River Pollution: Analyzing river pollution level from industrial waste water through Biochemical Oxygen Demand (BOD) water sample examination

Intro to River Pollution

Fresh water from rivers that generally flows through residential or industrial areas are often used for daily life purpose. People live around the river most likely uses river as source of water provider and as a house waste disposal while industries will use it as a final destination of their waste disposal. Those are the main factor that influenced the condition of water in the river declining that could lead to a significant lost in the river ecosystem.

Research Objective

To investigate the intensity of water pollution in the river caused by industries and factories by examine Oxygen amount (O2), Biochemical Oxygen Demands (BOD), and amount of Iron (Fe) dissolved in the water.


The investigation will be perform in two stages which are:

1. Practical fieldwork
Besides taking water samples for laboratory works, there are several observation that carry out in the fieldwork, which is:
Collecting Data: time and date, weather, environment situation, color and smell of the water, river depth and also the grimy level of the water.
Measuring: air temperature, pH level, water temperature, and water velocity

•    Width of river A with:
•    measuring the width of the river
•    measuring the height of water level
•    put the variable; A = width x height
•    River debit (Q):
•    Calculating velocity v = length / time
•    Debit: Q = v . A

Water sample gathering by:

•    Each decision point in the sample taken 2 bottles (big bottles) by the mouth of the bottle is inserted into the water parallel to the direction of river flow.
•    After the bottle sample is full, and close it tightly so it’s not to get air bubbles in the bottle. After that, then stored to be brought back to the laboratory and do not forget to sign or code given to distinguish a single point with another point.

I.3.2. Instruments used in the Field
The tools used in the field in this experiment are:

– Large sample bottles.   – Rol meters.
– PH meter.    – Thermometer.
– Markers.    – Tool box.
– Stop watch.

I.3.3.Investigation method in the laboratory

The results obtained in the field and then taken to the laboratory for examination:
– Content of oxygen (O 2) dissolved (O 2 field immediate, O2 field two days)
– Biochemical Oxygen Demand (BOD),
– Content of iron (Fe) the amount of solute.

I.4. Examination method for dissolved Oxygen (O2)

Mean dissolved oxygen content tests (O2) is to measure the size of water pollution contained in the sample. Results of dissolved O2 test were able to give an indication whether the water sample was contaminated or not. If O2 is high, the figures obtained are still low pollution or may not have been contaminated. If O2 is low means the water is already contaminated. Here are the opposite relationship between O2 and BOD. When the O2 level is high, then the BOD will be low, and vice versa if O2 level is low, BOD level will be high.

I.4.1.Equipments needed in the examination of O2
Equipment necessary for the examination of dissolved oxygen content in the laboratory are:
1.    Bottle O2 (reagent bottles).
2.    Pipette.
3.    Burette and stative burette.
4.    100 ml measuring glass.
5.    250 ml Erlenmeyer pumpkin.

I.4.2. Necessary Reagents
To analyze the dissolved oxygen content in sample on the small bottle, necessary reagents are:
1.    Concentrated sulfuric acid (H2SO4 concentrated).
2.    Starch (starch solution) 1%.
3.    Sodium Thio Sulphate 1 / 40 Neutrality (1 / 40 N. Na2S2O3).
4.    Per O2.
5.    MnSo4.

I.4.3. Sample processing
Steps by steps of laboratory works for analyzing the samples are:
1.    Open the lid of large sample bottle containing the water sample and then given Per.O2 (20 drops) and MnSO 4 (20 drops), close the bottle and turn it upside down and vice versa until the solution is homogen, let it stand briefly until it forms deposits. Then add concentrated H2 SO4 as much as 20 drops and close the bottle again. Try not to get air bubbles in the sample bottle and continue shaking it with upside downwards to dissolve all the sediment.
2.    Take 100 ml of liquid from the bottle and insert into the erlenmeyer flask.
3.    Add 10 drops of starch to the erlenmeyer flask. If intense blue color appears in the solution, then the samples contain high intensity of O2. Give a Titration method using a solution of Sodium Thio Sulphate (1/40 N) until the solution color changed to pale blue (almost white).
•    Calculate the use of Sodium Thio Sulphate as much as ∆v.
•    The Formula: O2 = (1000/100) * ∆v * 0.2 * f
•    Description:
•    02 = oxygen content in the sample (mg / l)
•    ∆v = number of Na 2 S 2 0 3 is used to titration
•    F = Thio factor = 1
•    0.2 = 1 ml Thio contains 0.2 mg of 02
•    100 = number of samples in titration
•    1000 = to get the mg / l

I.5. Biochemical Oxygen Demand (BOD) Investigation
Biochemical Oxygen Demand is the amount of oxygen needed by bacteria to decompose (oxidize) most of the dissolved organic substances and some substances suspended in the water.

