Antibiotics are often applied in aquaculture to prevent
fish diseases. These substances can cause disturbances on receiving waters, when not properly eliminated from the aquaculture effluents. In this work,
ozone (O3) was investigated as a possible
oxidizing agent to remove fishery
antibiotics from aquaculture effluents:
florfenicol (FF),
oxytetracycline (OTC),
sulfadimethoxine (
SDM),
sulfamethoxazole (SMX), and
trimethoprim (
TMP). Batch experiments were performed using ultrapure water and aquaculture effluents spiked with a mixture of target
antibiotics at relatively high concentrations (10 mg L-1 each). OTC, SMX and
TMP were fully removed (< 30 min) regardless of the tested conditions, mainly by O3 direct attack. In contrast, FF was partially removed in 30 min (∼ 10 and 60%, in aquaculture effluents and ultrapure water, respectively), but only in the presence of
hydroxyl radicals (HO•), the FF concentrations reaching levels below the detection limits in ultrapure water after 60 min. In the case of
SDM, its degradation was highly influenced by the selected water matrix, but with removals always higher than 68%. In continuous-flow experiments applying more environmentally relevant
antibiotic concentrations (100 ng L-1 each) and low O3 doses (1.5 mg L-1), ozonation highly removed (> 98%) all tested
antibiotics from aquaculture effluents with a hydraulic retention time (HRT) of 10 min, except FF (68%). Although by-products were detected in treated samples, zebrafish (Danio rerio) embryotoxicity tests did not show a toxicity increase by applying this ozonation treatment. Ozonation is thus a possible
solution to remove
antibiotics from aquaculture effluents. Still, full-scale studies in aquaculture farms are needed, and generation of HO• may be favoured to readily oxidize the FF
antibiotic.