WO2020041198A1

WO2020041198A1 - Methods for air flotation removal of highly fouling compounds from biodigester or animal waste

Info

Publication number: WO2020041198A1
Application number: PCT/US2019/047069
Authority: WO
Inventors: Ian Andrew HARRISON; John R. Herron; Jason Allan LAMPI
Original assignee: Fluid Technology Solutions (fts) Inc
Current assignee: Fluid Technology Solutions (fts) Inc
Priority date: 2018-08-24
Filing date: 2019-08-19
Publication date: 2020-02-27
Anticipated expiration: 2021-02-24

Abstract

Embodiments disclosed herein are directed to methods and systems for treating wastewater without addition of chemical flocculants. By way of example, the methods and systems disclosed herein may be used to remove one or more macromolecules, such as lignin, from the wastewater. For example, one or more macromolecules may be removed from the wastewater by injecting sub-micron sized air bubbles into the wastewater, effective to attach at least a portion of the sub-micron sized air bubbles to macromolecules in the wastewater to form macromolecule-coated bubbles that agglomerate and rise in the wastewater. The macromolecule-coated bubbles form a foam of the macromolecule-coated bubbles that is separated from the wastewater.

Description

METHODS FOR AIR FLOTATION REMOVAL OF HIGHLY FOULING COMPOUNDS FROM BIODIGESTER OR ANIMAL WASTE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application 62/722,357 filed on 24 August 2018, the disclosure of which is incorporated herein, in its entirety, by this reference.

BACKGROUND

[0002] Capture of fertilizer value from waste from dairies, biodigesters, and animal lots has become a priority. In the past, such wastewaters have been land applied to fields surrounding the site. This practice is being curtailed for environmental reasons due to the over-application of ammonia and phosphates to the fields. Volumes of waste from these installations are large and the nutrient fraction is relatively low, so trucking the waste more than a few kilometers is also not economical.

SUMMARY

[0003] Embodiments disclosed herein are directed to methods for separating macromolecules from wastewater by injecting sub-micron diameter bubbles into the wastewater. Wastewater from biodigesters is difficult to treat with membrane concentration systems largely due to the high concentrations of macromolecules in the wastewater, such as lignin, which do not breakdown during anaerobic digestion. Wastewater with these macromolecules shows thixotropic properties and gelation during concentration, which easily causes membrane or heat transfer surface fouling.

[0004] In an embodiment, a method of treating wastewater without addition of chemical flocculants is disclosed. The method includes providing the wastewater in a first chamber. The method also includes injecting sub-micron sized air bubbles into the wastewater in the first chamber, effective to attach at least a portion of the sub-micron sized air bubbles to macromolecules in the wastewater to form macromolecule-coated bubbles that agglomerate and rise in the wastewater. The macromolecule-coated bubbles form a foam of the macromolecule-coated bubbles. The method also includes removing at least a portion of the foam of the macromolecule-coated bubbles from the first chamber.

[0005] In an embodiment, a system for treating wastewater without addition of chemical flocculants is disclosed. The system includes a first chamber configured to receive wastewater therein, the first chamber including a collection hole. The system also includes an air injector configured to inject sub-micron sized air bubbles into the wastewater in the first chamber. The sub-micron sized air bubbles attach to macromolecules in the wastewater to form macromolecule-coated bubbles that agglomerate and rise in the wastewater to form a foam of the macromolecule-coated bubbles for at least partial removal from the first chamber through the collection hole.

[0006] Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The drawings illustrate several embodiments of the present disclosure, wherein identical reference numerals refer to identical elements or features in different views or embodiments shown in the drawings.

[0008] FIGS. 1A-C are schematic block diagrams of a wastewater treatment system for treating wastewater, according to an embodiment;

[0009] FIGS. 2A-C are schematic block diagrams of a wastewater treatment system for treating wastewater, according to an embodiment;

[0010] FIGS. 3A-C are schematic block diagrams of a wastewater treatment system for treating wastewater, according to an embodiment;

[0011] FIGS. 4A-C are schematic block diagrams of a wastewater treatment system for treating wastewater, according to an embodiment;

[0012] FIGS. 5A-C are schematic block diagrams of a wastewater treatment system for treating wastewater, according to an embodiment; and

[0013] FIG. 6 is a flowchart of a method for treating wastewater, according to an embodiment.

DETAIFED DESCRIPTION

[0014] Embodiments disclosed herein are directed to methods for separating macromolecules (e.g., lignin) from wastewater by injecting sub-micron diameter bubbles into the waste stream. For example, the sub-micron diameter bubbles may have a diameter that is 1 pm or less, such as less than about 700 nm, about 200 nm to about 500 nm, about 50 nm to about 100 nm, or about 70 nm. Waste from biodigesters is difficult to treat with membrane processes largely due to the high concentrations of macromolecules, such as lignin, which do not breakdown during anaerobic digestion. Wastewater with these macromolecules molecules shows thixotropic properties and gelation during concentration, which easily causes membrane or heat transfer surface fouling.

[0015] Embodiments disclosed herein are also directed methods to concentrate the waste so that the waste may be economically transported to more distant fields that need the nutrients. This may reduce the cost of fertilizer for these fields as well as allow dairies and biodigester operators to comply with environmental restrictions on overfertilizing nearby fields. Embodiments disclosed herein are also directed to methods for producing a biodigester or dairy waste concentrate that is not adulterated during concentration so that the concentrate may be sold at a premium price as a certified organic fertilizer. In addition, in some embodiments, the concentrate may have highly fouling macromolecules removed so that the concentrate may be used in drip irrigation systems. Furthermore, in some embodiments, the method economically captures fugitive ammonia emissions from the process to increase fertilizer value and to reduce odor and air pollution.

[0016] Embodiments disclosed herein are substantially different from a commonly used dissolved air floatation process (DAF). DAF separate suspended solids from water by injecting air into pressurized wastewater. The water is ejected through an opening, which reduces the pressure and the dissolved air pops out of solution forming a cloud of bubbles in the water. In most DAF units, the bubbles are on the order of 30 pm to 50 pm in diameter. These bubbles attach to suspended solid particles and float them to the surface to be skimmed off. In solutions where the solids do not attach well, flocculants may be added to the wastewater to facilitate agglomeration of the solids and the attachment of the suspended solids to the bubbles. In a typical DAF, the wastewater is passed through the DAF generator one time and the aerated water is put into a quiescent tank that is big enough that the bubbles have time to rise to the surface. Typical residence times in the floatation tanks are under 30 minutes.

[0017] Standard DAF equipment is unsuccessful in floating colloidal material such as the macromolecules in biodigestate. DAF may be used if a chemical is added to the wastewater, which causes the macromolecules to floe together, but if the digestate is to be used as a fertilizer, these chemicals may be undesirable. Embodiments described herein include methods and systems of treating wastewater without addition of chemical flocculants. The methods and systems described herein may include injecting sub-micron sized air bubbles into the wastewater, effective to attach at least a portion of the sub-micron sized air bubbles to macromolecules in the wastewater to form macromolecule-coated bubbles that agglomerate and rise in the wastewater. The macromolecule-coated bubbles form a foam of the macromolecule-coated bubbles that may be separated from the wastewater.

[0018] FIGS. 1A-C are schematic block diagrams of a wastewater treatment system 100 for treating wastewater, according to an embodiment. The wastewater treatment system 100 may include a standalone system or may be a component of a larger system, such as a biodigester or a sanitation system. The initial wastewater 110 treated in the wastewater treatment system 100 may include wastewater from dairies, biodigesters, animal lots, and so on. For example, the initial wastewater 110 may include liquid digestate. In many embodiments, the initial wastewater 110 has a viscosity of about 25 cP to about 100 cP, about 40 cP to about 90 cP, about 55 cP to about 80 cP, about 40 cP to about 50 cP, about 50 cP to about 60 cP, about 60 cP to about 70 cP, about 70 cP to about 80 cP, about 80 cP to about 90 cP, at least about 40 cP, at least about 50 cP, at least about 60 cP, at least about 70 cP, at least about 80 cP, or at least about 90 cP.

