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Influência da velocidade de entrada na zona de contato na eficiência de clarificação de unidades retangulares de flotação por ar dissolvido aplicado no tratamento de águas para abastecimento / Influence of the velocity in the contact zone entrance on the clarification efficiency of rectangular dissolved air flotation units applied to water treatment to supplyMaia, Kisner Anderson 07 October 2010 (has links)
A flotação por ar dissolvido (FAD) é reconhecida atualmente como técnica eficiente para a etapa de clarificação em sistemas de tratamento de água para abastecimento. Diversos estudos vêm sendo realizados para aprimoramento dessa técnica e das características físicas das unidades FAD. Seguindo essa tendência, o presente trabalho teve como objetivo estudar os efeitos da velocidade na entrada da zona de contato (\'V IND.EZC\') na eficiência de clarificação de unidades retangulares FAD. Para o presente estudo foi utilizada água sintética preparada através da adição de 1,0 mg/L de ácido húmico e 8,5 mg/L de caulinita, a qual foi coagulada com sulfato de alumínio. A pesquisa foi dividida em duas fases: FASE I - com o emprego do Flotateste foram determinadas as dosagens adequadas de coagulante, o pH adequado de coagulação com a medição do potencial zeta das partículas (PZ), o gradiente médio de velocidade para floculação e o tempo médio para floculação para o tratamento da água sintética em estudo; FASE II - utilizando unidade FAD em escala piloto foram realizados ensaios para diferentes variações na altura da entrada da zona de contato (he) da câmara de flotação de forma a se obter diferentes valores de \'V IND.EZC\'. Nesta fase foram investigadas duas diferentes condições de coagulação as quais forneceram bons resultados por flotação: 1ª condição, aplicação de 42,5 mg/L de \'AL IND.2\'(\'SO IND.4\')IND.3\' e pH de 6,35 \'+ OU -\' 0,05 na qual resultou em PZ positivo em torno de +10 mV e para 2ª condição, aplicação de 22,5 mg/L de \'AL IND.2\'(\'SO IND.4\')IND.3\' e pH de 6,40 \'+ OU -\' 0,05 na qual resultou em PZ próximo de 0 mV. Os ensaios foram monitorados e comparados entre si os valores residuais de turbidez e cor aparente. Em todos os ensaios as taxas de aplicação superficial foram mantidas em faixas estreitas de verificando-se que os melhores resultados residuais dos parâmetros monitorados foram obtidos para a 1ª condição de estudo com valores de 0,66 NTU de turbidez e cor aparente igual a 2 uC (eficiências de 90,5 e 93,9% respectivamente). Os resultados demonstraram que para a faixa de valores de \'V IND.EZC\' entre 62,2 e 12.432,4 m/h pouca influência desse parâmetro foi observada na eficiência do processo de clarificação por flotação para ambas as condições de coagulação investigadas. Entretanto, a faixa de valores de \'V IND.EZC\' entre 124,3 e 180,2 m/h forneceram as melhores condições de flotação. Portanto, sugere-se tal faixa de valores como subsídio ao projeto de sistemas de flotação constituído pelas características apresentadas nesta pesquisa. / Dissolved air flotation (DAF) is currently recognized as an efficient technique for water clarification in water treatment systems. Several studies have been conducted to improve this technique and the physical characteristics of DAF units in order to constantly improve their performance. Following this trend, the aim of this research was to evaluate the effects of the velocity in the contact zone entrance on the clarification efficiency of rectangular DAF units. A DAF pilot plant fed with synthetic water prepared by adding 1.0 mg/L of humic acid and 8.5 mg/L of kaolin, and coagulated with aluminum sulfate was used. The research was divided into two phases: I) by using a laboratory scale DAF unit (Flotatest) the optimal coagulation, flocculation, and flotation conditions for the synthetic water previously described were investigated; and II) by using a DAF pilot unit tests were performed for different variations in the height of the contact zone entrance (he) of the flotation chamber to obtain different values of velocity in the contact zone entrance. In this phase two different conditions of coagulation were investigated yielding good results: 1st condition: application of 42.5 mg/L of \'AL IND.2\'(\'SO IND.4\')IND.3\' and pH 6.35 \'+ OR -\' 0.05, which resulted in zeta potential of positive particles around +10 mV, and 2nd condition: application of 22.5 mg/L \'AL IND.2\'(\'SO IND.4\')IND.3\' and pH 6.40 \'+ OR -\' 0.05, which resulted in zeta potential of particles near zero. The tests were monitored and the residual values of turbidity and apparent color were compared. In all experiments, the hydraulic surface loadings were kept in narrow bands of values (in the contact zone equal to 180 \'+ OR -\' 4 m/h and in the clarification zone, equal to 184 \'+ OR -\' 4 m/d). It was verified that the best residual results of the parameters monitored were obtained for the 1st condition with 0.66 NTU turbidity and apparent color equal to 2 uC (efficiencies of 90.5 and 93.9%, respectively). The results showed that for the range of values of velocity in the contact zone entrance between 62.2 and 12432.4 m/h little influence of this parameter was observed on the clarification efficiency process by flotation for both coagulation conditions investigated. However, as the range of values between 124.3 and 180.2 m/h provided the best flotation conditions, such a range should be adopted for the designs of rectangular DAF units.
