Oxidation of diclofenac by aqueous chlorine dioxide: identification of major disinfection byproducts and toxicity evaluation

Transformation pathways of enrofloxacin chlorination disinfection by-products in constructed wetlands

Antibiotic residues and their chlorinated disinfection by-products (Cl-DBPs) have adverse effects on organisms in aquaculture water. Taking enrofloxacin (ENR) as target antibiotic, this study investigated the degradation and transformation of ENR Cl-DBPs in constructed wetlands (CWs). Results showed that, ENR and its Cl-DBPs affected the biodegradation of CWs at the preliminary stage, but did not affect the adsorption by plant roots, substrates, and biofilms. The piperazine group of ENR had great electronegativity, and was prone to electrophilic reactions. The carboxyl on quinolone group of ENR had strong nucleophilicity, and was prone to nucleophilic reactions. C atoms with significant negative charges on the aromatic structure of quinolone group were prone to halogenation. During the chlorination of ENR, one pathway was the reaction of quinolone group, in which nucleophilic substitution reaction by chlorine occurred at C26 atom on carboxyl group, then halogenation occurred under the action of Cl+ at C17 site on the aromatic ring; the other pathway was the reaction of piperazine group, in which N7 atom was firstly attacked by HOCl, resulting in piperazine ring cleavage, then followed by deacylation, dealkylation, and halogenation. During the biodegradation of ENR Cl-DBPs, the reactivity of piperazine structure was strong, especially at N6, N7, C13, and C14 sites, while the ring structure of quinolone group was quite stable, and only occurred decyclopropyl at N5 site. Overall, the biodegradation of ENR Cl-DBPs in CWs went through processes including piperazine ring cleavage, tertiary amine splitting, dealkylation, and aldehyde oxidation under the action of coenzymes, in which metabolites such as ketones, aldehydes, carboxylic acids, amides, primary amines, secondary amines, tertiary amines and acetaldehyde esters were produced. Most ENR Cl-DBPs had greater bioaccumulation potential and stronger toxicity than their parent compound, fortunately, CWs effectively reduced the environmental risk of ENR Cl-DBPs through the cooperation of adsorption and biodegradation.

Hydroxylated transformation products of pharmaceutical active compounds: Generation from processes used in wastewater treatment plants and its environmental monitoring

Pharmaceutical active compounds (PhACs) are organic pollutants detected in wastewater and aquatic environments worldwide in concentrations ranging from ng L-1 to μg L-1. Wastewater effluents containing PhACs residues is discharged in municipal sewage and, subsequently collected in municipal wastewater treatment plants (WWTPs) where are not entirely removed. Thus, PhACs and its transformation products (TPs) are discharged into water bodies. In the current work, the transformation of PhACs under treatments used in municipal WWTPs such as biological, photolysis, chlorination, and ozonation processes was reviewed. Data set of the major transformation pathways were obtained of studies that performed the PhACs removal and TPs monitoring during batch-scale experiments using gas and liquid chromatography coupled with tandem mass spectrometry (GC/LC-MS/MS). Several transformation pathways as dealkylation, hydroxylation, oxidation, acetylation, aromatic ring opening, chlorination, dehalogenation, photo-substitution, and ozone attack reactions were identified during the transformation of PhACs. Especially, hydroxylation reaction was identified as transformation pathway in all the processes. During the elucidation of hydroxylated TPs several isobaric compounds as monohydroxylated and dihydroxylated were identified. However, hydroxylated TPs monitoring in wastewater and aquatic environments is a topic scarcely studied due to that has no environmental significance, lack of available analytic standars of hydroxylated TPs and lack of analytic methods for their identification. Thus, screening strategy for environmental monitoring of hydroxylated TPs was proposed through target and suspect screening using GC/LC-MS/MS systems. In the next years, more studies on the hydroxylated TPs monitoring are necessary for its detection in WWTPs effluents as well as studies on their environmental effects in aquatic environments.

Enhanced chlorination of diclofenac using ABTS as electron shuttle: Performance, mechanism and applicability

Chlorination, one of the most common oxidation strategies, performed limited degradation capacity towards many emerging organic contaminants under neutral pH conditions. In this study, 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonate (ABTS) was discovered to possess an outstanding activation property towards free available chlorine (FAC) during the chlorination of diclofenac (DCF) among pH 6.0-9.5. ABTS radical (ABTS•+) primarily accounted for the elimination of DCF in the ABTS/FAC system, although hydroxyl radicals, reactive chlorine species, and singlet oxygen were also generated via the self-decomposition of FAC. ABTS acted as the electron shuttle to degrade DCF in the ABTS/FAC system, where ABTS was firstly oxidized by FAC to ABTS•+ via single electron transfer, and followed by the elimination of DCF with the generated ABTS•+. Eight DCF degradation intermediates were identified by LC/Q-TOF/MS, and four DCF degradation pathways were proposed. Real water bodies, humic acid, and the coexistent anions of Cl-, HCO3-, NO3-, and SO42- performed negligible influence on DCF removal in ABTS/FAC system. ABTS/FAC system was much superior to sole chlorination in terms of toxicity reduction and anti-interference capacity. Overall, this study innovatively introduced ABTS as the electron shuttle to enhance the oxidative capacity of FAC under neutral pH conditions and provided a new insight that the ABTS-like organic/synthetic components might play an important role in degrading emerging organic contaminants by chlorination in water treatment.

Mechanochemical Degradation of Caffeine and Diclofenac Using Biochar of Fique Bagasse in the Presence of Al: Monitoring by Mass Spectrometry

Much research has been carried out to remove emerging contaminants using diverse materials. Furthermore, studies related to pollutant degradation have increased over the past decade. Mechanochemical degradation can successfully decompose molecules that are persistent in the environment. In this study, the biochar of fique bagasse with mixtures SiO2, Al, Al2O3, and Al-Al2O3 was treated with a mechanochemical technique using a planetary ball mill to investigate the degradation of caffeine and diclofenac. These tests resulted in the transformation of caffeine and diclofenac due to the use of Al employing mechanochemistry. In fact, through the use of liquid chromatography coupled with mass spectrometry, eight and six subproducts were identified for caffeine and diclofenac, respectively. Additionally, analysis of the molecules proposed for caffeine and diclofenac transformation suggested hydroxylation, demethylation, decarboxylation, oxidation reactions, and cleavage of the C-C and C-N bonds in the pollutants studied. The formation of these transformation products could be possible by reductant oxygen species generated from the molecular oxygen in the presence of aluminum and the energy delivered for ball milling. The results obtained show the potential application in the environmental management of mechanochemical treatment in the elimination of emerging contaminants caffeine and diclofenac.

