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Eugenio Foresti - One of the best experts on this subject based on the ideXlab platform.
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Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater.
Bioresource Technology, 2010Co-Authors: Selma Aparecida Cubas, José A.d. Rodrigues, Suzana Maria Ratusznei, Eugenio Foresti, Marcelo ZaiatAbstract:Abstract The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR – Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, Flat-Blade, inclined-Blade and curved-Blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530 ± 37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the Flat-Blade turbine impeller.
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Effect of impeller type and agitation on the performance of pilot scale ASBR and AnSBBR applied to sanitary wastewater treatment
Journal of Environmental Management, 2010Co-Authors: Luciano Farias De Novaes, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Bruna Luckmann Saratt, Rogers Ribeiro, Eugenio ForestiAbstract:Abstract The objective of this work was to assess the effect of agitation rate and impeller type in two mechanically stirred sequencing batch reactors: one containing granulated biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam (denominated AnSBBR). Each configuration, with total volume of 1 m 3 , treated 0.65 m 3 sanitary wastewater at ambient temperature in 8-h cycles. Three impeller types were assessed for each reactor configuration: Flat-Blade turbine impeller, 45°-inclined-Blade turbine impeller and helix impeller, as well as two agitation rates: 40 and 80 rpm, resulting in a combination of six experimental conditions. In addition, the ASBR was also operated at 20 rpm with a Flat-Blade turbine impeller and the AnSBBR was operated with a draft tube and helix impeller at 80 and 120 rpm. To quantify how impeller type and agitation rate relate to substrate consumption rate, results obtained during monitoring at the end of the cycle, as well as the time profiles during a cycle were analyzed. Increasing agitation rate from 40 rpm to 80 rpm in the AnSBBR improved substrate consumption rate whereas in the ASBR this increase destabilized the system, likely due to granule rupture caused by the higher agitation. The AnSBBR showed highest solids and substrate removal, highest kinetic constant and highest alkalinity production when using a helix impeller, 80 rpm, and no draft tube. The best condition for the ASBR was achieved with a Flat-Blade turbine impeller at 20 rpm. The presence of the draft tube in the AnSBBR did not show significant improvement in reactor efficiency. Furthermore, power consumption studies in these pilot scale reactors showed that power transfer required to improve mass transfer might be technically and economically feasible.
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Effect of impeller type and mechanical agitation on the mass transfer and power consumption aspects of ASBR operation treating synthetic wastewater
Journal of Environmental Management, 2009Co-Authors: Rogério Michelan, Thiago R. Zimmer, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Eugenio ForestiAbstract:The effect of flow type and rotor speed was investigated in a round-bottom reactor with 5 L useful volume containing 2.0 L of granular biomass. The reactor treated 2.0 L of synthetic wastewater with a concentration of 800 mgCOD/L in 8-h cycles at 30 °C. Five impellers, commonly used in biological processes, have been employed to this end, namely: a turbine and a paddle impeller with six-vertical-Flat-Blades, a turbine and a paddle impeller with six-45°-inclined-Flat-Blades and a three-Blade-helix impeller. Results showed that altering impeller type and rotor speed did not significantly affect system stability and performance. Average organic matter removal efficiency was about 84% for filtered samples, total volatile acids concentration was below 20 mgHAc/L and bicarbonate alkalinity a little less than 400 mgCaCO3/L for most of the investigated conditions. However, analysis of the first-order kinetic model constants showed that alteration in rotor speed resulted in an increase in the values of the kinetic constants (for instance, from 0.57 h-1 at 50 rpm to 0.84 h-1 at 75 rpm when the paddle impeller with six-45°-inclined-Flat-Blades was used) and that axial flow in mechanically stirred reactors is preferable over radial-flow when the vertical-Flat-Blade impeller is compared to the inclined-Flat-Blade impeller (for instance at 75 rpm, from 0.52 h-1 with the six-Flat-Blade-paddle impeller to 0.84 h-1 with the six-45°-inclined-Flat-Blade-paddle impeller), demonstrating that there is a rotor speed and an impeller type that maximize solid-liquid mass transfer in the reaction medium. Furthermore, power consumption studies in this reduced reactor volume showed that no high power transfer is required to improve mass transfer (less than 0.6 kW/103 m3). © 2008 Elsevier Ltd. All rights reserved.
