Effectiveness of Advanced Oxidation Processes in Wastewater Treatment: State of the Art

water Review Effectiveness of Advanced Oxidation Processes in Wastewater Treatment: State of the Art Laura Antiñolo Bermúdez 1, Jaime Martín Pascual 1, María del Mar Muñio Martínez 2 and Jose Manuel Poyatos Capilla 1,*   Citation: Bermúdez, L.A.; Pascual, J.M.; Martínez, M.d.M.M.; Poyatos Capilla, J.M. Effectiveness of Advanced Oxidation Processes in Wastewater Treatment: State of the Art. Water 2021,13, 2094. https://doi.org/ 10.3390/w13152094 Academic Editor: Hongyu Ren Received: 31 May 2021 Accepted: 27 July 2021 Published: 30 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1Department of Civil Engineering and Institute of Water Research, University of Granada, 18071 Granada, Spain; [email protected] (L.A.B.); [email protected] (J.M.P.) 2Department of Chemical Engineering, University of Granada, 18071 Granada, Spain; [email protected] *Correspondence: [email protected] Abstract: In recent years, many scientific studies have focused their efforts on quantifying the different types of pollutants that are not removed in wastewater treatment plants. Compounds of emerging concern (CECs) have been detected in different natural environments. The presence of these compounds in wastewater is not new, but they may have consequences in the future. These compounds reach the natural environment through various routes, such as wastewater. This review focuses on the study of tertiary treatment with advanced oxidation processes (AOPs) for the degradation of CECs. The main objective of the different existing AOPs applied to the treatment of wastewater is the degradation of pollutants that are not eliminated by means of traditional wastewater treatment. Keywords: advanced oxidation processes; compounds of emerging concern; wastewater treatment plants; tertiary treatment 1. Introduction Today, there is strong environmental concern and a focus on minimising the impact of human activities on the environment. For years, the overexploitation to which the planet has been subjected has been unsustainable, highlighting the pressure exerted on the world’s water reserves. The high demand of population centres, massive industrial production, and agricultural activities have caused an unsustainable situation for the available water resources [ 1 ]. Due to this, wastewater treatment becomes absolutely essential for the subsequent return to the natural environment in the most efficient way possible. However, current technologies used in wastewater treatment are not efficient against certain types of pollutants that are able to remain in the treated wastewater, which is returned to the natural environment, thus reaching the water reserves [ 2 , 3 ]. Once in the environment, they are characterized by environmental persistence and threats to human health [ 4 , 5 ]. Due to the low concentrations of contaminants and diversity in nature, the removal of these contaminants poses numerous challenges [6]. Due to this, the application of tertiary treatments that are effective and economically viable in wastewater treatment plants has been investigated in recent years. These pollutants are a global problem and are not limited to just one region; they have been detected in waters around the world. In América, the Biobío River (Chile) has population settlements that, due to their economic activities, such as agriculture or forestry, incorporate compounds of emerging concern, such as pharmaceuticals, personal care products, and pesticides, into the aquatic environment [ 7 ]. The presence of 28 antibiotics was detected in six rivers and a drinking water storage catchment in watersheds of South- East Queensland, Australia [ 8 ]. In the Somes River (Transylvania, Romania), compounds including musk fragrances, pharmaceutics, metabolites and intermediates were detected [ 9 ]. An analysis of the Ebro River (Spain) revealed the presence of 31 pharmaceuticals; these Water 2021,13, 2094. https://doi.org/10.3390/w13152094 https://www.mdpi.com/journal/water Water 2021,13, 2094 2 of 19 compounds were detected in wastewater treatment plant (WWTP) effluents, with the highest concentrations found in effluents of the Zaragoza WWTP [ 10 ]. It was detected the occurrence of 20 illicit and therapeutic pharmaceuticals and metabolites in surface waters influenced by WWTP discharge and in wastewater effluents in Nebraska [ 11 ]. In the Pearl River (China), eight types of antibiotics were detected in the water [ 12 ]. Laboratory analysis revealed that antibiotics were widely distributed in Baiyangdian Lake, China [ 13 ]. In rivers and lakes in the agricultural zone of Northeast Denmark, 17 emerging contaminants (diclofenac, MCPA, caffeine and TCEPT were the most abundant) were identified and quantified in surface waters (including pesticides, personal care products [PCPs], pharmaceuticals, plasticisers, and fire retardants) [ 14 ]. In the affluents of the Delaware River (Pennsylvania, EE.UU), Triclosan (PCP), which is widely used as an antiseptic, was found in high concentrations, which proved to be a high-risk compound for aquatic life. In this river, Diphenhydramine (antibiotic) was also found whose effect is similar to Triclosan [15]. Pollution is not just limited to water; it is also ‘absorbed’ by sediments and living organisms that are found where waters contaminated by CECs are found. In Baiyangdian Lake (China), quinolones were detected in sediments and aquatic plants. Quinolones and macrolides are often found in aquatic animals and birds [13]. The present study focuses on the different types of advanced oxidations and their efficiency against the different polluting CECs. These pollutants are a global problem and are not limited to just one region but have been detected in waters around the world. This paper tries to give a global view of the problem by compiling the most relevant studies carried out during the last decade and centralizes other studies that review the problem. 2. Advanced Oxidation Processes for Wastewater Treatment Advanced oxidation processes (AOPs) have been used in urban and industrial wastewater treatment as an effective option for the treatment of non-biodegradable compounds [ 16 ]. The complete mineralisation to water, inorganic compounds and CO 2 , water of the contaminants in the wastewater, or at least their transformation into more innocuous compounds, can be achieved by applying a chemical treatment using AOPs [ 17 ]. There is a wide range of advanced oxidation treatments where different reagents are used with the aim of producing OH • radicals, which are very powerful oxidising agents. AOPs are classified as either homogeneous or heterogeneous. Homogeneous processes include processes that use energy and those that do not. This classification is shown in Figure 1. Homogeneous processes that use energy and ultraviolet radiation use reagent systems that include O 3 , H 2 O 2 , and photo-Fenton reactions. They all produce OH • radicals. For the degradation of compounds whose UV absorption range is within the corresponding range of the spectrum, these AOPs are generally used [ 17 , 18 ]. Homogeneous processes that use ultrasound energy form hydroxyl radicals because of the extreme