Determination and risk assessment of pharmaceutical residues in the urban water cycle in Selangor Darul Ehsan, Malaysia

The environmental fate of non-steroidal anti-inflammatory drugs (NSAIDs) in the urban water cycle is still uncertain and their status is mainly assessed based on specific water components and information on human risk assessments. This study (a) explores the environmental fate of NSAIDs (ibuprofen, IBU; naproxen, NAP; ketoprofen, KET; diazepam, DIA; and diclofenac, DIC) in the urban water cycle, including wastewater, river, and treated water via gas chromatography-mass spectrophotometry (GCMS), (b) assesses the efficiency of reducing the targeted NSAIDs in sewage treatment plant (STP) using analysis of variance (ANOVA), and (c) evaluates the ecological risk assessment of these drugs in the urban water cycle via teratogenic index (TI) and risk quotient (RQ). The primary receptor of contaminants comes from urban areas, as a high concentration of NSAIDs is detected (ranging from 5.87 × 10³ to 7.18 × 10⁴ ng/L). The percentage of NSAIDs removal in STP ranged from 25.6% to 92.3%. The NAP and KET were still detected at trace levels in treated water, indicating the persistent presence in the water cycle. The TI values for NAP and DIA (influent and effluent) were more than 1, showing a risk of a teratogenic effect. The IBU, KET, and DIC had values of less than 1, indicating the risk of lethal embryo effects. The NAP and DIA can be classified as Human Pregnancy Category C (2.1 > TI ≥ 0.76). This work proved that these drugs exist in the current urban water cycle, which could induce adverse effects on humans and the environment (RQ in high and low-risk categories). Therefore, they should be minimized, if not eliminated, from the primary sources of the pollutant (i.e., STPs). These pollutants should be considered a priority to be monitored, given focus to, and listed in the guideline due to their persistent presence in the urban water cycle.

The efficient degradation of diclofenac by ferrate and peroxymonosulfate: performances, mechanisms, and toxicity assessment

In this study, the degradation efficiency and reaction mechanisms of diclofenac (DCF), a nonsteroidal anti-inflammatory drug, by the combination of ferrate (Fe(VI) and peroxymonosulfate (PMS) (Fe(VI)/PMS) were systematically investigated. The higher degradation efficiency of DCF in Fe(VI)/PMS system can be obtained than that in alone persulfate (PS), Fe(VI), PMS, or the Fe(VI)/PS process at pH 6.0. DCF was efficiently removed in Fe(VI)/PMS process within a wide range of pH values from 4.0 to 8.0, with higher degradation efficiency in acidic conditions. The increasing reaction temperature (10 to 30 ℃), Fe(VI) dose (6.25 to 100 µM), or PMS concentration (50 to 1000 µM) significantly enhanced the DCF degradation. The existences of HCO₃¯, Cl¯, and humic acid (HA) obviously inhibited the DCF removal. Electron paramagnetic resonance (EPR), free radical quenching, and probing experiments confirmed the existence of sulfate radicals (SO₄^•¯), hydroxyl radicals (^•OH), and Fe(V)/ Fe(IV), which are responsible for DCF degradation in Fe(VI)/PMS system. The variations of TOC removal ratio reveal that the adsorption of organics with ferric particles, formed in the reduction of Fe(VI), also were functioned in the removal process. Sixteen DCF transformation byproducts were identified by UPLC-QTOF/MS, and the toxicity variation was evaluated. Consequently, eight reaction pathways for DCF degradation were proposed. This study provides theoretical basis for the utilization of Fe(VI)/PMS process.

Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway

Recently, ClO2-based oxidation has attracted increasing attention to micropollutant abatement, due to high oxidation potential, low disinfection byproduct (DBPs) formation, and easy technical implementation. However, the kinetics, reactive sites, activation methods, and degradation pathways involved are not fully understood. Therefore, we reviewed current literature on ClO2-based oxidation in micropollutant abatement. In direct ClO2 oxidation, the reactions of micropollutants with ClO2 followed second-order reaction kinetics (kapp = 10−3–106 M−1 s−1 at neutral pH). The kapp depends significantly on the molecular structures of the micropollutant and solution pH. The reactive sites of micropollutants start with certain functional groups with the highest electron densities including piperazine, sulfonyl amido, amino, aniline, pyrazolone, phenol groups, urea group, etc. The one-electron transfer was the dominant micropollutant degradation pathway, followed by indirect oxidation by superoxide anion radical (O2•−) or hydroxyl radical (•OH). In UV-activated ClO2 oxidation, the reactions of micropollutants followed the pseudo-first-order reaction kinetics with the rates of 1.3 × 10−4–12.9 s−1 at pH 7.0. Their degradation pathways include direct ClO2 oxidation, direct UV photolysis, ozonation, •OH-involved reaction, and reactive chlorine species (RCS)-involved reaction. Finally, we identified the research gaps and provided recommendations for further research. Therefore, this review gives a critical evaluation of ClO2-based oxidation in micropollutant abatement, and provides recommendations for further research.

Evaluating the effect of diclofenac on hydrogen production by anaerobic fermentation of waste activated sludge

Hydrogen production from waste-activated sludge (WAS) anaerobic fermentation is considered to be an effective method of resource recovery. However, the presence of a large number of complex organic compounds in sludge will affect the biological hydrogen production process. As an extensively applied prevalent anti-inflammatory drug, diclofenac (DCF) is inevitably released into the environment. However, the effect of diclofenac on hydrogen production from WAS anaerobic fermentation has not been fully investigated. This work therefore aims to comprehensively investigate the removal efficiency of DCF in mesophilic anaerobic fermentation of WAS and its effect on hydrogen yield. Experiment results showed that 32.5%-38.3% of DCF was degraded in the fermentation process when DCF concentration was ranged from 6 to 100 mg/kg TSS (total suspended solids). DCF at environmental level inhibited hydrogen production, the maximal hydrogen yield decreased from 24.2 to 15.3 mL/g VSS (volatile suspended solids) with an increase of DCF addition from 6 to 100 mg/kg TSS. This is because the presence of DCF caused inhibitions to acetogenesis and acidogenesis, the processes responsible for hydrogen production, probably due to that the polar groups of DCF (i.e., carboxyl group) could readily bind to active sites of [FeFe]- Hydrogenase. Besides, the microbial analysis revealed that DCF increased the microbial diversity but had few influences on the microbial structure.