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Effect of impeller type and mechanical agitation on the mass transfer and power consumption aspects of ASBR operation treating synthetic wastewater.
Journal of Environmental Management, 2008Co-Authors: Rogério Michelan, Thiago R. Zimmer, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Eugenio ForestiAbstract:Abstract The effect of flow type and rotor speed was investigated in a round-bottom reactor with 5 L useful volume containing 2.0 L of granular biomass. The reactor treated 2.0 L of synthetic wastewater with a concentration of 800 mgCOD/L in 8-h cycles at 30 °C. Five impellers, commonly used in biological processes, have been employed to this end, namely: a turbine and a paddle impeller with six-vertical-Flat-Blades, a turbine and a paddle impeller with six-45°-inclined-Flat-Blades and a three-Blade-helix impeller. Results showed that altering impeller type and rotor speed did not significantly affect system stability and performance. Average organic matter removal efficiency was about 84% for filtered samples, total volatile acids concentration was below 20 mgHAc/L and bicarbonate alkalinity a little less than 400 mgCaCO 3 /L for most of the investigated conditions. However, analysis of the first-order kinetic model constants showed that alteration in rotor speed resulted in an increase in the values of the kinetic constants (for instance, from 0.57 h −1 at 50 rpm to 0.84 h −1 at 75 rpm when the paddle impeller with six-45°-inclined-Flat-Blades was used) and that axial flow in mechanically stirred reactors is preferable over radial-flow when the vertical-Flat-Blade impeller is compared to the inclined-Flat-Blade impeller (for instance at 75 rpm, from 0.52 h −1 with the six-Flat-Blade-paddle impeller to 0.84 h −1 with the six-45°-inclined-Flat-Blade-paddle impeller), demonstrating that there is a rotor speed and an impeller type that maximize solid–liquid mass transfer in the reaction medium. Furthermore, power consumption studies in this reduced reactor volume showed that no high power transfer is required to improve mass transfer (less than 0.6 kW/10 3 m 3 ).
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Feasibility of treating swine manure in an anaerobic sequencing batch biofilm reactor with mechanical stirring
Applied Biochemistry and Biotechnology, 2005Co-Authors: Samantha Cristina Pinho, Suzana Maria Ratusznei, Eugenio Foresti, Bruna Soares Fernandes, José Alberto D. Rodrigues, Marcelo ZaiatAbstract:Anaerobic sequencing batch reactors containing granular or flocculent biomass have been employed successfully in the treatment of piggery wastewater. However, the studies in which these reactors were employed did not focus specifically on accelerating the hydrolysis step, even though the degradation of this chemical oxygen demand (COD) fraction is likely to be the limiting step in many investigations of this type of wastewater. The mechanically stirred anaerobic sequencing batch biofilm reactor offers an alternative for hastening the hydrolysis step, because mechanical agitation can help to speed up the reduction of particle sizes in the fraction of particulate organic matter. In the present study, a 4.5-L reactor was operated at 30°C, with biomass immobilized on cubic polyurethane foam matrices (1 cm of side) and mechanical stirring provided by three Flat-Blade turbines (6 cm) at agitation rates varying from 0 to 500 rpm. The reactor was operated to treat diluted swine waste, and mechanical stirring efficiently improved degradation of the suspended COD. The operational data indicate that the reactor remained stable during the testing period. After 2 h of operation at 500 rpm, the suspended COD decreased by about 65% (from 1500 to 380 mg/L). Apparent kinetic constants were also calculated by modified first-order expressions.
Marcelo Zaiat - One of the best experts on this subject based on the ideXlab platform.
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Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater.
Bioresource Technology, 2010Co-Authors: Selma Aparecida Cubas, José A.d. Rodrigues, Suzana Maria Ratusznei, Eugenio Foresti, Marcelo ZaiatAbstract:Abstract The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR – Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, Flat-Blade, inclined-Blade and curved-Blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530 ± 37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the Flat-Blade turbine impeller.