conditions generated by ultrasound, which are capable of cracking water molecules. They can be combined with other AOPs. Finally, homogeneous processes that use energy have anodic oxidation, electrochemical oxidation, and electro-Fenton processes. This type of process breaks down compounds and molecules for degradation using electrical energy. The electron transfer occurs by the intervention of hydroxyl radicals [17]. Homogeneous processes that do not use energy are hydrogen peroxide and catalyst processes, ozonation with hydrogen peroxide, and ozonation in an alkaline medium. The difference between the hydrogen peroxide process and catalysation with H 2 O 2 /UV is found in the area of radical formation of OH • , which is less in the process that does not use energy [17]. In heterogeneous AOPs, catalysts are often used to produce the degradation of the contaminant compounds. Compared to homogeneous processes, the catalysts used in heterogeneous processes have the advantage of being able to separate the product more easily [17]. The reactions produced in the different types of AOPs are exposed in Table 1. Water 2021,13, 2094 3 of 19 Table 1. Reactions of the different types of advanced oxidation processes. Advanced Oxidation Processes Reactions Description Examples of Pollutants That Can Be Removed O3/UV H2O+O3hv →2OH•+O2 2OH•→H2O2 The photolysis of the ozone produces the formation of hydroxyl radicals [17]. Imidacloprid [19] H2O2/UV 2OH•hv →H2O2 The formation of hydroxyl radicals is generated by photolysis of H2O2[17]. Bacterias (E. Coli, S. Enteritidis and E. Faecalis) [20] Inactivation of a multidrug resistant E. Coli [21] O3/H2O2/UV 2O3+H2O2hv →2OH•+3O2 Combination of systems O3/UV and H2O2/UV. The use of H2O2it accelerates the decomposition of ozone and increases the generation of OH•[17]. Tamoxifen [22] Fe2+/H2O2/UV Fe2++H2O2→Fe3++OH−+OH• The Fenton reaction is the process most often applied when it is necessary to remove recalcitrant compounds [17]. E. Faecalis [23] Inactivation of a multidrug resistant E. Coli [21] O3/US H2O))) →H•+OH• O3 ))) →O2(g)+O(3P) O(3P)(g)+H2O→2OH• O3+OH•→O2+HO• 2 O2+H•→HO• 2 O3+HO• 2→2O2+OH• OH•+OH•→H2O HO• 2+OH•→H2O+O2 Ultrasounds are represented as ‘(((‘ [24]. 7α-estradiol, 17β-estradiol, estrone, 17α-dihydroequilin, 17α-ethinyl estradiol, estriol and equilin [25] H2O2/US H2O2 ))) →OH•+OH• H2O2+O2 ))) →HO• 2+HO• 2 H2O2+OH•→HO• 2+H2O The combination of ultrasound and H2O2 achieves the formation of hydroxyl radicals [26]. 7α-estradiol, 17β-estradiol, estrone, 17α-dihydroequilin, 17α-ethinyl estradiol, estriol and equilin [25] Electrochemical oxidation [Anode] H2O→H++(OH•)ads +e− (OH•)ads →(O)adsorO2+H++e− (O)ads +O2→O3 [Cathode] O2+2H++2e−→H2O2 In this type of oxidation, the compound to be degraded reacts to the oxidants, which have been electrochemically generated in situ [27]. Reactive Orange 16, Reactive Violet 4, Reactive Red 228, and Reactive Black 5 [28] Anodic oxidation Anode +H2O→H++Anode(OH•)+e− In this process, organic compounds directly react with heterogeneous hydroxyl radicals (OH•), formed by oxidation of water at the surface of anode with high oxygen overpotential [29]. Acid Red 1 azo dye [30] Electro-Fenton O2(g)+2H++2e−→H2O2 Hydrogen peroxide is produced electrochemically through the cathodic reduction of dissolved oxygen on a carbon electrode [31]. Non-polar organochlorine pesticides [32] Direct yellow 9 azo dye [33] Ozonation in an alkaline medium O3+OH−→O•− 3+OH• O•− 3→O2+O•− O•− +H+→OH• The degradation of the compound occurs through the action of the ozone itself as well as through the radicals generated in the alkaline medium [34]. Bisphenol A, paraxantina [35] Ozonation with hydrogen peroxide H2O2+2O3→2OH•+3O2 HO− 2+O3→HO• 2+O• 3 Hydrogen peroxide in an aqueous solution is partially dissociated to hydroperoxide anion which reacts with ozone [36]. Fluoroquinolone antibiotics and Clarithromycin [37] Hydrogen peroxide and catalyst Fe2++H2O2→Fe3++OH−+OH• This type of reaction is very similar to photo-Fenton processes but the formation rate of OH•radicals is lower [17]. Doxycycline (catalyst CoFe2O4) [38] Catalytic ozonation Fe2++O3→FeO2++O2 FeO2++H2O→Fe3++OH•+OH− In catalytic ozonation the most widely used catalyst is Fe2+ [36]. Naphthalene [39] Photocatalytic ozonation: O3/UV/TiO2 TiO2hv →h++e− e−+O3→O− 3 O− 3→O2+O− O−+H2O→OH−+OH• h++OH−→OH• Titanium dioxide (TiO2) is the most effective catalyst of those used in AOPs. The basic mechanism is described by [40]. Diclofenac [41] Heterogeneous photocatalysis: UV/TiO2/H2O2 TiO2hv →TiO2(e−+h+) TiO2h++OH− ad →TiO2+OH• H2O2+e−→OH•+OH− In these processes, titanium dioxide is combined with hydrogen peroxide and UV radiation [42]. Inactivation of A multidrug resistant E. Coli [21] Water 2021,13, 2094 4 of 19 Figure 1. Classification of advanced oxidation processes. Abbreviations used: O 3 , ozonation; H 2 O 2 , hydrogen peroxide; UV, ultraviolet radiation; US, ultrasound energy; Fe2+, ferrous ion, modified of [17]. 3. Methodology The search for relevant literature was carried out by searching the Scopus database using the following keywords: “advanced oxidation processes”, “concern emerging contaminants” and “wastewater treatment”. The first search resulted in 51 articles, and a review article for 2010 (67 additional references) was used to provide an overview since 2000. The less relevant articles were discarded following the criterion of looking for articles of removal of the same pollutants with more easily reproducible operating conditions. Once the search list was generated, it was manually checked to exclude studies that were not relevant and to give preference to articles that eliminated several contaminants. In addition, relevant studies found in the bibliography of the selected studies were included in the literature identification list. Articles were selected from the years 2000 to 2021 to check the progress of the technology studied and only articles written in English were selected. This extended range of years was selected because it was considered important to give an overview of the evolution of advanced oxidation processes. 4. Compounds of Emerging Concern (CECs) Water is the essential resource for life; everybody depends on it, and because of this it is one of the most threatened resources on the planet. Aquifers and water reserves are constantly affected by overexploitation and pollution associated with human activities. For this reason, the European Union (EU), as well as most governments around the world, is focusing efforts on achieving good quality of their resources. The EU created an observation list of emerging pollutants. These substances do not currently follow an elimination legisla- Water 2021,13, 2094 5 of 19 tion, but it has been studied and shown that they are present in rivers, lakes, aquifers, and natural environments; therefore, they can pose a somewhat long-term risk and the study of their elimination is essential to prevent their entry into ecosystems. These substances can be divided into four main groups: pharmaceuticals (PHs) (e.g., antibiotics and analgesics), PCPs (e.g., fragrances and antiseptics), pesticides (e.g., atrazine and dimethoate) and illicit drugs (e.g., opioids and amphetamines). The introduction