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: The invention relates to a method for obtaining protein-containing animal feed from organic substances dissolved and/or suspended in water, where the substances are biologically processed in at least two series-connected stages (I, II) each having an activating tank (5, 7) and a settling tank (6, 8). In the first stage (I) a larger percentage of bacteria than protozoea prevails. The sludge is drained intermittently and alternatingly from the first and second stage (I, II), and conducted to a dehydrating device (9), and a part of the dehydrated sludge is returned to the input (5a, 7a) of that stage from which the sludge was taken. Into at least one of the activating tanks (5, 7), especially into the activating tank (5) of the first stage (I), additives promoting the growth of the micro organisms, especially trace elements and/or minerals, are placed.