Process and reactor for water treatment using a granular bed adapted to float during cleaning

A process for the treatment of water using a granular bed of granular materials (3) arranged in a reactor above a platform (2) in the reactor, the granular bed (3) being adapted to carry out a simple filtration treatment or filtration treatment in combination with an associated biological purification of water, said process comprising carrying out water treatment cycles through said granular bed (3) alternated with bed washing cycles, each treatment cycle being carried out while feeding the water to be treated from above the granular bed (3) and withdrawing the treated water from beneath the granular bed, said granular bed (3) comprising granular support materials having a volumic mass less than that of the water to be treated,

• each washing cycle comprising interrupting the withdrawal of treated water and stopping the feeding of treated water so that the granular bed (3) floats in a given volume of water VL,
• admitting washing air into the reactor for assuring an agitation of the floating bed,
• interrupting the admission of air for permitting a separation of the granular materials and the sediment (12) according to the difference in volumic mass, with settling of said sediment and flotation of said materials,
• evacuating the sediment from the bottom of the reactor with the water contained in the reactor thereby emptying the granular bed (3) for a new treatment cycle.