Main Transformation Products Research Articles

Investigation of sulfoxaflor, flupyradifurone and their transformation products in plant-based food matrices

Sulfoxaflor and flupyradifurone, two pesticides belonging to sulfoximins and butenolides, are widely used to treat crops and fruits. In order to amplify the detection of pollutants, we aimed to identify also molecules deriving from the parent pesticides. We studied their photoinduced transformation and identified their main transformation products by applying a laboratory simulation and by employing HPLC-HRMS to characterize them. We detected three transformation products from sulfoxaflor, whose formation involved the conversion of cyanamide group into a ureic group and the detachment of the side chain. Flupyradifurone transformation proceeded through the formation of seven transformation products and three of them were recognized in this study for the first time; it involved hydroxylation and breakage of the molecule with the detachment of the pyridine or furan ring. These results will allow enlarging the extent of TPs to be screened in food matrices.

Solar Light Photoactive Floating Polyaniline/TiO2 Composites for Water Remediation.

In the present study, the development of innovative polyurethane-polyaniline/TiO2 modified floating materials applied in the sorption and photodegradation of rhodamine B from water matrix under solar light irradiation is reported. All the materials were fabricated with inexpensive and easy approaches and were properly characterized. The effect of the kind of polyaniline (PANI) dopant on the materials’ behavior was investigated, as well as the role of the conducting polymer in the pollutant abatement on the basis of its physico-chemical characteristics. Rhodamine B is removed by adsorption and/or photodegradation processes depending on the type of doping agent used for PANI protonation. The best materials were subjected to recycle tests in order to demonstrate their stability under the reaction conditions. The main transformation products formed during the photodegradation process were identified by ultraperformance liquid chromatography-mass spectrometry (UPLC/MS). The results demonstrated that photoactive floating PANI/TiO2 composites are useful alternatives to common powder photocatalysts for the degradation of cationic dyes.

Microbial Transformation of Chlordecone and Two Transformation Products Formed During in situ Chemical Reduction.

Chlordecone (CLD) is a very persistent synthetic organochlorine pesticide found in the French West Indies. Recently published work has demonstrated the potential of zero-valent iron to dechlorinate CLD by in situ chemical reduction (ISCR) in soils under water-saturated conditions, forming mono- to penta-dechlorinated CLD transformation products. These transformation products are more mobile than CLD and less toxic; however, nothing is known about their further degradation, although increasing evidence of CLD biodegradation by bacteria is being found. The present study began with the enrichment from wastewater sludge of a CLD-transforming community which was then inoculated into fresh media in the presence of either CLD or two of the main ISCR transformation products, 10-monohydroCLD (-1Cl-CLD) and tri-hydroCLD (-3Cl-CLD). Carried out in triplicate batches and incubated at 38°C under anoxic conditions and in the dark, the cultures were sampled regularly during 3 months and analyzed for CLD, -1Cl-CLD, -3Cl-CLD, and possible transformation products by gas chromatography coupled to mass spectrometry. All batches showed a decrease in the amended substrates (CLD or hydroCLD). CLD degradation occurred with concomitant formation of a nine-carbon compound (pentachloroindene) and two sulfur-containing transformation products (chlordecthiol, CLD-SH; methyl chlordecsulfide, CLD-SCH3), demonstrating competing transformation pathways. In contrast, -1Cl-CLD and -3Cl-CLD only underwent a sequential reductive sulfidation/S-methylation process resulting in -1Cl-CLD-SH and -1Cl-CLD-SCH3 on the one hand, and -3Cl-CLD-SH, -3Cl-CLD-SCH3 on the other hand. Some sulfur-containing transformation products have been reported previously with single bacterial strains, but never in the presence of a complex microbial community. At the end of the experiment, bacterial and archaeal populations were investigated by 16S rRNA gene amplicon sequencing. The observed diversity was mostly similar in the CLD and -1Cl-CLD conditions to the inoculum with a dominant archaea genus, Methanobacterium, and four OTU affiliated to bacteria, identified at the family (Spirochaetaceae) or genus level (Desulfovibrio, Aminobacterium, and Soehngenia). On the other hand, in the -3Cl-CLD condition, although the same OTU were found, Clostridium sensu stricto 7, Candidatus Cloacimonas, and Proteiniphilum were also present at > 2% sequences. Presence of methanogens and sulfate-reducing bacteria could contribute to sulfidation and S-methylation biotransformations. Overall, these results contribute to increasing our knowledge on the biodegradability of CLD and its transformation products, helping to progress toward effective remediation solutions.

