Table of Contents

ABSTRACT...................................................................................................................2

1. INTRODUCTION..................................................................................................3

1.1. Introduction.....................................................................................................3

1.2. Theory..............................................................................................................4

1.3. Objective..........................................................................................................7

2. METHODOLOGY.................................................................................................8

2.1. Apparatus.........................................................................................................8

2.2. Reagent............................................................................................................8

2.3. Procedure.........................................................................................................8

3. RESULTS AND DISCUSSION...........................................................................10

3.1. Result.............................................................................................................10

3.2. Discussion......................................................................................................10

4. CONCLUSION.....................................................................................................13

5. RECOMMENDATION........................................................................................14

REFERENCES.............................................................................................................15

1

ABSTRACT

The air we breathe contains about 20% oxygen. Aquatic organisms require oxygen in

the water as well. The analysis of water consist of analysis of pH, temperature and

Dissolved Oxygen (DO). The term Dissolved Oxygen (DO or D.O.) refers to the

amount of free oxygen dissolved in water which is readily available to respiring

aquatic organisms. State water quality standards often express minimum

concentrations of dissolved oxygen which must be maintained in order to support life

as well as be of beneficial use. This experiment preferred analysis of DO by using

Azide Modification of Winkler Method. Generally, a higher dissolved oxygen level

indicates better water quality. If dissolved oxygen levels are too low, some fish and

other organisms may not be able to survive. It can range from 0-18 parts per million

(ppm), but most natural water systems require 5-6 parts per million to support a

diverse population. When organic matter such as animal waste or improperly treated

wastewater enters a body of water, algae growth increases and the dissolved oxygen

levels decrease as the plant material dies off and decomposed through the action of

the aerobic bacteria. Decreases in the dissolved oxygen levels can cause changes in

the types and numbers of aquatic macroinvertebrates which live in a water ecosystem.

From the wastewater samples, DO in this water is not suitable for the aquatic life

because its too low, 3.98ppm. Some fish and macroinvertebrate populations will begin

to decline.

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1. INTRODUCTION

1.1. Introduction

The air we breathe contains about 20% oxygen. Fish and other aquatic organisms

require oxygen in the water as well. The term Dissolved Oxygen (DO or D.O.) refers

to the amount of free oxygen dissolved in water which is readily available to respiring

aquatic organisms. State water quality standards often express minimum

concentrations of dissolved oxygen which must be maintained in order to support life

as well as be of beneficial use.

The water requirement per unit of body mass of a high-producing dairy is greater

because of the high yield of a secretion that is 87% water. Water also is required for

digestion and metabolism of energy and nutrients, transport in circulation of nutrients

and metabolites to and from tissues, excretion of waste products (via urine, feces, and

respiration), maintenance of proper ion, fluid, and heat balance; and, as a fluid and

cushioning environment for the developing fetus.

Generally, a higher dissolved oxygen level indicates better water quality. If dissolved

oxygen levels are too low, some fish and other organisms may not be able to survive.

It can range from 0-18 parts per million (ppm), but most natural water systems require

5-6 parts per million to support a diverse population. When organic matter such as

animal waste or improperly treated wastewater enters a body of water, algae growth

increases and the dissolved oxygen levels decrease as the plant material dies off and

decomposed through the action of the aerobic bacteria. Decreases in the dissolved

oxygen levels can cause changes in the types and numbers of aquatic

macroinvertebrates which live in a water ecosystem.

Additionally, biochemical oxygen demand (BOD) is commonly use with reference to

effluent discharges and is a common, environmental procedure for determining the

extent to which oxygen within a sample can support microbial life. The test for BOD

is especially important in wastewater treatment, food manufacturing, and filtration

facilities where the concentration is crucial to the overall process and end products.

High concentrations of DO predict that oxygen uptake by microorganisms is low

along with the required break down of nutrient sources in the medium.

