Treatment of solids-liquid-gas mixtures

Claim 1

A method of treating a waste water mixture containing solid particles and biologically degradable material in apparatus including a basin, a downcomer, a riser operatively communicating with the downcomer both through the basin and at the lower end of the downcomer, and a floatation chamber operatively connected to the riser and extending upwardly therefrom, said method comprising the steps of continuously circulating the mixture contained in the basin-downcomer-riser system down said downcomer, up said riser, and back down said downcomer until sufficient treatment of the biologically degradable material is achieved, and supplying oxygen-containing gas to said downcomer so that said gas flows co-currently with mixture flowing down said downcomer, and upwardly with said mixture in said riser, at least some of the oxygen-containing gas being dissolved in said mixture: separating a portion of the upwardly moving mixture in the riser with dissolved gas contained therein from the mixture moving upwardly in the riser, by diverting it into the floatation chamber, at a first vertical level of the riser; and gradually decreasing the hydrostatic pressure on said separated portion to release gas from solution to form gas bubbles attached to solid particles present in said separated mixture portion and thereby effectively separate the solid particles from the liquid in the separated mixture portion to produce a floated solids-enriched mixture, wherein the improvement comprises hydrostatically feeding the floated solids-enriched mixture into the riser from the chamber at a second level, below said first level, the driving force for entry at the second level being provided by the lower relative density, as a result of its content of gas bubbles, of the mixture flowing upwardly in the riser.

Claim 2

A method of treating a waste water mixture containing solid particles and biologically degradable material in apparatus including a basin, a downcomer, a riser operatively communicating with the downcomer both through the basin and at the lower end of the downcomer, and a floatation chamber operatively connected to the riser and extending upwardly therefrom, said method comprising the steps of continuously circulating the mixture contained in the basin-downcomer-riser system down said downcomer, up said riser, and back down said downcomer until sufficient treatment of the biologically degradable material is achieved, and supplying oxygen-containing gas to said downcomer so that said gas flows co-currently with mixture flowing down said downcomer, and upwardly with said mixture in said riser, at least some of the oxygen-containing gas being dissolved in said mixture: separating a portion of the upwardly moving mixture in the riser with dissolved gas contained therein from the mixture moving upwardly in the riser, by diverting it into the floatation chamber, at a first vertical level of the riser; and gradually decreasing the hydrostatic pressure on said separated portion to release gas from solution to form gas bubbles attached to solid particles present in said separated mixture portion and thereby effectively separate the solid particles from the liquid in the separated mixture portion to produce a floated solids-enriched mixture, wherein the improvement comprises hydrostatically feeding the floated solids-enriched mixture into the riser from the chamber at a second level, below said first level, the driving force for entry at the second level being provided by the lower relative density, as a result of its content of gas bubbles, of the mixture flowing upwardly in the riser.