Biological Wastewater Treatment System
20240132385 ยท 2024-04-25
Inventors
Cpc classification
International classification
Abstract
A biological wastewater treatment process utilizes biology carriers having recesses or pores defined on their surfaces. Biology form a biofilm or granular biofilm on the surface of the biology carriers and within. The pores or recesses protect the biology. As dissolved oxygen is consumed by biology close to the openings of the recesses or pores, less dissolved oxygen reaches biology living deeper within the pores. The pores thereby define aerobic, anoxic, and anaerobic regions within each biology carrier. Some examples of the biology carriers may be made at least in part from biochar or other partially charred materials. The resulting biological process requires less physical space than conventional flocculant sludge based processes and is more readily established and maintained verses traditional aerobic granular sludge.
Claims
1. A biological wastewater treatment method, comprising: providing at least one biological reactor; providing biology carriers within the at least one biological reactor; permitting biology to form on the biology carriers; providing wastewater into the at least one biological reactor; treating the wastewater anaerobically within at least one of the biological reactors, and treating the wastewater aerobically within at least one of the biological reactors, to produce biologically treated water; separating the biology carriers from a majority of the biologically treated water; and returning the biology carriers to one of the at least one biological reactors or retaining the biology carriers within the biological reactor.
2. The method according to claim 1, further comprising treating the wastewater anoxically within at least one of the biological reactors.
3. The method according to claim 2, wherein the anaerobic, aerobic, and anoxic treatment occur simultaneously for at least a portion of treating the wastewater anaerobically, aerobically, and anoxically within the biological reactor.
4. The method according to claim 3, wherein the biological carrier defines a plurality of recesses, the recesses containing biology, each of the recesses defining an outside portion, an inside portion, and a central portion therebetween, the outside portion supporting aerobic treatment by biology thereon, the central portion supporting anoxic treatment by bacteria thereon, and the inner portion supporting anaerobic treatment by bacteria thereon.
5. The method according to claim 4, wherein at least a portion of treating the wastewater anaerobically, aerobically, and anoxically within the biological reactor occurs simultaneously as a result of the outside portion, inside portion, and central portion defined by the recesses defined by the biological carrier.
6. The method according to claim 1, wherein the anaerobic and aerobic treatment occur simultaneously for at least a portion of treating the wastewater anaerobically and aerobically within the biological reactor.
7. The method according to claim 6, wherein the biological carrier defines a plurality of recesses, the recesses containing biology, each of the recesses defining an outside portion and an inside portion, the outside portion supporting aerobic treatment by biology thereon, and the inner portion supporting anaerobic treatment by bacteria thereon.
8. The method according to claim 7, wherein at least a portion of treating the wastewater anaerobically and aerobically within the biological reactor occurs simultaneously as a result of the outside portion and inside portion defined by the recesses defined by the biological carrier.
9. The method according to claim 1, wherein the biology carriers have a saturated specific gravity of about 0.8 to about 1.5.
10. The method according to claim 1, wherein the biology carriers are made at least partially from biological materials.
11. The method according to claim 10, wherein the biology carriers are made at least partially from biochar.
12. The method according to claim 1, wherein the biological reactor is a single tank wherein anaerobic, aerobic, and anoxic treatment are performed.
13. The method according to claim 12, wherein: the single tank includes bubble aerators, jet aerators, or venturi aerators, the bubble aerators, jet aerators, or venturi aerators being structured to provide a variable air flowrate; and anaerobic, aerobic, or anoxic processes are initiated by varying the air flowrate.
14. The method according to claim 1, wherein: the biology carriers have a specific gravity of about 1.0 to about 1.5; and separating the biology carriers from the biologically treated water is performed by permitting the biology carriers to settle, and then removing biologically treated water from above the settled biology carriers.
15. The method according to claim 1, wherein: the biology carriers have a specific gravity of about 0.8 to about 1.0; and separating the biology carriers from the biologically treated water is performed by permitting the biology carriers to float in an upper portion of the biological reactor, and then removing biologically treated water from below the biology carriers.
16. The method according to claim 1, further comprising combining the wastewater with volatile fatty acids prior to treating the wastewater anaerobically, aerobically, and anoxically within the biological reactor.
17. The method according to claim 1: wherein the biologically treated water has flocculant biology or biology which has become detached from carriers; and further comprising removing a portion of the flocculant biology or the biology which has become detached from the carriers from the biologically treated water.