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Effect of impeller type and agitation on the performance of pilot scale ASBR and AnSBBR applied to sanitary wastewater treatment
Journal of Environmental Management, 2010Co-Authors: Luciano Farias De Novaes, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Bruna Luckmann Saratt, Rogers Ribeiro, Eugenio ForestiAbstract:Abstract The objective of this work was to assess the effect of agitation rate and impeller type in two mechanically stirred sequencing batch reactors: one containing granulated biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam (denominated AnSBBR). Each configuration, with total volume of 1 m 3 , treated 0.65 m 3 sanitary wastewater at ambient temperature in 8-h cycles. Three impeller types were assessed for each reactor configuration: Flat-Blade turbine impeller, 45°-inclined-Blade turbine impeller and helix impeller, as well as two agitation rates: 40 and 80 rpm, resulting in a combination of six experimental conditions. In addition, the ASBR was also operated at 20 rpm with a Flat-Blade turbine impeller and the AnSBBR was operated with a draft tube and helix impeller at 80 and 120 rpm. To quantify how impeller type and agitation rate relate to substrate consumption rate, results obtained during monitoring at the end of the cycle, as well as the time profiles during a cycle were analyzed. Increasing agitation rate from 40 rpm to 80 rpm in the AnSBBR improved substrate consumption rate whereas in the ASBR this increase destabilized the system, likely due to granule rupture caused by the higher agitation. The AnSBBR showed highest solids and substrate removal, highest kinetic constant and highest alkalinity production when using a helix impeller, 80 rpm, and no draft tube. The best condition for the ASBR was achieved with a Flat-Blade turbine impeller at 20 rpm. The presence of the draft tube in the AnSBBR did not show significant improvement in reactor efficiency. Furthermore, power consumption studies in these pilot scale reactors showed that power transfer required to improve mass transfer might be technically and economically feasible.
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Effect of impeller type and mechanical agitation on the mass transfer and power consumption aspects of ASBR operation treating synthetic wastewater
Journal of Environmental Management, 2009Co-Authors: Rogério Michelan, Thiago R. Zimmer, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Eugenio ForestiAbstract:The effect of flow type and rotor speed was investigated in a round-bottom reactor with 5 L useful volume containing 2.0 L of granular biomass. The reactor treated 2.0 L of synthetic wastewater with a concentration of 800 mgCOD/L in 8-h cycles at 30 °C. Five impellers, commonly used in biological processes, have been employed to this end, namely: a turbine and a paddle impeller with six-vertical-Flat-Blades, a turbine and a paddle impeller with six-45°-inclined-Flat-Blades and a three-Blade-helix impeller. Results showed that altering impeller type and rotor speed did not significantly affect system stability and performance. Average organic matter removal efficiency was about 84% for filtered samples, total volatile acids concentration was below 20 mgHAc/L and bicarbonate alkalinity a little less than 400 mgCaCO3/L for most of the investigated conditions. However, analysis of the first-order kinetic model constants showed that alteration in rotor speed resulted in an increase in the values of the kinetic constants (for instance, from 0.57 h-1 at 50 rpm to 0.84 h-1 at 75 rpm when the paddle impeller with six-45°-inclined-Flat-Blades was used) and that axial flow in mechanically stirred reactors is preferable over radial-flow when the vertical-Flat-Blade impeller is compared to the inclined-Flat-Blade impeller (for instance at 75 rpm, from 0.52 h-1 with the six-Flat-Blade-paddle impeller to 0.84 h-1 with the six-45°-inclined-Flat-Blade-paddle impeller), demonstrating that there is a rotor speed and an impeller type that maximize solid-liquid mass transfer in the reaction medium. Furthermore, power consumption studies in this reduced reactor volume showed that no high power transfer is required to improve mass transfer (less than 0.6 kW/103 m3). © 2008 Elsevier Ltd. All rights reserved.
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Effect of impeller type and mechanical agitation on the mass transfer and power consumption aspects of ASBR operation treating synthetic wastewater.
