PROCESS AND APPARATUS FOR THE BIOLOGICAL PURIFICATION OF WASTE WATER

A process for the biological purification of effluent which is contaminated with nitrogen in the form of ammonium, nitrite or nitrate ions or in the form of organic compounds, by oxidizing the nitrogen under aerobic conditions and reducing the nitrogen under anaerobic conditions, wherein the sewage to be treated, mixed with activated sludge, is subjected, in an aeration basin, to oxygen-containing gas bubbles introduced from below and is thereby simultaneously enriched with dissolved oxygen, to oxidize carbon compounds and nitrogen compounds, and transported upward, by the buoyancy of the gas bubbles, releases gas at the surface of the liquid and, due to the higher average density of the mixture of lower gas content, in part automatically again flows downward in the aeration basin, to undergo further aeration, while in part it overflows into a denitrification basin which communicates with the aeration basin through an opening at the liquid surface, and an opening at the bottom of the partition, is mixed, in the denitrification basin, with the contents thereof by mechanical means and flows back, through an opening near the bottom, in the partition, to the aeration basin. The invention further relates to an activated sludge basin, wherein jet aerators are arranged parallel, and horizontally, at the bottom of the basin, a vertical partition divides the basin into an aeration compartment and a denitrification compartment, both compartments possessing jet aerators, and passages in the partition connect the two compartments of the basin in the area of the surface of the liquid, and in the vicinity of the bottom.