Ozonation as pre-treatment step for the biological batch degradation of industrial wastewater containing 3-methyl-pyridine

A combined chemical-biological treatment of industrial wastewater using ozonation as the first step of a Sequencing Batch Biofilm Reactor (SBBR) process, in which 3-methylpyridine (3MEP) was degraded as a model industrial pollutant, has been developed. The steps of the entire process were ozonation, heterotrophic degradation, denitrification and nitrification. An ozonation bubble-column reactor was used to produce biodegradable molecules, such as formate, acetate, ammonium or nitrate. These were then biologically degraded downstream in the biofilm reactors. The gas-liquid mass transfer coefficient (K(L)a=2.3*10(-3) (1/s)), the rate constant for the reaction of 3MEP with ozone (k(B)=6.63 (1/Ms)) and the surface tension were determined independently. The latter stayed almost constant through the whole batch ozonation (approximately sigma =72E-3 (N/m)). The process was limited by mass transfer during the first 80 minutes, when about 75 % of the initial pollutant was degraded. Only a small amount of the total consumed ozone reacted directly with 3MEP, while the rest reacted with the non-stable byproducts or was decomposed.