Critical role of oxygen for rapid degradation of organic contaminants in permanganate/bisulfite process. 
Organic contaminants can be oxidized rapidly in permanganate/bisulfite (PM/BS) process due to generation of Mn(III)aq.  However, the influence of O2 and its role in contaminants degradation in PM/BS process are poorly understood.  Thus, the influence of O2 concentration on phenol removal was quantified and isotopic oxygen tracers (18O-labeled water and 18O2) were employed to further unravel the mechanisms of PM/BS process.  The introduction of O2 to PM/BS process appreciably improved phenol oxidation.  Under oxic conditions the oxidation products of bisulfite included SO42- and HSO5- while SO42- was the single stable oxidation product under anaerobic conditions.  The oxygen isotope labeling experiments confirmed that HSO5- originated from the oxidation of SO3- by O2 to SO5- and the following reduction of SO5- by HSO3-.  Incorporation of oxygen isotope from H218O to MnO2 due to the disproportionation of Mn(III)aq was observed, which verified the generation of Mn(III)aq in PM/BS process.  The critical influence of O2 on PM/BS process was mainly associated with rapid oxidation of SO3- by O2 to SO5-, which otherwise competed with target contaminants for Mn(III)aq.  Oxygen from H2O and/or O2 can also be incorporated in the degradation products of organics in PM/BS process.