Advantages

Jet aeration systems use less energy than other diffused aeration systems. In actual wastewater treatment plants, side-by-side comparisons have shown energy reductions of up to forty percent. Figures are similar when compared with pure oxygen or mechanical aeration systems.

Jet aerators have replaced low and high speed aerators at several installations. Lower operating power and lower maintenance costs have been the reason for all replacements.

Alpha factor is the ratio of the oxygen transfer rate in wastewater to the oxygen transfer rate in clean water. Alpha factor is dependent on the aeration device used and also on the presence of chemicals such as surfactants in the wastewater.

Jet aerators produce a high alpha factor in pulp and paper mill wastes. The high alpha factor is due to the presence of surfactants in pulp and paper wastewater.

Oxygen transfer is enhanced due to the high shear at the gas/liquid interface. Typical alpha factors achieved with various aeration devices are shown below.

High shear aeration devices such as jet aerators yield a higher alpha factor due to surface renewal at the gas/liquid interface. Low shear aeration devices such as fine bubble diffusers (membrane or ceramic) yield a lower alpha factor because of insufficient renewal (oxygen saturation) at the gas/liquid interface.

All aeration systems are standardized for performance at standard conditions. Therefore, the process oxygen (AOR) is converted to standard oxygen (SOR) and is inversely proportional to the alpha factor. For this reason aeration systems with low alpha factors must be designed for a higher SOR.

A jet aeration system by Mixing Systems, Inc. consists of quality components that have an established reputation for reliability.

• Materials of construction are durable and resistant to abrasion, corrosion, and ultraviolet light.
• The jet nozzles used by Mixing Systems, Inc. have no moving parts that can wear out and no small passages to clog.
• Pumps and blowers are normally placed outside the tanks where they can be easily serviced.

In addition, the system is designed and manufactured to minimize field installation labor. Jet assemblies and piping are typically fiberglass which is lightweight, adaptable and easily installed.

All aeration and mixing occur below the surface so there is no mist or spray problems. In addition, no icing problems occur because the aeration and mixing units eliminate thermal stratification, thus preventing freezing.

Jet aerators have been used in tanks with 13 to 65 ft (4 to 20 meters) liquid depth. In deep tanks, due to the hydrostatic pressure of the bubbles, the initial and average bubble size is smaller than in shallow tanks. Smaller bubbles result in high mass transfer due to the following reasons:

• Higher surface area in the tank volume.
• The bubble stays in the tank longer due to the lower velocity of the rise.
• Higher pressure in the bubbles produce a greater driving force for oxygen transfer.

Mixing in deep tanks is provided from the bottom of the tank to the top. For this reason, jet aerators are not limited to just shallow tanks. The jet aerators provide maximum mixing near the bottom of the tank.

Jet aerators have been used in over one hundred pulp and paper mills. Jet aeration is a prevailing, proven technology that achieves high oxygen transfer efficiencies with minimum maintenance and minimum operator attention.

Jet aeration systems are designed for a twenty year life. These systems are designed so there is no need to drain the tanks for maintenance purposes. The pumps and blowers, which are generally the only components that require maintenance, are placed outside the tanks.

Jet aerators have been used in over one hundred pulp and paper mills. Jet aeration is a prevailing, proven technology that achieves high oxygen transfer efficiencies with minimum maintenance and minimum operator attention.

Jet aeration systems are designed for a twenty year life. These systems are designed so there is no need to drain the tanks for maintenance purposes. The pumps and blowers, which are generally the only components that require maintenance, are placed outside the tanks.

With the jet aeration system, both mixing and oxygen transfer can be independently controlled. Mixing is regulated by the recirculation pump. The level of oxygen transfer is controlled by the amount of air the blower releases to the jet aeration system.

Efficient mixing and oxygen transfer will yield an effluent which is non-toxic. When the wastewater is properly treated, 100% fish survival will occur in 100% effluent.

AOX (adsorbable organic halogens) are formed by a chemical reaction from the pulp bleaching processes which use chlorine or chlorine dioxide as bleaching agents. Jet aeration systems produce acceptable AOX levels in the effluent. Efficient mixing results in low AOX effluent.

A pneumatic backflush system can virtually eliminate all in-basin maintenance and manual cleaning, thereby maintaining high oxygen transfer rates and efficiencies.

By simply shutting off the pump, opening the backflush valve and continuing to supply air to the system, the unit’s aerodynamic design converts the submerged aeration system into a pneumatic air lift pump.

In the backflush mode, air flow blows backward through the system, displacing the liquid in the liquid distribution line and pumping the surrounding liquid in the reverse direction through the jets and liquid lines. This cleans the jet nozzles and the submerged aeration system of fouling material and debris. Most plants backflush their aeration tank once each month to maintain maximum efficiency.