[0019] The wastewater treatment system 100 includes a first chamber 102 having a collection hole 105 and an air injector 104. The first chamber 102 may include any of a number of different chambers, such as a sealable tank. In some embodiments, the first chamber 102 is a tank of a biodigester. The collection hole 105 may be positioned at the top of the first chamber 102, as shown in FIGS. 1A-C, or may be elsewhere in the first chamber 102, such as a sidewall. In many embodiments, the collection hole 105 is selectively closeable or sealable.

[0020] FIG. 1A shows the initial wastewater 110 in the first chamber 102 before the air injector 104 has injected air into the wastewater 110. The initial wastewater 110 may be directed into the first chamber 102 before the sub-micron sized air bubbles are injected into the initial wastewater 110, or, alternatively, the initial wastewater 110 may be formed within the first chamber 102 through a prior treatment in the first chamber 102, such as aerobic or anaerobic digestion. In operation of the wastewater treatment system 100, the initial wastewater 110 fills less than 100% of the volume of the first chamber 102 before the air injector 104 begins injecting the sub-micron sized air bubbles into the wastewater 110. For example, the initial wastewater 110 may fill less than 90% of the volume of the first chamber 102, less than 80% of the volume of the first chamber 102, less than 70% of the volume of the first chamber 102, less than 60% of the volume of the first chamber 102, less than 50% of the volume of the first chamber 102, less than 40% of the volume of the first chamber 102, less than 30% of the volume of the first chamber 102, less than 20% of the volume of the first chamber 102, less than 10% of the volume of the first chamber 102, about 10% to about 90% of the volume of the first chamber 102, about 20% to about 80% of the volume of the first chamber 102, about 30% to about 80% of the volume of the first chamber 102, about 40% to about 80% of the volume of the first chamber 102, about 50% to about 80% of the volume of the first chamber 102, about 20% to about 40% of the volume of the first chamber 102, about 40% to about 60% of the volume of the first chamber 102, or about 60% to about 80% of the volume of the first chamber 102. The remaining volume of the first chamber 102 where the initial wastewater 110 is absent may be filled with air 115. Accordingly, the amount of air 115 in the first chamber 102 may correspond to any of the values of the initial wastewater 110 in the first chamber 102. For example, if the initial wastewater 110 fills about 60% to about 80% of the volume of the first chamber 102, then the air 115 fills about 20% to about 40% of the first chamber 102 before the sub-micron sized air bubbles are injected into the initial wastewater 110.

[0021] The air injector 104 of the wastewater treatment system 100 is configured to inject sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102. Although shown on the bottom of the first chamber 102 in FIGS. 1A-C, the air injector 104 may be positioned elsewhere in the first chamber 102, such as a sidewall. The air injector 104 may include multiple air injectors each configured to inject sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102. Equipment for creating bubbles in solution that have diameters less than 1 pm has been developed for aerating water for the aquaculture industry. Bubbles of this diameter are stable in solution and rise extremely slowly to the surface.

[0022] The diameter of the sub-micron sized air bubbles injected into the initial wastewater 110 in the first chamber 102 by the air injector 104 may vary according to different embodiments. For example, the diameter of the sub-micron sized air bubbles injected into the wastewater 100 may be less than about 1 pm, less than about 900 nm, less than about 800 nm, less than about 700 nm, less than about 600 nm, less than about 500 nm, less than about 400 nm, less than about 300 nm, less than about 200 nm, less than about 100 nm, less than 75 nm, less than about 50 nm, about 50 nm to about 100 nm, about 100 nm to about 150 nm, about 150 nm to about 200 nm, about 200 nm to about 250 nm, about 250 nm to about 300 nm, about 300 to about 400 nm, about 400 nm to about 500 nm, about 500 to about 600 nm, about 600 nm to about 700 nm, about 700 nm to about 800 nm, about 800 to about 900 nm, about 900 to about 950 nm, about 50 nm to about 200 nm, about 200 nm to about 500 nm, about 500 nm to about 800 nm, about 950 nm, about 900 nm, about

850 nm, about 800 nm, about 750 nm, about 700 nm, about 650 nm, about 600 nm, about

550 nm, about 500 nm, about 450 nm, about 400 nm, about 350 nm, about 300 nm, about

250 nm, about 200 nm, about 150 nm, about 140 nm, about 130 nm, about 120 nm, about

110 nm, about 100 nm, about 90 nm, about 80 nm, about 70 nm, about 60 nm, or about 50 nm.

[0023] The air injector 104 also is configured to inject the sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102 at a predetermined rate. For example, the air injector 104 may include a MOLEAER™ OPTIMUS nanobubble generator, a MOLEAER™ BLOOM nanobubble generator, a MOLEAER™ CLEAR nanobubble generator, or a MOLEAER™ BOOST nanobubble generator. The air injector 104 may inject the sub-micron sized air bubbles into the initial wastewater 110 at a predetermined rate of about 1 to about 10 standard cubic feet per hour per m³ of wastewater 110, about 1.5 to about 9 standard cubic feet per hour per m³ of initial wastewater 110, about 2 to about 8 standard cubic feet per hour per m³ of initial wastewater 110, about 2.5 to about 7 standard cubic feet per hour per m³ of initial wastewater 110, about 2 to about 4 standard cubic feet per hour per m³ of initial wastewater 110, about 4 to about 6 standard cubic feet per hour per m³ of initial wastewater 110, about 6 to about 8 standard cubic feet per hour per m³ of initial wastewater 110, about 2 to about 3 standard cubic feet per hour per m³ of initial wastewater 110, about 3 to about 4 standard cubic feet per hour per m³ of initial wastewater 110, about 4 to about 5 standard cubic feet per hour per m³ of initial wastewater 110, about 5 to about 6 standard cubic feet per hour per m³ of initial wastewater 110, about 6 to about 7 standard cubic feet per hour per m³ of initial wastewater 110, about 7 to about 8 standard cubic feet per hour per m³ of initial wastewater 110, about 2 standard cubic feet per hour per m³ of initial wastewater 110, about 2.5 standard cubic feet per hour per m³ of initial wastewater 110, about 3 standard cubic feet per hour per m³ of initial wastewater 110, about 3.5 standard cubic feet per hour per m³ of initial wastewater 110, about 4 standard cubic feet per hour per m³ of initial wastewater 110, about 4.5 standard cubic feet per hour per m³ of initial wastewater 110, about 5 standard cubic feet per hour per m³ of initial wastewater 110, about 6 standard cubic feet per hour per m³ of initial wastewater 110, about 6.5 standard cubic feet per hour per m³ of initial wastewater 110, about 7 standard cubic feet per hour per m³ of initial wastewater 110, about 7.5 standard cubic feet per hour per m³ of initial wastewater 110, greater than about 2.5 standard cubic feet per hour per m³ of initial wastewater 110, greater than about 5 standard cubic feet per hour per m³ of initial wastewater 110, greater than about 7.5 standard cubic feet per hour per m³ of initial wastewater 110, less than about 2.5 standard cubic feet per hour per m³ of initial wastewater 110, less than about 5 standard cubic feet per hour per m³ of initial wastewater 110, less than about 7.5 standard cubic feet per hour per m³ of initial wastewater 110.

