Διερεύνηση της τύχης ενδοκρινικών διαταρακτών και φαρμακευτικών ουσιών κατά την εφαρμογή υπεριώδους ακτινοβολίας σε επεξεργασμένα αστικά λύματα

Abstract

Αντικείμενο της παρούσας μεταπτυχιακής εργασίας είναι η διερεύνηση της τύχης ενδοκρινικών διαταρακτών (TCS, BPA, NP, NP1EO, NP2EO) και φαρμακευτικών ουσιών (DCF, NPX, IBU, KTP) κατά την εφαρμογή υπεριώδους ακτινοβολίας σε επεξεργασμένα αστικά λύματα. H εργασία αυτή εκπονήθηκε στο Εργαστήριο Υγειονομικής Τεχνολογίας του Εθνικού Μετσόβιου Πολυτεχνείου. Σε πρώτο στάδιο πραγματοποιείται βιβλιογραφική ανασκόπηση για αυτές τις δύο ομάδες ενώσεων, ενώ σε επόμενο στάδιο γίνεται εκτενής ανάλυση ξεχωριστά για κάθε μία από τις 9 συνολικά ουσίες που μελετήθηκαν στη παρούσα εργασία. Στη συνέχεια γίνεται αναφορά στις μεθόδους και στα πειραματικά πρωτόκολλα που ακολουθήθηκαν για τη διεξαγωγή των εργαστηριακών πειραμάτων. Αρχικά μελετήθηκε η εφαρμογή της υπεριώδους ακτινοβολίας (UV) σε δευτεροβάθμια επεξεργασμένα λύματα από το Κέντρο Επεξεργασίας Λυμάτων Ψυτάλλειας, στα οποία είχαν προστεθεί οι εξεταζόμενες ενώσεις σε επίπεδα συγκεντρώσεων παρόμοια με αυτά που ανιχνεύονται σε μονάδες επεξεργασίας αστικών λυμάτων. Στη παρούσα εργασία εφαρμόστηκαν κυρίως εντάσεις UV ακτινοβολίας αντίστοιχες με αυτές που εφαρμόζονται κατά την απολύμανση, ωστόσο έγιναν δοκιμές και σε μεγαλύτερες. Τελικά αποδείχτηκε ότι η μέθοδος UV από μόνη της δεν επαρκεί για να επιτευχθεί ικανοποιητική απομάκρυνση της πλειοψηφίας των εξεταζόμενων ουσιών παρά μόνο σε πολύ υψηλές εντάσεις UV ακτινοβολίας. Στη συνέχεια πραγματοποιήθηκαν πειράματα με σκοπό να μελετηθεί η αποτελεσματικότητα ως προς την απομάκρυνση των ίδιων ουσιών (που εξετάστηκαν με τη μέθοδο UV) από δευτεροβάθμια επεξεργασμένα λύματα, με τη μέθοδο UV/Η2Ο2. Αυτή η μέθοδος επεξεργασίας ανήκει στις προηγμένες διεργασίες οξείδωσης. Από τα πειραματικά αποτελέσματα προέκυψε ότι η προσθήκη του Η2Ο2 σε συνδυασμό με εντάσεις UV ακτινοβολίας αντίστοιχες με αυτές που εφαρμόζονται κατά την απολύμανση, βελτίωσε τα ποσοστά απομάκρυνσης των περισσότερων ουσιών που εξετάστηκαν σε σχέση με εκείνα που προέκυψαν με τη μέθοδο UV. Ωστόσο και σε αυτή τη περίπτωση τα ποσοστά απομάκρυνσης που επετεύχθησαν για τις περισσότερες ουσίες ήταν χαμηλά. Επιπλέον στα πλαίσια αυτής της εργασίας μελετήθηκε η απομάκρυνση αυτών των ουσιών από τριτοβάθμια επεξεργασμένα λύματα μέσω της προσρόφησης σε ενεργό άνθρακα σε σκόνη (PAC). Κατά τη διάρκεια του πειράματος αυτού μελετήθηκε η επίδραση στην απομάκρυνση παραμέτρων, όπως η συγκέντρωση του ενεργού άνθρακα και η τιμή της αρχικής συγκέντρωσης των ουσιών. Από τα αποτελέσματα προέκυψε πως η μέθοδος αυτή μπορεί να δώσει ικανοποιητικά ποσοστά απομάκρυνσης για την πλειοψηφία των εξεταζόμενων ουσιών, στη περίπτωση όμως που προστίθενται υψηλές συγκεντρώσεις ενεργού άνθρακα σε σκόνη. Ακόμη ακολούθησαν πειράματα στα οποία προσδιορίστηκε η τοξικότητα, με τη μέθοδο της βιοφωταύγειας του Vibrio fischeri, των συγκεκριμένων ενώσεων μετά από την επεξεργασία με μεθόδους στις οποίες εφαρμόζεται υπεριώδης ακτινοβολία (UV, UV/Η2Ο2) σε υπερκάθαρο νερό και σε δευτεροβάθμια επεξεργασμένα λύματα. Από τα πειραματικά αποτελέσματα με τη μέθοδο UV και στις δύο περιπτώσεις δεν παρατηρήθηκε τοξικότητα. Αντίθετα στη περίπτωση που εφαρμόστηκε η μέθοδος UV/Η2Ο2 παρατηρήθηκε μικρή τοξικότητα και στα λύματα και στο υπερκάθαρο νερό. Τέλος πραγματοποιήθηκε μία σύγκριση μεταξύ μεθόδων που εφαρμόζονται κατά την απολύμανση των λυμάτων (χλωρίωση, UV, UV/Η2Ο2). Το κριτήριο με το οποίο συγκρίθηκαν ήταν η τοξικότητα που προκαλείται με τη παρουσία των εξεταζόμενων ουσιών σε υπερκάθαρο νερό, η οποία προσδιορίστηκε με τη μέθοδο της βιοφωταύγειας του Vibrio fischeri. Επίσης συγκρίθηκαν δύο μέθοδοι απολύμανσης (χλωρίωση, UV) εξετάζοντας μεμονωμένα δύο συγκεκριμένες ουσίες που περιέχονταν σε υπερκάθαρο νερό ως προς τη τοξικότητα που προκλήθηκε με την ίδια μέθοδο προσδιορισμού. Η εργασία αυτή ολοκληρώνεται με μια σύνοψη των κυριοτέρων συμπερασμάτων που προέκυψαν από τα πειράματα που πραγματοποιήθηκαν στο πλαίσιο της παρούσας μεταπτυχιακής εργασίας.

