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Effluent from a fish tank with Nile tilapia (Oreochromis niloticus) was treated in a system of two parallel fixed-bed anaerobic reactors followed by a suspended stirred, anoxic reactor for solids, organic matter and nitrogen removal. Microbial community structure was compared between the reactors and an enriched anammox culture originated from anaerobic sludge by using the PCR (Polymerase Chain Reaction) and DGGE (Denaturing Gradient Gel Electrophoresis) techniques. DGGE analysis revealed three large microbial clusters, namely, the biomass in the inoculum, the biomass growing in the reactors, and the enriched anammox culture. The similarity between the microbial community recovered from the anaerobic reactors and the anammox community was considered low (32.7%), suggesting differentiation of the bacterial community as a function of the selection of specific anammox groups. The last step in the anoxic reactor had worsened the effluent quality. The potential of organic matter and ammonia removal in a single anaerobic reactor was demonstrated. Resumo Efluentes de um tanque de peixes de cultivo de tilápia do Nilo (Oreochromis niloticus) foram tratados em um sistema de dois reatores anaeróbios de leito fixo paralelos e seguido por um reator agitado suspenso sob ambiente anóxico para remoção de sólidos, matéria orgânica e nitrogênio. A estrutura da comunidade microbiana foi comparada entre os reatores e uma cultura enriquecida de anammox originada de lodo anaeróbio por PCR (Reação em Cadeia de Polimerase) e DGGE (Eletroforese em Gel de Gradiente Desnaturante). A análise de DGGE revelou três grandes aglomerados microbianos, a saber, a biomassa do inóculo, a biomassa nos reatores e a cultura de anammox enriquecida. A similaridade entre a comunidade microbiana recuperada dos reatores anaeróbios e a comunidade anammox foi considerada baixa (32,7%), sugerindo diferenciação da comunidade bacteriana em função da seleção de grupos específicos de anammox. Embora o reator anóxico tenha piorado a qualidade do efluente, os resultados indicam o potencial de remoção de matéria orgânica e amônia em um único reator anaeróbio.

A comparison between a mixed aerobic-anoxic horizontal fixed-bed reactor (MAAFBR) and an aerobic horizontal fixed-bed reactor coupled with an anoxic vertical fixed-bed reactor (AHFBR-AVFBR) was made in order to evaluate the nitrogen removal behavior when nitrification and sulfide-driven autotrophic denitrification occurred in a single unit or spatially separated. Both systems achieved Total-N removal efficiencies (RE) higher than 89 %. Moreover, for both reactors, the effluent pH was affected for bicarbonate alkalinities lower than 250 mg CaCO3 L−1, decreasing the biogas desulfurization from 98 to 50 % in the MAAFBR and from 100 to 61 % in the AVFBR. Hydraulic retention times (HRTs) of 6, 8, 10 and 12 h did not affect the nitrification RE on the AHFBR, maintaining values higher than 99 %. In both cases, biogas desulfurization was achieved. However, results suggested that elemental sulfur (S0) was not predominantly formed due to the interference of oxygen. Such interference was more severe for the MAAFBR, in which the results implied diffusion of O2 and H2S between the aerobic and anoxic chambers.

The aim of this study was to investigate the post-treatment of UASB effluent by treating animal feed production wastewater using simultaneous partial nitrification, anammox and denitrification (SNAD) in a structured-bed reactor subjected to low aeration and recirculation. The average nitrogen loads applied were 0.307, 0.249 and 0.149 kgN m−3d−1, correlated to COD/N ratios of 0.28, 0.41 and 0.26 (Phases 1, 2 and 3, respectively). The best mean values for removal efficiencies of total-N and COD were obtained in Phase 1 with 48 ± 24% and 63 ± 20%, respectively, reaching a maximum total-N removal efficiency of 79%. The anammox process was the main pathway of nitrogen removal, as pointed out in the nitrogen mass balance. High free ammonia (FA) concentrations in Phases 2 and 3, associated to the limitation of oxygen supply, caused inhibition of nitrite oxidizing bacteria (NOB) activity, leading to NO2 accumulation, having an impact on the denitrifying activity. At the end of the operational period, sequencing analysis detected sequences related to heterotrophic denitrifiers (22.5%), anammox bacteria, Candidatus Anammoximicrobium (2%) and ammonia oxidizing bacteria (AOB) belonging to Nitrosomonadales and Nitrosomonas (0.6%). These results demonstrated that nitritation, denitrification and anammox were likely in the processes involved in nitrogen removal in this reactor.

