PRENITRIFICATION AND SEEDING FOR ENHANCED NITRIFICATION

A prenitrification basin and seeding approach are proposed for the Lincoln, Nebraska Theresa Street Wastewater Treatment Facility to enhance nitrification capacity. The existing facilities do not have sufficient capacity for nitrification of the ammonia to permitted levels. The prenitrification basin will be used for treatment of high strength recycle streams from solids processing operations. These streams, occurring intermittently, recycle approximately 36 percent of the ammonia received at the facility. Process models indicate overall treatment basin volume will be reduced with the addition of the prenitrification basin. Recycle streams will be combined with a portion of return activated sludge in the aerated prenitrification basin resulting in a decrease of ammonia from over 500 mg/l in the recycle to 10 to 30 mg/l prior to combining with the main plant flow. The prenitrification basin will also:result in higher temperatures for nitrifier growthprovide an enriched source of nitrifying organismseliminate the need to grow nitrifiers for recycle treatmentreduce shock loads from recycle streams