CIVIL ENGINEERING DEPARTMENT
POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN
Km 8, Jalan Paka, 23000 Dungun, Terengganu Darul Iman
Tel : 09-8400800 Faxs : 09-8458781
|DCC5172: STRUCTURE, HYDRAULICS & WATER QUALITY LAB|
LECTURER
LABORATORY
WATER QUALITY LABORATORY
PRACTICAL NO.
PRACTICAL TITLE
DOMAIN
C4_LD1(CLO1) / P4_LD2 (CLO2) /A3_LD9 (CLO3)
NAME
MATRIC NO.
SESSION
GROUP
NAME
MATRIC NO.
GROUP
MEMBERS
COMMENT
MARKS
C4/LD1
/ 30%
P4/LD2
/ 60%
A3/LD9
/10%
/100%
DCC5172: Structure, Hydraulic And Water Quality Laboratory
STUDENT CODE OF CONDUCT
CIVIL ENGINEERING DEPARTMENT
I hereby declare that have prepared the report with my own efforts. I also
pleaded not accept and provide any assistance in preparing this report and
make this solemn belief anything that is in it is true
_______________________________________________
Signature
Name
: ............................................................................
Registration no
: ............................................................................
Date
: ............................................................................
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CIVIL ENGINEERING DEPARTMENT
POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN
Km 8, Jalan Paka, 23000 Dungun, Terengganu Darul Iman
Tel : 09-8400800
Faxs : 09-8458781
WATER QUALITY LABORATORY
PRACTICAL 1D - CHEMICAL OXYGEN DEMAND (COD)
A.
OBJECTIVES
1.
B.
To determine the chemical oxygen demand of the given wastewater samples.
THEORY
The chemical oxygen demand (COD) is the amount of oxygen consumed to completely chemically oxidize
the organic water constituents to inorganic end products. COD is an important, rapidly measured variable
for the approximate determination of the organic matter content of water samples.
Some water samples may contain substances that are difficult to oxidize. In these cases, because of
incomplete oxidation under the given test methods, COD values may be a poor measure of the theoretical
oxygen demand. It should also be noted that the significance of the COD value depends on the
composition of the water studied.
COD is used as a measurement of pollutants in natural and waste waters to assess the strength of
discharged waste such as sewage and industrial effluent waters. It is normally measured in both municipal
and industrial wastewater treatment plants and gives an indication of the efficiency of the treatment
process. The dichromate reflux method is preferred over procedures using other oxidants because of
superior oxidizing ability, applicability to a wide variety of samples, and ease of manipulation. Oxidation
of most organic compounds is 95 -100% the theoretical value.
C.
APPARATUS & MATERIAL
1.
2.
3.
4.
5.
COD Reflux System – consisting Erlenmeyer flask (250 mL or 500 mL) with ground-glass 24/40
neck and 300 mm jacket Liebig West, or equivalent condenser with 24/40 ground-glass joint, and a
hot plate having sufficient power to produce at least 1.4 W/cm2 of heating surface.
Burette.
Pipette
COD vial
Reagent;
i)
Standard potassium dichromate 0.016667 M
 1000ml distilled water
 4.903 g potassium dichromate (K2 CR2 O7) dry 2 hour 150o C
 167 mL acid sulphuric (H2 SO4)
 33.3 g mercury sulphate (Hg SO4)
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DCC5172: Structure, Hydraulic And Water Quality Laboratory
ii)
Sulphuric acid reagent
 5.5g silver sulphate (Ag SO4)
 1kg acid sulphuric (H2 SO4).
iii)
Standard ferrous ammonium sulphate
 39.2g ammonium iron II sulphate 6-Hydrate {Fe (NH4)2(SO4)2. 6H2o}
 20ml acid sulphuric (H2 SO4)
 1L distilled water 0.)IV.
iv)
Ferroin indicator
Figure of Apparatus:
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DCC5172: Structure, Hydraulic And Water Quality Laboratory
D. PROCEDURE
Sampling Procedure
1.
2.
3.
The sample is collected in plastic container that is known no organic contamination in the container.
The sample is tested biologically.
Sample is preserved with sulphuric acid to a pH value < 2
Laboratory Procedures
1.
The substances were added in COD vial by followed the sequences below;
a)
Placed in COD vial 1 and 2 with;
 mL Potassium Dichromate Reagent
 mL Acid Sulphuric Reagent
b)
2.
3.
4.
5.
COD vial no.1: 2.5 mL sample
COD vial no.2: 2.5 mL distilled water
Refluxing mixture placed at COD Reactor with temperature 1500C for 1 hour.
After 1 hour, cool down the condenser with distilled water. Cooling down process continued to room
temperature.
Disconnect reflux condenser. The solution transferred to the conical flask and mixed up with 150ml
distilled water. Added with 3 drops of ferroin indicator.
Titrated K2 Cr2 O7 with Ferrous Ammonium Sulfate (FAS). The initial and final reading recorded.
The titration stopped when colour changed into reddish brown.
Titration Test
1.
2.
3.
E.
5mL Postassium Dichromate K2 Cr2 O7 solution (0.01667 M) diluted with 10 mL of distilled water
into 250 mL conical flask. Swirled and mixed slowly.
30 mL of concentrated acid sulfuric H2SO4 was added slowly and carefully. Titrated with FAS titrant
using 3 drops of ferroin indicator. The titration is stopped immediately when the colour changed into
reddish brown.
Initial and final reading was recorded.
DATA / RESULTS
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DCC5172: Structure, Hydraulic And Water Quality Laboratory
Table 1 - FAS standard titration data;
Reading of buret / pipette
Cone flask (Standard)
First reading
Last reading
Volume of FAS (mL)
Compute the molarity of FAS by using the given formula;
𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 𝑜𝑓 𝐹𝐴𝑆 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 =
𝑉𝑜𝑙𝑢𝑚𝑒 0.1667𝑀 𝐾2 𝐶𝑟2 𝑂7 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑡𝑖𝑡𝑟𝑎𝑡𝑒𝑑, 𝑚𝑙
𝑥 0.100
𝑉𝑜𝑙𝑢𝑚𝑒 𝐹𝐴𝑆 𝑢𝑠𝑒𝑑 𝑖𝑛 𝑡𝑖𝑡𝑟𝑎𝑡𝑖𝑜𝑛, 𝑚𝑙
Table 2 - COD test data collections;
Normality of FAS
(N)
Sample volume
(mL)
Volume of FAS used
In the original
In the blank
sample, B
sample, A
(mL)
(mL)
Compute the COD concentration in mg/L for the sample by using the given formula;
𝑪𝑶𝑫 𝒂𝒔
𝒎𝒈 (𝑨 − 𝑩) 𝒙 𝑴 𝒙 𝟖𝟎𝟎𝟎
=
(𝒎𝑳)𝒔𝒂𝒎𝒑𝒍𝒆
𝑳
Approved By:
………………………………………………….
(
)
F.
CALCULATION
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DCC5172: Structure, Hydraulic And Water Quality Laboratory
G. DISCUSSION
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DCC5172: Structure, Hydraulic And Water Quality Laboratory
1.
What is the purpose of using blank sample in the experiment?
2.
Briefly explain whether the value of COD obtain in this experiment are suitable to be discharged to
the stream.
H. CONCLUSION
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DCC5172: Structure, Hydraulic And Water Quality Laboratory
I.
LABORATORY SAFETY RULES
J.
REFERENCES
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