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Related Concept Videos

Diffusion01:12

Diffusion

Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
Gas Exchange and Transport01:20

Gas Exchange and Transport

Gas exchange, the intake of molecular oxygen (O2) from the environment and the outflow of carbon dioxide (CO2) into the environment, is necessary for cellular function. Gas exchange during respiration occurs largely via the movement of gas molecules along pressure gradients. Gas travels from areas of higher partial pressure to areas of lower partial pressure. In mammals, gas exchange occurs in the alveoli of the lungs, which are adjacent to capillaries and share a membrane with them.
Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion03:48

Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion

Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many different directions before reaching the desired target. At room temperature, a gaseous molecule will experience billions of collisions per second. The mean free path is the average distance a molecule travels between collisions. The mean free path increases with decreasing pressure; in general, the mean free path for a gaseous molecule will be...
Respiration and Gaseous Exchange01:20

Respiration and Gaseous Exchange

The intricate interplay between the cardiovascular and respiratory systems is crucial for efficiently transporting respiratory gases throughout the body. Let us explore the cardiovascular system's multifaceted functions, emphasizing its pivotal role in gas exchange.
Respiration involves the exchange of gases, especially oxygen (O2) and carbon dioxide (CO2), between the alveoli and body cells, a process facilitated by blood circulation. As a result, the cardiovascular system, which involves the...
Diffusion01:21

Diffusion

Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
External and Internal Respiration01:24

External and Internal Respiration

External respiration occurs in the lungs, and it is the first step in the journey of oxygen inside the body. When we inhale, oxygen enters our lungs and diffuses across the thin alveolar membrane. The alveoli are tiny, air-filled sacs that provide a vast surface area for gas exchange. Oxygen in the alveoli has a higher partial pressure (105 mmHg) than in the adjacent pulmonary capillaries (40 mmHg), establishing a pressure gradient. As a result, oxygen molecules move from the alveoli into the...

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Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling
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Gas transfer from air diffusers.

Erica L Schierholz1, John S Gulliver, Steven C Wilhelms

  • 1Brown and Caldwell, 30 East 7th Street, Suite 2500, St. Paul, MN 55101, USA.

Water Research
|February 24, 2006
PubMed
Summary
This summary is machine-generated.

This study quantifies oxygen transfer in aeration systems, developing equations to predict bubble and surface mass transfer coefficients based on airflow and depth. Fine bubble diffusers show significantly higher oxygen transfer rates than coarse bubble diffusers.

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Area of Science:

  • Environmental Engineering
  • Water Treatment Technologies
  • Mass Transfer

Background:

  • Diffused aeration systems are crucial for oxygen transfer in water treatment.
  • Accurate prediction of oxygen mass transfer coefficients is essential for optimizing aeration system design and performance.
  • Existing models may not fully capture the complex interplay of factors influencing oxygen transfer in deep water bodies.

Purpose of the Study:

  • To separately determine bubble and surface volumetric mass transfer coefficients for oxygen (k(L)a(b) and k(L)a(s)).
  • To develop empirical characterization equations for k(L)a(b) and k(L)a(s) based on key operational parameters.
  • To enable prediction of oxygen gas transfer in deep tanks and reservoirs.

Main Methods:

  • Conducted 179 aeration tests across a range of diffuser depths (2.25 to 32 m).
  • Utilized the DeMoyer et al. mass transfer model to analyze oxygen transfer.
  • Developed empirical correlations relating k(L)a(b) and k(L)a(s) to airflow (Qa), diffuser depth (hd), cross-sectional area (Acs), and volume (V).

Main Results:

  • k(L)a(b) increases with gas flow rate and depth, decreases with water volume.
  • Fine bubble diffusers exhibit k(L)a(b) approximately six times higher than coarse bubble diffusers.
  • k(L)a(s) increases with gas flow rate and diffuser depth.

Conclusions:

  • The developed characterization equations accurately predict oxygen transfer across bubble interfaces and the free surface.
  • These equations are applicable to diffused aeration systems in deep tanks and reservoirs up to 32 m depth.
  • The findings provide valuable insights for optimizing aeration efficiency in various water treatment applications.