NITROGEN AND PHOSPHOROUS REMOVAL FROM WASTEWATER

ABSTRACT OF THE DISCLOSURE Wastewater is passed sequentially through an anaerobic treating zone and an oxic treating zone, followed by separation from the treated liquor of a dense sludge containing activated biomass, a least part of which is recycled to provide the activated biomass employed in treating the influent wastewater. Of the part of the sludge so recycled a minor portion is introduced into the anaerobic treating zone for admix-ture with the wastewater influent and the remaining major portion is introduced into the oxic treating zone, into which oxic zone oxygen-containing gas is admitted to effect oxygenation of the contents of that zone.