Proposed is an installation for the biological treatment of wastewater using activated sludge, said installation containing, connected in sequence, a plurality of denitrification units, a nitrification unit and a membrane treatment unit, an activated sludge vacuum degassing unit based on an "aeroclean" installation, a reagent unit, a system for recirculating activated sludge from the membrane treatment unit into the denitrification unit, auxiliary equipment and pipelines.

The invention relates to a device for cleaning the outer shell of two immersion tubes or nozzles that are arranged next to each other and lowered into the melt of vacuum degassing units for the treatment of the liquid aluminum, comprising a spectacle-like scraper ring that is adapted to the contour of the nozzle pair, can be placed against the outer shell thereof and has wiper means such as teeth, bits, peripheral closed sheet metal construction or the like.

The concentrate from the second membrane separation stage and concentrate exiting from the electrode ionization unit are degassed in a degassing device and fed to the first membrane separation device.