Aerobic (AeMBRs) and Anaerobic Membrane Bioreactors (AnMBRs) are an essential part of the advanced wastewater treatment options, which offer advantages in terms of higher effluent discharge and smaller footprints over the traditional wastewater treatment. This study evaluates the performance of (AnMBRs) by analyzing the cumulative effect of eleven physico-chemical parameters from the data obtained from the studies conducted from year 2000 onwards. Effect of various parameters such as Solid Retention Time (SRT), Hydraulic Retention Time (HRT), Mixed Liquor Suspended Solids (MLSS), influent Chemical Oxygen Demand (COD), Organic Loading Rate (OLR), influent COD, and temperature on the COD removal, methane production and membrane fouling were evaluated. Spearman’s correlation analysis was performed to investigate the impact of environmental and operational parameters on membrane fouling, COD reduction, EPS/SMP and methane production and explain the results. It should be noted that the literature used has all needed variables; incomplete data sets were removed for the regression analysis, in this case, the fouling rate may be estimated. Of these variables, the fouling rate was significantly correlated only with flux (r = 0.291, p =

Producing renewable energy from biomass or from the wastewater treatment process has gained momentum in the past 20 years. Anaerobic digestion has historically been used as one step in the waste treatment process, to both reduce the mass of waste that needs to be disposed of and to generate biogas. This process is typically only able to reduce 30-40% of the waste mass because of the recalcitrant nature of the waste streams being treated. Anaerobic pretreatment with the thermophilic bacteria Caldicellulosiruptor bescii (C. bescii) has been proven to increase the percentage of mass digested and consequently increase methane production to 75%-85%. However, even with the use of pretreatment with C. bescii, it still leaves 15%-25% of the methane potential wasted. In anaerobic digestion, volatile fatty acids (VFAs) are of interest because they are the precursors to the production of methane. By using HPLC-UV-vis techniques, VFAs can be speciated and quantified in as little as 12-minutes. Depending on the pretreatment system, operational procedures for both the pretreatment and anaerobic digestion system, and substrate, the type and composition of VFAs can vary. For example, in several experiments analyzed it was found that valeric acid is a VFA that is dominate in waste activate sludge treatments, while acetic acid is in higher proportions with manure substrates. Besides methane production, VFA monitoring can detect issues with a bioreactor performance. By tracking VFA trends, the health of the system can be assessed.

"Transparency- the ability to see into and understand the inner workings of a landscape- is an absolutely essential ingredient to sustainability" -Robert Thayer from "Green World, Green Heart" Current land filling practices that bury waste and debris below layers of earth and synthetic caps do not take into account the potential of reclamation of the site after the landfill debris has become stable. As development and consumerism increases, the need for land reclamation grows stronger, as earth will succumb to overabundance of human excessiveness. Can a space be created that not only reclaims land, but also exposes what is hidden- in order to educate the public on the importance of recycling and sustainability? Is it possible to design a space that addresses the issues and culture of the past, present and future, particular to a geographic site? Can landscape architects use landscape as an educational medium for self-discovery? / Master of Landscape Architecture

The main hypothesis tested in this thesis was that poor animal production from saltbush pastures is due to the negative effects of high sodium chloride (NaCl) and potassium chloride (KCl) on the ruminal environment, and subsequent effects on microbial populations and products of rumen fermentation. This main hypothesis was tested in two experiments. In the first experiment (Chapter Four) the effects of saltbush and a formulated high-salt diet on the ruminal environment and microbial populations were measured over 24-hours following feeding. Feeding both the saltbush and high-salt diet increased the salinity of the rumen fluid, but the formulated high-salt diet caused a decrease in ruminal pH while the saltbush caused an increase. This resulted in differences in the composition of the ruminal microbial populations between the sheep fed different diets. In the second experiment (Chapter Five) the effects of saltbush and a formulated highsalt diet on rumen fermentation were measured. Sheep fed saltbush had inefficient rumen fermentation and this was only partially explained by the high salt content of the diet. Diets containing high levels of NaCl and KCl provided low levels of net energy to sheep, but sheep fed saltbush lost more energy as methane and faecal energy compared to sheep fed the formulated high-salt diet. Inefficient rumen fermentation could help to explain poor animal production from saltbush pastures. Energy supplements such as barley grain can improve the value of saltbush pastures as feed for sheep, but there is no information on how much supplement is required. A third experiment (Chapter Six) was designed to test the hypothesis that there would be an optimal amount of barley required to improve the efficiency of rumen fermentation in sheep fed saltbush. Barley and straw were combined in a pellet and substituted for saltbush at 0, 20, 40, 60, 80 and 100% of the maintenance ration. Feeding barley and straw improved the efficiency of rumen fermentation in sheep fed saltbush, with an optimal level of supplementation at 60% of the maintenance diet. This is likely to be lower (approximately 20% of maintenance) if barley is fed without straw.

