Sewage purification treatment

Claim 1

A PROCESS EMPLOYING TRICKLING FILTER MEANS FOR TREATING SEWAGE AND OTHER AQUEOUA WASTES CONSISTING IN SUPPLYING AN INFLUENT OF SAID MATERIAL TO A PRIMARY CONECT BY SEDIMENTATION IN ADVANCE OF THE TICKLING FILTER, INTERMIXING WITH THE FLOW BETWEEN THE PRIMARY CLARIFICATION AND THE TRICKLING A SUPPLY OF TREATED MATERIAL RECIRCULATED FROM A LATER STAGE OF THE PROCESS FOLLOWING TREATMENT OF THE MATERIAL BY BIOLOGICAL OXIDATION MAINTAINED AT A DISSOLVED OXYGEN CONTENT OF AT LEAST TWO PARTS PER MILLION AND SIMULTANEOUSLY WITH SAID SUPPLY OF TREATED MATERIAL INTRODUCING AND INTERMIXING WITH THE FLOW FROM THE PRIMARY CLARIFICATION TO THE TRICKLING FILTER AN AERATING SUPPLY OF OXYGEN-CONTAINING GAS, SUBSEQUENTLY SUBJECTING THE CLARIFIED MATERIAL WITH A GRADUALLY INCREASED SURFACE EXPOSURE TO A FURTHER SUPPLY OF AERATING OXYGEN-CONTAING GAS IN A TRICKLING FILTER RAISING THE DISSOLVED OXYGEN CONTENT FURTHER ABOVE SAID TWO PARTS PER MILLION FR A CORRESPONDINGLY INCREASED BIOLOGICAL OXIDATION, DRAWING OFF A PORTION OF THE EFFLUENT FROM SAID TRICKLING FILTER SAID PASSING SAID PORTION BACK FOR RECIRCULATION AS SAID SUPPLY OF TREATED MATERIAL FOR MIXTURE WITH SAID FLOW AT A POINT SUBSEQUENT TO SAID PRIMARY CLARIFICATION AND BETWEEN SAID PRIMARY CLARIFICATION AND SAID TRICKLING FILTER, AND CONTINUING SAID TREATMENT OF THE MATERIAL UNDER BIOLOGICAL OXIDATION IN THE PRESENCE OF A DESIRED OXYGEN CONTENT OF AT LEAST TWO PARTS PER MILLION.