Determine BOD of Bagmati River Water Sample: Calculation

REQUIREMENTS:

APPARATUS REQUIRED:

  1. Bod bottle
  2. Conical flask
  3. Burette
  4. Beaker
  5. Pipette
  6. Measuring Cylinder

Chemicals required:

  1. Sodium thiosulphate
  2. Alkaline potassium Iodide
  3. Magnese  sulphate
  4. Starch
  5. Conc. H2SO4

THEORY:

   Biological oxygen demand is a measurement of amount of dissolved oxygen(DO) that is used by aerobic microorganisms when decomposing organic matter in water. Nitrates and phosphates are plant nutrients and can cause plant life and algae to grow they die quickly. This contributes to organic waste in water.

Generally, BOD level in water indicate.

BOD level in mgll Indicators

         1 – 2 Very Good

         3 – 5 fair: moderate polluted

         6 – 9 poor: some what polluted

        10 or >10                          very poor: very polluted

PROCEDURE:

                 First of all, the dilution process was done. 1l of distilled water was taken in the volumetric flask. 1ml of phosphate buffer was added along with 1ml of Mg SO4. 7H2O, 1ml of CaCL2  was added along with 1ml of MgSO4,7H2O and then 1ml of FeCl3. 6H2O was added. The solution was mixed well for the complete preparation, 50ml of sample was taken from the sample bottle of 2 litre bottle.

Now finally for BOD test, 2 BOD bottle were taken. The bottle was wrapped with carbon paper and was kept in BOD in cupboard at 200C for 5days. 

In second bottle DO content of sample water was determined by using winkerls Podsmetric method.

CALCULATION FORMULA:

       BODs= (DO initial DO )-(Do five day (DO5)*D.F.

OBSERVATION TABLE:

  1. For Sundarijal

Initial observation:

S.N.Volume of sampleInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
150ml01.71.7
250ml1.73.61.91.9
350ml3.65.51.9

Final observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
150 ml01.61.6
250 ml1.63.11.51.5
350 ml3.14.61.5
  1. For Pashupati

Initial observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
150 ml01.61.6
250 ml2.44.11.71.7
350 ml4.15.81.7

Final observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
150 ml01.61.6
250 ml1.63.11.51.5
350 ml3.14.61.5
  1. For Buddhanagar

Initial observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
150 ml02.22.2
250 ml2.23.51.31.3
350 ml3.54.81.3

Final observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
150 ml18.919.70.8
250 ml19.720.60.90.9
350 ml20.621.50.9
  1. For chovar:

Initial observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
50 ml01.21.2
50 ml1.22.31.11.1
50 ml2.33.41.1

Final observation:

S.N.Volume of sample takenInitial buretle readingFinal buretle readingDifferent buretle readingConcurrent reading
50 ml01.71.7
50 ml1.73.01.31.3
50 ml3.04.31.3

CALCULATION:

  1. For sundarijal

Do initial = (ml*g) of Na2S2O3*8*100/ V2(V1-V/V1)

= 1.9*0.025*8*1000/50(300-4/300)

= 7.7032 mg/l

Do (5 days) = 1.5*0.025*8*1000/50(300-4/300)

= 6.081 mg/l

BOD of Sundarijal = ( Do initial- Do5day) *d.f.

= (7.7032-6.081)*10

= 16.222 mg/l

2. Calculation of Pashupati

Do inintial = 1.7*0.025*8*1000/50(300-4/300)

= 6.89 mg/l

Do (5 days) = 1.5*0.025*8*1000/50(300-4/300)

= 6.081 mg/l

BOD = (6.89-6.081)*10

= 8.09 mg/l

3. Calculation of Buddhanagar

Do initial = 1.3*0.025*8*1000/50(300-4/300)

= 5.27 mg/l

Do (5 days) = 0.9*0.025*8*1000/50(300-4/300)

= 3.648895 mg/l

BOD= (5.27-3.64)*10

= 16.3 mg/l

4. Calculation of Chovar

Do initial = 1.3*0.025*8*1000/ 50(300-4/300)

= 5.27 mg/l

Do (5 days)= 1.7*0.025*8*1000/50(300-4/300)

= 4.45976 mg/l

BOD = (5.27-4.45)*10

= 8.2 mg/l

CONCLUSION:

               From the above experiment we can conclude that the comparative study of biological oxygen demand (BOD) at different location of Bagmati river was done.

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