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Liquid and air state of equilibrium is reached when the partial pressure of oxygen,

example the part of the total pressure that is due to oxygen, is equal in air and in

liquid. Then, liquid is saturated with oxygen.

     

Figure 1: Air and liquid oxygen in equilibrium

Much of the dissolved oxygen in water comes from oxygen in the air that has

dissolved in the water. Some of the dissolved oxygen in the water is a result of

photosynthesis of aquatic plants. Other factors also affect DO levels such as on sunny

days high DO levels occur in areas of dense algae or plants due to photosynthesis.

Stream turbulence may also increase DO levels because air is trapped under rapidly

moving water and the oxygen from the air will dissolve in the water.

In addition, the amount of oxygen that can dissolve in water (DO) depends on

temperature. Colder water can hold more oxygen in it than warmer water. A

difference in DO levels may be detected at the test site if tested early in the morning

when the water is cool and then later in the afternoon on a sunny day when the water

temperature has risen. A difference in DO levels may also be seen between winter

water temperatures and summer water temperatures. Similarly, a difference in DO

levels may be apparent at different depths of the water if there is a significant change

in water temperature

1.2. Theory

The measurement of dissolved oxygen is a convenient method of measuring

production and decomposition in bodies of water. The AZIDE modifications of

Winkler method are introduced for the determination DO in the water. The

modification involve the addition of sulphuric acid and sodium azide as preserving

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agents rather than the precipitation of manganese hydroxides in the field, gives more

accurate results when samples have to be stored before completion of the

determination. The Winkler method was devised and modified by the Hungarian

scientist Lajos Winkler. He was recognized the importance of dissolved oxygen in

aquatic life and developed a simple oxidation-reduction reaction routinely performed

by aquatic biologists. The relatively new oxygen-sensitive electrodes facilitate

continuous measurement and broadened our knowledge in all aquatic ecosystems.

The Winkler method involves filling a sample bottle completely with water (no air is

left to bias the test). The dissolved oxygen is then "fixed" using a series of reagents

that form an acid compound that is titrated. Titration involves the drop-by-drop

addition of a reagent that neutralizes the acid compound and causes a change in the

color of the solution. The point at which the color changes is the "endpoint" and is

equivalent to the amount of oxygen dissolved in the sample. The sample is usually

fixed and titrated in the field at the sample site. It is possible, however, to prepare the

sample in the field and deliver it to a lab for titration.

The main problem with most oxygen probes is that the delicate membrane over the

electrode must be replaced frequently. Today the oxygen-sensitive electrode regularly

calibrated with the fundamental Winkler method. Winkler’s student, Rezsõ Maucha

became his partner and together in developed a semi-micro field method to measure

O2 in the late 1920’s. Maucha star diagram is used to visually compare the ionic

composition of bodies of water both qualitatively and quantitatively. Ahead of his

time (before phosphorus was measured in water) he classified the productivity of

Hungarian lakes based on the oxygen produced by algae. He broadened the three

connecting biological activities – production, consumption and decomposition with

the concept of supply and accumulation.

A biological cause of the increase can be discounted because of the high pH of the

fixed sample. The probable cause was therefore diffusion of oxygen through the

exposed rubber liner of the sample bottle. Natural and silicone rubber are known to be

permeable to oxygen. The effect of this may be reduced by the storage of fixed

samples under water, but not entirely eliminated. Samples should therefore not be

stored with the manganese hydroxides precipitated, but rather, where necessary,

preserved it. Similarly, this method is used to measure the primary production of

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water plants and the consumption of aquatic animals or bacteria in sewage waters.

The disadvantage of this method is that the final titration has to be done in the

laboratory because of the necessary equipment. Consequently, when doing field work,

the prepared samples containing MnII(OH)3 have to be transported as fast as possible,

but no longer than within three hours in well closed vessels, to the laboratory for

further work.

DO is measured either in milligrams per liter (mg/L) or "percent saturation."