[0024] The air injector 104 may inject the sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102 for a predetermined amount of time. For example, the air injector 104 may inject the sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102 for about 12 hours to about 36 hours, about 12 hours to about 18 hours, about 18 hours to about 24 hours, about 24 hours to about 30 hours, about 30 hours to about 36 hours, at least about 12 hours, at least about 14 hours, at least about 16 hours, at least about 18 hours, at least about 20 hours, at least about 22 hours, at least about 24 hours, at least about 26 hours, at least about 28 hours, at least about 30 hours, at least about 32 hours, at least about 34 hours, at least about 36 hours, about 12 hours, about 14 hours, about 16 hours, about 18 hours, about 20 hours, about 22 hours, about 24 hours, about 26 hours, about 28 hours, about 30 hours, about 32 hours, about 34 hours, or about 36 hours.

[0025] FIG. IB shows the wastewater treatment system 100 after the air injector

104 has injected the sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102. Injecting the sub-micron sized air bubbles into the initial wastewater 110 in the first chamber 102 is effective to attach at least a portion of the sub-micron sized air bubbles to macromolecules in the initial wastewater 110 to form macromolecule-coated bubbles that agglomerate and rise in the initial wastewater 110. As shown in FIG. IB, the macromolecule-coated bubbles form a foam 125 of the macromolecule-coated bubbles in the first chamber 102, resulting in a refined wastewater 120 in the chamber having a portion or substantially all of the macromolecules removed thereforem. The foam 125 may fill at least a portion of the first chamber 102 previously filled with air.

[0026] The macromolecules coating the sub-micron sized bubbles that form the foam 125 in the first chamber 102 may include one or more macromolecules, such as lignin. In conventional wastewater treatment systems, waste from biodigesters is difficult to treat with membrane processes because of the high concentrations of macromolecules, such as lignin. These macromolecules do not break down during anaerobic digestion of the wastewater. Wastewater with these macromolecules shows thixotropic properties and gelation during concentration, which causes membrane or heat transfer surface fouling. In the wastewater treatment system 100, however, injection of the sub-micron sized bubbles that form the foam 125 in the first chamber 102 removes the fouling macromolecules from the initial wastewater 110 without the use of chemical flocculants. Instead, the sub-micron sized bubbles have an electric charge that cause lignin and other macromolecules in the initial wastewater 110 to attach to the sub-micron sized bubbles. The sub-micron sized bubbles act as a flocculant, removing fouling macromolecules from the initial wastewater 110 without the use of chemical flocculants, thereby preparing an unadulterated and organic refined wastewater 120 for further concentration.

[0027] The wastewater treatment system 100 also may include a mixing system 106 configured to mix the initial wastewater 110 or the refined wastewater 120 in the first chamber 102. In many embodiments, the initial wastewater 110 is constantly mixed with the mixing system 106 while the air injector 104 injects the sub-micron sized air bubbles into the initial wastewater 110. The mixing system 106 also may mix the initial wastewater 110 before the injector 104 injects the sub-micron sized air bubbles into the wastewater 110 and may mix the refined wastewater 120 having the macromolecules removed therefrom after the injector 104 injects the sub-micron sized air bubbles into the initial wastewater 110.

[0028] The mixing system 106 may include any of a number of different systems configured to mix or recirculate the initial wastewater 110 or the refined wastewater 120 within the first chamber 102, such as a pump or a rotary blade mechanical mixer. In some embodiments, the mixing system 106 includes 20 psi centrifugal pump configured to circulate about 10 gallons per minute per each cubic foot per hour of air used. The mixing system 106 also may be configured to mix or recirculate the initial wastewater 110 or the refined wastewater 120 in the first chamber 102 with a predetermined recirculation rate. The predetermined recirculation rate may include a recirculation rate of about 2 to about 50 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 2 to about 10 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 10 to about

20 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 20 to about

30 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 30 to about

40 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 40 to about 50 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 2 to about 5 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 5 to about 10 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 10 to about 15 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 15 to about 20 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 20 to about 25 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 25 to about 30 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 30 to about 35 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 35 to about 40 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 40 to about 45 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 45 to about 50 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 2 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 4 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 6 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 8 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 10 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 15 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 20 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 25 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 30 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 35 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 40 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, at least about 45 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 10 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 15 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 20 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 25 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 30 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 35 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 40 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 45 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, less than about 50 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 2 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 5 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 10 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 15 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 20 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 25 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 30 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 35 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 40 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, about 45 m³/hour per m³ of the initial wastewater 110 in the first chamber 102, or about 50 m³/hour per m³ of the initial wastewater 110 in the first chamber 102.

[0029] FIG. 1C shows the wastewater treatment system after the foam 125 of the macromolecule-coated bubbles is removed from the first chamber 102. In many embodiments, the foam 125 of the macromolecule-coated bubbles is forced out of the collection hole 105. For example, the foam 125 of the macromolecule-coated bubbles initially formed is stiff enough that the foam 125 fills the first chamber 102 and forces the foam 125 out of the collection hole 105. Once the most or substantially all of the macromolecules are have been removed from the initial wastewater 110, the foam formed from the bubbles not coated with macromolecules is relatively light and unsubstantial. This foam formed from the bubbles not coated with macromolecules forces the heavier, more dirty foam 125 of the macromolecule-coated bubbles out of the first chamber 102 through the collection hole 105. Residues remaining on the foam formed from the bubbles not coated with macromolecules have little or no effect on subsequent processing of the refined wastewater 125.

[0030] The foam 125 of the macromolecule-coated bubbles may reside within the first chamber 102 for a residence time before being forced out or otherwise removed from the first chamber 102. The residence time of the foam 125 of the macromolecule-coated bubbles in the chamber before being forced out or otherwise removed from the first chamber 102 may be about 0.5 hour to about 5 hours, about 1 hour to about 4 hours, about 1 hour to about 2 hours, about 2 hours to about 3 hours, about 3 hours to about 4 hours, about 4 hours to about 5 hours, less than 5 hours, less than 4 hours, less than 3 hours, less than 2 hours, less than 1 hour, greater than about 5 hours, greater than about 4 hours, greater than about 3 hours, greater than about 2 hours, greater than about 1 hour, about 5 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour. [0031] At least a portion of the volume of the initial wastewater 110 before injecting sub-micron sized air bubbles into the wastewater 110 is removed with the foam 125. For example, about 5% to about 20% of the initial volume of the initial wastewater 110, about 5% to about 10%, about 10% to about 15%, about 15% to about 20%, at least about 5%, at least about 10%, at least about 15%, at least about 20%, about 5%, about 10%, about 15%, or about 20% of the initial volume of the initial wastewater 110 before injecting sub-micron sized air bubbles into the wastewater 110 may be removed with the foam 125.

[0032] With the macromolecules and a portion of the volume of the initial wastewater 110 removed with the foam 125 the refined wastewater 120 has a decreased viscosity relative to the viscosity of the initial wastewater 110 after the predetermined amount of time. For example, the refined wastewater 120 may include a viscosity of about 4 cP to about 10 cP, about 5 cP to about 8 cP, about 4 to about 6 cP, about 6 cP to about 8 cP, about 8 cP to about 10 cP, less than 10 cP, less than 9 cP, less than 8 cP, less than 7 cP, less than 6 cP, less than 5 cP, about 10 cP, about 9 cP, about 8 cP, about 7 cP, about 6 cP, about 5 cP, or about 4 cP.

[0033] FIGS. 2A-C show a wastewater treatment system 200. The wastewater treatment system 200 may include the same or similar components of the wastewater treatment system 100 described above, such as a first chamber 102, an air injector 104, and mixing system 106, and a collection hole 105. The wastewater treatment system 200 also includes a second chamber 210 and a line 205 provide fluid communication between the chamber 110 and the second chamber 210. The line 205 is positioned to provide fluid communication between the chamber 110 and the second chamber 210 through the collection hole 105. In many embodiments, the line 205 includes a pipe.

