Efficient single-stage autotrophic nitrogen removal with dilute wastewater through oxygen supply control

► Efficient single-stage autotrophic nitrogen removal from dilute waster is possible. ► Over 90% total N removal by controlling oxygen supply to 0.75 mol O2/mol NH3 added. ► With this or less oxygen, nitrate formation held to 2% or less of ammonia removed. ► The efficient nitrogen removal obtained with 1 h HRT, 25 °C and 50 mg/L NH3-N. ► Autotrophic nitrogen removal requires little oxygen and no organics.