Degradation of macrolide antibiotics by ozone: a mechanistic case study with clarithromycin

Kinetics and mechanisms of nitrate and ammonium formation during ozonation of dissolved organic nitrogen

Dissolved organic nitrogen (DON) is an emerging concern in oxidative water treatment because it exerts oxidant demand and may form nitrogenous oxidation/disinfection by-products. In this study, we investigated the reactions of ozone with DON with a special emphasis on the formation of nitrate (NO₃^-) and ammonium (NH₄⁺). In batch ozonation experiments, the formation of NO₃^- and NH₄⁺ was investigated for natural organic matter standards, surface water, and wastewater effluent samples. A good correlation was found between NO₃^- formation and the O₃ exposure (R² > 0.82) during ozonation of both model DON solutions and real water samples. To determine the main precursor of NO₃^-, solutions composed of tannic acid and model compounds with amine functional groups were ozonated. The NO₃^- yield during ozonation was significantly higher for glycine than for trimethylamine and dimethylamine. Experiments with glycine also showed that NO₃^- was formed via an intermediate with a second-order rate constant of 7.7 ± 0.1 M^-1s^-1 while NH₄⁺ was formed by an electron-transfer mechanism with O₃ as confirmed from a hydroxyl radical (OH) yield of 24.7 ± 1.9%. The NH₄⁺ concentrations, however, were lower than the OH yield (0.03 mol NH₄⁺/mol OH) suggesting other OH-producing reactions that compete with NH₄⁺ formation. This study concludes that NO₃^- formation during ozonation of DON is induced by an oxygen-transfer to nitrogen forming hydroxylamine and oxime, while NH₄⁺ formation is induced by electron-transfer reactions involving C-centered radicals and imine intermediates.

Combination of Fenton processes and biotreatment for wastewater treatment and soil remediation

There is a continuously increasing worldwide concern for the development of wastewater and contaminated soil treatment technologies. Fenton processes and biological treatments have long been used as common technologies for treating wastewater and polluted soil but they still need to be modified because of some defects (high costs of Fenton process and long remediation time of biotreatments). This work first briefly introduced the Fenton technology and biotreatment, and then discussed the main considerations in the construction of a combined system. This review shows a critical overview of recent researches combining Fenton processes (as pre-treatment or post-treatment) with bioremediation for treatment of wastewater or polluted soil. We concluded that the combined treatment can be regarded as a novel and competitive technology. Furthermore, the outlook for potential applications of this combination in different polluted soil and wastewater, as well as the mechanism of combination was also discussed.

Study on enhanced degradation of atrazine by ozonation in the presence of hydroxylamine

Degradation of atrazine (ATZ) by ozonation in the presence of hydroxylamine (HA) was experimentally investigated in this study. The results showed approximately 80% of ATZ was degraded by ozonation in the presence of HA, while only 20% was degraded by ozonation alone. The obvious inhibition of the ATZ degradation by tert-butanol suggested the enhanced ATZ degradation by ozone/HA was primarily attributed to OH. The OH yield was determined to be 25.8%. Additionally, the optimum HA dosage for the ATZ degradation was 4μM, when the ozone dosage was 20μM. The effects of pH, bicarbonate and temperature on ATZ degradation by ozone/HA were investigated in details. Most importantly, the enhanced ATZ degradation by ozonation in the presence of HA was still observed in real water especially at acidic pHs. Furthermore, the potential mechanism of OH formation during the reaction of ozone with HA was proposed herein. Nine products were identified by UPLC/Q-TOF-MS system. The ATZ degradation involved dealkylation, dechlorination-hydroxylation and olefination. The evolutions of the concentrations of three available transformation products including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine in ozone/HA were evaluated and compared with that in ozonation alone.

Ozonation of pyridine and other N-heterocyclic aromatic compounds: Kinetics, stoichiometry, identification of products and elucidation of pathways

Pyridine, pyridazine, pyrimidine and pyrazine were investigated in their reaction with ozone. These compounds are archetypes for heterocyclic aromatic amines, a structural unit that is often present in pharmaceuticals, pesticides and dyestuffs (e.g., enoxacin, pyrazineamide or pyrimethamine). The investigated target compounds react with ozone with rate constants ranging from 0.37 to 57 M(-1) s(-1), hampering their degradation during ozonation. In OH radical scavenged systems the reaction of ozone with pyridine and pyridazine is characterized by high transformation (per ozone consumed) of 55 and 54%, respectively. In non scavenged system the transformation drops to 52 and 12%, respectively. However, in the reaction of pyrimidine and pyrazine with ozone this is reversed. Here, in an OH radical scavenged system the compound transformation is much lower (2.1 and 14%, respectively) than in non scavenged one (22 and 25%, respectively). This is confirmed by corresponding high N-oxide formation in the ozonation of pyridine and pyridazine, but probably low formation in the reaction of pyrimidine and pyrazine with ozone. With respect to reaction mechanisms, it is suggested that ozone adduct formation at nitrogen is the primary step in the ozonation of pyridine and pyridazine. On the contrary, ozone adduct formation to the aromatic ring seems to occur especially in the ozonation of pyrimidine as inferred from hydrogen peroxide yield. However, also OH radical reactions are supposed processes in the case of pyrimidine and in particular for pyrazine, albeit negligible OH radical yields are obtained. The low compound transformation in OH radical scavenged system can prove this. As a result of negligible OH radical yields in all cases (less than 6%) electron transfer as primary reaction pathway plays a subordinate role.

Occurrence, removal and risk assessment of pharmaceutical and personal care products (PPCPs) in an advanced drinking water treatment plant (ADWTP) around Taihu Lake in China

The occurrence and removal of 39 selected pharmaceutical and personal care products (PPCPs) were investigated in an advanced drinking water treatment plant (ADWTP) around Taihu Lake. Fourteen of 39 targeted pharmaceuticals were detected in the raw water. After a series of purification processes, only indomethacin, caffeine and sulfamethoxazole were found in effluent, albeit at concentrations less than 2 ng L(-1). The results of principal component analysis suggested that three main purification processes, oxidation, coagulation combined with sedimentation and filtration combined with bio-degradation, influenced the removal performance of PPCPs. The ecotoxicological and human health risk assessment confirmed that drugs detected in effluent posed no potential toxicity and also suggested that two PPCPs (roxithromycin and sulfamethoxazole), especially sulfamethoxazole, should be seriously considered as candidates for regulatory monitoring and prioritization. Finally, the correlation between removal efficiency and risk quotient indicated that uniform removal efficiency for all PPCPs may not reflect an equal risk control in the ADWTP.

