Process and apparatus for the clarification of liquids

Claim 2

A process as claimed in claim 1 in which the number and size of the settling units in the secondary set is such that the liquids content of the liquid/sludge suspension at the level of the bottom of the settling units of the primary set compared with the liquids content of the suspension at the level of the bottom of the settling units of the secondary set is reduced by a factor of about 2.

Claim 3

A clarifier comprising a tank having means for supplying liquid to be clarified near its top and a sludge-collecting bottom with means for withdrawing sludge therefrom, a set of separate primary settling units adapted to be operatively positioned within an upper part of the tank and individually removed therefrom, and a set of separate secondary settling units adapted to be operatively positioned within a lower part of the tank below the primary set but above the sludge-collecting bottom and individually removed therefrom, each settling unit comprising a multiplicity of sharply inclined conical members mounted upon a central pipe in closely spaced superposed relation, the inclination of said members being outwardly and downwardly with respect to the associated central pipe with the outer peripheries of the members terminating short of the tank wall, when operatively positioned therein, to provide a vertical settling channel surrounding the superposed members of each settling unit, the central pipe of each settling unit having openings intermediate the apexes of each pair of adjacent conical members mounted thereon, and means for withdrawing clarified liquid from said central pipes when the settling units are operatively positioned within the tank.

Claim 4

A clarifier as claimed in claim 4, in which the central pipes of the primary set of settling units lead into the same collecting vessel as the central pipes of the secondary set of settling units.

Claim 5

A clarifier as claimed in claim 4 in which the sludge-collecting bottom of the tank is of frusto-conical shape sloping downwardly to a central outlet for sludge, the tank including a movable scraper which removes sludge from the sloping wall of the sludge-collecting bottom and encourages it to fall into the outlet.

Claim 6

A clarifier as claimed in claim 4, in which the secondary set of settling units are positioned relative to the primary set so that the central pipes of each run vertically up through the tank.

Claim 7

A clarifier as claimed in claim 4, in which the settling units in the secondary set are shorter than the settling units in the primary set.

Claim 8

A clariFier as claimed in claim 8, in which the settling units in the secondary set are of smaller cross-sectional size, in planes normal to the central pipe, than the settling units of the primary set.

Claim 9

A clarifier as claimed in claim 4, in which each central pipe is open at the top at a level above the normal liquid level in the tank and is provided with a valve-controlled outlet extending from the pipe a short distance below the open top.