Elimination of Diethylenetriaminepentaacetic Acid from Effluents from Pharmaceutical Production by Ozonation

ABSTRACT During production of diethylenetriaminepentaacetic acid (DTPA), process waste water is generated in several production stages. Process wastewater is usually disposed of via waste water treatment plants. However, due to low biodegradability of DTPA in conventional waste water treatment, incineration constitutes the current method of choice. The main disadvantage of incineration is high consumption of primary energy sources leading to substantial emission of carbon dioxide (CO2). Thus, an alternative method of process waste water treatment was investigated, which consists of an initial application of ozone and a subsequent biological treatment. In 2009, preliminary laboratory experiments were conducted to evaluate the elimination of DTPA in process waste water. Based on the initial results, the responsible authorities granted approval for large-scale ozonation of DTPA-containing wastewater in 2011. Additional laboratory scale experiments were carried out to assess the elimination of the target compound and the generation of its main transformation products using liquid chromatography – high resolution mass spectrometry. Through application of the postulated method, the concentration of DTPA and its derivatives can be reduced to levels assuring safe discharge into the receiving water. Additionally, a comparison of CO2 emissions showed that ozonation is an ecological alternative to incineration and, most likely, an economical as well, based on the local prices of primary energy sources.

Simultaneous high-efficiency removal of sulfamethoxazole and zinc (II) from livestock and poultry breeding wastewater by a novel dual-functional bacterium, Bacillus sp. SDB4.

The complex mixtures of antibiotics and heavy metals are commonly existed in livestock and poultry breeding wastewater. Effective and simultaneous removal of these toxic compounds by microorganisms, especially single strains, remains a considerable challenge. In this study, a novel functional strain SDB4, isolated from duck manure and identified as Bacillus sp., has been shown to possess high removal capabilities for both sulfamethoxazole (SMX) and Zn2+. The maximum removal efficiency achieved 73.97% for SMX and 84.06% for Zn2+ within 48 h in the single pollution system. It has great potential for eliminating SMX along with Zn2+, 78.45% of SMX and 52.91% of Zn2+ were removed in the 20 mg·L-1 SMX and 100 mg·L-1 Zn2+ binary system. Furthermore, the SMX-biotransformation capability of SDB4 was enhanced at low concentrations of Zn2+ (below 100 mg·L-1). The SMX biotransformation and Zn2+ adsorption data fitted well with the pseudo-first-order kinetic model, indicating that the two pollutants were in accordance with the same removal rule. N4-acetyl-SMX was identified as the main stable transformation product during SMX removal. FTIR analyses revealed that OH, NH2, C=O, C-N/N-H, and C-O-C played major roles in the adsorption of Zn2+. Our study of the dually functioning strain SDB4 provides a potential application for the simultaneous biological removal of antibiotics and heavy metals.

Fate, bioaccumulation and toxic effects of triclosan on a freshwater community – A mesocosm study