Occurrence and removal of organic micropollutants: An overview of the watch list of EU Decision 2015/495

Although there are no legal discharge limits for micropollutants into the environment, some regulations have been published in the last few years. Recently, a watch list of substances for European Union-wide monitoring was reported in the Decision 2015/495/EU of 20 March 2015. Besides the substances previously recommended to be included by the Directive 39/2013/EU, namely two pharmaceuticals (diclofenac and the synthetic hormone 17-alpha-ethinylestradiol (EE2)) and a natural hormone (17-beta-estradiol (E2)), the first watch list of 10 substances/groups of substances also refers three macrolide antibiotics (azithromycin, clarithromycin and erythromycin), other natural hormone (estrone (E1)), some pesticides (methiocarb, oxadiazon, imidacloprid, thiacloprid, thiamethoxam, clothianidin, acetamiprid and triallate), a UV filter (2-ethylhexyl-4-methoxycinnamate) and an antioxidant (2,6-di-tert-butyl-4-methylphenol) commonly used as food additive. Since little is known about the removal of most of the substances included in the Decision 2015/495/EU, particularly regarding realistic concentrations in aqueous environmental samples, this review aims to: (i) overview the European policy in the water field; (ii) briefly describe the most commonly used conventional and advanced treatment processes to remove micropollutants; (iii) summarize the relevant data published in the last decade, regarding occurrence and removal in aqueous matrices of the 10 substances/groups of substances that were recently included in the first watch list for European Union monitoring (Decision 2015/495/EU); and (iv) highlight the lack of reports concerning some substances of the watch list, the study of un-spiked aquatic matrices and the assessment of transformation by-products.

Systematic Exploration of Biotransformation Reactions of Amine-Containing Micropollutants in Activated Sludge

The main removal process for polar organic micropollutants during activated sludge treatment is biotransformation, which often leads to the formation of stable transformation products (TPs). Because the analysis of TPs is challenging, the use of pathway prediction systems can help by generating a list of suspected TPs. To complete and refine pathway prediction, comprehensive biotransformation studies for compounds exhibiting pertinent functional groups under environmentally relevant conditions are needed. Because many polar organic micropollutants present in wastewater contain one or several amine functional groups, we systematically explored amine biotransformation by conducting experiments with 19 compounds that contained 25 structurally diverse primary, secondary, and tertiary amine moieties. The identification of 144 TP candidates and the structure elucidation of 101 of these resulted in a comprehensive view on initial amine biotransformation reactions. The reactions with the highest relevance were N-oxidation, N-dealkylation, N-acetylation, and N-succinylation. Whereas many of the observed reactions were similar to those known for the mammalian metabolism of amine-containing xenobiotics, some N-acylation reactions were not previously described. In general, different reactions at the amine functional group occurred in parallel. Finally, recommendations on how these findings can be implemented to improve microbial pathway prediction of amine-containing micropollutants are given.

Effect of oxidation on amine-based pharmaceutical degradation and N-Nitrosodimethylamine formation

Four pharmaceuticals (ranitidine, nizatidine, doxylamine, and carbinoxamine) were selected as model compounds to assess the efficiency of four oxidants (ozone (O3), chlorine (Cl2), chlorine dioxide (ClO2) and potassium permanganate (KMnO4)) on the removal of amine-based pharmaceutical and personal care products (PPCPs), as well as the reduction of their N-Nitrosodimethylamine formation potentials (NDMAFPs). The changes in PPCPs and their NDMAFPs during oxidation were quantified using various oxidants and dosages. The relationship between oxidation product structures and NDMAFP changes was also analyzed. The results showed that oxidation with O3, Cl2 and ClO2 were effective in removing the selected PPCPs. However, only ozonation was effective in reducing their NDMAFPs. Ozonation at 6 mg/L removed approximately 90% PPCPs and 90% NDMAFPs for all PPCPs. In addition, the results indicated that ozonation products made little contribution to NDMAFPs. In contrast, some PPCP products had higher NDMAFPs than PPCPs after oxidation with Cl2, ClO2 and KMnO4. There were two possible reaction pathways that led to decrease in NDMAFPs after oxidation. One was oxygen transfer to nitrogen at the tertiary amine site and the other was N-dealkylation from the tertiary amine site.

Aquatic toxicity of the macrolide antibiotic clarithromycin and its metabolites

The human macrolide antibiotic clarithromycin is widespread in surface waters. Our study shows that its major metabolite 14-hydroxy(R)-clarithromycin is found in surface waters in comparable amounts. This metabolite is known to be pharmacologically active. Additionally, clarithromycin is partly metabolised to N-desmethyl-clarithromycin, which has no antimicrobial activity. For clarithromycin, some ecotoxicological studies on aquatic organisms have been published. However, many of them are not conform with the scientific principles as given in the "Technical guidance for deriving environmental quality standards" (TGD-EQS), because numerous studies were poorly documented and the methods did not contain analytical measurements confirming that the exposure concentrations were in the range of ± 20% of the nominal concentrations. Ecotoxicological effects of clarithromycin and its two metabolites on the zebrafish Danio rerio (embryo test), the microcrustacean Daphnia magna, the aquatic monocotyledonous macrophyte Lemna minor, the freshwater green alga Desmodesmus subspicatus (Chlorophyta) and the cyanobacterium Anabaena flosaquae were investigated in compliance with the TGD-EQS. Environmental risk assessment was performed using ErC10 values of Anabaena, the species most sensitive to clarithromycin and 14-hydroxy(R)-clarithromycin in our testing. Based oncomparable toxicity and similar concentrations of clarithromycin and its active metabolite 14-hydroxy(R)-clarithromycin in surface waters, an additional multiplication factor of 2 to the assessment factor of 10 on the ErC10 of clarithromycin should be used. Consequently, a freshwater quality standard of 0.130 μg L(-1) is proposed for clarithromycin as the "lead substance". Taking this additional multiplication factor of 2 into account, single monitoring of clarithromycin may be sufficient, in order to reduce the number of substances listed for routine monitoring programs.