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Influência da velocidade de entrada na zona de contato na eficiência de clarificação de unidades retangulares de flotação por ar dissolvido aplicado no tratamento de águas para abastecimento / Influence of the velocity in the contact zone entrance on the clarification efficiency of rectangular dissolved air flotation units applied to water treatment to supplyKisner Anderson Maia 07 October 2010 (has links)
A flotação por ar dissolvido (FAD) é reconhecida atualmente como técnica eficiente para a etapa de clarificação em sistemas de tratamento de água para abastecimento. Diversos estudos vêm sendo realizados para aprimoramento dessa técnica e das características físicas das unidades FAD. Seguindo essa tendência, o presente trabalho teve como objetivo estudar os efeitos da velocidade na entrada da zona de contato (\'V IND.EZC\') na eficiência de clarificação de unidades retangulares FAD. Para o presente estudo foi utilizada água sintética preparada através da adição de 1,0 mg/L de ácido húmico e 8,5 mg/L de caulinita, a qual foi coagulada com sulfato de alumínio. A pesquisa foi dividida em duas fases: FASE I - com o emprego do Flotateste foram determinadas as dosagens adequadas de coagulante, o pH adequado de coagulação com a medição do potencial zeta das partículas (PZ), o gradiente médio de velocidade para floculação e o tempo médio para floculação para o tratamento da água sintética em estudo; FASE II - utilizando unidade FAD em escala piloto foram realizados ensaios para diferentes variações na altura da entrada da zona de contato (he) da câmara de flotação de forma a se obter diferentes valores de \'V IND.EZC\'. Nesta fase foram investigadas duas diferentes condições de coagulação as quais forneceram bons resultados por flotação: 1ª condição, aplicação de 42,5 mg/L de \'AL IND.2\'(\'SO IND.4\')IND.3\' e pH de 6,35 \'+ OU -\' 0,05 na qual resultou em PZ positivo em torno de +10 mV e para 2ª condição, aplicação de 22,5 mg/L de \'AL IND.2\'(\'SO IND.4\')IND.3\' e pH de 6,40 \'+ OU -\' 0,05 na qual resultou em PZ próximo de 0 mV. Os ensaios foram monitorados e comparados entre si os valores residuais de turbidez e cor aparente. Em todos os ensaios as taxas de aplicação superficial foram mantidas em faixas estreitas de verificando-se que os melhores resultados residuais dos parâmetros monitorados foram obtidos para a 1ª condição de estudo com valores de 0,66 NTU de turbidez e cor aparente igual a 2 uC (eficiências de 90,5 e 93,9% respectivamente). Os resultados demonstraram que para a faixa de valores de \'V IND.EZC\' entre 62,2 e 12.432,4 m/h pouca influência desse parâmetro foi observada na eficiência do processo de clarificação por flotação para ambas as condições de coagulação investigadas. Entretanto, a faixa de valores de \'V IND.EZC\' entre 124,3 e 180,2 m/h forneceram as melhores condições de flotação. Portanto, sugere-se tal faixa de valores como subsídio ao projeto de sistemas de flotação constituído pelas características apresentadas nesta pesquisa. / Dissolved air flotation (DAF) is currently recognized as an efficient technique for water clarification in water treatment systems. Several studies have been conducted to improve this technique and the physical characteristics of DAF units in order to constantly improve their performance. Following this trend, the aim of this research was to evaluate the effects of the velocity in the contact zone entrance on the clarification efficiency of rectangular DAF units. A DAF pilot plant fed with synthetic water prepared by adding 1.0 mg/L of humic acid and 8.5 mg/L of kaolin, and