Adsorption of benzalkonium chlorides onto powdered activated carbon: mechanisms and detoxification

Because disinfectants have been essential during the COVID-19 pandemic, the global demand for benzalkonium chlorides (BACs) has significantly increased. BACs can inactivate coronaviruses, but are known as toxic. In this study, we investigated the adsorption mechanisms of BAC12, BAC14, and BAC16 in water using powdered activated carbon (PAC). The effects of the reaction time, pH, and temperature on the adsorption kinetics of BACs were examined. The adsorption reaction followed pseudo-second-order kinetics, and better fitted to the Langmuir isotherm than the Freundlich isotherm. The best adsorption of BACs was achieved at neutral pH conditions. Thermodynamic analysis revealed that adsorption of BACs onto PAC is a spontaneous and endothermic process. Competitive adsorption experiments revealed that BACs with longer alkyl chains were adsorbed more effectively onto PAC than shorter alkyl chain BACs, implying that, while the electrostatic interaction is an important adsorption mechanism for BAC12, van der Waals interaction plays a more important role during the adsorption of BAC14 and BAC16. Finally, we observed the partial detoxification (69%) BAC in adsorption treated water with PAC using a Microtox test.

Environmental concerns about the effects of effluents from wastewater treatment plants in tourist areas of the Alps: toxicity in aquatic microorganisms

Are the effluents of wastewater treatment plants in high mountains of concern for aquatic biodiversity? To answer this question, we carried out an experimental study testing the short-term toxicity of some Pharmaceutical Active Compounds (PhACs) in the effluents of a plant in a mountain valley of the Italian Alps sampled during the high tourist season (i.e., the ski season) when PhACs contamination is higher. We used different tools, taking as a model the bacterium Aliivibrio fischeri: the “whole-mixture approach” (Microtox test), “component-based approach”, predictive models “Concentration Addition (CA)”, “Independent Action (IA)”, and Combination Index (CI)”. We investigated the nature of interactions potentially occurring among seven selected PhACs (clarithromycin, naproxen, acetaminophen (paracetamol), ibuprofen, diclofenac, carbamazepine, and amoxicillin). This study showed that anti-inflammatory ibuprofen and diclofenac have higher short-term toxicity (IC50 <100 mg L-1) for A. fischeri compared with antibiotics, whose toxic effects are expected to become visible in the long term. Furthermore, based on the CI method, the seven PhACs seem not to interact in a synergistic or antagonistic way, but the final effect of their mixture seems to be equal to the sum of their individual effects. Notwithstanding the high tourist pressure, the Microtox test reported an overall toxicity of only 21%, which drops to 7% in the receiving water body, the Vermigliana stream. These values, besides the predictions by CA and IA, are not alarming per se, i.e., the treated effluent of the plant in the period of maximum tourist pressure can be considered no harmful to aquatic microorganisms. However, based on other studies highlighting negative effects of the diluted treated effluent of the same plant on macroinvertebrate community structure, we suggest that other model organisms be considered, including algae, insects, and fish, to assess the real ecological risk to wildlife of an effluent. The experimental tests on A. fischeri are useful for fast, preliminary information on the level of risk for freshwater ecosystems, but they should be combined with field studies and experiments on the wild populations to increase the ecological realism.

A comprehensive study on bisphenol A degradation by newly isolated strains Acinetobacter sp. K1MN and Pseudomonas sp. BG12

Bisphenol A (BPA) is an endocrine disrupting chemical. Its extensive use has led to the wide occurrence of BPA in various environmental ecosystems, at levels that may cause negative effects to the ecosystem and public health. Although there are many bacteria able to BPA utilization, only a few of them have a strong capacity for its biodegradation. Therefore, it is important to search for new bacteria strains, investigate their BPA biodegradation ability and potential effect of pH and other organic compounds on the process. These tasks have become the object of the present study. The results of our research show that for the newly isolated strains Acinetobacter sp. K1MN and Pseudomonas sp. BG12 after 15 days, with an initial BPA concentration of 100 mg L− 1, the highest BPA removal was achieved at pH 8, while sodium glutamate as a biostimulant best accelerated BPA degradation. Kinetic data for BPA biodegradation by both strains best fitted the Monod model. The specific degradation rate and the half saturation constant were estimated respectively as 8.75 mg L− 1 day− 1 and 111.27 mg L− 1 for Acinetobacter sp. K1MN, and 8.6 mg L− 1 day− 1 and 135.79 mg L− 1 for Pseudomonas sp. BG12. The half-maximal effective concentration (EC50) of BPA for Acinetobacter sp. K1MN was 120 mg L− 1 and for Pseudomonas sp. BG12 it was 123 mg L− 1. The toxicity bioassay (Microtox test) showed that elimination of BPA by both strains is accompanied by reduction of its toxic effect. The ability of tested strains to degrade BPA combined with their high resistance to this xenobiotic indicates that Acinetobacter sp. K1MN and Pseudomonas sp. BG12 are potential tools for BPA removal during wastewater treatment plant.