New 19F NMR methodology reveals structures of molecules in complex mixtures of fluorinated compounds

Although the number of natural fluorinated compounds is very small, fluorinated pharmaceuticals and agrochemicals are numerous. ¹⁹F NMR spectroscopy has a great potential for the structure elucidation of fluorinated organic molecules, starting with their production by chemical or chemoenzymatic reactions, through monitoring their structural integrity, to their biotic and abiotic transformation and ultimate degradation in the environment. Additionally, choosing to incorporate ¹⁹F into any organic molecule opens a convenient route to study reaction mechanisms and kinetics. Addressing limitations of the existing ¹⁹F NMR techniques, we have developed methodology that uses ¹⁹F as a powerful spectroscopic spy to study mixtures of fluorinated molecules. The proposed ¹⁹F-centred NMR analysis utilises the substantial resolution and sensitivity of ¹⁹F to obtain a large number of NMR parameters, which enable structure determination of fluorinated compounds without the need for their separation or the use of standards. Here we illustrate the ¹⁹F-centred structure determination process and demonstrate its power by successfully elucidating the structures of chloramination disinfectant by-products of a single mono-fluorinated phenolic compound, which would have been impossible otherwise. This novel NMR approach for the structure elucidation of molecules in complex mixtures represents a major contribution towards the analysis of chemical and biological processes involving fluorinated compounds.

¹⁹F-centred NMR structure determination protocol alleviates the need for compound separation. Disinfection byproducts of chloramination were unraveled by analyzing the reaction pathways of a single fluorinated molecule.

Characteristics and transformation pathways of venlafaxine degradation during disinfection processes using free chlorine and chlorine dioxide

Venlafaxine, a representative antidepressant, has been detected frequently in aquatic environments. The treatment of venlafaxine by free chlorine (NaOCl) and chlorine dioxide (ClO₂) was investigated in this study. The effects of operational variables and the water matrix on venlafaxine degradation were evaluated. The transformation pathways of venlafaxine were also studied. The results indicated that venlafaxine was removed efficiently during disinfection processes, especially when reacted with ClO₂. A higher dosage of disinfectant and mildly alkaline conditions (pH 9) enhanced the degradation of venlafaxine. The reactions were impacted when the tests were conducted in real water matrices, especially in secondary effluent. The presence of chloride and low concentrations of fulvic acid enhanced venlafaxine decomposition. The presence of Br^- also accelerated the reaction between venlafaxine and NaOCl. However, NO₂^- inhibited venlafaxine removal in both disinfection processes. Six intermediates were identified during venlafaxine degradation by ultrahigh-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry, and the main reactions included dehydration and demethylation.

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water: Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics (FQs) in synthetic marine aquaculture water were subject to sodium hypochlorite (NaClO) disinfection scenario to investigate their reaction kinetics and transformation during chlorination. Reactivity of each FQ to NaClO was following the order of ofloxacin (OFL) > enrofloxacin (ENR) > lomefloxacin (LOM) > ciprofloxacin (CIP) ~ norfloxacin (NOR) >> pipemedic acid (PIP), while flumequine did not exhibit reactivity. The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO, while humic acid was inhibitable to their degradation. The bromide ions promoted degradation of CIP and LOM, but restrained oxidation of OFL and ENR. By analysis of liquid chromatography with tandem mass spectrometry (LC-MS/MS), eight kinds of emerging brominated disinfection byproducts (Br-DBPs) caused by FQ_S were primarily identified in the chlorinated synthetic marine culture water. Through density functional theory calculation, the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms. Their formation involved decarboxylation, ring-opening/closure, dealkylation and halogenation. Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position. The piperazine ring containing tertiary amine was comparatively stable, while this moiety with a secondary amine structure would break down during chlorination. Additionally, logK_ow and logBAF of transformation products were calculated by EPI-Suite^TM to analyze their bioaccumulation. The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.

Electrochemical oxidation of diclofenac on CNT and M/CNT modified electrodes

Successful electrochemical oxidation of diclofenac, a non-steroidal anti-inflammatory drug considered as an emerging pollutant, was investigated on CNT, Pt/CNT and Ru/CNT modified electrodes based on Carbon Toray in aqueous media.

Detection, transformation, and toxicity of indole-derivative nonsteroidal anti-inflammatory drugs during chlorine disinfection

As important emerging contaminants, nonsteroidal anti-inflammatory drugs (NSAIDs) are the most intensively prescribed pharmaceuticals introduced to drinking water due to their incomplete removal in wastewater treatment. While concentrations of NSAIDs in drinking water are generally low, they have been attracting increasing concern as a result of their disinfection byproducts (DBPs) generated in drinking water disinfection. In this work, detection methods were set up for four representative indole-derivative NSAIDs (indomethacin, acemetacin, sulindac, and etodolac) using ultra performance liquid chromatography/electrospray ionization-triple quadruple mass spectrometry (UPLC/ESI-tqMS). ESI+ was better for detection of indomethacin and sulindac, whereas ESI- was suitable to detection of acemetacin and etodolac. With optimized MS parameters, the instrument detection and quantitation limits of the four indole derivatives were achieved to be 1.1-24.6 ng/L and 3.7-41.0 ng/L, respectively. During chlorination, indomethacin and acemetacin could undergo five major reaction types (chlorine substitution, hydrolysis, decarboxylation, C-C coupling, and C-N cleavage) to form a series of DBPs, among which 19 were proposed/identified with structures. Based on the revealed structures of DBPs, transformation pathways of indomethacin and acemetacin in chlorination were partially elucidated. Notably, individual and mixture toxicity of indomethacin and acemetacin before/after chlorination were evaluated using a well-established acute toxicity assessment and a Hep G2 cell cytotoxicity assay, respectively. Results showed that the predicted acute toxicity of a few chlorination DBPs were higher than their precursors; chlorination substantially enhanced the mixture cytotoxicity of indomethacin by over 10 times and slightly increased the mixture cytotoxicity of acemetacin.

