MIXING SYSTEMS, INC.
7058 Corporate Way, Dayton, Ohio 45459, USA
Fine bubble aeration
Fine Bubble Aeration
Mixing Systems, Inc. jet aeration system is a submerged aeration system that produces fine gas bubbles and enhances mixing between the gas and liquid phases. The fine bubbles and intimate contacting results in increased absorption efficiency.
Mixing Systems, Inc. jet aeration systems provide both environmentally conscious and cost effective operation. Built of quality components with an established reputation for reliability, Mixing Systems' jet aeration systems have shown energy reductions of up to forty percent over other aeration methods. Less operating horsepower is required which results in substantial energy savings. In addition, during periods of low service demand, air flow rates can be reduced by controlling and varying the blower output. By regulating the air flow to the aeration system, oxygen transfer rates can be controlled without affecting the mixing efficiency or solids suspension and additional energy savings are achieved.
Superior Oxygen Transfer
In a comparison of jet aeration methods, submerged jet aerators, such as those supplied by Mixing Systems, Inc. report a higher oxygen transfer than other aeration methods.
Higher Alpha Factor
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 on the presence of chemicals (such as surfactants) in the wastewater. Jet aeration systems yield a higher alpha factor than fine pore membrane and ceramic-type aeration systems. Because of the high shear within the jet nozzles, jet aerators produce a high surface renewal at the gas/liquid interface.
Most wastewaters have surfactants present. The surfactants create a resistance to oxygen transfer at the gas/liquid interface. The film thickness is the smallest (lowest resistance) with high shear devices such as jet aerators and surface aerators. In actual wastewater treatment plants, due to the high alpha factor achieved by the jet aerators, a lower design standard oxygen is required than with fine pore diffused aeration systems. This is one of the benefits of using jet aerators in wastewater generated from pulp and paper, pharmaceutical, chemical and brewery industries. These wastewaters normally have surfactants present in them and therefore jet aerators are very efficient. The total energy consumed for treatment of these wastewaters is 20% to 30% lower than with fine pore diffused aeration systems.
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 higher SOR.
Jet aeration systems, such as those supplied by Mixing Systems, Inc., use less energy than other diffused aeration systems. In actual wastewater treatment plants, side-by-side comparisons with diffused aeration systems have shown energy reductions of up to forty percent. Figures are similar when compared with pure oxygen or mechanical aeration systems.
Mixing Systems, Inc. jet aerators have replaced low-speed and high-speed aerators on several installations. In all cases, low operating power and lower maintenance costs have been the reason for replacing lesser aeration systems with jet aeration.
Thermal Energy Conservation
Submerged jet aerators, such as those supplied by Mixing Systems, Inc. , conserve thermal energy of the wastewater and helps maintain high BOD removal and nitrification rates throughout the wintertime. All aeration and mixing occurs below the surface so there is no mist or spray problems that lead to expensive heat losses. In addition, no icing problems occur because the aeration and mixing units eliminate thermal stratification, thus preventing freezing. No damage or impairment of operating efficiency is caused by accidental freezing.
The jet aeration system is installed near the bottom of the tank and does not splash wastewater into the atmosphere. Surface aerators splash wastewater into the atmosphere to transfer oxygen. In the process, the surface aerators strip volatile organic compounds (VOC) into the atmosphere. Due to the low quantity of air required by the Mixing Systems, Inc. jet aeration system, this VOC stripping to the atmosphere is minimized.
Consistent, Uniform Mixing
Each jet discharges a high-energy stream of small air bubbles and recirculated mixed liquor into the bottom region of the aeration basin. The combined action of the horizontally directed jet flow and the rising air plume provide mixing in the aeration tank and minimizes settling of biological solids.
With a jet aeration system by Mixing Systems, Inc. , 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.
During non-peak periods, airflow rates can be reduced and substantial power savings achieved. By regulating the airflow to the aeration system, oxygen transfer rates can be controlled without affecting the mixing efficiency or solids suspension and additional energy savings are achieved. The airflow can be turned off completely to achieve denitrification and phosphorus removal. The tanks can also be run in the aerobic and anoxic modes to control nitrification or denitrification and carboneous removal.
Deep Tank Operation
Mixing Systems, Inc. jet aerators have been used in tanks with 13 to 65 feet (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:
Mixing in deep tanks is provided from the bottom of the tank to the top. For this reason, jet aerators are not limited to shallow tanks. Mixing Systems, Inc. jet aerators provide maximum mixing near the bottom of the tank where solids would otherwise settle.
Low off Gases
In aeration tanks with high volatile organic compounds (VOC), it is preferable to use minimum quantities of air. This results in less off gases needing to be oxidized at high temperatures in thermal oxidizers. Mixing Systems, Inc. jet aeration technology uses deep reactors and produces micron size bubbles. The amount of air utilized is reduced so that comparatively small quantities of gas require thermal oxidation treatment. In addition, jet aeration systems do not splash water so VOC diffusion into the atmosphere is minimized.
In instances where low gas emissions into the atmosphere is important, the Mixing Systems, Inc. jet aeration systems can use pure oxygen or oxygen enriched air to increase the partial pressure of oxygen and reduce quantities of off gases.
In deep aeration tanks, the oxygen absorption efficiency is in the range of 25% to 80%. Therefore, for the same oxygen transfer, the amount of air required with the jet aeration system is 25% to 50% of what is required with conventional diffused aeration systems. In instances where the off gases from the aeration tanks have to be treated, such as thermal oxidation, lower quantities of air needs to be treated with jet aeration systems.
Toxicity RemovalToxicity in wastewater is caused by chemicals such as resin acids. Good mixing in the aeration tank and high BOD removal efficiencies result in a nontoxic effluent. The raw influent from the primary clarifier can be directly sent through the jet aeration system where it is immediately contacted with oxygen. This contact of the concentrated influent wastewater before release into the aeration tank dilutes the toxins and minimizes the shock loads in the aeration tank. The wastewater is then dispersed through a series of jet aeration nozzles before release into the aeration tank.
Efficient mixing and oxygen transfer will yield a nontoxic effluent. When the wastewater is properly treated 100% fish survival will occur in 100% effluent. AOX (adsorbable organic halogens) are formed by 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 a low AOX effluent.
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Mixing Systems, Inc.
7058 Corporate Way, Dayton, Ohio 45459, USA
Phone: 937-435-7227, Fax: 937-435-9200