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B.O.D & C.O.D
( BIOCHEMICAL OXYGEN DEMAND)
AND
(CHEMICAL OXYGEN DEMAND )
DEFINATION ( B.O.D)
 Biochemical oxygen demand (BOD) is the amount
of dissolved oxygen needed by aerobic biological organ...
DEFINATION ( C.O.D)
 COD (Chemical Oxygen Demand) is the amount of
oxygen required to degenerate all poution in a
chemica...
DIFFERENCE
B.O.D
 BOD is only a measure-
ment of consumed oxygen
by aquatic microorganisms
to decompose or oxidize
organi...
IMPORTANT POINTS
 BOD is similar in function to chemical oxygen demand (COD),
in that both measure the amount of organic ...
CALCULATION (C.O.D)
 The following formula is used to calculate COD:
COD= 8000(b-s)n
sample volume
 where b is the volum...
CALCULATION (B.O.D)
 BOD5 is calculated by: ( Dilution method )
unseeded : BOD5 = ( DO – D5)
P
seeded : BOD5 = ( DO-D5 ) ...
THANK YOU
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Biochemical oxygen demand (BOD) AND Chemical Oxygen Demand PDF

Biochemical oxygen demand (BOD) AND Chemical Oxygen Demand PDF

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Biochemical oxygen demand (BOD) AND Chemical Oxygen Demand PDF

  1. 1. B.O.D & C.O.D ( BIOCHEMICAL OXYGEN DEMAND) AND (CHEMICAL OXYGEN DEMAND )
  2. 2. DEFINATION ( B.O.D)  Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period.  The term also refers to a chemical procedure for determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water.[1]  The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a robust surrogate of the degree of organic pollution of water.
  3. 3. DEFINATION ( C.O.D)  COD (Chemical Oxygen Demand) is the amount of oxygen required to degenerate all poution in a chemical way (by adding oxidising agents and heating). In general with chemical destruction you can remove more polution than with the biological way.  . It is expressed in milligrams per liter (mg/L) also referred to as ppm (parts per million), which indicates the mass of oxygen consumed per liter of solution.
  4. 4. DIFFERENCE B.O.D  BOD is only a measure- ment of consumed oxygen by aquatic microorganisms to decompose or oxidize organic matter. > Although, some of the organic compounds, which can be broken down by microorganisms, are countable for the biological oxygen demand, they may not be encountered in measuring chemical oxygen demand C.O.D  COD refers the requirement of dissolved oxygen for the oxidation of organic and inorganic constituents both.
  5. 5. IMPORTANT POINTS  BOD is similar in function to chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matter.  For many years, the strong oxidizing agent potassium permanganate (KMnO4) was used for measuring chemical oxygen demand. Measurements were called oxygen consumedfrom permanganate, rather than the oxygen demand of organic substances. Potassium permanganate's effectiveness at oxidizing organic compounds varied widely, and in many cases biochemical oxygen demand (BOD) measurements were often much greater than results from COD measurements. This indicated that potassium permanganate was not able to effectively oxidize all organic compounds in water, rendering it a relatively poor oxidizing agent for determining COD.
  6. 6. CALCULATION (C.O.D)  The following formula is used to calculate COD: COD= 8000(b-s)n sample volume  where b is the volume of FAS used in the blank sample, s is the volume of FAS in the original sample, and n is the normality of FAS. If milliliters are used consistently for volume measurements, the result of the COD calculation is given in mg/L.  The COD can also be estimated from the concentration of oxidizable compound in the sample, based on its stoichiometric reaction with oxygen to yield CO2 (assume all C goes to CO2), H2O (assume all H goes to H2O), and NH3 (assume all N goes to NH3), using the following formula:  COD = (C/FW)(RMO)(32)Where C = Concentration of oxidizable compound in the sample,FW = Formula weight of the oxidizable compound in the sample,RMO = Ratio of the # of moles of oxygen to # of moles of oxidizable compound in their reaction to CO2, water, and ammoniaFor example, if a sample has 500 wppm of phenol:  C6H5OH + 7O2 → 6CO2 + 3H2OCOD = (500/94)(7)(32) = 1191 wppm
  7. 7. CALCULATION (B.O.D)  BOD5 is calculated by: ( Dilution method ) unseeded : BOD5 = ( DO – D5) P seeded : BOD5 = ( DO-D5 ) – ( B0 – B5 )F P  where: DO is the dissolved oxygen (DO) of the diluted solution after preparation (mg/l); D5 is the DO of the diluted solution after 5 day incubation (mg/l); P is the decimal dilution factor ; B0 is the DO of diluted seed sample after preparation (mg/l) ; B5 is the DO of diluted seed sample after 5 day incubation (mg/l) ; F is the ratio of seed volume in dilution solution to seed volume in BOD test on seed
  8. 8. THANK YOU

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