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A Heduit - One of the best experts on this subject based on the ideXlab platform.

  • predicting oxygen transfer of Fine Bubble diffused aeration systems model issued from dimensional analysis
    Water Research, 2005
    Co-Authors: Sylvie Gillot, M Roustan, S Capelamarsal, A Heduit
    Abstract:

    Abstract The standard oxygenation performances of Fine Bubble diffused aeration systems in clean water, measured in 12 cylindrical tanks (water depth from 2.4 to 6.1 m), were analysed using dimensional analysis. A relationship was established to estimate the scale-up factor for oxygen transfer, the transfer number ( N T ) N T = k L a 20 U G ( ν 2 g ) 1 / 3 = 7.77 × 1 0 - 5 ( S p S ) 0.24 ( S p S a ) - 0.15 ( D h ) 0.13 . The transfer number, which is written as a function of the oxygen transfer coefficient ( k L a 20 ) , the gas superficial velocity ( U G ) , the kinematic viscosity of water ( ν ) and the acceleration due to gravity ( g ) , has the same physical meaning as the specific oxygen transfer efficiency. N T only depends on the geometry of the tank/aeration system [the total surface of the perforated membrane ( S p ) , the surface of the tank ( S ) or its diameter ( D ) , the total surface of the zones covered by the diffusers (“aerated area”, S a ) and the submergence of the diffusers ( h ) ]. This analysis allowed to better describe the mass transfer in cylindrical tanks. Within the range of the parameters considered, the oxygen transfer coefficient ( k L a 20 ) is an increasing linear function of the air flow rate. For a given air flow rate and a given tank surface area, k L a 20 decreases with the water depth (submergence of the diffusers). For a given water depth, k L a 20 increases with the number of diffusers, and, for an equal number of diffusers, with the total area of the zones covered by the diffusers. The latter result evidences the superiority of the total floor coverage over an arrangement whereby the diffusers are placed on separate grids. The specific standard oxygen transfer efficiency is independent of the air flow rate and the water depth, the drop in the k L a 20 being offset by the increase of the saturation concentration. For a given tank area, the impact of the total surface of the perforated membrane ( S p ) and of the aerated area ( S a ) is the same as on the oxygen transfer coefficient.

  • Predicting oxygen transfer of Fine Bubble diffused aeration systems—model issued from dimensional analysis
    Water Research, 2005
    Co-Authors: Sylvie Gillot, M Roustan, S. Capela-marsal, A Heduit
    Abstract:

    Abstract The standard oxygenation performances of Fine Bubble diffused aeration systems in clean water, measured in 12 cylindrical tanks (water depth from 2.4 to 6.1 m), were analysed using dimensional analysis. A relationship was established to estimate the scale-up factor for oxygen transfer, the transfer number ( N T ) N T = k L a 20 U G ( ν 2 g ) 1 / 3 = 7.77 × 1 0 - 5 ( S p S ) 0.24 ( S p S a ) - 0.15 ( D h ) 0.13 . The transfer number, which is written as a function of the oxygen transfer coefficient ( k L a 20 ) , the gas superficial velocity ( U G ) , the kinematic viscosity of water ( ν ) and the acceleration due to gravity ( g ) , has the same physical meaning as the specific oxygen transfer efficiency. N T only depends on the geometry of the tank/aeration system [the total surface of the perforated membrane ( S p ) , the surface of the tank ( S ) or its diameter ( D ) , the total surface of the zones covered by the diffusers (“aerated area”, S a ) and the submergence of the diffusers ( h ) ]. This analysis allowed to better describe the mass transfer in cylindrical tanks. Within the range of the parameters considered, the oxygen transfer coefficient ( k L a 20 ) is an increasing linear function of the air flow rate. For a given air flow rate and a given tank surface area, k L a 20 decreases with the water depth (submergence of the diffusers). For a given water depth, k L a 20 increases with the number of diffusers, and, for an equal number of diffusers, with the total area of the zones covered by the diffusers. The latter result evidences the superiority of the total floor coverage over an arrangement whereby the diffusers are placed on separate grids. The specific standard oxygen transfer efficiency is independent of the air flow rate and the water depth, the drop in the k L a 20 being offset by the increase of the saturation concentration. For a given tank area, the impact of the total surface of the perforated membrane ( S p ) and of the aerated area ( S a ) is the same as on the oxygen transfer coefficient.

  • transfer number in Fine Bubble diffused aeration systems
    Water Science and Technology, 2001
    Co-Authors: S Capela, M Roustan, A Heduit
    Abstract:

    On the basis of full-scale data from 58 clean water tests performed in 26 activated sludge tanks equipped with Fine Bubble diffusers and of a theoretical approach, it can be stated that Fine Bubble aeration systems with total floor coverage arrangement provide higher kLa values and the lowest spiral liquid circulation. An efficiency criterion for oxygen transfer ( N T ) was deFined on the basis of the dimensional analysis. The transfer number N T allows us to take account of the impact of vertical liquid circulation movements on oxygen transfer. The values of N T calculated from the results of full scale nonsteady-state clean water tests vary from 5.3×10 -5 to 9.1×10 -5 and are directly dependent upon the arrangement of air diffusers. It has been shown that the highest transfer numbers corresponded to the total floor coverage arrangement and the average calculated N T values is 7.7×10 -5 , independently of the diffuser density and of the gas velocity, over the ranges studied. The lowest transfer numbers are obtained when the diffusers are located in separate grids, and the transfer number is reduced with increasing air flow rate.

