Determination of Suspended Solids

GB1576—2001

A3 Determination of Suspended Solids

A3.1 Overview

Suspended solids are the solids separated from a water sample by a certain filter material. Different filter materials yield different results. This method uses a G4 glass filter or a Gooch crucible filter lined with a 5mm thick layer of asbestos as the filter material.

A3.2 Apparatus

A3.2.1 A G4 glass filter with a pore size of 3–4 μm or a 30 mL Gooch crucible.

A3.2.2 An electric vacuum pump or a hydraulic vacuum pump.

A3.2.3 A 2000 mL suction flask.

A3.3 Reagents

Nitric acid solution (1:1).

A3.4 Determination Method

A3.4.1 When using a G4 glass filter, first wash the filter with nitric acid solution, then wash it with distilled water, and then dry it in an oven at 105-110℃ for 1 hour. Remove it, cool it to room temperature in a desiccator, and weigh it to constant weight.

A3.4.2 Install the glass filter (or a Goower crucible lined with an acid-washed asbestos layer) on a suction flask and start the vacuum pump.

Note: Acid-washed asbestos can be prepared as follows: Cut high-quality long-fiber asbestos into 0.5cm lengths, mix with water in a mortar, then boil with concentrated hydrochloric acid in a water bath for 12-18 hours. Wash with hot distilled water until no chloride ions are present in the washings; then it is ready for use.

A3.4.3 If an acid-washed asbestos layer is used as the filter material, the acid-washed asbestos can be evenly spread across the bottom of the Goower crucible as follows.

A3.4.3.1 Place the acid-washed asbestos in a beaker, add a small amount of distilled water, and stir vigorously.

A3.4.3.2 Add a large amount of distilled water to the stirred acid-washed asbestos, stir again, and pour the turbid liquid containing the fine asbestos fiber suspension from the top into one beaker. Pour the longer asbestos fiber suspension that settles at the bottom of the beaker into another beaker.

A3.4.3.3 Place a clean Gooch crucible on a suction flask for filtration.

A3.4.3.4 Pour the prepared longer asbestos fiber suspension into the crucible and slowly filter by suction, pouring and filtering gradually until the acid-washed asbestos layer reaches a thickness of approximately 4 mm.

A3.4.3.5 Then pour in the fine acid-washed asbestos fiber suspension and filter, creating a cover layer of approximately 1 mm.

A3.4.3.6 Wash the prepared acid-washed asbestos layer with distilled water until the wash solution is clear. Dry the prepared Gooch crucible with the acid-washed asbestos layer in an oven at 105–110°C for 1 hour. Remove and cool in a desiccator, then weigh until constant weight is achieved.

A3.4.4 After thoroughly mixing the water sample, accurately measure the volume of the water sample according to Table A3 and slowly pour it into a glass filter. The initial 200 mL of filtrate should be filtered once more. The filtrate should be reserved for dissolving solids and for other analyses. If the filtered water sample is turbid, it should be filtered again.

A3.4.5 After filtration, rinse the container and glass filter used for measuring the water sample several times with a small amount of distilled water. Place the glass filter in an oven at 105–110℃ and dry for 1 hour. Remove it and place it in a desiccator, cool to room temperature, and weigh.

A3.4.6 Dry again at the same temperature for 0.5 hours, cool, and weigh. Repeat this process until a constant weight is achieved. The suspended solids content in the water sample is calculated according to formula (A1):

Where: G1—Total amount of glass filter (or Goohl crucible with asbestos layer) and suspended solids, mg;

G2—Weight of glass filter (or Goohl crucible with asbestos layer), mg;

V—Volume of water sample, mL.

A3.4.7 The filter material used should be specified in the test results report.