One of four multi-nozzle JETOX units in an MBR tank in Spain
Aquabio Ltd - Aeration & Mixing
Basic Principles
The basic principle of Jet Aeration exploits two phase nozzle technology to enable high velocity contact mixing of air (or oxygen) and a liquid.
For a comparison of different aeration methods please see this table.
Aquabio Ltd offer both Jet aeration and Slot aeration technologies please follow the above links for further information.
A single phase 'sidestream' of pressurised liquid is recirculated in a manifold and through a 'primary' jet nozzle. Immediately after this nozzle an air stream is injected at low pressure either directly from the atmosphere or from low-pressure air blowers. Intimate contact mixing is achieved at this interface before the combined air/liquid stream passes through a 'secondary' nozzle, at high velocity, and into the main body of mixed liquor.
The effect of a sudden drop in pressure at the primary nozzle assists to entrain air into the secondary nozzle chamber and the high velocities at the interface cause a shear effect producing fine bubbles. This mixture of liquid and fine bubbles travels through the secondary nozzle and extends as a 'plume' into the tank.
The resulting 'plumes' from each of the equally spaced jet nozzles are directed horizontally to the tank base, with a slight downward incline to increase the effective liquid depth and oxygen dissolution efficiency (Henry's Law).
Principle of Jet Aeration
The air flow can be easily regulated from the air source, therefore controlling the amount of oxygen supplied (and power) in accordance with the relative demand of the system. With the pump sidestream still operating, complete mixing of the tank is retained even during periods of very low oxygen demand.
Please see below for a list of advantages for Jet Aeration and Mixing systems.
Although systems are designed with optimum nozzle separation and air/liquid ratios, certain applications require the JETOX eductor to provide a third phase of mixing. This helps extend the bubble plume during periods of high air/liquid entrainment and protect against 'coarse bubble breakout' which results in deterioration in oxygen transfer efficiency.
Jet Aeration is particularly suited to: aeration of high strength industrial wastestreams; applications with large incoming load fluctuations; aerobic sludge conditioning/digestion processes and single tank processes requiring sequential aerobic/anoxic treatment or batch operation.
Jetox pod in a bioreactor for a jam factory
A Jetox manifold in a bioreactor for a sauce factory
Features of Jet Aeration & Mixing
Aeration
- Self entraining or blower operation
- Separate control of mixing and aeration functions (e.g. for Nitrification/Denitrification)
- Ideal for continuous process or "batch" reactors
- High alpha factor characteristics especially in selected industrial wastestreams (resulting in significant powersaving and high actual aerator efficiencies into the wastewater)
- Solids handling
- Excellent mixing properties with directional patterns designed to suit reactor geometry
- Inexpensive installation with less in tank pipework and peripheral items (e.g. gantries, walkways etc.)
- Easily accessible and low maintenance
- Deep tank capabilities due to lower relative air blower pressures, resulting in a greater choice of plant ‘footprint’ and process options
- Extremely robust and available in a variety of manifold materials to suit the wastewater composition
- Sub surface aeration reduces aerosols
Mixing
- Secondary liquid entrainment vastly improves tank ‘turnover’ rates
- Reduced power costs
- Solids handling
- Directional patterns designed to suit reactor geometry.
- Extremely robust and available in a variety of manifold materials to suit the wastewater characteristics
- Inexpensive installation
- Easily accessible and low maintenance
Jetox pod installed in an MBR tank