coagulated with aluminum sulfate was used. The research was divided into two phases: I) by using a laboratory scale DAF unit (Flotatest) the optimal coagulation, flocculation, and flotation conditions for the synthetic water previously described were investigated; and II) by using a DAF pilot unit tests were performed for different variations in the height of the contact zone entrance (he) of the flotation chamber to obtain different values of velocity in the contact zone entrance. In this phase two different conditions of coagulation were investigated yielding good results: 1st condition: application of 42.5 mg/L of \'AL IND.2\'(\'SO IND.4\')IND.3\' and pH 6.35 \'+ OR -\' 0.05, which resulted in zeta potential of positive particles around +10 mV, and 2nd condition: application of 22.5 mg/L \'AL IND.2\'(\'SO IND.4\')IND.3\' and pH 6.40 \'+ OR -\' 0.05, which resulted in zeta potential of particles near zero. The tests were monitored and the residual values of turbidity and apparent color were compared. In all experiments, the hydraulic surface loadings were kept in narrow bands of values (in the contact zone equal to 180 \'+ OR -\' 4 m/h and in the clarification zone, equal to 184 \'+ OR -\' 4 m/d). It was verified that the best residual results of the parameters monitored were obtained for the 1st condition with 0.66 NTU turbidity and apparent color equal to 2 uC (efficiencies of 90.5 and 93.9%, respectively). The results showed that for the range of values of velocity in the contact zone entrance between 62.2 and 12432.4 m/h little influence of this parameter was observed on the clarification efficiency process by flotation for both coagulation conditions investigated. However, as the range of values between 124.3 and 180.2 m/h provided the best flotation conditions, such a range should be adopted for the designs of rectangular DAF units.
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Pluoštinių priedų įtaka autoklavinio akytojo betono savybėms / The Influence of Fiberous Additives on the Properties of Autoclaved Aerated ConcreteMikulskis, Donatas 29 June 2007 (has links)
Disertacijoje nagrinėjama pluoštinių priedų įtaka autoklavinio akytojo betono (AAC) savybėms, ištirta pluoštinių priedų korozija šarminėje aplinkoje, nustatyta pluoštinių priedų įtaka AAC formavimo mišiniams, parinkta optimali formavimo mišinių sudėtis, sumaišymo ir pluoštų parametrai. Atlikta pluoštinių priedų hidrofilizacija ir ištirta jos įtaka portlandcemečio hidratacijai bei pluoštų pasiskirstymui AAC matricoje. Nustatytos AAC bandinių su pluoštiniais priedais bandinių fizikinės mechaninės charakteristikos, ištirta pluoštų sąlyčio zona su AAC matrica, nustatyta drėgnio įtaka AAC savybėms ir šalčio atsparumas. Disertacijoje pateikta patobulinta AAC gamybos technologinė schema. / Dissertation analizes the influence of fiberous additives on the properties of autoclaved aerated concrete (AAC). The corrosion of fibers in alkaline medium and the resistance to hydrothermal exposure was investigate, the optimal composition of formation admixtures and its parameters of mixing was selected, optimal quantities and parameters of fibrous admixture was determined, the effect of surface active agents (SAA) used for hydrophilization of fibers on hydration of Portland cement was investigate to. The effect of fibrous admixtures on properties of AAC products (density, macro- and microstructure, reinforcing fibrous admixture – AAC matrix contact zone, compression strength, bending strength, freeze resistance) was determined. A new modernized technological scheme of AAC producing is presented in this dissertation.
