The project undertaken in this thesis was performed at MittSverige Vatten och Avfall (MSVA) in cooperation with the Swedish Environmental Research Institute (IVL). The effect of temperature on nitrogen removal using moving bed biofilm reactor (MBBR) was controlled using two separate lines by investigating the influence of temperature on nitrification, pre-denitrification, and post- denitrification in a pilot plant scale. By monitoring the process using chemical analysis, batch tests and online systems, it was possible to observe the changes occurring in the different reactors along with different parameter set-ups and react to the undesirable changes in the system. Due to some limitations, the master's thesis couldn’t fully answer the objective of the study. Nonetheless, the processes were investigated and evaluated to better understand the possibilities and limitations of nitrogen removal with MBBR with treating cold wastewater. During the study period, the inflow coming to the pilot plant, recirculation flow, external carbon dosing, set points of dissolved oxygen and temperature values were controlled. By manipulating these different parameters, it was possible to observe their impacts on the processes. The inflow was variable between 0.42 and 0.67 m3/h, recirculation flow was set to 1.2 m3/h at the beginning then changed to function same as the inflow after being reduced to 0.84 m3/h in between. DO level was variable throughout the entire study period with an average concentration of 4.2mg/l in line 1 and 4.43 mg/l in line2 in all the aerated zones for each line. Temperature of incoming water varied between 5.94 and 9.3 oC with an average temperature of 7.73 oC while the average temperature of the water in the system in line 1 was 13.3 oC and 12.62 oC in line 2. During the 5 months study period, the system achieved an average total nitrogen removal efficiency of 46% in line 1 and 60% in line 2. / Projektet i detta examensarbete utfördes vid MittSverige Vatten och Avfall (MSVA) i samarbete med Svenska Miljöinstitutet (IVL). Effekten av temperatur på kväveborttagning med användning av biofilmreaktorer med rörliga bärare (MBBR, eng. för Moving Bed Biofilm Reactor) kontrollerades genom att undersöka temperaturens inverkan på nitrifikation, pre-denitrifikation och post- denitrifikation i två separata linjer i en pilotanläggningsskala. Genom att övervaka processen med hjälp av kemiska analyser, batchtester och online-system, var det möjligt att observera de förändringar som sker i de olika reaktorerna tillsammans med olika parameteruppsättningar och reagera på de oönskade förändringarna i systemet. På grund av vissa begränsningar kunde masteruppsatsen inte helt svara på syftet med studien. Ändå har processerna undersökts och utvärderats för att bättre förstå möjligheterna och begränsningarna av kväverening med MBBR vid rening av kallt avloppsvatten. Under studieperioden kontrollerades inflödet till pilotanläggningen, recirkulationsflöde, extern koldosering, börvärden för löst syre och temperaturvärden. Genom att ändra dessa olika parametrar var det möjligt att observera deras inverkan på processerna. Inflödet var variabelt mellan 0,42 och 0,67 m3 /h, recirkulationsflödet sattes till 1,2 m3/h i början och ändrades sedan till att fungera som inflödet efter att ha reducerats till 0,84 m3 /h däremellan. DO- nivån var variabel under hela studieperioden med en genomsnittlig koncentration på 4,2 mg/l i linje 1 och 4,4 mg/l i linje 2 i alla luftade zoner för varje linje. Temperaturen på inkommande vatten varierade mellan 5,9 och 9,3 oC med en medeltemperatur på 7,7 oC medan medeltemperaturen på vattnet i systemet i linje 1 var 13,3 oC och 12,6 oC i linje 2. Under den 5 månader långa studieperioden uppnådde systemet en genomsnittlig total kvävereduktionseffektivitet på 46 % i linje 1 och 60 % i linje 2.