[Truncated abstract] In Australia, there is pressure to reduce the amount of methane produced by ruminant livestock because they are the single largest source of methane emitted from anthropogenic sources, accounting for 70.7% of agricultural methane emissions. In addition, methane production represents a loss of gross energy intake to the animal. The organisms that are responsible for methane production in the animal gut are a distinct group of Archaea called methanogens. Methanogens occupy three different niches within the rumen. Some live freely in the rumen digesta (planktonic), others are attached to the outer surface of the rumen ciliates (ectosymbiotic), and some reside within the ciliates (endosymbiotic). The types and number of methanogens, as well as rumen ciliates and their symbiotic interactions, influence the amount of methane produced from the rumen. These factors in turn are affected by many factors, including diet and ruminal retention time. In this thesis, I tested the general hypothesis that increasing the amount of grain in the diet and reducing the retention time would affect the abundance and diversity of methanogens in their different niches, including their association with ruminal ciliates. Twenty-four fistulated sheep were used in a complete factorial design with the sheep randomly divided into four groups. ... The change in DGGE banding patterns and Shannon indices when sheep were fed grain indicated that the types of methanogens changed when sheep were fed low and high grain diets, but their diversity did not. In contrast, the diversity of rumen ciliates decreased when sheep were fed a high grain diet. A total of 18 bands from the DGGE analysis of the ciliates were sequenced. All except one, which was 98% similar to Cycloposthium sp. not found previously in the rumen, matched the sequences for previously identified rumen ciliates. Some of the rumen ciliates identified were not present in sheep fed the high grain diet. On a high grain diet, methanogens associate endosymbiotically with rumen ciliates to get better access to hydrogen. It appears that the association between methanogens and rumen ciliates is dictated by the availability of hydrogen in the rumen and not the generic composition of the ciliate population. Furthermore, endosymbiotic methanogens appear to produce less methane than methanogens in other niches. The pot scrubbers did not change ruminal retention time but they did reduce the acetate/propionate measurements observed in sheep on the high grain treatment. The reason why pot scrubbers had this effect remains unknown, but it is interesting to consider that some physical interaction has occurred between the pot scrubbers, the grain and the sheep that has improved the fermentation parameters in sheep fed a high grain diet. The results from this study have advanced our understanding of the interaction between methanogens and ruminal ciliates, and methanogenesis in the rumen in response to dietary changes and mechanical challenges. Extending this work to look more specifically at the species of methanogens that are most closely linked to high methane production and how they interact with the ruminal ciliates will be critical for manipulating enteric greenhouse gas emissions.