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Professional identity adaptation of native English speaking ESL teachers in the state of Qatar Contact ZoneRajabieslami, Natasha January 2017 (has links)
Sachs (2005) argues that a conceptual framework of identity can guide teachers on how to construct their own ideas regarding “how to be”, “how to act”, and “how to understand” their work (p. 15). However, teachers who work in a foreign context may need to adapt their conceptual framework of identity in order to improve the fit between themselves and their workplace. With this thought in mind, the current qualitative, exploratory study is concerned with the professional identity adaptation of a group of ten native English speaking teachers working at two governmental institutes in the state of Qatar. The aim of this study was two-fold: first, to discover what factors affect teachers’ self-perception and professional identity; second, to explore implications for the practice of these native English speaking teachers (NESTs). Research data collected through in-depth semi-structured interviewing and classroom observations revealed that both institutional and intrapersonal factors were involved in the adaptation of the teachers’ professional identity and the teachers’ approaches to adapt their pedagogy. In other words, one of the noticeable features of the teachers’ professional identity adaptation was the conflict between the teachers’ expectations and the realities of the local context (interpersonal conflicts). There was evidence that teachers’ intrapersonal negotiation lead them to develop multiple identities in order to avoid any troubles at the workplace. Consequently, the mismatch between the teachers’ expectations of their professional life and the realities of the local context caused an apparent inconsistency between the teachers’ beliefs and behavior, which was considered to be a form of cognitive dissonance among the teachers. This study provides English teachers who work in a new context with pragmatic information and insights about the professional identity adjustment process. It also heightens their awareness of the possible professional identity transitions that they may go through. The study should help expatriate ESL teachers in the State of Qatar, in particular, to cope with a possible discrepancy between the idealism of their pedagogical and cultural theory, and their perceived reality of classroom practice.
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Hostitelská specifita, diverzita a distribuce malarických parazitů v kontaktní zóně dvou druhů slavíků / Host specificity, diversity and distribution of avian malaria parasites in a contact zone of two nightingale speciesŠíma, Michal January 2011 (has links)
Avian contact zones were suggested to act as barriers to parasite expansions. I studied haemosporidian parasites (genera Plasmodium, Haemoproteus, and Leucocytozoon) of two Nightingale species which meet in a contact zone in Europe. In total 20 lineages of parasites were detected. Surprisingly, all common lineages were shared by the two host species. The parasite prevalence vary between species (Trush Nightingales were more often parasitized than Common Nightingales.) but did not vary to a large extent within zones inside species Parasitemia of the most frequent Haemoproteus LULU1 lineage assessed by Real-Time PCR method did not differ significantly between the two host species. Six out of nine hybrids of the nightingale species were parasitized. Haemosporidian lineages found in hybrids were also frequent in the parental species. In conclusion, the nightingale contact zone seems to have only little (if any) effect on the distribution of haemosporidian parasites.
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Co-shaping the Image of China:Social Interactions at China Shops in Botswana / 中国イメージの共同構築-ボツワナのチャイナショップにおける社会的インタラクション-Zi, Yanyin 23 March 2016 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第19838号 / 地博第194号 / 新制||地||69(附属図書館) / 32874 / 京都大学大学院アジア・アフリカ地域研究研究科アフリカ地域研究専攻 / (主査)准教授 高田 明, 教授 太田 至, 准教授 平野(野元) 美佐, 准教授 小川 さやか / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM
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Spectacular Native Performances: From the Wild West to the Tourist Site, Nineteenth Century to the PresentScarangella, Linda 06 1900 (has links)
This dissertation engages with anthropological debates of the representation of Native peoples in performance through a series of comparative case studies that examine Native North American participation in Wild West
shows. Using multi-sited ethnographic and ethnohistorical approaches, it
investigates the experiences of some Native performers with the top Wild West
shows historically (1885-1930), of three Mohawk families who performed in a
variety of spectacles (early 1900s ), and of contemporary performers in Wild West show re-creations at EuroDisney (France) and Buffalo Bill Days (Sheridan, Wyoming, U.S.A). This research focuses on Native performers' perspectives and experiences in order to complicate the picture of exploitation and commercialization in this context. In this dissertation, rather than focusing solely on the production of stereotypes, I trace the extent and various forms of Native agency and expressions of identity through a series of encounters that occur in a Wild West show "contact zone." Drawing on the concept of transculturation, I argue that Native performers adopted and used contact zone encounters as a space to express their opinions or to maintain, express, and/or contest Native identity. I thus elucidate the various forms of agency that Native performers have wielded, whether expressive, communicative, performative, or agency of cultural projects. A "cultural
