Patent Application
20120021507
The disclosure relates to the methods and systems for introducing ambient gas into a liquid.
There is a need to dissolve various gases in a liquid. For example, in waste-water treatment, it is useful to dissolve oxygen or ozone in water. One known waste-water treatment method includes introducing oxygen in the water to support growth of aerobic bacteria. This is typically achieved by bubbling oxygen through the water. It is also useful to add ozone to water for killing bacteria and viruses, as well as for removing odors and colors. Such treatments are used, for example, in processing fruits and vegetables. The introduction of ozone is again typically achieved by bubbling ozone in the water. A difficulty associated with conventional air-bubbling methods is their appetite for electricity. In addition, such methods are inefficient. When air-bubbling is used, a considerable amount of time elapses before the level of dissolved gas reaches a useful level. As a result, a great deal of gas fails to dissolve and is ultimately wasted.
The present invention relates to the use of a rotating wheel to introduce a gas into a liquid medium. The wheel is covered by one or more net structures. The structures are formed by having ribs interconnecting with each other to form voids. When the voids are regularly shaped, each layer of the structure can be viewed as a mesh layer, or a net layer.
The wheel can be mounted to protrude above the surface of a liquid. As the wheel rotates, the voids in the net structures trap air bubbles. As these bubbles interact with the boundaries between the voids (e.g. the ribs in adjacent layers of netting), they become progressively smaller, and are therefore more prone to dissolve in the liquid.
In one aspect, the invention features a rotating wheel assembly for introducing an ambient gas into a liquid. The assembly includes a wheel plate having a face; and a net structure on the face. The wheel plate can be solid or not permeable to a liquid, such as water. The rotating wheel assembly can further include an axle passing through the wheel plate, the axle being positioned such that a portion of the wheel plate protrudes above the level of the liquid. The net structure can be made of aluminum, aluminum alloy, stainless steel, or ozone-resistant plastic. It can contain one or more layers of plastic or metal net on the face. The net can have mesh having a shape of diamond, square, or hexagon. The mesh can be of 0.5-2.0 cm in diameter.
In one embodiment, the assembly has a wheelward-most layer from the layers of net that contains a plurality of meshes having a first size, and a wheelward-least layer from the plurality of net layers that contains a plurality of net meshs having a second size, wherein the second size is larger than the first size.
In another embodiment, the above-mentioned face is a side face or a circumferential face of the wheel plate. For example, the wheel is a rolling tube covered by one or more layers of the net structures. See
The rotating wheel assembly can include a plurality of wheel plates, each having a face for placement of the net structure. It can include a first wheel plate; a second wheel plate mounted coaxially with the first wheel plate and separated from the first wheel plate along an axial direction; and a plurality of boards extending between the first and second wheels, the boards having faces. The net structure is disposed on the faces of the boards.
The invention also features a rotating wheel assembly for introducing a gas into a liquid. The assembly can include means for holding the liquid; means for entraining bubbles of the gas; and means for plunging the entraining means below a surface of the liquid and means for trapping and chopping off air bubbles of a large size into a smaller size.
In another aspect, the invention features an apparatus having multiple rotating wheel assemblies described above. The assemblies are assembled together in a bioreactor tank or chamber.
In another aspect, the invention features a bioreactor for introducing an ambient gas into a liquid. It contains a tank for holding the liquid; and a wheel assembly described above rotatably mounted in the tank. The bioreactor can further include an airtight lid for the tank. The gas can be air, oxygen, ozone, a fragrant gas, N2, or CO2. For air, oxygen, fragrant gas, N2, or CO2, the net structure can be made of plastic, aluminum, aluminum alloy, stainless steel, or plastic. For ozone, the net structure can be made of ozone-resistant plastic and the tank is airtight.
In the bioreactor, the liquid can contain chemicals, virus, microorganisms (e.g., bacteria or yeast), plant cells, or mammalian cells. The gas introduced into the liquid can treat the chemicals or kill the virus, microorganisms, plant cells, or mammalian cells. The liquid can contain water, industry wastewater, or sewage. Alternatively, the gas is required for the growth of the microorganisms or cells.
In one embodiment of the bioreactor, the tank further includes activated sludge, which can be used to treat polluted water. The activated sludge can be grown on a matrix, which can contain polymer non-woven cloth in between plastic nets. The activated sludge can be composed of saprotrophic bacteria but also can have a protozoan flora mainly composed of amoebae, Spirotrichs, Peritrichs including Vorticellids and a range of other filter feeding species. Other important constituents include motile and sedentary Rotifers.
