INTRODUCTION
Aeration can be described by the process in which air drawn in is brought in circulation and mixed with a liquid body. Aeration facilitates close contact between air and water for the removal of dissolved gases and ensures the oxidation of dissolved metals and even Volatile Organic Chemicals (VOCs).
DESCRIPTION
Aeration in wastewater treatment
A thorough and evenly spread of supply of oxygen within an aeration system is significant for an efficacious treatment of wastewater as this in order to foster microbial growth in the effluent to be treated. In both industrial scale and municipal treatment of wastewater, aeration is categorized as a secondary treatment process. Aeration is part of the activated sludge process whereby microbial growth in the wastewater is promoted through the distribution of oxygen supply through an aerating device. The grown microbes are to feed on organic material present within the effluent which in hand causes flocculation of activated sludge that easily sediments after a period of time. Once settled at the bottom of separate sedimentation or clarifying tank, the microbes facilitating the deposition of “activated sludge” are recycled back to the aeration vessel to increase rate of decomposition of organic material.
Application of ejector/jet pump for aeration
An ejector or a jet aerator can be applied in this process in order to entrain air that is either drawn from the atmosphere of blown in by a separate unit and induce its mixing with liquid simply for the aeration and mixing in a vessel containing wastewater to be treated. To put simply, liquid brought into circulation is pumped from a targeted tank and into the jet pump where it is accelerated through a jet. This process will result in the formation of a region of high velocity and low pressure into which the required air is drawn and mixed with the liquid where both immiscible process streams are dispersed into a main continuous phase. The conditions allow for favorable mixing ratios. The motive jet disperses the air which is at low motive pressure in a finite number of small bubbles which are subjected to vigorous mixing with the motive flow within the mixing zone. This mixture is subsequently injected into the aeration vessel at high turbulence flow.
As the mixture is continually channeled through the ejector, where a pressure boost by Bernoulli’s principle is induced to overcome the backpressure formed by the head of liquid in the predeceasing containment vessel. The high energy turbulent fluid flow is discharged with a velocity that is capable of entraining the surrounding liquid, following which, the mixture or relatively lower density rises surface of the wastewater to complete the aeration process. The jet pump ensures the supply of optimal oxygen concentration and a high shear mixing of wastewater in the vessel. The process is not hindered even with a high composition of organic material concentration in the wastewater to be treated as optimal flow velocities can still be achieved to prevent excess solid deposits on the vessel floor.
Key Advantageous
- Increased oxygen efficiency – projected small bubbles at high turbulence induces large point of contact between air and wastewater
- No moving parts – unlike conventional blower used for wastewater aeration
- Avoid deposition on vessel floors due to jet flow
- Jet aeration take up less energy compared to conventional diffused aeration systems