Removal of Azo Dye Acid Red 27 from Aqueous Solutions Using Classical and Modified Fenton Reagent with Zero-Valent Iron

The article compares the classic Fenton reagent (Fe2+/H2O2) with its modification with zero-valent iron (ZVI/H2O2) to remove azo dye Acid Red 27 from aqueous solutions at a concentration of 100 mg/L. For both methods, the most favorable parameter values ​​were determined at which visual discoloration of the solutions tested was obtained (for Fe2+/H2O2:pH 3.5, H2O2=60 mg/L, Fe2+/H2O2=0.3, t=15 min, and for ZVI/H2O2: pH 3, H2O2=40 mg/L, ZVI=80 mg/L, t=15 min). Under these conditions, the COD value was reduced by 71.5% and 69.2% for the classic Fenton and its modification, respectively. A reduction in toxicity was also obtained for Vibrio fischeri bacteria to below 25% by using the Microtox test. ZVI digestion at acidic pH for 10 minutes allowed to shorten the reaction time by about four times - from 15 to 4 minutes. BET analysis showed that the specific surface area increases with the digestion time, which significantly accelerates the reaction. The visual discoloration of aqueous solutions was obtained, and the final COD values ​​were very small, ranging from 49-53 mg O2/L. According to the Vibrio fischeri toxicity classification test for water samples, all solutions of dyes tested can be considered as non-toxic (toxicity value <25%). In the study presented, results of decreasing the COD value and concentration of the dye in the ZVI/H2O2 method obtained are slightly worse compared to the Fe2+/H2O2 method. However, taking the decolorisation time as a criterion, a four times faster decolorisation time was obtained in the ZVI/H2O2 method, compared to the Fe2+/H2O2 method.

Toxicity Assessment of Produced Water Using Microtox Rapid Bioassay

Aim: The study aimed at employing the Microtox test procedure in the current biological monitoring protocol as a reliable, rapid and ecologically relevant bioassay tool for toxicity assessment in environmental compliance monitoring of produced water discharges. Study Design: Inhibition of bioluminescence by V. fischeri [median effective concentration (EC50)] was employed as the toxicity index. Place and Duration of Study: Microbiology Department of Halden Laboratories, Port Harcourt, Nigeria / one month. Methodology: Percent reduction in bioluminescence by V. fischeri after 15-min exposure to the PW samples was recorded as median effective concentration (EC50) values. Results: The 15 min EC50 values of the untreated and treated produced water samples for V. fischeri was 1.0% and 23.27% respectively. Microtox test indicated the treated and untreated produced water samples were “very toxic” and “extremely toxic” respectively, after 15 min exposure time. Conclusion: These findings emphasize the need for adequate treatment of produced water to meet standard discharge limits of regulatory agencies in Nigeria, as both physicochemical analysis and bioassay (Microtox) suggested that the treated PW was toxic to V. fischeri. This study thus supports the use of Microtox (bacterial toxicity) system as a sensitive and rapid bioassay tool for biological monitoring protocol in Nigeria's petroleum industry.