A novel horizontal mixed anoxic-aerobic fixed-bed reactor configuration based on nitrification coupled with autotrophic denitrification using hydrogen sulfide as an electron donor was developed. The nitrification removal efficiency (RE) reached values greater than 99% but was slightly affected by the accumulation of dissolved sulfur species in the liquid phase. The denitrification RE reached 99% with a H2S inlet load of 28.6 g S m−3 h−1, although the use of aluminum polychloride (PAC) as a sulfur coagulant in the anoxic zone affected the buffering capacity of the system and resulted in a decrease in the RE. The performance of the reactor was primarily affected by the buffering capacity of the system, and this effect could be controlled with an increase in the NaHCO3 concentration. The recovery of biogenic elemental sulfur was possible using PAC as a coagulant, although the solid collected at the bottom of the settling tank contained only 1.5% S0.

Sparsely populated or peri-urban areas commonly lack access to public water supply and sewerage systems. The inhabitants must make use of excavated wells to meet their water needs and septic systems or pit latrines for domestic wastewater disposal, which can release pathogens and nutrients (nitrate and phosphate) into shallow groundwater. This study compares two on-site sanitation systems improved with permeable reactors for removal of nutrients and pathogens: a lateral flow design at Maryhill site (Canada) and a downflow design at Parelheiros site (Brazil). Both alternative latrines employed two reactive materials: BOF (Basic Oxygen Furnace) slag for pathogen removal and sawdust for nitrate removal. At Maryhill, the sawdust tank was emplaced before the BOF slag tank, and at Parelheiros, the BOF slag layer was emplaced before the sawdust layer. Maryhill latrine was able to oxidize up to 98% of ammonium to nitrate and to remove 99% of nitrate, phosphate, and E. coli from the effluent. Parelheiros latrine was more efficient in promoting nitrification, with almost complete ammonium oxidation, but nitrate removal by denitrification ranged between 13 and 57%, while phosphate and E. coli were completely removed. The BOF slag overlying sawdust layer in Parelheiros design may have negatively affected the performance in denitrifying bacteria due to the high pH created in BOF slag. The Maryhill latrine proved to be a more satisfactory design for nitrate removal. The combined use of sawdust and BOF slag in differing subsurface environments has shown considerable potential for mitigating impacts of on-site sanitation systems on groundwater.

Resumo O objetivo deste trabalho foi avaliar a dinâmica dos fluxos de óxido nitroso (N2O) em solo sob pastagem, em sistema de integração lavoura-pecuária, e sob cerrado nativo usado como referência, bem como identificar os atributos físicos e químicos do solo que influenciam esses fluxos. O estudo foi realizado na Fazenda Capivara, da Embrapa Arroz e Feijão, de 5 de fevereiro a 30 de setembro de 2013. As amostragens de gás foram realizadas com uso de câmaras estáticas manuais. O solo sob pastagem apresentou os maiores fluxos de N2O, com média de 14,12 ng m-2 s-1. Essa área também apresentou maior espaço poroso preenchido por água (EPPA), que, associado à temperatura e ao teor de nitrato no solo, influenciou a produção de N2O. Na época chuvosa, os fluxos apresentaram correlação positiva com o EPPA do solo e, na época seca, com seu teor de amônio e nitrato. A emissão total de N2O na área da pastagem foi de 1.644,19 gha1. No cerrado nativo, não houve emissão de N2O do solo para a atmosfera. Abstract The objective of this work was to evaluate the dynamics of nitrous oxide (N2O) fluxes in a soil under pasture, in an integrated crop-livestock system, and in native cerrado as a reference, besides identifying the physical and chemical soil properties that affect the fluxes. The study was conducted at Fazenda Capivara of Embrapa Arroz e Feijão, in the state of Goiás, Brazil, between February 5 and September 30, 2013. Gas sampling was performed using manual static chambers. The soil under pasture showed the highest N2O fluxes with average of 14.12 ng m-2 s-1. This area also showed greater water-filled pore space (WFPS), which, associated with soil temperature and nitrate content in the soil affected the production of N2O. In the rainy season, fluxes showed positive correlation with soil WFPS, and, in the dry season, they were correlated with soil contents of ammonium and nitrate. The total N2O emission in the pasture area was 1,644.19 g ha-1. In native cerrado, there was no soil-N2O emission to the atmosphere.