Novel franklinite-like synthetic zinc-ferrite redox nanomaterial: synthesis, and evaluation for degradation of diclofenac in water

The current study investigates a novel redox technology based on synthetic franklinite-like zinc-ferrite nanomaterial with magnetic properties and redox nature for potential use in water treatment. Physicochemical characterization revealed the nanoscale size and AB2O4 spinel configuration of the zinc-ferrite nanomaterial. The redox activity of nanoparticles was tested for degradation of diclofenac (DCF) pharmaceutical in water, without any added external oxidants and under dark experimental conditions. Results revealed ~90% degradation in DCF (10 μM) within 2 min of reaction using 0.17 g/L Zn1.0Fe2.0O4. Degradation of DCF was due to chemical reduction by surface electrons on zinc-ferrite and oxidation by oxygen-based radicals. Three byproducts from reduction route and eight from oxidation pathways were identified in the reaction system. Reaction pathways were suggested based on the identified byproducts. Results demonstrated the magnetic zinc-ferrite is a standalone technology that has a great promise for rapid degradation of organic contaminants, such as DCF in water.

Novel Disinfection Byproducts Formed from the Pharmaceutical Gemfibrozil Are Bioaccumulative and Elicit Increased Toxicity Relative to the Parent Compound in Marine Polychaetes (Neanthes arenaceodentata)

Formation of halogenated disinfection byproducts (DBPs) from pharmaceutically active compounds has been observed in water supply systems following wastewater chlorination. Although research has been limited thus far, several studies have shown that halogenated DBPs may elicit increased toxicity compared to their parent compounds. For example, the lipid regulator gemfibrozil has been shown to form chlorogemfibrozil (Cl-gemfibrozil) and bromogemfibrozil (Br-gemfibrozil) following chlorination, which are more potent antiandrogens in male Japanese medaka (Oryzias latipes) compared to their parent compounds. In the present study, we aimed to characterize the bioaccumulative ability of halogenated gemfibrozil DBPs in marine polychaetes via chronic sediment exposures and, consequently, to assess the chronic and acute toxicity of halogenated gemfibrozil DBPs through sediment (in vivo) and aqueous (in vivo and in silico) toxicity evaluations. Following 28 day sediment exposures, Cl-gemfibrozil and Br-gemfibrozil bioaccumulated within Neanthes arenaceodentata, with both compounds reducing survival and growth. The biota-sediment accumulation factors determined for Cl-gemfibrozil and Br-gemfibrozil were 2.59 and 6.86, respectively. Furthermore, aqueous 96 h toxicity tests with N. arenaceodentata indicated that gemfibrozil DBPs elicited increased toxicity compared to the parent compound. While gemfibrozil had an acute LC50 value of 469.85 ± 0.096 mg/L, Cl-gemfibrozil and Br-gemfibrozil had LC50 values of 12.34 ± 0.085 and 9.54 ± 0.086 mg/L, respectively. Although acute toxicity is relatively low, our results indicate that halogenated gemfibrozil DBPs are bioaccumulative and may elicit effects in apex food web organisms prone to accumulation following lifelong exposures.

Use of α-cyclodextrin to Promote Clean and Environmentally Friendly Disinfection of Phenolic Substrates via Chlorine Dioxide Treatment

The use of chlorine dioxide to disinfect drinking water and ameliorate toxic components of wastewater has significant advantages in terms of providing safe water. Nonetheless, significant drawbacks toward such usage remain. These drawbacks include the fact that toxic byproducts of the disinfection agents are often formed, and the complete removal of such agents can be challenging. Reported herein is one approach to solving this problem: the use of α-cyclodextrin to affect the product distribution in chlorine dioxide-mediated decomposition of organic pollutants. The presence of α-cyclodextrin leads to markedly more oxidation and less aromatic chlorination, in a manner that is highly dependent on analyte structure and other reaction conditions. Mechanistic hypotheses are advanced to explain the cyclodextrin effect, and the potential for use of α-cyclodextrin for practical wastewater treatment is also discussed.

Evaluation of azamethiphos and dimethoate degradation using chlorine dioxide during water treatment

Chlorine dioxide (ClO₂) degradation of the organophosphorus pesticides azamethiphos (AZA) and dimethoate (DM) (10 mg/L) in deionized water and in Sava River water was investigated for the first time. Pesticide degradation was studied in terms of ClO₂ level (5 and 10 mg/L), degradation duration (0.5, 1, 2, 3, 6, and 24 h), pH (3.00, 7.00, and 9.00), and under light/dark conditions in deionized water. Degradation was monitored using high-performance liquid chromatography. Gas chromatography coupled with triple quadrupole mass detector was used to identify degradation products of pesticides. Total organic carbon was measured to determine the extent of mineralization after pesticide degradation. Real river water was used under recommended conditions to study the influence of organic matter on pesticide degradation. High degradation efficiency (88-100% for AZA and 85-98% for DM) was achieved in deionized water under various conditions, proving the flexibility of ClO₂ degradation for the examined organophosphorus pesticides. In Sava River water, however, extended treatment duration achieved lower degradation efficiency, so ClO₂ oxidized both the pesticides and dissolved organic matter in parallel. After degradation, AZA produced four identified products (6-chlorooxazolo[4,5-b]pyridin-2(3H)-one; O,O,S-trimethyl phosphorothioate; 6-chloro-3-(hydroxymethyl)oxazolo[4,5-b]pyridin-2(3H)-one; O,O-dimethyl S-hydrogen phosphorothioate) and DM produced three (O,O-dimethyl S-(2-(methylamino)-2-oxoethyl) phosphorothioate; e.g., omethoate; S-(2-(methylamino)-2-oxoethyl) O,O-dihydrogen phosphorothioate; O,O,S-trimethyl phosphorodithioate). Simple pesticide degradation mechanisms were deduced. Daphnia magna toxicity tests showed degradation products were less toxic than parent compounds. These results contribute to our understanding of the multiple influences that organophosphorus pesticides and their degradation products have on environmental ecosystems and to improving pesticide removal processes from water.

Degradation of Diclofenac in Water Using the O3/UV/S2O8 Advanced Oxidation Process

: Diclofenac (DCF) is among the compounds that are highly resistant to biological degradation processes and have low removal efficiency in wastewater treatment plants. In the current study, DCF removal was examined by using the O3/UV/S2O8 process. All experiments were carried out in a 2-liter lab-scale semi-continuous reactor. DCF concentration was measured by HPLC analytical method. The study began with the optimization of pH, and the effects of other operating parameters, including pH, ozone concentrations, drug, persulfate, and natural organic matter (Humic acid) on the degradation were investigated. The mineralization of diclofenac was also investigated. The results showed the removal efficiency of 89% and a persulfate concentration of 200 mg/L, pH = 6, DCF = 8 mg/L, and reaction periods 30 min in the O3/UV/S2O8 process. Humic acid was selected as a scavenging compound, which decreased the removal DCF rate from 89% to 76%. So, sulfate radical-based technologies show promising results for the removal of these particular pharmaceuticals from the wastewater treatment plant.

