Αξιοποίηση αναερόβιων και βιο-ηλεκτροχημικών τεχνολογιών για επεξεργασία αποβλήτων και αναβάθμιση βιοαερίου

Kanellos, Gerasimos

dc.contributor.author	Kanellos, Gerasimos
dc.date.accessioned	2025-09-22T09:18:39Z
dc.date.available	2025-09-22T09:18:39Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/62487
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.30183
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/gr/	*
dc.subject	Επεξεργασία αποβλήτων	el
dc.subject	Wastewater treatment	en
dc.subject	Εφαρμογή δυναμικού	el
dc.subject	Applied potential	en
dc.subject	Μικροβιακό Ηλεκτρολυτικό κελί	el
dc.subject	Microbial electrolysis cell-assisted anaerobic digestion	en
dc.subject	Ηλεκτρομεθανοσύνθεση	el
dc.subject	Electromethanosynthesis	en
dc.subject	βιο-ηλεκτροχημικά συστήματα	el
dc.subject	Bio-electrochemical systems	en
dc.title	Αξιοποίηση αναερόβιων και βιο-ηλεκτροχημικών τεχνολογιών για επεξεργασία αποβλήτων και αναβάθμιση βιοαερίου	el
dc.contributor.department	Organic Chemical Technology	el
heal.type	doctoralThesis
heal.secondaryTitle	Utilization of anaerobic and bio-electrochemical technologies for waste valorization and biogas upgrading	en
heal.classification	Chemical Engineering	el
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2025-04-02
heal.abstract	Anaerobic digestion (AD) is a biochemical process in which microorganisms catalyze the conversion of chemical energy in organic compounds into biogas under anaerobic conditions. This technology is extensively utilized in wastewater treatment plants for its efficiency in treating organic waste. Despite the widespread propagation of AD for wastewater treatment, its efficiency remains constrained by several challenges. These include its limited efficacy in treating potent agro-industrial wastewaters, the inherently slow hydrolysis rate as the process's rate-limiting step, as well as the inability of the resulting biogas to be directly integrated into natural gas infrastructure due to suboptimal methane content and the presence of impurities. As a result, sustainable biological biogas upgrading technologies have attracted significant interest within the scientific community. In this context, bio-electrochemical systems, including microbial fuel cells (MFCs) and microbial electrolysis cells (MECs), are bioreactors that harness the chemical energy stored in organic compounds that act as electron donors, to generate electricity and methane, respectively, based on the electron acceptor employed and whether an external resistance or a power supply is employed. To address the limitations of AD, this thesis investigated anaerobic and bio-electrochemical technologies as advanced approaches for the enhanced treatment of organic and inorganic wastewaters, with a focus on promoting electromethanosynthesis and biogas upgrading, both as standalone processes and in integrated configurations. Initially, the co-digestion of organic wastes with complementary chemical compositions was studied, as a means of promoting increased biogas production and managing higher waste volumetric flow rates, through optimizing the feed carbon-to-nitrogen ratio. The anaerobic co-digestion of condensate, resulting from drying food waste, with Waste Activated Sludge (WAS) in a pilot scale continuous stirred tank reactor was assessed under multiple parameters: a) the condensate potency; b) the volumetric ratio of condensate to WAS; and c) the hydraulic retention time (HRT). The results showed that increasing the condensate content in the feed, enhanced the organic load removal and the bioenergy production. Moreover, the reduction of HRT enhanced the bioenergy production and did not significantly affect the reactor’s performance in terms of wastewater treatment efficacy. Overall it is concluded that the co-digestion of condensate and WAS can be safely applied in existing facilities for anaerobic digestion, while maintaining a more stable operation and improved effluent quality and bioenergy production in comparison with conventional anaerobic sludge digestion. Moreover, the capability of the MFC technology was investigated as an alternative method for valuable metal recovery from the inorganic chemical extract originating from end-of-life photovoltaic panels. The advantages of employing MFC technology lie in its ability to address inorganic waste treatment, a capability that AD technology lacks, while simultaneously treating organic wastewater and generating renewable electricity. The results indicated that silver was completely recovered from the chemical extract, albeit with a slower rate relative to synthetic wastewaters, which is attributed to the simultaneous reduction of other heavy metals in amorphous compounds, hindering the silver reduction kinetics and leading to a gradual