What is mass transfer of oxygen?
What is mass transfer of oxygen?
During the aeration process, the mass transfer is mostly from the water surface to the inside of the liquid body. The principals of oxygen mass transfer depend on the resistance to the oxygen mass transfer, which occurs in the liquid phase. So the oxygen mass transfer coefficient in the gas phase is neglected.
What is the oxygen transfer rate?
Oxygen transfer is often the rate-limiting step in the aerobic bioprocess due to the low solubility of oxygen in the medium. The possible increasing on OTR due to the oxygen consumption by the cells is taken into account through the use of the biological enhancement factor.
What is the actual mass of oxygen transferred per unit time?
Explanation: The OTR is the actual mass of oxygen transferred per unit time and it is the key process variable for design. The DO saturation concentration is the concentration of dissolved oxygen at saturation with no reactions in the liquid. 6.
How do you calculate oxygen transfer?
The rate of oxygen mass transfer (dC/dt, gO2 •m-3•d-1) is then multiplied by the volume (V, m3) of the aerator to yield the oxygen transfer rate (OTR, gO2•d-1 ), a key input in diffuser design.
What is a good oxygen uptake rate?
The oxygen uptake rate will indicate whether or not biological treatment is complete. When all (or most) of the organics have been oxidized, which means all (or most) of the food has been consumed, the microorganisms will have reached endogenous respiration and you will have an OUR value typically <9.0 mg Oxygen/L/hr.
Is used in determination of oxygen transfer rate?
A new approach is proposed for the simultaneous determination of the volumetric oxygen transfer coefficient (KLa) and the oxygen uptake rate (OUR) in bioreactors. A polarographic dissolved oxygen electrode is used to monitor the oxygen concentration during a switch of aeration gas composition.
What does oxygen transfer mean?
Oxygen transfer, the process by which oxygen is transferred from the gaseous to the liquid phase, is a vital part of a number of wastewater treatment processes. Oxygen can be supplied by means of air or pure oxygen bubbles introduced to the water to create additional gas-water interfaces.
How do you increase oxygen transfer rate?
For a successful aerobic cultivation, a good oxygen transfer is vital. It can be increased by: Creating a bigger surface of gas bubbles (kLa) by increasing gas flow and stirrer speed and by adding baffles. Creating a higher O2 concentration gradient by adding O2 to gasmix and increasing the pressure.
What is kLa formula?
For 860 mL working volume: KLa (h-1) = 1.5803x liquid speed (cm/sec) Knowing the liquid flow rate as well as the bioreactor type (fixed-bed height, compaction rate, working volume), the liquid flow rate can be easily converted in stirring speed (RPM) using the dedicated application note (Characterization of the liquid …
What does kLa depend on?
The values of kLa are affected by many factors, such as geometrical and operating characteristics of the reactor (type of impeller, the geometry of the bioreactor, the agitation speed and the air flow rate), media composition and properties, concentration and microorganism’s morphology and biocatalyst’s properties [3].
How is the transfer rate of oxygen calculated?
The dissolved oxygen concentration, for all practical purposes, will be zero and the KLa may then be calculated from the equation: where OTR is the oxygen transfer rate.
How does the mass transfer of oxygen affect cell growth?
The mass transfer of oxygen transfer is often a limiting factor in bioreactors. If oxygen is limited, cell growth and product formation can be affected. The oxygen transfer rate (OTR) is influenced by the physical properties of the gas and liquid, operational conditions, geometric parameters, and the consumption rate by the cells.
How to describe the transfer of oxygen from gas to liquid?
The oxygen transfer from a gas phase to a liquid phase can generally be described as follows: OTR = k L a ⋅ L O 2 ⋅ p abs ⋅ (y O 2, headspace − y O 2, liquid)
When is the mass transfer coefficient m large?
If the gas is rather insoluble in the liquid, such as oxygen or nitrogen in water, then m is large. In this case, from Equation I.14, the overall mass transfer coefficient KL is equal to the liquid phase mass transfer coefficient, kL.