In another aspect, the invention features a method of liquid treatment. The method includes repeatedly moving a net structure through a gas to be dissolved in the liquid; and plunging the net structure into the liquid, wherein the liquid is in a tank. The gas can be air, oxygen, ozone, fragrant gas, N2, or CO2. For air, oxygen, fragrant gas, N2, or CO2, the net structure can be made of plastic, aluminum, aluminum alloy, stainless steel, or plastic. For ozone, the net structure can be made of ozone-resistant plastic and the tank is airtight and the tank is airtight. The liquid can contain chemicals, virus, microorganisms, plant cells, or mammalian cells. The gas introduced into the liquid, can treat the chemicals or kill the virus, microorganisms (e.g., bacteria or yeast), plant cells, or mammalian cells. The liquid can contain water, industry wastewater, sewage, culture medium, or broth.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
The present invention relates to effectively transferring an ambient gaseous composition (e.g., ambient ozone, ambient air or oxygen, ambient nitrogen, ambient CO2 and ambient fragrant gases) into a liquid (e.g., water, wastewater and other liquids) by a novel multilayer net-covered rotating wheel method. See
Ozone is an effective agent to kill bacteria and viruses. It also oxidizes toxic materials and removes odor and color from water and wastewater. Current water treatment, food or vegetable processing and wastewater treatment often employ ozone-bubbling method to transfer ozone into the water for wastewater treatment. It can not utilize expensive ozone effectively, thus increasing cost and being harmful to its immediate environment. Therefore, this is need for alternatives to transfer ambient ozone directly into water and 100% utilize ozone.
Current biological wastewater treatment or microorganism culture often employs air-bubbling method to transfer oxygen into wastewater for suspension cultivation of activated sludge and microorganisms to improve water quality. The suspension cultivation of activated sludge and microorganisms by air-bubbling method is not an ideal process. For example, biomass of the suspended activated sludge and microorganisms is not higher enough to process large quantity of wastewater by using limited space. Meanwhile, dissolved oxygen level created by the bubbling oxygen transfer method is not good enough to support growth of large biomass of the activated sludge and microorganisms. In addition, mixing force of the bubbling oxygen transfer method is not strong enough to distribute the dissolved oxygen to support large biomass growth of the activated sludge microorganisms. Thus, there is a need for a more effective system to cultivate activated sludge and microorganism at large biomass and a better method to transfer oxygen or to make dissolved oxygen for supporting large biomass growth of the activated sludge microorganisms.
This invention provides a novel system and method for introducing a gaseous composition into a liquid composition as illustrated by
The systems and methods described herein can be used to transfer ambient oxygen and ozone (which is sealed in a chamber for 100% ozone transfer without leakage) into water or liquid and for low-cost and low-energy treatment of water, and wastewater. Basing on the above method, novel rotating wheel bioreactor systems (
The present invention also relates to novel bioreactors to high-density culture of microorganisms and culture of activated sludge at both suspension and attached status. Within the scope of the invention are methods to high-density culture of microorganisms and stably culture of activated sludge at larger biomass by using a stacked wall of polymer paper carriers packed in between plastic nets and a novel oxygen transfer method, the method comprised using the just-described system for wastewater treatment.
In one example, it includes the use of dissolved oxygen making wheels to culture high-density E-coli in suspension compared with a conventional impellor-based deep tank bioreactor (see
The systems and methods described herein can be used to high-density culture of microorganisms and the activated sludge at both suspension and attached status for treatment of wastewater. Based on the above methods, novel bioreactor systems (see
Below are a number of specific embodiments. A system for introducing gas into a liquid medium includes a tank 10, as shown in
Referring now to
The wheel 16 has, on one of its faces, a net structure 21 formed by an outer net/tessellation layer 20 and an inner net/tessellation layer 22. Net/Tessellation layers 20, 22, examples of which are shown in
The ribs 23 are made of a material that can withstand the effect of the gas present in the chamber 17. Thus, where the gas includes ozone, the ribs 23 are made of an ozone-resistant material. Other materials that can be used for ribs 23 include polypropylene, EVA/PE, synthetic glass, plastic, including ozone-resistant plastic, and metals, such as aluminum.
The cells 27 can be irregular or randomly shaped. However, in some embodiments, the cells 27 have a regular size and shape. In such embodiments, the tessellation layers can be viewed as mesh layers, or nets.
The cells 27 can be square, rectangular, hexagonal, rhombic, or parallelogram. In addition, the cells 27 from different mesh layers need not have the same shape. Thus, one might have an outer layer with rhombic cells and an inner layer with hexagonal cells.
In addition, there can be any number of mesh layers. As discussed in the experiments below, considerable improvement can be achieved with only one mesh layer. However, the dissolution rate increases as more layers are added.
