A major disadvantage of ozone diffusers is that they are easily
clogged with suspended solids and precipitates, which is why O3 often is injected with side
stream injectors. Side injections facilitate higher mixing efficiency, but can at same time lower
the contact times, resulting in poor gas diffusion. The transfer efficiency of O3 in aqueous phase
is generally increased with smaller bubble sizes (bigger interfacial area) and longer contact times
between O3 and the effluent. Continuous ozonation is needed due to the short half-life of O3,
and static mixers are sometimes incorporated into the reactor to increase the transfer
efficiencies of O3 in the liquid (Gogate and Pandit, 2004a).