Principle
A well mixed sample is filtered through a weighed standard glass fiber filter and the residue retain on the filter is dried to a constant weight at 103 to 105oC. The increase in the weight of the filter represents the total suspended solids (TSS).
The residue from the above method is ignited to constant weight at 550 ± 50oC. The remaining solids represent the fixed solid while the weight lost on ignition is the volatile solids.
Environmental significance
Suspended solids determination is used to evaluate the strength of domestic wastewater and to determine efficiency of treatment units.
Suspended solids and volatile suspended solids tests are particularly valuable in determining the amount of suspended solids remaining after settleable solids have been removed in primary setting units, for the purpose of determining the loading of remaining materials on secondary biological treatment units.
Materials
1. Glass fiber filter (2.2 to 4.7 cm diameter) with membrane filter assembly, or Whatman grade filter paper with Torsion filter assembly.
2. Drying oven
3. Muffle furnace for operation at 550 ± 50oC
4. Desiccator
5. Analytical balance capable of weight upto 0.1 mg
Procedure
1. Take glass fibre paper of 2.2 to 4.7 cm diameter.
2. Dry in an oven at 103 to 105oC for one hour.
3. Cool and take empty weight of filter paper (W1)
4. Filter a known quantity of sample.
5. Then wash with 10 ml of distilled water.
6. Continue suction for about 3 minutes after filtration is complete.
7. Dry for at least 3-4 hours at 103 – 105oC in an oven.
8. Cool in a desiccators till constant weight (W2) is obtained.
9. The residue obtained as above can be used for volatile suspended solids, in case it is needed, then follow the method as follow.
Ignite the residue obtained as above in muffle furnace at 550 ± 50oC
for 15 – 50 minutes
10. Take out the dish or filter disk-containing residue from furnace. Let it
cool partially in air until most of the heat has been dissipated
11. Transfer to a desiccators for final cooling
12. Weight to constant weight (W3)
Note:
1. Run at least one filter blank along with the sample.
2. Whatman filter paper can be used only for suspended solids, as it
cannot with stand 550-± 50oC temperatures
Calculation
1. Total suspended solid, mg/L = (W2 - W1) x1000 /SampleVolume mL
2. Volatile suspended solids, mg/L= (W2 - W3) x1000 SampleVolume mL
3. Fixed solids, mg/L=(W3 - W1) x1000/SampleVolume mL
Where
W1 = Weight of dish or filter
W2 = Weight of residue + dish or filter after drying at 103 – 105oC
W3 = Weight of residue + dish or filter after ignition