This thesis evaluates the performance of a deammonification system designed as a two-step tech-nology consisting of an initial partial nitritation followed by an Anammox process. Operation of a technical-scale pilot plant at the Himmerfjärden Wastewater Treatment Plant (Grödinge, Swe-den) has been assessed. Oxygen Uptake Rate (OUR) to evaluate the respiration activity of nitrifi-ers in the system and batch tests to assess reaction rates have also been applied in the study. It was found that the total inorganic nitrogen elimination strongly depended on the nitrite-to-ammonium ratio in the influent to the Anammox reactor, which was correlated with the per-formance of the partial nitritation phase. Therefore, a control strategy for oxidation of ammo-nium to nitrite has been proposed. Controlled oxygen supply to the partial nitritation reactor is obligatory to obtain a proper pH drop indicating oxidation of ammonia to nitrite at the adequate ratio. A very high nitrogen removal efficiency (an average of 84%) and stable operation of the system have been reached. Conductivity measurements were also used to monitor the system influent nitrogen load and the nitrogen removal in the Anammox reactor. The data gathered from the operation of the pilot plant enabled the use of multivariate data analysis to model the process behaviour and the assessment of the covariances between the process parameters. The options for full-scale implementation of the Anammox systems have been proposed as a result of the study. / QC 20101115

Understanding how nitrifiers react when exposed to low DO conditions could provide a greater understanding of low DO operations in full-scale biological wastewater treatment. Previous methods to observe nitrifier oxygen kinetics do exist in literature, however they are inefficient and labor intensive. Other more efficient methods require the use of selective inhibitors, which alter the characteristics of the biomass. This study developed a time and labor efficient respirometric method to distinctly measure oxygen half-saturation coefficients for both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) without the use of selective inhibitors. By eliminating the use of inhibitory substances, representative biomass characteristics were maintained throughout the tests. The developed method, called the declining DO method, consisted of using a high-speed dissolved oxygen (DO) probe to measure relative oxygen uptake rates (OUR) within a batch reactor when varying substrates (ammonia and nitrite) were present in excess within the system. A forward model was developed based on Monod kinetics to simultaneously fit Monod curves to the experimental OUR data. These curves were fit by solving for optimum oxygen kinetic parameters representing endogenous respiration, NOB, and AOB. An inverse model using Markov chain Monte Carlo analysis was applied to the results found in the forward model to provide statistical validation of the proposed respirometric method. A separate method, called the substrate utilization rate test, was conducted in parallel with the declining DO tests to compare and verify oxygen half-saturation coefficient results. Parallel tests were conducted using biomass samples from three different Hampton Roads Sanitation District (HRSD) full-scale facilities. Operating conditions between the three HRSD facilities were considered when performing parallel testing, including averages for DO, solids retention time (SRT), and floc size. Average floc size was found to have a significant effect on the observed oxygen half-saturation values. Observed trends for the KO values estimated using the two methods remained consistent throughout all tests, where KO,NOB was always lower than KO,AOB. The comparison of the two methods highlighted some faults associated with the substrate utilization rate test, which is commonly used in literature to observe nitrifier oxygen kinetics. The declining DO method appeared to be more resistant to potential experimental error and required less than half the time compared to the substrate utilization rate test. The development of the declining DO method without the use of selective inhibitors provided a more time and labor efficient technique for estimating apparent KO values for NOB and AOB without sacrificing biomass characteristics representative of the full-scale treatment process. Biomass samples collected from variable treatment process conditions yielded consistent parallel test results, providing further evidence that the proposed declining DO method can be a robust and reliable technique for distinctly measuring apparent oxygen half-saturation values for NOB and AOB. / Master of Science / Wastewater treatment operations utilizing biological nitrogen removal (BNR) require a continuous supply of oxygen for aerobic processes. Energy costs associated with aeration generally accounts for at least 50% of the total energy consumption at conventional activated sludge wastewater treatment facilities. Operating aerobic zones at low average dissolved oxygen (DO) concentrations could be an effective way to significantly reduce aeration costs as well as material costs associated with BNR treatment processes. This study developed a method to measure oxygen kinetics for the two groups of autotrophic bacteria responsible for performing nitrogen removal. The method consisted of measuring relative oxygen uptake rates (OUR) within a batch reactor when varying substrates were available. This method is unique from previously developed techniques in that the use of selective inhibitors was not included, meaning the characteristics of the wastewater were largely unchanged and therefore better represent biomass conditions within the full-scale process. The results of the proposed method were verified using an alternate method for estimating oxygen kinetics. These two methods were conducted in parallel using biomass samples from several full-scale Hampton Roads Sanitation District wastewater treatment facilities utilizing a variety of process designs and operating conditions. Consistent results obtained between the two methods suggested the proposed method is an effective technique for distinctly measuring nitrifier oxygen kinetics.

