Organic methods development has long dictated the molecular scaffolds available to the pharmaceutical and fine chemical synthesis industries. Photoredox catalysis has emerged as a powerful platform to enable novel reactivity with visible light irradiation through triplet sensitization and single-electron transfer. New methods involving radical intermediates are now readily accessible from countless starting materials through the application of these catalysts. Much of my work has utilized established photoredox platforms to enable both nickel catalyzed remote cross-coupling of primary amines via 1,5 hydrogen-atom transfer (HAT) and formal [3+2] synthesis of γ-lactams through triplet sensitization. My further work focuses on the application of ligand-to-metal charge transfer catalysis with cupric chloride and ferric chloride salts towards the alkylation of alkanes through the catalytic generation of chlorine radical to enable HAT. These studies expand photoredox catalysis to inner sphere mechanisms with abundant base-metal salts to enable redox chemistry at reduced electrochemical potentials.

No description available.

The objectives of this study were to (1) determine an intermittent aeration strategy that could be used to conserve nitrogen (N) via nitrification in dairy manure, (2) determine the effect of recycled flush water on the bio-availability of N during nitrification, and (3) determine effective and economical dosages of chemicals to remove phosphorus (P) from liquid dairy manure. Intermittent aeration strategies, defined in terms of time the aerator is on and off (ON h:OFF h), could be used to conserve N in dairy manure. Testing of four treatments (continuous aeration [100%], 1h:0.33h [75%], 1h:0.67h [60%], and 1h:1h [50%]) showed that only treatments using air provided for 100% and 75% of the time could support nitrification. The 100% and 75% aeration treatments conserved an average of 38% and 25% of influent total ammonia nitrogen (TAN) as nitrite-N+nitrate-N, respectively. Less than 2% of influent TAN was conserved using 60% and 50% treatments. The effect of manure handling technique on N bioavailability and nitrification was tested using flushed and scraped dairy manure. Nitrification was inhibited in scraped manure. Four aluminum- and iron-based salts and five cationic polyacrylamide polymers were evaluated for P removal using jar tests. Ferric chloride (FeCl3·6H2O), aluminum sulfate (Al2[SO4]3·13H2O, alum), and Superfloc 4512 were selected for further study. Polymer addition enhanced floc size and improved P removal. Treatment of manure (0.89% total solids) from Tank 2 at Virginia Tech's dairy using either FeCl3 or alum in combination with polymer resulted in more than 90% P removal. Chemical treatment and transport of P-rich sludge from a 2,270 cubic meter storage tank would result in an estimated 40% cost savings over transport of the entire manure volume offsite for land application elsewhere. The manure treatment strategies tested provide some solutions to dairy farmers regarding adjustment of N:P ratios so that manure can be applied to meet nutrient needs of crops while adhering to regulations set forth by nutrient management plans. / Master of Science

Effective coagulation is critical to the production of safe, potable drinking water, but variations in the chemical composition of source water can present challenges in achieving targeted contaminant removal and predicting coagulation outcomes. A critical literature review describes factors affecting the hydrolysis reactions of metal salt coagulants and the resulting precipitates. Properties of two key contaminants, turbidity and natural organic matter (NOM), are explored in the context of removal during coagulation, and the influence of co-occurring ions is described. While it is apparent that NOM character determines the minimum achievable organic carbon residual, the effects of water quality—including pH, NOM character and concentration, and concentrations of synergistic and competitive ions—on overall coagulation efficacy and NOM removal may be underestimated. An experimental research plan was devised to investigate the influence of water quality in coagulation and provide data to support the development of a predictive coagulation model. NOM is capable of interfering with ferric iron hydrolysis and influencing the size, morphology, and identity of precipitates. Conversely, calcium