Milligrams per liter is the amount of oxygen in a liter of water. Percent saturation is

the amount of oxygen in a liter of water relative to the total amount of oxygen that the

water can hold at that temperature.

Table 1

They vary with water temperature and altitude. Cold water holds more oxygen than

warm water (Table 1) and water holds less oxygen at higher altitudes. Thermal

discharges, such as water used to cool machinery in a manufacturing plant or a power

plant, raise the temperature of water and lower its oxygen content. Aquatic animals

6

Temperature(°C)

DO(mg/l)

Temperature(°C)

DO(mg/l)

0 14.60 23 8.56

1 14.19 24 8.40

2 13.81 25 8.24

3 13.44 26 8.09

4 13.09 27 7.95

5 12.75 28 7.81

6 12.43 29 7.67

7 12.12 30 7.54

8 11.83 31 7.41

9 11.55 32 7.28

10 11.27 33 7.16

11 11.01 34 7.16

12 10.76 35 6.93

13 10.52 36 6.82

14 10.29 37 6.71

15 10.07 38 6.61

16 9.85 39 6.51

17 9.65 40 6.41

18 9.45 41 6.41

19 9.26 42 6.22

20 9.07 43 6.13

21 8.90 44 6.04

22 8.72 45 5.95

are most vulnerable to lowered DO levels in the early morning on hot summer days

when stream flows are low, water temperatures are high, and aquatic plants have not

been producing oxygen since sunset.

1.3. Objective

The objective of this experiment to determine the dissolved oxygen (D.O) in the water

system and its important to the aquatic life.

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2. METHODOLOGY

2.1. Apparatus

300-mL BOD bottle, stopper, tube, titration cartridge, cylinder, 250-mL Erlenmeyer

flask,

2.2. Reagent

Manganous Sulfate powder pillow, Alkaline Iodide-Azide Regent powder pillow,

Sulfamic Acid Powder Pillow, sodium thiosulfate, Starch Indicator Solution.

2.3. Procedure

A water sample was collect in a clean 300-mL BOD bottle. The sample allowed to

overflow the bottle for 2-3 minutes to ensure that air bubbles are not trapped. Then,

the contents of one Manganous Sulfate Powder Pillow and one Alkaline Iodide-Azide

Reagent Powder Pillow was added into the bottle. Immediately and without trapping

the air in the bottle, the stopper was insert and mix it by inverting the bottle several

times. Let the solution for about five minutes to form a flocculent precipitate because

it settles slowly in salt water. It will be orange-brown if oxygen is present or white if

oxygen is absent. Then, the bottle was inverted for several times and wait until the

floc settles and the top half of the solution is clear again. Then, the stopper was

removed and the content of the Sulfamic Acid Powder Pillow was added into the

bottle. The stopper was replace without trapping air in the bottle. Then, the samples

was inverted for several times to mix it. The floc will dissolve and a yellow color is

present. A sample volume and Sodium Thiosulfate Titration Cartridge was select from

the table 2 that correspond to the expected DO concentration.

Table 2

Range(mg/L DO)

Sample volume(mL)

Titration Cartridge(N Na2S2O3)

Catalog number

Digital Multiplier

1 – 5 200 0.200 22675-01 0.012 – 10 100 0.200 22675-01 0.02>10 20 2.000 14401-01 0.10

Next, a clean delivery tube was inserted into the titration cartridge to the titrator body.

Then, turn the delivery knob to eject a few drops of titrant. Reset the counter to zero

and wipe the tip. Sample volume that used in this experiment is 100 mL. A graduated

8

cylinder was used to measure the sample volume and transfer it into 250-mL

Erlenmeyer flask. The delivery tube tip was place into the solution and the flask was

swirl while titrating with sodium thiosulfate to a pale yellow color. Then, two 1-mL

droppers of starch indicator solution added and swirl to mix it. The dark blue color

will develop. The titration continued to a colorless endpoint and the number of digital

required was recorded.

