Companies have been looking for new methods for treating toxic or refractory wastewaters; which can mainly be used prior to or after or in connexion with biological treatment processes. This paper compares conventional ozone oxidation with activated carbon (AC) promoted ozone oxidation, which helps developing a mechanism involving HO radical. For a compound which is quite easy to oxidise, like 2, 4-dichlorophenol (2, 4-DCP) conventional ...