[0034] As shown in FIG. 2A, the second chamber 210 may be empty before the sub-micron sized air bubbles are injected into the initial wastewater 110. The foam 125 of the macromolecule-coated bubbles is formed in the chamber 110 as the sub-micron sized air bubbles are injected into the initial wastewater 110 until the foam 125 is forced out of the collection hole 105, as described in greater detail above. In the wastewater treatment system 200, the foam 125 of the macromolecule-coated bubbles passes through the collection hole 105 and into the line 205, and from the line 205 into the second chamber 210, as shown in FIG. 2B.

[0035] Turning to FIG. 2C, once in the second chamber 210, the foam 125 of the macromolecule-coated bubbles may be reduced from a foam to a liquid sludge 225 by bursting or popping the macromolecule-coated bubbles. In some embodiments, the foam 125 may be reduced to a liquid sludge 225 with a defoamer. Alternatively, the secondary chamber may include a mechanical device such as a fan configured to burst the macromolecule-coated bubbles and reduce the foam 125 to a liquid sludge 225. The liquid sludge 225 may include about 10% of the liquid volume of the initial wastewater 110. The viscosity of the liquid sludge 225 is significantly greater than the viscosity of the initial wastewater and the refined wastewater. For example, the viscosity of the liquid sludge 225 may be at least about 100 cP, at least about 200 cP, at least about 300 cP, at least about 400 cP at least about 500 cP, at least about 600 cP, at least about 700 cP, at least about 800 cP, at least about 900 cP, at least about 1000 cP, at least about 1100 cP, at least about 1200 cP, at least about 1300 cP, at least about 1400 cP, at least about 1500 cP, about 200 cP to about 400 cP, about 400 cP to about 600 cP, about 600 cP to about 800 cP, about 800 cP to about 1000 cP, about 1000 cP to about 1200 cP, or about 1200 cP to about 1400 cP. The liquid sludge 225 from the second chamber 210 may be composted as an organic fertilizer.

[0036] FIGS. 3A-C show a wastewater treatment system 300. The wastewater treatment system 300 may include the same or similar components of the wastewater treatment system 100 described above, such as a first chamber 102, an air injector 104, and mixing system 106, and a collection hole 105. The wastewater treatment system 300 also includes a concentration system 310 in fluid communication with the first chamber 102. The concentration system 310 may include at least one of a forward osmosis concentration system or a reverse osmosis concentration system. In some embodiments, the forward osmosis system includes a forward osmosis concentration system as disclosed in PCT International Application No. PCT/US2017/062066, which is incorporated herein, in its entirety.

[0037] Turning to FIG. 3B, and as described in greater detail above, injection of the sub-micron sized air bubbles into the initial wastewater 110 removes at least a portion or all of the macromolecules from the initial wastewater 110, resulting in a foam 125 of the macromolecule-coated bubbles and the refined wastewater 120. The foam 125 of the macromolecule-coated bubbles may then be removed from the first chamber 102.

[0038] Turning to FIG. 3C, the refined wastewater 120 may be introduced to the concentration system 310. With at least a portion or all of the macromolecules removed from the refined wastewater 120, the refined wastewater 120 is suitable for concentration with membrane processing systems such as a forward osmosis system or a reverse osmosis system. In the concentration system 310, the refined wastewater 120 may be concentrated to form a concentrate. In embodiments including a forward osmosis concentration system, the pH of the refined wastewater 120 drops during concentration because molecular ammonia moves from the feed into the draw of the forward osmosis concentration system. For example, the pH may drop from about 8.8 in the refined wastewater 120 to less than about 7.5 in the concentrate during an 80% concentration. This drop in pH is beneficial because formation of struvite crystals (which cause abrasion problems in pumps and on membranes) during concentration may be avoided.

[0039] Refinement and concentration of the initial wastewater 110 with wastewater treatment system 300 allows for easier and more economical transportation of the wastewater to more distant fields in need of nutrients found in the wastewater. This transportation of the refined and concentrated wastewater also may reduce the cost of fertilizer for these distant fields, as well as allow dairies and biodigester operators to comply with environmental restrictions on over- fertilizing more near fields. Moreover, because the macromolecules were removed from the wastewater 110 without chemical flocculants, the concentrate formed from the refined wastewater 120 in the concentration system 310 may be marketed as a certified organic fertilizer suitable for drip irrigation systems.

[0040] FIGS. 4A-C show a wastewater treatment system 400. The wastewater treatment system 400 may include the same or similar components of the wastewater treatment systems 100, 200, and 300 described above, such as a first chamber 102, an air injector 104, and mixing system 106, a collection hole 105, a line 205, a second chamber 210, and a concentration system 310. The wastewater treatment system 400 is configured to inject sub-micron sized air bubbles into the wastewater 110 to form a refined wastewater 120 and foam 125 of macromolecule-coated bubbles, move the foam 125 of macromolecule-coated bubbles from the first chamber 102 to the second chamber 210, reduce to the foam 125 of macromolecule-coated bubbles in the second chamber 210 to a liquid sludge 225, and concentrate the refined wastewater 120 in a concentration system 310.

[0041] FIGS. 5A-C show a wastewater treatment system 500. The wastewater treatment system 500 may include the same or similar components of the wastewater treatment systems 100, 200, 300, and 400 described above, such as a first chamber 102, an air injector 104, and mixing system 106, a collection hole 105, a line 205, a second chamber 210, and a concentration system 310. The wastewater treatment system 500 is configured to inject sub-micron sized air bubbles into the wastewater 110 to form a refined wastewater 120 and foam 125 of macromolecule-coated bubbles, move the foam 125 of macromolecule-coated bubbles from the first chamber 102 to the second chamber 210, reduce to the foam 125 of macromolecule-coated bubbles in the second chamber 210 to a liquid sludge 225, and concentrate the refined wastewater 120 in a concentration system 310.

[0042] The wastewater treatment system 500 also includes a line 505 providing fluid communication between the second chamber 210 and the concentration system 310. When the air injector 104 injects the sub-micron sized air bubbles into the initial wastewater 110 and the foam 125 of macromolecule-coated bubbles are formed, emissions of ammonia from the wastewater also may be captured and transferred to the second chamber 210. Ammonia may be in the form of ammonium sulfate when captured in the second chamber 210. When the foam 125 of the macromolecule-coated bubbles is reduced to the liquid sludge 225 by bursting the macromolecule-coated bubbles, fugitive emissions of ammonia 510 may be captured in the second chamber 210. These fugitive emissions of ammonia 510 may then be transferred from the second chamber 210 through the line 505 into an acidic draw solution tank of a forward osmosis concentration system of the concentration system 310. The ammonia in the gas may be scavenged by the acid in the acid draw solution tank to form an ammonia salt, which ammonia salt may then be used as the draw solution in the forward osmosis concentration system. Excess ammonia salt in the draw solution also may be used as a fertilizer.

[0043] Also contemplated as part of this disclosure are one or more methods of treating wastewater. FIG. 6 is an example flowchart of a method 600 of treating wastewater without the addition of chemical flocculants. An example method may include one or more operations, functions or actions illustrated by one or more blocks of 605, 610, 615, 620, 625, 630, and/or 635.

[0044] The method allows a user to treat wastewater. An example method may include block 605, which recites“providing wastewater in a first chamber.” Block 605 may be followed by block 610, which recites“injecting sub-micron sized air bubbles into wastewater in the first chamber, effective to form a foam of macromolecule-coated bubbles.” Block 610 may be followed by block 615, which recites“removing the foam from the first chamber.” In some embodiments, block 615 may be followed by block 620, which recites“concentrating the refined wastewater in a concentration system.” In some embodiments, block 615 also may be followed by block 625, which recites“collecting the foam in a second chamber.” Block 625 may followed by block 630, which recites “reducing the foam to a liquid sludge.” In some embodiments, block 630 may be followed by block 635, which recites“capturing ammonia in the second chamber and transferring the ammonia captured to a concentration system.” Block 630 may be followed by block 620, which recites“concentrating the refined wastewater in a concentration system.”

