Total Suspended Solids TSS and Total Dissolved Solids TDS Measurements

Overview. In this procedure, you will first use 100mL of your sample to perform the most commonly used solids measurement, the total suspended solids (TSS). This requires you to filter a known volume of sample through a pre-heated and pre-tared glass-fiber filter, to remove the suspended solids. The difference between the initial (just filter) and final (filter with solids) weights, divided by the volume of sample, will yield the TSS. The TSS measurement accounts for all solids that do not pass through the filter (typically 0.2-0.45 mm in size). The filter is weighed after drying at 104°C, both before and after the filtering procedure. The filtrate (the remaining sample liquid) is then used in the dissolved solids determination (TDS, the next procedure). The TDS is a simple experiment where the filtrate is placed in a tared (pre-weighed) beaker and evaporated to dryness.

Student Procedures

Preparing Your Filters

1. Rinse three filters with 20-30mL DI to remove any solids that may remain from the manufacturing process. Place the filters in separate, labeled aluminum weight pans, dry them in a 104°C oven for 30 minutes, place them (filter and pan) in a desiccator, and obtain a constant weight by repeating the oven and desiccation steps.

Obtaining the TSS Measurement

2. Filter 100mL of sample through each tared filter. Save the filtrate.

3. Place each paper in its aluminum weight pan in the 104°C oven for 1h. Cool the filter and pan in a desiccator and obtain a constant weight by repeating the drying and desiccation steps. (This step will be completed after your normal lab meeting time.)

Calculation:

TSS mg/L

(average weight from step 3 in g sample volume in L

Total Dissolved Solids (TDS) Measurement

4. Obtain a constant weight for three 150-mL beakers, using the same procedure used for the filters in step 1.

5. Add 100 mL of your filtered sample to each beaker and evaporate it in the 98°C oven overnight.

6. The next day, place the beakers in the 104°C oven and heat them for 1h.

average inital weight from step 1 in g)(1000 mg/L)

7. Place the beakers in a desiccator until cool and obtain a constant weight.

8. Repeat steps 5 and 6 until you obtain a constant weight (within 0.5mg of each other). The differences between this weight and the weight of the beakers originally will be the total masses of dissolved solids in the 100-mL samples.

Calculation:

TDS mg/L

(average crucible weight from step 7 in g — average crucible weight empty in g)(l000 mg/g)

sample volume in L

Hints for Success

• Always completely mix your sample before removing any solution/suspension. The soil/sediment particles will settle and bias your results if you do not completely mix the sample every time you remove an aliquot.

• Perform all measurements in triplicate.

• Carefully clean all containers and pre-wash all filters with DI water prior to use. As noted in the procedures, you must heat filters to the maximum temperature that you will use experimentally, before filtering. Also as noted in the procedures, you must obtain a constant weight (generally within 0.5 mg) before you end each experiment. (Fingerprints and dust weigh enough to significantly affect your results.)

• Your balances have been calibrated, but for best results you should still use the same balance for every measurement. Even if the calibration on a balance is slightly off, the change in weight will probably be accurate.

Assignment. Turn in a table showing your measurements for each sample, your calculations TSS and TDS, and your final averages.

0 0

Post a comment