Publikationsserver der RWTH Aachen University
Studies on the behaviour of endocrine disrupting compounds in a membrane bioreactor
Abstract
dc:descriptionThe present research focuses on the fate of hydrophobic micropollutants in a membrane bioreactor (MBR) and their removal in it. MBR represents one of the most promising innovations in the field of wastewater treatment because of the high efficiency in removal of organics and nutrients. The high quality of the effluent is obtained by the complete retention of suspended solids, the almost complete removal of pathogens, and the possibility to increase biodegradation of micropollutants because of the higher sludge retention time in MBR, in comparison to the conventional activated sludge treatment. For the micropollutants which have hydrophobic properties the challenge is to distinguish the real biodegradation from abiotic physico-chemical phenomena like adsorption and volatilisation during the membrane bioreactor treatment. In order to achieve it, the application of radiolabelled hydrophobic model markers is considered to be a powerful technique. In this study the possible fate of NP during wastewater treatment by using a lab-scale MBR was investigated. After a single pulse of the 14C-labelled-NP isomer (4-[1-ethyl-1,3-dimethylpentyl]phenol) as radiotracer, the applied radioactivity was monitored in the MBR system over 34 days. The balance of radioactivity at the end of the study showed that 42% of the applied radioactivity was recovered in the effluent as degradation products of NP, 21% was removed with the daily excess sludge from the MBR, and 34% was recovered as adsorbed in the component parts of the MBR. A high amount of NP was associated to the sludge during the test period, while degradation products were mainly found in the effluent. Partial identification of these metabolites by means of HPLC-tandem mass spectrometry coupled to radio-detection showed that they were alkyl-chain oxidation products of NP. The use of a radiolabelled test compound in a lab-scale MBR was found suitable to demonstrate that the elimination of NP through mineralization and volatilization processes under the applied conditions was negligible (both less than 1%). However, the removal of NP via sorption and the continuous release of oxidation products of NP in the permeate were highly relevant. The fate of two differently labelled radioactive forms of 17alpha-ethinylestradiol (EE2), one with the ring and the other one with the ethinyl group labelled was studied during the membrane bioreactor (MBR) process. The system was operated using a synthetic wastewater representative for the pharmaceutical industry and the activated sludge was obtained from a large-scale MBR treating pharmaceutical wastewater. Before the five days radioactive experiment, the activated sludge was adapted for 29 days continuously to non-labelled EE2. Balancing of radioactivity could demonstrate that mineralization amounted to less than 1% of the applied radioactivity. The EE2 residues remained mainly sorbed in the reactor, resulting in a removal of approximately 80% relative to the concentration in the influent. The same metabolite pattern in the radiochromatograms of the two differently labelled 14C-EE2 molecules led to the assumption that the elimination pathway does not involve the removal of the ethinyl group from the EE2 molecule. The bioaugmentation of membrane bioreactor in order to improve the degradation of recalcitrant nonylphenol during the wastewater treatment was studied. The 14C-labelled NP isomer 4-[1-ethyl-1,3-dimethylpentyl]phenol was applied as single pulse to the membrane bioreactor bioaugmented with the bacterium Sphingomonas sp. strain TTNP3. The effects of five successive inoculations of the membrane bioreactor with this strain able to degrade NP were investigated in comparison to a non-bioaugmented reactor. Results showed that the radioactivity spiked in the bioaugmented system was retrieved mostly in the effluent (56%), followed by fractions sorbed to the system (25%), associated with the excess sludge (9%) and collected from the gas phase as CO2 resulting from mineralization (2.3%). The degradation products identified in the treated effluent and in the MLSS were specific metabolites of catabolism of the NP by Sphingomonas, e.g. hydroquinone resulting from ipso-substitution. The capacity of this bacterium to excrete biosurfactants and to increase nonylphenol bioavailability was investigated. The presence and persistence of the strain in the membrane bioreactor was examined by performing polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE).
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2007
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Cirja, Magdalena
- Contributors dc:contributor
-
- Schäffer, Andreas
Subjects
dc:subject × 6Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- eng