As a result of its high inert COD content (approximately 250 mg/l accounting for 63% of the total COD) and the possibility to evoke antibiotic resistance, Ceftriaxone sodium antibiotic formulation effluent (molecular formula = Ci(8)Hi(6)N(8)Na(2)O(7)S(3)) requires an additional treatment process preferably as chemical pretreatment along with the biological one to meet the discharge standards. The present study dealt with the effect of applying ozonation and the H2O2/O-3 process (perozonation) as a partial pretreatment stage to the mentioned antibiotic formulation effluent. 20 min of ozonation at a rate of 1500 mg/(l.h) removed 48% COD, whereas a COD removal efficiency of 53% could be achieved via perozonation in the presence of 31 mM H2O2. Ozonation completely eliminated the inhibitory effect of the effluent towards activated sludge, however at the same time it also resulted in an increase in acute toxicity towards the marine microalgae Phaeodactylum tricornutum. On the other hand, by perozonation a considerable reduction in the inhibitory effect of the studied effluent towards heterotrophic biomass was achieved, unfortunately perozonation also increased the toxicity of the effluent towards the marine microalgae.