The document discusses the estimation of dissolved oxygen (DO), biological oxygen demand (BOD), and chemical oxygen demand (COD) in a canal water sample. DO was found to be 3.20 ppm, BOD was 54.24 ppm, and COD was 220 ppm in the sample. BOD measures the amount of oxygen consumed by microorganisms to break down organic matter over 5 days. COD uses a strong chemical oxidant to measure total organic compounds and some inorganic compounds. While related, BOD and COD measure oxygen demand slightly differently. BOD is more relevant for organic-rich waters, while COD provides a faster test that is not affected by toxins.

1. ESTIMATION OF DO, BOD AND
COD IN CANAL WATER SAMPLE
SUBMITTED BY: SADIA RAHAT

2. ESTIMATIONOFDO,BODANDCODINCANALWATERSAMPLE
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TABLE OF CONTENTS
DISSOLVED OXYGEN (DO) ...................................................................................................... 2
EXAMPLES .............................................................................................................................. 2
CALCULATIONS....................................................................................................................... 5
RESULTS.................................................................................................................................. 6
ENVIRONMENTAL IMPACTS OF DISSOLVED OXYGEN (DO) ................................................... 6
ENVIRONMENTAL SIGNIFICANCE OF DISSOLVED OXYGEN (DO)........................................... 7
BIOLOGICAL OXYGEN DEMAND (BOD) .................................................................................. 7
QUANTIFICATION OF BOD ..................................................................................................... 8
APPLICATION OF BOD TEST.................................................................................................... 8
CHEMICAL OXYGEN DEMAND (COD)..................................................................................... 9
APPLICATION OF COD TEST.................................................................................................... 9
RELATION BETWEEN BOD AND COD...................................................................................... 9
COMPARISION OF BOD AND COD........................................................................................ 10
BIBLIOGRAPHY ..................................................................................................................... 12

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DISSOLVED OXYGEN (DO)
Dissolved oxygen refers to the level of free, non-compound oxygen present in
water or other liquids. It is an important parameter in assessing water quality because
of its influence on the organisms living within a body of water. A small amount of
oxygen, up to about ten molecules of oxygen per million molecules of water, is
actually dissolved in water. This dissolve oxygen is breathed by fish and zooplankton
and is needed by them to survive. In addition to oxygen, carbon dioxide, hydrogen
sulfide and nitrogen are examples of gases that dissolve in water. But dissolve oxygen
in water is most important among all of them as it is not only required by most of the
aquatic organisms but also an important indicator of water quality (Spellman, 2008).
Dissolved oxygen enters water through the air or as a plant byproduct. From
the air, oxygen can slowly diffuse across the water’s surface from the surrounding
atmosphere, or be mixed in quickly through aeration, whether natural or man-made.
The aeration of water can be caused by wind, rapids, waterfalls, ground water
discharge or other forms of running water. Man-made causes of aeration vary from an
aquarium air pump to a hand-turned waterwheel to a large dam.Dissolved oxygen is
also produced as a waste product of photosynthesis from phytoplankton, algae,
seaweed and other aquatic plants.
Dissolved oxygen is usually reported in milligrams per liter (mg/L) or as a
percent of air saturation. However, some studies will report DO in parts per million
(ppm) or in micromoles (umol). 1 mg/L is equal to 1 ppm.
EXAMPLES
FRESHWATER ORGANISMS AND DISSOLVED OXYGEN
REQUIREMENTS
Coldwater fish like trout and salmon are most affected by low
dissolved oxygen levels. The mean DO level for adult salmonids is 6.5
mg/L, and the minimum is 4 mg/L. These fish generally attempt to
avoid areas where dissolved oxygen is less than 5 mg/L and will begin
to die if exposed to DO levels less than 3 mg/L for more than a couple
days. For salmon and trout eggs, dissolved oxygen levels below 11
mg/L will delay their hatching, and below 8 mg/L will impair their
growth and lower their survival rates. When dissolved oxygen falls
below 6 mg/L (considered normal for most other fish), the vast
majority of trout and salmon eggs will die (Kramer, 1987).