O nitrogênio é um dos contaminantes mais importantes presentes nas águas residuais. As alternativas tecnológicas mais usuais para o tratamento de águas contendo esse composto lançam mão do ciclo bioquímico do nitrogênio, o qual se sustenta em dois processos, a nitrificação e a desnitrificação. Dentre os parâmetros que influenciam na remoção de nitrogênio, podemos citar a concentração de oxigênio dissolvido, relação carbono/nitrogênio, temperatura, pH entre outros. Este trabalho apresenta uma revisão sobre a remoção biológica de nitrogênio das águas e os principais parâmetros que influenciam na sua remoção, dando ênfase ao processo de nitrificação e desnitrificação simultânea. Nitrogen is one of the most important contaminants present in wastewater. The most common alternative technologies for the treatment of waters containing this compound lay hold of the biochemical cycle of nitrogen, which is based on two processes, nitrification and denitrification. Among the parameters that influence the removal of nitrogen, we can mention the concentration of dissolved oxygen, carbon/nitrogen ratio, temperature, pH, and other relationships. This paper presents an overview of the biological nitrogen removal of water and the main parameters that influence the removal, emphasizing the simultaneous nitrification and denitrification process. Fil: Miranda Zoppas, Fernanda. Universidade Federal do Rio Grande do Sul; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentina Fil: Bernardes, Andrea Moura. Universidade Federal do Rio Grande do Sul; Brasil Fil: Meneguzzi, Álvaro. Universidade Federal do Rio Grande do Sul; Brasil

The present study evaluated the efficiency of a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) to promote nitrogen and carbon removal from domestic sewage. The intermittent aeration and the recycling rate of 3 keeps the desired mixing degree inside the SBRRIA. Four different operational conditions were tested by varying the hydraulic retention time (HRT) from 12 to 8 h and aerated and non-aerated periods (A/NA) from 2 h/1 h and 3 h/1 h. At the THD of 8 h and A/NA of 2 h/1 h there was a decrease in the nitrification process (77.5%) due to the increase of organic matter availability, affecting the total-N removal performance. However, by increasing the aerated period from 2 h to 3 h, the nitrification efficiency rose to 91.1%, reaching a total-N removal efficiency of 79%. The system reached a maximum total-N loading removed of 0.117 kgN.m−3.d−1 by applying an HRT of 8 h and an intermittent aeration cycle of 3 h, aerated and 1 h non-aerated. The simultaneous nitrification and denitrification (SND) process was related to a complex interplay among microorganisms affiliated mostly to Acidovorax sp., Comamonas sp., Dechloromonas sp., Hydrogenophaga sp., Mycobacterium sp., Rhodobacter sp., and Steroidobacter sp.

