9. • insensitive to the
H+ ions in the solution
• most widely used is the
silver/silver chloride
electrode
• another commonly used
reference electrode is the
calomel electrode
11. The solids retained on a filter paper of pore size 2.0
µm or smaller, during the filtration of the sample
water
Total Suspended Solids are the amount of filterable
solids in a water sample. Samples are filtered
through a glass fiber filter. The filters are dried and
weighed to determine total suspended solids in
mg/L.
12. Prepare a 0.45 micron filter using wash-dry-cool cycle
Seat filter with DI water prior to filtration
Pippet a measured volume into filtration apparatus
from stirred sample
Wash filter with 3 x 10 mL washings DI water
Apply suction for 3 minutes after washing
Transfer to aluminum dish for support
Dry in the oven at 103-105 °C overnight (should be 1 h)
Place in a desiccator to cool to room temperature,
reweigh to the nearest 0.1 mg
Calculate TSS in mg/L
13. Total suspended solids (TSS) :
The total suspended solids (TSS) is given by thefollowing
formula:
mg/L Total suspended solids = ( A-B) × 1000 / ml sample
Where,
A = weight of filter disk with dried residue
B = weight of filter disk only
14. The solids that pass through the filter paper during
the filtration of sample water
Total Dissolved Solids are those solids (inorganic +
organic) that pass through a filter of 2.0 μm or
smaller. They are said to be non-filterable. After
filtration the filtrate (liquid) is dried and the
remaining residue is weighed and calculated as
mg/L of Total Dissolved Solids
15. 1. Dry a clean dry beaker at 103-105 °C for at least 1 hour
2. Desiccate until cool and weigh to nearest 0.1 mg
3. Filter 50.0 mL through a 0.45 μm filter paper into clean
dry beaker using technique described above
4. Heat the sample to just below boiling and reduce the
volume to 10 mL
5. Allow the beaker to cool and dry in the oven at 103-105
°C overnight
6. Remove the beaker and place in a desicator to cool to
room temperature, reweigh to the nearest 0.1 mg
7. Calculate TDS in mg/L
16. Total Dissolved solids (TDS):
The total dissolved solids are given by the formula:
mg/L Total dissolved solids = ( A-B) × 1000 / ml sample
Where;
A = weight of dried residue + dish weight (mg)
B = weight of dish (mg)
19. Dissolved Oxygen is the amount of gaseous oxygen
(O2) dissolved in the water. Oxygen enters the water
by direct absorption from the atmosphere, by rapid
movement, or as a waste product of plant
photosynthesis. Water temperature and the volume of
moving water can affect dissolved oxygen levels.
Oxygen dissolves easier in cooler water than warmer
water.
20. Adequate dissolved oxygen is important for
good water quality and necessary to all forms
of life. Dissolved oxygen levels that drop
below 5.0 mg/L cause stress to aquatic life.
Lower concentrations cause greater stress.
Oxygen levels that go below 1-2 mg/L for a
few hours may result in large fish kills.
21. Materials:
300.0 ml BOD bottles or SOLA (glass) bottles with
cap
250.0 ml graduated cylinder
500.0 ml Erlenmeyer flasks
1.0 ml Pipettes
Rubber aspirator
Titration set-up
22. Collect samples in a 300 mL SOLA bottle
Add 2ml of manganous sulfate solution
Add 2 ml of alkaline-iodide-sodium azide
solution
Shake the bottle by inverting several times
Allow solution to settle
Add 2ml of conc. sulfuric acid
Shake well until precipitate is dissolved
23. Pour 200ml of sample from the SOLA bottle into an
Erlenmeyer flask
If the solution is
reddish-brown in
color, titrate with
0.0250 N sodium
thiosulfate
If the solution has no
reddish-brown color, or is
only slightly colored,
add a small quantity
(approx. 1 mL) of starch
indicator.
24. BOD is the amount of dissolved oxygen needed
by aerobic biological organism in a body of
water to breakdown organic material present in
a given water sample at certain temperature
over a specific time period (5 days).
26. A. Dilution
Dilution Factor: The dilution factor, DF, is the ratio of the
final volume to the volume of sample therein. (e.g., for
the bottle method, the volume of the BOD bottle,
usually 300 mL; for the graduated bottle, usually 300
mL; for the graduated cylinder method, the volume of
the cylinder, usually 1000 mL).
DF for the bottle method = {Volume of
Diluted Mixture÷Volume of Sample in
Mixture
27. B. DO fixation
1. Slowly siphon three portions of aerated dilution water
into three separate BOD bottles. Avoid adding
atmospheric O2to dilution water.
2. To two of the three BOD bottles, add 1 2.To two of the
three BOD bottles, add 1 ml MnS04solution, followed
by 1 ml alkali-iodide-azide reagent. Submerge pipette
tips in sample when adding reagents. Rinse tips well
between uses.
3. Stopper carefully to exclude air bubbles; mix by
inverting bottle several times.
4.When precipitate has settled to about half the bottle
volume, carefully half the bottle volume, carefully
remove the stopper and add 1.0 ml conc. sulfuric acid.
Re-stopper and mix by gentle inversion until the iodine
is uniformly distributed throughout the bottle.
28. C. DO Measurement
5. Transfer 203 ml of sample into conical flask and
titrate with 0.0250N sodium thiosulfate to a pale
straw color.
6. Add 1-2 ml of starch solution and continue to
titrate to first disappearance continue to titrate to
first disappearance of the blue color. (200 ml of
original dilution water is equal to 203 ml of
dilution water plus reagents).
7. Determine the initial concentration of dissolved
oxygen in one bottle of the mixture of sample and
dilution water (DO), and in one of the water
(DOinitial), and in one of the bottles containing
only dilution water.
29. 8. Place the other bottles in the incubator
9. Incubate the blank dilution water and the diluted
samples for 5 days in the dark at 20 °C.
10. After 5 days, remove the bottles, fix the DO and
measure the DO (DOfinal) DO and measure the DO
(DOfinal)
11. Calculate BOD5
BOD5(mg/L) = {DOinitial(mg/L) of first bottle -
DOfinal(mg/L) of second bottle} x dilution factor
30. COD is the total amount of oxygen required to
chemically oxidize the bio degradable and non-
biodegradable organic matter.
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.
31. Water sample is refluxed in strong acidic solution
with a known excess amount of potassium
dichromate.
After digestion, the remaining unreduced K2Cr2O7
is titrated with Ferrous Ammonium Sulfate (FAS)to
determine K2Cr2O7 consumed.
This gives us the oxidizable organic matter in
terms of oxygen equivalent.
32. 1. Wash 300 ml round bottom refluxing flask.
2. In refluxing flask put one spatula of HgSO4 + 10 ml
sample + 5ml K2Cr2O7 + 15 ml concentrated H2SO4.
3. Add small amount of silver sulphate.
4. Shake well and reflux for 2 hr.
5. Cool and add little amount of distilled water to the
flask through the condenser
6. Titrate the solution in the flask against FAS using
Ferrion indicator
7. End point green color to reddish brown
33. CALCULATIONS
The COD in mg/l is determined by the formula,
COD mg/l = (A-B)xNx8000
ml sample taken
A = ml of FAS required for blank.
B = ml of FAS requires for sample.