WO2016077715A1

WO2016077715A1 - Biological water treatment for waste management

Info

Publication number: WO2016077715A1
Application number: PCT/US2015/060615
Authority: WO
Inventors: Jerold ZWAS
Original assignee: Plava Pur, Llc
Priority date: 2014-11-14
Filing date: 2015-11-13
Publication date: 2016-05-19

Abstract

An attached growth bioreactor for wastewater treatment is disclosed. One or more cages containing high surface area growth media for maintaining biological agents can be housed in one or more chambers through which wastewater flows. As the wastewater flows through the chambers it passes through the cages thereby interacting with the biological agents maintained on the growth media. As the cages rotate, the growth media in each cage is exposed to the air and oxygenated, allowing for aerobic microbial growth. Then, as the cages continue rotating, the growth media is submerged in the wastewater to treat the wastewater. The disclosed implementations can be relatively simple to operate and maintain, and may be practiced in small volumes and in compact spaces.

Description

BIOLOGICAL WATER TREATMENT FOR WASTE MANAGEMENT

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Patent Application Serial No.

14/541,346 filed November 14, 2014, the contents of which are incorporated herein by reference.

BACKGROUND

[0002] This disclosure relates generally to wastewater treatment systems, and specifically to attached growth bioreactors. Animal farming produces substantial waste material in the form of animal feces which can be saturated with harmful nitrogen compounds. If wastewater containing these contaminants is released into lakes, rivers, or other bodies of water, it can promote unwanted growth of algae and other aquatic plants that consume oxygen. Consequently, it is often advantageous to treat the wastewater to reduce nitrogen and phosphorous compounds in the wastewater prior to discharge of the wastewater.

[0003] Treatment of wastewater can be accomplished through the exposure of the wastewater to various biological agents including certain kinds of bacteria. There are several types of wastewater treatment facilities. In an "unattached" system, the biological agents may be introduced to the wastewater directly. In an "attached" system, the biological agents may be cultivated and grown on the surface of various media submerged in the wastewater, such as large, rotating discs called rotating biological contactors.

[0004] Different biological agents require different environmental conditions to survive. For example, some biological agents require aerobic conditions to survive. This requires exposure to oxygen. Other biological agents require anaerobic or anoxic conditions, which do not require exposure to oxygen. Current methods and systems for wastewater treatment often include multiple vessels in order to cultivate a plurality of environments for multiple types of biological agents. For example, in one unit, wastewater may be subjected to aerobic conditions to oxidize the nitrogen compounds to nitrates. In another unit, wastewater may be subjected to anoxic conditions to denitrify the nitrified wastewater. [0005] These multi-stage systems are complex to operate and expensive to maintain because of the resources needed to power the pump systems that move wastewater through the systems, from one tank to another tank or to pump air into the wastewater to provide the necessary oxygen levels. These systems and their parts are prone to breaking down or wearing out, and repair or replacement can be costly and time consuming. In addition, due to the complexity and cost of the systems, these systems are generally economically feasible only when installed in large water treatment facilities.

SUMMARY

[0006] Disclosed herein are implementations for an attached growth bioreactor for wastewater treatment. One or more cages containing high surface area growth media for maintaining biological agents can be housed in one or more chambers through which wastewater flows. As the wastewater flows through the chambers it passes through the cages thereby interacting with the biological agents maintained on the growth media. As the cages rotate, the growth media in each cage is exposed to the air and oxygenated, allowing for aerobic microbial growth. Then, as the cages continue rotating, the growth media is submerged in the wastewater to treat the wastewater. The disclosed implementations can be relatively simple to operate and maintain, and may be practiced in small volumes and in compact spaces.

[0007] In one exemplary implementation, a bioreactor for treating wastewater using biological agents is disclosed, the bioreactor comprising: at least a first chamber and a second chamber, each chamber comprising: an inlet for the wastewater to enter the chamber; an outlet for the wastewater to leave the chamber; a shaft; and a plurality of cages disposed on the shaft, each cage comprising a plurality of sections for holding growth media for the biological agents; wherein the outlet of the first chamber is in fluid communication with the inlet of the second chamber.

[0008] In another exemplary implementation, a method for treating wastewater using biological agents is disclosed, comprising: channeling the wastewater through a first chamber and a second chamber, each chamber comprising: an inlet for the wastewater to enter the chamber; an outlet for the wastewater to leave the chamber; a shaft; and a plurality of cages disposed on the shaft, each cage comprising a plurality of sections for holding growth media for the biological agents; wherein the outlet of the first chamber is in fluid communication with the inlet of the second chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 A is a cut away representation of an example attached growth bioreactor.