Examensarbetets syfte var att undersöka möjligheter till denitrifikation på sandfilter (SF) i industriell skala och hur det jämför sig med konventionella metoder för att uppnå denitrifikation och effekten av förändringen på processen vid Bromma reningsverk. Parametrar som undersöktes var rening av ammonium och nitrat, luftning, temperatur, pH, rening av fosfor, rening av organiskt material, rening av suspenderat material, förbigång av vatten vid SF och aktivslamanläggning (ASA), drifttider för SF:arna och total vattenbelastning på ASA och SF. Mätningarna gjordes med aCurve, ett online internt program vid Bromma reningsverk där onlineanalysatorer och driftsparametrar loggades. Nitrat- och nitritvärdena kontrollerades med standardiserade kyvettmetoder. Reningen av totalkväve uppnådde värden på 0,62-0,94 när denitrifikation på SF implementerades. Ökad igensättning av SF inträffade på grund av dosering av metanol på SF och tillväxt av mikroorganismer som orsakade en ökad risk för förbigång av SF, särskilt under hög vattenbelastning. Reningen av suspenderat material, organiskt material och fosfat påverkades inte av implementeringen av denitrifikation på SF. Resultaten av examensarbetet kan användas för att ytterligare optimera konventionella metoder för kväverening i reningsverk. För ytterligare studier kunde igensättning av SF vid användning av metanoldosering på sandfilter undersökas och metoderna kan jämföras i en kontrollerad miljö. / This thesis work aimed to investigate opportunities of denitrification on sand filters (SFs) at industrial scale and how it relates to conventional methods of achieving denitrification and its effect on the process at Bromma WWTP. Investigated parameters were ammonium and nitrate removal, oxygen and aeration, temperature, pH, phosphorus removal, removal of organic material, removal of suspended solids, water bypass of SF and activated sludge facility (ASF), operational times of the SFs and total water load on ASF and SF. The measurements were made with aCurve, an online internal program at Bromma WWTP where online analyzers and operational parameters were logged. The online values for nitrate and nitrite were controlled using standard cuvettes methods. Tot-N removal achieved values of 0.62-0.94 for denitrification on SF. Increased clogging of SFs occured due to dosage of methanol on SFs and growth of microorganisms causing an increased risk of SF bypass especially during high water load. Removal of TSS (total suspended solids), BOD7 and phosphate were unaffected by the implementation of denitrification on SFs.  The findings of the thesis can be used to further optimize conventional methods of nitrogen removal in WWTPs. For further studies the clogging of SFs when using methanol dosage on sand filters could be investigated as well as comparing the methods in a controlled environment.

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No description available.

<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>

Vid Hammarby Sjöstadsverk drivs en pilotanläggning som är en mindre skala av det framtida avloppsreningsverket i Henriksdal. Delar av reningsprocessen består av membranbioreaktorer. I pilotanläggningen finns en zon kallad RAS-DeOx dit returslammet från membrantankarna och rejektvattnet från slambehandlingen leds. Luftning av membrantankarna gör att returslammet är syrerikt och rejektvattnet innehåller mycket ammonium.Zonen fungerar som ett nitrifikationssteg då syret i returslammet kan oxidera ammoniumet från rejektvattnet. Dessutom kan zonen minska syrehalterna i returslammet för att undvika att det hamnar i pilotanläggningens fördenitrifikation. För att få bättre uppfattning om vad som sker i zonen och hur denna fungerar som ett nitrifikationssteg studerades nitrifikation, denitrifikation och syreförbrukningen i zonen. För att utvärdera RAS-DeOx-zonen belastades den med olika nivåer av ammonium från rejektvattnet vid olika hög luftning i membrantankarna. Detta utfördes både experimentellt direkt på pilotanläggningen och i en simuleringsstudie där processimuleringar genomfördes i en simuleringsmodell. I modellen utvärderades även två styrstrategier för zonen.Resultaten från studierna visade att både nitrifikation och denitrifikation förekom i zonen. Jämfört med simuleringsstudien varierade omfattningen av nitrifikation och denitrifikation mer i den experimentella studien. Båda studierna visade att det fanns risk att syre hamnande i pilotanläggningens fördenitrifikation. Styrstrategierna visade att det inte var fördelaktigt för pilotanläggningens resurseffektivitet att zonen luftades vid hög ammoniumbelastning från rejektvattnet. Det visade sig också att det var ingen större skillnad när det gällde pilotanläggningens prestation vid högt, lågt eller styrt returflöde för zonen. Däremot skiljde sig prestationen mer avseende luftning och koldosering.Utöver att det förekom nitrifikation och denitrifikation i zonen bedömdes den även fungera som ett nitrifikationssteg för ammoniumet i rejektvattnet. Dessutom minskade den syrehalterna i returslammet. Hur väl ammonium nitrifierades och syre förbrukades i zonen berodde på förhållandena i pilotanläggningen och förhållandet mellan mängden ammonium och syre i zonen. / At Hammarby Sjöstadsverk there is a pilot plant which is a smaller version of the future wastewater treatment plant at Henriksdal. Parts of the treatment process steps are membrane bioreactors. There is a zone