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Partial denitrification/anammox (PdNA) is a biological nitrogen removal technology with significant carbon and aeration savings when compared with conventional nitrification/denitrification. Yet despite these benefits, the use of PdNA in mainstream wastewater treatment remains limited. One of the main barriers to implementation of anammox-based technologies is the slow growth rate of anammox (AMX), which results in a long startup time. To accelerate startup, the typical approach to commissioning AMX-based processes, specifically used for sidestream partial nitritation/AMX, is with biomass augmentation, which is practically unrealistic for full-scale mainstream applications. Thus, this study evaluated startup strategies for mainstream PdNA without AMX inoculation in moving bed biofilm reactors (MBBRs) with two simultaneous experiments. In one experiment, an MBBR was started using IFAS carriers with a preliminary biofilm and no external carbon dosing or AMX biomass inoculation. The feed was controlled to 20°C and included mainstream conditions of nitrite and ammonia controlled to the stoichiometric requirements for AMX growth. After only 84 days of operation, AMX activity was confirmed in the reactor with evidence of activity a few weeks before testing. In the second experiment, four reactors were started with either virgin carriers or integrated fixed-film activated sludge (IFAS) carriers with a preliminary biofilm of heterotrophs and nitrifiers. The reactors were fed mainstream levels of ammonia and nitrate with a temperature control target of 20°C and one reactor of each carrier type was dosed with carbon in the form of either glycerol or methanol. Carbon dosing was based on a feedback proportional-integrative-derivative (PID) control loop with a nitrate residual of 1-1.5 mgNO3-N/L. Of the four reactors, the preliminary biofilm carrier reactor dosed with glycerol achieved AMX activity first after 224 days of operation, but it was determined this was likely limited by synthetic feeding for the first 184 days. These results, along with other recent PdNA work, suggest that growth of AMX on biofilm carriers can be established in mainstream conditions in 50-100 days, depending on media selection and carbon source. Ultimately, this research will help utilities understand methods for starting up mainstream PdNA MBBRs from scratch and make this technology more accessible. / Master of Science / Intensification is the practice by which operational changes and new technologies are employed to reduce economic, resource, energy, and space requirements of wastewater treatment plants. One area of increasing focus involves the use of anaerobic ammonia oxidizing bacteria, or anammox (AMX), to reduce the aeration and carbon dosing needs for treating wastewater. One of the main barriers to implementation of AMX-based technologies is the slow growth rate of AMX, which results in a long startup time. To accelerate startup, the typical approach to commissioning AMX-based processes, specifically used for sidestream partial-nitritation/AMX, is with augmentation of biomass, which is practically unrealistic for full-scale mainstream applications. Thus, this study evaluated startup strategies for mainstream moving bed biofilm reactors (MBBRs) without AMX biomass inoculation in two simultaneous experiments in an AMX MBBR and a partial denitrification/AMX (PdNA) MBBR. In one experiment, idealized stoichiometric conditions for AMX growth were provided to a mainstream MBBR started with carriers from an aerobic integrated fixed-film activated sludge (IFAS) process to determine how fast AMX could potentially grow. In another experiment, different carrier types, virgin or preliminary biofilm carriers from an IFAS process, and different carbon sources, methanol and glycerol, were tested to determine the best methods for encouraging AMX attachment and growth in a PdNA process. These results, along with other recent PdNA work, suggest that growth of AMX on biofilm carriers can be established in mainstream conditions within 50-100 days, depending on media selection and carbon source. Ultimately, this research will help utilities understand methods for starting up mainstream PdNA MBBRs from scratch and make this technology more accessible.