18. The method according to claim 1: wherein the biologically treated water remaining with the biology carriers after separation of the biology carriers from a majority of the biologically treated water has flocculant biology or biology which has become detached from carriers; and further comprising removing a portion of the flocculant biology or the biology which has become detached from the biologically treated water remaining with the biology carriers prior to reintroducing the biology carriers to the reactor.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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[0019] Like reference characters denote like elements throughout the drawings.
DETAILED DESCRIPTION
[0020] Referring to the drawings, a biological wastewater treatment process is illustrated. Biological treatment will typically be performed as a secondary treatment process, after a primary filtering step, although the invention is not limited to this sequence of steps, and may include processes which solely utilize biological treatment. Some examples of biological treatment may also be followed by a tertiary treatment process which includes additional filtering. An example of a sequence of primary and secondary treatment processes is disclosed in US 2023/0002264, which was invented by the present inventors, published on Jan. 5, 2023, and is entitled Wastewater Treatment System for Improved Primary Treatment and Volatile Fatty Acid Generation, the entire disclosure of which is expressly incorporated herein by reference.
[0021] Referring to
[0022] The illustrated example of a granule 10 defines an exterior surface 12 and an interior surface 14. The interior surface may not be present if other source materials are used and may form a more spherical shape with the pores extending into the center of the material. Some examples of the granules 10 have a specific surface area between about 50 m.sup.2/g and about 900 m.sup.2/g, thus providing increased surface area for a biofilm to form on the surface of the granules 10. The exterior surface 12 includes multiple projections 16 defining recesses 18 therebetween. Recesses or pores having a width W greater than about 0.5 ?m facilitate biology inhabiting the recesses or pores. When the granules 10 are placed in a biological treatment reactor, biology adhere to the surfaces 12, 14, including within the recesses 18. The recesses 18 serve to protect biology therein, and for the example of a rice hull, the interior surface 14 may also provide a protected area for biology as well. The recesses 18 also help to define aerobic, anoxic, and anaerobic regions on each granule 10. It is anticipated that biology on surface 12 located near an outside portion 20 of a recess 18, or otherwise on the surface 12 outside of a recess 18, will have the greatest access to dissolved oxygen for engaging in aerobic respiration. Less dissolved oxygen is anticipated to reach a central portion 22 of the recesses 18, because at least some of the oxygen is consumed by biology on the outside 20 of the recesses 18. Biology in the central portion 22 of each recess 18 are therefore likely to engage in anoxic respiration within at least some biological reactors. Similarly, biology within an inner portion 24 of each recess 18 is likely to receive even less dissolved oxygen, since biology in each outer region 20 and central region 22 are anticipated to consume a large portion of the available oxygen. Biology in the inner region 24 of each recess are therefore likely to be anaerobic within at least some biological reactors.
[0023] Other examples of the granules 10 may be made from sponge or other inorganic absorption media. Still other examples of the granules 10 may include recycled plastic material or charred plastics to increase porousness for the biology to reside on and within.
[0024] The granules 10 may be treated either before use, or after predetermined time periods, predetermined number of treatment cycles, or predetermined volume of water treated so that the hydrophilicity, absorptive capacity, or ion exchange capacity is increased. This treatment may occur in situ or ex situ.
[0025] The hydrophobicity of the biochar as well as the oleophilicity (useful if using the biochar to carry biology or for acting as an absorptive media) can be increased with various surface treatments. For example, oils such as linseed oil, which is a known polymerizing oil, or tung oil may be used to treat the porous structure of the biochar granules 10. This type of treatment preserves all of the advantages of using biochar as biofilm carriers, while rendering the material substantially hydrophobic.