A rápida nitrificação do nitrogênio (N) amoniacal de fontes orgânicas e minerais no solo pode resultar em perdas de nitrato (NO3-) para o ambiente. Uma estratégia para a redução dessas perdas envolve o uso de inibidores de nitrificação. O objetivo do presente trabalho foi o de avaliar, em condições de laboratório, a eficiência da dicianodiamida (DCD), presente no produto Agrotain® Plus (AP), em inibir a nitrificação do N amoniacal de cama de aviário (CA) no solo. Foram avaliados cinco tratamentos, sendo um com CA incorporada ao solo, três com CA incorporada ao solo com AP, nas doses de 3,5, 7,0 e 14,0kg ha-1, além de um tratamento somente com solo. A nitrificação foi monitorada através da determinação periódica dos teores de NH4+ e NO3 no solo durante 69 dias. A maior taxa de nitrificação ocorreu no tratamento em que a CA foi incorporada ao solo sem AP. As doses de 3,5 e 7,0kg de AP ha-1 inibiram parcialmente a nitrificação do N amoniacal da CA na fase inicial da incubação, perdendo a eficiência em inibir esse processo no período entre 12 e 27 dias. O tratamento com a maior dose de AP (14kg ha-1) foi aquele em que a DCD exerceu maior efeito inibitório da nitrificação, preservando maior quantidade de NH4+ e retardando o aparecimento de NO3- no solo. Os resultados deste trabalho indicam que a DCD, contida no Agrotain® Plus, reduz a taxa de nitrificação do N amoniacal da CA no solo, o que poderá contribuir à redução das perdas de NO3- para o ambiente. The fast nitrification of ammoniacal nitrogen (N) of organic and mineral sources in soil can result in losses of nitrate (NO3-) to the environment. One strategy to reduce these losses involves the use of nitrification inhibitors. The objective of this study was to evaluate, in laboratory conditions, the efficiency of Agrotain® Plus (AP), which contains dicyandiamide (DCD), as a nitrification inhibitor of ammoniacal nitrogen from poultry manure (PM) in soil. Were evaluated five treatments, one with PM incorporated into the soil, three with PM incorporated into the soil with AP at the doses of 3.5, 7.0 e 14.0kg ha-1 and one treatment without PM and AP. Nitrification was monitored by measuring changes in soil mineral N (NH4+ and NO3-) periodically over 69 days. The highest rate of nitrification occurred in the treatment in which PM was incorporated into the soil without AP. The doses of 3.5 and 7.0kg ha-1 of AP inhibited partially the nitrification of ammoniacal nitrogen of PM in the initial phase of incubation, losing the ability to inhibit this process in the period between 12 and 27 days. The treatment with the higher dose of AP (14kg ha-1) was on in which the DCD exerted more inhibitory effect on nitrification, preserving most NH4+ and delaying the onset of NO3- in soil. The results of this study indicate that the DCD, contained in the Agrotain® Plus, reduces the nitrification rate of ammoniacal nitrogen from PM in soil, that may contribute to reduce NO3- losses to the environment.

Because benzene, toluene, ethylbenzene, and xylenes (BTEX) and ethanol are important contaminants present in Brazilian gasoline, it is essential to develop technology that can be used in the bioremediation of gasoline-contaminated aquifers. This paper evaluates the performance of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor fed with water containing gasoline constituents under denitrifying conditions. Two HAIB reactors filled with polyurethane foam matrices (5 mm cubes, 23 kg/m(3) density and 95 % porosity) for biomass attachment were assayed. The reactor fed with synthetic substrate containing protein, carbohydrates, sodium bicarbonate and BTEX solution in ethanol, at an Hydraulic retention time (HRT) of 13.5 h, presented hydrocarbon removal efficiencies of 99 % at the following initial concentrations: benzene 6.7 mg/L, toluene 4.9 mg/L, m-xylene and p-xylene 7.2 mg/L, ethylbenzene 3.7 mg/L, and nitrate 60 mg N/L. The HAIB reactor fed with gasoline-contaminated water at an HRT of 20 h showed hydrocarbon removal efficiencies of 96 % at the following initial concentrations: benzene, 4.9 mg/L; toluene, 7.2 mg/L; m-xylene, 3.7 mg/L; and nitrate 400 mg N/L. Microbiological observations along the length of the HAIB reactor fed with gasoline-contaminated water confirmed that in the first segment of the reactor, denitrifying metabolism predominated, whereas from the first sampling port on, the metabolism observed was predominantly methanogenic.