Evaluation of the persistence of transformation products from ozonation of trace organic compounds - a critical review

Ozonation is an efficient treatment system to reduce the concentration of trace organic compounds (TrOCs) from technical aquatic systems such as drinking water, wastewater and industrial water, etc. Although it is well established that ozonation generally improves the removal of organic matter in biological post-treatment, little is known about the biodegradability of individual transformation products resulting from ozonation of TrOCs. This publication provides a qualified assessment of the persistence of ozone-induced transformation products based on a review of published product studies and an evaluation of the biodegradability of transformation products with the biodegradability probability program (BIOWIN) and the University of Minnesota Pathway Prediction System (UM-PPS). The oxidation of TrOCs containing the four major ozone-reactive sites (olefins, amines, aromatics and sulfur-containing compounds) follows well described reaction pathways leading to characteristic transformation products. Assessment of biodegradability revealed a high sensitivity to the formed products and hence the ozone-reactive site present in the target compound. Based on BIOWIN, efficient removal can be expected for products from cleavage of olefin groups and aromatic rings. In contrast, estimations and literature indicate that hydroxylamines and N-oxides, the major products from ozonation of secondary and tertiary amines are not necessarily better removed in biological post-treatment. According to UM-PPS, degradation of these products might even occur via reformation of the corresponding amine. Some product studies with sulfide-containing TrOCs showed a stoichiometric formation of sulfoxides from oxygen transfer reactions. However, conclusions on the fate of transformation products in biological post-treatment cannot be drawn based on BIOWIN and UM-PPS.

Prediction of micropollutant elimination during ozonation of a hospital wastewater effluent

Determining optimal ozone doses for organic micropollutant elimination during wastewater ozonation is challenged by the presence of a large number of structurally diverse micropollutants for varying wastewater matrice compositions. A chemical kinetics approach based on ozone and hydroxyl radical (·OH) rate constant and measurements of ozone and ·OH exposures is proposed to predict the micropollutant elimination efficiency. To further test and validate the chemical kinetics approach, the elimination efficiency of 25 micropollutants present in a hospital wastewater effluent from a pilot-scale membrane bioreactor (MBR) were determined at pH 7.0 and 8.5 in bench-scale experiments with ozone alone and ozone combined with H2O2 as a function of DOC-normalized specific ozone doses (gO3/gDOC). Furthermore, ozone and ·OH exposures, ·OH yields, and ·OH consumption rates were determined. Consistent eliminations as a function of gO3/gDOC were observed for micropollutants with similar ozone and ·OH rate constants. They could be classified into five groups having characteristic elimination patterns. By increasing the pH from 7.0 to 8.5, the elimination levels increased for the amine-containing micropollutants due to the increased apparent second-order ozone rate constants while decreased for most micropollutants due to the diminished ozone or ·OH exposures. Increased ·OH quenching by effluent organic matter and carbonate with increasing pH was responsible for the lower ·OH exposures. Upon H2O2 addition, the elimination levels of the micropollutants slightly increased at pH 7 (<8%) while decreased considerably at pH 8.5 (up to 31%). The elimination efficiencies of the selected micropollutants could be predicted based on their ozone and ·OH rate constants (predicted or taken from literature) and the determined ozone and ·OH exposures. Reasonable agreements between the measured and predicted elimination levels were found, demonstrating that the proposed chemical kinetics method can be used for a generalized prediction of micropollutant elimination during wastewater ozonation. Out of 67 analyzed micropollutants, 56 were present in the tested hospital wastewater effluent. Two-thirds of the present micropollutants were found to be ozone-reactive and efficiently eliminated at low ozone doses (e.g., >80% for gO3/gDOC = 0.5).

Transformation of pharmaceuticals during oxidation/disinfection processes in drinking water treatment

Pharmaceuticals are emerging contaminants of concern and are widespread in the environment. While the levels of these substances in finished drinking waters are generally considered too low for human health concern, there are now concerns about their disinfection by-products (DBPs) that can form during drinking water treatment, which in some cases have been proven to be more toxic than the parent compounds. The present manuscript reviews the transformation products of pharmaceuticals generated in water during different disinfection processes, i.e. chlorination, ozonation, chloramination, chlorine dioxide, UV, and UV/hydrogen peroxide, and the main reaction pathways taking place. Most of the findings considered for this review come from controlled laboratory studies involving reactions of pharmaceuticals with these oxidants used in drinking water treatment.

Year-long evaluation on the occurrence and fate of pharmaceuticals, personal care products, and endocrine disrupting chemicals in an urban drinking water treatment plant

The occurrence and removal of thirty representative pharmaceutical and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) in an urban drinking water treatment plant (DWTP) were investigated for a period of one year to evaluate current system's treatment efficacy and assess occurrence of PPCPs and EDCs in finished drinking water. Results showed that the average total PPCPs and EDCs concentration in the surface water source was around 360 ng/L (median concentration = 340 ng/L) with 57% coefficient of variation (CV). The median concentrations of most of the individual PPCPs and EDCs in the surface water were below 15 ng/L except for N,N-diethyltoluamide (DEET) and nonylphenol, which were at 122 and 83 ng/L, respectively. The compounds DEET, nonylphenol, ibuprofen, triclosan, atrazine, tris(2-chloroethyl)-phosphate (TCEP), bisphenol-A, and caffeine (in the order of decreasing median concentration) were among twenty compounds detected at least once in the surface water, while all of the above detected compounds, except two, were also detected in the finished drinking water. The average total PPCPs and EDCs concentration in the finished drinking water was around 98 ng/L (median concentration = 96 ng/L) with 66% CV. The median concentrations of most detected PPCPs and EDCs in drinking water were below 5 ng/L except for DEET and nonylphenol, which were at 12 and 20 ng/L, respectively. There was a strong correlation (r = 0.97) between PPCPs and EDCs' concentrations in the source water and in the drinking water over the one-year study period when data points from two sampling events with unusual removals were excluded. Individual water treatment unit processes showed greater temporal variations of PPCPs and EDCs removal efficiencies than the overall treatment processes. The removal efficiencies also varied greatly among different PPCPs and EDCs. The average removal for total PPCPs and EDCs was 76 ± 18% at the DWTP, with ozonation showing the highest removal efficiency. Based on the similar occurrence and removal trends observed as that of total PPCPs and EDCs in this study, DEET and nonylphenol can be considered as potential indicator compounds for predicting the occurrence and removal of total PPCPs and EDCs in surface water. No strong correlations could be found between total PPCPs and EDCs removal and the removal of suspended solids, turbidity, or organic carbon.

Hydroxylation and hydrolysis: two main metabolic ways of spiramycin I in anaerobic digestion

The anaerobic degradation behaviors of five macrolides including spiramycin I, II, III, midecamycin and josamycin by sludge were investigated. Within 32days, 95% of spiramycin I, II or III was degraded, while the remove rate of midecamycin or josamycin was 75%. SPM I degradation was much higher in nutrition supplementation than that just in sludge. The degradation products and processes of spiramycin I were further characterized. Three molecules, designated P-1, P-2 and P-3 according to their order of occurrence, were obtained and purified. Structural determination was then performed by nuclear magnetic resonance and MS/MS spectra, and data indicated that hydroxylation and hydrolysis were main reactions during the anaerobic digestion of spiramycin I. P-1 is the intermediate of hydroxylation, and P-2 is the intermediate of hydrolysis. P-3 is the final product of the both reaction. This study revealed a hydroxylation and hydrolysis mechanism of macrolide in anaerobic digestion.

A novel approach to modeling the reaction kinetics of tetracycline antibiotics with aqueous ozone

Tetracycline antibiotics represent one of the most successful classes of pharmaceuticals and are extensively used around the world for human and veterinary health. Ozone-based processes have emerged as a selective water treatment process for many pharmaceuticals. The primary objective of this study was to determine the reaction kinetics for transformation of five tetracycline antibiotics (i.e., chlortetracycline, doxycycline, oxytetracycline, rolitetracycline, and tetracycline) by ozone across the pH2 to 9 range. The apparent second-order rate constant for tetracycline was on the order of 1-6 × 10(4) M(-1) s(-1) at low pH, and 0.6-2.0 × 10(6) M(-1) s(-1) at near neutral pH. The apparent second-order rate constants did not fit a conventional pKa-based model, presumably due to the complex acid/base speciation of tetracycline antibiotics. A model that considers the net charge on tetracycline molecules in solution provided a nice fit to experimental data for all five tetracyclines. The five tetracycline antibiotics demonstrated similar reaction kinetics with ozone, and a cumulative analysis of all kinetics data provides a baseline model for other tetracycline compounds. The ozone exposure required for complete transformation of tetracycline antibiotics (10(-5) M-s) is well below that achieved during ozone disinfection processes (10(-3) M-s), indicating that ozone is an effective treatment for tetracycline antibiotics.

Pharmaceuticals as emerging contaminants and their removal from water. A review

The main objective of this study was to conduct an exhaustive review of the literature on the presence of pharmaceutical-derived compounds in water and on their removal. The most representative pharmaceutical families found in water were described and related water pollution issues were analyzed. The performances of different water treatment systems in the removal of pharmaceuticals were also summarized. The water treatment technologies were those based on conventional systems (chlorine, chlorine dioxide, wastewater treatment plants), adsorption/bioadsorption on activated carbon (from lotus stalks, olive-waste cake, coal, wood, plastic waste, cork powder waste, peach stones, coconut shell, rice husk), and advanced oxidation processes by means of ozonation (O₃, O₃/H₂O₂, O₃/activated carbon, O₃/biological treatment), photooxidation (UV, UV/H₂O₂, UV/K₂S₂O₈, UV/TiO₂, UV/H₂O₂/TiO₂, UV/TiO₂/activated carbon, photo-Fenton), radiolysis (e-Beam, ⁶⁰Co, ¹³⁷Cs. Additives used: H₂O₂, SO₃²⁻, HCO₃⁻, CH₃₋OH, CO₃²⁻, or NO₃⁻), and electrochemical processes (Electrooxidation without and with active chlorine generation). The effect of these treatments on pharmaceutical compounds and the advantages and disadvantages of different methodologies used were described. The most important parameters of the above water treatment systems (experimental conditions, removal yield, pharmaceutical compound mineralization, TOC removal, toxicity evolution) were indicated. The key publications on pharmaceutical removal from water were summarized.

Occurrence and removal of antibiotics in a municipal wastewater reclamation plant in Beijing, China

In this study, we investigated the occurrences and fates of eight quinolones (QNs), nine sulfonamides (SAs), and five macrolides (MCs) in a wastewater reclamation plant (WRP) in Beijing, China. Among all the 22 antibiotics considered, quinolones were the dominant antibiotics in all samples (4916ngL(-1) in influents, 1869ngL(-1) in secondary effluents, 123ngL(-1) in tertiary effluents, and 9200μgkg(-1) in sludge samples), followed by sulfonamides (2961ngL(-1) in influents, 1053ngL(-1) in secondary effluents, 25.9ngL(-1) in tertiary effluents, and 63.7μgkg(-1) in sludge samples) and macrolides (365ngL(-1) in influents, 353ngL(-1) in secondary effluents, 24.7ngL(-1) in tertiary effluents, and 32.7μgkg(-1) in sludge samples). The removal efficiencies of the target antibiotics were limited (-32 to 78%) in the conventional treatment. This study indicated that quinolones were mainly removed from the secondary clarifier, and sulfonamides were degraded in the oxic tank; while macrolides were considered as persistent during the conventional treatment. After the advance treatment, the target antibiotics could be effectively removed at high rates (85-100%), and the risks of antibiotic contamination significantly decreased. However, risk assessment showed that the risk of ofloxacin and erythromycin on organisms in recycled water needed further investigations.

Urban wastewater treatment plants as hotspots for the release of antibiotics in the environment: a review

Urban wastewater treatment plants (UWTPs) are among the main sources of antibiotics' release into various compartments of the environment worldwide. The aim of the present paper is to critically review the fate and removal of various antibiotics in wastewater treatment, focusing on different processes (i.e. biological processes, advanced treatment technologies and disinfection) in view of the current concerns related to the induction of toxic effects in aquatic and terrestrial organisms, and the occurrence of antibiotics that may promote the selection of antibiotic resistance genes and bacteria, as reported in the literature. Where available, estimations of the removal of antibiotics are provided along with the main treatment steps. The removal efficiency during wastewater treatment processes varies and is mainly dependent on a combination of antibiotics' physicochemical properties and the operating conditions of the treatment systems. As a result, the application of alternative techniques including membrane processes, activated carbon adsorption, advanced oxidation processes (AOPs), and combinations of them, which may lead to higher removals, may be necessary before the final disposal of the effluents or their reuse for irrigation or groundwater recharge.

Consumption and occurrence of pharmaceutical and personal care products in the aquatic environment in Spain

The occurrence of sixty pharmaceutically active compounds (PhACs), twenty metabolites and eight personal care products (PCPs) in the aquatic environment in Spain and their predicted environmental concentrations (PECs) were calculated and compared with measured environmental concentrations (MECs) obtained from relevant published research. The occurrence in the aquatic environment was calculated through a mass balance approach considering the following: the number of pharmaceutical prescriptions issued, the amount of pharmaceutical discharged without consumption, consumption, self-medication, pharmacokinetics, treatment in wastewater facilities and discharged to aquatic environment. The estimation of consumption of active compounds of pharmaceuticals was conducted by at least one of the following methodologies: number of commercial packages sold, data for the number of defined daily dose per 1000 inhabitants per day (DHD), and pattern of treatment. Comparison of these methodologies for some compounds showed similar estimated consumption ranges. The highest pharmaceutical occurrence in the aquatic environment was for acetaminophen glucuronide, Galaxolide®, Iso-E-super®, acetaminophen, valsartan, amoxicillin, 2-hydroxy-ibuprofen, iopromide, omeprazole, carbamazepine 10, 11-epoxide, iopamidol, salicylic β-d-O-glucuronide acid, Tonalide®, acetylsalicylic acid (ASA), clarithromycin and iohexol, with releases between 5 and 600 ty(-1). The relation of PEC/MEC was calculated for 58% of the compounds under study, and 64.7% of them had PEC/MEC ratios between 0.5 and 2. PEC values were mostly overestimated (57.4%). The predicted concentrations for pharmaceutical and personal care products (PPCPs) that had a high occurrence in the aquatic environment were very close to the measured concentrations. This research provides information that had not been calculated and analyzed previously, at least for Spain. Estimation of the PECs for pharmaceutical, personal care products and metabolites is a useful tool for identifying compounds that should be considered for environmental concern, and such estimations could be used to improve environmental risk assessment studies.