The nitritation-anammox process is an efficient and cost-effective approach for biological nitrogen removal, but its application in treating mainstream wastewater remains a great challenge. The key objectives of this dissertation are to develop nitritation-anammox process to treat wastewater with low-nitrogen strength, understand the fundamental microbiology, and optimize its operation through experimental studies and mathematic modeling. Chapter 2 showed that the nitritation-anammox process has been successfully developed in an upflow membrane-aerated biofilm reactor, where pure oxygen was delivered via gas-permeable membrane module. Chapter 3 demonstrated that hybrid anaerobic reactor (HAR) could be an effective pretreatment method to provide a relatively low COD/N ratio for nitritation-anammox reactor. In Chapter 4, a novel mathematical model has been proposed to evaluate the minimum DO requirement for the nitritation-anammox reactor to achieve the maximum TN removal under various COD/N scenarios (controlled by HRTHAR). Chapters 5 and 6 designed an OsAMX system by linking nitritation-anammox to forward osmosis to remove the reverse-fluxed ammonium while using ammonium bicarbonate as a draw solute. The microbial community structures and dynamics, spatial distributions in these bioreactors were characterized by high-throughput sequencing and fluorescent in situ hybridization techniques. The studies in this dissertation have demonstrated that nitritation-anammox process is a promising alternative for sustainable mainstream treatment with the appropriate pretreatment approach and operation optimization. / PHD

<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>

There is an urgent need to develop ammonia removal treatment systems for municipal and industrial wastewater treatment due to the increasingly stringent ammonia effluent discharge regulations implemented by Canada, the United States, and the European Union. The objective of this dissertation is to develop new understanding and advance the current design and operation of total ammonia nitrogen (TAN) removal via the moving bed biofilm reactor technology (MBBR) for municipal and industrial wastewaters. The first specific objective is to develop a passive, low operationally intensive, efficient and robust design strategy for municipal wastewater treatment to achieve partial nitritation (PN) as a pre-treatment to anammox treatment without using control strategies such as operating at low dissolved oxygen, or the use of inhibitors. This first objective includes developing new knowledge of the biofilm, biomass and microbiome of attached growth PN systems. The second specific objective is to investigate the impact of defining a maximum biofilm thickness, via bio-carrier design, to enhance the effects of free nitrous acid inhibition for PN of municipal wastewaters. The third objective is to investigate the effect of influent copper concentration on nitrifying MBBR systems over long-term operations, to demonstrate the feasibility of the nitrifying MBBR as a solution for TAN removal from gold mining wastewaters. The results pertaining to the first objective, achieved via a study investigating the operation of a nitrifying moving bed biofilm reactor at elevated TAN surface area loading rates (SALRs) of 3, 4, 5, and 6.5 g TAN/m²∙d with the aim of achieving passive PN, demonstrates that operating at a TAN SALR value of 6.5 g TAN/m²∙d can achieve PN without restricting dissolved oxygen or using inhibitors. Operating at a TAN SALR value of 6.5 g TAN/m²∙d achieves a TAN surface area removal rate (SARR) of 3.5 g TAN/m²∙d, and a nitrite accumulation of 99.8% of the oxidized TAN, demonstrating the suppression of nitrite oxidizing bacteria (NOB) activity, while achieving elevated TAN SARR values. At the molecular-scale, there is a statistically significant change in the ammonia oxidizing bacteria (AOB) to NOB ratio from 1:2.6 to 8.7:1 as the TAN SALR increases from 3 to 6.5 g TAN/m²∙d; however, even at a TAN SALR value of 6.5 g TAN/m²∙d there