Enhanced degradation of diclofenac with Ru/Fe modified anode microbial fuel cell: Kinetics, pathways and mechanisms

A microbial fuel cell (MFC) was constructed with a Ru/Fe-modified-anode prepared by reduction and coating for enhancing diclofenac (DCF) degradation. Results showed that Ru⁰ and Fe⁰ were dispersed uniformly on Ru/Fe-modified-electrode surface, and Ru/Fe existed as an alloy structure. Due to catalysis of Ru/Fe, both electrochemical activity and DCF-degradation performance of Ru/Fe-modified-anode-MFC (Ru/Fe-MFC) were enhanced compared to carbon-felt-anode-MFC (CF-MFC). The maximum power density of Ru/Fe-MFC reached 0.600 W m^-2, and DCF-degradation in Ru/Fe-MFC followed the pseudo-first-order-kinetic model with k_obs of 0.711 d^-1 which was 1.08, 1.34 and 2.21 times higher than that of Ru-modified-anode-MFC (Ru-MFC), Fe-modified-andoe-MFC (Fe-MFC) and CF-MFC, respectively. Results also showed that DCF-degradation and power generation would compete for electrons in Ru/Fe-MFC. Ru/Fe-modified-anode accelerated the enrichment of electro-active bacteria and DCF-degrading bacteria such as Geobacter, Clostridium, Sedimentibacter, Pseudomonas and Desulfovibrionaceae. Stepwise dechlornation occurred for DCF-degradation mainly due to synergistic reaction of Ru/Fe and DCF-degrading bacteria within Ru/Fe-MFC.

Degradation behaviors of Isopropylphenazone and Aminopyrine and their genetic toxicity variations during UV/chloramine treatment

Combination of ultraviolet and chloramine (i.e., UV/chloramine) treatment has been attracting increasingly attention in recent years due to its high efficiency in removing trace organic contaminants. This study investigated the degradation behaviors of two pyrazolone pharmaceuticals (i.e., Isopropyl phenazone (PRP) and Aminopyrine (AMP)) and their genetic toxicity variations during UV/chloramine treatment. The results showed that chloramine could hardly degrade PRP and AMP, while UV/chloramine greatly increased the observed first-order rate constant (k_obs) of PRP and AMP degradation. The quenching and probe experiments illustrated that the reactive chlorine species (RCS) contributed dominantly to PRP removal, and hydroxyl radical (HO^•) was the major contributor to the degradation of AMP, while the reactive amine radicals (RNS) could hardly degrade them. The overall degradation rates of PRP and AMP decreased as pH increased from 6.5 to 10. The k_obs of PRP and AMP increased along with NH₂Cl dosage increasing and reached a plateau at higher concentrations (0.2-0.5 mM). The present background carbonate (HCO₃^-, 1-10 mM), chloride (Cl^-, 1-10 mM) and natural organic matter (NOM, 5-10 mg-C L^-1) exhibited inhibition impacts on PRP and AMP degradation. In addition, the intermediates/products of PRP and AMP were identified and their general degradation pathways were proposed to be hydroxylation, deacetylation, and dephenylization. Specifically, Cl-substitution was inferred during PRP degradation, while demethylation in tertiary amine group was only observed in AMP degradation. These mechanisms including the main reactive sites of PRP and AMP were further confirmed by the frontier orbitals calculation. Moreover, the results of the genetic toxicity according to the micronucleus test of Viciafaba root tip indicated that UV/chloramine treatment could partially reduce the genetic toxicity of PRP and AMP.

Formation of new disinfection by-products of priority substances (Directive 2013/39/UE and Watch List) in drinking water treatment

The degradation of priority substances (Directive 2013/39/UE and Watch List) by chlorine dioxide (ClO₂) and the formation of disinfection by-products (DBPs) in a drinking water treatment plant (DWTP) located near Barcelona (NE Spain) were investigated. For the first time, the reactivity with ClO₂ of several compounds frequently found at the entrance of the DWTP such as erythromycin, clarithromycin, chlorpyrifos, and imidacloprid was evaluated in both simulated and real conditions. To identify potential DBPs, experiments were performed at laboratory scale by simulating the operational disinfection conditions in the DWTP. Liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) working in full scan and target-MS/HRMS modes was used for the identification of the generated DBPs. Several new DBPs were found, three from erythromycin, one from clarithromycin, two from chlorpyrifos, and one from imidacloprid. Then, the presence and behavior through DWTP treatment of priority substances and their DBPs were investigated in order to evaluate their generation in real working conditions. Two of the potential DBPs, anhydroerythromycin, and N-desmethyl clarithromycin were already identified in the raw water of DWTP, but N-desmethyl clarithromycin was also generated after the chlorine dioxide treatment step. Both compounds were eliminated by the treatments applied in the DWTP; anhydroerythromycin was eliminated after ozonation in the upgraded conventional treatment and after reverse osmosis in the advanced treatment while N-desmethyl clarithromycin is recalcitrant in the upgraded conventional treatment, but it was eliminated by reverse osmosis.

Simultaneous aqueous chlorination of amine-containing pharmaceuticals

Amine-containing pharmaceuticals such as acetaminophen, diclofenac, and sulfamethoxazole are the most often detected pharmaceuticals in wastewater and other aquatic environments. Amine-containing pharmaceuticals can be effectively removed by chlorination. These drugs, however, may coexist in wastewater. Thus, they may compete with each other, and their chlorinated products may react with each other to form new products. In this study, competitive effects of the above three amine-containing pharmaceuticals by chlorination and their products were investigated. The priority of chlorination of these compounds was dependent upon the pH of the solution, due to the dissociation of the compounds and hypochlorite. It followed the order of sulfamethoxazole > diclofenac > acetaminophen in an acidic condition, the order of sulfamethoxazole > acetaminophen > diclofenac in a neutral condition, and the order of sulfamethoxazole ≈ acetaminophen > diclofenac in an alkaline condition. Some of the chlorinated products in single- and multiple-compound systems were the same. Dimers of sulfamethoxazole and its chlorinated products, however, were not found, but dimers of sulfamethoxazole and acetaminophen or diclofenac were found in multiple-compound systems. This finding is important because it means that new products may be produced if different amine-containing pharmaceuticals react with free chlorine simultaneously.