Spectroscopic study of the degradation of antibiotics and the generation of representative EfOM oxidation products in ozonated wastewater

This study examined effects of ozonation on thirteen fluoroquinolone, macrolide and lincosamide antibiotics present in municipal wastewater. Transformations of effluent organic matter (EfOM) caused by ozonation were characterized using absorbance/fluorescence spectroscopy and high performance size exclusion chromatography (HPSEC). Concentrations of aldehydes and carboxylic acids generated via the oxidation of EfOM were also determined. The absorbance and fluorescence of ozonated wastewater decreased with increasing ozone dose or treatment time. HPSEC data showed that these phenomena corresponded to the oxidation of all EfOM fractions, with some preference towards the degradation of the EfOM molecules with high apparent molecular weight. The removal of antibiotics and production of aldehydes and carboxylic acids were strongly correlated with the changes in both EfOM absorbance and fluorescence. Applications of a model describing the concurrent degradation of trace level contaminants and relative changes of EfOM emission allowed achieving a good fitting between the experimental and modeled ΔC/C(0) vs. ΔA/A(0) and ΔC/C(0) vs. ΔF/F(0) data.

Kinetic and mechanistic investigations of the oxidation of tramadol by ferrate and ozone

The kinetics and oxidation products (OPs) of tramadol (TRA), an opioid, were investigated for its oxidation with ferrate (Fe(VI)) and ozone (O(3)). The kinetics could be explained by the speciation of the tertiary amine moiety of TRA, with apparent second-order rate constants of 7.4 (±0.4) M(-1) s(-1) (Fe(VI)) and 4.2 (±0.3) × 10(4) M(-1) s(-1) (O(3)) at pH 8.0, respectively. In total, six OPs of TRA were identified for both oxidants using Qq-LIT-MS, LTQ-FT-MS, GC-MS, and moiety-specific chemical reactions. In excess of oxidants, these OPs can be further transformed to unidentified OPs. Kinetics and OP identification confirmed that the lone electron pair of the amine-N is the predominant site of oxidant attack. An oxygen transfer mechanism can explain the formation of N-oxide-TRA, while a one-electron transfer may result in the formation of N-centered radical cation intermediates, which could lead to the observed N-dealkylation, and to the identified formamide and aldehyde derivatives via several intermediate steps. The proposed radical intermediate mechanism is favored for Fe(VI) leading predominantly to N-desmethyl-TRA (ca. 40%), whereas the proposed oxygen transfer prevails for O(3) attack resulting in N-oxide-TRA as the main OP (ca. 90%).

Degradation and removal methods of antibiotics from aqueous matrices--a review

Over the past few years, antibiotics have been considered emerging pollutants due to their continuous input and persistence in the aquatic ecosystem even at low concentrations. They have been detected worldwide in environmental matrices, indicating their ineffective removal from water and wastewater using conventional treatment methods. To prevent this contamination, several processes to degrade/remove antibiotics have been studied. This review addresses the current state of knowledge concerning the input sources, occurrence and mainly the degradation and removal processes applied to a specific class of micropollutants, the antibiotics. In this paper, different remediation techniques were evaluated and compared, such as conventional techniques (biological processes, filtration, coagulation, flocculation and sedimentation), advanced oxidation processes (AOPs), adsorption, membrane processes and combined methods. In this study, it was found that ozonation, Fenton/photo-Fenton and semiconductor photocatalysis were the most tested methodologies. Combined processes seem to be the best solution for the treatment of effluents containing antibiotics, especially those using renewable energy and by-products materials.

Combination of Advanced Oxidation Processes and biological treatments for wastewater decontamination--a review

Nowadays there is a continuously increasing worldwide concern for development of alternative water reuse technologies, mainly focused on agriculture and industry. In this context, Advanced Oxidation Processes (AOPs) are considered a highly competitive water treatment technology for the removal of those organic pollutants not treatable by conventional techniques due to their high chemical stability and/or low biodegradability. Although chemical oxidation for complete mineralization is usually expensive, its combination with a biological treatment is widely reported to reduce operating costs. This paper reviews recent research combining AOPs (as a pre-treatment or post-treatment stage) and bioremediation technologies for the decontamination of a wide range of synthetic and real industrial wastewater. Special emphasis is also placed on recent studies and large-scale combination schemes developed in Mediterranean countries for non-biodegradable wastewater treatment and reuse. The main conclusions arrived at from the overall assessment of the literature are that more work needs to be done on degradation kinetics and reactor modeling of the combined process, and also dynamics of the initial attack on primary contaminants and intermediate species generation. Furthermore, better economic models must be developed to estimate how the cost of this combined process varies with specific industrial wastewater characteristics, the overall decontamination efficiency and the relative cost of the AOP versus biological treatment.

Removal of antimicrobials using advanced wastewater treatment

Removal of numerous classes of pharmaceuticals from the municipal and industrial wastewater, using conventional wastewater treatment, is incomplete and several studies suggested that improvement of this situation would require the application of advanced treatment techniques. This is particularly important for the treatment of industrial effluents, released from pharmaceutical industries, which can contain rather high concentrations of antimicrobials. The aim of this work was to evaluate membrane bioreactors (MBRs), nanofiltration, reverse osmosis and ozonation, as well as their combinations, for the removal of antimicrobials from a synthetic wastewater which simulated highly contaminated industrial effluents. The study was performed using a mixture of four important classes of antimicrobials, including sulfonamides (SA), fluoroquinolones (FQ), macrolides (MAC) and trimethoprim (TMP). Performance of two different types of MBRs, Kubota and Zenon, was evaluated under different regimes regarding hydraulic retention time, total organic load and total nitrogen load. It was shown that elimination of SA in MBR treatment was very efficient, while the elimination of MAC, FQ, and TMP was incomplete. A mass balance of these contaminants in MBR suggested that microbial transformation represented the main mechanism, while only a small percentage was eliminated from the aqueous phase by adsorption onto sludge particles. Nanofiltration and reverse osmosis achieved high elimination rates however produced highly contaminated concentrate. High removal was achieved using ozonation, but further research is needed to characterize formed ozonation products.