The semi-arid region of Chiapas is dominated by N2 -fixing shrubs, e.g., Acacia angustissima. Urea-fertilized soil samples under maize were collected from areas covered and uncovered by A. angustissima in different seasons and N2O and CO2 emissions were monitored. The objective of this study was to determine the effects of urea and of the rainy and dry season on gas emissions from semi-arid soil under laboratory conditions. Urea and soil use had no effect on CO2 production. Nitrons oxide emission from soil was three times higher in the dry than in the rainy season, while urea fertilization doubled emissions. Emissions were twice as high from soil sampled under A. angustissima canopy than from arable land, but 1.2 lower than from soil sampled outside the canopy, and five times higher from soil incubated at 40 % of the water-holding capacity (WHC) than at soil moisture content, but 15 times lower than from soil incubated at 100 WHC. It was found that the soil sampling time and water content had a significant effect on N2O emissions, while N fertilizer and sampling location were less influent. A região semiárida de Chiapas é dominada por árvores fixadoras de N2 do tipo Acacia angustissima. Foram analisadas amostras de solos daquela região cultivados com milho, as quais foram coletadas em zonas sob cobertura e em regiões não cobertas por A. angustissima em diversas épocas do ano, às quais foi adicionada ureia. As emissões de N2O e CO2 foram monitoradas. A finalidade deste trabalho foi determinar o efeito da uréia, nas épocas secas e de chuvas, sobre as emissões de gases dos solos semiáridos, em condições de laboratório. O solo e a ureia não tiveram efeito na produção de CO2. As emissões de NO2 foram três vezes maiores no solo recolhido na época seca do que no solo recolhido na época úmida, e a adição de ureia duplicou essas emissões. O solo sob a cobertura de A. angustissima apresentou emissões de NO2 duas vezes superiores às do solo arável, porém 1,2 vez inferior à de solo colhido em zonas não cobertas por A. angustissima. Essas emissões foram cinco vezes maiores em solos incubados a 40 % da capacidade de retenção de água (CRA) do que em solo úmido, mas 15 vezes mais baixas do que em solo incubado a 100 % CRA. Foi perceptível que a época de amostragem e o teor em água do solo tiveram efeito nas emissões de NO2, enquanto o uso de fertilizantes nitrogenados e o local de amostragem tiveram efeito menor.

This study aimed to evaluate the influence of airflow (0.25, 0.50 and 0.75 L.L-1.min-1) and cycle time (10.45 h, 14.25 h and 17.35 h) on a sequencing batch reactor (SBR) performance in promoting nitrification and denitrification of poultry slaughterhouse wastewater. The operational stages included feeding, aerobic and anoxic reactions, sedimentation and discharge. SBR was operated in a laboratory scale with a working volume of 4 L, keeping 25% of biomass retained inside the reactor as inoculum for the next batch. In the anoxic stage, C: N ratio was maintained between 5 and 6 by adding cassava starch wastewater. A factorial design (22) with five repetitions was designed at the central point to evaluate the influence of cycle time and airflow on total inorganic nitrogen removal (N-NH4++N-NO2-+N-NO3-) and in the whole process (nitrification and denitrification). The highest total inorganic nitrogen removal (93.3%) was observed for airflow of 0.25 L.L-1.min‑1 and a cycle time of 14.25 h. At the end of the experiment, the sludge inside the reactor was characterized by fluorescent in situ hybridization (FISH), indicating the presence of ammonia and nitrite oxidizing bacteria. Este trabalho teve por objetivo avaliar a influência da vazão de ar (0,25; 0,50 e 0,75 L.L-1.min-1) e do tempo de ciclo (10h45; 14h25 e 17h35) no desempenho de um reator em bateladas sequenciais (RBS) em promover a nitrificação e a desnitrificação de água residuária de abatedouro de aves. A operação contemplou as etapas de alimentação, reação aerada e anóxica, sedimentação e descarte. O RBS foi operado em escala de bancada com volume útil de 4 L, mantendo-se 25% do volume do reator como inóculo em cada batelada. Na fase anóxica, a relação C:N foi mantida entre 5 e 6, adicionando-se água residuária do processo de obtenção de fécula de mandioca. Elaborou-se um planejamento fatorial (22) com cinco repetições, no ponto central, para verificar a influência dos fatores, o tempo de ciclo e a vazão de ar, na variável resposta remoção de nitrogênio inorgânico total (N-NH4++N-NO2-+N-NO3-), no processo completo (nitrificação e desnitrificação). A maior remoção de nitrogênio inorgânico total (93,3%) foi observada quando se utilizou vazão de ar de 0,25 L.L-1.min-1 e tempo de ciclo de 14h25. No final do experimento, o lodo do reator foi caracterizado através de hibridização fluorescente in situ (FISH), indicando a presença de bactérias oxidadoras de amônia e de nitrito.

