GB822749A - Improvements in or relating to the purification of sewage and industrial effluents - Google Patents

Abstract

822,749. Treating sewage &c. gravityseparation apparatus. FILTRATION CONSULTANTS Ltd. Oct. 28, 1957 [Nov. 14, 1956], No. 34766/56. Classes 46 and 111. A sedimentation tank for the purification of liquid sewage and industrial effluents comprises an imperforate baffle 12 mounted about a pipe 7 serving to introduce the liquid to the bottom of the tank from an inlet pipe 6. A mass formed from a coagulating agent or agents is introduced into the space below the baffle 12 through the spaces between the edges of the baffle 12 and tank sides and is then raised by inflowing liquid sewage to form a coherent blanket of thickness lying between levels xx and yy. A dish shaped baffle 16 prevents the inflowing liquid from flowing directly into a sludge pipe 8 which removes sludge to a drain 9. Liquid flows through the blanket and between the baffle 12 and tank sides, passing over a weir 5 into a channel 2 and thence through a pipe 4 to filter beds (not shown). Vent pipes 13 and 13a conduct away gaseous and liquid impurities respectively. The coagulating agent is prepared by adding sodium aluminate or lime to a solution of aluminium sulphate in water, the pH of the resultant aluminium hydroxide-containing mass being adjusted if necessary, in the latter case, by addition of more lime or aluminium sulphate. During operation, lime can be added to check putrefaction of impurities at the bottom of the tank, and blanket-forming material can be added to replace that removed with the sludge. Both are added through removable pipes (not shown). In the Provisional Specification the position of pipes 13 and 13a, and the shape of baffle 12, are modified slightly, and there is no baffle 16. Specification 780,630 is referred to.