is known to increase the size and aggregation of Fe3+ precipitates and increase surface potential, leading to more effective coagulation and widening the pH range of treatment. Experiments and modeling were conducted to investigate the significance of the Fe/NOM ratio and the presence of calcium in coagulation. At the high Fe/NOM ratio, sufficient or excess ferric hydroxide was available for NOM removal, and coagulation proceeded according to expectations based upon the literature. At the low Fe/NOM ratio, however, NOM inhibited Fe3+ hydrolysis, reduced zeta potential, and suppressed the formation of filterable Fe flocs, leading to interference with effective NOM removal. In these dose-limited systems, equilibrating NOM with 1 mM Ca2+ prior to dosing with ferric chloride coagulant increased the extent of Fe3+ hydrolysis, increased zeta potential, decreased the fraction of colloidal Fe, and improved NOM removal. In dose-limited systems without calcium, complexation of Fe species by NOM appears to be the mechanism by which coagulation is disrupted. In systems with calcium, data and modeling indicate that calcium complexation by NOM neutralizes some of the negative organic charge and minimizes Fe complexation, making Fe hydrolysis species available for growth and effective coagulation. Experiments were conducted to investigate the influence of aqueous silica and pH on the removal of natural organic matter (NOM) by coagulation with ferric chloride. Samples with preformed ferric hydroxide were also compared to samples coagulated in situ to assess the role of coprecipitation. The moderate (10 mg/L) and high (50 mg/L) SiO2 concentrations both demonstrated interference with NOM removal at pH 6.5-7.5. In turn, NOM at 2 mg/L as DOC interfered with silica sorption at the moderate silica level and in samples with preformed ferric hydroxide at the high silica level. The combination of NOM and high silica led to decreases in DOC sorption and unexpected increases in silica sorption in the coprecipitated samples. The fraction of colloidal Fe passing a 0.45-μm filter also increased in the coprecipitated samples with both NOM and high silica. It is hypothesized that the combination of NOM and high silica synergistically interfered with Fe precipitation and particle growth processes, with NOM having the greater effect at lower pH and shorter reaction times, and silica exerting greater influence at higher pH and longer reaction time. Direct competition for surface sites and electrostatic repulsion were also influential. An overall goal for this research was the development of a quantitative coagulation model. Previous attempts to model coagulation have been limited by the inherent complexities of simultaneously predicting ligand sorption, metal complexation, floc surface charge, and particle removal. A diffuse layer (DLM) surface complexation model was formulated to simultaneously predict sorption of NOM and other key species, including silica, calcium, and carbonate alkalinity. Predictions of surface potential were used to estimate zeta potential and resulting regimes of effective aggregation and turbidity removal. The model provided good predictive ability for data from bench-scale experiments with synthetic water and jar tests of nine U.S. source waters. Under most conditions, the model provides excellent capability for predicting NOM sorption, calcium sorption, and particle destabilization and adequate capability for predicting silica sorption. Model simulations of hypothetical scenarios and experimental results help to explain practical observations from the literature. The DLM can be optimized to site-specific conditions and expanded to include sorption of additional species, such as arsenic. / Ph. D.

O presente estudo visou investigar e monitorar a remoção de cistos de Giardia spp. e oocistos de Cryptosporidium spp. em processos combinados (anaeróbio-físico-químico) de uma estação de tratamento de esgoto (ETE), composta por tratamento preliminar, reator UASB (escala piloto) seguido de coagulação, floculação e sedimentação (equipamento jarteste em escala de bancada) ou coagulação, floculação e flotação por ar dissolvido – FAD (equipamento flotateste em escala de bancada), e verificar a ocorrência desses protozoários no lodo do reator UASB e do processo de sedimentação. Verificou-se a qualidade das amostras a partir de variáveis físicas e químicas, e pela