3-Methylpyridine (MP) and 5-ethyl-2-methylpyridine (EMP) were quantitatively removed in batch ozonation. Formate, acetate and oxalate where detected as ozonation products representing only about 10% of the total organic carbon after 90% removal of MP. Only 30% of the nitrogen was detected as nitrate. 5 moles of ozone were needed per mol of MP removed but at this time dissolved organic carbon (DOC) was only reduced by 10%. EMP was initially oxidised much faster but the reduction of DOC was only 5% when EMP was removed by 90%. Only 15% of the nitrogen was converted to nitrate. Small amounts of formate, acetate and oxalate were accumulated. 4 moles of ozone were required to remove one mole of EMP. In continuous combined experiments, wastewater was fed to a fluidised bed biofilm reactor with a mixed culture. The liquid was circulated through an ozonation bubble column. Ozone supply was controlled to keep the dissolved ozone concentration at a low level in the oxidation reactor. Complete mineralisation of MP and extensive mineralisation of EMP was observed during the whole experiment. During adaptation of biomass the ozone requirement decreased from 10 mol mol−1 of MP oxidised to 4 mol mol−1.

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