Abstract: A process for the purification of effluent, in which the effluent to be purified is first introduced into a high-loaded activation stage operated as an adsorption stage, then is passed through an intermediate clarifier with sludge offtake and subsequently introduced into a low-loaded stage to which a final clarification stage with sludge offtake is connected. Microorganisms work in the adsorption stage. The sludge is maintained in the initiation phase by means of the sludge takeoff from the intermediate clarification stage. Nitrification and subsequently denitrification can be carried out in the low-loaded stage. Sludge from the intermediate clarification stage can be reintroduced as recycled sludge into the adsorption stage, and sludge from the final clarification stage can be re-introduced as recycled sludge into the low-loaded stage. Also excess sludge is drawn off and thickened.

Abstract: A method of treating municipal and/or industrial sewage in a plurality of activation stages including a high-loading initial adsorption stage in which the biomass consists of procaryotae and make-up biomass in the form of procaryotae is introduced with the sewage in an amount per volume of one weight percent of the working biomass in the adsorption stage per unit volume to stabilize the treatment against pH shock, salt shock and toxic shock.

Abstract: A plant for the treatment of waste water, such as municipal sewage and industrial wastes containing organic matter which must be decomposed, comprises a mechanical clarifier for the removal of non-degradable and coarse contaminants, an activation vessel for a first digestion stage operating with an oxygen content close to 0 mg/l with facultative anaerobic operation, an intermediate clarifier, an aeration stage formed by a trickling filter for oxidative decomposition, an afterclarifier and an arrangement for removal and preferably the treatment of surplus sludge. An unaerated mixture (facultative anaerobic) basin is provided upstream of the afterclarifier in which water from the trickling filter is contacted with surplus sludge from the activation basin.