Biological process for enhanced removal of ammonia, nitrite, nitrate, and phosphate from wastewater

摘要

A method is disclosed for attaining concurrent biological nitrification and dentrification in an aerobic zone of an activated sludge treatment plant. The method comprises aerating a mixed liquor in an aerobic stage of a secondary treatment zone to attain nitrification of ammonia values to NO.sub.x, transferring the mixed liquor to a settling zone where activated sludge is allowed to settle from the mixed liquor, transferring at least a portion of the sludge to an anaerobic sludge holding zone where it is held for a prolonged period, and returning the aged sludge from the sludge holding zone to the secondary treatment zone for mixing with influent wastewater. By holding the sludge in the sludge holding zone for a prolonged period, a culture of organisms is developed which exhibits an oxygen respiration block in the presence of NO.sub.x. When returned to the aerobic zone where nitrification is achieved, these organisms utilize the NO.sub.x being formed as an electron acceptor to metabolize sorbed BOD and to discharge the respiratory block. The result is concurrent biological nitrification and denitrification in the aerobic zone.