projects" approach to agency considers Native performers own goals and social relationships in addition to the socio-political constraints and power relations that structure their lives. Native performers had their own cultural projects; they actively pursued the opportunities and benefits of working in Wild West shows. I argue that narratives of opportunity, success, and pride found in the employment encounter, in oral histories of Mohawk performers' experiences, and in interviews with contemporary performers, represent agency of cultural projects. Oral histories from Mohawk performers' descendants and their interpretations of the archival record were crucial for revealing and substantiating these alternative perspectives of Native experiences in Wild West shows and spectacles. / Thesis / Doctor of Philosophy (PhD)
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Collecting en route : an exploration of the ethnographic collection of Gertrude Emily BenhamCummings, Catherine January 2013 (has links)
In the second half of the nineteenth century and the first decades of the twentieth century the collecting of objects from colonized countries and their subsequent display in western museums was widespread throughout Western Europe. How and why these collections were made, the processes of collection, and by whom, has only recently begun to be addressed. This thesis is an exploration of the ethnographic collection of Gertrude Emily Benham (1867-1938) who made eight voyages independently around the world from 1904 until 1938, during which time she amassed a collection of approximately eight hundred objects, which she donated to Plymouth City Museum and Art Gallery in 1935. It considers how and why she formed her collection and how, as a an amateur and marginalised collector, she can be located within discourses on ethnographic collecting. The thesis is organised by geographical regions in order to address the different contact zones of colonialism as well as to contextualise Benham within the cultural milieu in which she collected and the global collection of objects that she collected. An interdisciplinary perspective was employed to create a dialogue between anthropology, geography, museology, postcolonial and feminist theory to address the complex issues of colonial collecting. Benham is located within a range of intersecting histories: colonialism, travel, collecting, and gender. This study is the first in-depth examination of Benham as a collector and adds to the knowledge and understanding of Benham and her collection in Plymouth City Museum and Art Gallery. It contributes to the discourse on ethnographic collectors and collecting and in doing so it acknowledges the agency and contribution of marginal collectors to resituate them as a central and intrinsic component in the formation of the ethnographic museum. In addition, and central to this, is the agency and role of indigenous people in forming ethnographic collections. The thesis offers a foundation for further research into women ethnographic collectors and a more nuanced and inclusive account of ethnographic collecting.
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Navigating the Contradictions of Colonial Citizenship : A Study of Chinua Achebe’s No Longer at Ease Focused on Mr Green and Obi Okonkwo / Det koloniala tillståndets inkonsekvenser : En studie av Chinua Achebes No Longer at Ease med fokus på Mr Green och Obi OkonkowoCarlsson, Cecilia January 2019 (has links)
This thesis studies Chinua Achebe’s novel No Longer at Ease from a postcolonial perspective, specifically concentrating on its protagonist, the colonized Obi Okonkwo, and his antagonist, the colonizer Mr Green, using the theories of the literary critic Homi Bhabha. It argues that these two characters are hybrids in their ambivalent contact zone by demonstrating firstly, the coinciding presence of reciprocal feelings of sympathy/admiration and contempt, and secondly, that they are culturally cross-bred individuals. Additionally, this thesis examines the mimicry of Obi and reveals that it can be either strategic or subconscious in nature. It concludes that both mimicry and mockery have the potential to destabilize the structural power-imbalance between colonizer and colonized, thereby challenging colonial authority.
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Influência da taxa de aplicação superficial e da concentração de ar na eficiência de clarificação de água de abastecimento em unidades de flotação por ar dissolvido / Influence of surface application fee and concentration of air in efficiency of clarification of water supply in units dissolved air flotationEscher, Aline Eléia 22 September 2011 (has links)