of this type of compound into the environment has its origin in human activity. Transformation products and metabolites may enter the aquatic environment and eventually reach drinking water if the CECs are not eliminated during wastewater treatment [43]. The EU, through Directive 2008/105/EC, establishes an observation list of substances for monitoring purposes at the European level. This list is updated every 24 months by the Water Framework Directive of the European Union. These modifications are made taking into account several criteria, among which are the research programmes in force and the characterisation and results obtained by the member states of the EU of their river basin districts. Each member state selects a representative monitoring station, and the monitoring frequency shall not be less than once a year. The last update of this list was made in December 2018, and a final programme of measures is foreseen for December 2021 to be fully operational by December 2024 (https://www.boe.es/buscar/doc.php? id=DOUE-L-2013-81677 accessed on 7 April 2020). In addition, in 2005, the European Commission funded the NORMAN project. (https://www.norman-network.net accessed on 7 April 2020). The NORMAN network enhances the exchange of information on emerging environmental substances and encourages the validation and harmonisation of common measurement methods and monitoring tools so that the requirements of risk assessors and risk managers can be better met. It specifically seeks both to promote and to benefit from the synergies between research teams from different countries in the field of emerging substances. This network includes the competent authorities/reference laboratories, research centres and academia, industry stakeholders, government institutions and standardisation bodies. The mission of the NORMAN network is to enhance the exchange of information and collection data environmental substances, encourage the validation and harmonisation of common measurement methods and monitoring tools so that the demands of risk assessors can be better met and ensure that knowledge of emerging pollutants is maintained and developed by stimulating coordinated, interdisciplinary projects on problem-oriented research and knowledge transfer to address identified needs. In the case of the US, the Environmental Protection Agency (EPA; https://www. epa.gov/ccl accessed on 28 May 2020) publishes a Contaminant Candidate List (CCL) every five years, with the last being published in 2016. The EPA has a candidate list of 97 chemical contaminants/groups of contaminants and 12 microbial contaminants (including PHs and PCPs). Within this area, each member state, as with Europe, adapts this policy to its territory. In California, the State Water Resources Control Board has a Recycled Water Policy where scientific advisors provide guidance on how to monitor CECs for prioritisation in legislation [44]. In the case of Japan and its Ministry of Health, they focus their efforts on evaluating the environmental risk posed by pharmaceutical products, and with it their marketing is approved or denied. The same occurs in the case of Canada and Australia, which are based on standard physicochemical tests to determine the biodegradability of the compounds, without following a specific list that is monitored or regulated (World Health Organization, 2012). In China, the Ministry of Environmental Protection establishes a plan for the control and prevention of environmental risks of chemical substances, including pharmaceuticals. This was launched in 2013 [45]. In general, the release of antibiotics into the environment is believed to be a major concern as it can increase the appearance of resistant bacteria in the environment. However, Water 2021,13, 2094 6 of 19 treatments done by man, as well as natural filtration, can be penetrated by emerging compounds and cause them to pose a potential risk to the supply of drinking water [46]. 4.1. Pharmaceuticals Compounds (PH) The appearance of different types of pharmaceuticals in waters has been extensively studied in recent years. A large number of compounds associated with the removal of urban and industrial wastewater have been detected in groundwater and surface. The current wastewater treatment technology is insufficient for these pollutants, and they are not retained in the treatment plants, which is why many of these pharmaceutical residues reach the ecosystem, thus joining the water cycle. In primary treatments, while some pharmaceuticals remain in the water, others can be removed by adsorption, e.g., naproxen, ibuprofen, iopromide, and sulfamethoxazole [ 47 , 48 ]. Antibiotics and anti-inflammatories are eliminated in subsequent biological treatments by 30–75%. The concern about pharmaceuticals is their chronic toxicity and not their acute toxic effects. In general, pharmaceuticals are biologically active compounds that are not easily biodegradable. They may cause side effects in non-target organisms or cause a similar function as they do in their intended users [ 49 ]. The evolution and spread of antimicrobial resistance are recognised as one of the major global health challenges of the 21st century by major regulatory, economic, and political bodies, including the European Commission (EC), the United Nations (UN), and the World Health Organisation (WHO), and the surveillance of critical hotspots through intensive monitoring is recommended, including urban wastewater treatment plants, aimed at reducing its propagation [50]. The uncontrolled consumption of pharmaceuticals by the population, where many of them are consumed without medical control, such as ibuprofen or diclofenac, has led to their detection in water intended for human consumption [ 8 ]. Thus, hospital wastewaters, landfill leachates, and municipal wastewaters are always considered ‘hot spots’ for environmental water contamination by pharmaceuticals [51]. During therapeutic periods, humans excrete pharmaceuticals and their metabolites. In the case of pharmaceuticals used for veterinary medicine, when animal wastes are sprayed on agricultural fields to fertilise them, these substances are released into the environment [52]. The different physico-chemical properties of these compounds, as well as their metabolites or degradation by-products thereof, can affect the waters they arrive at and/or be retained in the soil into which the treated waters are discharged, which causes a negative effect on the ecosystem. The annual usage of antibiotics has been estimated to be between 100.000 and 200.000 tons globally, with more than 25.000 tons used each year in China [12,53]. The pharmaceuticals are divided into several types, analgesics and antibiotics are the most widely used of them. Antibiotics: These are pharmaceuticals that are used to fight bacterial infections in organisms. Their use is not limited to humans, but they are also used in animals and in the food industry to preserve food. Therefore, they are widely produced and consumed, causing large amounts of them to be present in wastewater. Analgesics and anti-inflammatories: These are the pharmaceuticals with the highest global consumption and those most used by the population as self-medication [ 54 ]. Compounds