Improvements in sewage treatment

摘要

690,939. Aerating sewage. GRIFFIN, J. D. May 11, 1950 [May 17, 1949], No. 11742/50. Class 111 Sewage is caused to flow upwardly under aerobic conditions through a tank at a rate permitting detention and digestion of sludge; digested sludge is withdrawn from the top of the detained body, and liquid is withdrawn either from the top of the liquid layer overlying the sludge or together with the sludge. Liquid withdrawn as such may be circulated through an aerobic biological unit and returned to the tank. Sewage enters a tank 2 through a pipe 3; some supernatant liquid is withdrawn by a pump 11 for flow through a trickling filter 8 whence it falls back into the tank, the remainder being withdrawn at 4 for final disposal or for additional purification in biological units. Sludge is digested during its upward flow and in the digested state overflows into a funnel 5 from which it passes to a drying bed 1. The effluent from the bed 1 may be added to the incoming raw sewage as shown. In a modification, not shown, the filter 8 and tank 2 are separate, the effluent from the filter 8 discharging at substantially the top liquid level across the tank 2. Humus falls through the liquid zone to be retained in the sludge below. The effluent from the bed 1 may be used without further treatment for example for irrigation purposes. Aeration of the tank charge may be assisted by using any of the conventional devices.