The excessive use of fossil fuels, industrialization, and growing populations have increased environmental pollution, global warming, and global energy demands (Dimitriadis & Bezergianni, 2017). Due to these problems, a new alternative energy source must be used. Biomass conversion to liquid transportation fuels is a major category of renewable energy, with various waste biomasses as leading candidates (Dimitriadis & Bezergianni, 2017). Multiple thermo-chemical conversion (TCC) technologies exist to convert biomass into fuels with one of the most promising methods being hydrothermal liquefaction (HTL). The main benefit of HTL is that it does not require that the biomass be dried before processing which would be a fuel- and cost-intensive process (Grande et al., 2021; SundarRajan et al., 2021). However, HTL produces toxic solid, gaseous, and aqueous byproducts. The hydrothermal liquefaction aqueous-phase byproduct (HTL-AP) is thought to be the factor limiting commercial viability of the HTL process, particularly because some of the constituents have inhibitory effects on nitrifying bacteria (Macêdo et al., 2023). There are existing treatment technologies for HTL-AP such as anaerobic digestion, wet air oxidation (WAO), and more. The simplest treatment method at a wastewater treatment plant (WWTP) using HTL for sludge disposal would be to return the HTL-AP to the v headworks to be treated alongside standard wastewater flow (MBE, 2019). However, the inhibitory effects may cause the WWTP to not meet ammonia regulations, if relevant. In this project, four 3.5-L bench-scale aerated reactors were built to simulate conventional activated sludge wastewater treatment to develop methods to determine the long-term effects of HTL-AP on nitrification. Two reactors were controls fed only synthetic wastewater, and two reactors were fed synthetic wastewater with a small dilution of HTL-AP, called AP reactors. Two different doses of hydrothermal liquefaction aqueous phase (HTL-AP) were tested on long-operated activated sludge systems. A 275x dilution factor (DF) of HTL-AP was tested for 132 days and a 2750x DF was tested for 23 days. The weekly nitrogen data (total ammonia nitrogen, nitrate, and nitrite) suggested that both doses inhibited nitrification in the bench-scale activated sludge systems. Additionally, the nitrifying bacteria did not adapt over time to be able to nitrify the wastewater with HTL-AP. During the first experiment with a 275x DF, no nitrate was detected in the AP reactors (/L NO3 - -N) and nitrite was sparsely detected. The control reactors had low concentrations of nitrate of around 3-8 mg/L NO3 - -N and high concentrations of nitrite, typically around 10-40 mg/L NO2 - -N. Therefore, the AP reactors were performing minimal nitrification, if any, while the control reactors were primarily performing partial nitrification. Before implementing the 2750x DF of HTL-AP, all reactors were emptied, cleaned, and restarted with nitrifying mixed liquor from the San Luis Obispo Water Resource Recovery Facility membrane bioreactor (SLO WRRF MBR). By the end of the 23 days of HTL-AP exposure at a 2750x DF, the treatment reactors had a sharper nitrate decline with final NO3 - -N concentrations around 1 mg/L compared to about 5-7 mg/L vi NO3 - -N in the control reactors. At this time, nitrite concentrations were not considerable in any reactor. Because nitrification was not ideal even in the control reactors, future work is advised, including stabilizing the solids retention time and changing the synthetic wastewater formula to support higher concentrations of treatment bacteria. Some methods for the specific oxygen uptake rate (SOUR) test that are not explicitly or extensively outlined in ISO 8192 (ISO, 2007) were examined. First, a 10- minute trial duration was deemed sufficient compared to 20 minutes (R 2>0.99 in either case and Preliminary SOUR tests using the correct methods found that raw HTL-AP doses of 50x, 125x, and 250x dilution factors (DF’s) inhibited nitrification by about 80 to 105% in nitrifying sludge from the SLO WRRF MBR. Raw HTL-AP doses of 500x and 1000x DF’s did not inhibit nitrification respiration rates. From a SOUR test on this same sludge but on a different day, HTL-AP pretreated by wet air oxidation (WAO) had near-zero vii (neg. 0.9%) inhibition on nitrification respiration rates at a 250x DF compared to the 66% nitrification inhibition found in raw HTL-AP at this 250x DF on this testing date.