such as ibuprofen and diclofenac belong to this group. Antidepressants and anticonvulsants: These medications help improve the way the brain uses certain natural chemicals and can help combat depression and epileptic attacks. Lipid regulators: These are regulators of compounds present in blood, such as enzymes. β-blockers: These compounds work primarily in the heart and blood vessels. Many PHs are also thought to mimic natural hormones in the body, hence their classification as endocrine-disrupting chemicals (EDCs) [ 52 ]. These compounds are defined as natural and/or synthetic substances that can include naturally generated estrogenic Water 2021,13, 2094 7 of 19 hormones, e.g., estrone (E1) and 17b-oestradiol (E2), and, therefore, are ubiquitous in aquatic environments receiving wastewater effluents [ 49 ]. Oestrogens and xenoestrogens are excreted into wastewater and reach wastewater treatment plants as organic contaminants, where they are only partially eliminated [ 55 ]. Some of the most studied PHs and their classifications are listed in Table 2. Table 2. Classification and functions of pharmaceutical compounds. Pharmaceutical Compounds Use Examples [52] Antibiotics Antibacterial activity. Human and veterinary use Amoxicillin, ampicillin, cefaclor, cefalexin, ciprofloxacin, chlortetracycline, clarithromycin, difloxacine, doxycycline, enoxacin, erythromycin, lincomycin, levofloxacin, metromidazole, mecillinam, ofloxacin, oxytetracycline, penicillin, sulfamethoxazole, sulfadiazine, sulfamethizole, sulfathiazole, sulphapyridine, tetracyclines, trimethoprim, tylosin . . . Analgesics and anti-Inflammatory Pharmaceuticals Pain relief and the reduction of inflammation Ibuprofen, diclofenac, paracetamol, acetaminophen, acetylsalicylic acid, fenoprofen, indomethacin, naproxen, nimesulide, mefenamic acid, fluoxetine, ketoprofen, phenazone . . . Antidepressants and Anticonvulsants Relief from mental symptoms and the treatment of epileptic seizures Diazepam, carbamazepine, doxepin, imipramine, amitriptyline, primidone, salbutamol, meprobamate, fluxetine, oxazepam, gabapentin, phenobarbital, thioridazine, dilantin . . . Lipid Regulators Regulation of cholesterol and blood triglycerides Clofibric acid, clofibrate, benzafibrate, fenofibric acid, etofibrate, gemfibrozil, simvastatin, furosemide, Bendroflumethiazide . . . β-blockers Reduction of blood pressure Atenolol, metoprolol, propranolol, sotalol, timolol . . . X-ray contrasts Diagnostic contrast (organ visibility) Iopromide, iopamidol, diatrizoate . . . Eestrogens, Progestogens, Androgens, Glucocorticoids, Phytoestrogens & Hormones Regulation of female/male sexual development, maintenance of pregnancy, growth promotion in meat-producing animals, control of immune function, treatment of breast cancer, lymphomas and leukaemias 17b-Oestradiol (E2), estrone (E1), estriol, diethylstilbestrol (DES), 17-αethynylestradiol, mestranol, zerranol, trenbolone acetate, melengestrol acetate, tamoxifen, testosterone, phytosterols, sesquiterpenes, androstenedione, beclomethasone, progesterone, norethindrone . . . The application of AOPs based on studies of the removal of pharmaceutical products present in wastewater that are not eliminated by other technologies will be analysed. During the oxidation of urban wastewater, transformation products (TPs) of the antibiotics present can be formed, which may be more biologically potent, less biodegradable, or more toxic compared to the parent compounds [56]. One of the most studied types of AOPs for the treatment of wastewater by the authors is the UV/H 2 O 2 process. Photolysis of hydrogen peroxide is produced under ultraviolet radiation and it does not depend on pH. A H 2 O 2 /UV system can totally mineralise any organic compound, reducing it to CO 2 and water [ 17 ]. In addition, in this method, you can use sunlight instead of UV lamps. This is very interesting as in places where there are many hours with sunlight, this would be a low-cost application. In the case of antibiotics, this process can degrade compounds such as ciprofloxacin, which is a compound that is observed in wastewater. Ciprofloxacin is a compound included in the observation List of substances for the EU. Michael et al. [ 50 ] studied ciprofloxacin removal using H 2 O 2 /UV and H 2 O 2 /sunlight processes by comparing them to each other. H 2 O 2 /UV treatment was able to remove ciprofloxacin (90 min, 0.9 kJ L –1 ), while the H 2 O 2 /sunlight process was able to remove ciprofloxacin in 60 min (8 kJ L –1 ). Monteoliva-García et al. [ 57 ] reported the elimination of ciprofloxacin (concentrations from 22.30 to 98.53 µ g L −1 ) by applying Water 2021,13, 2094 8 of 19 H 2 O 2 /UV treatment ([H 2 O 2 ] = 25, 50, and 100 mg L −1 ), with total elimination after 20 min of treatment. Yuan et al. [ 58 ] completely eliminated ciprofloxacin by applying H 2 O 2 /UV from an initial CIP concentration of 5 µ M and using an LP-Hg lamp. Rosal et al. [ 59 ] studied ciprofloxacin removal using O 3 and O 3 /H 2 O 2 -based AOPs under similar conditions. While removal rates were very good at 98% and more than 93%, respectively, TOC removal was much more efficient in the O 3 /H 2 O 2 process, obtaining more than 90% removal compared to 15% in the other process. De Witte et al. [ 60 ] obtained a very similar result of eliminating the TOC of 95% by applying O 3 -based AOPs. Most of the treatments range between pH 7.5 and 8, this is very interesting and useful as this is within the pH range detected in urban wastewater. Therefore, for ciprofloxacin, it can be accepted that it can be almost completely removed from wastewater by AOPs, with the most favourable carbon treatment being O3/H2O2treatment. Another commonly used antibiotic is sulfamethoxazole. Michael et al. [ 50 ] studied its elimination by means of H 2 O 2 /UV and H 2 O 2 /sunlight treatment to determine which was more efficient. The H 2 O 2 /UV treatment was able to eliminate sulfamethoxazole after 90 min (0.9 kJ L −1 ), while the process with H 2 O 2 /UV only eliminated 46% after 300 min and 42 kJ L −1 . Lekkerkerker-Teunissen et al. [ 61 ] also studied the elimination of sulfamethoxazole by applying UV/H 2 O 2 treatment, which was able to eliminate it by more than 90% (UV doses ranged from 300–700 mJ cm –2 ). Yang et al. [ 62 ] applied the UV/H 2 O 2 treatment and succeeded in removing sulfamethoxazole (SMX) after 60 min. Other authors applied O 3 -based AOPs for SMX elimination, obtaining excellent elimination results (99.9%) from a high concentration of SMX (30 mg L –1 , 22 ◦ C) [ 63 ]. The pH range of the various treatments is very wide, ranging from 2–10. This is really useful; although, the water can be treated effectively at a natural pH but would achieve satisfactory eliminations in the event of temporary fluctuations in the plant. For the treatment of amoxicillin, an antibiotic widely used because of its great efficacy, its elimination has been studied using various POP processes. By applying UV/H 2 O 2 treatment, it was possible to irradiate the compound with a low-pressure lamp at an incident light intensity of 8 × 10 –7 Einstein L –1 s –1 and one at an H 2 O 2 concentration of 0.4–10 mM at 99% in only 20 min [ 64 ]. However, in the study by Elmolla