During the last decade, pharmaceuticals (PhACs) and endocrine disrupting chemicals (EDCs) have been classified as the most frequently detected organic pollutants in the environment. Among them, the acidic non-steroidal anti-inflammatory drugs (NSAIDs), diclofenac (DFC), naproxen (NPX), ibuprofen (IBF) and ketoprofen (KFN), and the phenolic EDCs, triclosan (TCS), bisphenol (BPA), nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO), receive great research interest, and review articles rank them as priority emerging pollutants due to their worldwide high consumption and their reported toxic effects on aquatic organisms. The scope of this master thesis study, was to investigate the fate of endocrine disruptors and pharmaceuticals compounds during UV process, at treatment municipal wastewater. As part of this thesis examined and other methods in order to remove such substances from wastewater. The study was conducted at the Sanitary Engineering Laboratory of the School of Civil Engineering, at the National Technical University of Athens.

ii. Pharmaceuticals and endocrine disrupting chemicals Pharmaceuticals constitute a large group of human and veterinary medicinal compounds which have long been used throughout the world. Therefore, over the past few years they are considered to be an emerging environmental problem. There are several potential sources and mechanisms through which these compounds reach the environment. These chemicals used by humans, as well as their metabolites, enter the Sewage Treatment Plants (STP’s) through discharges from production facilities, hospitals and private household effluents. Although the amount of these pharmaceuticals in the aquatic environment is low, its continuous input may constitute in the long – term a potential risk for aquatic and terrestrial organisms. Also, it is presently unclear whether there would be increased toxic effects or synergistic effects through exposure to multiple compounds, even at very low levels. Endocrine disrupting compounds (EDCs) are chemicals with the potential to elicit negative effects on the endocrine systems of humans and wildlife. An endocrine disruptor by definition is an exogenous agent that interferes with the synthesis, secretion, transport, binding, action and elimination of natural hormones in the body, which are responsible for the maintenance of homeostasis, reproduction, development and behavior. EDCs have been attributed as a cause of reproductive disturbance in humans and wildlife. Human exposure to these chemicals in the environment is a critical concern with unknown long – term impacts. Natural and synthetic EDCs are released into the environment by humans, animals and industries mainly through sewage treatment systems that end up into the receiving bodies (soil, surface water, sediment and ground water). Concluding pharmaceuticals and endocrine disrupting chemicals are used in many consumer products such as cosmetics, detergents, pharmaceuticals, plastics etc. Also these chemicals exist in extremely low concentration (μg/L or ng/L), that means that highly sensitive measurement of EDCs is necessary, including chemical monitoring, such as gas chromatography-tandem mass spectrometry (GC – MS). EDCs and pharmaceuticals main distribution in the environment is illustrated in Fig. 1.

