Biological Nutrient Removal (BNR) reduces the amount of nitrogen and phosphorous discharged from water treatment plants. BNR is usually subdivided into:
· Nitrification – biological conversion of ammonia nitrogen into less harmful nitrate nitrogen.
· Denitrification – conversion of nitrate/nitrite nitrogen into nitrogen gas ~ this actually removes the nitrogen from the water.
· Biological Phosphorus Removal – certain microbial cells uptake phosphate in excess. These cells with high phosphate stored are wasted into biosolids, thereby removing phosphate from the water discharge.