Ultrapure Water Applications - Determination of Suspended Solids in Water - Gravimetric Method

GB 11901-89

Water quality－Determination of suspended substance Gravimetric method

1. Subject Matter and Scope

This standard specifies the determination of suspended solids in water.

This standard applies to surface water, groundwater, and also to the determination of suspended solids in domestic sewage and industrial wastewater.

2. Definition

Suspended solids in water refer to substances that remain on a 0.45 μm pore size filter membrane after a water sample is passed through it and dried to constant weight at 103–105 °C.

3. Reagents

Distilled water or water of equivalent purity.

4. Instruments

4.1 Commonly used laboratory instruments and the following instruments.

4.2 All-glass microporous membrane filter.

4.3 GN-CA filter membrane, 0.45 μm pore size, 60 mm diameter.

4.4 Suction flask, vacuum pump

4.5 Toothless flat-tipped forceps.

5. Sampling and Sample Storage

5.1 Sampling

The polyethylene bottle or hard glass bottle used must be washed with detergent. Rinse thoroughly with tap water and then distilled water. Before sampling, rinse three more times with the water sample to be collected. Then, collect a representative water sample of 500–1000 mL and tightly stopper the bottle.

Note: Floating or submerged heterogeneous solids are not considered suspended matter and should be removed from the water sample.

5.2 Sample Storage

The collected water sample should be analyzed as soon as possible. If storage is necessary, it should be stored in a refrigerator at 4°C, but not for more than seven days.

Note: Do not add any preservatives to prevent disruption of the solid-liquid distribution equilibrium.

6. Procedure

6.1 Filter Membrane Preparation

Use flat-tipped toothless tweezers to pick up the microporous filter membrane and place it in a pre-weighed weighing bottle. Place it in an oven at 103–105°C and dry for half an hour. Remove it and cool it to room temperature in a desiccator, then weigh it. Repeat the drying, cooling, and weighing process until the weight difference between two weighings is ≤0.2 mg. Place the constant-weight microporous membrane correctly on the filter tray of the membrane filter (4.1), cover it with the matching funnel, and secure it with clamps. Moisten the membrane with distilled water and continuously aspirate.

6.2 Determination

Measure 100 mL of the thoroughly mixed sample and aspirate to filter it. Ensure all water passes through the membrane. Wash three times consecutively with 10 mL of distilled water each time, continuing aspiration to remove trace amounts of water. After stopping aspiration, carefully remove the membrane containing the suspended solids and place it in the original constant-weight weighing bottle. Dry it in an oven at 103–105°C for one hour, then transfer it to a desiccator to cool to room temperature and weigh it. Repeat the drying, cooling, and weighing process until the weight difference between two weighings is ≤0.4 mg.

Note: Excessive suspended solids retained on the membrane may trap too much water, prolonging drying time and potentially causing filtration difficulties. In such cases, reduce the sample size accordingly. Insufficient suspended solids on the filter membrane will increase weighing error and affect measurement accuracy. If necessary, the sample volume can be increased. Generally, a suspended solids content of 5–100 mg is considered a practical range for sample volume measurement.

7. Expression of Results

The suspended solids content C (mg/L) is calculated using the following formula:

Where: C—Suspended solids concentration in water, mg/L;

A—Weight of suspended solids + filter membrane + weighing bottle, g;

B—Weight of filter membrane + weighing bottle, g;

V—Sample volume, mL.

Additional Notes:

This standard was technically proposed by the Standards Division of the State Environmental Protection Administration.

This standard was drafted by the Yantai Environmental Monitoring Center.

The main drafters of this standard are Li Changhai and Wang Wenfa.

This standard is entrusted to the China National Environmental Monitoring Centre for interpretation.