[0045] The blocks included in the described example methods are for illustration purposes. In some embodiments, the blocks may be performed in a different order. In some other embodiments, various blocks may be eliminated. In still other embodiments, various blocks may be divided into additional blocks, supplemented with other blocks, or combined together into fewer blocks. Other variations of these specific blocks are contemplated, including changes in the order of the blocks, changes in the content of the blocks being split or combined into other blocks, etc.

[0046] Block 605 recites“providing wastewater in a first chamber.” The initial wastewater provided in the first chamber may include wastewater from dairies, biodigesters, animal lots, and so on. For example, the initial wastewater provided in the first chamber may include liquid digestate. The initial wastewater provided in the first chamber may be directed into the first chamber before sub-micron sized air bubbles are injected into the initial wastewater, or, alternatively, the initial wastewater may be formed within the first chamber through a prior treatment in the first chamber, such as aerobic or anaerobic digestion. In many embodiments, the initial wastewater provided in the first chamber has a viscosity of about 25 cP to about 100 cP, about 40 cP to about 90 cP, about 55 cP to about 80 cP, about 40 cP to about 50 cP, about 50 cP to about 60 cP, about 60 cP to about 70 cP, about 70 cP to about 80 cP, about 80 cP to about 90 cP, at least about 40 cP, at least about 50 cP, at least about 60 cP, at least about 70 cP, at least about 80 cP, or at least about 90 cP.

[0047] Providing wastewater in the first chamber may include providing initial wastewater to fill less than 100% of the volume of the chamber before the air injector 104 begins injecting the sub-micron sized air bubbles into the initial wastewater. For example, the initial wastewater provided in the first chamber may fill less than 90% of the volume of first chamber, less than 80% of the volume of the first chamber, less than 70% of the volume of the first chamber, less than 60% of the volume of the first chamber, less than 50% of the volume of the first chamber, less than 40% of the volume of the first chamber, less than 30% of the volume of the first chamber, less than 20% of the volume of the first chamber, less than 10% of the volume of the first chamber, about 10% to about 90% of the volume of the first chamber, about 20% to about 80% of the volume of the first chamber, about 30% to about 80% of the volume of the first chamber, about 40% to about 80% of the volume of the first chamber, about 50% to about 80% of the volume of the first chamber, about 20% to about 40% of the volume of the first chamber, about 40% to about 60% of the volume of the first chamber, or about 60% to about 80% of the volume of the first chamber. The remaining volume of the first chamber where the initial wastewater is absent may be filled with air. Accordingly, the amount of air in the first chamber may correspond to any of the values of the initial wastewater in the first chamber. For example, if the initial wastewater 110 fills about 60% to about 80% of the volume of the first chamber, then the air 115 fills about 20% to about 40% of the first chamber before the sub-micron sized air bubbles are injected into the initial wastewater.

[0048] Providing the wastewater in the first chamber also may include mixing the initial wastewater in the first chamber with a pump at a predetermined recirculation rate. The predetermined recirculation rate may include a recirculation rate of about 2 to about 50 m³/hour per m³ of the initial wastewater in the first chamber, about 2 to about 10 m³/hour per m³ of the initial wastewater in the first chamber, about 10 to about 20 m³/hour per m³ of the initial wastewater in the first chamber, about 20 to about 30 m³/hour per m³ of the initial wastewater in the first chamber, about 30 to about 40 m³/hour per m³ of the initial wastewater in the first chamber, about 40 to about 50 m³/hour per m³ of the initial wastewater in the first chamber, about 2 to about 5 m³/hour per m³ of the initial wastewater in the first chamber, about 5 to about 10 m³/hour per m³ of the initial wastewater in the first chamber, about 10 to about 15 m³/hour per m³ of the initial wastewater in the first chamber, about 15 to about 20 m³/hour per m³ of the initial wastewater in the first chamber, about 20 to about 25 m³/hour per m³ of the initial wastewater in the first chamber, about 25 to about 30 m³/hour per m³ of the initial wastewater in the first chamber, about 30 to about 35 m³/hour per m³ of the initial wastewater in the first chamber, about 35 to about 40 m³/hour per m³ of the initial wastewater in the first chamber, about 40 to about 45 m³/hour per m³ of the initial wastewater in the first chamber, about 45 to about 50 m³/hour per m³ of the initial wastewater in the first chamber, at least about 2 m³/hour per m³ of the initial wastewater in the first chamber, at least about 4 m³/hour per m³ of the initial wastewater in the first chamber, at least about 6 m³/hour per m³ of the initial wastewater in the first chamber, at least about 8 m³/hour per m³ of the initial wastewater in the first chamber, at least about 10 m³/hour per m³ of the initial wastewater in the first chamber, at least about 15 m³/hour per m³ of the initial wastewater in the first chamber, at least about 20 m³/hour per m³ of the initial wastewater in the first chamber, at least about 25 m³/hour per m³ of the initial wastewater in the first chamber, at least about 30 m³/hour per m³ of the initial wastewater in the first chamber, at least about 35 m³/hour per m³ of the initial wastewater in the first chamber, at least about 40 m³/hour per m³ of the initial wastewater in the first chamber, at least about 45 m³/hour per m³ of the initial wastewater in the first chamber, less than about 10 m³/hour per m³ of the initial wastewater in the first chamber, less than about 15 m³/hour per m³ of the initial wastewater in the first chamber, less than about 20 m³/hour per m³ of the initial wastewater in the first chamber, less than about 25 m³/hour per m³ of the initial wastewater in the first chamber, less than about 30 m³/hour per m³ of the initial wastewater in the first chamber, less than about 35 m³/hour per m³ of the initial wastewater in the first chamber, less than about 40 m³/hour per m³ of the initial wastewater in the first chamber, less than about 45 m³/hour per m³ of the initial wastewater in the first chamber, less than about 50 m³/hour per m³ of the initial wastewater in the first chamber, about 2m³/hour per m³ of the initial wastewater in the first chamber, about 3 m³/hour per m³ of the initial wastewater in the first chamber, about 4 m³/hour per m³ of the initial wastewater in the first chamber, about 5 m³/hour per m³ of the initial wastewater in the first chamber, about 6 m³/hour per m³ of the initial wastewater in the first chamber, about 7 m³/hour per m³ of the initial wastewater in the first chamber, about 8 m³/hour per m³ of the initial wastewater in the first chamber, about 9 m³/hour per m³ of the initial wastewater in the first chamber, or about 10 m³/hour per m³ of the initial wastewater in the first chamber, about 15 m³/hour per m³ of the initial wastewater in the first chamber, about 20 m³/hour per m³ of the initial wastewater in the first chamber, about 25 m³/hour per m³ of the initial wastewater in the first chamber, about 30 m³/hour per m³ of the initial wastewater in the first chamber, about 35 m³/hour per m³ of the initial wastewater in the first chamber, about 40 m³/hour per m³ of the initial wastewater in the first chamber, about 45 m³/hour per m³ of the initial wastewater in the first chamber, or about 50 m³/hour per m³ of the initial wastewater in the first chamber.

[0049] Block 610 recites“injecting sub-micro sized air bubbles into wastewater in the first chamber, effective to form a foam of macromolecule-coated bubbles.” The sub micron sized air bubbles injected into the initial wastewater in the first chamber are effective to attach at least a portion of the sub-micron sized air bubbles to macromolecules in the initial wastewater to form macromolecule-coated bubbles that agglomerate and rise in the initial wastewater. The macromolecule-coated bubbles form a foam of the macromolecule-coated bubbles as the macromolecules are removed from the initial wastewater, leaving a refined wastewater in the first chamber. The foam of the macromolecule-coated bubbles may fill at least a portion of the first chamber previously filled with air.

