Method and device for purification of effluent

A method for purification of effluent, in particular effluent from the paper industry, comprising the following process steps:

• a) aerobic clarification of the effluent through activated sludge in an activated-sludge tank;
• b) settling of at least a portion of the effluent/activated-sludge mixture exiting the activated-sludge tank in a settling tank;
• c) dehydrating in a dehydration unit a portion of the effluent/activated-sludge mixture exiting the settling tank and a portion of the activated sludge settled in the settling tank;
• d) feeding back at least a portion of the activated sludge settled in either or both steps b) and c) into the activated-sludge tank.

A device for the purification of effluent, in particular effluent from the paper industry, comprising:

• an activated-sludge tank to receive a mixture of activated sludge and effluent for the aerobic clarification of the effluent;
• a settling tank for solid/liquid separation of the activated-sludge/effluent mixture;
• and
• a dehydration unit for dehydration of the effluent/activated-sludge mixture and of the activated sludge, wherein the settling tank and the dehydration unit are hydraulically coupled so that either or both the effluent/activated-sludge mixture from the activated-sludge tank and from the settling tank as well as the activated sludge settled in the settling tank can be fed to the dehydration unit.