et al. [ 65 ], which carried out UV/TiO 2 treatment, only 20% elimination (UV 365 nm) and a high pH dependency were reported, achieving the highest degradation at pH 11. The authors also studied the addition of H 2 O 2 at pH 5 (ambient) with a TiO 2 concentration of 1 g/L, achieving complete degradation of amoxicillin in only 30 min of heterogeneous photocatalysis treatment (UV/H 2 O 2 /TiO 2 ). The amoxicillin treatment with O 3 -based AOPs also provided very good results. At an initial amoxicillin concentration of 5.0 × 10 –4 M, with pH 5.5 (buffer) and a flow of O 3 1.6 × 10 –4 M, 90% was eliminated [ 66 ]. Therefore, amoxicillin is a compound that reacts very well to advanced oxidation treatments, achieving very good removal performance. In conclusion, the highest degradation for this pharmaceutical compound occurs at pH 11, which can be problematic; although, high clearance is also achieved at pH 5, where mineralisation of the pharmaceutical (phenolic ring hydroxylation) occurs. Another important antibiotic is metronidazole, which is used for bacterial infections affecting various parts of the body (vaginal infection primarily and others, such as the stomach, liver, skin, and brain). Several authors have studied their removal by applying different types of AOPs and comparing them with each other. Shemmet et al. [ 67 ] applied the UV/H 2 O 2 method under four operating conditions, obtaining elimination rates of between 58% and 67% (6.0 µ M metronidazole; 1.5 mW cm –2 ; 50 mg L –1 H 2 O 2 ). Furthermore, ref. [ 67 ] applied the UV/H 2 O 2 /Fe 2+ method and obtained 94% elimination as the best result, also starting from a 6.0 µ M Metronidazole concentration, and they compared it with the H 2 O 2 /Fe 2+ process under the same reaction conditions, where the maximum elimination result was 76%. These results show significant differences in behaviour under equal conditions, making the advanced photo-Fenton oxidation process the most effective against this compound. Rosal et al. [ 59 ] studied metronidazole elimination using ozone Water 2021,13, 2094 9 of 19 technology, comparing O 3 -based AOPs and O 3 /H 2 O 2 under the same conditions, where they obtained elimination percentages of 91% (15% TOC) and 92% (above 90% TOC), respectively, highlighting the role H 2 O 2 key to eliminating toxicity, the same as other antibiotics such as ciprofloxacin. The pH ranges studied are very broad, but the data seem to indicate that better removal rates are achieved at increasingly acidic pH values in UV/H 2 O 2 /Fe 2+ processes, with this AOP showing a removal rate of over 90%. In the case of lincomycin, Andreozzi et al. [ 68 ] applying different types of AOPs (UV/H 2 O 2 and O 3 -based AOPs). O 3 -based AOPs shown a total elimination in 2 min of treatment and no toxicity in one hour of treatment. UV/H 2 O 2 obtained the elimination percentages of 80% in 3 min of treatment and no toxic product generation. De Witte et al. [ 60 ] applying O3-based AOPs in the elimination of levofloxacin and obtained a removal of 99.9 %. The antiepileptic pharmaceutical carbamazepine, which is present in wastewater, has been studied for its removal by the advanced UV/H 2 O 2 removal process. At low H 2 O 2 concentration, carbamazepine removal is not appropriate despite UV treatment with medium- and low-pressure lamps [ 61 ]. However, at H 2 O 2 concentrations of 5 mg/L and above, up to 99.7% removal is achieved [ 69 ]. Monteoliva-García et al. [ 57 ] achieved at laboratory scale eliminations of more than 80% until complete elimination under real plant conditions (pH natural and real wastewater). The results of the different authors seem to indicate that working with natural pH is sufficient, but nevertheless the initial H 2 O 2 concentration in the treatment is very important, since at low concentrations the UV flux applied, even if it is high, is not sufficient to achieve optimum removal yields. Their elimination has been extensively studied lipid-lowering pharmaceuticals (lipid regulators). An example of this compound is bezafibrate, treating the waters with O 3 -based AOPs, eliminations of the compound have been reported ranging from 80% [ 70 ], 94% (15% TOC) [ 59 ] until reaching above 95% [ 71 ]. Another compound of the same nature, gemfibrozil also obtained elimination percentages close to 100%, but with better TOC elimination performance (>90%) when the ozone process is combined with H 2 O 2 , being the case similar to that of antibiotics [59]. Another type of pharmaceutical widely used is those known as anti-inflammatories. One example is diclofenac, a widely used anti-inflammatory that has been found in many wastewater treatment plant effluents. The advanced oxidation process H 2 O 2 /UV is able after 90 min of treatment to degrade this compound with a mineralisation of 39% [ 72 ]. Lekkerkerker-Teunissen et al. [ 61 ] reported its elimination in more than 80% by applying different intensities with low and medium pressure UV lamps two ranged from 300–700 mJ cm−2 and variable concentrations of H 2 O 2 (0–10 mg L −1 ). Andreozzi et al. [ 73 ] obtained a 100% elimination in 2 min starting from an initial diclofenac concentration of 2.8 mg L −1 and applying a UV intensity (LP-Hg lamp) of 2.51 × 10 −6 E s −1 and variable concentrations of H 2 O 2 . It is treatment by means of an AOP based on O 3 also eliminates it completely [ 74 ]. At a concentration of O 3 of 5 mg L –1 and H 2 O 2 of 1.8 mg L –1 , it showed high efficacy in the elimination of ibuprofen and diclofenac, obtaining 98% mineralisation [75]. The Photo-Fenton system completely oxidised diclofenac after 60 min [76]. Another anti-inflammatory widely used by the population and detectable in practically all studies of wastewater effluents is ibuprofen. Several authors have applied O 3 /H 2 O 2 treatment and O 3 -based AOPs obtaining very good results, with eliminations reaching up to 99.4% starting from an initial ibuprofen concentration of 2 µ g L −1 and an ozone flow 1–5 mg L –1 with a molar ratio O 3 :H 2 O 2 (2:1) [ 75 ]. Huber et al. [ 71 ] reported an elimination of between 40–70% treating the effluent with O 3 (0.1–2 mg L −1 ) starting from an ibuprofen concentration of 0.5 µ M. Eliminations greater than 62% were also achieved for water with an initial concentration of 0.13 µ g L −1 and an O 3 (5–15 mg L −1 ) [ 77 ]. Monteoliva-García et al. [ 57 ] reported an ibuprofen elimination (concentrations from 54.6 to 275.0 µ g L −1 ) applying the H 2 O 2 /UV treatment ([H 2 O 2 ] = 25, 50, and 100 mg L −1 ) from 89.8 to 100%. This seems to indicate that despite the high elimination obtained with both treatments, the most efficient is O3/H2O2, practically eliminating it completely. Water 2021,13, 2094 16 of 19 28. Soares, I.C.D.C.; Da Silva, Á.R.L.; Santos, E.C.M.D.M.; dos Santos, E.V.; Da Silva, D.R.; Martínez-Huitle, C.A. Understanding the electrochemical oxidation of dyes on platinum and boron-doped diamond electrode surfaces: Experimental and computational study. J. Solid State Electrochem. 2020,24, 3245–3256. [CrossRef] 29. Damodhar, G.; Ghosh, P. Removal of organic compounds found in the wastewater through electrochemical advanced oxidation processes: A review. Russ. J. Electrochem. 