초록

In activated sludge-type wastewater treatment, nitrified oxygenated liquid-solid from the oxic zone is retained under anoxic conditions for denitrification and release of nitrogen gas, and the denitrified liquid-solid returned to the oxic zone.

대표청구항 ▼

In the purification of wastewater by the activated sludge method in which wastewater containing nitrogenous compounds is mixed in an oxic zone in the presence of carbonaceous compounds with oxygen-containing gas and activated sludge containing carbon-consuming and nitrogen-oxidizing bacteria for suf

In the purification of wastewater by the activated sludge method in which wastewater containing nitrogenous compounds is mixed in an oxic zone in the presence of carbonaceous compounds with oxygen-containing gas and activated sludge containing carbon-consuming and nitrogen-oxidizing bacteria for sufficient duration to nitrify the nitogenous compounds and form nitrified oxygenated mixed liquor which is discharged from the oxic zone and passed to a separate zone to effect concentration of solids from liquor with at least a major part of the concentrated solids being returned to said oxic zone as said activated sludge such that the total mean residence time of solids (SRT) is at least two days, the improvement comprising withdrawing and introducing nitrified oxygenated liquid-solid to an anoxic zone at volume flow rate less than one-half the volume flow rate of nitrified oxygenated mixed liquor entering the solids concentration zone, maintaining said nitrified oxygenated liquid-solid in said anoxic zone under anoxic conditions for a period between 0.4 and 36 hours and sufficient to denitrify the liquid-solid and form nitrogen-containing gas, releasing said nitrogen-containing gas and returning the denitrified liquid-solid to said oxic zone.