and means the necessity to drive the oxidation for biodegradability
improvement to the detriment of mineralization. It is worth noting
that the 50 min reaction time corresponded to a very remarked
inflexion of the O3(applied) yield (corresponding to 73.9% for
50 min) decline. In addition, as the ozonation time increases from
20 min to 80 min, the rise of BOD5/COD is increasingly slow, even
presenting a drop during the ozonation time from 60 min to
80 min. This demonstrated that extending contact time for BTCM
ozonaton is not always positive in improvement BOD5/COD. Therefore,
the 50 min contact time selected in present study was
reasonable.