🔬 Total Suspended Solids (TSS) Determination
Gravimetric determination of suspended solid particle concentration in water by vacuum filtration and drying. A fundamental wastewater quality parameter.
Overview
Total Suspended Solids (TSS) is a measure of the mass of solid particles suspended in water that are retained on a glass fibre filter of defined porosity. The result is expressed in mg/L.
TSS is one of the fundamental parameters for assessing water and wastewater quality. In municipal wastewater, typical values are 150–400 mg/L (raw) and <35 mg/L (treated). High suspended solids levels affect water turbidity, pollutant transport (heavy metals, pathogens, pesticides adsorbed onto particles), sedimentation processes, and riverbed siltation.
This parameter is mandatory in water permits, surface water monitoring, and wastewater treatment plant operational control. Standard PN-EN 872 is one of the most widely applied water analysis standards in Europe.
Method principle
Gravimetric method — a known volume of water sample is filtered through a pre-dried and pre-weighed glass fibre filter (GF/C, nominal porosity ~1.2 μm) under vacuum or pressure. The filter with residue is dried in an oven at 105±2°C to constant mass, cooled in a desiccator, and weighed on an analytical balance.
TSS [mg/L] = (m₂ – m₁) × 1000 / V
where m₁ — filter mass before filtration [mg], m₂ — filter mass after drying [mg], V — sample volume [L].
Applications
- Treated wastewater control (limit <35 mg/L)
- Surface water and groundwater monitoring
- Wastewater treatment plant operational control
- Drinking water testing (turbidity vs. suspended solids)
- Sedimentation and filtration process efficiency assessment
- Environmental studies — soil erosion, stormwater runoff
Key parameters
| Parameter | Value |
|---|---|
| Limit of quantification | 2 mg/L (at 1 L sample volume) |
| Measurement range | 2–20 000 mg/L |
| Filter porosity | ~1.2 μm (GF/C) or ~1.6 μm (GF/A) |
| Drying temperature | 105 ± 2°C |
| Weighing accuracy | 0.1 mg (analytical balance) |
| Repeatability | CV < 10% at concentration >10 mg/L |
Standard
- Standard number
- PN-EN 872:2007+Ap1:2007
- Title (PL)
- Jakość wody — Oznaczanie zawiesin — Metoda z zastosowaniem filtracji przez sączki z włókna szklanego
- Title (EN)
- Water quality — Determination of suspended solids — Method by filtration through glass fibre filters
Step-by-step procedure
1. Filter preparation
Place the GF/C filter on the filtration funnel, rinse 3× with deionized water (20 mL portions). Transfer to the drying oven.
2. Pre-drying
Dry the filter at 105±2°C for min. 1 hour. Cool in a desiccator for min. 30 minutes.
3. Filter weighing (m₁)
Weigh the filter on an analytical balance to 0.1 mg accuracy. Record the mass. Repeat drying and weighing until constant mass is achieved (difference <0.5 mg).
4. Sample preparation
Mix the sample thoroughly. Measure a known volume (typically 100–1000 mL, depending on expected concentration). For raw wastewater: 50–100 mL, for clean water: 500–1000 mL.
5. Filtration
Place the filter on the filtration assembly, moisten with deionized water. Filter the measured sample volume under vacuum (~500 mbar). Rinse the cylinder 3× with deionized water.
6. Residue rinsing
Rinse the residue on the filter with 3 portions of 10 mL deionized water — this removes dissolved salts.
7. Drying filter with residue
Transfer the filter to the drying oven at 105±2°C. Dry for min. 1 hour. Cool in a desiccator for min. 30 minutes.
8. Weighing (m₂)
Weigh the filter with residue. Repeat the drying–weighing cycle until constant mass is achieved (difference <0.5 mg between successive weighings).
9. Calculations
TSS [mg/L] = (m₂ – m₁) × 1000 / V [L]. Round the result according to the standard: <10 mg/L → to 1 mg/L, 10–100 → to 5, >100 → to 10.
10. Quality control
Blank sample: filter deionized water — m₂–m₁ ≤0.5 mg. Duplicate sample: RPD <15%.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Vacuum filtration assembly | Büchner funnel + filter flask + membrane pump, Merck Millipore | 2 000–5 000 PLN |
| Glass fibre filters GF/C | Whatman GF/C ø 47 mm (cat. 1822-047), Macherey-Nagel MN 85/90 | 200–400 PLN / 100 pcs. |
| Laboratory drying oven (105°C) | Binder FD 115, POL-EKO SLW 53, Memmert UF110 | 5 000–15 000 PLN |
| Analytical balance (0.1 mg) | Mettler Toledo ME204, Sartorius Entris II, Radwag AS 220.R2 | 5 000–15 000 PLN |
| Desiccator | Glass with silica gel or P₂O₅, ø 200 mm | 300–800 PLN |
| Measuring cylinders | 100, 250, 500, 1000 mL class A | 50–150 PLN/pc. |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Deionized water | — | For rinsing filters and vessels, conductivity <0.1 mS/m |
| Silica gel (desiccant) | 112926-00-8 | Desiccant for the desiccator, with moisture indicator (blue→pink) |
Health and safety (OHS)
- Drying oven at 105°C — burn risk, use thermal gloves
- Vacuum — exercise caution with glassware (implosion risk)
- Wastewater samples — potentially infectious, wear gloves and eye protection
- Glass fibre — do not inhale dust, do not handle with bare hands