As shown in
Although the stacking of mesh layers, or tessellation layers, on a wheel 16 is a useful way to construct the net structure 21, the net structure 21 can be constructed in any other way, for example by machining, casting, or etching.
In the particular case of a wheel with only two tessellation layers, as shown in
In operation, the tank 10 is partially filled with the liquid into which the gas is to be introduced. The level to which the tank 10 is filled is such that the wheel 16 partially protrudes above the surface of the liquid. Preferably, as much as half of the wheel 16 is above the liquid's surface. The chamber 17 is then filled with the gas. After the chamber 17 is filled, the motor 18 rotates the wheel 16 at a pre-defined rate for some pre-defined period.
Referring to
In some practices, gas is continuously fed into the chamber 17 so that a constant concentration or amount of gas is always present.
As the optimal level of dissolved gas is reached, the supply of gas is cut off, and the wheel 16 is allowed to spin for some time thereafter. During this period, whatever residual gas is in the chamber 17 dissolves in the liquid. This enables almost 100% utilization of the gas, depending on how long the wheel 16 is kept spinning after the gas supply has been cut off.
In one example, wheels having a 0.5 meter diameter and different numbers of tessellation layers were immersed in 110 liters of water in a chamber filled with oxygen. It was found that with no layers, it would take 20 minutes to reach a dissolved oxygen level of 100% from a baseline dissolved oxygen level of 0%. Adding a net structure with one layer to the wheel 16 reduced this time a mere 150 seconds. Adding a second layer to the net structure reduced the time further, to only 90 seconds.
In another experiment, the chamber was filled with 110 liters of water tinted by a blue ink, and the remaining portion of the chamber was filled with ozone. The same wheel diameter (0.5 meters) and rotation rate (90 rpm) was used. In this case, the water turned clear in 40 minutes when the wheel 16 had one tessellation layer, and turned clear in 25 minutes when a net structure with two tessellation layers was used.
The effectiveness of having a net structure with multiple tessellation layers can be seen in, e.g., Table 3 in Example 3 below, which shows the level of dissolved oxygen during the first six minutes of operation using different numbers of tessellation layers. In this experiment, the tessellation layers were made of aluminum, the wheel 16 was 1.0 m in diameter and spun at 53 rpm, and there were 650 liters of a 0.16 g/L aqueous solution of Na2SO3.
Gas dissolution assisted by net structures as described herein can be used in a variety of applications. For instance, the system can be used to introduce oxygen into waste-water, thus facilitating growth of aerobic bacteria. Or, the system can be used to disinfect water with ozone. Such water is useful for washing, and thereby disinfecting, vegetables or meats. Or the system can be used to introduce fragrant gas, for example a gas carrying a lemon scent, into water, or to introduce chlorine or other disinfectant gases into swimming pool water. Ozone treatments as described herein can also be used to pre-treat contaminated wastewater, such as phenol contaminated waste water.
An ozone treatment as described herein can also be used to treat contaminated ground water, as shown in
A bioreactor as described herein is sufficiently small and portable to be transported to a site on a truck 60, as shown in
The rate at which the wheel 16 introduces gas into a liquid depends on the structure of the wheel 16 and its accompanying net structure 21. Example 15 shows the extent to which several 0.25 m diameter wheels can dissolve oxygen within 7 minutes when rotated at 90 rpm.
Systems and methods as described herein can be adapted to facilitate high-density culture of microorganisms and culture of activated sludge, whether suspended or attached. For example, the system can be provided with a stacked wall of polymer paper carriers packed between plastic meshes, Examples of such a material include, but are not limited to, non-woven polymer fiber paper carriers and biocompatible plastic nets.
In additional embodiments, the rim 18 of the wheel 16 defines a circumferential face that can have a net structure 21 disposed thereon. This is particularly useful for wheel having a wide rim 18, such as that shown in
The expansion of wheel surface area devoted to a net structure, as shown in
Moreover, in the embodiment shown in
The configurations shown in
In
Moreover, as described herein, the net structure 21 is plunged into and out of the water by mounting it on a rotating structure. However, other mechanisms for plunging the net structure 21, or portions thereof, are possible. For example, the net structure 21 can be mounted on a reciprocating structure, such as a flat or curved board, that is repetitively plunged into and out of the water. Or the net structure 21 can be mounted on an endless belt that is looped between a rotating cylinder below the surface and another rotating cylinder above the surface.
The specific examples below are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. Without further elaboration, it is believed that one skilled in the art can, based on the description herein, utilize the present invention to its fullest extent. All publications cited herein are hereby incorporated by reference in their entirety. Further, any mechanism proposed below does not in any way restrict the scope of the claimed invention.