in the pilot plant which is called RAS-DeOx to where the return activated sludge from the membrane tanks and the reject water from the sludge treatment are pumped. The return activated sludge contains oxygen since the membranetanks are aerated and the reject water has high contents of ammonium.The zone works as a nitrification step for the ammonium in the reject water, and also reduces the oxygen levels in the return sludge to avoid oxygen in the pilot plant's pre-denitrification step. To aquire a better understanding of what occurs in the zone and how it functions as a nitrification step; nitrification, denitrification and oxygen consumption was studied in the zone. To evaluate the RAS-DeOx-zone it was loaded with different loads of ammonium from the reject water at different levels of aeration in the membrane tanks. This was evaluated both experimentally at the pilot and in a simulation model of the pilot. In the simulation model two control strategies for the zone were also evaluated.It was shown that both nitrification and denitrification occurred in the zone. Furthermore, both studies showed that there is a risk that oxygen occurs in pilot's pre-denitrification step if the ammonium load in zone was low. Then, all of oxygen in the zone was not consumed. As for the control strategies, it was shown that the benefits were low for the resource efficiency of the pilot when the zone was aerated during high loads of ammonium. The performance of the pilot was similiar for high, low and regulated return flows for the zone, but the aeration and carbon dosage in the pilot differed.Besides that both nitrification and denitrification occurred in the zone, it was also functioning as a nitrification step for the ammonium from the reject water. The oxygen from the return sludge was reduced as well. The extent of nitrification and consumption of oxygen in the zone depended on the circumstances in the pilot and the relationship between the amount of oxygen and ammonium.

O avanço da tecnologia anaeróbia para tratamento de esgotos deve ser creditado em grande parte ao desenvolvimento dos modernos reatores de alta taxa de aplicação orgânica, com os maiores méritos ao filtro anaeróbio ascendente e principalmente, à configuração do UASB. A evolução dos reatores levou à busca para maximizar a aplicação prática para aproveitar todas as potencialidades dos processos anaeróbios. Todas as modernas configurações têm em comum a preocupação em atender requisitos essenciais em um reator: formação e retenção de grande quantidade de biomassa e melhoria do contato biomassa/matéria orgânica. Esta pesquisa tem como principal objetivo avaliar dois reatores anaeróbios, operados em batelada seqüencial e periodicamente aerados, como unidade de tratamento das águas residuárias geradas no campus da Universidade de São Paulo em São Carlos. Um dos reatores contém biomassa imobilizada em espuma de poliuretano e o outro é operado com biomassa suspensa ou auto-imobilizada, sem utilização de suporte inerte. Os sistemas, na primeira etapa operacional, anaeróbia, apresentaram remoção de matéria orgânica, com eficiências médias para espuma de 61% (ASBBR) e grânulos de 56% (ASBR) e eficiências na remoção de sólidos iguais a 62% de SST e 65% de SSV no ASBBR e 56 % de SST e 61% de SSV no ASBR. Na segunda etapa operacional, anaeróbia e aeróbia, os reatores ASBR e ASBBR, mostrou que a estratégia de operação com etapa anaeróbia seguida por período com aeração não foi adequada para remoções de matéria orgânica e nitrogênio. Os reatores operaram com grande instabilidade e baixas eficiências de remoção de matéria orgânica, abaixo das observadas em reator operado de forma anaeróbia. / The advance of anaerobic technology for wastewater treatment should be credited in great part to the development of the modern reactors with high rates of organic application, with merit to the ascendant anaerobic filter and mainly to the UASB configuration. The evolution of reactors led to the search to maximize the practical aplication to make the best use of all the potentialities of the anaerobic processes. All the modern configurations have in common the preoccupation to deal with essential requisites in a reactor: formation and retention of a large quantity of biomass and improvement in the biomass/organic matter contact. This research prime objective is to evaluate two anaerobic reactors, operated in sequential batch and periodically aerated, as unity of treatment of wastewaters generated at the campus of the University of São Paulo in São Carlos. One of the reactors contains biomass immobilized on polyurethane foam and the other is operated with suspended or autoimmobilized biomass, without the use of inert support. The systems, in the first operational step, anaerobic, presented organic matter removal, with medium efficiencies for foam of 61% (ASBBR) and granule of 56% (ASBR) and efficiencies in the removal of solids equal to 62% of TSS and to 65% of VSS in the ASBBR and to 56% of TSS and to 61% of VSS in the ASBR. In the second operational step, anaerobic and aerobic, the ASBBR and ASBR reactors showed that the strategy of operation with anaerobic step followed by a period with aeration was not adequate for the removal of organic matter and nitrogen. The reactors operated with great instability and low efficiency of organic matter removal, with results below of the ones observed in a reactor operated in the anaerobic way.

