RT info:eu-repo/semantics/doctoralThesis
T1 Studying  bioavailability limitations in processes that involve gaseous phases
A1 Kraakman, Norbertus Joannes Richardus
A2 Universidad de Valladolid. Escuela de Doctorado
K1 Biodisponibilidad - Medio ambiente
K1 Bioavailability
K1 Biodisponibilidad
K1 Gas purification
K1 Purificación de gases
K1 Hydrophobic VOCs
K1 COV hidrofóbicos
K1 Taylor flow
K1 Flujo de Taylor
K1 23 Química
AB This PhD thesis obtained a better understanding of bioavailability limitations of especially hydrophobic contaminants at relatively low concentrations in gas treatment bioprocesses. More specifically, methods to enhance the bioavailability of (1) gaseous hydrophobic contaminants in the context of indoor air quality (IAQ) and (2) dilute methane to reduce greenhouse gas (GHG) emissions have been investigated from an experimental and theoretical point of view.Several long-term experimental studies were undertaken to investigate constraints of bioavailability and possible design and operational strategies to overcome them. First the treatment in a capillary reactor of gaseous compounds that are model compounds for hydrophobic indoor air contaminants was evaluated (Chapter 5). This process was further investigated through the addition of a second non-aqueous liquid phase with a high affinity for these contaminants (Chapter 6) and through the co-abatement of gaseous contaminants and CO2 (Chapter 7). The abatement of dilute methane using the concept of a capillary bioreactor was investigated with the focus on liquid optimisation (Chapter 8) and reactor operation (Chapter 9). Overall, bioavailability limitations related to biological gas treatment have been investigated in general terms, with an emphasis on the underlying principles and technically feasible methods to overcome bioavailability limitations of especially hydrophobic contaminants in a capillary bioreactor. The removal efficiency of the model air contaminants hexane, toluene and α-pinene (selected based on their different hydrophobicity and biodegradability) was on average 58, 90 and 44%, with maximum removals of up to 75, 99 and 75%, respectively, at an average gas contact time in the capillary channels of less than 1 second. The toluene, α-pinene and hexane removals were further enhanced up to 99, 98, and 55%, respectively, when 10% (v/v) silicone oil with a viscosity of 20 cSt was dispersed in the recirculating liquid. The addition of silicone oil increased the removal efficiency of α-pinene from 45 ± 6% to 98 ± 2% over two days, likely due to the fact that silicone oil alleviated biokinetic inhibition by acting as a buffer for this compound and their metabolites. For toluene, the removal efficiencies gradually increased after silicone oil addition from 81 ± 3% to 99 ± 1% over eight weeks, likely due to microbial adaptation. Interestingly, visually all the biomass adhered to the silicone oil phase rather than residing in the water phase. Furthermore, different bench experiments elucidated that the liquid phase in a capillary bioreactor can be optimized to enhance the bioavailability of dilute methane. When the removal of gaseous methane was investigated in different capillary bioreactor configurations, the addition of only surfactant or only silicone oil did not show any enhancement in methane removal. The capillary bioreactor containing silicone oil and the surfactant BRIJ 58 treating dilute methane performed best with an average elimination capacity of 231 ± 30 g methane per m3 internal capillary channel per hour at an efficiency of 51 ± 2% and an empty channel gas contact time of 23 seconds. This is a large improvement compared to conventional biological methane treatment methods. Moreover, the potential of silicone oil as a buffer for methane was confirmed in a test that showed no deterioration in methane removal in the capillary bioreactor following the methane supply interruption of six days. No accumulation of biomass on the walls of the capillary glass channels was observed during the entire period of more than 300-days operation of the capillary bioreactor. It appears that a capillary bioreactor, when operated with internal gas recirculation and thus decoupling optimal conditions for mass transfer from the gas contact time, may be a useful platform for further exploring the abatement of dilute methane.
YR 2025
FD 2025
LK https://uvadoc.uva.es/handle/10324/76135
UL https://uvadoc.uva.es/handle/10324/76135
LA eng
NO Escuela de Doctorado
DS UVaDOC
RD 08-jul-2025