Removal of antiretroviral drugs stavudine and zidovudine in water under UV254 and UV254/H2O2 processes: Quantum yields, kinetics and ecotoxicology assessment

The concentration of antiretroviral drugs in wastewater treatment plants (WWTP) effluents and surface waters of many countries has increased significantly due to their widespread use for HIV treatment. In this study, the removal of stavudine and zidovudine under UV254 photolysis or UV254/H2O2 was investigated in a microcapillary film (MCF) photoreactor, using minimal water samples quantities. The UV254 quantum yield of zidovudine, (2.357 ± 0.0589)·10−2 mol ein−1 (pH 4.0–8.0), was 28-fold higher that the yield of stavudine (8.34 ± 0.334)·10−4 mol ein−1 (pH 6.0–8.0). The second-order rate constant kOH,iof reaction of hydroxyl radical with the antiretrovirals (UV254/H2O2 process) were determined by kinetics modeling: (9.98 ± 0.68)·108 M−1 s−1 (pH 4.0–8.0) for zidovudine and (2.03 ± 0.18)·109 M−1 s−1 (pH 6.0–8.0) for stavudine. A battery of ecotoxicological tests (i.e. inhibition growth, bioluminescence, mutagenic and genotoxic activity) using bacteria (Aliivibrio fischeri, Salmonella typhimurium), crustacean (Daphnia magna) and algae (Raphidocelis subcapitata) revealed a marked influence of the UV dose on the ecotoxicological activity. The UV254/H2O2 treatment process reduced the ecotoxicological risk associated to direct photolysis of the antiretrovirals aqueous solutions, but required significantly higher UV254 doses (≥2000 mJ cm−2) in comparison to common water UV disinfection processes.