Os processos anaeróbios têm sido recentemente adotados como unidades principais em sistemas de tratamento de efluentes, em virtude das inúmeras vantagens que apresentam. Este trabalho de pesquisa, no entanto, visa possibilitar a obtenção de fonte de carbono prontamente degradável a partir de uma das primeiras aplicações da biotecnologia anaeróbia: a digestão de lodo. A partir de um digestor hidrolítico e acidogênico de lodo primário foi possível a obtenção de efluentes com altas concentrações de DQO solúvel (da ordem de 4.000 mg/L) e ácidos graxos voláteis – AGV – (da ordem de 600 mg/L). Porém, foi necessária a aplicação de um processo de troca iônica para a remoção das altas concentrações de 'NH IND.4'POT.+' (da ordem de 480 mg/L) no efluente do DHL. A utilização de zeólitas – minerais de silício e alumínio – permitiu a remoção de íons amônio, através de experimentos em bateladas e colunas. As capacidades de adsorção de 'NH IND.4'POT.+' por massa de zeólitas atingidas foram de 8,0 mg 'NH IND.4'POT.+'/g. Adicionalmente, foi realizado o estudo da regeneração do mineral, através de processo biológico de nitrificação e posterior aplicação do mineral regenerado para remoção de 'NH IND.4'POT.+'. O processo resultou na obtenção de minerais com capacidades próximas às atingidas por amostras de zeólitas virgens. Além de restaurar grande parte da capacidade inicial de troca iônica do mineral (87% da capacidade inicial), o processo de regeneração biológica permite a obtenção de efluente com altas concentrações de nitrato (da ordem de 400 mg/L), podendo ser aproveitado para correção de solos com deficiência deste nutriente. O processo como um todo envolve conceitos de sustentabilidade aplicada aos sistemas de tratamento de efluentes, pois promove a utilização de subproduto de estações de tratamento, bem como a reutilização do mineral aplicado no processo de troca iônica. / Anaerobic processes have recently been widely adopted as core units in sewage treatment systems, due to several advantages inherent in these processes. However, this research aims at the acquisition of readily degradable carbon source by means of a primary application of anaerobic biotechnology: the sludge digestion. The use of a hidrolitic and acidogenic digester of primary sludge made it possible to achieve high concentrations for soluble COD (around 4.000 mg/L) and volatile fatty acids – VFA - (around 600 mg/L). Along with high concentrations of soluble COD and VFA, the effluent of the hidrolitic and acidogenic digester also presented undesirable significant amount of ammonium (480 mg 'NH IND.4'POT.+'/L), which was removed by the application of ion-exchange process. Natural zeolites were employed as the cation exchanger, achieving values of 8.0 mg 'NH IND.4'POT.+'/g for ammonium removal per unit mass of zeolite. The zeolite saturated with 'NH IND.4'POT.+' ions was biologically regenerated by nitrifying sludge. Regenerated zeolite samples were then reused for ammonium removal and presented removal capacities close to the ones achieved by fresh samples. The whole process (primary sludge digestion followed by ion-exchange process for ammonium removal and biological regeneration of saturated zeolite samples) comprises several sustainability concepts, as it promotes, concomitantly, primary sludge pre-digestion and the reutilization of the zeolite employed as cation exchanger for 'NH IND.4'POT.+' ions removal. In addition to partially recovering original exchange capacity (87% of original capacity), biological regeneration of saturated zeolite also produced, as effluent, highly nitrate concentrated solution (around 400 mg/L), which could be used as nitrogen source for soil enrichment.