In this example, a modified bicycle wheel structure was used for the O2 transfer wheel construction as shown in
In order to generate micro-bubbles, we hypothesized that large air bubbles becomes micro-bubbles after 3 times of hitting by and interaction with (entraining microscopic bubbles during the interaction) metal or plastic or organic glass bars or surface of the nets and finally the solid surface (illustrated in
To transfer O3, we used plastic nets to avoid ozone's oxidization activity. We used ozone's capability to remove ink's blue color as a marker. Results in Table 2 indicate that the 2-layer net covered wheel had better ozone transfer capability.
As mentioned above, large air bubbles becomes micro-bubbles after 3 times of hitting on metal or plastic or organic glass bars of the nets and finally the solid surface (see
For the results shown in Table 3, a wheel of 1.0 meter diameter was used. Oxygen transfer is expressed by DO(%). Total volume of water is 650 L; and 0.16 g/L of Na2SO3 was loaded. The wheel rotation speed was 53 rpm.
For the results shown in Table 4, a wheel of 1.0 meter diameter was used. The oxygen transfer speed was expressed by KLA. Total volume of water was 650 L. 0.16 g/L of Na2SO3 is loaded. The wheel rotation speed was 53 rpm.
A wheel bioreactor assembly that had a wheel of 2.0M diameter was employed for O2 and O3 transfer. As shown in Table 5, the results indicated similar O2 and O3 transfer speeds.
In order to 100% transfer the environmental O3 into a sealed chamber for waster sterilization (Table 6), vegetable wash (Table 7), dish (Table 8) (ozone 40 mg/L), and meat cleaning (ozone 40 mg/L), we stopped wheel rotation 10 minutes after stopping O3 supply. Our gas O3 measurement indicated that no O3 exist after 10 minutes of rotation after O3 supply stopped. This indicated that all the O3 was 100% transferred into the water without leakage to the surrounding environment.
The above-described ambient gas transfer bioreactor was used to transfer fragrant gas (lemon scented) into water. The results (shown in Table 9 below) indicated rapid addition of fragrant gas (lemon scented) into the water.
The above-described bioreactor (illustrated in
The above-described bioreactor (illustrated in
The above-described bioreactor (illustrated in
One of industrial wastewater treatment examples (East-China Pharma) was described in this example. The above-described bioreactor (illustrated in
The above-described bioreactor (illustrated in
Water samples were obtained from the algae-bloomed Dianchi Lake, the sixth largest freshwater lake in China. The water samples were then subject to 30 minutes of ozone treatment using the above-described bioreactor. It was found that no taste, odor and color were observed after the treatment.
Ozone transfer speed into water was examined by using an ambient ozone transfer bioreactor (6 liter work volume; 0.25 meter in diameter wheels x2; 12 g/hour O3 generator). Table 12 shows the results.
Ozone transfer effect was examined by using an ambient ozone transfer bioreactor (6 liter work volume; 0.25 meter in diameter wheels x2; 12 g/hour O3generator) and ink colored water samples. Our result showed that O3transfer effect was clearly shown by de-colored water samples at various treatment periods.
In order to find the best materials for constructing the rotating wheels, different materials including metal, plastic, polymer, synthetic glass in different structural shapes were studied by scanning electronic microscope (SEM), dissolved oxygen probe, dissolved ozone probe, high-speed camera probe and a phase Doppler anemometer (PDA) probe for their oxygen and ozone transfer properties. Table 13 and Table 14 show their oxygen and ozone transfer results. The synthetic glass wheel coated with stainless steel metal nets at both sides was chosen for current use. For this study, wheels with 0.25 meter in diameter (90 rpm) were used in wastewater samples.
In order to understand if the rotating wheel (1.0 meter in diameter) oxygen transfer method and air-sparging interfered with each other or if they employ different mechanisms, different methods and combinations were employed. The results in Table 15 indicated that these two method used together as a combination did not perform better than the rotating wheel method alone, suggesting their interference on each others' performance. This also suggests different mechanisms of the two oxygen transfer methods.
Rotating wheels with different diameters (0.25, 0.5, 1.0, or 2.0 meter) were studied for their ozone transfer properties in periods of 10 minutes. Table 16 shows the results, indicating that all sizes of the diameters worked well. For all the experiments, a 12 g/L O3 generator was used. Thus, the ozone supply was not enough to supply O3 to the large wheel ozone transfer experiments due to the ozone generator's capability limitation.