The paper summarizes the state-of-the-art of the most recent advances in biological nitrogen removal, including process design criteria and technological innovations. With reference to the Modified Ludzck Ettinger (MLE) process (pre-denitrification and nitrification in the activated sludge process), the most common nitrogen removal process used nowadays, a new design equation for the denitrification reactor based on specific denitrification rate (SDNR) has been proposed. In addition, factors influencing SDNR (DO in the anoxic reactor; hydrodynamic behavior) are analyzed, and technological solutions are proposed. Concerning technological advances, the paper presents a summary of various "deammonification" processes, better known by their patent names like ANAMMOX(r), DEMON(r), CANON(r), ANITA(r) and others. These processes have already found applications in the treatment of high-strength wastewater such as digested sludge liquor and landfill leachate. Among other emerging denitrification technologies, consideration is given to the Membrane Biofilm Reactors (MBfRs) that can be operated both in oxidation and reduction mode. Resumo O artigo resume o estado da arte dos mais recentes avanços na remoção biológica de nitrogênio, incluindo os critérios para o cálculo do processo e as inovações tecnológicas. Em relação ao processo Ludzck Ettinger modificado (pré-desnitrificação, nitrificação, no sistema de lodo activados), o qual é amplamente utilizado na remoção biológica de nitrogênio, foi proposta uma nova equação para calcular o reactor de desnitrificação, com base na taxa de desnitrificação (SDNR-Specific Denitrification Rate). Além disso, foram analisados os fatores que influenciam o SDNR (oxigênio dissolvido no reator; comportamento hidrodinâmico do reator) e foram propostas as soluções tecnológicas. Quanto à evolução tecnológica, o artigo apresenta um resumo dos vários processos de remoção biológica de amônia, que são mais conhecidos com os nomes patenteados, tais como: ANAMMOX(r), DEMON(r), CANON(r), ANITA(r) e outros. Estes processos já encontraram aplicações industriais no tratamento de águas residuais de alta concentração, tais como o licor de lodo digerido e o percolado de aterro sanitário. Entre as tecnologias emergentes de desnitrificação foram considerados os bioreatores com membranas (MBfR), os quais podem ser operados tanto na fase aeróbia quanto na fase anóxica.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:50:19Z No. of bitstreams: 1 S0100-69162011000100015.pdf: 420223 bytes, checksum: 8bc228b5ff4ea82da914cdcf3fb7421c (MD5) Made available in DSpace on 2013-08-22T18:50:19Z (GMT). No. of bitstreams: 1 S0100-69162011000100015.pdf: 420223 bytes, checksum: 8bc228b5ff4ea82da914cdcf3fb7421c (MD5) Previous issue date: 2011-02-01 Made available in DSpace on 2013-09-30T19:41:15Z (GMT). No. of bitstreams: 2 S0100-69162011000100015.pdf: 420223 bytes, checksum: 8bc228b5ff4ea82da914cdcf3fb7421c (MD5) S0100-69162011000100015.pdf.txt: 26451 bytes, checksum: f2e6ddcb3a2d1a74ac243bc5a9edbcdf (MD5) Previous issue date: 2011-02-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:10:54Z No. of