[0010] Fig. IB is a pictorial representation of a housing usable with the attached growth bioreactor.

[0011] Fig. 2 is an exploded representation of a cage used in the attached growth bioreactor.

[0012] Fig. 3 is a perspective pictorial representation of a cage used in the attached growth bioreactor.

[0013] Fig. 4 is a front view of the attached growth bioreactor.

[0014] Fig. 5 is a side view of the attached growth bioreactor.

[0015] Fig. 6 is a top view of the attached growth bioreactor.

[0016] Fig. 7 is a pictorial representation of another example attached growth bioreactor.

DETAILED DESCRIPTION

[0017] An attached growth bioreactor for wastewater treatment is disclosed. One or more cages containing high surface area growth media for maintaining biological agents can be housed in one or more chambers through which wastewater is channeled. As the wastewater flows through the chambers it can be channeled through the cages, thereby causing the wastewater to contact the biological agents maintained on the growth media. The cages can be partially submerged in the wastewater and partially exposed to the air. As the cages rotate, the growth media in the cages is exposed to the air and oxygenated, allowing for aerobic microbial growth. Then, as the cages continue rotating, the growth media is submerged in the wastewater to treat the wastewater. Each cage can be partitioned into sections, each section containing growth media. Two or more chambers can be arranged in a serpentine fashion such that the direction of the wastewater flow alternates for each chamber. The flow of the wastewater can be gravity fed.

[0018] Fig. 1 A is a partially exploded pictorial representation of an attached growth bioreactor 100. The bioreactor 100 can include one or more chambers 102 through which wastewater can be channeled. In one exemplary implementation, the chambers 102 can be arranged side by side, with the wastewater flow direction alternating between each successive chamber 102. This arrangement can allow the bioreactor 100 to be encased in a compact unit to allow for easy transportation, rather than one long chamber, which would be more difficult to transport. In addition, it can generally be more difficult to maintain the structural integrity of a long chamber or shaft and to prevent bowing. On the other hand, the exemplary implementations disclosed here can enhance the structural integrity and portability of an attached growth bioreactor.

[0019] In this disclosure, the term "chamber" refers to a row, or train, of cages 110

(described in more detail below), which can guide the path of the wastewater through the bioreactor 100. In one exemplary implementation, the bioreactor 100 can include one or more frames 103, and a single frame 103 can encompass multiple chambers 102. In another exemplary implementation (not depicted in the figures), each chamber 102 can include a separate frame 103.

[0020] Fig. IB is a pictorial representation of a housing 104 usable with the attached growth bioreactor 100. The housing 104 can include exterior walls to surround the frames 103. The housing can include one or more dividers 105 separating the chambers 102 within the housing 104. The housing 104 can also include interior walls 106 separating the cages 110 within each chamber 102. The interior walls 106 can include concave sides to match the curvature of the cages 110 to prevent the wastewater from flowing around the cages 110, as described below.

[0021] Each chamber 102 can include a face defining an inlet 107 and a face defining an outlet 108. For each chamber 102, the outlet 108 can be situated lower than the inlet 107. This can allow gravity to cause the wastewater to flow through the chamber 102 and drain toward the outlet 108. The outlet 108 of a first chamber 102 can be connected to a channel 109 which in turn feeds into the inlet 107 of a second chamber 102. The channel 109 can be positioned on an incline such that the inlet 107 of the second chamber 102 is lower than the outlet 108 of the first chamber 102 so that gravity can be used to channel the wastewater to the inlet 107 of the second chamber 102. This can be repeated for each subsequent chamber 102.

[0022] It should be noted that other arrangements for the positioning of the chambers

102 can be employed to conform to space constraints present in a particular environment without departing from the spirit and scope of the invention. For example, the chambers 102 can be positioned in a "T" arrangement. Additionally, the chambers 102 can be stacked on two or more vertical levels (for example, in a 2x2 arrangement). An arbitrary number of chambers 102 may be employed, with the wastewater moving through the chambers 102 serially. In each case, a channel 109 can connect the outlet 108 of one chamber 102 to the inlet 107 of the next chamber 102 in the series. In accordance with one exemplary implementation, the chambers 102 can be used modularly, so that if more treatment capability is required, an additional chamber 102 or group of chambers 102 can be easily added to the bioreactor 100. Similarly, two or more complete bioreactor 100 units can be used together to create a larger effective treatment system. Multiple bioreactors 100 can be used either in serially or in parallel. In the interest of simplicity, the disclosed figures have been illustrated using two chambers 102 in a single bioreactor 100.