[0026] In other examples of biology carriers, the granules 10 are combined with a polymer or other low density binder in a manner which occludes a portion of the recesses within the granules 10, thus resisting the ingress of water and increasing the buoyancy of the granules. The low density of the polymer or other binder also increases buoyancy. Some examples of the resulting carriers will have a buoyancy of about 1.5 (negatively buoyant or sinking) to about 0.8 (positively buoyant or floating) when saturated with water. Other examples of the carriers will have a buoyancy of about 0.95 to about 1.05 when saturated with water. Still other examples of the carriers will have a buoyancy of about 1.0 (neutral) when saturated with water. At least a portion of the recesses in the granules remain so that the recesses defined within the granules remain available for inhabitation by biology. Some examples of the binders may also have adhesive properties, causing the granules 10 to cluster together to form larger biology carriers 26, as illustrated in
[0027] Referring to
[0028] The polymer base 28 may be made from a variety of polymers, with examples including polypropylene, low density polyethylene, and high density polyethylene among other various thermoplastics or other polymers. The granules may be added by melting or partially melting the polymer base 28, and then adding the granules 10 to the surface so that at the base cools, it solidifies around portions of the granules to secure them in place. Alternatively, the granules can be heated and then added to the surface of the polymer base 28. As another example, the granules 10 can be added to the polymer prior to extruding the polymer, such that the granules form occlusions which are not able to be saturated with water, increasing the buoyance of the compound. In this scenario the outer layer of polymer can charred or melted away to expose at least a portion of the outer granules' surface. Uncharred porous organic materials or inorganic porous materials may also be incorporated into the composite formed or serve as an alternative to biochar. If so desired, other materials of higher density can be added to the composite to decrease buoyancy and promote faster settling within the process or to add desirable properties, for example increased cationic exchange capacity. The media can also undergo various treatments to enhance hydrophobicity, hydrophilicity, oleophilicity, oleophobicity, or various other adsorptive properties such as cationic exchange capacity to enhance contaminant adsorption.
[0029] Granules 10, clusters 26, and bases 28 having granules 10 thereon are herein collectively referred to as biology carriers 32. Biology carriers 32 can be utilized within processes that utilize separate reactors for anaerobic, aerobic, and/or anoxic processes, as well as within processes that utilize a single reactor to perform anaerobic, aerobic, and/or anoxic processes. If a single reactor is used, anaerobic, aerobic, and anoxic processes may be performed sequentially within that reactor, or may be performed simultaneously within that reactor by taking advantage of the structure of the granules 10 to create aerobic, anoxic, and anaerobic zones.
[0030] Referring to
[0031] Some examples of the treatment process include utilizing an ultraviolet or electrocoagulation device prior to biological treatment of the wastewater in order to make the contaminants within the wastewater more easily removed. In some examples of the treatment process, metal coagulants, salts, acids, bases, or oxidants are also added to the wastewater either prior to or during biological treatment in order to enhance the removal of contaminants. All of these processes and additives are well known to those skilled in the art of water treatment.
[0032] Once primary treatment is complete, the wastewater (and in some examples the volatile fatty acids combined with the wastewater) is added to a reactor 38 at step 40, in the illustrated example utilizing pump 42. Other examples may utilize gravity feed. An example of a reactor 38 is illustrated in
[0033] Anaerobic, aerobic, and anoxic processes can be performed sequentially. Although not limited to this order, an example biological process begins by injecting large air bubbles and/or providing air at a lower flowrate into the reactor 38 to provide agitation during anaerobic processing at step 40 (
[0034] Alternatively, referring to
[0035] Referring to
[0036] A pair of substantially identical filter discs 96 are rotatably secured within the housing 84, and connected by a central shaft to a motor. The filter discs 96 may be flat or conical in nature. A treatment chamber 98 is defined between the discs, as well as by a bottom wall 100 which is in sliding contact with the rotating discs 98. In the illustrated example, each of the filter discs 96 includes an inner course filter screen of approximately 50-1,000 ?m adjacent to the treatment chamber 98, and an outer fine filter screen having an approximately 10-50 ?m screen, Alternatively the course filter can be in the outer position to provide support for the fine filter screen or can be accomplished with a single fine screen layer of between approximate 10-1,000 ?m. A lip seal along the perimeter of each of the discs 98 resist passage of water between the edge of the disc 98 and the wall 100. An effluent chamber 102 is located below the wall 100. A discharge conduit 105 carries filtered water out of the effluent chamber 102.
[0037] A pipe 104 is disposed outside of each of the filter discs 96. The pipes 104 include a plurality of nozzles 106 for directing pressurized water against the outside of each of the discs 96. A collecting duct 108 is disposed between the filter discs 96, below the pipe 104.