Figure 2: titrating DO

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3. RESULTS AND DISCUSSION

3.1. Result

From the experiment, digital number that determine is 199. Therefore the Dissolved

Oxygen (D.O) in mg/L is 3.98 mg/ L that equal with 3.98 ppm.

DO (mg/L) = digits required x digit multiplier

= 199 x 0.02

= 3.98 mg/L

= 3.98 ppm

3.2. Discussion

From the results, it shows that DO in the sample water is 3.98 ppm. Based on the table

3, the water is poor, some fish and macro invertebrate populations will begin to

decline

Table 3: DO level and its analysis

DO Level (in ppm) Water Quality

0.0 - 4.0 Poor

Some fish and macro invertebrate populations will begin to decline

4.1 - 7.9 Fair

8.0 - 12.0 Good

12.0 + Retest

Water maybe artificially aerated.

At levels of 4 ppm or less, some fish and macro invertebrate populations (examples:

bass, trout, salmon, mayfly nymphs, stonefly nymphs, caddisfly larvae) will begin to

decline. Other organisms are more capable of surviving in water with low dissolved

oxygen levels (examples: sludge worms, leeches).

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Low dissolved oxygen levels usually result from algal blooms, human waste and

animal waste. Low DO levels may be found in areas where organic material which is

dead plant and animal matter is decaying. Bacteria require oxygen to decompose

organic waste, thus, deplete the water of oxygen. Areas near sewage discharges

sometimes have low DO levels due to this effect. DO levels will also be low in warm,

slow moving waters.

At room temperature, 20o C and standard atmospheric pressure at sea level, the

maximum amount of oxygen that can dissolve in fresh water is 9 ppm. If the water

temperature is below 20º C, there may be more oxygen dissolved in the sample. In

general, a dissolved oxygen level of 9-10 ppm is considered very good.

There are a variety of factors that can increase the level of dissolved oxygen in water.

Dissolved oxygen naturally enters the water from the atmosphere and will continue to

enter the water until it becomes saturated. When aquatic plants and algae are exposed

to sunlight they produce oxygen as a waste product of photosynthesis. The structure

of a stream or river affects dissolved oxygen. The more turbulence that a stream or

river displays, such as waterfalls or rapids, the more oxygen is absorbed into the

water. Also, turbulence on the surface of a body of water caused by wind tends to

increase levels of dissolved oxygen. Artificial aeration such as with an aquarium

bubble stone will increase DO levels, sometimes dramatically.

However, there are some processes that reduce dissolved oxygen levels in water. All

living organisms must respire to survive. Animals such as fish, crustaceans, mollusks,

and worms that live in water remove oxygen from the water for respiration. Plants and

algae also need oxygen to respire at night or on cloudy days. As the amount of dead

organic material increases in water more oxygen is used by bacteria to decompose

that material. These organic wastes can come from agricultural runoff, industrial

wastes, or sewage treatment plants. Chemical pollution can also reduce DO levels due

to chemical reactions with dissolved oxygen. Nitrates, ammonia, sulfates, and other

ions reduce levels of dissolved oxygen when they enter bodies of water.

Two weather factors, temperature and barometric pressure, can also affect levels of

dissolved oxygen. As temperature increases, water tends to hold less dissolved

oxygen, so dissolved oxygen levels in water tend to decrease when it is warmer. And

when it is cooler dissolved oxygen levels tend to increase. Also, as barometric

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pressure increases, the solubility of oxygen increases, so levels of dissolved oxygen

tend to increase.

Some aquatic organisms are more sensitive to low levels of dissolved oxygen than

others. Trout, striped bass, perch, and shad are fish that require 5 to 6 ppm of

dissolved oxygen to survive. While trout are spawning, dissolved oxygen should not

be below 7.0 ppm. If dissolved oxygen falls below 4.0 ppm some fish and invertebrate

populations such as insects and crustaceans will begin to decline. When DO levels are

between 3.0 and 4.0 ppm, fish will come to the surface to begin piping. Piping is the

gulping or gasping for air that fish do when they come to the surface for air. Some

crustaceans such as crabs and crayfish can survive in waters with dissolved oxygen as

low as 3.0 ppm. Organisms commonly associated with poor water quality such as

leeches, sludge worms and other types of worms can live in water with low dissolved

oxygen levels.