bitstreams: 2 S0100-69162011000100015.pdf: 420223 bytes, checksum: 8bc228b5ff4ea82da914cdcf3fb7421c (MD5) S0100-69162011000100015.pdf.txt: 26451 bytes, checksum: f2e6ddcb3a2d1a74ac243bc5a9edbcdf (MD5) Made available in DSpace on 2014-05-20T15:10:54Z (GMT). No. of bitstreams: 2 S0100-69162011000100015.pdf: 420223 bytes, checksum: 8bc228b5ff4ea82da914cdcf3fb7421c (MD5) S0100-69162011000100015.pdf.txt: 26451 bytes, checksum: f2e6ddcb3a2d1a74ac243bc5a9edbcdf (MD5) Previous issue date: 2011-02-01 O objetivo deste trabalho foi avaliar a desnitrificação de efluente de abatedouro de tilápia, em reator em batelada. Para isto, foi avaliado o efluente gerado por uma indústria processadora de mandioca (manipueira) como fonte de carbono. Também foram avaliadas as condições de agitação do sistema. Os experimentos foram conduzidos em escala de laboratório, em que foram testados cinco níveis de agitação (20; 32; 60; 88 e 100 rpm) e cinco níveis de relação DQO/N (0,1; 1,0; 3,2; 5,4 e 6,3), configurando-se um planejamento do tipo Delineamento Composto Central Rotacional (DCCR), com quatro ensaios nos níveis +1 e - 1; quatro ensaios nos níveis dos pontos axiais (-1,414 e +1,414) e mais uma triplicata no ponto central (0), totalizando 11 ensaios. Avaliaram-se o desempenho da desnitrificação através da remoção de nitrato (%) e a remoção de nitrito (%). Durante o processo, também foram monitorados temperatura (ºC), pH e alcalinidade (mgCaCO3.L-1). Os resultados mostraram que a relação DQO/N teve influência significativa, com intervalo de confiança de 95%, sobre o processo de remoção de nitrato e nitrito, com faixa ótima de operação entre 3,2 e 5,4, cujas eficiências de remoção de nitrogênio foram de 100%. The objective of this work was to evaluate the denitrification of tilapia slaughterhouse wastewater, in a batch reactor. For this, it was evaluated the wastewater from a cassava processing industry (manipueira) as a carbon source. It was also evaluated the shaking conditions of the process. The experiments were carried out in laboratory series, where five shaking levels were tested (20; 32; 60; 88 e 100 rpm) as well as five COD/N ratio levels (0.1; 1.0; 3.2; 5.4 and 6.3), forming a planning as a Central Composite Rotational Design (CCRD), with four essays in levels +1 and - 1; four essays on the axial points levels (-1.414 and +1.414) and one more triplicate in the central point (0), which meant eleven essays. The denitrification performance through the nitrate removal (%) and nitrite removal (%) were evaluated. During this process, temperature (ºC), pH and alkalinity (mgCaCO3.L-1) were also observed. The results showed that the COD/N ratio had significant influence, with a 95 % of confidence interval, on the process of nitrate and nitrite removal, with a great operation range, from 3.2 to 5.4, whose nitrogen removal efficiencies were 100 %. Universidade Estadual Paulista Júlio de Mesquita Filho Faculdade de Ciências Agronômicas Universidade Estadual do Oeste do Paraná (UNIOESTE) Universidade Tecnológica Federal do Paraná Universidade Estadual Paulista Júlio de Mesquita Filho Faculdade de Ciências Agronômicas