Diclofenac removal by pyrite-Fenton process: Performance in batch and fixed-bed continuous flow systems

This study provides experimental results from batch and column studies to investigate diclofenac degradation by pyrite-Fenton process under variable chemical conditions (e.g., pyrite loading). Batch experiments show that diclofenac removal increased with increasing hydrogen peroxide and pyrite concentration. On the other hand, the addition of organic chelating agents such as citrate had an adverse effect on diclofenac removal by pyrite-Fenton process in batch systems due to scavenging effect of these agents for hydroxyl radicals. Batch results showed a direct correlation between the rate of diclofenac degradation and the rate of iron dissolution from pyrite, suggesting that diclofenac removal by pyrite-Fenton process was mainly controlled by solution phase hydroxyl radical attack on aromatic structure. Column experiments show that the effluent diclofenac concentration initially reached a peak value, and then sharply decreased to zero at higher pore volumes. The initial diclofenac breakthrough coincided well with the highest Fe(II) concentration observed in the breakthrough curve, implying that the generation of excess Fe(II) had a detrimental effect on removal efficiency due to scavenging effect of excess Fe(II) for hydroxyl radicals. The column system continued to function with 100% diclofenac removal efficiency when the effluent Fe(II) concentration decreased to a level at which the scavenging effect was minimized.

Insights into the synergetic mechanism of a combined vis-RGO/TiO2/peroxodisulfate system for the degradation of PPCPs: Kinetics, environmental factors and products

In recent years, how to effectively remove emerging organic pollutants in water bodies has been studied extensively, especially in the actual complex water environment. In the present study, an effective wastewater treatment system that combined photocatalysis and an oxidizing agent was investigated. Specifically, visible-light driven reduced graphene oxide (RGO)/TiO₂ composites were prepared, and peroxodisulfate (PDS) was used as electron acceptor to accelerate the photocatalytic activity of this material. The vis-RGO/TiO₂/PDS system exhibited outstanding properties in the degradation of diclofenac (DCF), which was also facilitated by acidic conditions and Cl^-. Lake water, tap water, river water and HCO₃^- decreased the DCF degradation rate, while NO₃^- affected the system only slightly. Low concentrations of fulvic acid (FA) promoted the degradation of DCF via the generation of excited states, whereas a high concentration of FA inhibited the degradation, which was likely due to the light screening effect. The photocatalytic mechanism revealed that PDS served as an electron acceptor for the promotion of electron-hole pair separation and the generation of additional reactive oxygen species, while the RGO served as an electric conductor. The active substances, h⁺, OH, ¹O₂, SO₄^- and O₂^- were generated in this system, O₂^- and h⁺ played significant roles in the degradation of DCF based electron spin resonance tests and radical quenching results. According to the mass spectrometry results, the amide bond cleavage, dechlorination reaction, hydroxyl addition reaction, and decarboxylation reaction were the primary transformative pathways.

Fast degradation of diclofenac by catalytic hydrodechlorination

Aqueous-phase catalytic hydrodechlorination (HDC) has been scarcely explored in the literature for the removal of chlorinated micropollutants. The aim of this work is to prove the feasibility of this technology for the fast and environmentally-friendly degradation of such kind of compounds. Diclofenac (DCF), a highly consumed anti-inflammatory drug, has been selected as the target pollutant given its toxicity and low biodegradability. The commercial Pd/Al₂O₃ (1% wt.) catalyst has been used due to its prominent role on this field. Complete degradation of DCF was achieved in a short reaction time (20 min) under ambient conditions (25 °C, 1 atm) at [DCF]₀ = 68 μM; [Pd/Al₂O₃]₀ = 0.5 g L^-1 and H₂ flow rate of 50 N mL min^-1. Remarkably, the chlorinated intermediate (2-(2-chloroanilino)-phenylacetate (Cl-APA)) generated along reaction was completely removed at the same time, being the chlorine-free compound 2-anilinophenylacetate (APA) the only final product. A reaction scheme based on this consecutive pathway and a pseudo-first-order kinetic model have been proposed. An apparent activation energy of 43 kJ mol^-1 was obtained, a comparable value to those previously reported for conventional organochlorinated pollutants. Remarkably, the catalyst exhibited a reasonable stability upon three successive uses, achieving the complete degradation of the drug and obtaining APA as the final product in 30 min. The evolution of ecotoxicity was intimately related to the disappearance of the chlorinated organic compounds and thus, the final HDC effluents were non-toxic. The versatility of the system was finally demonstrated in different environmentally-relevant matrices (wastewater treatment plant effluent and surface water).

Removal of diclofenac from water by in/out PAC/UF hybrid process

Results from a lab-scale investigation of a hybrid in/out ultrafiltration and powdered activated carbon adsorption PAC/UF for removal of diclofenac (c₀= 5 mg/L) are presented. The efficiency of the process was compared for single pulse and continuous carbon dosing (PAC dose 5 mg/L) in dechlorinated tap water under fluxes of 87 and 135 L/(m² h). For higher flux conditions, it was observed that single pulse dosing has an advantage over continuous dosing procedure when comparing cycle average removal efficiency. Increase of carbon dose under these conditions increased cycle average removal only to a limited extent. PAC dose above 15 mg/L did not give improvements of the removal. Hypothesis was made that non-effective carbon distribution might be the possible reason.

Determination of nine pharmaceutical active compounds in surface waters from Paraopeba River Basin in Brazil by LTPE-HPLC-ESI-MS/MS

A simple, inexpensive, versatile, and environment-friendly extraction method, using low-temperature partitioning extraction (LTPE), was validated to quantify pharmaceutical-active compounds (PhACs) in surface water samples by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The PhACs analyzed were acetaminophen, bezafibrate, diclofenac, diltiazem, fluconazole, linezolid, miconazole, ondansetron hydrochloride, and trimethoprim. The detection and quantification limits ranged from 0.15 to 12.30 ng L^-1 and 0.43 to 40.60 ng L^-1, respectively. Recovery rates ranged from 46 to 135%, and relative standard deviation (RSD%) varied between 0.49 and 6.13%. This method was applied to monitor water contamination by PhACs in the Paraopeba River Basin (PRB), Minas Gerais state, Brazil. All PhACs, except linezolid which was not detected, were found in PRB water samples in concentrations that ranged from 2.6 ng L^-1 to 2.62 μg L^-1.