[0038] Water and biology carriers within the influent chamber 86 will enter the treatment chamber 98 between the rotating discs 96. The water will pass through the filter discs 96 into the effluent chamber 102. Biology carriers 32 are unable to pass through the discs 96, and are removed via the chute 103 via the combined rotation of the disks and velocity of the water entering between the disks. Pressurized water from the nozzles 106 pushes the flocculant sludge trapped on the filter discs 96 back into the treatment chamber 98, where they fall into the collecting duct 108. The biology carriers 32, and inevitably some water, are then transferred back to the anaerobic reactor 38 by the pump 110, gravity, or other means of conveyance and the flocculant sludge is wasted from the process to remove nutrients assimilated within. In the illustrated example, filtered water exiting the outlet 105 is carried by the pump 112 or by gravity to a tertiary filtering treatment 114 at step 116, 117 and then discharged at step 118, 119. Other examples may directly discharge the water from the outlet 105.
[0039] Other examples of the water treatment system may utilize sedimentation, floatation, or hydraulic separation. Some methods of removing the carriers 10 and flocculant sludge from the treated water may leave the carriers 10 within the reactor 38, rather than removing and then returning the carriers 10. For example, depending on the specific gravity of the carriers 10, they may be permitted to sink to the bottom of the reactor 38 so that water may be removed from the top of the reactor 38. Alternatively, carriers 10 may be permitted to float to the top of the reactor 38 so that water can be withdrawn from a portion of the reactor below the carriers. Unattached biology as well as any organic or inorganic particles are anticipated to sink to the bottom of the reactor 38. Depending on whether removal of this unattached biology and these particles is desirable, water may be removed from the middle of the tank to remove water only, or from the bottom of the tank to remove unattached biology and particles. In examples wherein the flow of water into and out of the reactor 38 is intermittent, stopping mixing at a time when water is not flowing in or out will permit the carriers 10, unattached biology, and other particles within the reactor 38 to float or sink.
[0040] As the processes of
[0041] The processes described herein can be performed as batch processes, wherein a predetermined volume of water is placed in the reactor 38 and then remains in the reactor until fully biologically treated and proceeds to filtering. Alternatively, the processes may be performed continuously, with wastewater continuously entering and exiting the reactor 38, and biology carriers 32 being continuously separated by filtration and returned to the reactor 38. In yet another form, the biology carriers 32 are retained via hydraulic separation, where the rapidly settling biology carriers 32 are retained and slower settling flocculant sludge is wasted from the process. In another form, the biologically treated water is separated from the biology carriers 32 and flocculant sludge via gravity settling and then the flocculant sludge is separated from the biology carriers 32 via filtration as described earlier, with the flocculant sludge being wasted and the biology carriers 32 returned to the anaerobic process stage.
[0042] The present invention therefore provides a means of biologically treating wastewater using simultaneous aerobic, anaerobic, and anoxic processes. Aerobic, anoxic, and anaerobic zones are created on each biology carrier, and are determined by the depth of the biology within the pores or recesses of the biology carrier. The process can be accomplished with reduced physical space, reduced energy, and more quickly as compared to prior biological treatment processes. The specific gravity and particle density of the biology carriers facilitates keeping the biology carriers suspended in and distributed around the wastewater, while also facilitating settling of the biology carriers when desired. The biological treatment process reduces the quantity of organic carbon, nitrogen, and phosphorus and the biology carriers along with the biological degradation may also aid in the adsorption of contaminants of emerging concern such as perfluorinated compounds, 1,2,3-trichloropropane, 1,4-dioxane, 2,4,6-trinitrotoluene, dinitrotoluene, hexahydro-1,3-5-trinitro-1,3,5-triazine, N-nitroso-dimethylamine, perchlorate oxidants, and other contaminants within the wastewater via adsorption. The treatment process utilizes biology carriers made at least in part from charred biological waste, making the biology carriers resist biological degradation, robust, and to be readily habitable verses traditional aerobic granules which often takes many months to be generated by the biology or sometimes fail to form at all. Partially charred wastes may also potentially be added to provide a supplemental carbon source for the biology that lives thereon if the system is carbon limited, thereby ensuring the availability of this biology for the treatment process. The possible addition of volatile fatty acids further ensures that the biology has an adequate source of carbon to drive the biological process regardless of whether the biology exists in the aerobic, anoxic, or anaerobic zone of a biology carrier.
[0043] A variety of modifications to the above-described embodiments will be apparent to those skilled in the art from this disclosure. Thus, the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention. The appended claims, rather than to the foregoing specification, should be referenced to indicate the scope of the invention.