is an NOB abundance of approximately 2%; thus demonstrating that NOB remain present in the biofilm, while their activity is suppressed by operation at elevated TAN SALR values. Furthermore, this system was shown to achieve stable PN consistently for over a period of 10 months of operation, demonstrating a robust, passive, low operational strategy for attached growth PN. The second objective of this dissertation is addressed through a study that compared the carrier design of defined maximal biofilm thickness (z-prototype carrier) to undefined maximal biofilm thickness (chip-prototype carrier) for PN via free nitrous acid inhibition of tertiary, low carbon, municipal wastewaters. The study demonstrates that defined maximal biofilm thickness is a preferred design choice to achieve attached growth PN. The chip-prototype carrier shows biofilm thicknesses and biofilm mass values that are ten-fold higher than the z-prototype carrier, which is shown to contribute to the impact of free nitrous acid on AOB and NOB activities. The z-prototype carrier shows PN is achieved after 3 hours of exposure to free nitrous acid while the chip-prototype carrier does not achieve PN within this same time of exposure. Therefore, the defined maximal biofilm thickness carrier is identified in this research as the preferred design option to achieve attached growth PN for municipal, low carbon, tertiary wastewater treatment. The results of the third objective, achieved via a study investigating the effects of influent copper concentrations on nitrifying MBBR during long term operations to gold mining wastewaters, demonstrates that there is no AOB inhibition in attached growth systems exposed to 0.1, 0.3, 0.45, and 0.6 mg Cu/L for long exposure times. A trend of increasing nitrite accumulation with increasing influent copper concentrations is shown, indicating that NOB inhibition occurs at influent copper concentrations of 0.3 mg Cu/L and greater, with the greatest NOB inhibition observed with an influent copper concentration of 0.6 mg/L. There is no statistically significant difference in biofilm characteristics at the copper concentrations tested; however, there is a trend of increasing biofilm thickness and biofilm roughness with increasing copper concentrations. This study demonstrates the resilience of the nitrifying biofilm to copper inhibition and demonstrates that the nitrifying MBBR is a promising system for removing TAN in mining wastewater in the presence of copper.

O objetivo do presente trabalho foi avaliar o desempenho de um reator de leito fixo e fluxo ascendente &#40;RLFFA&#41; em escala de bancada submetido à baixa aeração e recirculação. O reator foi utilizado como um sistema de pós-tratamento do efluente de indústria de fabricação de ração animal &#40;INCOFAP&#41; a partir de resíduos de abatedouro de aves, caracterizado por elevada carga de nitrogênio amoniacal. Para tanto, o RLFFA foi avaliado quanto à remoção da fração remanescente de matéria orgânica e de nitrogênio do efluente do reator UASB instalado na indústria. O RLFFA foi operado em condições mesofílicas &#40;30&#176;C&#41; e tinha volume total de 11,5 L e volume útil de 6,1 L, com leito estruturado composto por 13 estruturas cilíndricas &#40;3 cm de diâmetro&#41; de espuma de poliuretano, dispostas verticalmente no interior do reator. O reator apresentou sistema de recirculação interna, com razão de recirculação igual a 3, suficiente para garantir a mistura completa. O sistema foi operado em três condições distintas, que foram denominadas de fases, todas com tempo de detenção hidráulica &#40;TDH&#41; de 24 horas e concentração de oxigênio dissolvido próxima a 1,0 mg.L-1. Nas fases 1 e 2, o RLFFA foi alimentado com 20&#37; de efluente do UASB diluídos em água, e a alimentação da Fase 3 foi com 10&#37; de efluente. As relações DQO/N para as Fases de 1 a 3 foram de, respectivamente, 0,28, 0,41 e 0,26. Na Fase 1, a alcalinidade foi mantida em concentração estequiométrica para a ocorrência da nitrificação total, enquanto nas fases 2 e 