4. ESTIMATIONOFDO,BODANDCODINCANALWATERSAMPLE
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PERMISSIBLE STANDARDS FOR COD, BOD
JAMAICA NATIONAL AMBIENT WATER QUALITY STANDARD,
MARINE WATER-BOD
BOD 0.1-1.16 mg/L
(Jamaica National Ambient Water Quality Standard, 2009)
WHO STANDARD- COD
Dams 10 mg/L
(WHO standard, 2004)
PAKISTAN, NATIONAL ENVIRONMENTAL QUALITY STANDARD- 1997
INDUSTRIAL EFFLUENTS-BOD
Into Sea 80mg/L
Into In-land Water 80mg/L
Into Sewage Treatment 250mg/L
(PAKISTAN, NATIONAL ENVIRONMENTAL QUALITY STANDARD, 1997)
PAKISTAN, NATIONAL ENVIRONMENTAL QUALITY STANDARD- 1997
INDUSTRIAL EFFLUENTS-COD
Into Sea 150mg/l
Into In-land Water 150mg/L
Into Sewage Treatment 400mg/L
(PAKISTAN, NATIONAL ENVIRONMENTAL QUALITY STANDARD, 1997)

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PROCEDURE
DO ANALYSIS
We have carefully took representative sample of canal water and pour it into
glass beaker. Then we checked it’s DO at room temperature and recorded it.
BOD ANALYSIS
We aerate our water sample through blowing of the sample for half an hour
through artificial aeration. Then we checked its DO after fifteen minutes so that
all the oxygen may get stabilized. This will be DO1 of the sample. Pour the sample
in BOD bottle and place it in incubator at 20-25oC for five days. After five days,
take out the sample and check DO gain. This will be DO2 of sample. BOD will be
determined by following equation:
BOD = DO1 – DO2
COD ANALYSIS
We carefully took the beaker and add 50ml canal water sample, 5ml conc. H2SO4,
1g HgSO4 and 25ml 0.25M K2Cr2O7 in it. Then we mixed it. To make blank, take
another beaker and add 50ml distilled water, 5ml conc. H2SO4, 1g HgSO4 and
25ml 0.25M K2CR2O7 in it. Then we mixed. Pour sample solution and blank in
two separate flasks attached condenser. Attach both flasks to COD condenser.
Turn on the condenser and reflux the sample and blank for 2 hours. After
required time, take out the sample and blank and cool them in beaker. After
cooling, add 8-9 drops of ferroin indicator in both beakers. Titrate sample and
blank against standard Mohr’s salt solution. The end point will be blue to red.
To calculate COD following formula will be used:
(A – B) x N x 8 x 1000
V

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CALCULATIONS
Where;
A = volume of Mohr’s salt used for blank (ml)
B = volume of Mohr’s salt used for sample (ml)
N = normality of Mohr’s salt
V = volume of sample taken
DISSOLVED OXYGEN
DO = 3.20ppm at 26.4oC
BIOLOGICAL OXYGEN DEMAND
DO1 = 3.84ppm
DO2 = 2.05
BOD = (DO1 –DO2) /Sample Fraction (Sample Size/ BOD Measuring Bottle)
BOD = (3.84 –2.05) / (10ml/300) = 1.79/0.033
BOD = 54.24 ppm
CHEMICAL OXYGEN DEMAND
Sr.
no.
Initial volume-I
(ml)
Final volume-F
(ml)
Volume of
Mohr’s salt
used to titrate
blank-
F - I
(ml)
Average
volume used
(ml)
1 0 5.2 5.2 5.3
2 5.2 10.6 5.4
Sr.
no.
Initial volume (ml) Final volume
(ml)
Volume of
Mohr’s salt
Average
volume used

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used to titrate
sample (F - I)
(ml)
(ml)
1 0 4.1 4.1 4.2
2 4.1 8.4 4.3
A = 5.3ml
B = 4.2ml
N = 0.25 N
V = 10ml
COD = (5.3 – 4.2) x 0.25 x 8 x 1000
10
COD = 220 mg/L
RESULTS
The amount of dissolved oxygen, BOD and COD in canal water is 3.20ppm, 54.24ppm
and 220ppm respectively.
ENVIRONMENTAL IMPACTS OF DISSOLVED OXYGEN (DO)
 If dissolved oxygen concentrations drop below a certain level, fish mortality rates
will rise. Sensitive freshwater fish like salmon can’t even reproduce at levels below
6 mg/L.
 In the ocean, coastal fish begin to avoid areas where DO is below 3.7 mg/L, with
specific species abandoning an area completely when levels fall below 3.5 mg/L.
Below 2.0 mg/L, invertebrates also leave and below 1 mg/L even benthic
organisms show reduced growth and survival rates (Matos et al, 2014).
 A winterkill is a fish kill caused by prolonged reduction in dissolved oxygen due to
ice or snow cover on a lake or pond (Kramer, 1987).