During this experiment, make sure that the stopper was inserted immediately to avoid

air trap. After the sample was added with the chemicals, swirl it to ensure complete

reaction of the samples and reagent.

Sodium thiosulfate is used in this experiment to neutralize the chlorine. This is

because, Chlorine can also affect BOD measurement by inhibiting or killing the

microorganisms that decompose the organic and inorganic matter in a sample.

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4. CONCLUSION

Biochemical oxygen demand, or BOD, measures the amount of oxygen consumed by

microorganisms in decomposing organic matter in stream water. BOD also measures

the chemical oxidation of inorganic matter like the extraction of oxygen from water

via chemical reaction. A test is used to measure the amount of oxygen consumed by

using Azide Modification of Winkler Method.

BOD directly affects the amount of dissolved oxygen in rivers and streams. The

greater the BOD, the more rapidly oxygen is depleted in the stream. This means less

oxygen is available to higher forms of aquatic life. The consequences of high BOD

are the same as those for low dissolved oxygen, aquatic organisms become stressed,

suffocate, and die.

Sources of BOD include leaves and woody debris; dead plants and animals; animal

manure; effluents from pulp and paper mills, wastewater treatment plants, feedlots,

and food-processing plants; failing septic systems; and urban stormwater runoff.

It can be concluded that the water samples is poor. It means some fish and macro

invertebrate populations will begin to decline at a rate 3.98 ppm.

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5. RECOMMENDATION

In this experiment, the water samples that selected came from wastewater. It is not

suitable for aquatic life because the DO level is too low which is 3.98ppm. It

recommended to used the water from lake or river. Therefore, the results that get will

give higher value for DO, then the comparison between both water samples can be

analyzed.

Besides that, the analysis of water can be changed by using EPT Testing. It used

macroinvertebrates as quality indicators is that they provide evidence of water quality

over a long stretch of time. While temperature, pH and DO can fluctuate day to day

and even hour to hour. Macroinvertebrates show long-term trends in water quality.

The presence of a mixed population of macroinvertebrates indicates that water quality

has been suitable for a while. The absence of some macroinvertebrates may support

the hypothesis that the water is not suitable for fish or other aquatic life. While toxins

and other pollutants may come and go from time to time, their impact on aquatic life

will be most evident by analyzing how many and what kinds of macroinvertebrates

there are in a water

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REFERENCES

A.P.H.A. (1981). Standard methods for the examination of water and wastewater.

American Public Health Association, American Water Works Association & Water

Pollution Control Federation, Washington.

Ballance, J. B. (1996). Water Quality Monitoring - A Practical Guide to the Design

and Implementation of Freshwater. Physical and chemical Analyisis , 1-90.

Beede, D. K. (Apr 2005). Assessment of Water Quality and Nutrition for Dairy Cattle.

Mid-South Ruminant Nutrition Conference, (pp. 50-62). Washington.

Cleveland, L. L. (1998, April 6). Design an experiment to test the effects of increases

or decreases in dissolved oxygen levels on aquatic plants and animals. Retrieved

October 1, 2009, from

http://www.ncsu.edu/sciencejunction/depot/experiments/water/lessons/do/

dolesson3.htm

Elson, J. (2000). Method for determination of dissolved oxygen in water . U.S

Environment Protection Agency , 34-42.

Francis-Floyd, R. (1992). Dissolved oxygen for fish production. Retrieved October 1,

2009, from World Wide Web: http://edis.ifas.ufl.edu/BODY_FA002

Trease, L. S. (October 31, 2002). The Relationship Between Dissolved Oxygen &

Water Clarity In Milwaukee Area Water. Chicago: Science Book Press.

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