[0023] Fig. 2 is an exploded representation of a cage 110 used in the bioreactor 100, and Fig. 3 is a perspective view of the cage 110. Each chamber 102 can include a one or more cages 110 which can contain media for growing useful biological agents. The cages 110 can be disposed axially on a shaft 112 (as described below in Figs. 5 and 6). In one exemplary implementation, circular cages 110 can be used. Each cage 110 can include partitions 114 to segment the cage 110 into a plurality of sections 116 (for example, eight equally sized sections 116, as depicted in Fig. 2). A screen 118 can be included on each side of the cage

110 to contain the growth media. The screen 118 can be fine enough to keep the growth media from falling out but will allow the wastewater to pass through. Structure rings 120 can be used to help maintain the structure of the cage 110 and to lock the screens 118 onto the cage 110. Partition covers 122 can be used as the perimeter of each cage 110 and to secure the growth media within the sections 116. [0024] The width of the partitions 114 will generally dictate the overall width of the cage 110, with some additional width provided by the two screens 118. As an example, the partitions 114 may be approximately 4" wide. The diameter of each cage 110 can measure, for example, approximately 5'. As described above, the dimensions and shape of the chambers 102 and the housing can fit tightly around the cages 110 to ensure that all wastewater is forced to flow through the cages 110 and thereby contact the media. For example, each of the interior walls 106 can have a concave edge that matches the curvature of a corresponding cage 110 and that abuts that cage 110. Accordingly, the wastewater can be prevented from bypassing the cages 110, and can be forced to flow through the cages 110 rather than around them. The cages 110 can be partially submerged in the wastewater and partially exposed to the air. In one exemplary implementation, approximately half of each cage 110 (the bottom portion) can be submerged.

[0025] The growth media can be housed in each of the sections 116 of the cages 110.

The growth media can include any media that can sustain and support the growth of biological agents useful for wastewater treatment. Different types of growth media and/or different types of biological agents can be used for treating different kinds of wastewater. In one example implementation, a growth media with high surface area can be used. The high surface area allows more of the biological agent to live on the media. One type of growth media that can be used is zeolite. Zeolites are generally microporous minerals, either naturally occurring or manufactured synthetically. Other high-surface area materials can also be used without departing from the spirit or scope of the invention. One or both of the screens 118 on each cage 110 can be removable to enable a user to fill or replace the growth media. Alternatively, the partition covers 122 can be removable to enable the user to fill or replace the growth media within a section 116. In another exemplary implementation, the cages 110 can be permanently sealed and disposable at the end of the life of the growth media and/or the biological agents. After disposing one cage 110, a new cage 110 containing new growth media can be installed in its place within the chamber 102.

[0026] One advantage of the disclosed implementations is that the entire volume of each cage 110 can be filled with growth media, which can result in a substantial increase of total surface area on which the biological agents can be supported. On the other hand, existing rotating biological contactors can only support biological agents on their surfaces (that is, in two dimensions). The sections 116 need not be packed tightly with growth media, and in fact loosely filled sections 116 (for example, 80-90% filled) can allow the growth media to mix evenly as the cage 110 rotates, allowing the particles to come into contact with a greater portion of the wastewater and air.

[0027] Keeping the growth media in partitioned sections 116 within the cages 110 can lead to a number of heretofore unexpected benefits. For example, because each section 116 is separated by the partitions 114, the sections 116 do not all have to be filled to the same capacity. For instance, if there is only a small amount of wastewater to be treated, some sections 116 of the cage can be left empty. Similarly, one or more cages 110 within a chamber 102 can be left empty and the wastewater will simply flow through the empty cage 110.

[0028] Additionally, keeping the growth media in partitioned sections 116 can prevent the growth media from settling to the bottom of the cage 110. This can ensure that the biological agents are sequentially exposed to the air and the wastewater, thus promoting the aerobic reactions of the biological agents. The sections 116 also prevent clumping of the growth media, which can deprive biological agents trapped within the clumps of exposure to air and/or the wastewater. Also, it is believed that the force of the partitions 114 contacting the wastewater as the cages 110 rotate may lead to a heretofore unexpected benefit of agitating the wastewater and creating micro-vortices at the point of contact with the wastewater, infusing the wastewater with additional oxygenation, which can increase the efficacy of the biological agents.