2019,55, 591–620. [CrossRef] 30. Florenza, X.; Solano AM, S.; Centellas, F.; Martínez-Huitle, C.A.; Brillas, E.; Garcia-Segura, S. Degradation of the azo dye Acid Red 1 by anodic oxidation and indirect electrochemical processes based on Fenton’s reaction chemistry. Relationship between decolorization, mineralization and products. Electrochim. Acta. 2014,142, 276–288. [CrossRef] 31. Peralta-Hernández, J.; Meas-Vong, Y.; Rodríguez, F.J.; Chapman, T.W.; Maldonado, M.I.; Godínez, L.A. Comparison of hydrogen peroxide-based processes for treating dye-containing wastewater: Decolorization and destruction of Orange II azo dye in dilute solution. Dye Pigment. 2008,76, 656–662. [CrossRef] 32. Raschitor, A.; Llanos, J.; Rodrigo, M.A.; Cañizares, P. Combined electrochemical processes for the efficient degradation of non-polar organochlorine pesticides. J. Environ. Manag. 2019,248, 109289. [CrossRef] [PubMed] 33. Kourdali, S.; Badis, A.; Boucherit, A. Degradation of direct yellow 9 by electro-Fenton: Process study and optimization and, monitoring of treated water toxicity using catalase. Ecotoxicol. Environ. Saf. 2014,110, 110–120. [CrossRef] [PubMed] 34. Alaton, I.A.; Balcioglu, I.A.; Bahnemann, D.W. Advanced oxidation of a reactive dyebath effluent: Comparison of O 3 , H 2 O 2 /UV-C and TiO2/UV-A processes. Water Res. 2002,36, 1143–1154. [CrossRef] 35. Dogruel, S.; Atesci, Z.C.; Aydin, E.; Pehlivanoglu-Mantas, E. Ozonation in advanced treatment of secondary municipal wastewater effluents for the removal of micropollutants. Environ. Sci. Pollut. Res. 2020,27, 45460–45475. [CrossRef] 36. Al Momani, F. Degradation of cyanobacteria anatoxin-a by advanced oxidation processes. Sep. Purif. Technol. 2007 ,57, 85–93. [CrossRef] 37. Lou, W.; Kane, A.; Wolbert, D.; Rtimi, S.; Assadi, A.A. Study of a photocatalytic process for removal of antibiotics from wastewater in a falling film photoreactor: Scavenger study and process intensification feasibility. Chem. Eng. Process. Process. Intensif. 2017 , 122, 213–221. [CrossRef] 38. Hong, P.; Li, Y.; He, J.; Saeed, A.; Zhang, K.; Wang, C.; Kong, L.; Liu, J. Rapid degradation of aqueous doxycycline by surface CoFe2O4/H2O2system: Behaviors, mechanisms, pathways and DFT calculation. Appl. Surf. Sci. 2020,526, 146557. [CrossRef] 39. Aguilar-Melo, C.; Rodríguez, J.L.; Chairez, I.; Tiznado, H.; Poznyak, T. Naphthalene degradation by catalytic ozonation based on nickel oxide: Study of the ethanol as cosolvent. Environ. Sci. Pollut. Res. 2016,24, 25550–25560. [CrossRef] 40. Tanaka, K.; Abe, K.; Hisanaga, T. Photocatalytic water treatment on immobilized TiO 2 combined with ozonation. J. Photochem. Photobiol. A Chem. 1996,101, 85–87. [CrossRef] 41. Aguinaco, A.; Beltran, F.J.; García-Araya, J.F.; Oropesa, A.L. Photocatalytic ozonation to remove the pharmaceutical diclofenac from water: Influence of variables. Chem. Eng. J. 2012,189-190, 275–282. [CrossRef] 42. García, J.; Oliveira, J.; Silva, A.; Oliveira, C.; Nozaki, J.; De Souza, N. Comparative study of the degradation of real textile effluents by photocatalytic reactions involving UV/TiO 2 /H 2 O 2 and UV/Fe 2 +/H 2 O 2 systems. J. Hazard. Mater. 2007 ,147, 105–110. [CrossRef] 43. Kümmerer, K. The presence of pharmaceuticals in the environment due to human use—Present knowledge and future challenges. J. Environ. Manag. 2009,90, 2354–2366. [CrossRef] [PubMed] 44. Naidu, R.; Jit, J.; Kennedy, B.; Arias, V. Emerging contaminant uncertainties and policy: The chicken or the egg conundrum. Chemosphere 2016,154, 385–390. [CrossRef] [PubMed] 45. Bu, Q.; Wang, B.; Huang, J.; Deng, S.; Yu, G. Pharmaceuticals and personal care products in the aquatic environment in China: A review. J. Hazard. Mater. 2013,262, 189–211. [CrossRef] 46. Petrovi´c, M.; Gonzalez, S.; Barceló, D. Analysis and removal of emerging contaminants in wastewater and drinking water. Trends Anal. Chemistry 2003,22, 685–696. [CrossRef] 47. Carballa, M.; Omil, F.; Lema, J.M.; Llompart, M.; García-Jares, C.; Rodríguez, I.; Gomez, M.; Ternes, T. Behavior of pharmaceuticals, cosmetics and hormones in a sewage treatment plant. Water Res. 2004,38, 2918–2926. [CrossRef] 48. Rivera-Utrilla, J.; Sánchez-Polo, M.; Ferro-García, M.Á.; Prados-Joya, G.; Ocampo-Pérez, R. Pharmaceuticals as emerging contaminants and their removal from water. A review. Chemosphere 2013,93, 1268–1287. [CrossRef] 49. Jiang, J.-Q.; Zhou, Z.; Sharma, V. Occurrence, transportation, monitoring and treatment of emerging micro-pollutants in waste water—A review from global views. Microchem. J. 2013,110, 292–300. [CrossRef] 50. Michael, S.G.; Michael-Kordatou, I.; Nahim-Granados, S.; Polo-López, M.I.; Rocha, J.; Martínez-Piernas, A.B.; Fernández-Ibáñez, P.; Agüera, A.; Manaia, C.M.; Fatta-Kassinos, D. Investigating the impact of UV-C/H 2 O 2 and sunlight/H 2 O 2 on the removal of antibiotics, antibiotic resistance determinants and toxicity present in urban wastewater. Chem. Eng. J. 2020 ,388, 124383. [CrossRef] 51. Gao, Y.-Q.; Zhang, J.; Li, C.; Tian, F.-X.; Gao, N.-Y. Comparative evaluation of metoprolol degradation by UV/chlorine and UV/H2O2processes. Chemosphere 2020,243, 125325. [CrossRef] 52. Tayo, L.L.; Caparanga, A.R.; Doma, B.T.; Liao, C.-H. A Review on the removal of Pharmaceutical and Personal Care Products (PPCPs) using advanced oxidation processes. J. Adv. Oxid. Technol. 2018,21, 196–214. [CrossRef] 53. Yan, C.; Yang, Y.; Zhou, J.; Liu, M.; Nie, M.; Shi, H.; Gu, L. Antibiotics in the surface water of the Yangtze estuary: Occurrence, distribution and risk assessment. Environ. Pollut. 2013,175, 22–29. [CrossRef] Water 2021,13, 2094 17 of 19 54. Oviedo Cordoba, H.; Cortina Navarro, C.E.; Osorio Coronel, J.A.; Romero Torres, S.M. Realidades de la práctica de la automedicación en estudiantes de la Universidad del Magdalena. Enfermería Global. 2021,20, 531–556. [CrossRef] 55. Jardim, W.F.; Montagner, C.C.; Pescara, I.C.; Umbuzeiro, G.; Bergamasco, A.M.D.D.; Eldridge, M.L.; Sodré, F.F. An integrated approach to evaluate emerging contaminants in drinking water. Sep. Purif. Technol. 2012,84, 3–8. [CrossRef] 56. Bletsou, A.A.; Jeon, J.; Hollender, J.; Archontaki, E.; Thomaidis, N.S. Targeted and non-targeted liquid chromatography-mass spectrometric workflows for identification of transformation products of emerging pollutants in the aquatic environment. TrAC Trends Anal. Chem. 2015,66, 32–44. [CrossRef] 57. Monteoliva-García, A.; Martín-Pascual, J.; Muñío, M.M.; Poyatos, J.M. Removal of carbamazepine, ciprofloxacin and ibuprofen in real urban wastewater by using light-driven advanced oxidation processes. Int. J. Environ. Sci. Technol. 2019 ,16, 6005–6018. [CrossRef] 58. Yuan, F.; Hu, C.; Hu, X.; Wei, D.; Chen, Y.; Qu, J. Photodegradation and toxicity changes of antibiotics in UV and UV/H 2 O 2 process. J. Hazard. Mater. 2011,185, 1256–1263. [CrossRef] 59. Rosal, R.; Rodríguez, A.; Melon, J.A.P.; Mezcua, M.; Hernando, D.; Leton, P.; Calvo, E.G.; Agüera, A.; Fernández-Alba, A. Removal of pharmaceuticals and kinetics of mineralization by O 3 /H 2 O 2 in a biotreated municipal wastewater. Water Res. 2008 , 42, 3719–3728. [CrossRef] 60. De Witte, B.; Dewulf, J.; Demeestere, K.; Van Langenhove, H. Ozonation and advanced oxidation by the peroxone process of ciprofloxacin in water. J. Hazard. Mater. 