3 a alcalinidade foi adicionada em excesso. As melhores eficiências de remoção de N-total e DQO foram obtidas na Fase 1, com respectivamente, 48 &#177; 24&#37; e 63 &#177; 20&#37;, atingindo remoção máxima de N-total de 79&#37; e 92&#37; para DQO. As análises estatísticas demonstraram independência entre a remoção de DQO e a remoção de N-total, e com demanda de doador de elétrons para desnitrificação heterotrófica via nitrato superior à DQO removida, indicando a ocorrência de vias complementares. A desnitrificação via nitrito e a desnitrificação autotrófica foram observadas nos ensaios cinéticos de desnitrificação via nitrito e teste de atividade para desnitrificação autotrófica utilizando sulfeto como doador de elétrons. A modelagem para qualidade da água do rio Chibarro&#40; local de lançamento do efluente da empresa INCOFAP&#41; utilizando uma modificação do modelo de Streeter-Phelps, indicou que o cenário com a adoção do reator estudado no presente trabalho para tratamento do efluente da INCOFAP permitiu reduzir o impacto para a qualidade da água do rio Chibarro ao se comparar ao sistema atual de tratamento do efluente da empresa INCOFAP. Entretando, ainda faz-se necessária a elevação da eficiência de remoção de N-total no sistema, para atingir a concentração máxima de N-amoniacal permitida de 20 mg.L-1 para o efluente para compatibilização com a capacidade de autodepuração do rio Chibarro. / The objective of this study was to evaluate the performance of a bench scale up-flow fixedbed reactor &#40;UFBR&#41; subjected to low aeration and effluent recirculation.The reactor was used as a post-treatment system of effluent from animal food plant &#40;INCOFAP&#41; using poultry slaughterhouse wastes, characterized by high ammoniacal nitrogen load rate.Therefore, the UFBR was evaluated in respect to residual organic matter and nitrogen removal of industrys UASB reactor effluent. The UFBR was operated in mesophilic conditions &#40;30&#176;C&#41; and it had a total volume of 11.5 L and a working volume of 6.1 L, with a structured bed composed by 13 polyurethane foam vertical cylindrical structures &#40;3 cm of diameter&#41; inside the reactor. The reactor was provided with internal recirculation system with recirculation ratio of 3, suficiente to guarantee a complete mixture. The system was operated in three different phases, with hydraulic retention time &#40;HRT&#41;of 24 hours and dissolved oxygen concentration close to 1.0 mg.L-1.On Phases 1 and 2, the UFBR was fed with 20&#37; of UASB effluent diluted in water,and the Phase 3 was fed with 10&#37; of effluent. On phases 1 to 3 COD/N ratios were, respectively, 0.28, 0.41 and 0.26. The alkalinity on Phase 1 was maintained on stoichiometric concentration to total nitrification, while in phases 2 and 3 excess alkalinity was added. The best total nitrogen and COD removal efficiencies were obtained in Phase 1, with respectively, 48 &#177; 24&#37; and 63 &#177; 20&#37; , reaching maximum total nitrogen removal of 79&#37; and 92&#37; for COD. Statistical analysis demonstrated independency between COD and total nitrogen removal, and with higher electron donor demand for nitrate denitrification than COD removal, indicating the occurrence of complementary paths. The nitrite denitrification and autotrophic denitrification were noted in kinetics experiments and activity tests for autotrophic denitrification using sulfide as source of electron donors. The modeling for Chibarro river water quality &#40;site of INCOFAPs effluent release&#41; , using a modified Streeter-Phelps model, indicated the scenario with the adoption of the studied reactor on this work for INCOFAP&#39;s effluent treatment provided the reduction of the impact on Chibarros water quality in comparison with the current effluent treatment of INCOFAP. However, it is still necessary an increase on system denitrification efficiency to reach the maximum ammoniacal nitrogen concentration allowed of 20 mg.L-1 for the effluent to make compatible with de selfpurification of Chibarro river.

