This research investigates a novel approach to methanol production from methane. The high use of fossil fuels in New Zealand and around the world causes global warming. Using clearer, renewable fuels the problem could potentially be reduced. Biomass energy is energy stored in organic matter such as plants and animals and is one of the options for a cleaner, renewable energy source. A common biofuel is methane that is produced by anaerobic digestion. Although methane is a good fuel, the energy is more accessible if it is converted to methanol. While technology exists to produce methanol from methane, these processes are thermo-chemical and require large scale production to be economic. Nitrosomonas europaea, a nitrifying bacterium, has been shown to oxidize methane to methanol (Hyman and Wood 1983). This research investigates the possibility of converting methane into methanol using immobilized N. europaea for use in smaller applications. A trickle bed bioreactor was developed, containing a pure culture of N. europaea immobilized in a biofilm on ceramic raschig rings. The reactor had a biomass concentration of 7.82 ± 0.43 g VSS/l. This was between 4 – 15 times higher than other systems aimed at biologically producing methanol. However, the immobilization dramatically affected the methanol production ability of the cells. Methanol was shown to be produced by the immobilized cells with a maximum production activity of 0.12 ± 0.08 mmol/gVSS.hr. This activity was much lower than the typical reported value of 1.0 mmol/g dry weight.hr (Hyman and Wood 1983). The maximum methanol concentration achieved in this system was 0.129 ± 0.102 mM, significantly lower than previous reported values, ranging between 0.6 mM and 2 mM (Chapman, Gostomski, and Thiele 2004). The results also showed that the addition of methane had an effect on the energy gaining metabolism (ammonia oxidation) of the bacteria, reducing the ammonia oxidation capacity by up to 70%. It was concluded, because of the low methanol production activity and the low methanol concentrations produced, that this system was not suitable for a methanol biosynthesis process.

Naphthenic acids (NAs) comprise a complex mixture of alkyl-substituted acyclic and cycloaliphatic carboxylic acids. NAs are present in wastewaters at petroleum refineries and in the process waters of oil sands extraction plants where they are primarily retained in large tailing ponds in the Athabasca region of Northern Alberta. The toxicity of these waters, primarily caused by NAs, dictates the need for their treatment.Bioremediation is considered as one of the most cost-effective approaches for the treatment of these wastewaters. Ex-situ bioremediation conducted in a bioreactor optimizes the microbial growth and activity by controlling environmental conditions resulting in efficient conversion of the contaminants to less harmful compounds. In this work, a circulating packed bed bioreactor (CPBB), with improved mixing, mass transfer and biomass hold-up has been used to study biodegradation of several model NA compounds: namely trans-4-methyl-1-cyclohexane carboxylic acid (trans-4MCHCA), a mixture of cis- and trans- 4-methyl-cyclohexane acetic acid (4MCHAA), and octanoic acid as well co-biodegradation of these naphthenic acids with octanoic acid, using a mixed culture developed in our laboratory. The biodegradation rates achieved for trans-4MCHCA in the CPBB are far greater than those reported previously in the literatures. The maximum biodegradation rate of trans-4MCHCA observed during batch operation was 43.5 mg/L-h, while a rate of 209 mg/L-h was achieved during continuous operation. Although cis-4MCHAA is more resistant to biodegradation when compared with trans-4MCHCA, the experimental results obtained from this study indicated both isomers were effectively biodegraded in the CPBB, with the maximum biodegradation rates being as high as 2.25 mg/L-h (cis-4MCHAA) and 4.17 mg/L-h (trans-4MCHAA) during batch operations and 4.17 mg/L-h(cis-4MCHAA) and 7.80 mg/L-h (trans-4MCHAA) during the continuous operation. Optimum temperature for biodegradation of 4MCHAA was determined as 25 aC. Furthermore, the biodegradation rate of single ring NAs (trans-4MCHCA and 4MCHAA) were found to be significantly improved through utilization of octanoic acid as a co-substrate. For example, the maximum biodegradation rate of trans-4MCHCA obtained during batch operation with the presence of octanoic acid was 112 mg/L-h, which was 2.6 times faster than the maximum value of 43.5 mg/L-h when trans-4MCHCA was used as a sole substrate. Similarly, the highest biodegradation rates of cis-4MCHAA and trans-4MCHAA were 16.7 and 28.4 mg/L-h in the presence of octanoic acid, which were 7.4 and 6.8 times higher than the maximum rates of 2.25 and 4.17 mg/L-h in the absence of octanoic acid.