The antibacterial agent triclosan (TCS) is added to many daily-used consumer products and can therefore reach the aquatic environment via treated wastewater and potentially harm aquatic ecosystems. A 120 days pond mesocosm study was conducted in order to investigate the fate of TCS in water and sediment, its bioaccumulative potential in different biota as well as the effects of TCS and its main transformation product methyl-triclosan (M-TCS) on plankton, periphyton, macrophytes, and benthos communities. TCS was dosed once each in six pond mesocosms (nominal concentrations: 0.12, 0.6, 3.5, 21, 130 and 778 µg/L TCS, respectively) while two ponds served as controls. A concentration-dependent increase in the DT50 values from 5.0 to 15.0 and 7.5 to 16.3 days was observed for TCS in water and the whole pond system (water, sediment, biota), respectively. Consequently, the substance should be categorized as non-persistent. For TCS, the bioaccumulation factors (non steady-state conditions, BAFnssc) in Lymnaea stagnalis, Myriophyllum spicatum and periphyton were below the critical limit of 2000, above which a substance is classified as bioaccumulative. In contrast, a BAFnssc value of >10,000 was found for M-TCS in L. stagnalis, denoting that M-TCS definitely falls under this classification. Although strong effects on freshwater communities could only be observed in the highest TCS treatments, some periphyton species, such as Oedogonium spp., reacted very sensitive to TCS with an EC50 (time weighted average, 28 d) of 0.3 µg/L TCS. Considering the high bioaccumulative potential of M-TCS in combination with the observed effects of TCS at low doses suggests that the use of TCS, and therefore its release into the environment, should cease.

Transformation and degradation of barbaloin in aqueous solutions and aloe powder under different processing conditions

Aloe vera is one of the few edible species in the genus Aloe, and its products are widely used in foods, cosmetics, health care products, medicines and other fields. Barbaloin is the highest content of anthraquinones in aloe, which has potential allergenicity, and it is one of the important indicators for the quality control of aloe-containing products. Aiming at resolving the problems of barbaloin instability, easy sensitization and high residue, the transformation and degradation mechanisms of barbaloin under different processing conditions (temperature, pH, food additives and metal ions) were studied in this research, and the toxicity of the products were evaluated. The results showed that the transformation and degradation of barbaloin can be significantly accelerated by high temperature, alkaline conditions, calcium chloride, carboxymethyl cellulose, Fe3+ and Mg2+ (p < 0.001). However, they can be significantly inhibited by the acidic environment and Pb2+ (p < 0.001). And the transformation and degradation of barbaloin in aloe powder were almost the same as those in the barbaloin aqueous solution. The main transformation and degradation products of barbaloin were isobarbaloin, aloe emodin, 10-Hydroxyalloin A and 10-Hydroxyalloin B, and the other two unknown products were isomers. And aloe emodin may have greater toxicity hazards and potential safety risks. The molecular electrostatic potential properties also indicated that the 10th carbon atom of barbaloin, isobarbaloin, 10-Hydroxyaloin A and 10-Hydroxyaloin B may be more likely to break chemical bonds and generate new transformation and degradation products. These research results can be applied to the control of barbaloin and aloe emodin in the processing of aloe-containing products, so as to provide the basis for the better development and utilization of aloe.

Removal and fate of carbamazepine in the microbial fuel cell coupled constructed wetland system

Carbamazepine (CBZ), which is difficult to remove in the wastewater treatment system and easily forms toxic transformation products during the treatment process, is one of the priority pollutants of pharmaceuticals and personal care products (PPCPs). Increasing attention has been paid to explore their treatment technology without side effects from the treatment products. This study aims to reveal the removal and transformation of CBZ in the microbial fuel cell coupled constructed wetland (CW-MFC) system. The CW-MFC system was operated continuously at room temperature for nearly 80 days. The results show that CW-MFC system can effectively remove CBZ with an average removal rate of 97%. Three transformation products were identified by liquid chromatography−high-resolution mass spectrometry: 2-(2-oxoquinazolin-1(2H)-yl) benzoic acid (TP267), methyl 2-(2-oxoquinazolin-1(2H)-yl) benzoate (TP281), 2-(2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl) benzoic acid (TP283). Except TP281 in the influent, the other transformation products were formed in the system, which indicated that TP267 and TP283 were the main transformation products of CBZ. The formation pathway of transformation products could be explained by reactions including oxidation, hydrolysis, bond rupture and intramolecular reaction. The results also indicate that the CW-MFC system might be a promising technology for PPCPs treatment.