detecção de microrganismos indicadores – E.coli e coliformes totais. Os métodos de detecção de protozoários se basearem nas etapas de concentração (tripla centrifugação ou filtração em membrana seguida de tripla centrifugação); purificação por separação imunomagnética (IMS); detecção por reação de imunofluorescência direta (RID). As recuperações de cistos e oocistos variaram de 25,9 a 41,2% e de 5,8 a 22,2%, respectivamente. Foram detectadas significativas quantidades de cistos de Giardia spp. em 100% das amostras de esgoto analisadas, com concentrações médias no esgoto bruto de 4,27x103 cistos.L-1 na etapa 1 e 3 (TDH de 12 horas) e 3,18x103 cistos.L-1 na etapa 2 (TDH de 8 horas). No esgoto tratado após processo de sedimentação as concentrações médias foram 327,4 cistos.L-1 no tratamento utilizando coagulante cloreto férrico e 3,8 cistos.L-1 utilizando tanino, ambos na etapa 1, já na etapa 2 esses mesmos tratamentos apresentaram efluente com concentrações médias de 211,6 e 29,6 cistos.L-1, respectivamente. No efluente tratado após o processo de flotação as concentrações médias de cistos de Giardia spp. foram de 8,0 cistos.L-1 com coagulante cloreto férrico e 1,5 cistos.L-1 com PAC, na etapa 3, e de 7,0 cistos.L-1 com cloreto férrico e 5,3 cistos.L-1 com PAC na etapa 2. Os oocistos de Cryptosporidium spp. foram detectados com menor frequência nas amostras de esgoto, como concentrações médias de 18,7 oocistos.L-1 no esgoto bruto nas etapas 1 e 3 e de 23,0 oocistos.L-1 na etapa 2. As eficiências de remoção de cistos de Giardia spp. dos tratamentos combinados variaram de 1,1 log a 3,4 log. O lodo do reator UASB e o lodo da etapa de sedimentação apresentaram altas quantidades de (oo)cistos, evidenciando a tendência de remoção de (oo)cistos por processos físicos como a sedimentação. O processo de flotação foi mais eficiência que o processo de sedimentação na remoção de (oo)cistos, mas devido à pequena quantidade de lodo não foi possível quantificar os (oo)cistos no lodo flotado. / The aim of study was to investigate and monitor the removal of Giardia spp. cysts and Cryptosporididum spp. oocysts through different combined treatment (anaerobic/physicalchemical) of a sewage treatment plant (STP), consisted of preliminary treatment, UASB reactor (pilot scale) followed by sedimentation (jartest equipment in bench scale) or by dissolved air flotation (flotatest equipment in bench scale). Moreover, it was investigated the occurrence of protozoa in the sludge of the UASB reactor and sedimentation process. It was analyzed the quality of the samples through physical and chemical variables and detection of indicator microorganisms – E. coli and total coliforms. The detection methods of protozoa were based on steps of concentration (triple centrifugation or membrane filtration followed by triple centrifugation); purification by immunomagnetic separation (IMS); immunofluorescence assay (IFA). The recovery of cysts and oocysts ranged from 25,9 to 41,2% and from 5,8 to 22,2%, respectively. Significant quantities of Giardia spp. cysts were detected in 100% of the analyzed wastewater samples, with mean concentration of 4,27x103 cysts.L-1 in raw watewater in step 1 and 3 (THD 12 hours) and 3,18x103 cysts.L-1 in step (THD 8 hours). In treated wastewater after the sedimentation process the mean concentration were 327,4 cysts.L-1 with ferric chloride and 3,8 cysts.L-1 with tannin, both in step 1, and in step 2 the same treatments were with mean concentration of 211,6 and 29,6 cysts.L-1, respectively. In treated wastewater after flotation process the mean concentration were 8,0 cysts.L-1 with ferric chloride and 1,5 cysts.L-1 with PAC in step 3 and 7,0 cysts.L-1 with ferric chloride and 5,3 cysts.L-1 with PAC in step 2. The oocysts of Cryptosporidium spp. were detected less often in the wastewater samples, with mean concentration of 18,7 oocysts.L-1 in raw wastewater in steps 1 and 3 and of 23,0 oocysts.L-1 in step 2. The overall removal for Giardia spp. was on average of 1,1 to 3,4 log. The sludge from UASB reactor and sedimentation process presented high quantities of (oo)cysts, implying the tendency of these systems to remove (oo)cysts by its physical processes such as sedimentation. The flotation process was more eficiente than the sedimentation process in the (oo)cysts removal, but due to the small amount of sludge was not possible to quantify the (oo)cysts in the float sludge.