Els lixiviats d'abocadors urbans són aigües residuals altament contaminades, que es caracteritzen per les elevades concentracions d'amoni i el baix contingut de matèria orgànica biodegradable. El tractament dels lixiviats a través dels processos de nitrificació-desnitrificació convencionals és costós a causa de la seva elevada demanda d'oxigen i la necessitat d'addició d'una font de carboni externa. En els darrers anys, la viabilitat del tractament d'aquest tipus d'afluents per un procés combinat de nitritació parcial-anammox ha estat demostrada. Aquesta tesi es centra en el tractament de lixiviats d'abocador a través d'un procés de nitritació parcial en SBR, com un pas preparatori per a un reactor anammox. Els resultats de l'estudi han demostrat la viabilitat d'aquesta tecnologia per al tractament de lixiviats d'abocador. El treball va evolucionar des d'una escala inicial de laboratori, on el procés va ser testat inicialment, a uns exitosos experiments d'operació a llarg termini a escala pilot. Finalment, la tesi també inclou el desenvolupament, calibració i validació d'un model matemàtic del procés, que té com a objectiu augmentar el coneixement del procés. / Urban landfill leachate are highly contaminated wastewater, usually characterised by high ammonium concentrations and low biodegradable organic matter content. Treating leachate through conventional nitrification-denitrification processes is expensive due to its high oxygen demand and the requirement of a supplementary external carbon source. In recent years, the feasibility of treating such streams with a low C:N ratio by a combined partial nitritation-anammox process has been demonstrated. This thesis deals with the treatment of landfill leachate by a partial nitritation-SBR, as a preparative step for an anammox reactor. The results of the study have demonstrated the feasibility of this technology for the treatment of landfill leachate. The work evolved from initial lab-scale studies, where the process was first tested, to a successful long-term experiment at pilot-scale. In addition, the thesis also includes the development, calibration and validation of a mathematical model of the process, aiming at increasing process knowledge.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-07T20:04:03Z No. of bitstreams: 1 TUILLY DE FÁTIMA MACEDO FURTADO GUERRA – DISSERTAÇÃO (PPGECA) 2016.pdf: 2570702 bytes, checksum: dc3123f0ac79b6573767e39e1c19c4c4 (MD5) / Made available in DSpace on 2018-08-07T20:04:03Z (GMT). No. of bitstreams: 1 TUILLY DE FÁTIMA MACEDO FURTADO GUERRA – DISSERTAÇÃO (PPGECA) 2016.pdf: 2570702 bytes, checksum: dc3123f0ac79b6573767e39e1c19c4c4 (MD5) Previous issue date: 2017-03-17 / Capes / O processo Anammox essencialmente é a desnitrificação autotrófica na qual nitrogênio amoniacal é oxidado por nitrito para nitrogênio molecular. O nitrito pode ser produzido em águas residuárias pela oxidação da amônia pelas Nitrosomonas. Todavia, tem-se que evitar que as bactérias do gênero Nitrobacter se desenvolvam para evitar a oxidação do nitrito para nitrato. O processo Anammox se aplica particularmente em águas ricas em amônia e pobres em material orgânico, como por exemplo, efluentes de digestores anaeróbios. Na prática tem sido aplicado com sucesso para efluentes de digestores de lodo aquecidos a 37 °C, mas a aplicação à temperatura ambiente na Europa (5 a 15 °C) não tem sido eficiente, pela dificuldade de eliminação da etapa de nitratação. Na presente pesquisa, procurou-se estabelecer se a nitrificação parcial é factível para a faixa de temperatura de esgotos no Brasil, para uma possível aplicação do processo Anammox visando à remoção de nitrogênio dos efluentes de reatores UASB. Para tanto, foram determinadas as constantes cinéticas da nitritação e nitratação em um sistema de lodo ativado entre a faixa de temperaturas de 12,7°C a 31 °C e as constantes de meia saturação do oxigênio dissolvido. A respirometria foi a ferramenta utilizada para determinar as taxas de nitritação e de nitratação e estimar as outras constantes cinéticas relevantes, sendo mostrado pelos resultados que