Abstract: A mixed culture reactor biologically removes organic pollution and nitrates by the anoxic route. The reactor includes a central stirred section having a lower part in which biological treatment of supplied raw water takes place. The central reactor section contains a suspension of an attached biomass of low concentration, in the order of a few grams per liter. At least one propelling screw is positioned within a jacket that is coaxially located in the reactor central section to ensure the circulation of the water to be treated. The water to be treated circulates in one direction within the jacket and in an opposite direction outside the jacket. The speed of circulation is selected so that bioparticles remain in suspension within the reactor central section. A release zone is located externally of the reactor central section and communicates with a lower part thereof.

Abstract: Process for the treatment of liquid effluents, such as waste water, for the purpose of removal of carbon, nitrogen and phosphorus pollution using an activated sludge, according to which the effluent, after having been subjected to mechanical pretreatments, is brought into contact with the activated sludge. The effluent/activated sludge mixture is the subjected to clarification/settling in order to separate the treated water from the thickened sludge, the latter then being recycled at the head of the aeration treatment and the excess sludge being continuously discharged. An inert material of inorganic origin is injected into the activated sludge, this material being immediately and homogeneously dispersed in the activated sludge, in order to create a mixed culture containing both, and in a single bacterial floc, free heterotrophic species and autotrophic species partially fixed on the particles of the said material within the floc.

Abstract: Process for the biological treatment of water using a biological reactor containing a culture of microorganisms, immobilized on a granular support material, according to which an expendable powdery material is injected into the said reactor, said process being performed so as to ensure a self-selection and a self-regulation of the support material of the particle size necessary for the biological process.