<p>This thesis evaluates the performance of a deammonification system designed as a two-step tech-nology consisting of an initial partial nitritation followed by an Anammox process. Operation of a technical-scale pilot plant at the Himmerfjärden Wastewater Treatment Plant (Grödinge, Swe-den) has been assessed. Oxygen Uptake Rate (OUR) to evaluate the respiration activity of nitrifi-ers in the system and batch tests to assess reaction rates have also been applied in the study. It was found that the total inorganic nitrogen elimination strongly depended on the nitrite-to-ammonium ratio in the influent to the Anammox reactor, which was correlated with the per-formance of the partial nitritation phase. Therefore, a control strategy for oxidation of ammo-nium to nitrite has been proposed. Controlled oxygen supply to the partial nitritation reactor is obligatory to obtain a proper pH drop indicating oxidation of ammonia to nitrite at the adequate ratio. A very high nitrogen removal efficiency (an average of 84%) and stable operation of the system have been reached. Conductivity measurements were also used to monitor the system influent nitrogen load and the nitrogen removal in the Anammox reactor. The data gathered from the operation of the pilot plant enabled the use of multivariate data analysis to model the process behaviour and the assessment of the covariances between the process parameters. The options for full-scale implementation of the Anammox systems have been proposed as a result of the study.</p>

<p>This master thesis in energy optimization was made during the autumn of 2006 at Käppala wastewater treatment plant in Lidingö, Stockholm. A preceding thesis, where all electricity consumption was mapped, showed that the aeration in the biological treatment is the single largest consumer in the plant, and it is therefore of interest to reduce this cost. The oxygen control strategy used at Käppala WWTP is working well from a nutrient removal point of view, but not from an economic one. The last aerobic zones have a very low oxygen consumption during low loading periods which give rise to enhanced dissolved oxygen concentrations with excessive costs and reduced denitrification as a result. But also during periods of normal loading unnecessary high oxygen concentration are sometimes given.</p><p>By modifying the aeration control strategy three full-scale experiments have been made, with the intention to reduce the air consumption. The experiments were carried out during week 37-50 in the autumn of 2006 and showed that savings could be made.</p><p>The regular oxygen control at Käppala WWTP controls the oxygen level in the aerobic compartment with two DO-setpoints; one in the first aerobic zone and one in the last. The zones in between are controlled by an airflow fractionation depending on the oxygen level in the first and last zone. In the first strategy to be evaluated, all four zones in the aerated part were individually controlled with its own setpoint. Two different setpoint combinations were tested. By using the fact that the efficiency in the oxygen transfer rate was higher at low airflows, savings of approximately 16 % were achieved. In the second strategy tested, an ammonia-feedback control combined with a DO-feedback controlled the DO-set point in the first aerobic zone. This strategy adjusted the DO- set points to the loading variations, and this gave a decreased airflow of approximately 9 %. Finally the two strategies were combined. All zones were then controlled individually with DO-set points set by an ammonium-feedback and a DO-feedback. The strategy gave savings in the airflow of approximately 18 %. In all three trials the aerated zones were more efficiently used, and the estimated savings are 550 000 SEK/year, and with a preserved nutrient removal efficiency.</p> / <p>Under hösten 2006 har ett examensarbete om energieffektivisering på Käppalaverket på Lidingö utförts. Ett föregående examensarbete där all elenergiförbrukning kartlades visade att blåsmaskinerna i biosteget står för den enskilt största förbrukningen i verket och det är därför av intresse att minska denna kostnad. Syrestyrningsstrategin som används på Käppalaverket fungerar mycket bra ur reningssynpunkt, men är inte optimal ur energisynpunkt. Dels luftas de första aeroba zonerna för mycket vid låg belastning vilket ger upphov till kraftigt förhöjda syrekoncentrationer i de sista aeroba zonerna med höga luftningskostnader och risk för försämrad denitrifikation, men även under normal belastning har det visat sig att onödigt höga syrekoncentrationer ibland ges.