Because of the increasing trends in energy consumption and increased environmental awareness, greater focus has been placed on improvement and development of renewable energy sources. An already proven and accepted method is biogas production from anaerobic digestion at municipal wastewater treatment plants. In the waste water treatment process solid material and dissolved pollutants are separated from the water, forming a sludge. The sludge is separated from the process and stabilized during anaerobic digestion or aerobic aeration. Most often, mesophilic anaerobic digestion is used. Because of degradation by microorganisms, biogas with a high content of methane is formed during the digestion. To optimize the process different studies with co-digestion with sludge and other substrate have been made. It has been showed, in earlier research studies, that co-digestion with microalgae and sewage sludge results in a synergistic effect with increased biogas production. As the microalgae are microorganisms which use photosynthesis they contain stored energy from sun light. The stored energy will be available when the microalgae are digested in mesophilic conditions. In contrast to other biomass suitable for co-digestion microalgae have the advantage of being able to grow in waste water and reduce the pollutants in the water phase. Cultivation of microalgae will therefore not compete with the cultivation of food production and at the same time has the possibility to decrease the electricity- and heat consumption at the wastewater treatment plants. The aim of this study was to investigate how a possible synergetic effect between microalgae and sewage sludge effects the biogas production and the process stability. The microalgae was cultivated in municipal waste water from the WWTP in Umeå (Sweden) and the sludge was collected from the WWTP in Västerås (Sweden). The fermenters used was of the type DOLLY© and the active volume was 5 dm3. The temperature in the fermenters was kept at 37 °C and the study was divided into two periods. During the first period the hydraulic retention time was 15 days and the organic loading rate 2.4 g VS dm-3 d-1. During the second period the hydraulicretention time was kept at 10 days and the organic loading rate was 3.5 g VS dm-3 d-1. The result showed an increase with 54.6 % in methane production per reduced VS in the fermenter with co-digestion compared to the fermenter where only sludge was digested. Period one showed the highest increase. The result also showed a good process stability for both fermenters during the whole experiment. This study shows that there are reasons for continued investigations about co-digestion with microalgae and sewage sludge for an increased biogas production. / På grund av ökande el- och värmeförbrukning och ökat miljöengagemang har större fokus lagts på förbättring och utveckling av förnyelsebara källor för el- och värmeproduktion. En redan beprövad och accepterad metod för framställning av förnyelsebar energi är från biogasproduktion vid kommunala reningsverk. Vid rening av avloppsvatten avskiljs fasta partiklar och lösta föroreningar och bildar ett slam som separeras från vattnet. Slammet kan sedan stabiliseras anaerobt genom rötning eller aerobt genom luftning. En ofta använd metod vid konventionella reningsverk är mesofil anaerob rötning. Vid rötningen bryts material ner av mikroorganismer och genererar biogas som framförallt innehåller metan och koldioxid. För att optimera en sådan process och därmed kunna utvinna mer gas har det tidigare undersökts hur samrötning med olika material påverkar biogasproduktionen. Det har visat sig i forskningsförsök att samrötning med mikroalger och orötat blandslam ger en synergieffekt och mer biogas produceras. Mikroalgerna innehåller lagrad energi från solljus, då de är fotosyntesiserande organismer. Den lagrade energin har visat sig bli tillgänglig vid mesofil anaerob nedbrytning. Till skillnad från annan biomassa som undersökts för samrötning kan mikroalgerna odlas på avloppsreningsverken och fungera som en del av reningsprocessen då mikroalgerna tar upp näringsämnen ur vattnet de växer i. På det sättet undviks konkurrens om odlingsmark för livsmedel och så blir reningsprocessen på avloppsreningsverken mer el- och värmeeffektiv. Syftet med studien var att undersöka om eventuell synergieffekt mellan mikroalgerna och slammet påverkar biogasproduktionen och processtabiliteten vid mesofil anaerob rötning. Mikroalgerna som användes var odlade på mekaniskt renat spillvatten från Umeås reningsverk och slammet som användes hämtades ifrån Västerås reningsverk. Rötkamrarna som användes var av modellen DOLLY© med en aktiv volym på 5 dm3. Temperaturen i rötkamrarna hölls kring 37°C och studien var uppdelad i två perioder. Under period ett var den hydrauliska uppehållstiden 15 dygn och den organiska belastningen 2,4 g VS dm-3 d-1, medan period två hade en hydraulisk uppehållstid på 10 dygn och en organisk belastning på 3,5 g VS dm-3 d-1. Resultaten visade att metangasproduktionen per tillförd mängd organiskt material var lägre vid samrötning jämfört med rötning av enbart slam. Metangasproduktionen per reducerad mängd organiskt material ökade med upp till 54,6 % vid samrötningen jämfört med rötning av enbart slam. Period ett gav upphov till den största ökningen. Processen hölls stabil även vid inblandning av mikroalger, under både period ett och två. Studien visar att det finns ett underlag för fortsatta studier kring samrötning av mikroalger och slam för en ökad biogasproduktion.