Naphthenic acids (NAs) comprise a complex mixture of alkyl-substituted acyclic and cycloaliphatic carboxylic acids. NAs are present in wastewaters at petroleum refineries and in the process waters of oil sands extraction plants where they are primarily retained in large tailing ponds in the Athabasca region of Northern Alberta. The toxicity of these waters, primarily caused by NAs, dictates the need for their treatment.Bioremediation is considered as one of the most cost-effective approaches for the treatment of these wastewaters. Ex-situ bioremediation conducted in a bioreactor optimizes the microbial growth and activity by controlling environmental conditions resulting in efficient conversion of the contaminants to less harmful compounds. In this work, a circulating packed bed bioreactor (CPBB), with improved mixing, mass transfer and biomass hold-up has been used to study biodegradation of several model NA compounds: namely trans-4-methyl-1-cyclohexane carboxylic acid (trans-4MCHCA), a mixture of cis- and trans- 4-methyl-cyclohexane acetic acid (4MCHAA), and octanoic acid as well co-biodegradation of these naphthenic acids with octanoic acid, using a mixed culture developed in our laboratory. The biodegradation rates achieved for trans-4MCHCA in the CPBB are far greater than those reported previously in the literatures. The maximum biodegradation rate of trans-4MCHCA observed during batch operation was 43.5 mg/L-h, while a rate of 209 mg/L-h was achieved during continuous operation. Although cis-4MCHAA is more resistant to biodegradation when compared with trans-4MCHCA, the experimental results obtained from this study indicated both isomers were effectively biodegraded in the CPBB, with the maximum biodegradation rates being as high as 2.25 mg/L-h (cis-4MCHAA) and 4.17 mg/L-h (trans-4MCHAA) during batch operations and 4.17 mg/L-h(cis-4MCHAA) and 7.80 mg/L-h (trans-4MCHAA) during the continuous operation. Optimum temperature for biodegradation of 4MCHAA was determined as 25 aC. Furthermore, the biodegradation rate of single ring NAs (trans-4MCHCA and 4MCHAA) were found to be significantly improved through utilization of octanoic acid as a co-substrate. For example, the maximum biodegradation rate of trans-4MCHCA obtained during batch operation with the presence of octanoic acid was 112 mg/L-h, which was 2.6 times faster than the maximum value of 43.5 mg/L-h when trans-4MCHCA was used as a sole substrate. Similarly, the highest biodegradation rates of cis-4MCHAA and trans-4MCHAA were 16.7 and 28.4 mg/L-h in the presence of octanoic acid, which were 7.4 and 6.8 times higher than the maximum rates of 2.25 and 4.17 mg/L-h in the absence of octanoic acid.

Beaucoup de micropolluants organiques sont présents dans les boues. Leur possible impact sur l'environnement contribue à accroître leur intérêt scientifique et social. La digestion anaérobie présente un potentiel certain pour dégrader ces composés. Dans ce travail, il a été développé un modèle dynamique pour décrire le devenir de micropolluants hydrophobes au cours de la digestion anaérobie de boues contaminées. Le modèle est basé sur une distribution des composés dans quatre-compartiments et il a démontré que la transformation des micropolluants est bien simulée si l'on considère une cinétique de co-métabolisme pour la dégradation et si la phase aqueuse constitue le compartiment biodisponible. Dans ce modèle, la sorption des micropolluants hydrophobes est envisagée sur deux phases différentes: la matière particulaire et la matière dissoute/colloïdale (DCM), car la sorption sur le compartiment DCM peut influencer la disponibilité des composés et donc leur biodégradation. Il a été conclu que le transfert de micropolluants hydrophobe ne limite pas leur biodégradation, et que leur devenir est régi par l'état d'équilibre de sorption-désorption. Afin d'identifier quelle(s) étape(s) de la digestion permet le co-métabolisme, de nouvelles expérimentations ont été menées en utilisant des inhibiteurs des Méthanogènes. Elles suggèrent que la dégradation anaérobie des micropolluants implique principalement des microorganismes non-méthanogènes. En effet, la transformation co-métabolique des micropolluants serait principalement liée à la population acidogènes, comme le montre le modèle avancé proposé. Le modèle proposé est potentiellement utile pour mieux comprendre la distribution des micropolluants, prédire leur devenir dans des conditions anaérobies et aider à optimiser le processus de fonctionnement pour leur épuisement. / Many organic micropollutants are present in sludge. Their possible impact on the environment contributes to their increasing scientific and social interest. Anaerobic digestion has been shown as a potential biological process for removing these compounds. In this work, a dynamical fate model is developed for hydrophobic micropollutant under anaerobic digestion of contaminated sludge. The model is based on a four-compartment distribution and demonstrated that the micropollutant transformation is well simulated if considering a co-metabolic kinetic and the aqueous phase as the bioavailable compartment. In this model, the sorption of hydrophobic micropollutants is considered on two different phases: particulate matter and dissolved/colloidal matter (DCM). Indeed, the sorption onto DCM can influence the availability of compounds for biodegradation. It was concluded that hydrophobic micropollutant transfer does not limit their biodegradation, and that their fate is governed by sorption-desorption equilibrium state. In order to evaluate which step of the anaerobic pathway is implied in the co-metabolism of micropollutants, experimental set-ups were designed using different way to inhibit the Methanogens. The experimental inhibition of methanogenic activity suggests that the anaerobic degradation of micropollutants mainly involves non-methanogenic microorganisms. Indeed, the co-metabolic transformation of micropollutants would be mainly linked to acidogens population as it was shown through the proposed advanced model. This latter is potentially useful to better understand the micropollutant distribution, predict their fate under anaerobic condition and help to optimize the operation process for their depletion.