Utilizou-se reator de leito estruturado e aeração intermitente (RLEAI) como pós-tratamento de efluentes de reator UASB tratando esgoto sanitário. O volume total e o tempo de detenção hidráulica (TDH) do reator UASB eram de 11,2 L e 9 horas, respectivamente. O RLEAI possuía volume total de 11,0 L e, devido às hastes cilíndricas verticais de espuma de poliuretano usadas como suporte para a biomassa, o volume útil foi de 9,6 L. Este reator foi operado com um TDH de 12 horas, razão de recirculação igual a 3 e foi alimentado continuamente com efluente do reator UASB. O objetivo deste trabalho foi avaliar a influência do tempo de aeração no desempenho do RLEAI na remoção de matéria orgânica e nitrogênio. O reator foi operado com aeração contínua, e tempos de aeração intermitentes (tempo aerado/não aerado) de 2h/1h, 1h/1h, 0,75h/1,25h, 1h/ h e 1h/3h. Em todas as fases a DQO efluente ao sistema ficou entre 26 e 42 mg.L-1. A fase de aeração contínua foi fundamental para o estabelecimento da comunidade nitrificante no sistema. A oxidação do nitrogênio total (como NTK) para nitrato aumentou de 62% (aeração contínua ) para 82% (aeração intermitente de 1h/2h) devido à alcalinidade gerada pela desnitrificação, estimulada pelo período não aerado. Na fase 1h/3h a oxidação do NTK foi prejudicada pela falta de oxigênio, e a eficiência nesta fase foi de 42%. A maior remoção estável de N-total foi obtida na fase 1h/2h com eficiência de 29%. Foi observado no ensaio em batelada que a velocidade de desnitrificação via nitrato aumentou de 0,90 mg N. g SSV-1.h-1 para 2,55 mg N. g SSV-1.h-1 após aclimatação da biomassa em condições de excesso de matéria orgânica. Concluiu-se que a remoção de N-total foi limitada pela baixa quantidade de matéria orgânica advinda do reator UASB, sendo a relação DQO/N do afluente ao RLEAI de 3,04. A elevada oxidação de NTK e de remoção de matéria orgânica, aliadas à baixa produção sólidos e ao alto tempo de retenção celular (139 dias), mostram que o RLEAI é uma alternativa interessante em comparação às tecnologias praticadas atualmente para pós tratamento de efluentes de reatores anaeróbios. / This study used a structured bed reactor under intermittent aeration for post-treatment of UASB rector treating domestic sewage. The UASB reactor had a total volume of 11.2 L and 9 hours of hydraulic retention time (HRT). The structured bed reactor had a total volume of 11.0 L and working volume of 9.6 L due to the vertical cylindrical rods with polyurethane foam used as a support for the biomass. This reactor was operated whit 12 hours of HRT, recirculation ratio equal to 3 and was continuously fed with effluent from the UASB reactor. The aim of this study was to evaluate the influence of aeration time on RLEAI performance in removal of organic matter and nitrogen. For this the reactor was operated with continuous aeration and intermittent aeration periods (time aerated/ non-aerated) of 2h/1h, 1h/1h, 0.75h/1.25h, 1h/2h e 1h/3h. During all operation time the COD effluent to the system it was between 26 and 42 26 e 42 mg.L-1. The continuous aeration operation was fundamental to the establishment of the nitrifying microorganism community in the system. The TKN oxidation to nitrate increase from 62% (continues aeration) to 82% (intermittent aeration 1h/2h) due to the alkalinity generated by denitrification, that was stimulated by non-aerated period. In the intermittent aeration period of 1h/3h the NTK oxidation was damaged by a lack of oxygen; the efficiency at this stage was 42%. The most stable total nitrogen removal was obtained in 1h/2h aeration period with 29% efficiency. It was observed in the batch test that nitrate denitrification rate increased from 0.90 mg N. g VSS-1.h-1 to 2.55 mg N. g VSS-1.h-1 after acclimation of biomass in conditions of excess organic matter. It was inferred that the removal of total nitrogen was limited by the low amount of organic matter load from the UASB reactor; the COD/N ratio of the influent was 3.04. The high NTK oxidation and high organic matter removal, combined with low solid production and high cell retention time (139 days), leads to the conclusion that the structured bed reactor under intermittent aeration is an interesting alternative compared to the technologies currently applied for post treatment of anaerobic reactors effluent.

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.