[0050] In many embodiments, injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber includes injecting into the initial wastewater in the first chamber sub-micron sized air bubbles having a diameter of less than about 1 pm, less than about 900 nm, less than about 800 nm, less than about 700 nm, less than about 600 nm, less than about 500 nm, less than about 400 nm, less than about 300 nm, less than about 200 nm, less than about 100 nm, less than 75 nm, less than about 50 nm, about 50 nm to about 100 nm, about 100 nm to about 150 nm, about 150 nm to about 200 nm, about 200 nm to about 250 nm, about 250 nm to about 300 nm, about 300 to about 400 nm, about 400 nm to about 500 nm, about 500 to about 600 nm, about 600 nm to about 700 nm, about 700 nm to about 800 nm, about 800 to about 900 nm, about 900 to about 950 nm, about 50 nm to about 200 nm, about 200 nm to about 500 nm, about 500 nm to about 800 nm, about 950 nm, about 900 nm, about 850 nm, about 800 nm, about 750 nm, about 700 nm, about 650 nm, about 600 nm, about 550 nm, about 500 nm, about 450 nm, about 400 nm, about 350 nm, about 300 nm, about 250 nm, about 200 nm, about 150 nm, about 140 nm, about 130 nm, about 120 nm, about 110 nm, about 100 nm, about 90 nm, about 80 nm, about 70 nm, about 60 nm, or about 50 nm.

[0051] In many embodiments, injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber includes injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber at a predetermined rate. For example, the method 600 include injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber at a predetermined rate of about 1 to about 10 standard cubic feet per hour per m³ of the initial wastewater, about 1.5 to about 9 standard cubic feet per hour per m³ of initial wastewater, about 2 to about 8 standard cubic feet per hour per m³ of initial wastewater, about 2.5 to about 7 standard cubic feet per hour per m³ of initial wastewater, about 2 to about 4 standard cubic feet per hour per m³ of initial wastewater, about 4 to about 6 standard cubic feet per hour per m³ of initial wastewater, about 6 to about 8 standard cubic feet per hour per m³ of initial wastewater, about 2 to about 3 standard cubic feet per hour per m³ of initial wastewater, about 3 to about 4 standard cubic feet per hour per m³ of initial wastewater, about 4 to about 5 standard cubic feet per hour per m³ of initial wastewater, about 5 to about 6 standard cubic feet per hour per m³ of initial wastewater, about 6 to about 7 standard cubic feet per hour per m³ of initial wastewater, about 7 to about 8 standard cubic feet per hour per m³ of initial wastewater, about 2 standard cubic feet per hour per m³ of initial wastewater, about 2.5 standard cubic feet per hour per m³ of initial wastewater, about 3 standard cubic feet per hour per m³ of initial wastewater, about 3.5 standard cubic feet per hour per m³ of initial wastewater, about 4 standard cubic feet per hour per m³ of initial wastewater, about 4.5 standard cubic feet per hour per m³ of initial wastewater, about 5 standard cubic feet per hour per m³ of initial wastewater, about 6 standard cubic feet per hour per m³ of initial wastewater, about 6.5 standard cubic feet per hour per m³ of initial wastewater, about 7 standard cubic feet per hour per m³ of initial wastewater, about 7.5 standard cubic feet per hour per m³ of initial wastewater, greater than about 2.5 standard cubic feet per hour per m³ of initial wastewater, greater than about 5 standard cubic feet per hour per m³ of initial wastewater, greater than about 7.5 standard cubic feet per hour per m³ of initial wastewater, less than about 2.5 standard cubic feet per hour per m³ of initial wastewater, less than about 5 standard cubic feet per hour per m³ of initial wastewater, less than about 7.5 standard cubic feet per hour per m³ of the initial wastewater.

[0052] In some embodiments, the predetermined rate of injecting air bubbles into the initial wastewater may be correlated to the predetermined circulation rate. For example, the predetermined rate of injecting air bubbles into the initial wastewater may be about 0.5 to about 1 cubic feet per hour for every 1 m³/hour per m³ of the initial wastewater of the recirculation rate. Accordingly, if the recirculation rate is about 10 m³/hour per m³ of the initial wastewater, then the predetermined rate of injecting air bubbles into the wastewater may be about 5 to about 10 cubic feet per hour; if the recirculation rate is about 20 m³/hour per m³ of the initial wastewater, then the predetermined rate of injecting air bubbles into the wastewater may be about 10 to about 20 cubic feet per hour, and so on. In many embodiments, about 100 cubic feet of air are required to completed about 1 m³ of digestate.

[0053] In many embodiments, injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber includes injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber for a predetermined amount of time. For example, the method 600 may include injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber for a predetermined amount of time of about 3 hours to about 36 hours, about 3 hours to about 6 hours, about 6 hours to about 12 hours, about 12 hours to about 18 hours, about 18 hours to about 24 hours, about 24 hours to about 30 hours, about 30 hours to about 36 hours, at least about 3 hours, at least about 6, at least about l2hours, at least about 14 hours, at least about 16 hours, at least about 18 hours, at least about 20 hours, at least about 22 hours, at least about 24 hours, at least about 26 hours, at least about 28 hours, at least about 30 hours, at least about 32 hours, at least about 34 hours, at least about 36 hours, about 3 hours, about 6 hours, about 12 hours, about 14 hours, about 16 hours, about 18 hours, about 20 hours, about 22 hours, about 24 hours, about 26 hours, about 28 hours, about 30 hours, about 32 hours, about 34 hours, or about 36 hours, less than about 36 hours, less than about 30 hours, less than about 24 hours, less than about 18 hours, less than about 12 hours, less than about 9 hours, less than about 6 hours, or less than about 3 hours. In some embodiments, the predetermined amount of time is reduced if the predetermined rate of injecting air bubbles into the initial wastewater is held constant relative to the predetermined circulation rate, as described above.

[0054] In many embodiments, injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber includes injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber while the initial wastewater is being recirculated in the first chamber. For example, the method 600 may include injecting the sub-micron sized air bubbles into the initial wastewater in the first chamber while the initial wastewater is being recirculated at any of the rates described above.

[0055] Block 615 recites“removing the foam from the first chamber.” In some embodiments, removing the foam from the first chamber includes forcing the foam of the macromolecule-coated bubbles out of a collection hole in the first chamber. For example, the foam of the macromolecule-coated bubbles initially formed is stiff enough that the foam fills the first chamber and forces the foam out of the collection hole. Once the most or substantially all of the macromolecules are have been removed from the initial wastewater, the foam formed from the bubbles not coated with macromolecules is relatively light and unsubstantial. This foam formed from the bubbles not coated with macromolecules forces the heavier, more dirty foam of the macromolecule-coated bubbles out of the first chamber through the collection hole. Residues remaining on the foam formed from the bubbles not coated with macromolecules have little or no effect on subsequent processing of the refined wastewater. Allowing the foam to remain in the first chamber before being forced out of the collection hole may allow more of the liquid to remain in the first chamber for treatment with the concentration system, and also produce a more viscous liquid in the second chamber.

[0056] In many embodiments, removing the foam from the first chamber includes removing the foam of the macromolecule-coated bubbles from the first chamber after the foam has been formed and resided in the first chamber for a residence time. For example, the method 600 may include removing the foam of the macromolecule-coated bubbles from the first chamber after the foam has been formed and resided in the in the first chamber for a residence time of about 0.5 hour to about 5 hours, about 1 hour to about 4 hours, about 1 hour to about 2 hours, about 2 hours to about 3 hours, about 3 hours to about 4 hours, about 4 hours to about 5 hours, less than 5 hours, less than 4 hours, less than 3 hours, less than 2 hours, less than 1 hour, greater than about 5 hours, greater than about 4 hours, greater than about 3 hours, greater than about 2 hours, greater than about 1 hour, about 5 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour.