Journal of Environmental Management, 2008Co-Authors: Rogério Michelan, Thiago R. Zimmer, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Eugenio ForestiAbstract:Abstract The effect of flow type and rotor speed was investigated in a round-bottom reactor with 5 L useful volume containing 2.0 L of granular biomass. The reactor treated 2.0 L of synthetic wastewater with a concentration of 800 mgCOD/L in 8-h cycles at 30 °C. Five impellers, commonly used in biological processes, have been employed to this end, namely: a turbine and a paddle impeller with six-vertical-Flat-Blades, a turbine and a paddle impeller with six-45°-inclined-Flat-Blades and a three-Blade-helix impeller. Results showed that altering impeller type and rotor speed did not significantly affect system stability and performance. Average organic matter removal efficiency was about 84% for filtered samples, total volatile acids concentration was below 20 mgHAc/L and bicarbonate alkalinity a little less than 400 mgCaCO 3 /L for most of the investigated conditions. However, analysis of the first-order kinetic model constants showed that alteration in rotor speed resulted in an increase in the values of the kinetic constants (for instance, from 0.57 h −1 at 50 rpm to 0.84 h −1 at 75 rpm when the paddle impeller with six-45°-inclined-Flat-Blades was used) and that axial flow in mechanically stirred reactors is preferable over radial-flow when the vertical-Flat-Blade impeller is compared to the inclined-Flat-Blade impeller (for instance at 75 rpm, from 0.52 h −1 with the six-Flat-Blade-paddle impeller to 0.84 h −1 with the six-45°-inclined-Flat-Blade-paddle impeller), demonstrating that there is a rotor speed and an impeller type that maximize solid–liquid mass transfer in the reaction medium. Furthermore, power consumption studies in this reduced reactor volume showed that no high power transfer is required to improve mass transfer (less than 0.6 kW/10 3 m 3 ).
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Feasibility of treating swine manure in an anaerobic sequencing batch biofilm reactor with mechanical stirring
Applied Biochemistry and Biotechnology, 2005Co-Authors: Samantha Cristina Pinho, Suzana Maria Ratusznei, Eugenio Foresti, Bruna Soares Fernandes, José Alberto D. Rodrigues, Marcelo ZaiatAbstract:Anaerobic sequencing batch reactors containing granular or flocculent biomass have been employed successfully in the treatment of piggery wastewater. However, the studies in which these reactors were employed did not focus specifically on accelerating the hydrolysis step, even though the degradation of this chemical oxygen demand (COD) fraction is likely to be the limiting step in many investigations of this type of wastewater. The mechanically stirred anaerobic sequencing batch biofilm reactor offers an alternative for hastening the hydrolysis step, because mechanical agitation can help to speed up the reduction of particle sizes in the fraction of particulate organic matter. In the present study, a 4.5-L reactor was operated at 30°C, with biomass immobilized on cubic polyurethane foam matrices (1 cm of side) and mechanical stirring provided by three Flat-Blade turbines (6 cm) at agitation rates varying from 0 to 500 rpm. The reactor was operated to treat diluted swine waste, and mechanical stirring efficiently improved degradation of the suspended COD. The operational data indicate that the reactor remained stable during the testing period. After 2 h of operation at 500 rpm, the suspended COD decreased by about 65% (from 1500 to 380 mg/L). Apparent kinetic constants were also calculated by modified first-order expressions.
Suzana Maria Ratusznei - One of the best experts on this subject based on the ideXlab platform.
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Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater.
Bioresource Technology, 2010Co-Authors: Selma Aparecida Cubas, José A.d. Rodrigues, Suzana Maria Ratusznei, Eugenio Foresti, Marcelo ZaiatAbstract:Abstract The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR – Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, Flat-Blade, inclined-Blade and curved-Blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530 ± 37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the Flat-Blade turbine impeller.