Este trabalho visou avaliar a remoção de fósforo solúvel e total, carga orgânica, sulfetos e sólidos num esgoto doméstico fraco, ao qual se adicionou como coagulante o cloreto férrico, atravessando o manto de lodo de um tratamento anaeróbio UASB. A ETE Ribeirão Pires, aonde este estudo foi desenvolvido, conta com 4 reatores com capacidade para tratar 70 L/s, dos quais 2 foram utilizados, num deles (reator B) foram dosados 25 e 50 mg FeCl3/L e no outro (reator C) não houve dosagem, servindo como referência. Em cada uma das fases, foram realizadas 20 amostragens para DQO, fósforo total e solúvel, alcalinidade, pH e sólidos suspensos. Para DBO5,20ºC, sulfetos, sólidos totais e sedimentáveis foram obtidos 10 valores em cada dosagem. Os pontos de coleta foram: esgoto bruto e esgoto tratado dos reatores B e C. Foram coletadas amostras em 3 alturas do manto de lodo e realizadas as séries de sólidos em cada dosagem. Quanto à secagem desse lodo, os itens ciclo de desaguamento, espessura da camada e teor de sólidos foram comparados em descartes aos leitos de secagem da ETE. Da avaliação, pode-se concluir que a adição de cloreto férrico gera aumento considerável de remoção de carga orgânica (de 55% para 73% da DQO e de 63% para 82% da DBO5,20ºC, com 50 mg FeCl3/L). Quanto ao fósforo, as eficiências foram menores, sendo mais notadas nos ortofosfatos (de 28% para 36% de fósforo total e de 0% para 59% de solúvel com 50 mg FeCl3/L). Com relação ao lodo gerado, houve diminuição do ciclo de secagem e do volume da torta (do lodo com adição) em relação àquela gerada no reator sem adição de cloreto férrico. O manto de lodo se mostrou mais espesso e com menor concentração de sólidos no reator com aplicação de cloreto férrico, sugerindo uma tendência a maior perda de sólidos com o efluente clarificado. / The presented work intended to evaluate the removal of soluble and total phosphorus, organic matter (BOD5,20ºC and COD), sulfides and solids in a weak domestic wastewater, to which it was added ferric chloride as precipitant, crossing an UASB sludge blanket. The Ribeirão Pires wastewater treatment plant, where this study took place, is composed by 4 UASB reactors. In one of them (reactor B), 25 and 50 mg FeCl3/L were dosed, and in another (reactor C) there were no dosage, serving as a reference. In each of the stages, it had been carried through around 20 samplings for COD, total and soluble phosphorus, alkalinity, pH and suspended solids. For BOD5,20ºC, total sulfides, total solids and settleable solids it had been gotten 10 values in each dosage. The collection points had been: raw wastewater and treated wastewater from reactors B and C. Samples in 3 heights of the sludge blanket had been collected and carried through the solid series analysis in each dosage. About the sludge dewatering, items as dewatering period, layer thickness and total solids had been compared in some discharges to the drying beds. From this evaluation, it can be concluded that the ferric chloride addition generates an increase of organic matter removal (from 55% to 73% of the COD and from 63% to 82% of the BOD5,20ºC, with 50 mg FeCl3/L). For phosphorus, the removal efficiencies had been lower, more noticed in the soluble portion (from 28% to 36% of total and from 0% to 59% of soluble phosphorus at 50 mg FeCl3/L). Improvement in the dewatering capacity and in sludge cake volume were also noticed. The sludge blanket showed thicker and with a lower solid concentration in the reactor with ferric chloride application, suggesting a trend to solids loss in the clarified effluent.

Este trabalho teve como propósito investigar a cinética de floculação de água bruta com baixa turbidez, utilizando o sulfato de alumínio (Al2(SO4)3o18H2O) e o cloreto férrico (FeCl3o6H2O) como coagulantes. Os resultados experimentais foram obtidos em ensaios de \"jar test\". A água bruta utilizada nos ensaios foi preparada em laboratório, simulando um manancial superficial eutrofizado contendo células da cianobactéria Microcystis aeruginosa. Foram testadas 5 dosagens distintas de cada coagulante, 3 valores de G, 2 valores de TAS e 12 tempos de floculação. Utilizou-se a turbidez como medida principal de avaliação dos resultados experimentais. O valor de turbidez inicial (N0) foi corrigido, levando-se em consideração o acréscimo de turbidez em função das dosagens de coagulante. Determinou-se que as dosagens mais efetivas, em termos de remoção de turbidez, foram 20 mg.L-1 para o sulfato de alumínio e 40 mg.L-1 para o cloreto férrico (ambas expressas como massa de coagulante). Para ambos os coagulantes, constatou-se que G = 20 s-1 e TAS = 27 m3.m-2.dia-1 resultaram nas melhores eficiências de remoção de turbidez. Verificou-se também a variação do potencial zeta em função das dosagens de coagulante. Observou-se que o aumento da dosagem de coagulante leva à redução do potencial zeta, aproximando-o do ponto isoelétrico. Porém, o ponto isoelétrico não necessariamente coincide com a melhor eficiência em termos de remoção de turbidez. Com base nos resultados experimentais, foi proposta uma modificação ao modelo clássico da cinética de floculação de suspensões coloidais. Nesta, foi incluso um segundo termo referente à ruptura de flocos (quebra irreversível). O ajuste do modelo proposto foi obtido através de procedimentos de iteração numérica computacional com a função \"Solver\" do programa Microsoft Excel®. Foram calculados os valores das constantes KA, KB e KC do modelo proposto. Amostras do lodo gerado nos ensaios de cinética de floculação foram caracterizadas visualmente através de microscopia eletrônica de varredura (MEV). / The purpose of this work was to investigate flocculation kinetics of low-turbidity raw water, using aluminum sulfate (Al2(SO4)3o18H2O) and ferric chloride (FeCl3o6H2O) as coagulants. Experimental results were obtained in jar tests. Raw water used in the jar tests was prepared in laboratory, simulating a eutrophic natural water source containing cells of the cyanobacteria Microcystis aeruginosa. 