Degradation of sulfamonomethoxine with Fe3O4 magnetic nanoparticles as heterogeneous activator of persulfate

Iron oxide magnetic nanoparticles (Fe(3)O(4) MNPs) can effectively activate persulfate anions (S(2)O(8)(2-)) to produce sulfate free radicals (SO(4)(-)), which are a powerful oxidant with promising applications to degrade organic contaminants. The kinetics of sulfamonomethoxine (SMM) degradation was studied in the system of Fe(3)O(4) MNPs and S(2)O(8)(2-). A complete removal of the added SMM (0.06 mmol L(-1)) was achieved within 15 min with the addition of 1.20 mmol L(-1) S(2)O(8)(2-) and 2.40 mmol L(-1) Fe(3)O(4) MNPs. There is an optimum concentration of Fe(3)O(4) MNPs because Fe(3)O(4) MNPs may also act as a SO(4)(-) scavenger at higher concentrations. It was further observed that the addition of Fe(3)O(4) MNPs in several batches for a given total amount of the activator is favorable to enhancing the degradation of SMM. A degradation mechanism was proposed on the basis of identification of the degradation intermediates of SMM with liquid chromatography combined with mass spectroscopy.

Ozonation performance of WWTP secondary effluent of antibiotic manufacturing wastewater

The ozonation performance of wastewater treatment plant secondary effluent of oxytetracycline (OTC) manufacturing wastewater was investigated in terms of ozone dosage and initial pH levels when OTC contributed to a negligible fraction in the chemical oxygen demand (COD) ingredients of the medium-organic-strength wastewater with low biodegradability. A particular emphasis was placed on ammonia, OTC, and residual antibacterial activity (RAA) (evaluated using the objective pathogenic bacterium Staphylococcus aureus). It appears that an ozone dosage of 657 mg L⁻¹ (120 min of reaction) was enough to achieve an OTC abatement of 96%, and COD and biochemical oxygen demand removals of 29% and 33%, respectively, at initial levels of 10.4, 1360, and 300 mg L⁻¹ , respectively. There is a clear correlation between complete OTC depletion and complete RAA disappearance with an increase of ozone dosage. The presence of plentiful non-antibiotic refractory substances influenced the determination of the optimum ozone dosage for biodegradability enhancement and OTC/RAA reduction as well as the ozonation transformation of NH(3). The initial pH adjustment from the original level (pH 9) to pH 11 significantly reduced COD removal while RAA and NH(3) levels were not significantly influenced.

Tetracycline degradation by ozonation in the aqueous phase: proposed degradation intermediates and pathway

During the ozonation of tetracycline (TC) in aqueous media at pHs 2.2 and 7.0, the effects of pH variations, protonation and dissociation of functional groups and variation in free radical exposure were investigated to elucidate the transformation pathway. Liquid chromatography-triple quadrupole mass spectrometry detected around 15 ozonation products, and uncovered their production and subsequent degradation patterns. During ozonation at pH 2.2, the TC degradation pathway was proposed on the basis of the structure, ozonation chemistry and mass spectrometry data of TC. Ozonation of TC at the C11a-C12 and C2-C3 double bonds, aromatic ring and amino group generated products of m/z 461, 477, 509 and 416, respectively. Further ozonation at the above mentioned sites gave products of m/z 432, 480, 448, 525 and 496. The removal of TOC reached a maximum of approximately 40% after 2 h of ozonation, while TC was completely removed within 4-6 min at both pHs. The low TOC removal efficiency might be due to the generation of recalcitrant products and the low ozone supply for high TC concentration. Ozonation decreased the acute toxicity of TC faster at pH 7.0 than pH 2.2, but the maximum decrease was only about 40% at both pHs after 2 h of ozonation. In this study, attempts were made to understand the correlation between the transformation products, pathway, acute toxicity and quantity of residual organics in solution. Overall, ozonation was found to be a promising process for removing TC and the products initially generated.

Identification of degradation products of erythromycin A arising from ozone and advanced oxidation process treatment

The degradation products of the macrolide antibiotic erythromycin A (ERY) arising from direct ozone attack and hydroxyl radical attack are presented for the first time. Ozone treatment was carried out by spiking ozone stock solutions to solutions containing ERY-ERY:O3 = 1:5 and 1:10 (M:M), while, in parallel, t-BuOH was used as a hydroxyl radical (*OH) scavenger. The advanced oxidation processes (AOPs) O3/UV, O3/H2O2, and UV/H2O2 were carried out to recognize and verify possible differences between their primary degradation products; the initial concentrations were ERY:O3 = 1:5 (M:M), ERY:O3:H202 = 1:5:5 (M:M:M), or ERY:H202 = 1:5 (M:M), respectively. Six degradation products were identified from ozonation-one originates from direct ozone attack on the tertiary amine group, while the others arise from radical ion attack, which might be formed during degradation of O3 in water. Fewer primary degradation products were observed arising from *OH-based treatments (AOP) than from ozonation, possibly because the reaction of *OH radicals is non-selective and typically is diffusion-controlled. Four degradation products were detected by *OH radical attacks; two of them already were observed during ozonation, with one as an oxidized ERY molecule and the other as a non-oxidized fragment of the ERY molecule.

Fate of antibiotics during municipal water recycling treatment processes

Municipal water recycling processes are potential human and environmental exposure routes for low concentrations of persistent antibiotics. While the implications of such exposure scenarios are unknown, concerns have been raised regarding the possibility that continuous discharge of antibiotics to the environment may facilitate the development or proliferation of resistant strains of bacteria. As potable and non-potable water recycling schemes are continuously developed, it is imperative to improve our understanding of the fate of antibiotics during conventional and advanced wastewater treatment processes leading to high-quality water reclamation. This review collates existing knowledge with the aim of providing new insight to the influence of a wide range of treatment processes to the ultimate fate of antibiotics during conventional and advanced wastewater treatment. Although conventional biological wastewater treatment processes are effective for the removal of some antibiotics, many have been reported to occur at 10-1000 ng L(-1) concentrations in secondary treated effluents. These include beta-lactams, sulfonamides, trimethoprim, macrolides, fluoroquinolones, and tetracyclines. Tertiary and advanced treatment processes may be required to fully manage environmental and human exposure to these contaminants in water recycling schemes. The effectiveness of a range of processes including tertiary media filtration, ozonation, chlorination, UV irradiation, activated carbon adsorption, and NF/RO filtration has been reviewed and, where possible, semi-quantitative estimations of antibiotics removals have been provided.

