Ozonation of cytostatic drugs in aqueous phase

As the number of cancer patients increases, so does the consumption of cytostatic drugs, which are commonly used in chemotherapy. These compounds are already ubiquitous in wastewater treatment plant (WWTP) effluents and natural water streams, revealing the urgent need for efficient technologies for their removal from the aqueous phase. This work presents the elimination of five cytostatics of concern, found in Portuguese WWTP effluents: bicalutamide (BICA), capecitabine (CAP), cyclophosphamide (CYC), ifosfamide (IFO) and mycophenolic acid (MPA), using non-catalytic ozonation. Experiments were performed starting from trace-level concentrations (1 μM) for all cytostatics at neutral pH (pH: 7.3 ± 0.1) and room temperature (23 ± 1 °C), employing different ozone dosages. Under the studied conditions, CAP and MPA were quickly eliminated by direct ozonation, whereas BICA, CYC and IFO were more slowly degraded, as they undergo a breakdown via hydroxyl radicals generation (HO) exclusively. Increasing the O₃ dosage from 1 to 3 mg_O3/mg_DOC, CAP, MPA and IFO were completely removed, and BICA and CYC were converted more than 90% after 180 min. The presence of both inorganic ions and organic matter in real water matrices (river water, WWTP secondary effluent) did not affect the removal of CAP and MPA. Nonetheless, there was an inefficient and very fast O₃ consumption that resulted in only around 30% elimination of BICA, CYC and IFO, even if the reaction time is extended.