iii. Wastewater treatment methods The scope of this work was to determine the removal of the tested compounds, from biological treated wastewater, in order to achieve the limits of regulations for safe water supply and make them acceptable for reuse. It is well known that these compounds are only partially removed through conventional biological wastewater treatment thus being detected in secondary effluents. Disinfection of biologically treated wastewater is the minimum additional treatment stage required in order to provide for safe wastewater reuse. As the primary goal of disinfection is to reduce wastewater microbiological content, the effectiveness of such methods to reduce pharmaceuticals is unclear. In view of the above the aim of this study was to examine whether disinfection and other treatment methods, employed to provide for safe wastewater reuse, can lead to effective removal of EDCs and pharmaceuticals from wastewater. More specifically, this thesis paper details an investigation of the removal of selected compounds using three different processes: 1. UV irradiation alone 2. an advanced oxidation process (AOP), specifically UV combined with hydrogen peroxide (UV/H2O2) 3. adsorption on powder activated carbon (PAC) UV treatment was carried out using 3 L biologically treated water (i.e., effluent from secondary sedimentation tanks from a municipal wastewater treatment plant of Psitallia, Greece). The selected PhACs and EDCs were spiked in the biologically treated water in a concentration of 1000 ng/L. The UV reactor that used in the batch experiments was TROJAN SYSTEM UV 4000 (Fig. 2). The source of ultraviolet radiation was a low-pressure UV lamp (LP lamp) that emits at 254 nm. The spiked water samples were placed under an automated shutter in an open dish (100 mL) containing a small stir bar to provide constant mixing to the 5.7 cm depth sample. Also the UV batch experiments were conducted at pH 8 and at room temperature. Before and after exposing the spiked samples to UV light, a calibrated radiometer (IL1700 SED 240) was placed under the UV source at the same height as the water level in the dish, to obtain incident irradiance measurements. The UV fluences applied were 40, 80, 100, 150, 1000 mJ/cm2. Then a pretreatment of the samples was followed for the quantification of the selected compounds with GC – MS. In the UV/H2O2 oxidation batch experiments before the exposure hydrogen peroxide 30 % was added to the samples. Initial H2O2 concentrations were 6, 12 and 20 mg/L for each UV/H2O2 experiment. The UV fluences applied were 80, 150, 1000 mJ/cm2. After exposure, a solution of Na2SO3 was used to quench the residual hydrogen peroxide. Then the same procedure with UV treatment was followed for the quantification of the selected compounds with GC – MS. Finally, experiments carried out, in order to determine the efficiency to the removal of the examined compounds, by adsorption on activated carbon. As samples, were used tertiary treated effluents, at which examined compounds were spiked to concentrations of 300, 500, 1000 ng/L. Also coal carbon (WPM7) in powder form was added at concentrations 15, 50, 100 mg/L. During this experiment, were studied the effects on removal, of parameters such as concentration of activated carbon and the initial concentration of the compounds. Similar other processes the samples pretreated for quantification of the examined compounds with GC – MS.

iv. Results UV disinfection at UV doses in the order of 40 – 150 mJ/cm2 is not effective to remove EDCs and pharmaceuticals, except TCS and KFN. From the target compounds tested TCS, NP2EO, DCF and KFN exhibited appreciable removal between 80 – 90 % only at higher UV doses (1000 mJ/cm2). The removal rates of target compounds at typical UV doses for disinfection are shown at Fig. 3. For the UV/H2O2 process the experimental results showed that the addition of H2O2 in combination with UV radiation intensities similar to those applied in the disinfection, improved removal rates of most substances tested compared to those obtained with the method of UV alone. KFN is only presented significant removal. However in this case the removal rates achieved for most substances were low. The removal rates of target compounds at typical UV doses for disinfection are shown at Fig. 4. Results from the experiments on activated carbon showed that only TCS, BPA, NPX, IBP, KTP can be correlated with the empirical relationship of Freundlich. Overall it seemed that for low concentrations of PAC (15 mg/L) the removal of target compounds averaged 10 - 35%. Exception was BPA, which had satisfactory removal (60%). In contrast to higher concentrations of PAC (50 - 100 mg/L) better results achieved. In particular for the majority of substances removal rates were high and ranged from 50 - 90%. The exceptions were the two endocrine disruptors (NP1EO NP2EO), whose removal was negligible (10 - 18%). It was also shown that pharmaceutical compounds (excluding IBP) showed similar behavior to the adsorption on activated carbon, which on endocrine disrupters not. Finally for TCS and NP experimental data showed that the initial concentration of the substances affected the adsorption on the active carbon.

v. Toxicity Also, experiments took place in order to investigate the toxicity of endocrine disruptors and pharmaceutical compounds in biologically treated water and ultra pure water, after UV, UV/H2O2 processes, by applying the method of bioluminescence, using the bacterium Vibrio fischeri. This bacterium is an aquatic microorganism that displays significantly greater sensitivity of the microorganisms present in wastewater treatment plants. It was found that after the exposure of selected compounds to UV radiation wasn't detected toxicity. In contrary after the UV/H2O2 treatment it was found that parent compounds shown small levels of toxicity both in biologically treated water and ultra pure water. This is probably due to the presence of organic compounds in wastewater reacted with H2O2 to form toxic compounds. Additional cases of toxicity examined for two substances separately (NP, BPA) in ultra pure water after exposure to UV radiation. Also in this case no toxicity was detected.

vi. Conclusions The experiments of this thesis showed that by applying UV radiation intensities similar to those at wastewater treatment plants is not possible to effectively remove pharmaceuticals and endocrine disrupting chemicals from wastewater. The method UV/Η2Ο2 showed that the addition of Η2Ο2 in typical UV radiation intensity improved removal rates of more drugs than the method of UV. Wastewater treatment with the use of powder activated carbon yielded very satisfactory results. Using high concentrations of activated carbon (50 - 100 mg/L) for the most relevant substances removal by tertiary treated effluents was up to 90 %.