Photocatalytic Oxidation of Chlorantraniliprole, Imidacloprid, Pirimicarb, Thiamethoxam and Their Main Photoreaction InterMediates as Impacted by Water Matrix Composition under UVA-LED Exposure

Processes on wastewater treatment plants (WWTP) are not always efficient for pollutant removal. A new, low-cost, and effective technology is needed. In this work, the photocatalytic degradation of four insecticides, chlorantraniliprole, imidacloprid, pirimicarb, and thiamethoxam, has been examined in different water matrices (irrigation water, leaching waters, and WWTP effluent). Lab experiments were conducted with TiO2 and ZnO, as photocatalysts, with and without Na2S2O8 as an oxidant, exposed to UVA irradiation with LED lamps. Previously, different loadings of TiO2 and ZnO were assessed on the disappearance kinetics of the different insecticides to know the optimal efficiency. The effect of water matrices, susceptible to being contaminated with the target insecticides, was discussed when the photocatalytic system TiO2/Na2S2O8 was applied. The abatement of their main transformation products (TPs) was also monitored during the studied photoperiods. A total of 13 TPs were detected in the different water matrices studied. All of them were formed and eliminated during the photoperiod, except thiamethoxam urea which was present from the beginning of the experiments due to its hydrolysis in water. In conclusion, UVA-LED lamps are a good source to carry out heterogeneous photocatalysis in WWTP, since its high efficiency, low-cost, long lifetime, and effectiveness on pollutant removal.

Heme Oxygenase-1 Signaling and Redox Homeostasis in Physiopathological Conditions.

Heme-oxygenase is the enzyme responsible for degradation of endogenous iron protoporphyirin heme; it catalyzes the reaction’s rate-limiting step, resulting in the release of carbon monoxide (CO), ferrous ions, and biliverdin (BV), which is successively reduced in bilirubin (BR) by biliverdin reductase. Several studies have drawn attention to the controversial role of HO-1, the enzyme inducible isoform, pointing out its implications in cancer and other diseases development, but also underlining the importance of its antioxidant activity. The contribution of HO-1 in redox homeostasis leads to a relevant decrease in cells oxidative damage, which can be reconducted to its cytoprotective effects explicated alongside other endogenous mechanisms involving genes like TIGAR (TP53-induced glycolysis and apoptosis regulator), but also to the therapeutic functions of heme main transformation products, especially carbon monoxide (CO), which has been shown to be effective on GSH levels implementation sustaining body’s antioxidant response to oxidative stress. The aim of this review was to collect most of the knowledge on HO-1 from literature, analyzing different perspectives to try and put forward a hypothesis on revealing yet unknown HO-1-involved pathways that could be useful to promote development of new therapeutical strategies, and lay the foundation for further investigation to fully understand this important antioxidant system.

Fungal degradation of selected medium to highly polar pesticides by Trametes versicolor: kinetics, biodegradation pathways, and ecotoxicity of treated waters.

The massive use of pesticides represents one of the main causes of environmental deterioration, as they have adverse effects on non-target organisms. Thus, the development of technologies capable of reducing their release into the environment is urgently needed. This study reports for the first time the white-rot fungus Trametes versicolor as an alternative towards the degradation of medium to highly polar pesticides such as the organophosphate malathion, and the neonicotinoids acetamiprid and imidacloprid. Specifically, T. versicolor could completely remove 1mg/L of malathion in an Erlenmeyer flask within 48h, while experiments of acetamiprid and imidacloprid (4mg/L), conducted in air-pulse fluidized bioreactors, resulted in degradation percentages of 20% and 64.7%, respectively, after 7days of operation. Enzymatic exploration studies revealed that the cytochrome P450 system, instead of the extracellular enzyme laccase, is involved in the degradation of acetamiprid and imidacloprid. The degradation pathways were proposed based on the main transformation products (TPs) formed in the solutions: seven in the case of malathion, and two and one in the case of imidacloprid and acetamiprid, respectively. Although the TPs identified were predicted to be less toxic than the investigated pesticides, the toxicity of the individual solutions slightly increased throughout the degradation process, according to the Microtox assay. However, the solution toxicity was always below the threshold established in the local regulation. Although additional research is needed to implement this treatment at a pilot plant scale, this work highlights the potential of T. versicolor to bio-remediate pesticide-contaminated waters.