I .5.1. Necessary Instruments
Necessary Instruments for Biochemical Oxygen Demand investigation in the laboratory are:
1.    Bucket and bailer
2.    1-liter glass beaker
3.    Suction pipette 10 ml
4.    Air pump (aeration)
5.    Stirrer tool
6.    Bottle O2 (small reagent bottle)
7.    Markers
8.    incubator
9.    Pipette drops
10.    Measuring glass 100 ml, 500 ml, 10 ml
11.    250 ml Erlenmeyer flask
12.    Burette and burette stative

I.5.2. Necessary Reagents
To investigate the dissolved oxygen content that is on small sample bottle, then necessary reagents to be used are:
1.    Distilled water
2.    Peroxide (Per. O2)
3.    Mangansulfat (MnSO4)
4.    Concentrated Sulfuric Acid (H2SO4 concentrated)
5.    Starch (starch solution) 1%
6.    Sodium Thio Sulphate 1/40 Neutrality (1/40 N. Na2S2O3).

I.5.3. Sample processing
The steps to be done in the laboratory for investigating the samples are:
1.    Make the same amount of diluent water with the samples that will be examine. One sample of water will need approximately 400 ml of diluent by adding 1 ml each of phosphate buffer MgSO4, CaCl2, FeCl3 on each liter of distilled water. Then aerating the diluent water with aeration pump for approximately 30 minutes to reach oxygen saturation.
2.    Standard for determining the amount of diluent water from the calculation of oxygen is:

Less or equal to 1.9  diluent 10 times 2.0 to 3.9   diluent 8 times
•          4.0 to 5.9   diluent 4 times
more or equal to 6.0  diluent 2 times
Example: dilution 4 times
Take a water sample : ¼ x 400 ml = 100 ml
Take the diluent water : 400 ml – water samples
▪          = 400 ml – 100 ml = 300 ml
•    The original water sample and diluent then mixed together and stir until blended.
3.    Take two bottles that had been provided and then fill them until full and cover them tightly.
4.    Store one bottle of sample inside the incubator with 27º C temperature for two days while the other bottle unclosed

Bottles stored in an incubator with a temperature of 27 0 C for 2 (two) days while the other bottle is open given 10 drops of peroxide and 10 drops of manganese sulphate. After that, mix the samples by inverting upside down the sample bottle and wait until it forms deposit. Add H2SO4 solution, close the bottle and mix the sample by inverting upside down. Then check the content of O2 as O2 immediate.

Formula: BOD = (O2 immediately – O2 2 days) x diluent
I.6. Total Dissolved Heavy Metal (Fe) Investigation
I.6.1. Necessary Instrument
Necessary instrument for laboratory investigation of the amount of dissolved metal content in the samples are:

1.    Test tube
2.    Tube rack
3.    Suction pipette 1 ml
4.    Markers
5.    Pipette drops
6.    10 ml measuring cup

I.6.2. Necessary Reagents
To check the dissolved metal content in the bottle is a small sample, the reagents used are:

1.    Distilled water
2.    Fe standard solution of 0.01
3.    Acid sulfate 4N (H2SO4 4N)
4.    Potassium permanganate solution 0.1 N (0.1 N KMnO4)
5.    KCNS 20%
In the examination of the amount of dissolved iron content, there are two main things to do together, namely:
1.    Making a standard solution of Fe as a comparison.
2.    Examination Fe levels in the sample.

I.6.3. Making Fe standard solution
The steps to be done in the laboratory for the making of Fe standard solution is:

1.    Prepare a small tube of 6 pieces.
2.    Fill each tube with 10 ml of aquades.
3.    Add 10 drops of H2SO4 4N in each test tube, cover with the thumb and be inverted.
4.    Add 0.01 Fe standard solution in a test tube into each 0; 0.1; 0.2; 0.3; 0.4 and 0.5 ml and then closed with the thumb and inverted until homogeneous.
5.    Add 10 drops of 0.1N KMnO4 in each test tube, cover with the thumb and be inverted to appear pink color (red wine).
6.    Add 10 drops of 20% KCNS into each tube, cover with the thumb and flipped through until arising yellowish color getting darker and darker.

I.6.4. Samples processing
The steps to be done in the laboratory for samples investigation are:

1.    Prepare a small test tube of sample examined.
2.    Take water samples from each 10 ml of points and enter into a small tube that has been available.
3.    Add 10 drops of H 2 SO 4 4 N in each test tube, cover with the thumb and be inverted.
4.    Add 10 drops of 0.1 N KMnO 4 into each tube, cover with the thumb and be inverted to appear pink (red wine). Set aside for a while and when the young colors add another missing 0.1 N KMnO 4 until the color is stable.
5.    Add 10 drops of 20% KCNS into the tube, cover with the thumb and then be inverted, if arising nankin it means Fe-positive.
6.    Comparing with the standard colors that have been made.
Formula: (1000/10) * b * 0.01
◦    Fe = iron content of the sample (mg / l)
•          1000 = to get the mg / liter.
•          10 = amount of samples titration.
•          0.01 = 1 ml solution containing 0.01 mg Fe.
•          b = comparison with standard results. 

>>> This method is a standard river investigation in hydrolab. This laboratory instruction is re-written and translated by Andreas Siagian – The House Of Natural Fiber, an alumni of Atma Jaya Yogyakarta University, Civil Engineer Study Program. This instruction has been tested by practical works and implemented in a national curriculum of Environmental Engineering For Civil Engineer.