This document discusses biochemical oxygen demand (BOD) analysis. BOD is a measure of the amount of dissolved oxygen needed by aerobic biological organisms in water to break down organic material present in the water. When organic matter is present in water, bacteria consume dissolved oxygen as they break down the waste, leaving less oxygen available for other aquatic life. The BOD test determines the amount of oxygen consumed by bacteria over a 5-day incubation period at 20°C. A higher BOD indicates more organic pollution and less dissolved oxygen in the water. The standard BOD test involves diluting water samples, measuring initial dissolved oxygen, incubating in bottles for 5 days, and measuring final dissolved oxygen to determine oxygen used by bacteria.

1. Biochemical Oxygen
Demand Analysis
Pn. Zaifah Binti Che Wil
Diploma Kejuruteraan Alam Sekitar,
Jabatan Kejuruteraan Awam Politeknik Sultan Idris Shah.

3. For the beginning…..
 Water is “polluted” by many organic matter in its course of flow
 When organic matter is present in a water supply, the bacteria
present in water will begin the process of breaking down this waste.
 With this much of the available dissolved oxygen is consumed by
aerobic bacteria, robbing other aquatic organisms of the oxygen
they need to live.
 Biological Oxygen Demand (BOD) is a measure of the oxygen
use by microorganisms to decompose this waste.
 A large quantity of organic waste in the water supply, guarantees a
large number bacteria present to decompose this waste.
 In this case, the demand for oxygen will be high (due to all the
bacteria) so the BOD level will be high.
 As the waste is consumed or dispersed through the water, BOD
levels will begin to decline.

4. Dissolved Oxygen
D.O.
Amount of “FREE” Oxygen
O2
In the Water
Required By :
FISH
MICROORGANISMS
( Bacteria)

5. Dissolved Oxygen (DO)

6. BOD5

7. What is BOD?
Biochemical Oxygen Demand is the
amount of oxygen, expressed in mg/L
or parts per million (ppm), that bacteria
take from water when they oxidize
organic matter.

8.  BOD indicates a amount of pollution of water bodies.
 Lower BOD indicates the water is a good quality for
aquatic life or little aerobic acitivity whereas the
higher BOD indicates the water is highly polluted.
 When BOD is higher , then DO becomes lower .
 so, aquatic organisms are unable to survive at
normal rate , it becomes stressed , asphyxiate and
may die . (EUTROFICATION)

9. What is BOD?
Bacteria
+ Food + Oxygen Carbon
Dioxide
All three must present
in order to have BOD

10. What is BOD?
Dissolved oxygen levels are monitored
before and after incubation period, to
determine the amount of oxygen
depletion.

11. BOD (Biochemical Oxygen Demand):
Incubation conditions:
 Temperature - 20 ± 1ºC
 Time – 5 days
 In the dark
Botol gelap
Inkubasi 20oC
5 hari
DO5
DOi

12. BOD decomposition rates vary widely
DO
Consumed
(mg/l)
Decaying phytoplanton
biomass
Black water
organic matter
Municipal,
industrial
BOD loads
Time 5 days
BOD5

13. BODLEVEL:
BOD LEVEL (mg/l) Remarks
1mg/l very clean
2mg/l clean
3mg/l fairly
5mg/l doubtful
10mg/l contaminated
BOD of some collected samples from different sources:
• Normal water = 0-3
• River water = 5-20 mg/L
• Sewerage water = 50-100
• Industrial water = 150-1000
• Land for irrigation = 100
• Marine coastal area = 100
• Inland surface water = 30
• Public sewers = 350

15. Sewerage system

16. METHOD

17. DO Meter

19. Botol BOD
Sigid
Hariyadi
–
2005/2008

20. Determination o f BOD:
 The most common and popular method for
determination of biological oxygen demand is
standard method which is recognized by U.S . EPA .
 It is not accurate quantitative test , although it
is widely used as an indicates the amount of
pollution.

21. Determination o f BOD:
 Contoh sampel air sisa
diambil dari kolam.
 4 liter air suling diisi ke
dalam botol yang disediakan.
 Air suling tersebut diudarakan
selama 2 jam dengan cara
menggunakan alat
pengudaraan.

22. Determination o f BOD:
Masukkan 4 ml larutan
 Magnesium Sulfat,
 Buffer Fosfat,
 Ferum (II) Klorida, dan
 Kalsium Klorida
ke dalam 4 liter air suling yang sedang diudarakan
tadi.

23. BOD
Phosphate Buffer
Magnesium Sulfate
Calcium Chloride
Ferric Chloride
Distilled Water
Provide Essential Nutrients
Buffer pH

24. Determination o f BOD:
 Lakukan pencairan mengikut tahap pencemaran,
ambil air sisa yang telah dineutralkan sebanyak
100 ml dan campurkan dengan 900 ml air suling
yang telah diudarakan.
 Gunakan silinder penyukat 1000 ml untuk
melakukan pencairan.
 Perlu diingatkan, isipadu air sisa yang telah
dicairkan mestilah melebihi 300 ml supaya
mencukupi untuk memenuhkan botol BOD nanti.

25. Determination o f BOD:
 Penuhkan botol BOD dengan air sisa yang telah
dicairkan dan ambil DO awalnya dengan
menggunakan DO meter untuk bacaan hari 0
 Tutup rapat botol BOD sehingga tiada gelembung
udara tidak kelihatan dan simpan dalam incubator
pada suhu 20°C selama 5 hari.
 Ambil bacaan DO untuk pengeraman selama 5 hari.
Dapatkan perbezaan antara DO tersebut dan
didarabkan dengan pencairan memberikan nilai
BOD bagi contoh sampel tersebut.

26. BOD PROCEDURE, (cont.)
FILL BOTTLE (with dilution water)
MEASURE INITIAL D.O.
STOPPER
(No Air Bubbles)
SEAL
(Water and Cover)

27. BOD PROCEDURE, (cont.)
INCUBATE
MEASURE FINAL D.O.
(wash bottles)
20 ± 1°C
5 Days ± 6 hour

28. Thankyoufolks…for
yourpatience