Treatment of waste liquor in a vertical shaft bioreactor

Abstract

An improved apparatus for treating waste mixed liquor comprising a long vertical downcomer chamber; an adjacent long vertical riser chamber; a surface basin; said downcomer chamber and said riser chamber operatively communicating directly with each other at their lower ends and through said basin at their upper ends to form a circulatory loop; means for injecting an oxygen-containing gas in said downcomer and riser chambers at depth; a flotation-sedimentation vessel adjacent said surface basin; a first waste liquor influent conduit opening into said riser chamber at depth and operatively communicating with said vessel to provide a first waste liquor influent from said vessel to said riser chamber; a treated liquor effluent first conduit opening into said riser chamber and operatively in communication with said vessel to provide a treated waste liquor first effluent to said vessel from said riser chamber; the improvement comprising a treated waste liquor effluent second conduit having an inlet opening into said surface basin and operatively in communication with said vessel to provide a treated waste liquor second effluent to said vessel from said surface basin; and flow control and mixing means to operatively provide said treated waste liquor first and second effluents in such intimate mixing of said first and said second effluents as to cause heterogeneous bubble nucleation thereof and produce a nucleated liquor. The apparatus provides for improved flocculation, flotation and settlement of solids.