Method for the froth flotation separation and treatment of slowly biodegradable components in waste treatment

Claim 1

In a modified activated sludge waste treatment method wherein an aerobic biological reaction takes place during the continuous circulation of fluid waste in an apparatus comprising a surface basin, a long vertical downcomer chamber, a long vertical riser chamber operatively communicating with the downcomer through the basin and at the lower end of the downcomer to form a circulating loop and including means to circulate waste liquor through said loop in the presence of oxygen-containing gas, the improvements whereby the slowly biodegradable components of the waste may be separated from the waste liquor in the loop, aerobically treated, and after treatment returned to the waste liquor in the loop, comprising the steps of: (a) introducing waste liquor from a single source into the said riser chamber of the said loop, (b) adding oxygen-containing gas to the waste liquor in the said riser chamber to lift said waste liquor for circulation through said loop and to provide oxygenation of the said waste, (c) collecting from the surface of said waste in the said surface basin any foam containing slowly biodegradable materials together with activated sludge, which foam has been produced by stripping the supersaturated dissolved gases ascending from depth in the said circulating loop by the action of the said added oxygen-containing gas in the said riser, (d) separating said foam and contained slowly biodegradable materials and activated sludge from the surface of the liquid waste in the said basin and transferring said foam and contained materials to a foam oxidation vessel, (e) aerating said foam in said foam oxidation vessel to produce further biodegraded liquid and solids mixture, and (f) returning the said further biodegraded liquids and solids mixture from step (e) to the circulating waste in the said loop via step (a).