Photodegradation kinetics, transformation, and toxicity prediction of ketoprofen, carprofen, and diclofenac acid in aqueous solutions

Photodegradation of 3 commonly used nonsteroidal anti-inflammatory drugs, ketoprofen, carprofen, and diclofenac acid, was conducted under ultraviolet (UV) irradiation. The kinetic results showed that the 3 pharmaceuticals obeyed the first-order reaction with decreasing rate constants of 1.54 × 10^-4 , 5.91 × 10^-5 , and 7.78 × 10^-6  s^-1 for carprofen, ketoprofen, and diclofenac acid, respectively. Moreover, the main transformation products were identified by ion-pair liquid-liquid extraction combined with injection port derivatization-gas chromatography-mass spectrometry and high-performance liquid chromatography-quadrupole-time of flight mass spectrometric analysis. There were 8, 3, and 6 transformation products identified for ketoprofen, carprofen, and diclofenac acid, respectively. Decarboxylation, dechlorination, oxidation, demethylation, esterification, and cyclization were proposed to be associated with the transformation of the 3 pharmaceuticals. Toxicity prediction of the transformation products was conducted on the EPI Suite software based on ECOSAR model, and the results indicate that some of the transformation products were more toxic than the parent compounds. The present study provides the foundation to understand the transformation behavior of the studied pharmaceuticals under UV irradiation. Environ Toxicol Chem 2017;36:3232-3239. © 2017 SETAC.

Mass spectrometry based in vitro assay investigations on the transformation of pharmaceutical compounds by oxidative enzymes

The ubiquitous presence of trace organic chemicals in wastewater and surface water leads to a growing demand for novel removal technologies. The use of isolated enzymes has been shown to possess the capability for a targeted application but requires a clearer mechanistic understanding. In this study, the potential of peroxidase from horseradish (HRP) and laccase from Pleurotus ostreatus (LccPO) to transform selected trace organic chemicals was studied using mass spectrometry (MS)-based in vitro enzyme assays. Conversion by HRP appeared to be more efficient compared to LccPO. Diclofenac (DCF) and sotalol (STL) were completely transformed by HRP after 4 h and immediate conversion was observed for acetaminophen (APAP). During treatment with LccPO, 60% of DCF was still detectable after 24 h and no conversion was found for STL. APAP was completely transformed after 20 min. Sulfamethoxazole (SMX), carbamazepine (CBZ), ibuprofen (IBP) and naproxen (NAP) were insusceptible to enzymatic conversion. In pharmaceutical mixtures, HRP exhibited a preference for DCF and APAP and the generally less efficient conversion of STL was enhanced in presence of APAP. Transformation product pattern after treatment with HRP revealed polymerization products for DCF while STL showed cleavage reactions. DCF product formation shifted towards a proposed dimeric iminoquinone product in presence of APAP whereas a generally less pronounced product formation in mixtures was observed for STL. In conclusion, the enzymatic treatment approach worked selectively and efficiently for a few pharmaceuticals. However, for application the investigation and possibly immobilization of multiplex enzymes being able to transform diverse chemical structures is recommended.

Photodegradation of diclofenac in aqueous solution by simulated sunlight irradiation: kinetics, thermodynamics and pathways

Diclofenac (DCF) is one of the most frequently detected pharmaceuticals in various water samples. This paper studied the effects of aquatic environmental factors (pH, temperature and dissolved organic matter) on photodegradation of DCF under simulated sunlight. The results demonstrate that degradation pathways proceed via pseudo first-order kinetics in all cases and the photodegradation of DCF by simulated sunlight. Thermodynamic study indicated that the photodegradation course is spontaneous, exothermic and irreversible. The rate constant gradually increased when the pH increased from 3 to 5, then decreased when the pH increased from 5 to 8, and finally increased when the pH further increased from 8 to 12. Humic acid inhibited the photodegradation of DCF. Three kinds of main degradation products were observed by high performance liquid chromatography/mass spectrometry and the degradation pathways were suggested. A toxicity test using Photobacterium phosphoreum T₃ Sp indicated the generation of some more toxic products than DCF.

Aqueous chlorination of fenamic acids: Kinetic study, transformation products identification and toxicity prediction

Fenamic acids, one important type of non-steroidal anti-inflammatory drugs, are ubiquitous in environmental matrices. Thus it is of high significance to know the fate of them during chlorination disinfection considering their potential toxicity to the environment and humans. In the present study, the chlorination kinetics of three fenamic acids, i.e. mefenamic acid (MEF), tolfenamic acid (TOL) and clofenamic acid (CLO), were examined at different pHs, which followed second-order reaction under studied conditions. The studied fenamic acids degraded fast, with the largest apparent second-order rate coefficient (k_app) values of 446.7 M^-1 s^-1 (pH 7), 393.3 M^-1 s^-1 (pH 8) and 360.0 M^-1 s^-1 (pH 6) for MEF, TOL and CLO, respectively. The transformation products (TPs) were identified by solid-phase extraction-liquid chromatography-mass spectrometer and ion-pair liquid-liquid extraction and injection port derivatization-gas chromatography-mass spectrometer. Despite different numbers of TPs were detected for each studied fenamic acid through these two analytical methods, the types of TPs were almost the same; chlorine substitution, oxidation and the joint oxidation with chlorine substitution are transformation reactions involved in chlorination. Moreover, the total toxicity of the TPs was assayed based on luminescent bacteria. Under different pHs, the different types of TPs might form, resulting in the varied total toxicity. The toxicity of all three fenamic acids chlorinated at pH of 8 was greater than those at pHs of 6 and 7. This study provided the information about the kinetics, transformation and toxicity of three fenamic acids during water chlorination, which is important to the drinking water safety.

