John Henry Fair
Engineers at Newcastle St, Colorado Springs, CO

4111808, Sep 5, 1978

Mar 17, 1977

5/778793

John H. Fair - Colorado Springs CO

C02C 300

210197

Sludge digestion in a digester tank wherein the primary sludge is force fed into a vertically extending updraft tube mounted within the tank. The primary sludge is fed into the updraft tube at a position adjacent to the upper open end thereof whereas the gas lift employed for circulating the contents within the tank is introduced at a position adjacent to the lower end thereof with a portion of the conduit for the feed of the gas lift medium extending vertically within the updraft tube. A plurality of openings are provided in the updraft tube to allow for the flow of some of the digested sludge thereinto when the gases are fed under pressure into the updraft tube. The feed of the gases into the updraft tube not only serves to uplift the primary sludge fed thereinto, but also causes an unbalance in pressure between the contents in the digester tank and the interior of the updraft tube to then induce a flow of digested sludge into the tube and to there mix with the incoming primary sludge to thus seed the same before the combined primary and digested sludge are released within the digester tank.