electrode passivation. Nevertheless, silver can be 100% retrieved from the chemical extract, with an average purity of 86% w / w, in crystal (face center cube) structure, containing minor metal impurities. Furthermore, the MEC technology was evaluated for its capability to treat potent agro-industrial wastewaters while facilitating the bio-electrochemical conversion of CO2 to CH4. Specifically, the electromethanosynthesis process was studied with: a) synthetic wastewaters to unravel the electrochemical characteristics of the MEC; b) the secondary treatment of cheese whey effluent from dark fermentation; c) the primary treatment of two-phase olive mill wastewater (TPOMW); and d) the primary treatment of condensate, in order to optimize the operating conditions (organic loading,conductivity, treatment time, chemical composition and pretreatment of wastewaters, operation mode, applied potential and pH). Subsequently, a second MEC reactor was constructed in order to examine the impact of increased electrode specific surface area (1.25 m2 relative to 0.25 m2). Thereinafter, the MECs were modelled in the COMSOL Multiphysics® software. A non-linear dynamic model was developed, taking into account the extraction of the kinetic parameters in a 0D environment, aiming to the sensitivity analysis of the design and operational parameters in a 3D environment, in order to optimize the system based on the use of potentially improved configurations. The model was formulated to simulate the growth of six microbial populations, along with the impact that the cell overpotentials have on the Butler-Volmer-Monod kinetic rates and the current output based on Faraday’s law. The parameter estimation was followed by the sensitivity analyses of multiple parameters (the electrolyte conductivity, the electrode conductivity, active surface area, porosity and density, the electrolyte-to-electrode volume fractions, the Electrical Double Layer capacitance and the diffusion and convection of species in the electrolyte and electrode). The performed sensitivity analyses led to the identification of the key design parameters to promote the electromethanosynthesis pathways. Finally, the present thesis proposed an innovative single chamber MEC-AD reactor, which integrates the AD and MEC processes in order to achieve improved waste valorization and in-situ biogas upgrading. The integrated system was studied with: a) WAS; b) two-phase olive mill waste; and c) cheese whey, in order to optimize the operating conditions (organic loading rate-OLR, HRT, chemical composition and pretreatment of wastewaters and applied potential). For comparison, two identical reactors, a control (AD) and the MEC-AD reactor were constructed and operated. Overall, the results showed that the MEC-AD accelerated and enhanced the waste treatment, boosting the hydrolysis process and the methane productivity, whereas the AD process failed under stress. Subsequently, a second MEC-AD reactor was constructed in order to examine the impact of carbon veil as an alternative electrode material (specific surface area of 0.125 m2 and conductivity of 300 S / m), relative to the carbon felt (specific surface area of 0.25 m2 and conductivity of 370 S / m). Thereinafter, the MEC-AD with carbon felt electrodes was modelled using the AQUASIM software and the ADM1 mathematical framework. The aim was to derive a mathematical model for the study of the MEC-AD, which can be utilized to extract the effect of an applied potential on the kinetics of AD. The kinetic parameters extracted from the ADM1 showed that the MEC-AD yielded improved biomass yields, substrate consumption and 1st order disintegration rates, with a predominant contribution to disintegration of complex particulates. Moreover, the divergence from the AD increased as a function of the OLR, therefore accelerating waste treatment, as well as an improved performance at increased solids retention time (SRT). The ADM1 exhibited efficient adaptability and predictability of the kinetic processes and can be effectively used as a preliminary framework for the optimization of the MEC-AD operation.	en
heal.sponsor	The research work was supported by the Hellenic Foundation for Research and Innovation (HFRI) under the 3rd Call for HFRI PhD Fellowships (Fellowship Number: 5675).	en
heal.advisorName	Lyberatos, Gerasimos
heal.committeeMemberName	Lyberatos, Gerasimos
heal.committeeMemberName	Chronis, Nikolaos
heal.committeeMemberName	Polettini, Alessandra
heal.committeeMemberName	Pomi, Raffaella
heal.committeeMemberName	Vlysidis, Anestis
heal.committeeMemberName	Mamma, Diomi
heal.committeeMemberName	Vlysidis, Apostolos
heal.academicPublisher	Σχολή Χημικών Μηχανικών	el
heal.academicPublisherID	ntua
heal.numberOfPages	277
heal.fullTextAvailability	false