esta é uma ferramenta útil na determinação das constantes cinéticas. Os valores encontrados das constantes cinéticas de crescimento das nitritadoras e nitratadoras em função da temperatura mostraram uma tendência de prevalecimento da nitritação sobre a nitratação em toda a faixa avaliada. Através da determinação da idade lodo mínima para a nitritação e nitratação pode-se estimar que operando um sistema de lodo ativado a temperatura ambiente adotando uma idade de lodo de 4 dias é possível promover a nitrificação parcial. / The Anammox process is essentially autotrophic denitrification in which ammoniacal nitrogen is oxidized by nitrite to molecular nitrogen. Nitrite can be produced in wastewater by the oxidation of ammonia by Nitrosomonas. However, it has to be avoided that bacteria of the genus Nitrobacter develop to avoid the oxidation of nitrite to nitrate. The Anammox process is applied particularly in ammonium rich waters and poor in organic material, such as effluent from anaerobic digesters. In practice it has been successfully applied to effluent from sludge digesters heated to 37 ° C, but application at room temperature in Europe (5 to 15 ° C) has not been efficient due to the difficulty of eliminating the nitration step. In the present research, it was tried to establish if the partial nitrification is feasible for the range of sewage temperature in Brazil, for a possible application of the Anammox process aiming at the removal of nitrogen from UASB reactor effluents. For this, the kinetic constants of nitriding and nitration were determined in an activated sludge system between the temperature range of 12.7 ° C to 31 ° C and the half-saturation constants of the dissolved oxygen. The respirometry was the tool used to determine nitration and nitration rates and to estimate the other relevant kinetic constants, and it is shown by the results that this is a useful tool in the determination of kinetic constants. The values of the kinetic constants of the nitriding and nitrating agents as a function of temperature showed a tendency of nitriding over nitration over the entire range. By determining the age minimum sludge for nitriding and nitration it can be estimated that operating a sludge activated system at room temperature adopting a sludge age of 4 days can promote partial nitrification.

Submitted by Neusa Fagundes (neusa.fagundes@unioeste.br) on 2017-09-06T13:24:19Z No. of bitstreams: 1 Adelcio_Giongo2016.pdf: 1383735 bytes, checksum: ddf849e35c040eb04a0c84af1eeb643f (MD5) / Made available in DSpace on 2017-09-06T13:24:19Z (GMT). No. of bitstreams: 1 Adelcio_Giongo2016.pdf: 1383735 bytes, checksum: ddf849e35c040eb04a0c84af1eeb643f (MD5) Previous issue date: 2017-07-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The swine industry has shown strong development and, thus, has produced large volumes of effluents that must be correctly managed. Therefore, when such effluent cannot be released into soil, a treatment must be carried out to avoid environmental impacts of swine wastewater. Nitrogen is one of the elements that takes part in swine waste and it must be under constant evaluation, but, in some cases, it must be removed. Nitrification/denitrification (NDF) process is a frequent applied technology. However, when the effluent presents low C/N ratio, such as effluents after anaerobic processes, there is some decrease on denitrification efficiency and the total nitrogen removal can be affected. In this case, Nitritation/denitritation (NDT) process can be used to improve the system performance as well as save energy cost with aeration and external source of carbon due to the lower C/N requirement. Thus, this study aimed at evaluating swine wastewater based on NDF and NDT processes at different C/N ratios in order to obtain a system with efficient nitrogen removal and low oxygen and carbon consumption. Four phases were carried out during this experiment: Phase I) DO from 2.0-3.0 mgO2L-1 to 1.5 C/N; Phase II) DO from 0.6-0.7 mgO2L-1 to 1.5 C/N; Phase III) DO from 0.6 to 0.7 mgO2L-1, different C/N ratios (1.5, 0.9, 0.75 and 