Photocatalytic degradation of four insecticides and their main generated transformation products in soil and pepper crop irrigated with reclaimed agro-wastewater under natural sunlight

This work is the first-ever study of the concurrence of four insecticides (chlorantraniliprole, imidacloprid, pirimicarb and thiamethoxam) and their main transformation products (TPs) in soil and pepper crop irrigated with reclaimed and non-reclaimed water under agricultural field conditions. Field experiments were conducted using different irrigation supplies: control water (CW), wastewater polluted with phytosanitary commercial products containing the studied insecticides (WW) and reclaimed wastewater after a photocatalytic processing with TiO2/Na2S2O8 at pilot plant under sunlight (RWW). Photocatalytic treatments removed most of the insecticides and their TPs generated during the photoperiod. Neither target insecticides nor their TPs were detected in pepper samples when CW and RWW were used as irrigation source, whereas the four insecticides and two TPs were detected when WW was used. In the experiment carried out with WW, all insecticides and eight TPs were detected in soil samples. The impact of using reclaimed water on the quality of pepper crop was also assessed, showing barely any significant difference.

Study of biotransformation of cholesterol 3β-methyl ether by mycobacteria Mycobacterium sp.

The influence of exogenous factors on the selectivity of biotransformation of cholesterol 3β-methyl ether by Mycobacterium sp. was studied. The main product of the microbiological transformation was Δ5-dehydroepiandrosterone 3β-methyl ether. The presence of methyl-β-cyclodextrin in the bacterial growth medium led to a change in the ratio of the reaction products and an increase in the yield of Δ4-androstene-3,17-dione. Aliphatic saturated and unsaturated carboxylic acids were also formed in the course of biotransformation.

Exposure to DDT and HCH congeners and associated potential health risks through khat (Catha edulis) consumption among adults in South Wollo, Ethiopia

Khat (Catha edulis) chewing is widespread in the region of East Africa. Even low levels of organochlorine pesticides (OCPs) in khat could induce public health concern. In a market-based study, from five popular khat varieties, a total of 35 composite khat samples were analyzed for dichlorodiphenyltrichloroethane (DDT) and its main transformation products, and four hexachlorocyclohexane (HCH) isomers. Extraction was carried out by quick, easy, cheap, effective, rugged and safe method (QuEChERS). OCP concentrations were determined by head space solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME–GC–MS). Every sample contained β-HCH above the maximum residue limit set by the European Commission. For total DDT, this was the case for 25.7% of the samples. The ratios of (p,p′-DDD + p,p′-DDE) to p,p′-DDT were less than one for 85% of khat samples, demonstrating recent use of DDT in khat farmlands. Conversely, the ratio of β-HCH to total HCH varied from 0.56 to 0.96, implying historical input of technical HCH. Assuming a daily chewable portion of 100 g, dietary intakes of p,p′-DDT, total DDT and total HCH by adults ranged from 3.12 to 57.9, 6.49 to 80.2 and 39.2 to 51.9 ng (kg body weight)−1 day−1, respectively. These levels are below acceptable levels suggested by international organizations. Chewing khat showed lower non-cancer health risk, but showed relatively higher cancer risk in terms of OCPs. Because khat is chewed without being subjected to any treatment, uncertainties associated with estimated intakes and health risks should be low. Therefore, this practice is of great concern.

