Hoss' 4-stage biological nutrient removal (BNR) activated sludge process for removal of total phosphate and total nitrogen to a level below 1.0 mg/l without any chemical coagulation process such as alum or ferric chloride used for phosphorous removal

A biological nutrient removal (BNR) suspended waste activated sludge treatment process to treat a municipal wastewater, said process comprising the steps of:

• a. Flowing screened and de-gritted municipal plant wastewater influent containing nitrogen and phosphorus through four main stages directly interflowing of anaerobic, oxic (aerobic), anoxic, and re-aeration zones prior to clarification in a clarifier having a weir and
• b. Recycling internal mixed liquor suspended solids from the end of the aerobic (oxic) zone to the anaerobic zone and return activated sludge returning from the clarifier underflow to the anaerobic zone with a portion diverted to the anoxic zone for a carbon source and
• c. Producing a liquid effluent from the weir of the clarifier having less than 1.0 mg/l of total phosphorus and 1.0 mg/l of total nitrogen without any coagulant chemical additions.