0.6); Phase IV) DO from 2.0 to 3.0 mgO2L-1, different C/N ratios (1.5, 0.9, 0.75, and 0.6). The best operational condition was obtained at nitritation/denitritation process, whose C/N ratio was 0.9, and the optimum N removal was 86.3%. Under this condition, the system saved almost 36.8% of total organic carbon consumption and nearly 74% of dissolved oxygen consumed when compared to the conventional process for N-removal. This strategy can be very useful for nitrogen removal with low carbon rates, as the digestate from anaerobic processes. / A atividade suinocultura tem apresentado forte crescimento, e assim vem produzindo grandes volumes de efluentes que devem ser corretamente administrados. Portanto, quando não é possível a aplicação deste tipo de efluente no solo, o tratamento deve ser aplicado para que se evitem impactos ambientais. O nitrogênio é um dos elementos presentes nos dejetos de suínos que deve estar sob constante avaliação, e em alguns casos deve ser removido. O processo de nitrificação/desnitrificação (NDF) é uma tecnologia frequentemente aplicada, porém, quando o efluente apresenta baixa relação C/N, como efluentes pós-processos anaeróbios, a eficiência da desnitrificação é reduzida e a remoção de nitrogênio total pode ser afetada. Neste caso, o processo de nitritação/desnitritação (NDT) pode ser utilizado para melhorar o desempenho do sistema e economizar energia com aeração e com fonte externa de carbono, devido ao requisito de baixa relação C/N. Assim, o objetivo deste estudo foi avaliar a água residuária de suinocultura utilizando nitrificação/desnitrificação e nitritação/desnitritação em diferentes relações C/N, a fim de se obter um sistema com eficiente remoção de nitrogênio e baixo consumo de oxigênio e carbono. Quatro fases foram realizadas durante o experimento: Fase I) OD entre 2,0-3,0 mgO2 L-1 (nitrificação) e C/N 1,5; Fase II) OD entre 0,6-0,7 mgO2 L-1 (nitritação), e C/N 1,5; Fase III) OD entre 0,6-0,7 mgO2 L-1, diferentes relações C/N (1,5, 0,9, 0,75 e 0,6); Fase IV) OD entre 2,0-3,0 mgO2 L-1, diferentes relações de C/N (1,5, 0,9, 0,75 e 0,6). A melhor condição operacional foi encontrada no processo nitritação/desnitritação, com relação C/N de 0,9, cuja remoção de N considerada ótima foi de 86,3%. Nesta condição, a economia do sistema foi de 36,8% do consumo total de carbono orgânico e de cerca de 74% do consumo de oxigênio dissolvido, quando comparado com o processo convencional de remoção de N. Esta estratégia pode ser muito útil para a remoção do nitrogênio de efluentes de baixo teor de carbono, como os provenientes de processos anaeróbios.

O objetivo do presente trabalho foi avaliar o desempenho de um reator de leito fixo e fluxo ascendente &#40;RLFFA&#41; em escala de bancada submetido à baixa aeração e recirculação. O reator foi utilizado como um sistema de pós-tratamento do efluente de indústria de fabricação de ração animal &#40;INCOFAP&#41; a partir de resíduos de abatedouro de aves, caracterizado por elevada carga de nitrogênio amoniacal. Para tanto, o RLFFA foi avaliado quanto à remoção da fração remanescente de matéria orgânica e de nitrogênio do efluente do reator UASB instalado na indústria. O RLFFA foi operado em condições mesofílicas &#40;30&#176;C&#41; e tinha volume total de 11,5 L e volume útil de 6,1 L, com leito estruturado composto por 13 estruturas cilíndricas &#40;3 cm de diâmetro&#41; de espuma de poliuretano, dispostas verticalmente no interior do reator. O reator apresentou sistema de recirculação interna, com razão de recirculação igual a 3, suficiente para garantir a mistura completa. O sistema foi operado em três condições distintas, que foram denominadas de fases, todas com tempo de detenção hidráulica &#40;TDH&#41; de 24 horas e concentração de oxigênio dissolvido próxima a 1,0 mg.L-1. Nas fases 1 e 2, o RLFFA foi alimentado com 20&#37; de efluente do UASB diluídos em água, e a alimentação da Fase 3 foi com 10&#37; de efluente. As relações DQO/N para as Fases de 1 a 3 foram de, respectivamente, 0,28, 0,41 e 0,26. Na Fase 1, a alcalinidade foi mantida em concentração estequiométrica para