Transformation of beta-lactam antibacterial agents during aqueous ozonation: reaction pathways and quantitative bioassay of biologically-active oxidation products

Reactions of ozone (O3) with the beta-lactam antibiotics penicillin G (PG) and cephalexin (CP) have previously been found to yield products retaining antibacterial activities. These products are unequivocally identified here as the stereoisomeric (R)-sulfoxides of each parent molecule and characterized by a combination of chemical analysis and an antibacterial activity assay. PG-(R)-sulfoxide, which is approximately 15% as potent as PG itself, is formed in approximately 55% yield, whereas CP-(R)-sulfoxide, which is 83% as active as CP, is formed with a maximum 34% yield. PG-(R)-sulfoxide is recalcitrant toward further oxidation by O3, but readily transformed by hydroxyl radical (HO*) (kHO*,app"=7.4x10(9) M(-1) s(-1), pH 7), resulting in quantitative elimination of its antibacterial activity. In contrast, CP-(R)-sulfoxide is degraded by both O3 and HO* (kO3,app"=2.6x10(4) M(-1) s(-1) and kHO*,app"= 7.6x10(9) M(-1) s(-1), pH 7), leading to quantitative elimination of its antibacterial activity. During ozonation of a secondary municipal wastewater effluent sample (pH 8.1, CDOC=4.0 mg/L, [alkalinity]=3.6 mM as HCO3-) spiked with [PG]0=1 microM, PG-(R)-sulfoxide yields did not exceed 0.15 microM for O3 doses up to 100 microM (4.8 mg/L), but reached 0.47 microM with 10-mM t-BuOH added as a HO* scavenger. In contrast, CP-(R)-sulfoxide yields did not exceed 0.1 microM for the same wastewater spiked with [CP]0=1 microM in either the presence or absence of t-BuOH, indicating that CP-(R)-sulfoxide transformation is governed primarily by direct reaction with O3. These findings suggest that, for a given degree of parent compound transformation, PG-(R)-sulfoxide yields would likely be greatest during ozonation of wastewaters characterized by low O3 demands and high HO* scavenging rates, whereas CP-(R)-sulfoxide yields would be less matrix-dependent. In general, complete deactivation of penicillins during wastewater treatment will likely require higher O3 exposures than necessary for deactivation of cephalosporins.

Evidencing generation of persistent ozonation products of antibiotics roxithromycin and trimethoprim

The mechanism of product formation during ozonation of two widely used antimicrobial agents, macrolide roxithromycin and inhibitor of dihydrofolate reductase (DHFR) trimethoprim was studied in laboratory-scale experiments with two types of matrix: distilled water and secondary wastewater effluent The structures ofthe primary and secondary reaction intermediates were elucidated byquadrupole-time-of-flight (QqToF) instrument, showing that in spite of their high ozone affinity both roxithromycin and trimethoprim oxidation pathway involve to a great degree the *OH radical chain reactions. In total nine ozonation products were detected, whereas two products of roxithromycin exhibited high refractoriness to ozonation, especially in the case of distilled water. Furthermore, the intact tertiary amine moiety of roxithromycin in these products suggests that the antimicrobial activity of the parent compound will be preserved.

Ozonation of wastewater: rate of ozone consumption and hydroxyl radical yield

For the prediction of the elimination efficiency of micropollutants from wastewater by ozone, the ozone rate constants of the micropollutants and the kinetics of the reaction of ozone with wastewater must be known. The latter is multiphasic with k = 0.071 (mg DOC)(-1) s(-1) for the first mg/L ozone (at a DOC of 7.2 mg/L) followed by 0.011 (mg DOC)(-1) s(-1) the next 5 mg/L ozone and the k = 0.0019 (mg DOC)(-1) s(-1) for subsequent 4 mg/L ozone as determined by stopped-flow and batch-quench methods. An analysis of gel permeation and UV absorption data indicates that the wastewater DOC is largely polymeric, and at 12 mg/L the concentration of its subunits must be near 100 microM with epsilon(254 nm) approximately 3000 M(-1) cm(-1). The *OH radical yield as determined by the tertiary butanol assay is approximately 13%. From its dose dependence, it follows that new *OH-generating sites are formed during ozonation. The *OH scavenging capacity of the wastewater DOC has been determined at 3 x 10(4) (mg DOC)(-1) s(-1). The contribution of bicarbonate to the OH scavenging capacity is small in comparison, approximately 10% of DOC. Simulations indicate that at 5 mg/L ozone only the most reactive (k > 3 x 10(30 M(-1) s(-1)) micropollutants are fully eliminated but at 10 mg/L ozone the slow ozone decay starts to contribute and even the much less reactive ones (k = 300 M(-1) s(-1)) are oxidized (25% remaining).

Rhamnolipid biosurfactants decrease the toxicity of chlorinated phenols to Pseudomonas putida DOT-T1E

AIMS

To investigate the effect of a mixture of rhamnolipid R1 and R2 biosurfactants produced by a Pseudomonas aeruginosa strain on the toxicity of phenol and chlorophenols to Pseudomonas putida DOT-T1E.

METHODS AND RESULTS

Toxicity was quantified by the effective concentration 50% (EC50), that is the concentration that causes a 50% inhibition of bacterial growth. The presence of 300 mg l(-1) rhamnolipids, that is at about twice their critical micelle concentration (CMC), increased the EC50 of phenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,5-trichlorophenol by about 12, 19, 32 and 40%, respectively, and consequently reduced the bioavailability and the freely dissolved concentration of the toxic phenolic compounds. The reduction was related to the phenols' octanol-water partition coefficients (K(ow)).

CONCLUSIONS

The reduction in toxicity of the phenols can be explained by a combination of toxin accumulation in biosurfactant micelles and hydrophobic interactions of the phenols with rhamnolipid-based dissolved organic carbon.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results provide evidence that next to the effect of the micelle formation also hydrophobic interactions with rhamnolipid-based dissolved organic carbon affects the bioavailability of the phenols. Quantifying the effect of biosurfactants on the toxicity of hydrophobic compounds such as phenols thus appears to be a useful approach to assess their bioavailable equilibrium concentration.