The above-described O3 transfer technology was also applied to treat contaminated ground water. Detailed design was shown in
The present invention also relates to novel bioreactors to high-density culture of microorganisms and culture of activated sludge at both suspension and attached status. Within the scope of the invention are methods to high-density culture of microorganisms and stably culture of activated sludge at larger biomass by using a stacked wall of polymer paper carriers packed in between plastic nets and a novel oxygen transfer method, the method comprised using the just-described system for wastewater treatment.
In one example, it includes the use of dissolved oxygen making wheels to culture high-density E-coli in suspension compared with a conventional impellor-based deep tank bioreactor (
The systems and methods described herein can be used to high-density culture of microorganisms and the activated sludge at both suspension and attached status for treatment of wastewater. Based on the above methods, novel bioreactor systems (
A method for adaptation of activated sludge is described in this example. Wastewater COD 400-800 mg/L was used in a container supplied with air sparging at room temperature (18-24° C.). After one week of cultivation, the activated sludge appeared. Then, 50% of the wastewater was removed and the same volume of fresh wastewater volume added every week. In two weeks, qualified activated sludge was obtained. To maintain the activated sludge cultivation, 50% volume change every week continued.
A bioreactor with 60-gram of a stacked polymer paper per liter of wastewater was used to treat wastewater. The wastewater was cultivated for 6, 8, 10 and 12 hours. COD was measured. Results in Table 20 showed effective removal of COD was accomplished.
Attachment of the activated sludge to the polymer paper carriers was also studied in the cultivation containers. The sludge attachment status and clarity of supernatant were observed. Table 21 shows the results, indicating clear supernatant and almost complete attachment of the activated sludge while mixed either by air-sparging or the rotating wheels.
In order to understand attachment and growth of the activated sludge and related microorganisms in detail, scanning electronic microscope was used. Our results showed clear microorganism growth and attachment on and within the carriers.
We observed that micro-organisms grew within non-woven polymer fibers as well as on plastic and organic glass net (
A perfusion system using a 0.25 meter-diameter rotating wheel cultivation system was used for process development. The prototype system was shown in
After several runs, it was concluded that the loading richness of the wastewater such as COD levels automatically regulate biomass of the activated sludge. For example, higher COD loading of the wastewater resulted in higher biomass of the activated sludge attached to the paper carrier. The lower COD loading of the wastewater resulted in lower biomass of the activated sludge. This feature favors very much a stable perfusion cultivation system for wastewater treatment.
Very surprisingly, we used O3 treatment before aerobic fermentation unit, our results indicated that O3 treatment at 10 mg/L level reduced COD from 1001 to 650, and reduced ammonia nitrogen from 37 to 19 mg/L. These surprising results indicated that combined use of O3 unit and aerobic fermentation unit added one more choice for process development of wastewater treatment.
A perfusion system using a 1.0 meter-diameter rotating wheel cultivation system was designed for a 120-ton daily treatment facility. The complete system includes anaerobic fermentation, aerobic fermentation, O3 treatment and Pi removal. This system was used to study 120 tons/day wastewater treatment. COD removal 200-500 gram/ton/hour for each aerobic unit (2 ton work volume per unit) were expected. Table 23 shows the results of 4 hours of perfusion cultivation retention time at 25-30° C. plus two hour ozone treatment. A fish tank was again used to biologically monitor the outlet water quality. We concluded that a stable wastewater treatment system has been established.
Again, we found that total phosphate (TP) and total ammonia nitrogen (NH4-N) were significantly reduced when fishes were raised together with water plants. For example, TP was reduced from 1.2 to 0.4 mg/L while NH4-N was reduced from 16.0 to 4.6 mg/L. These results again indicated use of water plants together with fishes in the final clear water tank to reduce TP and NH4-N.
All of the features disclosed in this specification may be combined in any combination. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features. From the above description, one skilled in the art can easily ascertain the essential characteristics of the present invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, other embodiments are also within the scope of the following claims.
This application claims priority to U.S. provisional application No. 61/145,893, filed on Jan. 20, 2009; U.S. provisional application No. 61/168,740, filed on Apr. 13; 2009, U.S. provisional application No. 61/205,590, filed on Jan. 21, 2009; U.S. provisional application No. 61/212,387, filed on Apr. 11, 2009; and U.S. provisional application No. 61/258,322, filed on Nov. 5, 2009. The contents of these prior applications are herein incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US10/21522 | 1/20/2010 | WO | 00 | 9/30/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61145893 | Jan 2009 | US | |
| 61205590 | Jan 2009 | US | |
| 61212387 | Apr 2009 | US | |
| 61168740 | Apr 2009 | US | |
| 61258322 | Nov 2009 | US |
