient content might be present in the water and result the ponds
marches towards eutropication.
The increase in pH also indicates rapid death and
decomposition of flora and fauna present in the Mukhra pond.
pH of Lalbagh pond: The of pond also increased from 7
to 8 which indicated that the water became alkaline.
DO2 of Mukhra Pond: One thing is very
apparent from the reading of dissolved oxygen in the pond. It shows a
progressive increase. Here DO2 increases because number of
photosynthetic organisms increase due to increase eutrophication of the system.
DO2 of Lalbagh Pond: Minimum dissolved
oxygen was recorded in the month of March and maximum in the month of July.
Same scenarios of Mukhra pond exist here. Because of increase in the number of
macrophytes and algal blooms, this indicates progression of the pond towards
eutrophication.
We know that total hardness of any system depends on
the amount of calcium and magnesium salts present in the system. Therefore, the
reading shows moderate hardness in Mukhra pond and very hard water of Lalbagh
pond.
The presence of chloride, phosphate and nitrate in the
two ponds in significant amount indicate that the two ponds are marching
towards hyper-eutrophication.
Conclusion
The periodic physical and chemical reading of the two
ponds clearly indicate that the two ponds are highly eutrophicated. There are
many sources, which cause eutrophication in the water of the two ponds. The
sources are sewage and oxygen demanding wastes, agricultural discharge,
inorganic chemicals, washing chemicals, organic pollutants, disease causing
agents and siltation. If restoration measure is not undertaken for the two
ponds the existence of the two ponds are under threat.
General
Restorative Suggestion
It is primarily
suggested that the performance of sewage system at the close vicinity of the
water body should be regularly monitored. The environmentalist and other
governing body should also have regular check on the look and feel of the water
system. Free oxygen should be made available to dying water body. To restore
aquatic ecosystem in any urban area fish farming and shellfish farming should
be highly encouraged. The growth of algae, cyno-bacteria and excessive
macrophytes should also be monitored. If these are not checked, the water
bodies in the area will die.
References
Varshney CK (1981) Water pollution and management
reviews 1981. South Asia publication, New Delhi; pp: 154.
Welch (1952) Limnology, McGrew Hills, New Delhi.
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