NITRIFICATION AND OXYGEN UTILIZATION IN A MEMBRANE AERATION BIOREACTOR

A laboratory-scale membrane aeration bioreactor (MABR) was operated wi th a nitrifying biofilm attached to the surface of oxygen-permeable ho llow fibres. Pure oxygen was supplied to the biofilm via the lumen of the hollow fibres. The process achieved high rates of nitrogen removal (98%) and nitrification (83%) at a nitrogen loading rate of 1.2 kg NH 4-N m(-3) d(-1). A specific nitrification rate of 5.4 g NH4-N m(-2) d( -1) and a nitrogen removal rate of 6.6 g NH4-N m(-2) d(-1) were demons trated. Nitrification was virtually unaffected by a reduction in the o xygen supply rate up to the point where the supply matched the oxygen requirement of the wastewater. Exceptionally high oxygen utilisation e fficiencies were achieved. It is proposed that interfacial oxygen mass transfer contributes to the excellent performance of the MABR at low oxygen supply rates. (C) 1998 Elsevier Science B.V.