Investigation of the Efficiency of the UV/H2O2 Process on the Removal of dye Acid Green 16 from Aqueous Solutions: Process Optimization and Toxicity Assessment

The effects of the removal of Acid Green 16 (100 mg AG-16/dm3, COD=111 mg O2/dm3) from aqueous solutions by the UV/H2O2 process in UV reactors: low pressure lamp (LP, 15W) and medium pressure lamps (MP, 150W) are presented. The best results of AG-16 removal were obtained for H2O2 250 mg/dm3 (99.85%, AG-16=0.15 mg/dm3) and 200 mg/dm3 (99.80%, AG-16=0.20 mg/dm3) for LP and MP lamps, respectively, with the same parameters, i.e. 30 min reaction time and pH 6. Under these conditions, the AG-16 solution was completely discolored and the COD removal efficiency was 57.3% (LP lamp) and 63,4% (MP lamp). However, at optimum conditions of decolorisation, no decrease in the toxicity of solutions (Microtox test) was observed. For the MP lamp, the toxicity of solutions remained at the same level as in the initial solutions (Toxicity Unit, TU=3), whereas in the case of the LP lamp, the TU value after the process increased to 6. In conclusion, the AOPs for toxic pollutants should also be optimised from the point of view of toxicity.

Analysis of the Metabolites of Indole Degraded by an Isolated Acinetobacter pittii L1

Indole and its derivatives are typical nitrogen heterocyclic compounds and have been of immense concern since they are known for the risk of their toxic, recalcitrant, and carcinogenic properties for human and ecological environment. In this study, a Gram-negative bacterial strain of eliminating indole was isolated from a coking wastewater. The strain was confirmed as Acinetobacter pittii L1 based on the physiological and biochemical characterization and 16S ribosomal DNA (rDNA) gene sequence homology. 400 mg/L indole could be completely removed within 48 h by the strain on the optimum condition of 37°C, pH 7.4, and 150 rpm. The organic nitrogen was converted to NH3-N and then to NO3- and the organic carbon was partially transferred to CO2 during the indole biodegradation. The metabolic pathways were proposed to explain the indole degradation based on the liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of indigo, 4-(3-Hydroxy-1H-pyrrol-2-yl)-2-oxo-but-3-enoic acid, and isatin. The toxicity of the biodegradation products was evaluated using the Microtox test, which revealed that the metabolites were more toxic than indole. Our research holds promise for the potential application of Acinetobacter pittii L1 for NHCs degradation, production of indigoids, and soil remediation as well as treatment of indole containing wastewater.