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Effect of impeller type and agitation on the performance of pilot scale ASBR and AnSBBR applied to sanitary wastewater treatment
Journal of Environmental Management, 2010Co-Authors: Luciano Farias De Novaes, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Bruna Luckmann Saratt, Rogers Ribeiro, Eugenio ForestiAbstract:Abstract The objective of this work was to assess the effect of agitation rate and impeller type in two mechanically stirred sequencing batch reactors: one containing granulated biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam (denominated AnSBBR). Each configuration, with total volume of 1 m 3 , treated 0.65 m 3 sanitary wastewater at ambient temperature in 8-h cycles. Three impeller types were assessed for each reactor configuration: Flat-Blade turbine impeller, 45°-inclined-Blade turbine impeller and helix impeller, as well as two agitation rates: 40 and 80 rpm, resulting in a combination of six experimental conditions. In addition, the ASBR was also operated at 20 rpm with a Flat-Blade turbine impeller and the AnSBBR was operated with a draft tube and helix impeller at 80 and 120 rpm. To quantify how impeller type and agitation rate relate to substrate consumption rate, results obtained during monitoring at the end of the cycle, as well as the time profiles during a cycle were analyzed. Increasing agitation rate from 40 rpm to 80 rpm in the AnSBBR improved substrate consumption rate whereas in the ASBR this increase destabilized the system, likely due to granule rupture caused by the higher agitation. The AnSBBR showed highest solids and substrate removal, highest kinetic constant and highest alkalinity production when using a helix impeller, 80 rpm, and no draft tube. The best condition for the ASBR was achieved with a Flat-Blade turbine impeller at 20 rpm. The presence of the draft tube in the AnSBBR did not show significant improvement in reactor efficiency. Furthermore, power consumption studies in these pilot scale reactors showed that power transfer required to improve mass transfer might be technically and economically feasible.
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Effect of impeller type and mechanical agitation on the mass transfer and power consumption aspects of ASBR operation treating synthetic wastewater
Journal of Environmental Management, 2009Co-Authors: Rogério Michelan, Thiago R. Zimmer, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Eugenio ForestiAbstract:The effect of flow type and rotor speed was investigated in a round-bottom reactor with 5 L useful volume containing 2.0 L of granular biomass. The reactor treated 2.0 L of synthetic wastewater with a concentration of 800 mgCOD/L in 8-h cycles at 30 °C. Five impellers, commonly used in biological processes, have been employed to this end, namely: a turbine and a paddle impeller with six-vertical-Flat-Blades, a turbine and a paddle impeller with six-45°-inclined-Flat-Blades and a three-Blade-helix impeller. Results showed that altering impeller type and rotor speed did not significantly affect system stability and performance. Average organic matter removal efficiency was about 84% for filtered samples, total volatile acids concentration was below 20 mgHAc/L and bicarbonate alkalinity a little less than 400 mgCaCO3/L for most of the investigated conditions. However, analysis of the first-order kinetic model constants showed that alteration in rotor speed resulted in an increase in the values of the kinetic constants (for instance, from 0.57 h-1 at 50 rpm to 0.84 h-1 at 75 rpm when the paddle impeller with six-45°-inclined-Flat-Blades was used) and that axial flow in mechanically stirred reactors is preferable over radial-flow when the vertical-Flat-Blade impeller is compared to the inclined-Flat-Blade impeller (for instance at 75 rpm, from 0.52 h-1 with the six-Flat-Blade-paddle impeller to 0.84 h-1 with the six-45°-inclined-Flat-Blade-paddle impeller), demonstrating that there is a rotor speed and an impeller type that maximize solid-liquid mass transfer in the reaction medium. Furthermore, power consumption studies in this reduced reactor volume showed that no high power transfer is required to improve mass transfer (less than 0.6 kW/103 m3). © 2008 Elsevier Ltd. All rights reserved.
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Effect of impeller type and mechanical agitation on the mass transfer and power consumption aspects of ASBR operation treating synthetic wastewater.