PH-Dependent mechanisms and kinetics of the removal of acetaminophen by manganese dioxide

Acetaminophen is commonly found in aquatic environments because it is widely used as an analgesic. In this study, the extent of transformation and adsorption of acetaminophen by manganese dioxide (MnO2) at different pH conditions was systematically investigated. The adsorption of acetaminophen by MnO2 was significant under acidic conditions but negligible under neutral and alkaline conditions. This indicates that the rate-determining steps in the removal of acetaminophen are electron transfer under acidic conditions and precursor complex formation under neutral and alkaline conditions. The kinetic simulation result is consistent with the above results, and the kinetics can be described using a surface complexation and transformation kinetic model if the initial concentration of acetaminophen exceeds the total concentration of the reactive surface sites on MnO2. Otherwise, the Michaelis–Menten model and the pseudo-first-order kinetic model can be used to describe the removal kinetics under acidic conditions and under neutral and alkaline conditions, respectively. The main transformation products were p-benzoquinone and a dimer of 4-aminophenol and acetaminophen under acidic and alkaline conditions, respectively. This indicates that dehydration–oxidation is the main pathway only under acidic conditions. Under alkaline conditions, the main transformation mechanism is dimerization–hydrolysis.

Ciprofloxacin-degrading Paraclostridium sp. isolated from sulfate-reducing bacteria-enriched sludge: Optimization and mechanism

Ciprofloxacin (CIP), one of the most widely used fluoroquinolone antibiotics, is frequently detected in the effluents of wastewater treatment plants and aquatic environments. In this study, a CIP-degrading bacterial strain was isolated from the sulfate reducing bacteria (SRB)-enriched sludge, identified as Paraclostridium sp. (i.e., strain S2). The effects of critical operational parameters on CIP removal by the strain S2 were systematically studied and these parameters were optimized via response surface methodology to maximize CIP removal. Furthermore, the pathway and kinetics of CIP removal were investigated by varying the initial CIP concentrations (from 0.1 to 20 mg/L). The CIP removal was characterized by rapid sorption followed by biotransformation with a specific biotransformation rate of 1975.7 ± 109.1 µg/g-cell dry weight/h at an initial CIP concentration of 20 mg/L. Based on the main transformation products, several biotransformation pathways have been proposed including piperazine ring cleavage, OH/F substitution, decarboxylation, and hydroxylation as the major transformation reactions catalyzed by cytochrome P450 and dehydrogenases. Acute toxicity assessment apparently shows that CIP biotransformation by strain S2 resulted in the formation of less toxic intermediates. To the best of our knowledge, this is the very first study in which a key functional microbe, Paraclostridium sp., highly effective in CIP biotransformation, was isolated from SRB-enriched sludge. The findings of this study could facilitate in developing appropriate bioaugmentation strategy, and in designing and operating an SRB-based engineered process for treating CIP-laden wastewater.

Insights into pH-dependent transformation of gibberellic acid in aqueous solution: Transformation pathway, mechanism and toxicity estimation

Gibberellic acid (GA3) is widely used in agriculture and maybe transfer with groundwater flow, which is an endocrine disruptor, but few studies have focused on the transformation pathway and toxicity assessment of GA3 and its products. Here, GA3 and its transformation products in aqueous solution were identified and quantified by liquid chromatography mass spectrometry hybrid ion trap time-of-flight (LCMS−IT−TOF) and high-performance liquid chromatography (HPLC), respectively. The results showed that the half-life of GA3 transformation in ultrapure water was 16.1–24.6 days at pH=2.0–8.0, with the lowest half-life occurring at pH=8.0 and highest half-life occurring at pH=3.3. Isomerized gibberellic acid (Iso-GA3) and gibberellenic acid (GEA) were the main transformation products with a little hydroxy gibberellic acid (OH-GA3). In North China groundwater, the mass balance of GA3 and its products was 76.2%, including Iso-GA3 (58%), GEA (7.9%), GA3 (7.3%) and OH-GA3 (3%) after reaching transformation equilibrium. Using Gaussian 09 for chemical computation, it was found that the transformation mechanism of GA3 was dependent upon the bond energy and the stereochemical feature of its molecular structure. GA3 always isomerized from the γ-lactone ring due to the lowest bond energy between the oxygen terminus of the γ-lactone ring and A ring. While GA3 and its transformation products all had developmental toxicity, the predicated LC50 (96 hr) and LD50 of the main products of GA3 were much lower than those of GA3, indicating GA3 would be transformed into higher toxicity derivatives in water environments, posing a significant health risk to humans and the environment.

