Oxidative treatment of antibiotics in pharmaceutical effluents

Abstract

Antibiotics are intensively used both in veterinary and human medicine and up to 90 per cent they are excreted through urine and feces into municipal sewage after administration. They can also enter to the sewage treatment plants through the wastewater generated from the formulation process in pharmaceutical industry. Since antibiotic containing effluents are inert towards conventional biotreatment, antibiotics may reach to the aquatic environment and thus such effluents require an oxidative pretreatment. Cephalosporine (I) and penicillin (II) group human antibiotics and quinolone group veterinary antibiotic in synthetically prepared pharmaceutical formulation effluents were treated by ozonation in order to improve their biodegradability. The effects of pH, initial antibiotic concentration, dose of H2O2 and applied ozone doses were investigated on treatment performance. Elevating the reaction pH, inlet ozone concentration and H2O2 dose resulted in an enhancement on treatment efficiencies of all antibiotic formulation effluents. While in the veterinary antibiotic effluent BOD5/COD ratio was increased from 0.077 to 0.38 with an applied O3 dose of 2960 mg/L h, at pH=7, for human antibiotic I and human antibiotic II, BOD5/COD ratio was increased from 0 to 0.1 and 0.27 respectively. In order to correlate biodegradability results with a structure of antibiotics, degradation rates of antibiotics were related with energies required for the degradation by H-abstraction. Combination of ozone with UV, accelerated aromaticity removal from 63 to 83 per cent, and oxygen uptake rate from 0.21 to 0.28 mg/L min for veterinary antibiotic (CODi=900 mg/L), however, did not appear to be more effective than applying mere ozonation in terms of COD removal rates.