Nanofiltration combined with ozone-based processes for the removal of antineoplastic drugs from wastewater effluents

Over the past years, there has been an increasing concern about the occurrence of antineoplastic drugs in water bodies. The incomplete removal of these pharmaceuticals from wastewaters has been confirmed by several scientists, making it urgent to find a reliable technique or a combination of techniques capable to produce clean and safe water. In this work, the combination of nanofiltration and ozone (O3)-based processes (NF + O3, NF + O3/H2O2 and NF + O3/H2O2/UVA) was studied aiming to produce clean water from wastewater treatment plant (WWTP) secondary effluents to be safely discharged into water bodies, reused in daily practices such as aquaculture activities or for recharging aquifers used as abstraction sources for drinking water production. Nanofiltration was performed in a pilot-scale unit and O3-based processes in a continuous-flow column. The peroxone process (O3/H2O2) was considered the most promising technology to be coupled to nanofiltration, all the target pharmaceuticals being removed at an extent higher than 98% from WWTP secondary effluents, with a DOC reduction up to 92%. The applicability of the clean water stream for recharging aquifers used as abstraction sources for drinking water production was supported by a risk assessment approach, regarding the final concentrations of the target pharmaceuticals. Moreover, the toxicity of the nanofiltration retentate, a polluted stream generated from the nanofiltration system, was greatly decreased after the application of the peroxone process, which evidences the positive impact on the environment of implementing a NF + O3/H2O2 process.

Theoretical rejection of fifty-four antineoplastic drugs by different nanofiltration membranes

The rise of nanofiltration technologies holds great promise for creating more effective and affordable techniques aiming to remove undesirable pollutants from wastewaters. Despite nanofiltration's promising potential in removing antineoplastic drugs from liquid matrices, the limited information on this topic makes it important to estimate the rejection rates for a larger number of compounds, particularly the emerging ones, in order to preview the nanofiltration performance. Aiming to have preliminary estimations of the rejection rates of antineoplastic drugs by nanofiltration, 54 antineoplastic drugs were studied in 5 nanofiltration membranes (Desal 5DK, Desal HL, Trisep TS-80, NF270, and NF50), using a quantitative structure-activity relationship (QSAR) model. While this methodology provides useful and reliable predictions of the rejections of compounds by nanofiltration, particularly for hydrophilic and neutral compounds, it is important to note that QSAR results should always be corroborated by experimental assays, as predictions were confirmed to have their limitations (especially for hydrophobic and charged compounds). Out of the 54 studied antineoplastic drugs, 29 were predicted to have a rejection that could go up to 100%, independent of the membrane used. Nonetheless, there were 2 antineoplastic drugs, fluorouracil and thiotepa, for which negligible removals were obtained (<21%). This study's findings may contribute (i) to the selection of the most appropriate nanofiltration membranes for removing antineoplastic drugs from wastewaters and (ii) to assist in the design of effective treatment approaches for their removal.

Antineoplastic drugs in urban wastewater: Occurrence, nanofiltration treatment and toxicity screening

Antineoplastic drugs are pharmaceuticals that have been raising concerns among the scientific community due to: (i) their increasing prescription in the fight against the disease of the twentieth century (cancer); (ii) their recalcitrance to conventional wastewater treatments; (iii) their poor environmental biodegradability; and (iv) their potential risk to any eukaryotic organism. This emerges the urgency in finding solutions to mitigate the entrance and accumulation of these hazardous chemicals in the environment. Advanced oxidation processes (AOPs) have been taken into consideration to improve the degradation of antineoplastic drugs in wastewater treatment plants (WWTPs), but the formation of by-products that are more toxic or exhibit a different toxicity profile than the parent drug is frequently reported. This work evaluates the performance of a nanofiltration pilot unit, equipped with a Desal 5DK membrane, in the treatment of real WWTP effluents contaminated (without spiking) with eleven pharmaceuticals, five of which were never studied before. Average removals of 68 ± 23% were achieved for the eleven compounds, with decreasing risks from feed to permeate for aquatic organisms from receiving waterbodies (with the exception of cyclophosphamide, for which a high risk was estimated in the permeate). Aditionally, no significative impact on the growth and germination of three different seeds (Lepidium sativum, Sinapis alba, and Sorghum saccharatum) were determined for permeate matrix in comparison to the control.