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 Winterkills occur when respiration from fish, plants and other organisms is greater
than the oxygen production by photosynthesis. They occur when the water is
covered by ice, and so cannot receive oxygen by diffusion from the atmosphere.
ENVIRONMENTAL SIGNIFICANCE OF DISSOLVED OXYGEN (DO)
 Dissolve oxygen can be important to the sustainability of a particular ecosystem.
The level of oxygen is a much more important measure of water quality than any
other water quality measure (Spellman, 2008).
 Dissolved oxygen is absolutely essential for the survival of all aquatic organisms
(not only fish but also invertebrates such as crabs, clams, zooplankton, etc.).
 Moreover, oxygen affects a vast number of other water indicators, not only
biochemical but esthetic ones like the odor, clarity and taste. Consequently,
oxygen is perhaps the most well-established indicator of water quality (METCALF
and EDDY, 2003).
BIOLOGICAL OXYGEN DEMAND (BOD)
Biochemical oxygen demand is an important example of water pollutants
that degrade biochemically and affect water quality according to the location as well
as the strength of the discharge. Therefore, it is important to examine carefully the
potential water quality impacts of a program of transferable discharge permits
(TDP's) to regulate these discharges prior to the implementation of such a program
(Jr et al., 1984).
Biological Oxygen Demand (BOD) is one of the most common measures of
pollutant organic material in water. BOD indicates the amount of putrescible organic
matter present in water. Therefore, a low BOD is an indicator of good quality water,
while a high BOD indicates polluted water. Dissolved oxygen (DO) is consumed by
bacteria when large amounts of organic matter from sewage or other discharges are
present in the water. DO is the actual amount of oxygen available in dissolved form
in the water. When the DO drops below a certain level, the life forms in that water
are unable to continue at a normal rate. The decrease in the oxygen supply in the
water has a negative effect on the fish and other aquatic life (Connor, 1980). Fish
kills and an invasion and growth of certain types of weeds can cause dramatic
changes in a stream or other body of water. Energy is derived from the oxidation
process. BOD specifies the strength of sewage. In sewage treatment, to say that the
BOD has been reduced from 500 to 50 indicates that there has been a 90 percent
reduction (Robson, 2002).

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QUANTIFICATION OF BOD
For the quantification of BOD, the analysis was made after the sample
incubation for 5 days at 20 °C, obtaining BOD. The long time required for the analysis
is precisely one of the main limitations to its use in studies or in monitoring that
requires quick responses, so that it is possible to act with environmental impacts or
operation of biological treatment systems. The rise in temperature favors higher
multiplication and faster metabolism of microorganisms as well as increased
availability of organic material by increasing the hydrolysis of the organic
compounds (METCALF & EDDY, 2003). Thus, the increase in temperature, since
within the optimum range for the development of mesophilic microorganisms,
which is of 30-35 °C, may, provide an increase in the rate of oxygen depletion,
allowing more rapid degradation of the organic material. The increase in BOD
progression of exercise provided by the temperature rise can be verified by the
increase in de-oxygenation process, which is dependent on the concentration of
biodegradable organic matter and temperature, and indicates the consumption of
DO over time besides the speed that reaches the last biochemical oxygen demand
(Matos et al., 2014).
APPLICATION OF BOD TEST
The BOD test serves an important function in stream pollution-control activities.
It is a bioassay procedure that measures the amount of oxygen consumed by living
organisms while they are utilizing the organic matter present in waste, under
conditions similar in nature. The other traditional tests or indicators for water
quality are chemical oxygen demand (COD) and pH. For results of the BOD test to be
accurate, much care must be taken in the actual process. For example, additional air
cannot be introduced. Temperature must be 20°C, which is the usual temperature of
bodies of water in nature (Robson, 2002). A five-day BOD test is used in
environmental monitoring. This test is utilized as a means of stating what level of
contamination from pollutants is entering a body of water. In other words, this test
measures the oxygen requirements of the bacteria and other organisms as they feed
upon and bring about the decomposition of organic matter. Time and temperature,
as well as plant life in the water, will have an effect on the test (Jr et al, 1984). High
BOD burdens or loads are added to wastewater by food processing plants, dairy
plants, canneries, distilleries and similar operations, and they are discharged into
streams and other bodies of water.