2009,161, 701–708. [CrossRef] [PubMed] 61. Lekkerkerker-Teunissen, K.; Benotti, M.J.; Snyder, S.; van Dijk, H.C. Transformation of atrazine, carbamazepine, diclofenac and sulfamethoxazole by low and medium pressure UV and UV/H2O2treatment. Sep. Purif. Technol. 2012,96, 33–43. [CrossRef] 62. Yang, Y.; Lu, X.; Jiang, J.; Ma, J.; Liu, G.; Cao, Y.; Liu, W.; Li, J.; Pang, S.; Kong, X.; et al. Degradation of sulfamethoxazole by UV, UV/H 2 O 2 and UV/persulfate (PDS): Formation of oxidation products and effect of bicarbonate. Water Res. 2017 ,118, 196–207. [CrossRef] [PubMed] 63. Kim, T.-H.; Kim, S.D.; Kim, H.Y.; Lim, S.J.; Lee, M.; Yu, S. Degradation and toxicity assessment of sulfamethoxazole and chlortetracycline using electron beam, ozone and UV. J. Hazard. Mater. 2012,227-228, 237–242. [CrossRef] [PubMed] 64. Jung, Y.J.; Kim, W.G.; Yoon, Y.; Kang, J.-W.; Hong, Y.M.; Kim, H.W. Removal of amoxicillin by UV and UV/H2O2processes. Sci. Total Environ. 2012,420, 160–167. [CrossRef] 65. Elmolla, E.S.; Chaudhuri, M. Photocatalytic degradation of amoxicillin, ampicillin and cloxacillin antibiotics in aqueous solution using UV/TiO2and UV/H2O2/TiO2photocatalysis. Desalination 2010,252, 46–52. [CrossRef] 66. Torre, J.A.C.; Lehmann Ah González, C.; Carmona Em Muñoz, A.H. Presencia de Fármacos en Aguas Residuales y Eficacia de los Procesos Convencionales en su Eliminación; Cátedra de Ingeriería Sanidad y Ambiente de la ETS Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid: Madrid, Spain, 2006. 67. Shemer, H.; Kunukcu, Y.K.; Linden, K.G. Degradation of the pharmaceutical Metronidazole via UV, Fenton and photo-Fenton processes. Chemosphere 2006,63, 269–276. [CrossRef] 68. Andreozzi, R.; Canterino, M.; Giudice, R.L.; Marotta, R.; Pinto, G.; Pollio, A. Lincomycin solar photodegradation, algal toxicity and removal from wastewaters by means of ozonation. Water Res. 2006,40, 630–638. [CrossRef] [PubMed] 69. Alharbi, S.K.; Kang, J.; Nghiem, L.; van de Merwe, J.; Leusch, F.; Price, W.E. Photolysis and UV/H 2 O 2 of diclofenac, sulfamethoxazole, carbamazepine, and trimethoprim: Identification of their major degradation products by ESI–LC–MS and assessment of the toxicity of reaction mixtures. Process. Saf. Environ. Prot. 2017,112, 222–234. [CrossRef] 70. Ternes, T.A.; Meisenheimer, M.; McDowell, D.; Sacher, F.; Brauch, H.-J.; Haist-Gulde, B.; Preuss, G.; Wilme, U.; Zulei-Seibert, N. Removal of pharmaceuticals during drinking water treatment. Environ. Sci. Technol. 2002,36, 3855–3863. [CrossRef] 71. Huber, M.M.; Canonica, S.; Park, G.-Y.; Von Gunten, U. Oxidation of pharmaceuticals during ozonation and advanced oxidation processes. Environ. Sci. Technol. 2003,37, 1016–1024. [CrossRef] 72. Vogna, D.; Marotta, R.; Napolitano, A.; Andreozzi, R.; D’Ischia, M. Advanced oxidation of the pharmaceutical drug diclofenac with UV/H2O2and ozone. Water Res. 2004,38, 414–422. [CrossRef] [PubMed] 73. Andreozzi, R.; Campanella, L.; Fraysse, B.; Garric, J.; Gonnella, A.; Giudice, R.L.; Marotta, R.; Pinto, G.; Pollio, A. Effects of advanced oxidation processes (AOPs) on the toxicity of a mixture of pharmaceuticals. Water Sci. Technol. 2004 ,50, 23–28. [CrossRef] [PubMed] 74. Sein, M.M.; Zedda, M.; Tuerk, J.; Schmidt, T.C.; Golloch, A.; Von Sonntag, C. Oxidation of diclofenac with ozone in aqueous solution. Environ. Sci. Technol. 2008,42, 6656–6662. [CrossRef] [PubMed] 75. Zwiener, C.; Frimmel, F.H. Oxidative treatment of pharmaceuticals in water. Water Res. 2000,34, 1881–1885. [CrossRef] 76. Ravina, M.; Campanella, L.; Kiwi, J. Accelerated mineralization of the drug Diclofenac via Fenton reactions in a concentric photo-reactor. Water Res. 2002,36, 3553–3560. [CrossRef] 77. Ternes, T.A.; Stüber, J.; Herrmann, N.; McDowell, D.; Ried, A.; Kampmann, M.; Teiser, B. Ozonation: A tool for removal of pharmaceuticals, contrast media and musk fragrances from wastewater? Water Res. 2003,37, 1976–1982. [CrossRef] 78. Witte, B.D.; Langenhove, H.V.; Hemelsoet, K.; Demeestere, K.; Wispelaere, P.D.; Van Speybroeck, V.; Dewulf, J. Levofloxacin ozonation in water: Rate determining process parameters and reaction pathway elucidation. Chemosphere 2009 ,76, 683–689. [CrossRef] 79. Lima, V.B.; Goulart, L.A.; Rocha, R.S.; Steter, J.R.; Lanza, M.R. Degradation of antibiotic ciprofloxacin by different AOP systems using electrochemically generated hydrogen peroxide. Chemosphere 2020,247, 125807. [CrossRef] [PubMed] Water 2021,13, 2094 18 of 19 80. Lange, F.; Cornelissen, S.; Kubac, D.; Sein, M.M.; von Sonntag, J.; Hannich, C.B.; Golloch, A.; Heipieper, H.J.; Möder, M.; von Sonntag, C. Degradation of macrolide antibiotics by ozone: A mechanistic case study with clarithromycin. Chemosphere 2006 , 65, 17–23. [CrossRef] 81. Garoma, T.; Umamaheshwar, S.K.; Mumper, A. Removal of sulfadiazine, sulfamethizole, sulfamethoxazole, and sulfathiazole from aqueous solution by ozonation. Chemosphere 2010,79, 814–820. [CrossRef] 82. Chen, X.; Richard, J.; Liu, Y.; Dopp, E.; Tuerk, J.; Bester, K. Ozonation products of triclosan in advanced wastewater treatment. Water Res. 2012,46, 2247–2256. [CrossRef] 83. Ellis, J. Pharmaceutical and personal care products (PPCPs) in urban receiving waters. Environ. Pollut. 2006 ,144, 184–189. [CrossRef] 84. Ebele, A.J.; Abdallah, M.A.-E.; Harrad, S. Pharmaceuticals and personal care products (PPCPs) in the freshwater aquatic environment. Emerg. Contam. 2017,3, 1–16. [CrossRef] 85. Xia, K.; Bhandari, A.; Das, K.; Pillar, G. Occurrence and fate of pharmaceuticals and personal care products (PPCPs) in biosolids. J. Environ. Qual. 2005,34, 91–104. [CrossRef] [PubMed] 86. Lu, G.; Hu, J. Effect of alpha-hydroxy acids on transformation products formation and degradation mechanisms of carbamaz-epine by UV/H2O2process. Sci. Total. Environ. 2019,689, 70–78. [CrossRef] 87. Huang, Y.; Kong, M.; Coffin, S.; Cochran, K.H.; Westerman, D.C.; Schlenk, D.; Richardson, S.D.; Lei, L.; Dionysiou, D.D. Degradation of contaminants of emerging concern by UV/H 2 O 2 for water reuse: Kinetics, mechanisms, and cytotoxicity analysis. Water Res. 2020,174, 115587. [CrossRef] 88. Tay, K.S.; Rahman, N.A.; Bin Abas, M.R. Kinetic studies of the degradation of parabens in aqueous solution by ozone oxidation. Environ. Chem. Lett. 2010,8, 331–337. [CrossRef] 89. De la Cruz, N.; Giménez, J.; Esplugas, S.; Grandjean, D.; de Alencastro, L.F.; Pulgarín, C. Degradation of 32 emergent contaminants by UV and neutral photo-Fenton in domestic wastewater effluent previously treated by activated sludge. Water Res. 2012 ,46, 1947–1957. [CrossRef] [PubMed] 90. Zuccato, E.; Castiglioni, S.; Bagnati, R.; Chiabrando, C.; Grassi, P.; Fanelli, R. Illicit drugs, a novel group of environmental con-taminants. Water Res. 2008,42, 961–968. [CrossRef] 91. Ahmed, F.; Tscharke, B.; O’Brien, J.W.; Cabot, P.J.; Hall, W.D.; Mueller, J.F.; Thomas, K.V. Can wastewater analysis be used as a tool to assess the burden of pain treatment within a population? Environ. Res. 2020,188, 109769. [CrossRef] [PubMed] 92. Du, P.; Zhou, Z.; Bai, Y.; Xu, Z.; Gao, T.; Fu, X.; Li, X. Estimating heroin abuse in major Chinese cities through wastewater-based epidemiology. Sci. Total. Environ. 