This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.

O presente trabalho teve como principal objetivo avaliar o desempenho de um reator anaeróbio híbrido (RAnH) em escala piloto no tratamento da fração líquida de estrume bovino, visando à remoção de matéria orgânica e à produção de biogás. O RAnH estudado apresentava volume total 6,2 m3 e foi composto por manta de lodo, na qual a biomassa encontrava-se suspensa, e leito fixo, no qual utilizou-se Biobob® como material suporte para imobilização da biomassa. Para dar suporte a partida do RAnH, a água residuária em estudo foi submetida a teste de biodegradabilidade visando avaliar a influencia da inoculação do reator no potencial de biodegradabilidade e de produção de metano. No teste, a inoculação mostrou-se adequada, apresentando biodegradabilidade de 57 ± 4% e produção de metano de 344 ± 26 mL CH4. g SV-1. A operação do RAnH foi realizada por 260 dias e foi dividida em duas etapas: etapa inicial, na qual se procedeu a adequação da operação do reator, e etapa experimental, na qual se avaliou o desempenho do reator perante o aumento progressivo da carga orgânica aplicada. Durante a operação do reator foi alcançada a aplicação de COV bruta total de 25,50 ± 2,53 kg DQO.m-3.d-1 e a COV solúvel total de 7,69 ± 0,02 kg DQO.m-3.d-1, sendo atingido o TDH de 1,27 ± 0,004 d. O RAnH apresentou eficiência de remoção média de 65 ± 4 % durante a etapa experimental. A produção média de metano foi de 0,310 ± 0,095 m3 CH4. m-3.d-1 e 0,098 ± 0,018 m3 CH4. kg SVad, com 89 ± 3% de metano na composição do biogás. O potencial de produção de energia elétrica estimada com base no reaproveitamento metano produzido no RAnH foi de 0,89 kWh.m-3. O aproveitamento desta energia em sistema com vazão de 3.500 m3.d-1 geraria energia suficiente para abastecer 615 residências e uma economia mensal de R$ 11.835,09. / The main objective of this work was to evaluate the performance of a pilot-scale anaerobic hybrid reactor (RAnH) in the treatment of the liquid fraction of dairy manure, in order to remove organic matter and produce biogas. The applied RAnH had a total volume of 6.2 m3 and was composed of sludge blanket, in which the biomass was suspended, and fixed bed, in which Biobob® was applied as a support material for biomass immobilization. In order to support RAnH startup, the wastewater under study was submitted to a biodegradability test to evaluate the influence of reactor inoculation on the biodegradability potential and methane production potential. In the test the inoculated condition presented appropriate biodegradability (57 ± 4%) and higher methane production potential (344 ± 26 mL CH4.gVS-1). The RAnH operation was performed for 260 days and was divided into two stages: initial stage, in which the reactor operation was adjusted, and the experimental stage, in which the reactor performance was evaluated with the progressive increase of the applied organic load. During the reactor operation was reachead total raw VOC application of 25.50 ± 2.53 kg COD m-3.d-1 and total soluble VOC of 7.69 ± 0.02 kg COD m-3.d-1, with the HRT of 1.27 ± 0.004 d. The RAnH presented average removal efficiency of 65 ± 4% during the experimental stage. The average methane production was 0.310 ± 0.095 m3 CH4.m-3.d-1 and 0.098 ± 0.018 m3 CH4. kg VSad, with 89 ± 3% of methane in the biogas composition. The potential of electric energy production estimated based on the reuse of the methane produced in the RAnH was 0,89 kWh.m-3. The use of this energy in a system with a flow of 3,500 m3.d-1 would generate sufficient energy to supply 615 homes and a monthly saving of R$ 11,835.09.