5 different coagulant doses were tested for each coagulant, 3 G values, 2 SLR values and 12 flocculation times. Turbidity was selected as the major parameter for experimental results analysis. Initial turbidity values (N0) were corrected taking into account turbidity increase due to coagulant dosing. In terms of turbidity removal, it was determined that the most effective dosage for aluminum sulfate was 20 mg.L-1, and for ferric chloride, 40 mg.L-1 (both expressed as coagulant mass). For both coagulants, it was found that G = 20 s-1 and SLR = 27 m3.m-2.day-1 resulted in the best turbidity removal efficiencies. Zeta potential variation, due to coagulant dosing, was also verified. It was noted that increasing coagulant dosing led to zeta potential reduction, bringing it closer to the isoelectric point. However, the isoelectric point does not necessary coincides with the best turbidity removal efficiency. Based on the experimental results, it was proposed a modification to the classic colloidal suspension flocculation kinetics model. In this modification, a second term regarding floc rupture (irreversible breakage) was included. Through computer numeric iteration using Microsoft Excel®\'s \"Solver\" function, the proposed model adjustment was obtained. Kinetics constants KA, KB e KC values, from the proposed model, were calculated. Sludge samples, generated during flocculation kinetics tests, were visually characterized through scanning electronic microscopy (SEM).

soldagem de aços inoxidáveis duplex AID SAF 2205 utilizando o processo Metal Active Gas (MAG) ainda tem poucos dados e referências, estes aços são conceituados devido ao seu equilíbrio entre resistência mecânica e à corrosão, resultado de sua microestrutura composta por austenita e ferrita. A soldagem dos aços inoxidáveis duplex exige um controle de aporte térmico, da composição química do metal de adição e gás de proteção. Mínimas mudanças em parâmetros e composição dos consumíveis podem afetar diretamente a estrutura formada na região da solda. Neste trabalho, o objetivo foi estudar a influência da utilização do processo de soldagem MAG com diferentes energias aplicadas ao AID SAF 2205, sobre a resistência à corrosão das amostras resultantes. Foram usados quatro valores de energias de soldagem, entre 0,6 e 1,1 kJ/mm, sendo a maior energia limitada à espessura das chapas, que era de 5 mm. Quando foi analisada a microestrutura formada na região da solda, a quantificação de ferrita na zona afetada pelo calor apresentou uniformidade nas amostras, independendo da energia de soldagem. Contudo, a quantidade de ferrita no metal de solda diminuiu à medida que a energia aumentou. A precipitação de nitretos de cromo foi observada no interior de alguns grãos de ferrita e/ou próximo a regiões com austenita secundária intragranular. Os perfis de microdureza Vickers não apresentaram nenhum valor acima de 300 HV, e nenhum comportamento diferenciado de acordo com área de indentação. A resistência à corrosão não apresentou mudanças consideráveis, o metal base e as regiões da solda nas quatro condições se comportaram de forma muito similar. Os ensaios de imersão em cloreto férrico, seguindo a ASTM G48, permitiram observar a formação de pites, mas a quantidade e densidade destes não pode ser associada a uma região da solda específica ou variação de energia de soldagem. Os valores de parâmetros eletroquímicos, OCP, ECORR, e EPIT, após os ensaios de polarização potenciodinâmica de acordo com a ASTM G5, tiveram pouca variação, mostrando um comportamento em corrosão similar para o metal base e para os metais de solda das quatro diferentes condições de energia de soldagem empregadas. / Welding of AID SAF 2205 duplex stainless steels using the Metal Active Gas (MAG) process still has few data and references, these steels are conceptualized due to their balance between mechanical resistance and corrosion, resulting from their microstructure composed of austenite and ferrite. The welding of duplex stainless steels requires a control of the thermal input, the chemical composition of the addition metal and the shielding gas. Minimal changes in parameters and composition of consumables will directly affect the structure formed in the region of the weld. In this work, the objective was to study the influence of the MAG welding process with different energies applied to AID SAF 2205, on the corrosion resistance of the resulting samples. Four values of welding energies were used, between 0.6 and 1.1 kJ / mm, with the greatest energy limited to the thickness of the plates, which was 5 mm. When the microstructure formed in the region of the weld was analyzed, the quantification of ferrite in the zone affected by the heat showed uniformity in the samples, independent of the welding energy. However, the amount of ferrite in the weld metal decreased as the energy increased. The precipitation of chromium nitrides was observed in the intermetallic was associated with grain boundaries α / γ, inside some ferrite grains, close to regions with secondary intragranular austenite. The Vickers microhardness profiles showed no value above 300 HV, and no behavior differed according to the indentation area. The corrosion resistance did not change considerably, the base metal and the regions of the weld in the four conditions behaved very similarly. Ferric chloride immersion assays, following ASTM G48, allowed to observe the formation of pites, but the amount and density thereof can not be associated with a specific weld region or weld energy variation. The values of electrochemical parameters, OCP, ECORR, and EPIT, after the potentiodynamic polarization tests according to ASTM G5, showed little variation, showing a similar corrosion behavior for the base metal and the solder metals of the four Different welding energy conditions employed.

Este trabalho teve como propósito investigar a cinética de floculação de água bruta com baixa turbidez, utilizando o sulfato de alumínio (Al2(SO4)3o18H2O) e o cloreto férrico (FeCl3o6H2O) como coagulantes. Os resultados experimentais foram obtidos em ensaios de \"jar test\". A água bruta utilizada nos ensaios foi preparada em laboratório, simulando um manancial superficial eutrofizado contendo células da cianobactéria Microcystis aeruginosa. Foram testadas 5 dosagens distintas de cada coagulante, 3 valores de G, 2 valores de TAS e 12 tempos de floculação. Utilizou-se a turbidez como medida principal de avaliação dos resultados experimentais. O valor de turbidez inicial (N0) foi corrigido, levando-se em consideração o acréscimo de turbidez em função das dosagens de coagulante. Determinou-se que as dosagens mais efetivas, em termos de remoção de turbidez, foram 20 mg.L-1 para o sulfato de alumínio e 40 mg.L-1 para o cloreto férrico (ambas expressas como massa de coagulante). Para ambos os coagulantes, constatou-se que G = 20 s-1 e TAS = 27 m3.m-2.dia-1 resultaram nas melhores eficiências de remoção de turbidez. Verificou-se também a variação do potencial zeta em função das dosagens de coagulante. Observou-se que o aumento da dosagem de coagulante leva à redução do potencial zeta, aproximando-o do ponto isoelétrico. Porém, o ponto isoelétrico não necessariamente coincide com a melhor eficiência em termos de remoção de turbidez. Com base nos resultados experimentais, foi proposta uma modificação ao modelo clássico da cinética de floculação de suspensões coloidais. Nesta, foi incluso um segundo termo referente à ruptura de flocos (quebra irreversível). O ajuste do modelo proposto foi obtido através de procedimentos de iteração numérica computacional com a função \"Solver\" do programa Microsoft Excel®. Foram calculados os valores das constantes KA, KB e KC do modelo proposto. Amostras do lodo gerado nos ensaios de cinética de floculação foram caracterizadas visualmente através de microscopia eletrônica de varredura (MEV). / The purpose of this work was to investigate flocculation kinetics of low-turbidity raw water, using aluminum sulfate (Al2(SO4)3o18H2O) and ferric chloride (FeCl3o6H2O) as coagulants. Experimental results were obtained in jar tests. Raw water used in the jar tests was prepared in laboratory, simulating a eutrophic natural water source containing cells of the cyanobacteria Microcystis aeruginosa. 5 different coagulant doses were tested for each coagulant, 3 G values, 2 SLR values and 12 flocculation times. Turbidity was selected as the major parameter for experimental results analysis. Initial turbidity values (N0) were corrected taking into account turbidity increase due to coagulant dosing. In terms of turbidity removal, it was determined that the most effective dosage for aluminum sulfate was 20 mg.L-1, and for ferric chloride, 40 mg.L-1 (both expressed as coagulant mass). For both coagulants, it was found that G = 20 s-1 and SLR = 27 m3.m-2.day-1 resulted in the best turbidity removal efficiencies. Zeta potential variation, due to coagulant dosing, was also verified. It was noted that increasing coagulant dosing led to zeta potential reduction, bringing it closer to the isoelectric point. However, the isoelectric point does not necessary coincides with the best turbidity removal efficiency. Based on the experimental results, it was proposed a modification to the classic colloidal suspension flocculation kinetics model. In this modification, a second term regarding floc rupture (irreversible breakage) was included. Through computer numeric iteration using Microsoft Excel®\'s \"Solver\" function, the proposed model adjustment was obtained. Kinetics constants KA, KB e KC values, from the proposed model, were calculated. Sludge samples, generated during flocculation kinetics tests, were visually characterized through scanning electronic microscopy (SEM).

