Patent ID: 6113788
Filing Date: 2000-09-05
Classification: C02F,Y02W,Y10S

Abstract:
A wastewater treatment process providing increased nitrogen, phosphate and biochemical oxygen demand removal comprising the steps of:(a) passing wastewater containing ammonia nitrogen, phosphate and biochemical oxygen demand through a main aerobic biological oxidation zone and therein oxidizing a portion of the ammonia nitrogen to nitrate nitrogen and at least a portion of the biochemical oxygen demand and converting at least a portion of the biochemical oxygen demand into suspended solids;(b) passing (i) effluent from the main aerobic biological oxidation zone and (ii) recycle sludge consisting essentially of anoxic/anaerobic-treated solids from the anoxic/anaerobic zone of step (d) directly to a single aerobic/mixing zone wherein the effluent and sludge are mixed under aerobic conditions;(c) passing effluent from the aerobic/mixing zone to a final settling zone and therein separating(i) a purified wastewater having decreased biochemical oxygen demand and a decreased phosphate and nitrogen content and(ii) a final sludge containing suspended solids and phosphate;(d) recycling at least a portion of the final sludge to an anoxic/anaerobic zone and treating it therein with at least one, non-wastewater solids produced volatile acid to release phosphate; and(e) passing effluent from the anoxic/anaerobic zone directly to the aerobic/mixing zone wherein phosphate is removed.