Automatically operable two stage biological compact clearing installation

Claim 1

An automatically operating two-stage aerobic biological compact clearing installation, which includes: a single container open at the top and having a substantially cylindrical inner cross section, partition means subdividing the interior of said container into a plurality of coaxial compartments arranged one within the other, the outermost one of said compartments representing the first compartment and comprising an upper section forming a pre-activating chamber and also cOmprising a lower section in shunt arrangement with regard to said upper section and forming a digesting chamber, influent means delivering liquid to be purified to said pre-activating chamber, the compartment within and next to said first compartment representing the second compartment and forming an activating chamber, and a third compartment next to and within said second compartment forming a post-clearing chamber, said first and second and third compartments communicating hydrostatically with each other so as to permit a trouble-free unimpeded flow of waste water through said compartments, venting and conveying means arranged in the upper portion of said container, driving shaft means common to said venting and conveying means for driving the same, said venting means being adapted separately to introduce air at the water surface into said pre-activating chamber and said activating chamber and to generate a uniformly directed water flow in the circumferential direction of said container, and said conveying means being adapted automatically and separately to convey return sludge from the lower range of said post-clearing chamber into said activating chamber and also to convey excess sludge from said activating chamber into said preactivating chamber, and furthermore to convey floating sludge from the upper range of said post-clearing chamber into said preactivating chamber, means for controlling the quantity of excess sludge being conveyed from said activating chamber to said preactivating chamber, and means for discharging clear effluent from said third compartment.