[0057] When removing the foam from the first chamber, at least a portion of the volume of the initial wastewater is removed with the foam. For example, removing the foam from the first chamber includes removing about 5% to about 20% of the initial volume of the initial wastewater, about 5% to about 10%, about 10% to about 15%, about 15% to about 20%, at least about 5%, at least about 10%, at least about 15%, at least about 20%, about 5%, about 10%, about 15%, or about 20% of the initial volume of the initial wastewater with the foam of the macromolecule-coated bubbles. With the macromolecules and a portion of the volume of the initial wastewater removed from the first chamber with the foam of the macromolecule-coated bubbles, the refined wastewater remaining in the first chamber has a decreased viscosity relative to the viscosity of the initial wastewater after the predetermined amount of time. For example, the refined wastewater remaining in the first chamber after removing the foam may have a viscosity of about 4 cP to about 10 cP, about 5 cP to about 8 cP, about 4 to about 6 cP, about 6 cP to about 8 cP, about 8 cP to about 10 cP, less than 10 cP, less than 9 cP, less than 8 cP, less than 7 cP, less than 6 cP, less than 5 cP, about 10 cP, about 9 cP, about 8 cP, about 7 cP, about 6 cP, about 5 cP, or about 4 cP.

[0058] In many embodiments, block 615 may be followed by block 620, which recites “concentrating the wastewater in a concentration system.” The wastewater concentrated in the concentrated system has had the macromolecules removed with the foam of macromolecule-coated bubbles and is, therefore, a refined wastewater. As noted above, waste from biodigesters is typically difficult to treat with membrane process concentration systems because of the high concentrations of macromolecules, such as lignin, in the wastewater. Wastewater with these macromolecules shows thixotropic properties and gelation during concentration, which causes membrane or heat transfer surface fouling. In the method 600, however, injecting the sub-micron sized bubbles that form the foam in the first chamber removes the fouling macromolecules from the initial wastewater without the use of chemical flocculants, thereby preparing an unadulterated and organic refined wastewater for further concentration.

[0059] In some embodiments, concentrating the wastewater in a concentration system may include concentrating the refined wastewater in a reverse osmosis concentration system to form a concentrate. In some embodiments, concentrating the wastewater in a concentration system may include concentrating the refined wastewater in a forward osmosis concentration system to form a concentrate. The forward osmosis system may include a forward osmosis concentration system as disclosed in PCT International Application No. PCT/US2017/062066. Concentrating the refined wastewater in a forward osmosis concentration system reduces the pH of the refined wastewater during concentration because molecular ammonia moves from the feed into the draw of the forward osmosis concentration system. For example, the pH may drop from about 8.8 in the refined wastewater to less than about 7.5 in the concentrate during an 80% concentration in the forward osmosis concentration system. This drop in pH is beneficial because formation of struvite crystals (which cause abrasion problems in pumps and on membranes) during concentration may be avoided.

[0060] Refinement and concentration of the initial wastewater in blocks 610, 615, and 620 of the method 600 allows for easier and more economical transportation of the wastewater to more distant fields in need of nutrients found in the wastewater. This transportation of the refined and concentrated wastewater also may reduce the cost of fertilizer for these distant fields, as well as allow dairies and biodigester operators to comply with environmental restrictions on over- fertilizing more near fields. Moreover, because the macromolecules were removed from the wastewater without chemical flocculants, the concentrate formed from the refined wastewater at block 620 may be marketed as a certified organic fertilizer suitable for drip irrigation systems. [0061] In some embodiments, block 615 also may be followed by block 625, which recites“collecting the foam in a second chamber.” In some embodiments, the method 600 may include forcing the foam of the macromolecule-coated bubbles from the first chamber through a line, such as a pipe, to the second chamber, the line providing fluid communication between the first chamber and the second chamber.

[0062] Block 625 may be followed by block 630, which recites“reducing the foam to a liquid sludge.” Reducing the foam to a liquid sludge may include reducing the foam of the macromolecule-coated bubbles collected in the second chamber to a liquid sludge by bursting, popping, or otherwise destroying at least a portion of the macromolecule-coated bubbles. In some embodiments, reducing the foam of the macromolecule-coated bubbles to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles includes reducing the foam of the macromolecule-coated bubbles to the liquid sludge by bursting at least the portion of the macromolecule-coated bubbles with a mechanical device in the second chamber, such as a fan. In some embodiments, reducing the foam of the to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles includes reducing the foam of the macromolecule-coated bubbles to the liquid sludge by bursting at least the portion of the macromolecule-coated bubbles with a defoamer. In other embodiments, reducing the foam of the to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles includes reducing the foam of the macromolecule- coated bubbles to the liquid sludge by bursting at least the portion of the macromolecule- coated bubbles with both a defoamer and a mechanical device such as a fan.

[0063] Reducing the foam to a liquid sludge also may include reducing the foam of the macromolecule-coated bubbles to form a liquid sludge having a viscosity that is significantly greater than the viscosity of the initial wastewater. For example, the method 600 may include reducing the foam of the macromolecule-coated bubbles to form a liquid sludge having a viscosity of at least about 100 cP, at least about 200 cP, at least about 300 cP, at least about 400 cP, at least about 500 cP, at least about 600 cP, at least about 700 cP, at least about 800 cP, at least about 900 cP, at least about 1000 cP, at least about 1100 cP, at least about 1200 cP, at least about 1300 cP, at least about 1400 cP, at least about 1500 cP, about 200 cP to about 400 cP, about 400 cP to about 600 cP, about 600 cP to about 800 cP, about 800 cP to about 1000 cP, about 1000 cP to about 1200 cP, or about 1200 cP to about 1400 cP. The liquid sludge formed by reducing the foam may include a percentage of the volume of the initial wastewater before injecting sub-micron sized air bubbles into the initial wastewater. For example, the liquid sludge may include the portion of the volume of the initial wastewater removed with the foam, as described above. The liquid sludge formed from the reduced foam of the macromolecule-coated bubbles may be removed from the second chamber and composted as an organic fertilizer.

[0064] In some embodiments, the method 600 also may include block 635, which recites“capturing ammonia in the second chamber and transferring the ammonia captured to a concentration system.” When the sub-micron sized air bubbles are injected into the initial wastewater and the foam of macromolecule-coated bubbles are formed, emissions of ammonia from the wastewater also may be captured and transferred to the second chamber. Ammonia capture from the second chamber may be in the form of ammonium sulfate. When the foam of the macromolecule-coated bubbles is reduced to the liquid sludge, fugitive emissions of ammonia may be captured in the second chamber. The method 600, then, may include at block 635 transferring these fugitive emissions of ammonia from the secondary chamber through a line into an acidic draw solution tank of a forward osmosis concentration system of the concentration system. The ammonia in the gas may be scavenged by the acid in the acid draw solution tank to form an ammonia salt, which ammonia salt may then be used as the draw solution in the forward osmosis concentration system. Excess ammonia salt in the draw solution also may be used as a fertilizer.

