Waste water treatment with oxygen

A method of treating waste water having a BOD content of more than 10 ppm comprising the steps of mixing raw waste water with an activated biologically active mass at a waste metabolizing concentration of more than about 10,000 ppm of activated organisms in a mixing vessel without substantial oxygenation of the mixture in said vessel such that substantially no metabolism of the biologically active mass occurs in said vessel to form reduced BOD content water and a BOD-rich biologically active mass, said BOD-rich biologically active mass having adsorbed and absorbed BOD from said waste water, transferring the substantially non-oxygenated mixture to a clarifier to separate the BOD-reduced water from the BOD-rich biologically active mass, supplying an oxygen containing gas having an oxygen concentration of at least 30% by volume to at least a portion of the BOD-rich biologically active mass in a separate oxygenation vessel to metabolize the BOD-rich biologically active mass develop said activated organisms, and form said activated biologically active mass, and recycling said activated biologically active mass back to said mixing vessel to contact said raw waste water.

In a method of reducing the BOD content of BOD-containing waste water including the steps of mixing influent BOD-containing water with an effective amount of an activated biologically active mass, separating the resulting BOD-rich biologically active mass from the resulting reduced BOD effluent and oxygenating a substantial portion of the BOD-rich biologically active mass to provide the activated biologically active mass for mixing with the influent BOD-containing water, the improvement comprising;

• oxygenating a substantial portion of the BOD-rich biologically active mass in a separate oxygenation vessel with an oxygen-rich gas said gas having an oxygen concentration of at least 30% by volume to substantially completely metabolize said biologically active mass in said oxygenation vessel;
• and mixing the BOD-containing water with said activated biologically active mass in a mixed liquor vessel without substantially oxygenating the mixture such that substantially no metabolism of the biologically active mass occurs in said mixed liquor vessel and transferring the resulting mixture of BOD-rich biologically active mass and reduced BOD-content water to a separator.