a ocorrência da nitrificação total, enquanto nas fases 2 e 3 a alcalinidade foi adicionada em excesso. As melhores eficiências de remoção de N-total e DQO foram obtidas na Fase 1, com respectivamente, 48 &#177; 24&#37; e 63 &#177; 20&#37;, atingindo remoção máxima de N-total de 79&#37; e 92&#37; para DQO. As análises estatísticas demonstraram independência entre a remoção de DQO e a remoção de N-total, e com demanda de doador de elétrons para desnitrificação heterotrófica via nitrato superior à DQO removida, indicando a ocorrência de vias complementares. A desnitrificação via nitrito e a desnitrificação autotrófica foram observadas nos ensaios cinéticos de desnitrificação via nitrito e teste de atividade para desnitrificação autotrófica utilizando sulfeto como doador de elétrons. A modelagem para qualidade da água do rio Chibarro&#40; local de lançamento do efluente da empresa INCOFAP&#41; utilizando uma modificação do modelo de Streeter-Phelps, indicou que o cenário com a adoção do reator estudado no presente trabalho para tratamento do efluente da INCOFAP permitiu reduzir o impacto para a qualidade da água do rio Chibarro ao se comparar ao sistema atual de tratamento do efluente da empresa INCOFAP. Entretando, ainda faz-se necessária a elevação da eficiência de remoção de N-total no sistema, para atingir a concentração máxima de N-amoniacal permitida de 20 mg.L-1 para o efluente para compatibilização com a capacidade de autodepuração do rio Chibarro. / The objective of this study was to evaluate the performance of a bench scale up-flow fixedbed reactor &#40;UFBR&#41; subjected to low aeration and effluent recirculation.The reactor was used as a post-treatment system of effluent from animal food plant &#40;INCOFAP&#41; using poultry slaughterhouse wastes, characterized by high ammoniacal nitrogen load rate.Therefore, the UFBR was evaluated in respect to residual organic matter and nitrogen removal of industrys UASB reactor effluent. The UFBR was operated in mesophilic conditions &#40;30&#176;C&#41; and it had a total volume of 11.5 L and a working volume of 6.1 L, with a structured bed composed by 13 polyurethane foam vertical cylindrical structures &#40;3 cm of diameter&#41; inside the reactor. The reactor was provided with internal recirculation system with recirculation ratio of 3, suficiente to guarantee a complete mixture. The system was operated in three different phases, with hydraulic retention time &#40;HRT&#41;of 24 hours and dissolved oxygen concentration close to 1.0 mg.L-1.On Phases 1 and 2, the UFBR was fed with 20&#37; of UASB effluent diluted in water,and the Phase 3 was fed with 10&#37; of effluent. On phases 1 to 3 COD/N ratios were, respectively, 0.28, 0.41 and 0.26. The alkalinity on Phase 1 was maintained on stoichiometric concentration to total nitrification, while in phases 2 and 3 excess alkalinity was added. The best total nitrogen and COD removal efficiencies were obtained in Phase 1, with respectively, 48 &#177; 24&#37; and 63 &#177; 20&#37; , reaching maximum total nitrogen removal of 79&#37; and 92&#37; for COD. Statistical analysis demonstrated independency between COD and total nitrogen removal, and with higher electron donor demand for nitrate denitrification than COD removal, indicating the occurrence of complementary paths. The nitrite denitrification and autotrophic denitrification were noted in kinetics experiments and activity tests for autotrophic denitrification using sulfide as source of electron donors. The modeling for Chibarro river water quality &#40;site of INCOFAPs effluent release&#41; , using a modified Streeter-Phelps model, indicated the scenario with the adoption of the studied reactor on this work for INCOFAP&#39;s effluent treatment provided the reduction of the impact on Chibarros water quality in comparison with the current effluent treatment of INCOFAP. However, it is still necessary an increase on system denitrification efficiency to reach the maximum ammoniacal nitrogen concentration allowed of 20 mg.L-1 for the effluent to make compatible with de selfpurification of Chibarro river.