  • effect of air flow rate on oxygen transfer in an oxidation ditch equipped with Fine Bubble diffusers and slow speed mixers
    Water Research, 2000
    Co-Authors: S Gillot, A Heduit
    Abstract:

    Abstract The effect of air flow rate on oxygen transfer efficiency was examined in clean water and under process conditions in an oxidation ditch equipped with Fine Bubble membrane diffusers and large blade slow speed mixers. Under process conditions, an increase in the air flow rate resulted in a decrease of the oxygen transfer efficiency similar to that observed in clean water. Consequently, the value of the alpha factor was in the order of 0.58 independently of the air flow rate (between 45 and 110 m 3  h −1 per m 2 of membrane). The combined influence of the air flow rate and of the horizontal liquid velocity on the oxygen transfer efficiency was studied. Results have evidenced that regrouping the diffuser grids and applying a horizontal flow could lead to a significant limitation in the impact of the air flow rate on the oxygen transfer efficiency. Finally, the use of the off gas method to determine the oxygen transfer efficiency of an aeration system at a given air flow rate led to the definition of a relationship, that enabled the evaluation of the system oxygenation capacities at air flow rates different from the one at which the measurements were initially performed.

  • optimization of oxygen transfer in clean water by Fine Bubble diffused air system and separate mixing in aeration ditches
    Water Science and Technology, 1998
    Co-Authors: G Deronzier, Ph. Duchène, A Heduit
    Abstract:

    The influence of design parameters on the transfer of oxygen was studied in different ring ditches equipped with Fine Bubble membrane air diffusers and separate mixing. The results produced evidence that the oxygen transfer efficiency (OTE) decreases when the air flow rate per diffuser increases. OTE increases asymptotically with the horizontal water flow (50% for velocity up to 0.5 m/sec). It increases also when the diffuser modules are brought closer together. Theoretical analysis enabled ranking of the impact of the design parameters on which the oxygen transfer is dependent, namely the interfacial area (a) and the oxygen transfer coefficient (Kl). The increase in the air flow rate per diffuser essentially reduces the interfacial area by an increase in the diameter of the initial air Bubbles and by a reduction of the contact time due to an acceleration of the “spiral flows” (vertical rotation of water flow). The horizontal rotation of water increases the interfacial area most probably by decreasing the diameter of the initial air Bubbles and by a lengthening of the contact time resulting from a reduction in the large spiral flows. Bringing the diffuser modules closer together makes longer the contact time by a reduction in the large spiral flows.

Zhenya Zhang - One of the best experts on this subject based on the ideXlab platform.

  • characteristics of ultra Fine Bubble water and its trials on enhanced methane production from waste activated sludge
    Bioresource Technology, 2019
    Co-Authors: Di Wang, Xiaojing Yang, Caixing Tian, Noriko Kobayashi, Motoyoshi Kobayashi, Yasuhisa Adachi, Kazuya Shimizu, Zhenya Zhang
    Abstract:

    Abstract In this study biogas production efficiency was evaluated by adding ultra-Fine Bubble water (UFBW) into waste activated sludge (WAS) through anaerobic digestion (AD). Four kinds of gases, i.e. Air, N2, CO2 and H2 were introduced into tap water (TW) to prepare the UFBW with their properties being first investigated. Results show that hundreds of millions of nanoscale Bubbles with the negative zeta potential could be stable in the UFBW for longer than two weeks whereas almost no nanometer Bubbles could be detected in the raw TW. As for their impact on subsequent AD of WAS, the cumulative methane production with the addition of UFBW was 14–21% higher than that from the raw TW addition group. Interestingly, the Air-UFBW also could promote the biogas production in this study, which is different from the common understanding of AD, an obligate anaerobic process.

Di Wang - One of the best experts on this subject based on the ideXlab platform.

  • characteristics of ultra Fine Bubble water and its trials on enhanced methane production from waste activated sludge
    Bioresource Technology, 2019
    Co-Authors: Di Wang, Xiaojing Yang, Caixing Tian, Noriko Kobayashi, Motoyoshi Kobayashi, Yasuhisa Adachi, Kazuya Shimizu, Zhenya Zhang
    Abstract:

    Abstract In this study biogas production efficiency was evaluated by adding ultra-Fine Bubble water (UFBW) into waste activated sludge (WAS) through anaerobic digestion (AD). Four kinds of gases, i.e. Air, N2, CO2 and H2 were introduced into tap water (TW) to prepare the UFBW with their properties being first investigated. Results show that hundreds of millions of nanoscale Bubbles with the negative zeta potential could be stable in the UFBW for longer than two weeks whereas almost no nanometer Bubbles could be detected in the raw TW. As for their impact on subsequent AD of WAS, the cumulative methane production with the addition of UFBW was 14–21% higher than that from the raw TW addition group. Interestingly, the Air-UFBW also could promote the biogas production in this study, which is different from the common understanding of AD, an obligate anaerobic process.