Journal of Environmental Management, 2008Co-Authors: Rogério Michelan, Thiago R. Zimmer, José A.d. Rodrigues, Suzana Maria Ratusznei, Marcelo Zaiat, Deovaldo De Moraes, Eugenio ForestiAbstract:Abstract The effect of flow type and rotor speed was investigated in a round-bottom reactor with 5 L useful volume containing 2.0 L of granular biomass. The reactor treated 2.0 L of synthetic wastewater with a concentration of 800 mgCOD/L in 8-h cycles at 30 °C. Five impellers, commonly used in biological processes, have been employed to this end, namely: a turbine and a paddle impeller with six-vertical-Flat-Blades, a turbine and a paddle impeller with six-45°-inclined-Flat-Blades and a three-Blade-helix impeller. Results showed that altering impeller type and rotor speed did not significantly affect system stability and performance. Average organic matter removal efficiency was about 84% for filtered samples, total volatile acids concentration was below 20 mgHAc/L and bicarbonate alkalinity a little less than 400 mgCaCO 3 /L for most of the investigated conditions. However, analysis of the first-order kinetic model constants showed that alteration in rotor speed resulted in an increase in the values of the kinetic constants (for instance, from 0.57 h −1 at 50 rpm to 0.84 h −1 at 75 rpm when the paddle impeller with six-45°-inclined-Flat-Blades was used) and that axial flow in mechanically stirred reactors is preferable over radial-flow when the vertical-Flat-Blade impeller is compared to the inclined-Flat-Blade impeller (for instance at 75 rpm, from 0.52 h −1 with the six-Flat-Blade-paddle impeller to 0.84 h −1 with the six-45°-inclined-Flat-Blade-paddle impeller), demonstrating that there is a rotor speed and an impeller type that maximize solid–liquid mass transfer in the reaction medium. Furthermore, power consumption studies in this reduced reactor volume showed that no high power transfer is required to improve mass transfer (less than 0.6 kW/10 3 m 3 ).
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Feasibility of treating swine manure in an anaerobic sequencing batch biofilm reactor with mechanical stirring
Applied Biochemistry and Biotechnology, 2005Co-Authors: Samantha Cristina Pinho, Suzana Maria Ratusznei, Eugenio Foresti, Bruna Soares Fernandes, José Alberto D. Rodrigues, Marcelo ZaiatAbstract:Anaerobic sequencing batch reactors containing granular or flocculent biomass have been employed successfully in the treatment of piggery wastewater. However, the studies in which these reactors were employed did not focus specifically on accelerating the hydrolysis step, even though the degradation of this chemical oxygen demand (COD) fraction is likely to be the limiting step in many investigations of this type of wastewater. The mechanically stirred anaerobic sequencing batch biofilm reactor offers an alternative for hastening the hydrolysis step, because mechanical agitation can help to speed up the reduction of particle sizes in the fraction of particulate organic matter. In the present study, a 4.5-L reactor was operated at 30°C, with biomass immobilized on cubic polyurethane foam matrices (1 cm of side) and mechanical stirring provided by three Flat-Blade turbines (6 cm) at agitation rates varying from 0 to 500 rpm. The reactor was operated to treat diluted swine waste, and mechanical stirring efficiently improved degradation of the suspended COD. The operational data indicate that the reactor remained stable during the testing period. After 2 h of operation at 500 rpm, the suspended COD decreased by about 65% (from 1500 to 380 mg/L). Apparent kinetic constants were also calculated by modified first-order expressions.
S D Vlaev - One of the best experts on this subject based on the ideXlab platform.
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Shear stress generated by radial flow impellers at bioreactor integrated membranes
Theoretical Foundations of Chemical Engineering, 2016Co-Authors: S D Vlaev, I. TsibranskaAbstract:The study reveals the hydrodynamics at the surface of a submerged tubular membrane module integrated in a stirred membrane bioreactor. The reactor is equipped with a conventional six Flat-Blade impeller imposing radial circulation across the membrane interface. Simulation and computer visualization of “real” flow using a Reynolds-averaged Navier-Stokes model and CFD methodology are employed. A variety of model solutions at various mixing intensity are obtained and the mixing conditions are assessed by delineation of the near-wall zones and identification of the zones' shear rate and shear stress values. Shear rate non-uniformity along the surface of the tubular module is visualized. Shear stress values as high as 160 Pa at the membrane module lower section and as low as 0.6 Pa at the module upper section has been determined. Referring to reported data for shear stress near Flat plate stirred filtration cells and external narrow-channel cross-flow systems, the mixing conditions are expected to allow enhanced access of the retentate fluid to the membrane surface, as well as possible low membrane fouling potential related to microfiltration practice.