</p><p>Tre fullskaliga optimeringsförsök har utförts, med syfte att minska luftförbrukningen med bibehållen reningsgrad. Försöken pågick från vecka 37 till 50 hösten 2006, och visade att det finns möjlighet att spara energi genom att modifiera syrestyrningsstrategin.</p><p>Den reguljära syreregleringen i Käppalaverket styr syrehalten i den aeroba bassängen mot två syrebörvärden; ett i den första luftade zonen och ett i den sista. Luftflödet till de mellanliggande zonerna styrs av luftflödesandelar beroende på syrehalten i dessa två zoner. Den första strategin som utvärderades styrde istället samtliga zoner individuellt med egna börvärden, där två olika strukturer på de satta börvärdena användes. Genom att utnyttja en högre effektivitet i syreöverföringshastigheten vid låga luftflöden uppnåddes luftflödesbesparingar på ca 16 % i första försöket.</p><p>I den andra strategin styrdes syrebörvärdet i den första luftade zonen med hjälp av två återkopplingar, en från utgående ammoniumhalt och en från syrehalten i den sista luftade zonen.</p><p>Tack vare att strategin anpassade syrebörvärdena efter belastningen av syretärande ämnen erhölls luftflödesbesparingar på ca 9 %. Slutligen kombinerades de två strategierna; samtliga zoner styrdes individuellt med börvärden satta av en ammonium-återkoppling och en syre-återkoppling. Strategin medförde luftflödesbesparingar på ca 18 %. I samtliga försök utnyttjades de luftade zonerna bättre, och besparingspotentialen uträknad från 2005 års elpriser blev som mest 550 000 SEK/år, detta med en bibehållen reningsgrad.</p>

Estudou-se nesta pesquisa o processo de lodos ativados para pós-tratamento do efluente proveniente de um reator anaeróbio compartimentado, que recebe esgoto sanitário. Isso se deu em vários ensaios em sistema descontínuo (\"batch\'\') para avaliar a biodegradabilidade dessa água residuária e em um ensaio em sistema contínuo com finalidade de melhorar a qualidade do efluente final e determinar os coeficientes cinéticos, os parâmetros a\' e b \', a taxa de utilização de oxigênio e o coeficiente &#945. Também realizaram-se ensaios hidrodinâmicos para verificação do tipo de reator utilizado. A pesquisa desenvolveu-se com base em uma célula de aeração, em escala de laboratório, composta por quatro câmaras (reatores) que possuíam tanque de aeração e decantador secundário justapostos, separados por uma cortina fixa. Não houve controle de temperatura nos dois sistemas utilizados. No ensaio em sistema contínuo quatro reatores foram operados simultaneamente com as respectivas idades do lodo de 5, 10, 15 e 20 dias durante 35 dias. O tempo de detenção hidráulico foi mantido próximo de 8 horas. Nesse ensaio os reatores quando se encontravam estabilizados dinamicamente, apresentaram remoção superior a 95% para DBO bruta, 90% para DBO filtrada, 87% para DQO bruta, 80% para DQO filtrada e 95% para SST. Mesmo não sendo realizado processo adicional para remoção de nutrientes, os reatores, após a estabilização dinâmica, apresentaram remoção de fosfato de até 28% e de nitrogênio amoniacal até níveis de não serem detectados pelos métodos de análises utilizados. Os ensaios hidrodinâmicos mostraram que os reatores são do tipo mistura completa. / In this work the activated sludge process for post-treatment of effluent anaerobic baffled reactor which receives sanitary sewage was studied. This was established during various experiments in batch system to evaluate the biodegradable of this wastewater and also in an experiment of continuous system aiming to improve the quality of the final effluent and to determine the kinetic coefficients, the a\' and b\' parameters, the oxygen uptake rate and the &#945 coefficient. Hydrodynamic tests to verify the type of reactor used in this research were also perfonned. The work was developed and based on an aeration cell bench-scale, composed of four chambers (reactors) which had an aeration tank and a secondary settling tank in the same chamber, separated by a fixed baffle. Temperature control was not used in both systems. In the experiment of continuous system, four reactors were simultaneously operated with sludge age of 5, 10, 15 and 20 days during 35 days. The hidraulic retention time was maintained at around 8 hours. When the reactors were dynamically stabilized, they showed an average removal superior to 95% for BOD (biochemical oxygen demand), 90% for filtrated BOD, 87% for COD (chemical oxygen demand), 80% for filtrated COD and 95% for TSS (total suspended solids). Without additional process of nutrient removal, after the dynamic stabilization the reactors presented up to 28% of total phosphate removal and ammonia nitrogen up to levels of not being detected by the analyses methods used. The hydrodynamic tests showed that the reactors are of the complete-mix type.

