Σκοπός της διδακτορικής αυτής διατριβής ήταν η διερεύνηση και αποσαφήνιση του μηχανισμού έμφραξης των μεμβρανών στους βιοαντιδραστήρες ΜΒR και η διερεύνηση της δυνατότητας ελάττωσης της έμφραξης. Επιμέρους στόχοι ήταν η μελέτη της επίδρασης των διαλυτών μικροβιακών προϊόντων (SMP) και των εξωκυτταρικών πολυμερικών συστατικών (ΕPS) στην έμφραξη, καθώς επίσης και η διερεύνηση / αποσαφήνιση του μηχανισμού έμφραξης σε υδρόφιλες και υδρόφοβες μεμβράνες μικροδιήθησης σε συμβατικούς βιοαντιδραστήρες μεμβρανών (MBR). Η λειτουργία του MBR αξιολογήθηκε με τη διενέργεια φυσικοχημικών αναλύσεων της εισροής και εκροής, την ανάλυση των ιδιοτήτων της ενεργού ιλύος και τον χαρακτηρισμό των SMP και EPS ως προς τη συγκέντρωσή τους σε πρωτεΐνες και υδατάνθρακες. Παράλληλα, για τον προσδιορισμό των χαρακτηριστικών της ιλύος ή/και του διηθήματος χρησιμοποιήθηκαν τα αναλυτικά όργανα χρήσης δυναμικής σκέδασης φωτός (DLS), εφαρμογής σκέδασης φωτός (Mastersizer), χρωματογραφίας αποκλεισμού μεγεθών (SEC) και οπ ...
Όλα τα τεκμήρια στο ΕΑΔΔ προστατεύονται από πνευματικά δικαιώματα.
Περίληψη σε άλλη γλώσσα
The purpose of this doctoral dissertation was to investigate and elucidate the membrane fouling mechanism in membrane bioreactors (MBR) as well as to investigate the possibility of membrane fouling reduction. The particular objectives were to study in depth the effect of soluble microbial products (SMP) and extracellular polymeric substances (EPS) in the fouling process, and to investigate and clarify the fouling mechanism of hydrophilic and hydrophobic microfiltration membranes in conventional ΜΒRs. The evaluation of the ΜΒR system operation was carried out through inflow-outflow physico-chemical analysis, activated sludge characteristics study and SMP and EPS of mixed liquοr characterization, in the form of proteins and carbohydrates. In addition, several methods including dynamic light scattering (DLS), light scattering (Mastersizer), size exclusion chromatography (SEC) and optical microscopy were applied in order to determine sludge and/or filtrate characteristics. The experimental ...
The purpose of this doctoral dissertation was to investigate and elucidate the membrane fouling mechanism in membrane bioreactors (MBR) as well as to investigate the possibility of membrane fouling reduction. The particular objectives were to study in depth the effect of soluble microbial products (SMP) and extracellular polymeric substances (EPS) in the fouling process, and to investigate and clarify the fouling mechanism of hydrophilic and hydrophobic microfiltration membranes in conventional ΜΒRs. The evaluation of the ΜΒR system operation was carried out through inflow-outflow physico-chemical analysis, activated sludge characteristics study and SMP and EPS of mixed liquοr characterization, in the form of proteins and carbohydrates. In addition, several methods including dynamic light scattering (DLS), light scattering (Mastersizer), size exclusion chromatography (SEC) and optical microscopy were applied in order to determine sludge and/or filtrate characteristics. The experimental results revealed that a small part of SMP proteins and a higher rate of SMP carbohydrates is retained by the membrane. The SMP proteins and carbohydrates that are deposited within the membrane pores is found to be gradually aggregated resulting either in blockade of pores and increase of the trans-membrane pressure (TMP) or in detachment and excretion of unified aggregates with size equal or greater than the membrane pores. The rest of the retained SMP are rejected to the mixed liquor due to Donnan electrostatic repulsion by the deposited SMP, mainly caused by the negatively charged SMP carbohydrates, alike the Layer-by-Layer (LbL) mechanism that is applied in membranes in order to reduce membrane fouling. It was, also, concluded that the modified hydrophobic membrane exhibited anti-fouling properties during the first fouling phase compared to the non-modified hydrophilic membrane. However, the fouling process was subsequently developed similarly with the hydrophilic membrane. Aiming to resolve the membrane fouling problem, an innovative bioreactor set-up was created composed of two in-series aerobic bioreactors, which effectively reduces membrane fouling through the filamentous bacterial population adjustment. Specifically, the filamentous bacterial population is controlled in mixed liquor in low concentration, having filamentous index (FI) between 1 and 4, resulting in activated sludge of high porosity. Moreover, the SMP concentration is minimized, having as a result high reduction of irreversible membrane fouling. The final result of this innovative technology was the reduction of TMP within the range of 2 – 2.5 kPa for duration greater than three months, in contrast to the corresponding TMP of the conventional membrane bioreactor, where TMP gradually increased from 2.5 to 5 kPa in the first 25 days and reached 12 kPa after 43 days working time. Therefore, reversible and irreversible membrane fouling was successfully controlled through the proposed innovative filamentous MBR configuration.
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