Total suspended solids (TSS)

Sample filtration

Supplies and equipment

• Whatman GF/F circle filter pads, 47 mm
• GAST vacuum pump and water rig (already assembled)
• Forceps
• Graduated cylinder
• Squirt bottle filled with deionized water
• Pre-cut foil packet
• Sample baggie
• Sharpie marker

Procedures

General filtering notes

• Shake closed water sample container well before filling the graduated cylinder. Otherwise, the solids sink to the bottom of the container.
• Rinse graduated cylinders three (3) times (a.k.a. sample rinse) prior to starting filtration of a new water sample container.
• Make sure you write the volume of water filtered for each sample on your data sheet.
• Do not contaminate the filter pads or the inside of the foil packets by touching with your fingers. Use forceps only. The oils on your fingers will register on the 4-decimal place scale used to weigh the filters.
• Be very gentle with the filter pads to avoid tearing/ripping. If a filter is torn after filtering is complete, include all pieces in foil packet. If filter is torn before filtering, discard.
• Never run the vacuum pump with all air valves closed. This will burn out the pump. Don’t run the pump for too long without any samples filtering either. This will tax the pump.

Filtering instructions

1. To collect a sample, rinse a 1-l Nalgene container three times with sample water, then fill with sample water.
2. Label a foil packet using labeling tape and a sharpie with the location, date and time, filter number, and volume filtered.
3. Connect a piece of vacuum tubing to the pump spigot. Attach the other end to a filtration flask.
4. Center a prenumbered, combusted, weighed 47-mm GFF filter pad on the filter holder (frit) number side down if number is visible. Secure the filtration funnel to the frit.
5. Rinse a graduated cylinder three times with sample water.
6. Measuring with a graduated cylinder, pour 200 ml of sample water into the filter holder. Ensure it is tight before pouring to avoid spills.
7. Open the filter valve and turn on the pump using the labeled switch on the side of the lab bench.
8. Rinse the filter funnel unit twice with deionized (DI) water after the initial volume has filtered through the pad. This step is VERY IMPORTANT because it rinses out the salt.
9. Turn off the pump before unscrewing the filtration tunnel and removing the filter pad. Using 2 forceps and without touching the material on the filter, fold the filter in half with the filtered material on the inside of the fold. Remove the folded pad from the filtration unit with forceps and place inside your pre-labeled aluminum foil packet. Do not touch the filter pad or the inside of the foil pouch with your fingers. Sometimes the folded filter pad will pop open as you are attempting to place it in the foil packet. If this occurs, use forceps to hold the folded filter pad in half and then fold the aluminum packet closed. Make sure that only the outside of the folded pad (area without filtered material directly on it or visible) is touching the foil.
10. If you have not already done so, fold all sides of the aluminum packet closed.
11. Record the date, time, location, filter number, and total volume filtered on each foil packet and on the data sheet.
12. Label a ziplock freezer bag using a black sharpie marker with the date and “MRNE 395”, place the packet into the freezer bag, and store on ice until freezing.
13. Remove the vacuum hose. Discard the filtered water. Rinse the hose and filtering flask with DI water.

Post-filtration filter measurement

Supplies and equipment

• Pencil
• Muffle Furnace
• Analytical balance (reads to 4 decimal places)
• Filter log book
• Sealed containers
• Drying Oven
• Desiccator with desiccant
• Porcelain crucibles or aluminum weigh boats
• Nitrile gloves

Procedures

Drying and muffling filters

1. Wearing gloves, label an aluminum weigh boat with the filter number, and record the weight.
2. Gently unfold the aluminum sheet storing the filter, and use forceps to move the filter to the labeled weight boat. DO NOT DISCARD THE FOIL UNLESS YOU HAVE RECORDED ALL INFORMATION FROM THE LABEL.
3. Dry filters at 105◦C overnight. Allow samples to cool to room temperature in a desiccator.
4. Wearing gloves and using filter forceps, weigh filters and record weights (in grams).
5. Place filters back in drying oven for a minimum of 1 hour.
6. Re-weigh filters until a constant dry weight is obtained or until weight change is less than 4% of previous weight or 0.0005 g, whatever is less.

Calculating TSS

TSS concentration is calculated using the following equation:

TSS (\(\frac{mg}{l}\)) = \(\frac{(W~post~-W~pre~)}{V}\) x 1000

Where:

• W_post = dry weight of filter pad after filtering (g),
• W_pre = dry weight of filter pad before filtering (g)
• V = volume of water filtered (l)

Combusting filters for TVS measurement

Crucible preparation

1. After calculating TSS, transfer filter to a pre-combusted porcelain crucible stored prior to use in the circular desiccator or an aluminum weigh boat
2. To prepare crucibles, place 5 or more crucibles into the muffle furnace. Turn temperature to 550°C.
3. Bake out clean crucibles in the muffle furnace for several hours.
4. Turn the oven temperature to just below 200°C and slowly crack the door to allow crucibles to cool. Keep crucibles in the oven for another 30-45 minutes.
5. Remove crucibles that you need (the rest can stay stored in the muffle furnace) with Julian tongs.
6. Cool the crucibles in glass desiccators to remove moisture (~45 minutes).
   
7. Take desiccator over to weigh station. Put on gloves (oils on hands may change tare weight). Weigh the crucible (crucible mass) and then place sample in crucible.

Filter Combustion

1. Turn muffle furnace on. Let it come to 500◦C (this takes about 90 minutes). Add crucibles (or aluminum weigh boats) with filters and let them combust for 90 minutes.
   
2. Turn muffle furnace to 150 or move to a drying oven set to 150. Allow samples to come to 150◦C for about 1 h, then place in a desiccator. Allow sample to come to room temperature while in the desiccator.
3. Weigh crucible (or aluminum weigh boat) and record weight (in grams). Weigh over a few hours until the filter comes to a stable weight (within 0.0005g, or dependent on your accuracy needs).

Calculating TVS:

TVS (\(\frac{mg}{l}\)) = \(\frac{(W~post~-W~combust~)}{V}\) x 1000

Where:

• W_combust = dry weight of filter pad and sample after combustion (g)-crucible weight (g)
• W_post = dry weight of filter pad after filtering (g).
• V = volume of water filtered (l).

REFERENCES

• APHA. 1975. Method 208D. Total Nonfilterable Residue Dried at 103- 105 C (Total Suspended Matter) in Standard Methods for the Examination of Water and Wastewater, 14th Edition. American Public Health Association. Washington, D.C. 460pp.

• USEPA 1979 Method No. 160.2 (with slight modification) in Methods for chemical analysis of water and wastes. United States Environmental Protection Agency, Office of Research and Development. Cincinnati, Ohio. Report No. EPA-600/4-79-020 March 1979. 1193 pp.