This master thesis in energy optimization was made during the autumn of 2006 at Käppala wastewater treatment plant in Lidingö, Stockholm. A preceding thesis, where all electricity consumption was mapped, showed that the aeration in the biological treatment is the single largest consumer in the plant, and it is therefore of interest to reduce this cost. The oxygen control strategy used at Käppala WWTP is working well from a nutrient removal point of view, but not from an economic one. The last aerobic zones have a very low oxygen consumption during low loading periods which give rise to enhanced dissolved oxygen concentrations with excessive costs and reduced denitrification as a result. But also during periods of normal loading unnecessary high oxygen concentration are sometimes given. By modifying the aeration control strategy three full-scale experiments have been made, with the intention to reduce the air consumption. The experiments were carried out during week 37-50 in the autumn of 2006 and showed that savings could be made. The regular oxygen control at Käppala WWTP controls the oxygen level in the aerobic compartment with two DO-setpoints; one in the first aerobic zone and one in the last. The zones in between are controlled by an airflow fractionation depending on the oxygen level in the first and last zone. In the first strategy to be evaluated, all four zones in the aerated part were individually controlled with its own setpoint. Two different setpoint combinations were tested. By using the fact that the efficiency in the oxygen transfer rate was higher at low airflows, savings of approximately 16 % were achieved. In the second strategy tested, an ammonia-feedback control combined with a DO-feedback controlled the DO-set point in the first aerobic zone. This strategy adjusted the DO- set points to the loading variations, and this gave a decreased airflow of approximately 9 %. Finally the two strategies were combined. All zones were then controlled individually with DO-set points set by an ammonium-feedback and a DO-feedback. The strategy gave savings in the airflow of approximately 18 %. In all three trials the aerated zones were more efficiently used, and the estimated savings are 550 000 SEK/year, and with a preserved nutrient removal efficiency. / Under hösten 2006 har ett examensarbete om energieffektivisering på Käppalaverket på Lidingö utförts. Ett föregående examensarbete där all elenergiförbrukning kartlades visade att blåsmaskinerna i biosteget står för den enskilt största förbrukningen i verket och det är därför av intresse att minska denna kostnad. Syrestyrningsstrategin som används på Käppalaverket fungerar mycket bra ur reningssynpunkt, men är inte optimal ur energisynpunkt. Dels luftas de första aeroba zonerna för mycket vid låg belastning vilket ger upphov till kraftigt förhöjda syrekoncentrationer i de sista aeroba zonerna med höga luftningskostnader och risk för försämrad denitrifikation, men även under normal belastning har det visat sig att onödigt höga syrekoncentrationer ibland ges. Tre fullskaliga optimeringsförsök har utförts, med syfte att minska luftförbrukningen med bibehållen reningsgrad. Försöken pågick från vecka 37 till 50 hösten 2006, och visade att det finns möjlighet att spara energi genom att modifiera syrestyrningsstrategin. Den reguljära syreregleringen i Käppalaverket styr syrehalten i den aeroba bassängen mot två syrebörvärden; ett i den första luftade zonen och ett i den sista. Luftflödet till de mellanliggande zonerna styrs av luftflödesandelar beroende på syrehalten i dessa två zoner. Den första strategin som utvärderades styrde istället samtliga zoner individuellt med egna börvärden, där två olika strukturer på de satta börvärdena användes. Genom att utnyttja en högre effektivitet i syreöverföringshastigheten vid låga luftflöden uppnåddes luftflödesbesparingar på ca 16 % i första försöket. I den andra strategin styrdes syrebörvärdet i den första luftade zonen med hjälp av två återkopplingar, en från utgående ammoniumhalt och en från syrehalten i den sista luftade zonen. Tack vare att strategin anpassade syrebörvärdena efter belastningen av syretärande ämnen erhölls luftflödesbesparingar på ca 9 %. Slutligen kombinerades de två strategierna; samtliga zoner styrdes individuellt med börvärden satta av en ammonium-återkoppling och en syre-återkoppling. Strategin medförde luftflödesbesparingar på ca 18 %. I samtliga försök utnyttjades de luftade zonerna bättre, och besparingspotentialen uträknad från 2005 års elpriser blev som mest 550 000 SEK/år, detta med en bibehållen reningsgrad.