O tratamento de água residuária rica em sulfato por via de processo anaeróbio é um grande desafio, devido ao potencial de redução do sulfato pela via biológica a sulfeto, o que pode inviabilizar o aproveitamento do biogás e afetar o tratamento por seus efeitos tóxicos e inibitórios. Neste contexto, o presente trabalho investigou a potencial aplicação da separação de fase para minimizar tais problemas de operação. A operação de reator de primeira fase visa estabelecer um ambiente sulfetogênico sob condições acidogênicas. Os efeitos da pré-acidificação da água residuária sobre a produção de metano foram avaliados por meio do monitoramento de dois reatores metanogênicos, um sistema de fase única alimentado com água residuária rica em sulfato e um sistema de duas fases alimentado com água residuária acidificada. Em todos os casos foram utilizados reatores anaeróbios de leito estruturado, aplicada condições termofílica de temperatura (55°C). Para o sistema de primeira fase, dois reatores com diferentes materiais foram comparados: reator com cilindros de polietileno de baixa densidade (RAS-PEBD) com cinco etapas de operação (13 subetapas) e outro reator com cubos de espuma de poliuretano (RAS-PU) com quatro etapas de operação. As principais estratégias operacionais para otimização da redução do sulfato a variação do tempo de detenção hidráulica (TDH: 6-15 h RAS-PEBD; 12 - 16 h RAS-PU ), carga orgânica volumétrica (COVafl: 10 - 20,0 kg-DQO m-3 d-1 - RAS-PEBD; 15 - 20 kg-DQO m-3 d-1 - RAS-PU), carga de sulfato volumétrica (CSV: 3,2-16,0 kg-SO4 m-3 d-1 - RAS-PEBD; 4 - 8 kg-SO4 m-3 d-1 - RAS-PU) e velocidade ascensional (Va: 0,06 3,35 m h-1 - RAS-PEBD; 3,42 7,9 m h-1 - RAS-PU). Após longo período de adaptação da biomassa no RAS-PEBD, verificou-se o aumento da eficiência e stripping do sulfeto. A recirculação controlada do efluente foi um fator chave para melhoria do sistema. O mesmo não foi obtido em RAS-PU, apresentando perda de desempenho devido a problemas de colmatação e subsequente aparecimento de vias preferenciais. O efluente do reator de primeira fase com carga de sulfato residual menor que 7% (COVefl de 15,12 kg-DQO m-3d-1 e sulfeto de 256 mg L-1, subetapa X) foi aplicado em reator metanogênico de segunda fase (RMI). Considerando a comparação entre os sistemas metanogênicos, fixou-se uma carga orgânica (CO) inicial de 2,5 g-DQO d-1, sendo aumentada até 5 g d-1. A partida do reator de fase única apresentou limitações, requerendo aplicação de baixos valores de CO, o que demandou 140 dias até a estabilização para a carga de 5 g-DQO d-1. Por sua vez, o sistema com duas fases necessitou de 102 dias e apresentou maior geração de metano (RMI 1,95 L-CH4 d-1 e RMII 1,76 L-CH4 d-1). A separação de fases permitiu a geração de efluente acidificado com menores concentrações de sulfato residual, resultando em maior produção de metano e reduzida concentração de sulfeto no biogás no sistema de duas fases, quando comparado ao sistema de fase única. / The treatment of sulfate-rich wastewater via anaerobic processes is challenging, due to the potential biological sulfate reduction to sulfide, which limits biogas use and affect treatment performance due to toxic and inhibitory effects. In this context, this study investigated the potential application of phase separation to minimize such operating problems. The operation of the first-stage reactor aimed to establish a sulfidogenic environment under acidogenic conditions. The effects of pre-acidifying the wastewater over methane production was further assessed through monitoring two methanogenic reactors, i.e., one single-phased system fed with raw sulfate-rich wastewater and one two-phased system fed with acidified wastewater. In all cases anaerobic structured-bed reactors were used as well as thermophilic temperature conditions were applied (55ºC). For the first-phase system, two reactors with different materials were compared: reactor with low density polyethylene cylinders (RAS-PEBD) with five operating steps (13 sub-stages) and another reactor with polyurethane foam cubes (RAS-PU) with four operating steps. The main operational strategies for the optimization of sulfate reduction were the variation of hydraulic retention time (HRT: 6-15 h RAS-PEBD; 12-16 h RAS-PU:), organic loading rate (OLRinfl: 10-20 kg-COD m-3 d-1 - RAS-PEBD; 15-20 kg-COD m-3 d-1 - RAS-PU), sulfate loading rate (SLR: 3.2-16.0 kg-SO4 m-3 d-1 - RAS-PEBD; 4 - 8 kg-SO4 m-3 d-1 RAS-PU), and upflow velocity (Vu: 0.06 - 3.35 m h-1 - RAS-PEBD ; 3.42-7.9 m h-1-RAS-PU). After a long period of biomass adaptation in RAS-PEBD, increasing efficiency patterns and sulfide stripping were observed. Controlling effluent recirculation was the key-factor to improve system performance. The same pattern was not obtained in RAS-PU, which presented performance losses due to clogging-related problems and the subsequent establishment of preferential pathways. The effluent from the first-phase reactor with residual sulfate load rate of less than 7% (OLRefl of 15.12 kg m-3 d-1 and sulfide of 256 mg L-1, sub-step X) was applied to a second-phase methanogenic reactor. Considering the comparison between the methanogenic systems, an initial organic load (OL) of 2.5 g-COD d-1 was set, which was further increased up to 5 g d-1. The start-up of the single-phase reactor presented limitations, requiring the application of lower OL values, in order to require 140 days up to the stabilization of the load of 5 g-COD d-1. In turn, the two-phase system required 102 days and presented higher methane generation rates metano (RMI 1,95 L-CH4 d-1 and RMII 1,76 L-CH4 d-1). Phase separation enabled the generation of an acidified effluent with lower residual sulfate concentrations, leading to higher methane production and low sulfide concentration in the biogas in the two-phase system, when compared to the single phase system.

O tratamento de água residuária rica em sulfato por via de processo anaeróbio é um grande desafio, devido ao potencial de redução do sulfato pela via biológica a sulfeto, o que pode inviabilizar o aproveitamento do biogás e afetar o tratamento por seus efeitos tóxicos e inibitórios. Neste contexto, o presente trabalho investigou a potencial aplicação da separação de fase para minimizar tais problemas de operação. A operação de reator de primeira fase visa estabelecer um ambiente sulfetogênico sob condições acidogênicas. Os efeitos da pré-acidificação da água residuária sobre a produção de metano foram avaliados por meio do monitoramento de dois reatores metanogênicos, um sistema de fase única alimentado com água residuária rica em sulfato e um sistema de duas fases alimentado com água residuária acidificada. Em todos os casos foram utilizados reatores anaeróbios de leito estruturado, aplicada condições termofílica de temperatura (55°C). Para o sistema de primeira fase, dois reatores com diferentes materiais foram comparados: reator com cilindros de polietileno de baixa densidade (RAS-PEBD) com cinco etapas de operação (13 subetapas) e outro reator com cubos de espuma de poliuretano (RAS-PU) com quatro etapas de operação. As principais estratégias operacionais para otimização da redução do sulfato a variação do tempo de detenção hidráulica (TDH: 6-15 h RAS-PEBD; 12 - 16 h RAS-PU ), carga orgânica volumétrica (COVafl: 10 - 20,0 kg-DQO m-3 d-1 - RAS-PEBD; 15 - 20 kg-DQO m-3 d-1 - RAS-PU), carga de sulfato volumétrica (CSV: 3,2-16,0 kg-SO4 m-3 d-1 - RAS-PEBD; 4 - 8 kg-SO4 m-3 d-1 - RAS-PU) e velocidade ascensional (Va: 0,06 3,35 m h-1 - RAS-PEBD; 3,42 7,9 m h-1 - RAS-PU). Após longo período de adaptação da biomassa no RAS-PEBD, verificou-se o aumento da eficiência e stripping do sulfeto. A recirculação controlada do efluente foi um fator chave para melhoria do sistema. O mesmo não foi obtido em RAS-PU, apresentando perda de desempenho