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shear and skin friction on particles in power law fluids agitated by Flat Blade and fluid foil impellers
Chemical Engineering Science, 2006Co-Authors: S D Vlaev, I Nikov, Martin MartinovAbstract:Abstract The shear rates that exert angular deformation on spherical particles have been measured. The particles are mimiced by a spherical probe. The probe has been immersed in various impeller-agitated power law fluids. The fluids are aqueous dispersions of polymers, e.g. CMC, xanthan gum and starch. The probe has been positioned in various points of a stirred vessel and at various angles. Angle-averaged shear rate distributions were produced. The distributions obtained are characteristic for the specific impeller flow patterns. The flow patterns have been identified by computational fluid dynamics (CFD). Two types of impellers representative for the Flat and the fluid-foil Blade design, i.e., a Rushton Flat-Blade turbine (RT) and a Narcissus impeller (NS) are studied. The effects of rheological properties and Blade design on the ‘shear-rate-on-particles’ distribution are examined. The local shear field non-uniformity has been uncovered and compared in terms of the CFD-generated time-averaged velocity and deformation rate profiles. The ‘shear-rate-on-particles’ distribution apart from the impeller is found to follow qualitatively the time-averaged inner flow shear rate distribution. Referring to impeller speed 5–12.5 Hz, the dimensionless wall shear rate varied between 200 and 1000. In power law fluids, the shear rate on particles decreased up to 50%. The fluid-foil NS-generated shear field was found comparable to the shear field induced by conventional Flat-Blade turbines and appeared in cases less sensitive to polymer presence. The shear rate produced by the fluid-foil impeller in the highly shear-thinning model solution ( n ∼ 0.4 ) exceeded the Flat-Blade RT-imposed shear rate. The analysis has been extended to skin friction drag on particles. It is shown that, while exerting an undoubtedly greater angular deformation in water-like fluids, in polymer presence the conventional Flat-Blade turbine introduces a flow geometry that imposes particle drag that is close or in some cases even less than the one generated by the fluid-foil impeller. The fact implies a weak shape effect of radial turbines on shear-sensitive particles or particle dispersions in power law liquids.
Martin Martinov - One of the best experts on this subject based on the ideXlab platform.
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shear and skin friction on particles in power law fluids agitated by Flat Blade and fluid foil impellers
Chemical Engineering Science, 2006Co-Authors: S D Vlaev, I Nikov, Martin MartinovAbstract:Abstract The shear rates that exert angular deformation on spherical particles have been measured. The particles are mimiced by a spherical probe. The probe has been immersed in various impeller-agitated power law fluids. The fluids are aqueous dispersions of polymers, e.g. CMC, xanthan gum and starch. The probe has been positioned in various points of a stirred vessel and at various angles. Angle-averaged shear rate distributions were produced. The distributions obtained are characteristic for the specific impeller flow patterns. The flow patterns have been identified by computational fluid dynamics (CFD). Two types of impellers representative for the Flat and the fluid-foil Blade design, i.e., a Rushton Flat-Blade turbine (RT) and a Narcissus impeller (NS) are studied. The effects of rheological properties and Blade design on the ‘shear-rate-on-particles’ distribution are examined. The local shear field non-uniformity has been uncovered and compared in terms of the CFD-generated time-averaged velocity and deformation rate profiles. The ‘shear-rate-on-particles’ distribution apart from the impeller is found to follow qualitatively the time-averaged inner flow shear rate distribution. Referring to impeller speed 5–12.5 Hz, the dimensionless wall shear rate varied between 200 and 1000. In power law fluids, the shear rate on particles decreased up to 50%. The fluid-foil NS-generated shear field was found comparable to the shear field induced by conventional Flat-Blade turbines and appeared in cases less sensitive to polymer presence. The shear rate produced by the fluid-foil impeller in the highly shear-thinning model solution ( n ∼ 0.4 ) exceeded the Flat-Blade RT-imposed shear rate. The analysis has been extended to skin friction drag on particles. It is shown that, while exerting an undoubtedly greater angular deformation in water-like fluids, in polymer presence the conventional Flat-Blade turbine introduces a flow geometry that imposes particle drag that is close or in some cases even less than the one generated by the fluid-foil impeller. The fact implies a weak shape effect of radial turbines on shear-sensitive particles or particle dispersions in power law liquids.