[0065] Working Example

[0066] A digestate was batch processed in a sealed tank with fluid being constantly mixed. When the batch began, the tank was 80% full of the liquid digestate and the remaining 20% of the tank was filled with air. The mixing in the tank was performed by a pump with a recirculation rate of approximately 5 m³/hr per m³ of digestate. Dissolved air having sub-micron sized air bubbles was added to the digestate at a rate of 2.5 standard cubic feet per hour per m³ of digestate. During mixing of the batch with the dissolved air having sub-micron sized air bubbles, foam was formed in the tank. The foam had residence time in the tank of approximately 2 hours before the foam was forced out of a collection hole in the tank and through a pipe to a second tank. The foam was collected in the second tank and a fan was used to pop the macromolecule-coated bubbles of the foam, thereby reducing the foam to a liquid sludge. 10% of the volume of the liquid digestate was carried over to the liquid sludge in the second tank. At the end of at least 16 hours, the viscosity of the liquid digestate was reduced from a typical range of 40 cP to 90 cP to about less viscous range of 5 cP to 8 cP. The viscosity of the liquid sludge was over 1000 cP. [0067] As used herein, the term“about” or“substantially” refers to an allowable variance of the term modified by“about” or“substantially” by ±10% or ±5%. Further, the terms“less than,”“or less,”“greater than,”“more than,” or“or more” include, as an endpoint, the value that is modified by the terms“less than,”“or less,”“greater than,” “more than,” or“or more.”

[0068] While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting.

Claims

CLAIMS What is claimed is:

1. A method of treating wastewater without addition of chemical flocculants, the method comprising:

providing the wastewater in a first chamber;

injecting sub-micron sized air bubbles into the wastewater in the first chamber, effective to attach at least a portion of the sub-micron sized air bubbles to macromolecules in the wastewater to form macromolecule-coated bubbles that agglomerate and rise in the wastewater, wherein the macromolecule-coated bubbles form a foam of the macromolecule-coated bubbles; and

removing at least a portion of the foam of the macromolecule-coated bubbles from the first chamber.

2. The method of claim 1 , wherein providing the wastewater in a first chamber includes mixing the wastewater in the first chamber with a pump having a recirculation rate of about 2 m³/hour per m³ of the wastewater to about 40 m³/hour per m³ of the wastewater.

3. The method of claim 1 , wherein providing the wastewater in a first chamber includes providing the water in the first chamber such that a total volume of the first chamber is about 60% to about 80% wastewater and about 20% to about 40% air.

4. The method of claim 1, wherein injecting sub-micron sized air bubbles into the wastewater in the first chamber includes injecting the sub-micron sized air bubbles into the wastewater in the first chamber at a rate of about 2.5 to about 40 standard cubic feet per hour per m³ of wastewater.

5. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is less than about 700 nm.

6. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is less than about 500 nm.

7. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is less than about 250 nm.

8. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is less than about 100 nm.

9. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is about 200 nm to about 500 nm.

10. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is about 50 nm to about 100.

11. The method of claim 1, wherein the sub-micron sized air bubbles have a diameter that is about 70 nm.

12. The method of any claim 1, further comprising collecting the at least a portion of the foam of the macromolecule-coated bubbles in a second chamber, the at least a portion of the foam of the macromolecule-coated bubbles being forced out of a collection hole of the first chamber to the second chamber.

13. The method of claim 12, wherein the at least a portion of the foam of the macromolecule-coated bubbles resides in the first chamber about 0.5 hour to about 4 hours before being forced out of the collection hole of the first chamber to the second chamber.

14. The method of claim 12, further comprising reducing the at least a portion of the foam of the macromolecule-coated bubbles collected in the second chamber to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles.

15. The method of claim 14, wherein reducing the at least a portion of the foam of the macromolecule-coated bubbles to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles includes reducing the at least a portion of the foam of the macromolecule-coated bubbles to the liquid sludge by bursting at least the portion of the macromolecule-coated bubbles with a fan.

16. The method of claim 14, wherein reducing the at least a portion of the foam of the macromolecule-coated bubbles to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles includes reducing the at least a portion of the foam of the macromolecule-coated bubbles to the liquid sludge by bursting at least the portion of the macromolecule-coated bubbles with a defoamer.

17. The method of any claim 14, wherein about 5% to about 20% volume of the wastewater before injecting sub-micron sized air bubbles into the wastewater is removed from the first chamber with the at least a portion of the foam of the macromolecule-coated bubbles and included in the liquid sludge in the second chamber.

18. The method of claim 14, wherein a viscosity of the liquid sludge is at least about 500 cP.

19. The method of claim 14, further comprising composting the liquid sludge to form an organic fertilizer.

20. The method of claim 1, wherein a viscosity of the wastewater in the first chamber is about 5 cP to about 8 cP after injecting the sub-micron sized air bubbles into the wastewater in the first chamber and removing the at least a portion of the foam from the first chamber.

21. The method of claim 1, wherein a viscosity of the wastewater in the first chamber is about 40 cP to about 90 cP before injecting the sub-micron sized air bubbles into the wastewater in the first chamber.

22. The method of claim 1, wherein injecting sub-micron sized air bubbles into the wastewater in the first chamber includes injecting the sub-micron sized air bubbles into the wastewater in the first chamber for at least about 3 hours.

23. The method of claim 1, further comprising concentrating the wastewater in a forward osmosis concentration system after the at least a portion of the foam of the macromolecule-coated bubbles has been removed.

24. The method of claim 23, further comprising:

collecting the at least a portion of the foam of the macromolecule-coated bubbles in a second chamber, the at least a portion of the foam of the macromolecule-coated bubbles being forced out of a collection hole of the first chamber to the second chamber;

reducing the at least a portion of the foam of the macromolecule-coated bubbles collected in the second chamber to a liquid sludge by bursting at least a portion of the macromolecule-coated bubbles; and

capturing ammonia in the second chamber and transferring the ammonia captured in the second chamber into an acidic draw solution tank of the forward osmosis concentration system.

25. The method of claim 24, further comprising removing excess ammonia as ammonium sulfate from the acidic draw solution tank.

26. The method of claim 1, further comprising purifying the wastewater in a reverse osmosis system after the at least a portion of the foam of the macromolecule-coated bubbles has been removed.

27. A system for treating wastewater without addition of chemical flocculants, the system comprising:

a first chamber configured to receive wastewater therein, the first chamber including a collection hole; and an air injector configured to inject sub-micron sized air bubbles into the wastewater in the first chamber, the sub-micron sized air bubbles attaching to macromolecules in the wastewater to form macromolecule-coated bubbles that agglomerate and rise in the wastewater to form a foam of the macromolecule-coated bubbles for at least partial removal from the first chamber through the collection hole.

28. The system of claim 27, further comprising a mixing system in the first chamber configured to mix the wastewater in the first chamber, the mixing system including a pump having a recirculation rate of about 2 m³/hour per m³ of the wastewater to about 10 m³/hour per m³ of the wastewater.

29. The system of claim 27, wherein the air injector is configured to inject the sub-micron sized air bubbles into the wastewater in the first chamber at a rate of about 2.5 to about 40 standard cubic feet per hour per m³ of wastewater.

30. The system of claim 27, further comprising a second chamber fluidly coupled to the collection hole of the first chamber, wherein the foam of the macromolecule- coated bubbles forced out of the collection hole of the first chamber collect in the second chamber.

31. The system of claim 30, wherein the second chamber includes a fan configured to reduce the foam of the macromolecule-coated bubbles to a liquid sludge by bursting at least the portion of the macromolecule-coated bubbles.

32. The system of claim 27, further comprising a forward osmosis concentration system in fluid communication with the first chamber and configured to concentrate the wastewater after the foam of the macromolecule-coated bubbles has been removed.

33. The system of claim 32, further comprising:

a second chamber fluidly coupled to the collection hole of the first chamber, wherein the foam of the macromolecule-coated bubbles forced out of the collection hole of the first chamber collect in the second chamber where the foam of the macromolecule- coated bubbles is reduced to a liquid sludge; and

a line configured to transfer ammonia captured in the second chamber into the forward osmosis concentration system.

The system of claim 27, further comprising a reverse osmosis system in fluid communication with the first chamber and configured to purify the wastewater after the foam of the macromolecule-coated bubbles has been removed.