A polyurethane packed-bed-biofilm sequential batch reactor was fed with synthetic substrate simulating the composition of UASB reactor effluents. Two distinct ammonia nitrogen concentrations (125 and 250 mg l(-1)) were supplied during two sequential long-term experiments of 160 days each (320 total). Cycles of 24h under intermittent aeration for periods of 1h were applied, and ethanol was added as a carbon source at the beginning of each anoxic period. Nitrite was the main oxidized nitrogen compound which accumulated only during the aerated phases of the batch cycle. A consistent decrease of nitrite concentration started always immediately after the interruption of oxygen supply and addition of the electron donor. Removal to below detection limits of all nitrogen soluble forms was always observed at the end of the 24h cycles for both initial concentrations. Polyurethane packed-bed matrices and ethanol amendments conferred high process stability. Microbial investigation by cloning suggested that nitrification was carried out by Nitrosomonas-like species whereas denitrification was mediated by unclassified species commonly observed in denitrifying environments. The packed-bed batch bioreactor favored the simultaneous colonization of distinct microbial groups within the immobilized microbial biomass. The biofilm was capable of actively oxidizing ammonium and denitrification at high ratios in intermittent intervals within 24h cycles.

Um sistema combinado reator UASB-reator aeróbio foi utilizado para a remoção de nitrogênio total e DQO de efluente de parboilização de arroz. O experimento foi realizado em reatores de bancada, com volumes de 4 L (UASB) e 3,6 L (reator aeróbio). Os parâmetros de operação pH, temperatura, alcalinidade e concentração de ácidos voláteis foram monitorados durante o período experimental. Para o reator aeróbio de mistura completa, foi determinada, também, a concentração de oxigênio dissolvido. O sistema combinado reator UASB-reator aeróbio apresentou uma eficiência de remoção de carbono de 84% e uma eficiência de remoção de nitrogênio total Kjeldahl de 83%. O sistema proposto, nas condições experimentais, demonstrou ser adequado para remoção, simultânea, de DQO e de compostos oxidados de nitrogênio, em reator UASB. An UASB-aerobic reactor system was used for the removal of total nitrogen and COD of effluent from industries of parboilized rice. The experiment was performed in reactors with volumes of 4 L (UASB reactor) and 3,6 L (aerobic reactor), respectevely. Temperature, pH, alkalinity and volatile acids concentration were monitored during the experiment. Dissolved oxygen concentration was determined for the aerobic reactor. The UASB-aerobic reactor system showed 84% carbon removal efficiency and 83% total Kjeldahl nitrogen removal efficiency. This system was able to remove, efficiently, COD and nitrogen in an UASB reactor.

A study of the kinetics of denitrification was carried out in the laboratory based on the quantification of N2O, the final product of the activity of denitrifying microorganisms, when the enzymatic reduction of N2O to N2 was blocked by acetylene. Concentrated mixed liquor (sludge from a reactor with intermittent aeration used for sewage treatment) was used as the inoculum, while methanol, acetic acid, glucose, effluent sewage from an anaerobic fluidized bed reactor and synthetic substrate simulating domestic sewage were used as carbon sources. The mean concentration of nitrate was 20 mg/L. Maxima of N2O production and NO3- consumption occurred between 0.5h and 2.0h of incubation using all the carbon sources, which characterized the denitrification process. Acetic acid and methanol were responsible for the highest rates of N2O production. The estimated number of denitrifying microorganisms in the reactor with intermittent aeration, using the MPN technique, varied from 10(9) to 10(10) MPN/g VSS, indicating a high potential for the occurrence of denitrification. O estudo da cinética do processo de desnitrificação foi realizado em laboratório a partir da quantificação de N2O, produto final da atividade de organismos desnitrificantes, quando acetileno bloqueou a redução enzimática de N2O para N2. Foram utilizados, como inóculo, licor misto concentrado (lodo proveniente de reator com aeração intermitente tratando esgoto sanitário) e, como fontes de carbono: metanol, ácido acético, glicose, esgoto efluente de reator anaeróbio de leito expandido/fluidificado e substrato sintético simulando esgoto sanitário. A concentração média de nitrato foi de 20 mg/L. Entre 0,5h e 2,0h de incubação, ocorreram máximos de produção de N2O e de consumo de NO3-, com todas as fontes de carbono usadas, caracterizando o processo de desnitrificação. Ácido acético e metanol foram responsáveis pelas maiores velocidades de produção de N2O. Os números estimados de microrganismos desnitrificantes no reator com aeração intermitente, empregando a técnica de NMP, variaram entre 10(9) a 10(10) NMP/g.SSV, indicando elevado potencial para a ocorrência da desnitrificação.