Estudou-se nesta pesquisa o processo de lodos ativados para pós-tratamento do efluente proveniente de um reator anaeróbio compartimentado, que recebe esgoto sanitário. Isso se deu em vários ensaios em sistema descontínuo (\"batch\'\') para avaliar a biodegradabilidade dessa água residuária e em um ensaio em sistema contínuo com finalidade de melhorar a qualidade do efluente final e determinar os coeficientes cinéticos, os parâmetros a\' e b \', a taxa de utilização de oxigênio e o coeficiente &#945. Também realizaram-se ensaios hidrodinâmicos para verificação do tipo de reator utilizado. A pesquisa desenvolveu-se com base em uma célula de aeração, em escala de laboratório, composta por quatro câmaras (reatores) que possuíam tanque de aeração e decantador secundário justapostos, separados por uma cortina fixa. Não houve controle de temperatura nos dois sistemas utilizados. No ensaio em sistema contínuo quatro reatores foram operados simultaneamente com as respectivas idades do lodo de 5, 10, 15 e 20 dias durante 35 dias. O tempo de detenção hidráulico foi mantido próximo de 8 horas. Nesse ensaio os reatores quando se encontravam estabilizados dinamicamente, apresentaram remoção superior a 95% para DBO bruta, 90% para DBO filtrada, 87% para DQO bruta, 80% para DQO filtrada e 95% para SST. Mesmo não sendo realizado processo adicional para remoção de nutrientes, os reatores, após a estabilização dinâmica, apresentaram remoção de fosfato de até 28% e de nitrogênio amoniacal até níveis de não serem detectados pelos métodos de análises utilizados. Os ensaios hidrodinâmicos mostraram que os reatores são do tipo mistura completa. / In this work the activated sludge process for post-treatment of effluent anaerobic baffled reactor which receives sanitary sewage was studied. This was established during various experiments in batch system to evaluate the biodegradable of this wastewater and also in an experiment of continuous system aiming to improve the quality of the final effluent and to determine the kinetic coefficients, the a\' and b\' parameters, the oxygen uptake rate and the &#945 coefficient. Hydrodynamic tests to verify the type of reactor used in this research were also perfonned. The work was developed and based on an aeration cell bench-scale, composed of four chambers (reactors) which had an aeration tank and a secondary settling tank in the same chamber, separated by a fixed baffle. Temperature control was not used in both systems. In the experiment of continuous system, four reactors were simultaneously operated with sludge age of 5, 10, 15 and 20 days during 35 days. The hidraulic retention time was maintained at around 8 hours. When the reactors were dynamically stabilized, they showed an average removal superior to 95% for BOD (biochemical oxygen demand), 90% for filtrated BOD, 87% for COD (chemical oxygen demand), 80% for filtrated COD and 95% for TSS (total suspended solids). Without additional process of nutrient removal, after the dynamic stabilization the reactors presented up to 28% of total phosphate removal and ammonia nitrogen up to levels of not being detected by the analyses methods used. The hydrodynamic tests showed that the reactors are of the complete-mix type.

