How to Determine the Solids in Water?

The aim is to determine the total solids, filterable, non-filterable solids, volatile and non-volatile. Before looking into the procedure, you can brush up on the what are solids in water by reading Solids in Water.

Test Apparatus

1. Evaporating dishes of 100 ml capacities made of porcelain.
2. Steam Bath
3. Drying oven
4. Desiccators
5. Muffle Furnace
6. Analytical balance
7. Imhoff Cone
8. Filter Paper
9. Filter Apparatus

Procedure

1. Test to determine Total Solids in Water

Ignite the clean evaporating dish at 500 ± 5 degrees for 1 hr in muffle furnace and cool in the desiccator. Note the empty weight of the dish (W1). Take 100 ml of the sample (V) in the weighed porcelain dish and evaporate to dryness in a steam bath and then in a hot air oven for 1 hr at 103 to 105 degrees. Cool the dish breifly in air desiccator and weigh it. the process of heating, cooling, dessicating, weighing is repeated until a constant weight is obtained (W2) { 0.5 mg weight change).

Calculations

Total Solids in mg/l = (mg of total residue x 100)/ Volume of sample in ml = ((W2-W1) x 1000)/V

W2 is the weight of the residue; W1 is the weight of the dish; V1 = Volume of the sample

2. Test to determine Filterable solids or Total Suspended Solids (TSS)

Dry the filter paper in a hot air oven for 1 hr at 103 to 105 degrees. Cool, dessicate and note the weight of the filter paper (W3). Filter a known volume of the well mixed sample  (V) and transfer 50 ml of the filtrate to the evaporating dish that is already ignited and weighed (W4). Place the dish with the content over the steam bath and evaporate to dryness. Place the evaporated sample in a hot air oven for 1 hr at 103 to 105 degrees. Desiccate and weigh the evaporating dish and contents to a constant weight (W5). 

Report the increase in weight over the empty dish as filterable residue.

Calculations

Filterable residue in mg/l = mg.of filterable residue x 1000/ml of the sample ={ (w5-w4)x1000}/V

3. Test to determine non-filterable residue or total suspended matter

The filter paper used in the test for filterable solids is removed and dried in a hot air oven for 1 hour at 103 to 105 degree celsius. It is cooled, desiccated and noted the weight (W7).

Calculations

Total non -filterable residue in mg/l = (mg of non-filterable residue x 1000) / ml of sample = ( (w7-w6) x 1000)/V

W6 = Weight of dry filter paper

W7 = Weight of non-filterable residue + filter paper

Also Read: 

1. Stages of Water Supply System
2. Water Demand-Fire Demand-Water Supply System