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CHEMICAL OXYGEN DEMAND (COD)
Chemical oxygen demand (COD) is a measure of the capacity of water to
consume oxygen during the decomposition of organic matter and the oxidation of
inorganic chemicals such as ammonia and nitrite. COD measurements are commonly
made on samples of waste waters or of natural waters contaminated by domestic or
industrial wastes.
The Chemical Oxygen Demand (COD) test uses a strong chemical oxidant in
an acid solution and heat to oxidize organic carbon to CO2 and H2O. By definition,
chemical oxygen demand is
“A measure of the oxygen equivalent of the organic matter content of a sample that
is susceptible to oxidation by a strong chemical oxidant.”
APPLICATION OF COD TEST
Oxygen demand is determined by measuring the amount of oxidant
consumed using titrimetric or photometric methods. The test is not adversely
affected by toxic substances, and test data is available in 1-1/2 to 3 hours, providing
faster water quality assessment and process control (Boyles, 1997).
COD test results can also be used to estimate the BOD results on a given
sample. An empirical relationship exists between BOD, COD and TOC. However, the
specific relationship must be established for each sample. Once correlation has been
established, the test is use fulL for monitoring and control (Boyles, 1997).
Chemical oxygen demand is measured as a standardized laboratory assay in
which a closed water sample is incubated with a strong chemical oxidant under
specific conditions of temperature and for a particular period of time. A commonly
used oxidant in COD assays is potassium dichromate (K2Cr2O7) which is used in
combination with boiling sulfuric acid (H2SO4). Because this chemical oxidant is not
specific to oxygen-consuming chemicals that are organic or inorganic, both of these
sources of oxygen demand are measured in a COD assay.
RELATION BETWEEN BOD AND COD
Chemical oxygen demand is related to biochemical oxygen demand (BOD),
another standard test for analyzing the oxygen-demanding strength of waste waters.
However, biochemical oxygen demand only measures the amount of oxygen

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consumed by microbial oxidation and is most relevant to waters rich in organic
matter. It is important to understand that COD and BOD do not necessarily measure
the same types of oxygen consumption. For example, COD does not measure the
oxygen-consuming potential associated with certain dissolved organic compounds
such as acetate. However, acetate can be metabolized by microorganisms and would
therefore be detected in test of BOD. In contrast, the oxygen-consuming potential of
cellulose is not measured during a short-term BOD test, but it is measured during a
COD test (Boyles, 1997).
COMPARISION OF BOD AND COD
TABLE 1 showsthe comparisonbetweenBODtestandCod Test.

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(Boyles, 1997)

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BIBLIOGRAPHY
1. Spellman, F.R. (Nov, 2008). Handbook of Water and Wastewater Treatment
Plant Operations (2nded.). Florida: CRC Press
2. Kramer, D.L. (February 1987). Dissolved oxygen and fish behavior.
Environmental Biology of Fishes. 2(18). 81-92
3. Robson, M. G., (2002). Biological Oxygen Demand. Encyclopedia of Public
Health.1-1
4. Jr. E.D.B.,Eheart, J.W., Kshirsagar, S.R. and Lence B. J. (April, 1984). Water
Quality Impacts of Biochemical Oxygen Demand under Transferable
Discharge Permit Programs. AGU Publications. 4(20). 445-446
5. Connor, R. O. (March, 1980).Biological oxygen demand. Journal of Chemical
Education 57(3)807-808
6. APHA. 1992. Standard methods for the examination of water and
wastewater. (18th ed.). American Public Health Association: Washington, DC.
7. USEPA. 1983. Methods for chemical analysis of water and wastes (2nd ed).
Method 365.2. U.S. Environmental Protection Agency: Washington DC.
8. Matos, M. P. D., Borges, A. C., Matos, A. T. D., Silva, E. F. d. and Martinez, M.
A. (2014). Effect of time-temperature binomial in obtaining biochemical
oxygen demand of different wastewaters. EngenhariaAgrícola, 34(2), 332-
340.
9. METCALF and EDDY. (2003). Wastewater engineering: treatment disposal
and reuse (4th ed.). New York: McGraw-Hill.

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10. Boyles, W. (1997).The Science ofCHEMICAL OXYGEN DEMAND: Technical
Information Series. (9THed.).USA: Hach Company.