The combination of moving bed biofilm reactors and membrane bioreactors (MBBR-MR) can compensate for the drawbacks of both of these systems and further increase their acceptance and application in wastewater treatment industries. Despite the potential benefits of a MBBR-MR technology there has only been limited study of this configuration. The present study consisted of an overall assessment of the performance of a combined MBBR-MR system under high and low loading rates. Since colloidal matter in mixed liquor suspended solid (MLSS) is considered as one of the important contributors to membrane fouling, pre-treatment of membrane feed by coagulation was investigated for improving membrane performance. The performance of the MBBR-MR was assessed based on its chemical oxygen demand (COD) removal efficiency and membrane fouling mechanisms. The study was carried out using pilot-scale MBBR and bench-scale batch membrane filtration setups (Millipore Inc. Bedford, MA). The pilot MBBR had a working volume of 1.8 m3 and a 30% carrier fill fraction. The MBBR was operated with loading rates of 160 ± 44 g/m2/d (hydraulic residence time (HRT) of 4.6 h) and 223 g/m2/d (HRT of 2.6 h). The MBBR feed was obtained from a starch recovery line in a potato chip processing factory. The carriers were mixed by coarse bubble aeration and the dissolved oxygen (DO) was maintained above 2 mg/l. Preliminary jar test trials (based on turbidity removal) were performed in order to obtain an optimal dosage of coagulants for subsequent ultrafiltration (UF) tests. The efficiency of three coagulants (alum, ferric chloride and a blend of polyaluminum chloride and polyamine) was evaluated. The membranes were composed of polyethersulfone (PES) and had a pore size of 0.05 microns. The results of this study indicate that the combination of MBBR with membrane filtration can be operated at relatively high loading rates to yield a constant high quality permeate that is suitable for water reuse purposes. Fouling of the membrane by the wastewater was found to be substantially reduced by treatment with the MBBR. The reversible and irreversible fouling of the MBBR effluent were 56 and 63%, respectively, of that observed with the raw wastewater. The MBBR Loading-rate was found to affect treatment efficiency of the MBBR-MR and membrane performance. Operation under the elevated loading-rate conditions HRT = 2.6 hours) resulted in an increase in the irreversible fouling of the membranes (60% on average). The addition of all the coagulants in this study was found to decrease the fouling of the membrane. However, the extent of the pre-coagulation effect on membrane fouling was found to strongly depend on the type and dosage of the coagulant and the MBBR effluent characteristics. All the coagulants were effective in decreasing membrane fouling at their optimal dosages which was determined in preliminary jar tests. Ferric chloride performed the best as a pretreatment coagulant compared to alum (Aluminum sulfate) and the coagulant blend with reductions in both reversible and irreversible fouling (43-86% and 51-71%, respectively) and increased consistency (in decreasing fouling) as compared to the other coagulants. Alum had no effect on irreversible fouling and the coagulant blend significantly increased irreversible fouling in some trials (up to 196% or by a factor of 3 when overdosed). Additionally, alum and the blend were, on average, 29% and 7%, less effective than ferric chloride in reducing reversible fouling under the conditions and dosages tested.