ALUMINIUM SULPHATE, powder, per kg

Coagulant used for treating turbid water. Coarse crystallic powder, possibly in lumps. Usually supplied in bags, can also be supplied in plastic barrels. Unit of measurement: 1 kilogram. Used in water treatment in particular in the coagulation - flocculation process.

Cake aluminium, Pickle aluminium, Filter aluminium, Papermaker's aluminium or Pearl aluminium.

Solid small granules of Aluminium Sulphate. Exists as well in (big) lumps, but these will have to be crushed in order to become dissolvable in water to form a 1% stock solution. These are white crystalline granules. They have the following properties:

Treatment of water

Normally used prior to chlorination of water, as a part of a process to reduce raw water turbidity: Aluminium sulphate solution is added to the raw water in a circular or onion-shape sedimentation tank, or for direct rapid sand filtration with the Water Treatment Unit. Assists sedimentation / rapid sand filtration through coagulation. Store in dry conditions. Mostly used in stock solution of 1%).

Choosing the correct coagulant depends on the raw water's pH. See in book "Public Health Engineering in Precarious Situations", MSF, 2nd edition, 2010, for more information, or contact your WHS technical referent if in doubt.

Certain water analyses should be made before using Al2(SO4)3: certainly pH (range of use: 6.0 till 7.4), turbidity, and preferably also conductivity, alkalinity (pH buffer effect) and temperature.​

For treating turbid water, a 1 % stock solution (or "mother solution") is used (10 g/litre).

This is made by diluting 10 x (100/18) = 56 g Al₂(SO₄)₃ granules (18% concentration) into 1 litre of water. The Al₂(SO₄)₃ granules will dissolve completely, although this might take some time and effort (e.g. shaking vigorously the solution's recipient).

The stock solution should be kept in an airtight, non-metallic container.

A jar test will have to be performed to determine the dosage needed. Transparent 1 litre beakers are ideal as the formation and finally the settling of flocs will be very visible. The quantity required for this small volume can then be extrapolated according to the volume of the big sedimentation tank or to the flow of raw water which is pumped into the sedimentation tank or through the Water treatment Unit. Once all flocs have settled (this takes several hours) or when the water has passed the Water Treatment Unit, it still needs to be chlorinated in a separate reservoir.

Attention: Residual Aluminium might provoke certain health risks if sedimentation times are too short and/or if the dosage is not correctly performed. Thus a residual aluminium test is strongly recommended and should preferably be under 0.2 mg/l.

For information on preparation of coagulation solution and its jar test, see:

"Public Health Engineering in Precarious Situations", MSF, 2nd edition, 2010:

• T.B. 2.14 Coagulants / flocculants
• T.B. 2.15 Jar test for coagulants

For information on water treatment methods based on coagulants, see:

"Public Health Engineering in Precarious Situations", MSF, 2nd edition, 2010:

• T.B. 2.16 Assisted batch sedimentation
• T.B. 2.17 Filtration methods

For information on water analysis to be done before and after the coagulant is used, see:

"Public Health Engineering in Precarious Situations", MSF, 2nd edition, 2010:

• T.B. 2.13 Turbidity measurement
• T.B. 2.22 Monitoring chlorination