Multi-target analysis of cytostatics in hospital effluents over a 9-month period

The consumption of cytostatics, pharmaceuticals prescribed in chemotherapy, is increasing every year and worldwide, along with the incidence of cancer. The presence and the temporal evolution of cytostatics in wastewaters from a Portuguese hospital center was evaluated through a 9-month sampling campaign, comprising a total of one hundred and twenty-nine samples, collected from May 2019 to February 2020. Eleven cytostatics out of thirteen pharmaceuticals were studied, including flutamide, mycophenolate mofetil and mycophenolic acid, which have never been monitored before. Target analytes were extracted and quantified by solid-phase extraction coupled to liquid-chromatography-tandem mass spectrometry analysis; the method was fully validated. All pharmaceuticals were detected in at least one sample, bicalutamide being the one found with higher frequency (detected in all samples), followed by mycophenolic acid, which was also the compound detected at higher concentrations (up to 5340 ± 211 ng/L). Etoposide, classified as carcinogenic to humans, was detected in 60% of the samples at concentrations up to 142 ± 15 ng/L. The risk from exposure to cytostatics was estimated for aquatic organisms living in receiving bodies. Cyclophosphamide, doxorubicin, etoposide, flutamide, megestrol and mycophenolic acid are suspected to induce risk. Long-term and synergic effects should not be neglected, even for the cytostatics for which no risk was estimated.

Are cytostatic drugs in surface waters a potential threat?

Cytostatic drugs are pharmaceuticals administered to cancer patients under chemotherapy. Their occurrence in surface waters has been reported worldwide, increasing environmental and human health concerns. This work addresses a question of worldwide interest: are these hazardous pharmaceuticals in surface waters a potential threat? For the first time, this study brings information on the presence of cytostatic drugs in Portuguese rivers. Furthermore, cutting-edge data on the occurrence of two cytostatic drugs is provided; up to the authors' best knowledge, flutamide and mycophenolate mofetil have never been monitored in worldwide surface waters. Nine out of thirteen cytostatic drugs were detected in Portuguese rivers. Despite bicalutamide being the cytostatic most frequently detected, the highest concentration was recorded for cyproterone (19 ± 3 ng/L). Three different scenarios were considered to estimate the risks from the exposure of humans to cytostatic drugs via surface waters. Two scenarios are associated with bathing practices in rivers, particularly in the spring and summer seasons (river beaches): (i) the exposure to cytostatic drugs by dermal contact with contaminated water and (ii) the exposure by accidental ingestion of contaminated water, which is less likely but also occurs. The third exposure scenario is related to (iii) the long-life consumption of drinking water produced from river water capture, under worst-case conditions, i.e. negligible degradation of cytostatic drugs at drinking water treatment plants. It was concluded that the third exposure context to cytostatics could represent a risk to children, if the highest concentration ever reported in the literature for cyclophosphamide in surface waters is considered. Still, attending to the carcinogenicity of some of these compounds (e.g., cyclophosphamide, chlorambucil, etoposide and tamoxifen), health risks might always be expected, regardless of the contamination level. Furthermore, health risks associated with synergic effects and/or long-term exposures cannot be ruled out, even for the remaining cytostatics/exposure contexts.

Intensification strategies for cytostatics degradation by ozone-based processes in aqueous phase