[0029] In addition to being treated by the biological agents, as the wastewater flows through each chamber 102, it will naturally be filtered by the screens 118 and by the media itself. Nevertheless, it may be desirable to filter out the largest solids before biological treatment. Accordingly, the wastewater can be run through a pre-processing separator or centrifuge prior to releasing it into the chambers 102, and/or a coarse filter can be incorporated into the inlet 107 of a chamber 102 in order to separate the larger solids from the wastewater liquids before the wastewater enters the chamber 102.

[0030] In addition, as the wastewater flows through the chambers 102, heavier solids can separate and settle to the floor of a chamber 102, allowing for easy disposal. Similarly, dead biological agents can detach from the growth media and settle together, creating a sludge that can settle to the floor of the chamber 102. The sludge can thus be easily removed for disposal or for other industrial uses (such as fertilizer, etc.).

[0031] Figs. 4, 5, and 6 are front, side, and top views, respectively, of an example attached growth bioreactor 100. Each chamber 102 in the attached growth bioreactor 100 can include a shaft 112 that can extend approximately the length of the chamber 102, from substantially the inlet face to substantially the outlet face of the chamber 102. The shaft 112 can be supported on the chamber 102 using bearings 124. A plurality of cages 110 can be disposed axially on the shaft 112.

[0032] The shaft 112 can be configured to rotate axially, driven by a motor 130 in mechanical communication with the shaft 112. The mechanical communication can be made using a chain 132, or through any other similar methods (for example, using one or more belts, gears or similar mechanical devices) familiar in the art. A sprocket 134 can be used to connect the shaft 112 to the chain 132.

[0033] In one exemplary implementation, as shown in Fig. 6, a single motor 130 can power two or more shafts 112. The cages 110 in each chamber can be affixed to the shaft 112 so that the cages 110 rotate in concert with the shaft 112. Using multiple gears as part of the mechanical communication between the motor 130 and each particular shaft 112, any arbitrary gear ratio can be achieved. Accordingly, each shaft 112 can individually be selectively configured to rotate at a different speed. The rotational speed can control the amount of oxygen supplied to the wastewater by controlling the amount of time the wastewater is exposed to the air, in order to achieve a desired biological oxidation of carbonaceous organics in the wastewater.

[0034] In another exemplary implementation, each cage 110 can be selectively configured in an attached state or detached state. In the attached state, the cage 110 is affixed to the shaft 112; thus, it will rotate in concert with the rotation of the shaft 112. In the detached state, on the other hand, the cage 110 can be detached from the shaft 112 so that it hangs freely, remaining stationary even as the shaft 112 rotates. This can be advantageous because some treatment processes require anaerobic conditions, meaning they use biological agents that are not exposed to oxygen for microbial growth. Accordingly, the sections 116 of a detached cage 110 that are below the wastewater level can be filled with anaerobic biological agents. These sections 116 will remain underwater, even when the shaft 112 is rotating. On the other hand, other cages 110 that are in an attached state can contain aerobic biological agents and can rotate to supply those agents with the necessary air exposure.

Accordingly, the same chambers 102 can be used for both aerobic and anaerobic treatment processes, thus increasing the flexibility of the system compared to the prior art (which generally use completely different and separate chambers for aerobic and anaerobic stages of wastewater treatment).

[0035] Fig. 7 is a pictorial representation of an alternative exemplary implementation of the bioreactor 100, in which the cages 110 can be in mechanical communication with the motor 130 via an axle 136, for example using chains 132. In this implementation, a fixed (non-rotating) shaft 112 can be used rather than a rotating one, and the cages 110 are not attached to the shaft 112, but rather rotate axially around it. In this implementation, each cage 110 individually can be selectively configured to rotate at a different speed based on a selected gear ratio used to connect each cage 110 with the axle 136.

[0036] The bioreactor 100, comprising all the chambers 102 collectively, can be contained in one compact housing. The wastewater can be introduced into the bioreactor 100 via the inlet 107 in the first chamber 102 of the series and be released through the outlet 108 of the final chamber 102 in the series. As described above, the wastewater can pass from the outlet 108 of one chamber 102 to the inlet 107 of the next chamber 102 via a channel 109. The bioreactor 100 can include wheels (for example, either two rear wheels or four or more wheels) and can be configured as a trailer so that it can be hitched to a vehicle for easy transport. In another exemplary implementation, it can be configured to be transported on a flatbed. In one exemplary implementation, the size of the bioreactor 100 can be such that the bioreactor fits in a standard-size shipping or trucking container (for example, a standard 20- foot container or a standard 40-foot container). The number of chambers 102 in the bioreactor 100 can also be set according to the desired size of the external housing of the bioreactor 100.