Oxidation of indometacin by ferrate (VI): kinetics, degradation pathways, and toxicity assessment

The oxidation of indometacin (IDM) by ferrate(VI) (Fe(VI)) was investigated to determine the reaction kinetics, transformation products, and changes in toxicity. The reaction between IDM and Fe(VI) followed first-order kinetics with respect to each reactant. The apparent second-order rate constants (k _app) decreased from 9.35 to 6.52 M^-1 s^-1, as the pH of the solution increased from 7.0 to 10.0. The pH dependence of k _app might be well explained by considering the species-specific rate constants of the reactions of IDM with Fe(VI). Detailed product studies using liquid chromatography-tandem mass spectrometry (LC-MS/MS) indicated that the oxidation products were primarily derived from the hydrolysis of amide linkages, the addition of hydroxyl groups, and electrophilic oxidation. The toxicity of the oxidation products was evaluated using the Microtox test, which indicated that transformation products exhibited less toxicity to the Vibrio fischeri bacteria. Quantitative structure-activity relationship (QSAR) analysis calculated by the ecological structure activity relationship (ECOSAR) revealed that all of the identified products exhibited lower acute and chronic toxicity than the parent pharmaceutical for fish, daphnid, and green algae. Furthermore, Fe(VI) was effective in the degradation IDM in water containing carbonate ions or fulvic acid (FA), and in lake water samples; however, higher Fe(VI) dosages would be required to completely remove IDM in lake water in contrast to deionized water.

Fate and behaviour of diclofenac during hydrothermal carbonization

Hydrothermal carbonization (HTC) has become an esteemed method to convert sewage sludge into biochar. Besides dewatering and disinfection the process is suggested to reduce the micropollutant load, which would be beneficial for the use of biochar as fertilizer. This study was designed to examine reduction of micropollutants and formation of transformation products during HTC using the example of diclofenac. We investigated compounds' removal at HTC conditions in inert experiments and in real samples. Results showed that HTC temperature (>190 °C) and pressure (∼15 bar) have the potential to fully degrade diclofenac in inert experiments and spiked sewage sludge (>99%) within 1 h. However, interfering effects hinder full removal in native samples resulting in 44% remaining diclofenac. Additionally, a combination of suspected-target and non-target analysis using LC-MS/MS and LC-HRMS resulted in the determination of six transformation products. These products have been reported in biochar from HTC for the first time, although other studies described them for other processes like advanced oxidation. Based on the detected transformation products, we proposed a degradation mechanism reflecting HTC reactions such as dehydroxylation and decarboxylation.

Transformation of tamoxifen and its major metabolites during water chlorination: Identification and in silico toxicity assessment of their disinfection byproducts

The selective estrogen receptor modulator tamoxifen is the most commonly used drug for the treatment and prevention of breast cancer. Tamoxifen is considered as a pro-drug since it is known to exert its pharmacological effect through its major active metabolites, 4-hydroxy-tamoxifen and 4-hydroxy-N-desmethyl-tamoxifen, which are mainly excreted in the urine in the days following administration. In the present work, the reactivity of tamoxifen and its major active metabolites in free chlorine-containing water was investigated for the first time. Under the studied chlorination conditions, tamoxifen was fairly stable whereas its metabolites were quickly degraded. A total of thirteen chlorinated byproducts were tentatively identified by ultra-high performance liquid chromatography coupled to high-resolution hybrid quadrupole-Orbitrap tandem mass spectrometry. Time-course profiles of the identified byproducts were followed in real wastewater samples under conditions that simulate wastewater disinfection. A preliminary assessment of their acute aquatic toxicity at two trophic levels by means of quantitative structure-activity relationship models showed that the identified byproducts were up to 110-fold more toxic than the parent compounds.

Oxidation of diclofenac with chlorine dioxide in aquatic environments: influences of different nitrogenous species

The oxidation of diclofenac (DCF), a non-steroidal anti-inflammatory drug and emerging water pollutant, with chlorine dioxide was investigated under simulated water disinfection conditions. The reaction kinetics as functions of the initial concentrations of DCF, different nitrogenous species, and different pE values were experimentally determined. The results demonstrated that DCF reacted rapidly with ClO2, where more than 75 % of DCF (≤3.00 μM) was removed by 18.94 μM ClO2 within 60 s. All of the reactions followed pseudo first-order kinetics with respect to DCF, and the rate constant, k obs, exhibited a significant decrease from 4.21 × 10(-2) to 8.09 × 10(-3) s(-1), as the initial DCF concentration was increased from 1.00 to 5.00 μM. Furthermore, the degradation kinetics of DCF was clearly dependent on nitrogen-containing ion concentrations in the reaction solution. Ammonium and nitrite ions inhibited the DCF degradation by ClO2, whereas nitrate ion clearly initiated its promotion. In contrast, the inhibitory effect of NO2 (-) was more robust than that of NH4 (+). When the values of pE were gradually increased, the transformation of NH4 (+) to NO2 (-), and subsequently to NO3 (-), would occur, the rate constants were initially decreased, and then increased. When NH4 (+) and NO2 (-) coexisted, the inhibitory effect on the DCF degradation was less than the sum of the partial inhibitory effect. However, when NO2 (-) and NO3 (-) coexisted, the actual inhibition rate was greater than the theoretical estimate. These results indicated that the interaction of NH4 (+) and NO2 (-) was antagonistic, while the coexistence of NO2 (-) and NO3 (-) was observed to have a synergistic effect in aqueous environments.

Modified phyto-waste Terminalia catappa fruit shells: a reusable adsorbent for the removal of micropollutant diclofenac

A novel reusable adsorbent was prepared and investigated for the removal of diclofenac from aqueous systems.

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.

Seasonal variation of diclofenac concentration and its relation with wastewater characteristics at two municipal wastewater treatment plants in Turkey

The pharmaceutically active compound diclofenac has been monitored during one year at separate treatment units of two municipal wastewater treatment plants (WWTPs) to evaluate its seasonal variation and the removal efficiency. Conventional wastewater characterization was also performed to assess the possible relationship between conventional parameters and diclofenac. Diclofenac concentrations in the influent and effluent of both WWTPs were detected in the range of 295-1376 and 119-1012ng/L, respectively. Results indicated that the higher diclofenac removal efficiency was observed in summer season in both WWTPs. Although a consistency in diclofenac removal was observed in WWTP_1, significant fluctuation was observed at WWTP_2 based on seasonal evaluation. The main removal mechanism of diclofenac in the WWTPs was most often biological (55%), followed by UV disinfection (27%). When diclofenac removal was evaluated in terms of the treatment units in WWTPs, a significant increase was achieved at the treatment plant including UV disinfection unit. Based on the statistical analysis, higher correlation was observed between diclofenac and suspended solids concentrations among conventional parameters in the influent whereas the removal of diclofenac was highly correlated with nitrogen removal efficiency.