Nicolae Băran - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Fine Bubble Generator Architecture on Time Variation of Dissolved Oxygen Concentration in Water
    Revista De Chimie, 2019
    Co-Authors: Nicolae Băran, Mihaela Constantin, Beatrice Tanase, Edgar Moraru, Corina Ioana Moga
    Abstract:

    The paper presents two constructive solutions in the field of Fine Bubble generators that serve to aerate the water. Two installations for experimental researches have been designed and built in connection with the two constructive solutions. The dissolved oxygen concentration was experimentally determined. The theoretical and experimental results for the two constructive solutions are compared showing a good coincidence in relation to the results reported in the literature.

  • Researches Regarding the Use of Additive Technologies in the Construction of Water Aeration Elements
    Proceedings of the International Conference of Mechatronics and Cyber-MixMechatronics – 2018, 2018
    Co-Authors: Octavian Dontu, Nicolae Băran, Beatrice Tanase, Moga Corina Ioana, Gheorghe I. Gheorghe, Edgar Moraru
    Abstract:

    The paper presents the technology of execution of a Fine Bubble generator; the air inlets in the water are O 0.1 mm and made in silicon plates. The scheme of the experimental installation where this Fine Bubble generator is fitted is presented. The end of the paper shows the methodology of the researches and the obtained results.

  • Decrease of Energy Consumption in the Case of Water Oxygenation Processes
    Energy Procedia, 2014
    Co-Authors: Mihaela Vlăsceanu, Nicolae Băran, Mihai Băran
    Abstract:

    Abstract The paper aims to demonstrate that Fine Bubble generators manufactured by spark erosion are more efficient that generators endowed with porous diffusers. Pressure losses experimentally established are presented and energy consumption needed for water oxygenation is calculated. The advantages of using Fine Bubble generators endowed with plates with nozzles manufactured by spark erosion are emphasized.

  • Researches Regarding Water Aeration Using a New Type of Fine Bubble Generator
    Advanced Materials Research, 2014
    Co-Authors: Mihaela Vlăsceanu, Nicolae Băran, Mihai Băran
    Abstract:

    The purpose of the paper is to demonstrate that the age of porous diffusers manufactured by ceramic, plastic or other porous materials declined. Following theoretical and experimental researches, the author built a new type of Fine Bubble generator whose nozzle plate is manufactured by spark erosion. The constructive solution of the Fine Bubble generator is presented; the scheme of the experimental stand developed at POLITEHNICA University of Bucharest is subsequently exposed. The final section of the paper presents the results of the experimental research, which are compared to data existing in specialty literature.

  • the determination of dissolved oxygen concentration in stationary water
    Applied Mechanics and Materials, 2013
    Co-Authors: Ionela Mihaela Călusaru, Nicolae Băran, Adrian Costache
    Abstract:

    In the paper the differential equation of the transfer speed of the oxygen towards water is numerically integrated, software is written and theoretical results are presented. A setup for experimental tests regarding the functioning of Fine Bubble generators was designed and built in the frame of the Department of Thermotechnics, Engines, Thermic and Refrigeration Plants laboratory. Measurements regarding the increase of the concentration of oxygen dissolved in water were performed. Theoretical and experimental results were compared.

Yasuhisa Adachi - One of the best experts on this subject based on the ideXlab platform.

  • characteristics of ultra Fine Bubble water and its trials on enhanced methane production from waste activated sludge
    Bioresource Technology, 2019
    Co-Authors: Di Wang, Xiaojing Yang, Caixing Tian, Noriko Kobayashi, Motoyoshi Kobayashi, Yasuhisa Adachi, Kazuya Shimizu, Zhenya Zhang
    Abstract:

    Abstract In this study biogas production efficiency was evaluated by adding ultra-Fine Bubble water (UFBW) into waste activated sludge (WAS) through anaerobic digestion (AD). Four kinds of gases, i.e. Air, N2, CO2 and H2 were introduced into tap water (TW) to prepare the UFBW with their properties being first investigated. Results show that hundreds of millions of nanoscale Bubbles with the negative zeta potential could be stable in the UFBW for longer than two weeks whereas almost no nanometer Bubbles could be detected in the raw TW. As for their impact on subsequent AD of WAS, the cumulative methane production with the addition of UFBW was 14–21% higher than that from the raw TW addition group. Interestingly, the Air-UFBW also could promote the biogas production in this study, which is different from the common understanding of AD, an obligate anaerobic process.