Double-layered compacted solid water-purification product

A process for the preparation of a compacted solid product for the purification of water comprising at least one first layer and at least one second layer, wherein the process comprises the following stages:

• a) mixing at least one flocculating system and at least one disintegrating system in powdered form;
• b) mixing at least one disinfectant in powdered form, which releases active chlorine on contact with water, and at least one excipient for the disinfectant, the excipient releasing the disinfectant into the water at a controlled rate such that the excipient-disinfectant combination releases from 0.1 to 100 mg/l of active chlorine per hour;
• c) precompacting the mixture obtained in b) in a pelleting machine;
• and
• d) adding the mixture obtained in a) to the pelleting machine and the combined mixture is compacted in order to obtain a two-layer product,
• the flocculating system comprises at least one trivalent metal salt and at least one water-soluble cationic polymer, and
• the at least one water-soluble cationic polymer is present in a volume of water to be treated at a content ranging from 1 to 2 ppm.