Ozonation of wastewater containing N-methylmorpholine-N-oxide Original Research Article

Ozonation of synthetic wastewater containing N-methylmorpholine-N-oxide (NMMO) was investigated in batch experiments at different pH-values. Increasing pH caused higher initial elimination rates of NMMO as well as higher formation rates of nitrate. In mass transfer limited experiments, the shortest time needed for NMMO removal was observed at pH 7. This could be explained on the one hand through the importance of ·OH-radicals for the oxidation of NMMO and on the other hand through ozone decomposition reactions by ·OH-radicals at high pH-values. Dissolved ozone increased rapidly after elimination of NMMO at pH 7 and 8.5. High oxygen uptake rates of biomass with ozonation products showed the increase of the biodegradability compared to the initial synthetic wastewater. An improvement of ozone efficiency for elimination of NMMO and organic carbon can be expected in a process using a bioreactor in a recycle system.