Over the past decade there has been an increasing concern on the presence of cytostatics (also known as anticancer drugs) in natural waterbodies. The conventional wastewater treatments seem not to be effective enough to remove them, and therefore new processes must be considered. This work investigates the performance of ozonation (O₃), catalytic ozonation (O₃/Fe²⁺) and peroxone (O₃/H₂O₂) processes, under dark or UV radiation conditions, for the degradation of cytostatics of worldwide concern. The degradation of bicalutamide (a representative of recalcitrant cytostatics) was firstly assessed in batch and then in a tubular column reactor (continuous flow mode runs) using a wastewater treatment plant (WWTP) secondary effluent. Bicalutamide removal ranged between 66 % (O₃) and 98 % (O₃/H₂O₂/UV) in continuous flow mode runs, the peroxone process being the most effective. The performance of these processes was then assessed against a mixture of twelve cytostatics of worldwide concern spiked in the WWTP effluent (25-350 ng/L). After treatment, seven cytostatics were completely removed, whereas the five most recalcitrant ones were eliminated to an extent of 8-92 % in O₃/H₂O₂, and 44-95 % in O₃/H₂O₂/UV. Phytotoxicity tests revealed a noticeable reduction in the effluent toxicity, demonstrating the feasibility of these processes in realistic conditions as tertiary treatment.

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.

Liquid-liquid extraction as a simple tool to quickly quantify fourteen cytostatics in urban wastewaters and access their impact in aquatic biota

Cytostatics are highly toxic pharmaceuticals used in the treatment of cancer. These substances are partially excreted by the human body after administration. The inefficient removal of some cytostatics in urban wastewater treatment plants (WWTPs) allows them to reach surface waters and consequently the aquatic biota. However, information about their occurrence in urban wastewaters is available only for certain active ingredients. A liquid-liquid extraction method coupled to liquid-chromatography-tandem mass spectrometry analysis was developed, allowing the identification and quantification of 14 cytostatics in wastewater samples, avoiding the use of expensive sorbents. Moreover, satisfactory cytostatics' recoveries were achieved when the new method was applied to wastewaters from a Portuguese WWTP: average of (74 ± 21)% for the influents, (83 ± 22)% for secondary effluents, and (94 ± 24)% for tertiary effluents collected after UV treatment, except for imatinib. Doxorubicin, etoposide, megestrol and prednisone were completely eliminated in the first stage of the WWTP treatment (i.e. detected in the influents, but not in the effluents). Bicalutamide, capecitabine, cyclophosphamide, ifosfamide and mycophenolic acid were recalcitrant to UV radiation (i.e. detected in tertiary effluents), ifosfamide being the cytostatic most difficult to be removed (its concentration did not decrease from the entrance to the outlet of the WWTP). The risk at which aquatic organisms might be subjected, due to their exposure to cytostatics' concentrations 10-times lower than those found in the tertiary effluents, was estimated and it was verified that mycophenolic acid may represent a high risk. Although no risk was estimated for the other cytostatics, the risks associated to long-term and synergic exposure should not be ruled out.

New insights on cytostatic drug risk assessment in aquatic environments based on measured concentrations in surface waters

Cytostatic drugs are compounds used to treat cancer, one of the deadliest diseases worldwide with a rising yearly incidence. However, the occurrence and concentrations of a large number of cytostatics in waters and wastewaters are unknown. Thus, this study sought to analyze the concentrations of these compounds in different aquatic environments worldwide to assess the risk that these compounds pose to aquatic organisms. The top five most monitored cytostatics in aquatic environments are fluorouracil, methotrexate, tamoxifen, ifosfamide, and cyclophosphamide. Risk quotients (RQs) based on maximum reported measured concentrations revealed that mycophenolic acid and tamoxifen pose a high risk to aquatic organisms (RQ_max ≥ 1) at concentrations observed in surface waters. Moreover, methotrexate and tegafur were categorized as moderate risk compounds, and bicalutamide was found to pose a low risk. Importantly, the available analytical methodologies for the quantification of some cytostatics (e.g., cisplatin, fluorouracil, daunorubicin, imatinib, and mycophenolic acid) in water could not rule out potential risk to aquatic biota, since estimated risks for these compounds using the lowest method detection limits reported in the literature (RQ MDL) were all ≥0.01 (i.e., low risk or higher). Moreover, risks based on predicted concentrations (RQ PEC) were consistently lower than those based on measured concentrations, highlighting the importance of risk assessment based on measured values. Thus, accurate and sensitive analytical methods are crucial to identify and quantify cytostatic exposure in aquatic ecosystems in order to preserve biodiversity and ensure a safer environment.