Os objetivos deste trabalho foram verificar a influência das taxas de aplicação superficial das zonas de separação e de contato e da concentração de micro bolhas de ar na eficiência da remoção de partículas em unidades de flotação aplicadas ao tratamento de água para abastecimento público e, caracterizar a estrutura de escoamento no interior da zona de separação, com a utilização de uma planta piloto de flotação por ar dissolvido. Os trabalhos relativos à pesquisa foram divididos em duas etapas: a primeira delas contemplou a operação de unidade piloto alimentada com água sintética, utilizando três valores de taxa de aplicação superficial na zona de separação associadas a duas taxas de aplicação superficial na zona de contato, cada qual com três concentrações de ar fornecido à flotação. Foram mantidos fixos os parâmetros: tempo de contato na zona de contato, tempo de floculação, gradiente médio de floculação e velocidade cross-flow. Os resultados desta etapa foram monitorados com base na eficiência de remoção de cor e turbidez. As maiores eficiências de remoção, 87,5% para turbidez e 96,8% de cor aparente foram obtidos para as menores taxas de aplicação superficial nas zonas de contato e separação estudadas, associadas à concentração de ar de 4,90 g/\'CM POT.3\' de água. Este, entre outros resultados, levou à conclusão de que tal concentração de ar fornecida à flotação forneceu sempre os menores residuais de cor e turbidez nas condições investigadas. Quanto à taxa de aplicação superficial na zona de contato, 136,3 m/h resultou em maiores eficiências de clarificação, sendo que o aumento para 172,8 m/h causou ligeira queda na eficiência. Finalmente, quanto à taxa de aplicação superficial na zona de separação, a menor taxa (9,8 m/h) foi aquela onde as maiores eficiências de clarificação foram obtidas, as quais decresceram à medida que a taxa foi aumentada. Na segunda etapa utilizou-se a sonda microADV na caracterização do escoamento no interior da zona de separação. Foram realizadas caracterizações para as três concentrações de ar fornecidas para a flotação estudadas na etapa I, mantendo-se fixos a taxa de aplicação superficial e o tempo na zona de contato (136,3 m/h e 53 s, respectivamente), a taxa de aplicação superficial na zona de separação (12,3 m/h), a vazão de entrada e a velocidade cross-flow, conforme a etapa I. Para as três condições estudadas, adotou-se uma malha virtual de coleta de dados de duas dimensões, composta por 98 pontos igualmente espaçados, sendo 14 na altura e 7 paralelos ao comprimento. O tempo de coleta de dados em cada ponto foi de 2 min com uma freqüência de amostragem de 50 Hz. Os vetores de velocidade resultantes foram plotados em esquemas ilustrativos, afim de se comparar os três perfis obtidos. Observou-se em todos os casos um fluxo em curto-circuito na região superior da zona de separação e logo abaixo desta, um fluxo descendente no sentido dos coletores ao fundo da unidade. Quando comparadas, apenas pequenas diferenças quanto à espessura da região de curto circuito superior foram verificadas entre as três situações abordadas, as quais não explicam as diferentes eficiências de clarificação obtidas na etapa I da pesquisa, relacionadas à concentração de ar fornecida à flotação. / The objectives of this study were to determine the influence of hydraulic surface loading of contact and separation zones and of the air micro bubbles concentration in the particle removal efficiency in flotation units applied to water treatment for public supply and also characterize the flow structure into the separation zone. The works were divided into two stages: the first included the operation of the pilot plant fed with synthetic water, using three values of hydraulic surface loadings in the separation zone associated with two hydraulic surface loadings in the superficial zone of contact, each one with three concentrations of air supplied to the flotation. Were kept fixed parameters: contact time in the contact zone, flocculation time, mean flocculation gradient and cross-flow velocity. The results of this step were monitored based on the removal efficiency of color and turbidity. The higher removal efficiencies, 87.5% of turbidity and 96.8% apparent color were obtained for the lower hydraulic surface loading of contact and separation zones studied, associated with air concentration of 4.90 g/\'CM POT.3\' of water. This, among other results, led to the conclusion that this air supplied to the flotation concentration always provided the lowest residual color and turbidity values, under the conditions investigated. As for the hydraulic surface loading in the contact zone, 136.3 m/h resulted in higher efficiencies for clarification and when increasing to 172.8 m/h slight drop in efficiency was caused. Finally, regarding separation zone hydraulic surface loading, the lowest rate (9.8 m/h) was the one in which the highest efficiencies of clarification were obtained, which decreased, as the hydraulic surface loading was increased. In the second step, the probe microADV was used to characterize the flow inside the separation zone. Characterizations were carried out for the three air concentrations supplied to the flotation studied on the first step, fixing contact zone hydraulic surface loading and time (136.3 m/h and 53 s, respectively), the separation zone hydraulic surface loading (12.3 m/h), the input flow and cross-flow velocity as step I. For the three conditions studied, we adopted a of two-dimensional virtual data collection grid with 98 equally spaced points, 14 in height and 7 parallel to the length. The data collection time at each point was 2 min with a sampling frequency of 50 Hz. The resulting velocity vectors were plotted on illustrative diagrams in order to compare the three profiles obtained. A short-circuit flow in the upper part of the separation zone and below this, a downward flow toward the bottom of the collector unit were observed in all cases. In comparison, only small differences in the thickness of the upper region of short circuit were observed between the three situations discussed, which do not explain the different efficiencies of clarification obtained in the first step of the research related to the air bubble concentration.
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