Ανίχνευση, μεταφορά και φωτολυτική διάσπαση φαρμακευτικών ενώσεων στο περιβάλλον

Σκοπός της παρούσας διατριβής ήταν: (α) Ο συστηματικός έλεγχος για την ανίχνευση υπολειμμάτων φαρμακευτικών ουσιών σε νερά Μονάδων Επεξεργασίας Υγρών Αποβλήτων στον Ελλαδικό Χώρο, (β) η μελέτη του ρυθμού απομάκρυνσης των φαρμακευτικών ουσιών από τις μονάδες αυτές, (γ) η εκτίμηση της περιβαλλοντικής τους επικινδυνότητας, (δ) η μελέτη της φωτολυτικής αποικοδόμησης επιλεγμένων φαρμακευτικών ουσιών σε διαφορετικούς τύπους επιφανειακών υδάτων (κινητική, προσδιορισμός προϊόντων μετασχηματισμού, μελέτη τοξικότητας), (ε) η μελέτη της φωτοκαταλυτικής αποικοδόμησής τους με την εφαρμογή του πειραματικού σχεδιασμού (κινητική, προσδιορισμός ανόργανων ιόντων και ολικού οργανικού άνθρακα, προσδιορισμός προϊόντων μετασχηματισμού, έλεγχος τοξικότητας) και (στ) η μελέτη της φωτοκαταλυτικής διάσπασης της ουσίας trimethoprim σε πιλοτική μονάδα φωτοκαταλυτικής αποικοδόμησης. Αρχικά, αναπτύχθηκε και βελτιστοποιήθηκε μια απλή αναλυτική μέθοδος προσδιορισμού των φαρμακευτικών ουσιών στα υγρά απόβλητα, η οποία βασίστηκε στην εφαρμογή της εκχύλισης δια της στερεάς φάσης (Solid Phase Extraction, SPE) σε συνδυασμό με υγρή χρωματογραφία συζευγμένη με φασματομετρία μάζας (LC-MS). Επιπλέον, πραγματοποιήθηκε περαιτέρω επιβεβαίωση των θετικών ανιχνεύσεων των φαρμακευτικών ουσιών στα υγρά απόβλητα, με τη χρήση του υβριδικού αναλυτή UHPLC–LTQ-Orbitrap MS. Επιλέχθηκαν είκοσι δραστικές φαρμακευτικές ουσίες και ένα προϊόν μετασχηματισμού και προσδιορίστηκαν τα επίπεδα των συγκεντρώσεών τους στην είσοδο και την έξοδο οκτώ ΜΕΥΑ διαφορετικών πόλεων της Ελλάδας, κατά τη διάρκεια ενός έτους. Τα επίπεδα των συγκεντρώσεων των ουσιών στις εισόδους κυμάνθηκαν από 9,3 έως 96648,3 ng/L, ενώ στις εξόδους από 6,6 έως 1076,0 ng/L. Οι ρυθμοί απομάκρυνσης των ουσιών κυμάνθηκαν μεταξύ υψηλών, μεσαίων και χαμηλών τιμών, ενώ σε κάποιες περιπτώσεις παρατηρήθηκαν αρνητικές απομακρύνσεις. Από τα αποτελέσματα προέκυψε ότι κάποιες ουσίες εμφάνισαν υψηλή επικινδυνότητα (RQ>1), με την ουσία triclosan να είναι η πιο κρίσιμη. Στη συνέχεια, πραγματοποιήθηκε μελέτη της φωτολυτικής και φωτοκαταλυτικής αποικοδόμησης δύο επιλεγμένων οργανικών ενώσεων (trimethoprim και omeprazole). Η μελέτη της φωτολυτικής τους αποικοδόμησης, πραγματοποιήθηκε σε διαφορετικούς τύπους νερών (απεσταγμένο, ποτάμιο, λιμναίο, θαλάσσιο), υπό την επίδραση τόσο τεχνητής (συσκευή Suntest), όσο και φυσικής ηλιακής ακτινοβολίας. Η ταυτοποίηση των ενδιάμεσων προϊόντων πραγματοποιήθηκε με τη χρήση του UHPLC/LTQ-ORBITRAP, όπου προσδιορίστηκαν συνολικά δεκαπέντε και εννέα προϊόντα μετασχηματισμού για τις ουσίες trimethoprim και omeprazole, αντίστοιχα. Για τη μελέτη της τοξικότητας, χρησιμοποιήθηκε το σύστημα Microtox test (Microtox 500, Azur), με τη χρήση των βακτηρίων Vibrio Fischeri. Ακολούθησε η μελέτη της φωτοκαταλυτικής αποικοδόμησης των φαρμακευτικών ουσιών, όπου πραγματοποιήθηκε εφαρμογή του στατιστικού πειραματικού σχεδιασμού. Οι βέλτιστες συνθήκες για τη μέγιστη φωτοκαταλυτική δραστικότητα της ουσίας trimethoprim ήταν οι: TiO2=460 mg/L, Ctrimethoprim= 5 mg/L και L.I.=628 W/m2, ενώ για την ουσία omeprazole ήταν οι: Comeprazole= 10 mg/L, TiO2=284 mg/L και τιμή pH=10. Οι μετρήσεις του ολικού οργανικού άνθρακα (Total Organic Carbon, TOC), πραγματοποιήθηκαν σε αναλυτή TOC V-csh της Shimadzu. Ο προσδιορισμός των ανιόντων (νιτρικών, νιτρωδών, θειϊκών) πραγματοποιήθηκε σε ιοντικό χρωματογράφο Dionex ICS-1500, ενώ ο προσδιορισμός των αμμωνιακών ιόντων βασίστηκε στη φασματοφωτομετρική μέθοδο Solorzano. Η ταυτοποίηση των ενδιάμεσων προϊόντων πραγματοποιήθηκε με τη χρήση του UHPLC/LTQ-ORBITRAP, όπου προσδιορίστηκαν δεκαέξι και δέκα προϊόντα μετασχηματισμού για το trimethoprim και το omeprazole, αντίστοιχα και ακολούθησε μελέτη της τοξικότητάς τους. Τέλος, πραγματοποιήθηκε μελέτη της φωτοκαταλυτικής αποικοδόμησης της ουσίας trimethoprim σε πιλοτική μονάδα φωτοκαταλυτικής αποικοδόμησης με τη χρήση TiO2, υπό την επίδραση φυσικής ηλιακής ακτινοβολίας.