[0037] The foregoing description relates to what are presently considered to be the most practical embodiments. It is to be understood that the above-described embodiments are merely illustrative of the application. Other embodiments, modifications, and equivalent arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof. The scope of the claims is thus to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures as permitted by law.

Claims

What is claimed is:

1. A bioreactor for treating wastewater using biological agents, the bioreactor comprising: at least a first chamber and a second chamber, each chamber including: a first face, the first face defining an inlet for the wastewater to enter the associated chamber; a second face opposite the first face, the second face defining an outlet for the wastewater to exit the associated chamber, wherein the inlet and the outlet are positioned relative to one another to define a course of wastewater fluid flow; at least one shaft extending substantially from the first face to the second face; and at least one cage axially disposed on the at least one shaft, the at least one cage having a plurality of sections, wherein each section is permeable to the wastewater and configured to hold growth media that supports growth of the biological agents, wherein at least one cage is positioned relative to the course of wastewater fluid flow; wherein the outlet of the first chamber is in fluid communication with the inlet of the second chamber.

2. The bioreactor of claim 1, wherein the outlet of each chamber is vertically offset from the inlet of that chamber at a lower position for the purpose of using gravity to channel the wastewater from the inlet to the outlet.

3. The bioreactor of claim 1, wherein the inlet of the second chamber is vertically offset from the outlet of the first chamber at a lower position for the purpose of using gravity to channel the wastewater from the outlet of the first chamber to the inlet of the second chamber.

4. The bioreactor of claim 1, wherein the wastewater is channeled through the first chamber and the second chamber in mutually distinct directions.

5. The bioreactor of claim 1, wherein the at least one cage of the at least first chamber and second chamber is rotationally mounted relative to the respective chamber on an axis substantially coterminous with the at least one shaft of the respective chamber.

6. The bioreactor of claim 5, wherein rotational movement of the at least one cage is powered by a motor.

7. The bioreactor of claim 5, wherein rotational movement of the at least one cage is at a speed determined by a selected gear ratio.

8. The bioreactor of claim 5, wherein the at least one shaft of the at least first chamber and second chamber is rotationally mounted relative to the respective chamber, and wherein rotational movement of the at least one cage is induced by rotational movement of the at least one shaft.

9. The bioreactor of claim 8, wherein rotational movement of the at least one cage can be selectively prevented by disconnecting the at least one cage from the at least one shaft.

10. The bioreactor of claim 5, wherein the at least one shaft is non-rotating and the at least one cage is rotationally mounted relative to the at least one shaft.

11. The bioreactor of claim 5, wherein the at least one cage is partially submerged in the wastewater and partially exposed to air, and wherein axial rotation of the at least one cage causes the growth media contained in the plurality of sections of the at least one cage to sequentially contact the wastewater and the air.

12. The bioreactor of claim 1, further comprising a single external housing containing the at least first chamber and second chamber.

13. The bioreactor of claim 12, wherein the single external housing comprises at least two wheels and is configured to be connected in a trailer configuration to a hitch of a vehicle.

14. The bioreactor of claim 1, wherein the growth media is zeolite.

15. A method for treating wastewater using biological agents, comprising: channeling the wastewater through a first chamber and a second chamber, each chamber comprising: a first face, the first face defining an inlet for the wastewater to enter the associated chamber; a second face opposite the first face defining an outlet for the wastewater to exit the associated chamber; at least one shaft extending substantially from the first face to the second face, wherein the inlet and the outlet are positioned relative to one another to define a course of waste water flow; and at least one cage axially disposed on the at least one shaft, the at least one cage having a plurality of sections, wherein each section from the plurality of sections is permeable to the wastewater and configured to hold growth media that supports growth of the biological agents, wherein said at least one cage is positioned relative to the course of wastewater flow; wherein the outlet of the first chamber is in fluid communication with the inlet of the second chamber.

16. The method of claim 15, further comprising: channeling the wastewater, within each of the at least first chamber and second chamber, through the at least one cage so as to cause the wastewater to contact the growth media in the plurality of sections.

17. The method of claim 15, further comprising: axially rotating the at least one cage of the at least first chamber and second chamber relative to the respective chamber on an axis substantially coterminous with the at least one shaft of the respective chamber.

18. The method of claim 17, wherein the at least one cage is partially submerged in the wastewater and partially exposed to air, and wherein axially rotating the at least one cage causes the growth media contained in the plurality of sections of the at least one cage to sequentially contact the wastewater and the air.

19. The method of claim 15, wherein the wastewater is channeled through the first chamber and the second chamber in mutually distinct directions.

20. The method of claim 15, wherein the growth media is zeolite.