The document discusses biochemical oxygen demand (BOD) and its importance as a measure of water quality. BOD is defined as the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material in a water sample over a 5 day incubation period at 20°C. A higher BOD indicates a higher level of organic pollution. BOD is used to assess the effectiveness of wastewater treatment plants and provides an indication of overall water quality. The standard BOD test involves measuring the dissolved oxygen in a sample before and after 5 days, with the difference representing the oxygen consumed during decomposition of organic compounds.

1. Biochemical Oxygen Demand
BY
HANU PRATAP

2. DefinitionDefinition
• The Biochemical (or Biological) oxygen
demand (BOD) is a measure of the
amount of dissolved oxygen required to
break down the organic material in a given
volume of water through aerobic biological
activity. ( By Micro-organism)

3. Biochemical oxygen demandBiochemical oxygen demand
• Biochemical oxygen demand (BOD) (also called biological
oxygen demand) is the amount of dissolved oxygen needed (i. e.,
demanded) by aerobic biological organisms to break down organic
material present in a given water sample at certain temperature over
a specific time period. 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 surrogate of the
degree of organic pollution of water.
• BOD can be used as a gauge of the effectiveness of
wastewater treatment plants. It is listed as a conventional pollutant
in the U.S. Clean Water Act.
• BOD is similar in function to chemical oxygen demand (COD), in
that both measure the amount of organic compounds in water.
However,

4. DefinitionDefinition
• Biochemical oxygen demand or BOD is
a chemical procedure for determining the
rate of uptake of dissolved oxygen by the
rate biological organisms in a body of
water use up oxygen. It is not an precise
quantitative test, although it is widely used
as an indication of the quality of water.

5. Method for the measuring of BODMethod for the measuring of BOD
• Dilution method
To ensure that all other conditions are
equal, a very small amount of micro-
organism seed is added to each sample
being tested.
• Undiluted: Initial DO - Final DO = BOD
• Diluted: ((Initial DO - Final DO)- BOD of
Seed) x Dilution Factor

6. Test ProcedureTest Procedure
• The BOD test takes 5 days to complete and is
performed using a dissolved oxygen test kit. The
BOD level is determined by comparing the DO
level of a water sample taken immediately with
the DO level of a water sample that has been
incubated in a dark location for 5 days. The
difference between the two DO levels represents
the amount of oxygen required for the
decomposition of any organic material in the
sample and is a good approximation of the BOD
level.

7. BOD test bottles at the laboratory of aBOD test bottles at the laboratory of a
wastewater treatmentwastewater treatment plant.plant.

8. Taking samples from the influent rawTaking samples from the influent raw wastewaterwastewater streamstream
for BOD measurements at afor BOD measurements at a wastewater treatmentwastewater treatment plant .plant .

9. Method for the measuring of BODMethod for the measuring of BOD
• Manometric method
• This method is limited to the measurement
of the oxygen consumption due only to
carbonaceous oxidation. Ammonia
oxidation is inhibited.

10. Applications
Water Quality

11. Measures of Water Quality
Some of the Most basic and Important Measures
Dissolved Oxygen
Biochemical Oxygen Demand
Solids
Nitrogen
Bacteriological

12. Dissolved Oxygen (DO)
Typically Measured by DO probe and Meter
Electrochemical Half Cell Reaction

13. COD and BODCOD and BOD
• The standard BOD test requires five
days to complete - unable to provide
continuous monitoring of organic load.
• COD is often used for BOD screening.
• Both involve a 2 step process:
Step 1 - Oxidation of organic matter
Step 2 - Measurement of extent of oxidation

14. BOD Test
Dark
20o
C
Time
Standard – 5 days
Ultimate

15. BOD = I - F
I = Initial DO
F = Final DO
If all the DO is used up the test is invalid, as in B
above
To get a valid test dilute the sample, as in C above. In this
case the sample was diluted by 1:10. The BOD can then be
calculated by:
BOD = (I – F) D D = dilution as a fraction
D = volume of bottle/(volume of bottle – volume of dilution water)
BOD = (8 – 4) 10 = 40 mg/L

16. COD and BODCOD and BOD
• Biochemical Oxygen Demand (BOD) and Chemical Oxygen
Demand (COD) are ubiquitous measurements of overall water
quality.
• Among the most diagnostic parameters for the
determination of water quality in natural waterways and
waste streams.
• COD measures the equivalent amount of oxygen
required to chemically oxidize the organic compounds in
water
• BOD measures the equivalent amount of oxygen
required to biologically (microbes) oxidize the organic
compounds in water

17. COD and BODCOD and BOD
• The standard BOD test requires five days
to complete - unable to provide continuous
monitoring of organic load.
• COD is often used for BOD screening.
• Both involve a 2 step process:
Step 1 - Oxidation of organic matter
Step 2 - Measurement of extent of oxidation

18. Standard COD MethodStandard COD Method
(Dichromate)(Dichromate)
• Uses hazardous chemicals (dichromate,
concentrated acid, mercury) to oxidize organic
carbon in water into CO--
2 and H2O.
• Samples are digested at 150°C, 2-3 hour
process with cooling time
• The oxygen demand is determined by the
amount of oxidant consumed, using a
spectrophotometer or titration method.

19. Nanotechnology basedNanotechnology based
approachapproach
• Patented sensor consists of a UV-activated
TiO2 (titanium dioxide) photocatalyst
• Powerful oxidizing potential of TiO2 gives a true
measure of COD
• COD analysis can now be done by any operations staff
member

20. Nanotechnology basedNanotechnology based
approachapproach

21. COD ApplicationsCOD Applications
Municipal
•Incoming COD monitoring
•In-plant COD monitoring
•Potable water analysis

22. Industrial
•In-plant COD monitoring
•Process optimization

23. Laboratory
•COD analysis
•Multi-parameter
•Speed and accuracy
•Safety of employees

24. ConclusionConclusion
• Overcomes the weaknesses of traditional COD analysis
– Results in only 15 minutes
– No use of dichromate or harmful reagents
– Easy to use system for all operations staff
• Nanotechnology provides more accurate measure of
COD
• Excellent screening tool for BOD
• Recognized and used by the Ontario Ministry of
Environment

25. Chemical oxygen demandChemical oxygen demand
• In environmental chemistry, the chemical oxygen
demand (COD) test is commonly used to indirectly
measure the amount of organic compounds in water.
Most applications of COD determine the amount
of organic pollutants found in surface
water (e.g. lakes and rivers) or wastewater, making COD
a useful measure of water quality. It is expressed in
milligrams per liter (mg/L), which indicates the mass of
oxygen consumed per liter of solution.

31. ConclusionConclusion
• Overcomes the weaknesses of traditional COD analysis
– Results in only 15 minutes
– No use of dichromate or harmful reagents
– Easy to use system for all operations staff
• Nanotechnology provides more accurate measure of
COD
• Excellent screening tool for BOD
• Recognized and used by the Ontario Ministry of
Environment

32. Thank you