Importance

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Abstract

A method of pretreating raw water, for instance sea water, which is intended for supplying reverse osmosis units. An aqueous solution of acid salt and acid with the same anions is mixed with the raw water, whereby the most advantageous pH value is adjusted for the reverse osmosis, and whereby the acid salt is converted into the corresponding hydroxide. After possible addition of flocking or flaking additives, the resulting hydroxide flakes are separated, in a strongly concentrated form, by way of a centrifuge, particularly a plate or disc centrifuge, and together with fresh metal salt, are again brought into solution as a salt by means of the previously mentioned acid and, after mechanical purification in a second centrifuge, likewise particularly a plate or disc centrifuge, are again supplied to the raw water. The pretreated raw water leaves under pressure from the separator through which it flows and, alternatively, a chemical reducing agent may be added to this departing water flow. With a small requirement for metal salts, the recirculation can be eliminated. Also, the addition of the reducing agent to the pretreated raw water can be eliminated.

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First Claim