Synergistic mechanism and degradation kinetics for atenolol elimination via integrated UV/ozone/peroxymonosulfate process

The present research systematically investigates the atenolol (ATL) degradation in integrated UV/Ozone (O3)/peroxymonosulfate (PMS) process focusing on the synergistic mechanism, reaction kinetics, pollutant degradation pathway and antibacterial activity. The results manifested that the integrated UV/O3/PMS process showed the noteworthy superiority to ATL degradation compared with UV/PMS, UV/O3 and O3/PMS systems. Simultaneously, the impacts of operating parameters like PMS dosage, initial ATL concentration, solution pH and water matrix were comprehensively explored. The ATL elimination efficiency increased linearly with PMS dose and significantly enhanced in alkaline conditions. The •OH and SO4•− were the primary reactive radicals for ATL oxidation in UV/O3/PMS system based on the radical scavenging experiments and electron paramagnetic resonance characterization. Besides, a simplified kinetic model on the basis of the dominant reactions and the steady-state assumption was established to foretell the relative contributions of reactive oxidants for ATL elimination in UV/O3/PMS process. Main transformation products were determined via UPLC-QTOF-MS to infer the possible degradation pathways of ATL. Furthermore, the UV/O3/PMS process could distinctly mitigate the antibacterial activity of ATL and its intermediates to E. coli and B. subtilis. Our findings may have critical implications for the development of novel oxidation processes for recalcitrant contaminants mitigation in water purification.

An innovative microbial electrochemical ultraviolet photolysis cell (MEUC) for efficient degradation of carbamazepine

Discharge of recalcitrant pharmaceuticals into aquatic environments can lead to serious negative environmental effects. While traditional wastewater treatment plants (WWTPs) are efficient for a wide range of non-toxic pollutants (i.e. ammonia), some wastewater streams contain recalcitrant toxic trace micropollutants such as pharmaceuticals that cannot be removed by the treatment processes that are typically employed in common WWTPs. Herein, an innovative 20 L microbial electrochemical ultraviolet photolysis cell (MEUC) was developed for the first time by the integration of a UV irradiation and a bioelectrochemical system, which exhibited efficient treatment of carbamazepine-a model pharmaceutical compound. Notably, neither the UV irradiation nor the bioelectrochemical system alone could effectively eliminate carbamazepine. The effect of operational parameters including applied voltage, cathodic aeration rate, UV intensity, and hydraulic retention time were evaluated. The obtained results elucidated that the degradation of carbamazepine was consistent with pseudo-first-order reaction kinetics, and required a lower energy input than traditional advanced oxidation processes. Five main transformation products were identified, and probable transformation pathways were established. Furthermore, the eco-toxicity as tested by Vibrio fischeri showed no significant bioluminescence inhibition by the treated carbamazepine effluent. Finally, the MEUC system was further tested with a real wastewater matrix, which again exhibited effective removal of carbamazepine. This paper provides a proof-of-concept verification of the novel MEUC system, which contributes insight for the subsequent vigorous development of the application of such efficient and cost-effective technologies for the treatment of trace pharmaceuticals wastewater.

Ozonation of carbamazepine and its main transformation products: product determination and reaction mechanisms

Carbamazepine (CBZ) is a recalcitrant pharmaceutical often detected in wastewater and in the environment. CBZ can be removed from wastewater through advanced oxidation treatment methods such as ozonation. In this study, CBZ and its transformation product 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-dione (BQD) were ozonated, and the formation and transformation of their ozonation products were investigated using liquid chromatography coupled to ion trap mass spectrometry and high-resolution mass spectrometry as well as nuclear magnetic resonance (NMR). The main products, 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM) and BQD were quantified using isolated standards and LC-UV. Of the original CBZ concentration, 74% was transformed into BQM and 83% of BQM was further transformed into BQD. Both products are more stable than CBZ and could still be detected after 240 min of ozonation. Another major product, 2,2′-azanediyldibenzaldehyde (TP225) was for the first time identified using NMR. Twelve further CBZ products were identified.