The effect of O-3 (applied dose = 1440 mg h(-1); pH 7 and pH 12) a rid H2O2/O-3 (applied dose = 1440 mg h(-1); pH 7; 10 mM H2O2) pretreatment of procaine penicillin G (PPG) formulation effluent on its biodegradability and acute toxicity was investigated. For that purpose ISO 8192 activated sludge inhibition and Daphnia magna acute toxicity tests were conducted. BOD5 measurements that were carried out to preevaluate the biocompatibility of untreated, ozonated, and perozonated PPG effluent have shown that BOD5 alone was not a very correct or useful too] to predict the actual biodegradability of PPG effluent. No significant correlation existed between the BOD5 and the toxicity test results. Acute toxicity studies carried out with D. magna and synthetic Municipal sewage sludge have demonstrated the inhibitory effect of H2O2/O-3 oxidation. COD removal of pharmaceutical wastewater containing PPG effluent with acclimated sewage sludge decreased from 79% to 50% after H2O2/O-3 pretreatment. (c) 2005 Elsevier Inc. All rights reserved.