devido a problemas de colmatação e subsequente aparecimento de vias preferenciais. O efluente do reator de primeira fase com carga de sulfato residual menor que 7% (COVefl de 15,12 kg-DQO m-3d-1 e sulfeto de 256 mg L-1, subetapa X) foi aplicado em reator metanogênico de segunda fase (RMI). Considerando a comparação entre os sistemas metanogênicos, fixou-se uma carga orgânica (CO) inicial de 2,5 g-DQO d-1, sendo aumentada até 5 g d-1. A partida do reator de fase única apresentou limitações, requerendo aplicação de baixos valores de CO, o que demandou 140 dias até a estabilização para a carga de 5 g-DQO d-1. Por sua vez, o sistema com duas fases necessitou de 102 dias e apresentou maior geração de metano (RMI 1,95 L-CH4 d-1 e RMII 1,76 L-CH4 d-1). A separação de fases permitiu a geração de efluente acidificado com menores concentrações de sulfato residual, resultando em maior produção de metano e reduzida concentração de sulfeto no biogás no sistema de duas fases, quando comparado ao sistema de fase única. / The treatment of sulfate-rich wastewater via anaerobic processes is challenging, due to the potential biological sulfate reduction to sulfide, which limits biogas use and affect treatment performance due to toxic and inhibitory effects. In this context, this study investigated the potential application of phase separation to minimize such operating problems. The operation of the first-stage reactor aimed to establish a sulfidogenic environment under acidogenic conditions. The effects of pre-acidifying the wastewater over methane production was further assessed through monitoring two methanogenic reactors, i.e., one single-phased system fed with raw sulfate-rich wastewater and one two-phased system fed with acidified wastewater. In all cases anaerobic structured-bed reactors were used as well as thermophilic temperature conditions were applied (55ºC). For the first-phase system, two reactors with different materials were compared: reactor with low density polyethylene cylinders (RAS-PEBD) with five operating steps (13 sub-stages) and another reactor with polyurethane foam cubes (RAS-PU) with four operating steps. The main operational strategies for the optimization of sulfate reduction were the variation of hydraulic retention time (HRT: 6-15 h RAS-PEBD; 12-16 h RAS-PU:), organic loading rate (OLRinfl: 10-20 kg-COD m-3 d-1 - RAS-PEBD; 15-20 kg-COD m-3 d-1 - RAS-PU), sulfate loading rate (SLR: 3.2-16.0 kg-SO4 m-3 d-1 - RAS-PEBD; 4 - 8 kg-SO4 m-3 d-1 RAS-PU), and upflow velocity (Vu: 0.06 - 3.35 m h-1 - RAS-PEBD ; 3.42-7.9 m h-1-RAS-PU). After a long period of biomass adaptation in RAS-PEBD, increasing efficiency patterns and sulfide stripping were observed. Controlling effluent recirculation was the key-factor to improve system performance. The same pattern was not obtained in RAS-PU, which presented performance losses due to clogging-related problems and the subsequent establishment of preferential pathways. The effluent from the first-phase reactor with residual sulfate load rate of less than 7% (OLRefl of 15.12 kg m-3 d-1 and sulfide of 256 mg L-1, sub-step X) was applied to a second-phase methanogenic reactor. Considering the comparison between the methanogenic systems, an initial organic load (OL) of 2.5 g-COD d-1 was set, which was further increased up to 5 g d-1. The start-up of the single-phase reactor presented limitations, requiring the application of lower OL values, in order to require 140 days up to the stabilization of the load of 5 g-COD d-1. In turn, the two-phase system required 102 days and presented higher methane generation rates metano (RMI 1,95 L-CH4 d-1 and RMII 1,76 L-CH4 d-1). Phase separation enabled the generation of an acidified effluent with lower residual sulfate concentrations, leading to higher methane production and low sulfide concentration in the biogas in the two-phase system, when compared to the single phase system.