La bactérie hyperthermophile Thermotoga maritima a été cultivée dans un fermenteur dans lequel la concentration en O2 a été rigoureusement contrôlée. A 80°C et pH 7, il a été démontré que T. maritima pouvait survivre à des expositons de durées variables à l’O2 et qu’elle était capable de le consommer. La vitesse spécifique de consommation de l’O2 a été estimée à 73.6 µmoles O2.min-1.g protéines-1 lors d’une courte exposition à l’O2 (30 min). De longues expositions à l’O2 (20 h) nous ont permis de démontrer que la présence d’O2 ralentissait la croissance de T. maritima et conduisait à un shift du métabolisme vers la production de lactate aux dépens de l’acétate et à un arrêt de production d’H2. Dans ces conditions, il a été constaté que 73% du glucose était consommé selon un métabolisme partiellement oxydatif faisant intervenir simultanément les deux voies Embden-Meyerhof et Entner-Doudoroff de la glycolyse. En l’occurrence, l’oxydation incomplète du glucose est corrélée à la réduction de l’O2 en eau. Les études transcriptomiques ont montré que cette réduction de l’O2 résultait d’une cascade de réactions intermédiaires faisant intervenir des enzymes de type peroxydases [activation de l’expression des enzymes Ahp (alkyl hydroperoxyde réductase), Bcp1 et Bcp2 (thiol peroxydase thioredoxin-dépendante)] qui acheminent les électrons libérés via les radicaux libres. D’autres enzymes comme la rubréryhtrine et la neelarédoxine interviendraient pour détoxiquer les espèces réactives d’O2. Les électrons libérés seraient au final utilisés pour réduire l’O2 en H2O par l’enzyme FprA, dont l’expression varie en fonction du potentiel redox du milieu de culture. Ce schéma est proposé comme un des éléments essentiels du dispositif enzymatique permettant la consommation de l’O2 et la protection des cellules contre les effets des espèces réactives de l’oxygène chez T. maritima. / Batch cultures of the hyperthermophilic bacterium Thermotoga maritima were performed in a bioreactor where O2 concentrations in the gas phase were strictly controlled. At 80°C and pH 7, we demonstrated that T. maritima survived despite being exposed to oxygen at different times and that it consumed it. O2 uptake rate was estimated at 73.6 µmoles O2 min-1g proteins-1 during a short exposure to O2 (30 minutes). A long time exposure of T. maritima cultures to oxygen (20h) led to a drastic reduction in growth, together with a shift in glucose metabolism towards lactate instead of acetate production and a stop in H2 production. Under these conditions, it has been observed that 73% of glucose was partially oxidised by using both Embden-Meyerhof and Entner-Doudoroff glycolytic payhways. Uncomplete oxidation of glucose is correlated to a reduction of O2 to H2O. Transcription analyses revealed that this reductive process of O2 involved enzymes like peroxidases [activation of alkyl hydroperoxide reductase (ahp), bcp1 and thioredoxin-dependent thiol peroxidase (bcp 2)]. Moreover, genes encoding reactive oxygen species (ROS)-scavenging systems (neelaredoxin and rubrerythrin), were found to be upregulated during oxygen exposure. The oxygen reductase FprA, which expression was shown to depend on the redox level of the culture medium, is proposed as a primary consumer of O2. All these enzymes are essential for T. maritima to consume O2 consumption and to fight against the toxic effects of ROS in cells.

This master thesis is based on own studies. A four-month study was performed at Hammarby Sjostad Research Station, which is located in Stockholm. One-stage deammonification process was evaluated in two different system configurations in pilot plant scale. The theoretical background for this thesis works is presented in the first part and where is presented negative impacts of nitrogen compounds in environment and requirements for purified wastewater in European Union (Sweden and Poland). In the next part of the thesis the nitrogen cycle is described and with focus on biological reactions for nitrogen removal. Especially, nitrification/denitrification and anammox processes are described with special focus on parameters affecting the anammox process performance and its advantages and disadvantages of using this process. Experimental results from the four-month study and evaluation of the microbial activity are described in the last part.