2017,605–606, 158–165. [CrossRef] 93. Subedi, B.; Kannan, K. Mass loading and removal of select illicit drugs in two wastewater treatment plants in New York State and estimation of illicit drug usage in communities through wastewater analysis. Environ. Sci. Technol. 2014 ,48, 6661–6670. [CrossRef] 94. Been, F.; Benaglia, L.; Lucia, S.; Gervasoni, J.-P.; Esseiva, P.; Delémont, O. Data triangulation in the context of opioids monitoring via wastewater analyses. Drug Alcohol Depend. 2015,151, 203–210. [CrossRef] [PubMed] 95. McCall, A.-K.; Bade, R.; Kinyua, J.; Lai, F.Y.; Thai, P.; Covaci, A.; Bijlsma, L.; van Nuijs, A.; Ort, C. Critical review on the stability of illicit drugs in sewers and wastewater samples. Water Res. 2016,88, 933–947. [CrossRef] [PubMed] 96. Mercan, S.; Kuloglu, M.; Tekin, T.; Turkmen, Z.; Dogru, A.O.; Safran, A.N.; Acikkol, M.; Asicioglu, F. Wastewater-based monitoring of illicit drug consumption in Istanbul: Preliminary results from two districts. Sci Total Environ. 2019 ,656, 231–238. [CrossRef] [PubMed] 97. Damien, D.A.; Thomas, N.; Hélène, P.; Sara, K.; Yves, L. First evaluation of illicit and licit drug consumption based on wastewater analysis in Fort de France urban area (Martinique, Caribbean), a transit area for drug smuggling. Sci. Total Environ. 2014 ,490, 970–978. [CrossRef] [PubMed] 98. Kasprzyk-Hordern, B.; Dinsdale, R.; Guwy, A.J. The occurrence of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs in surface water in South Wales, UK. Water Res. 2008,42, 3498–3518. [CrossRef] 99. Jones-Lepp, T.L.; Alvarez, D.A.; Petty, J.D.; Huckins, J.N. Polar organic chemical integrative sampling and liquid chromatography? Electrospray/ion-trap mass spectrometry for assessing selected prescription and illicit drugs in treated sewage effluents. Arch. Environ. Contam. Toxicol. 2004,47, 427–439. [CrossRef] 100. Huerta-Fontela, M.; Galceran, M.T.; Martin-Alonso, J.; Ventura, F. Occurrence of psychoactive stimulatory drugs in wastewaters in north-eastern Spain. Sci. Total Environ. 2008,397, 31–40. [CrossRef] 101. Spasiano, D.; Russo, D.; Vaccaro, M.; Siciliano, A.; Marotta, R.; Guida, M.; Reis, N.; Puma, G.L.; Andreozzi, R. Removal of benzoylecgonine from water matrices through UV254/H 2 O 2 process: Reaction kinetic modeling, ecotoxicity and genotoxicity assessment. J. Hazard. Mater. 2016,318, 515–525. [CrossRef] 102. Russo, D.; Spasiano, D.; Vaccaro, M.; Cochran, K.H.; Richardson, S.D.; Andreozzi, R.; Puma, G.L.; Reis, N.; Marotta, R. Investigation on the removal of the major cocaine metabolite (benzoylecgonine) in water matrices by UV254 /H 2 O 2 process by using a flow microcapillary film array photoreactor as an efficient experimental tool. Water Res. 2016 ,89, 375–383. [CrossRef] [PubMed] 103. Gooddy, D.C.; Bloomfield, J.P.; Chilton, P.J.; Johnson, A.C.; Williams, R.J. Assessing herbicide concentrations in the saturated and unsaturated zone of a Chalk aquifer in southern England. Ground Water 2001,39, 262–271. [CrossRef] [PubMed] 104. Gooddy, D.C.; Chilton, P.J.; Harrison, I. A field study to assess the degradation and transport of diuron and its metabolites in a calcareous soil. Sci. Total Environ. 2002,297, 67–83. [CrossRef] Water 2021,13, 2094 19 of 19 105. Kolpin, D.W.; Thurman, E.M.; Linhart, S.M. Occurrence of cyanazine compounds in groundwater: Degradates More Prevalent than the parent compound. Environ. Sci. Technol. 2001,35, 1217–1222. [CrossRef] 106. Panno, S.; Kelly, W. Nitrate and herbicide loading in two groundwater basins of Illinois’ sinkhole plain. J. Hydrol. 2004 ,290, 229–242. [CrossRef] 107. Lapworth, D.; Gooddy, D.; Stuart, M.; Chilton, P.; Cachandt, G.; Knapp, M.; Bishop, S. Pesticides in groundwater: Some observations on temporal and spatial trends. Water Environ. J. 2006,20, 55–64. [CrossRef] 108. Hans-Rudolf, B. Atrazine and others-triazine herbicides in lakes and in rain in Switzerland. Environ. Sci. Technol. 1990 ,24, 1049–1058. [CrossRef] 109. Chen, L.; Hu, X.; Yang, Y.; Jiang, C.; Bian, C.; Liu, C.; Zhang, M.; Cai, T. Degradation of atrazine and structurally related s-triazine herbicides in soils by ferrous-activated persulfate: Kinetics, mechanisms and soil-types effects. Chem. Eng. J. 2018,351, 523–531. [CrossRef] 110. Serna-Galvis, E.A.; Botero-Coy, A.M.; Martínez-Pachón, D.; Moncayo-Lasso, A.; Ibáñez, M.; Hernández, F.; Torres-Palma, R.A. Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation pro-cesses. Water Res. 2019,154, 349–360. [CrossRef] 111. Ma, D.; Yi, H.; Lai, C.; Liu, X.; Huo, X.; An, Z.; Li, L.; Fu, Y.; Li, B.; Zhang, M.; et al. Critical review of advanced oxidation processes in organic wastewater treatment. Chemosphere 2021,275, 130104. [CrossRef] 112. Berberidou, C.; Kitsiou, V.; Lambropoulou, D.; Antoniadis, A.; Ntonou, E.; Zalidis, G.C.; Poulios, I. Evaluation of an alternative method for wastewater treatment containing pesticides using solar photocatalytic oxidation and constructed wetlands. J. Environ. Manag. 2017,195, 133–139. [CrossRef] 113. Karaolia, P.; Michael-Kordatou, I.; Hapeshi, E.; Drosou, C.; Bertakis, Y.; Christofilos, D.; Armatas, G.S.; Sygellou, L.; Schwartz, T.; Xekoukoulotakis, N.P.; et al. Removal of antibiotics, antibi-otic-resistant bacteria and their associated genes by graphene-based TiO 2 composite photocatalysts under solar radiation in urban wastewaters. Appl. Catal. B Environ. 2018 ,224, 810–824. [CrossRef] 114. Talwar, S.; Sangal, V.K.; Verma, A. Feasibility of using combined TiO 2 photocatalysis and RBC process for the treatment of real pharmaceutical wastewater. J. Photochem. Photobiol. A Chem. 2018,353, 263–270. [CrossRef] 115. Rueda-Marquez, J.J.; Levchuk, I.; Fernández Ibañez, P.; Sillanpää, M. A critical review on application of photocatalysis for toxicity reduction of real wastewaters. J. Clean. Prod. 2020,258, 120694. [CrossRef] 116. Ibáñez, M.; Lor, E.G.; Bijlsma, L.; Morales, E.; Pastor, L.; Hernandez, F. Removal of emerging contaminants in sewage water subjected to advanced oxidation with ozone. J. Hazard. Mater. 2013,260, 389–398. [CrossRef] 117. Martínez, F.; Molina, R.; Rodríguez, I.; Pariente, M.I.; Segura, Y.; Melero, J.A. Techno-economical assessment of coupling Fen-ton/biological processes for the treatment of a pharmaceutical wastewater. J. Environ. Chem. Eng. 2018 ,6, 485–494. [CrossRef] 118. Olvera-Vargas, H.; Oturan, N.; Buisson, D.; Oturan, M.A. A coupled Bio-EF process for mineralization of the pharmaceuticals furosemide and ranitidine: Feasibility assessment. Chemosphere 2016,155, 606–613. [CrossRef] 119. Ganzenko, O.; Trellu, C.; Oturan, N.; Huguenot, D.; Péchaud, Y.; Van Hullebusch, E.D.; Oturan, M.A. Electro-Fenton treatment of a complex pharmaceutical mixture: Mineralization efficiency and biodegradability enhancement. Chemosphere 2020 ,253, 126659. [CrossRef] [PubMed] 120. Karaolia, P.; Michael-Kordatou, I.; Hapeshi, E.; Alexander, J.; Schwartz, T.; Fatta-Kassinos, D. Investigation of the potential of a membrane BioReactor followed by solar Fenton oxidation to remove antibiotic-related microcontaminants. Chem. Eng. J. 2017 , 310, 491–502. [CrossRef] 121. Lastre-Acosta, A.M.; Palharim, P.H.; Barbosa, I.M.; Mierzwa, J.C.; Teixeira, A.C.S.C. Removal of sulfadiazine from simulated industrial wastewater by a membrane bioreactor and ozonation. J. Environ. Manag. 2020,271, 111040. [CrossRef]