Oxidation of antibacterial compounds by ozone and hydroxyl radical: elimination of biological activity during aqueous ozonation processes

A wide variety of antibacterial compounds is rapidly oxidized by 03 and hydroxyl radical (*OH) during aqueous ozonation. Quantitative microbiological assays have been developed here or adapted from existing methods and utilized to measure the resulting changes in antibacterial potencies during O3 and *OH treatment of 13 antibacterial molecules (roxithromycin, azithromycin, tylosin, ciprofloxacin, enrofloxacin, penicillin G, cephalexin, sulfamethoxazole, trimethoprim, lincomycin,tetracycline, vancomycin, and amikacin) from 9 structural classes (macrolides, fluoroquinolones, beta-lactams, sulfonamides, dihydrofolate reductase inhibitors, lincosamides, tetracyclines, glycopeptides, and aminoglycosides), as well as the biocide triclosan. Potency measurements were determined from dose-response relationships obtained by exposing Escherichia coli or Bacillus subtilis reference strains to treated samples of each antibacterial compound via broth micro- or macrodilution assays and related to the measured residual concentrations of parent antibacterial in each sample. Data obtained from these experiments show that O3 and *OH reactions lead in nearly all cases to stoichiometric elimination of antibacterial activity (i.e., loss of 1 mole equivalent of potency per mole of parent compound consumed). The beta-lactams penicillin G (PG) and cephalexin (CP) represent the only clear exceptions, as bioassay measurements indicate that biologically active products may be formed in the reactions of these two compounds with both O3 and *OH. The active product(s) generated in the direct reaction of O3 with PG appear(s) to be recalcitrant to further transformation by O3, though any biologically active products formed in the reactions of CP with O3, or of either PG or CP with *OH, are apparently deactivated by further reactions with O3 or *OH, respectively. Thus, with few exceptions, it can be expected that municipal wastewater ozonation will generally yield sufficient structural modification of antibacterial molecules to eliminate their antibacterial activities, whether oxidation results from selective reactions with O3 or from relatively nonselective reactions with incidentally produced OH.

Removal of residual pharmaceuticals from aqueous systems by advanced oxidation processes

Over the past few years, pharmaceuticals are considered as an emerging environmental problem due to their continuous input and persistence to the aquatic ecosystem even at low concentrations. Advanced oxidation processes (AOPs) are technologies based on the intermediacy of hydroxyl and other radicals to oxidize recalcitrant, toxic and non-biodegradable compounds to various by-products and eventually to inert end-products. The environmental applications of AOPs are numerous, including water and wastewater treatment (i.e. removal of organic and inorganic pollutants and pathogens), air pollution abatement and soil remediation. AOPs are applied for the abatement of pollution caused by the presence of residual pharmaceuticals in waters for the last decade. In this light, this paper reviews and assesses the effectiveness of various AOPs for pharmaceutical removal from aqueous systems.

Oxidative transformations of environmental pharmaceuticals by Cl₂, ClO₂, O₃, and Fe(VI): kinetics assessment

Several pharmaceuticals have been detected globally in surface water and drinking water, which indicate their insufficient removal from water and wastewater using conventional treatment methods. This paper reviews the kinetics of oxidative transformations of pharmaceuticals (antibiotics, lipid regulators, antipyretics, anticonvulsants, and beta-blockers) by Cl(2), ClO(2), O(3), and ferrate(VI) (Fe(VI)O(4)(2-),Fe(VI)) under treatment conditions. In the chlorination of sulfonamide antibiotics, HOCl is the major reactive Cl(2) species whereas in the oxidation by Fe(VI), HFeO(4)(-) is the dominant reactive species. Both oxidation processes can oxidize sulfonamides in seconds at a neutral pH (t(1/2)≤ 220 s; 1 mg L(-1) HOCl or K(2)FeO(4)). The reactivity of O(3) with pharmaceuticals is generally higher than that of HOCl (k(app,pH 7) (O(3))=1-10(7)M(-1)s(-1); k(app,pH 7) (HOCl)=10(-2)-10(5)M(-1)s(-1)). Ozone selectively oxidizes pharmaceuticals and reacts mainly with activated aromatic systems and non-protonated amines. Oxidative transformation of most pharmaceuticals by O(3) occurs in seconds (t(1/2)≤ 100 s; 1 mg L(-1) O(3)) while half-lives for oxidations by HOCl differ by at least two orders of magnitude. Ozone appears to be efficient in oxidizing pharmaceuticals in aquatic environments. The limited work on Fe(VI) shows that it can also potentially transform pharmaceuticals in treatment processes.

Oxidation of diclofenac with ozone in aqueous solution

Ozonation of diclofenac in aqueous solution in the presence and absence of an *OH scavenger, tertiary butanol (t-BuOH), was studied, and the most important reaction intermediates and products were identified. The second-order O3 rate constantwas determined by competition with buten-3-ol and was found to be 6.8 x 10(5) M(-1) s(-1) at 20 degrees C. From this high rate constant, it has been concluded that O3 must initially add on the amino nitrogen. Decomposition of the adduct results in the formation of O3*- (--> *OH) and aminyl radical precursors. A free *OH yield of 30% was estimated based on the HCHO yields generated upon reaction of *OH with 0.01 M t-BuOH. Almost all diclofenac reacted when the molar ratio of O3/diclofenac was approximately 5:1 in the presence of t-BuOH and approximately 8:1 in its absence. As primary reaction products (maximum yield), diclofenac-2,5-iminoquinone (32%), 5-hydroxydiclofenac (7%), and 2,6-dichloroaniline (19%) were detected with respect to reacted diclofenac in the presence of t-BuOH. These primary products degraded into secondary ones when the O3 dose was increased. In the *OH-mediated reaction (absence of t-BuOH) small yields of 5-hydroxydiclofenac (4.5%), diclofenac-2,5-iminoquinone (2.7%), and 2,6-dichloroaniline (6%) resulted. Practically all Cl- (95%) was released in the absence of t-BuOH but only about 45% in the presence of t-BuOH at an O3/diclofenac molar ratio of 10: 1. Based on the reaction products, mechanisms that may account for the high O3 consumption during ozonation of diclofenac are suggested. For technical applications, adequate supply of O3 is needed not only to eliminate diclofenac, but also for the degradation of its potentially toxic products like diclofenac-2,5-iminoquinone and 5-hydroxydiclofenac.

Ozonation and advanced oxidation technologies to remove endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) in water effluents

Advanced oxidation processes (AOPs) constitute a promising technology for the treatment of wastewaters containing pharmaceuticals and personal care products (PPCPs) and especially endocrine disrupting chemicals (EDCs). Data concerning the degradation of PPCPs and EDCs by means of AOPs reported during the period January 2000-May 2007 are evaluated in this work. Ozonation was the oxidation process most studied, gives the best expectatives to be applied with successful results.