Evaluation of oxygen transfer rates in stirred-tank bioreactors for clinical manufacturing

The efficiency of the aeration system in a full-scale activated sludge basin with 3 separately controlled aeration zones was improved for the low loading period in summer. The air flow rate to each aeration zone is currently regulated to hold a preset dissolved oxygen concentration (DO). Four different DO setpoint combinations were tested, each one for a one week period, using dynamic off-gas testing to measure the standardised oxygen transfer efficiency (αSOTE). As the DO setpoints were lowered, the total air flow rate to the basin decreased initially. A low DO in the first zones slowed biomass activity and pushed the load towards the end of the aeration basin. The relationship between αSOTE and the specific diffuser flow rate qD is different for each zone. In Zone 1 there was a strong decrease in αSOTE as qD increased, while Zones 2 and 3 were fairly independent of qD, Zone 2 at a higher level than Zone 3. Aeration costs were reduced by 15% for the most efficient combination. To achieve even more savings, a control strategy adjusting oxygen transfer rates over the aeration basin to the necessary oxygen transfer rates is suggested. It is based on changing the DO setpoints to reach the lowest total air flow rate while meeting the effluent requirements.

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Effect of Palm Oil on Oxygen Transfer in a Stirred Tank Bioreactor

Journal of Applied Sciences ◽

10.3923/jas.2010.2745.2747 ◽

2010 ◽

Vol 10 (21) ◽

pp. 2745-2747 ◽

Cited By ~ 6

Author(s):

Suhaila Mohd Sauid ◽

Veluri V.P.S. Murthy

Keyword(s):

Palm Oil ◽

Oxygen Transfer ◽

Stirred Tank ◽

Stirred Tank Bioreactor

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Determination of oxygen transfer rate to a rotating biological contactor by microelectrode measurement

Water Science & Technology ◽

10.2166/wst.1994.0794 ◽

1994 ◽

Vol 29 (10-11) ◽

pp. 471-477 ◽

Cited By ~ 6

Author(s):

K. Nishidome ◽

T. Kusuda ◽

Y. Watanabe ◽

M. Yamauchi ◽

M. Mihara

Keyword(s):

Diffusion Layer ◽

Oxygen Transfer ◽

Transfer Rate ◽

Oxygen Transfer Rate ◽

Water Film ◽

Ammonia Nitrogen ◽

Concentration Profiles ◽

Rotating Biological Contactor ◽

Transfer Rates ◽

Do Concentration

With an oxygen microelectrode developed by the authors for the measurement of dissolved oxygen (DO) concentration profiles of biofilms in a rotating biological contactor (RBC), DO concentration profiles in the inside and outside of rotating biofilms were measured continuously in the air and water phases. Thicknesses of attached-water film (Lw) and the diffusion layer (Ld) formed on the biofilms were estimated from DO concentration profiles. The oxygen transfer rate to the biofilm was determined with measured DO concentration profiles and a steady state biofilm kinetic model by use of the thicknesses of attached-water film and the diffusion layer. The oxygen transfer rates obtained by two independent methods agreed well, so that the method of the measurement of DO concentration profilesis considered highly reliable. The conclusions in this study are summarized as follows: (1) Lw and Ld on a biofilm attached on a partially submerged rotating biological contactor were 50 and 70 μm thick, respectively; (2) The measured oxygen fluxes were about 10 g-O2/m2/day, and reasonably agreed with those calculated from removing rates of ammonia nitrogen.

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Fine Bubble Aeration Using a High Density Diffuser System

Water Science & Technology ◽

10.2166/wst.1992.0756 ◽

1992 ◽

Vol 26 (9-11) ◽

pp. 2437-2440 ◽

Cited By ~ 1

Author(s):

K. Thatcher

Keyword(s):

Activated Sludge ◽

Oxygen Transfer ◽

Oxygen Demand ◽

High Density ◽

Plant Performance ◽

Energy Usage ◽

High Quality ◽

Transfer Rates ◽

Fine Bubble ◽

Activated Sludge Processes

Current developments with the activated sludge processes with highly concentrated effluents highlight the requirement to (a) reduce energy usage (b) promote the production of high quality effluent. Having observed the efforts being made to improve plant performance we became aware that current methods had to be improved. It was also noted that a period of stagnation had occurred in the development of effective aeration systems. Improved aeration methods are needed which would allow for oxygen transfer efficiencies to be greater than 2kg/kWh. Such oxygen transfer rates should be continually variable in line with the oxygen demand prevailing at any given time. In our study of activated sludge plants we found that operational and electrical/mechanical maintenance was proving to be time consuming and very costly. With these problems in mind we have designed and developed the Fine Bubble High Density Diffuser System.

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Oxygen Transfer and Fragmentation of Aspergillus niger Pellets in Stirred Tank and Concentric-Duct Airlift Bioreactors

Industrial Biotechnology ◽

10.1089/ind.2020.29199.mmb ◽

2020 ◽

Vol 16 (2) ◽

pp. 67-74 ◽

Cited By ~ 2

Author(s):

Mariane M. Buffo ◽

Mateus N. Esperança ◽

Rodrigo Béttega ◽

Cristiane S. Farinas ◽

Alberto C. Badino

Keyword(s):

Aspergillus Niger ◽

Oxygen Transfer ◽

Stirred Tank ◽

Airlift Bioreactors

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Effect of orifice diameter, depth of air injection, and air flow rate on oxygen transfer in a pilot-scale, full lift, hypolimnetic aeratorA paper submitted to the Journal of Environmental Engineering and Science.

Canadian Journal of Civil Engineering ◽

10.1139/s08-047 ◽

2009 ◽

Vol 36 (1) ◽

pp. 137-147 ◽

Cited By ~ 9

Author(s):

K.I. Ashley ◽

D.S. Mavinic ◽

K.J. Hall

Keyword(s):

Flow Rate ◽

Oxygen Transfer ◽

Gas Flow ◽

Pore Diameter ◽

Oxygen Transfer Rate ◽

Pilot Scale ◽

Orifice Diameter ◽

Transfer Rates ◽

Oxygen Transfer Efficiency ◽

Design Factors

A pilot-scale, full lift, hypolimnetic aerator was used to examine the effect of diffuser pore diameter, depth of diffuser submergence, and gas flow rate on oxygen transfer, using four standard units of measure for quantifying oxygen transfer: (a) KLa20 (h–1), the oxygen transfer coefficient at 20 °C; (b) SOTR (g O2·h–1), the standard oxygen transfer rate; (c) SAE (g O2·kWh–1), the standard aeration efficiency and (d) SOTE (%), the standard oxygen transfer efficiency. Diffuser depth (1.5 and 2.9 m) exerted a significant effect on KLa20, SOTR, SAE, and SOTE, with all units of measure increasing in response to increased diffuser depth. Both KLa20 and SOTR responded positively to increased gas flow rates (10, 20, 30, and 40 L·min–1), whereas both SAE and SOTE responded negatively. Orifice diameter (140, 400, and 800 µm) exerted a significant effect on KLa20, SOTR, SAE, and SOTE, with all units of measure increasing with decreasing orifice size. These experiments demonstrate how competing design factors interact to determine overall oxygen transfer rates in full lift hypolimnetic aeration systems. The practical application for full lift hypolimnetic aerator design is to maximize the surface area of the bubbles, use fine (i.e., ~140 μm) pore diameter diffusers, and locate the diffusers at the maximum practical depth.

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