METHOD FOR SEWAGE TREATMENT Russian patent published in 1998 - IPC

FIELD: environmental control; treatment of both industrial and household sewage. SUBSTANCE: sewage is treated by subjecting it, in succession, to gravity sedimentation, flotation and filtering. Flotation treatment is carried out by organizing forced (artificial) coalescence of microbubbles. For this purpose, saturated solution of some gas easily soluble in water, such as, e. g. carbon dioxide or hydrogen sulfide, is injected into sewage. This effect is also achieved by placing hydrophobic surface on path of travelling gas bubbles. Microbubbles not trapped by clarified water coalesce as they enter filtering charge (bed) constituted by particles of carbon and peat, the latter being normally represented by high-moor peat flotation concentrate. Froth product obtained by flotation stage and froth cake obtained by filtering stage are combined together and directed to separation by decantation into light and heavy fractions, the latter being recycled back to gravity sedimentation stage. EFFECT: higher efficiency. 9 cl