WO2025010446A1 - Compact system and method for treating urine and other wastewater - Google Patents

Abstract

Systems and methods are disclosed for the treatment and recovery of resources in waste, such as water and nitrogen. The system includes a bioreactor and a membrane filter. The bioreactor is configured to receive a waste stream and includes at least one anoxic treatment zone and at least one oxic treatment zone. The membrane filter is fluidly coupled to the bioreactor and is downstream of the at least one anoxic treatment zone and the at least one oxic treatment zone.

Description

COMPACT SYSTEM AND METHOD FOR TREATING URINE AND OTHER

WASTEWATER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to, claims priority to, and incorporates herein by reference for all purposes U.S. Provisional Patent Application No. 63/512,084, filed July 6, 2023.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] This invention was made with government support under 80NSSC18K1692 awarded by the National Aeronautics and Space Administration (NASA). The Government has certain rights in the invention.

FIELD OF THE INVENTION

[0003] The disclosed technology is generally directed to biological treatment of wastewater. More particularly, the technology is directed to regenerative biological treatment of urine and other wastewater using membranes.

BACKGROUND

[0004] With little to no resources readily available to support human life outside of Earth, planetary bases in environments such as, for example, space, the Moon, and Mars must be robust, independent, and provide all the basic requirements to support life that are naturally granted on Earth. In the case of a thirty-month mission, a single Crew Member will require 2250 kg of drinking water, 6525 kg of hygiene water (oral, handwash, shower, shave, etc.), and produce over 2000 kg of metabolic waste. The resulting cost of just water for a single astronaut is an incredible amount. Additionally, existing Environmental Control and Life Support Systems (ECLSS) technologies used in space are generally not optimized for Early Planetary Base (EPB) scenarios. [0005] Looking to one consideration, urine is notoriously difficult to treat, primarily due to its high nutrient and ion content. For example, in municipal wastewater, urine accounts for 80% of nitrogen while constituting only a small fraction of the total volume. While the formulations and compositions of EPB waste streams (e.g., humidity, hygiene, urine/flush, and laundry) are still under investigation, it is estimated that urine will account for approximately 97% of the nitrogen in such waste streams.

[0006] Some existing treatment systems only extract water from urine, utilize multiple consumable inputs, and need improved efficiency to reach a future water recovery goal of 98%. Consequently, such systems are highly dependent on a harsh chemical pretreatment method that must be constantly resupplied in order to recover water from the urine. These current challenges highlight the need for the development of alternative treatment technologies which can operate with minimum external inputs.

[0007] Waste treatment technologies can be broadly categorized into physical, chemical, and biological. In space, treatment technologies have been strictly physical-chemical as they provide rapid and consistent treatment. For example, in some current systems, urine is pretreated with hexavalent chromium and phosphoric acid to prevent the precipitation of uric acid and inhibit biological growth before Vapor Compression Distillation (VCD) is used to separate the water from a brine solution. VCD can recover approximately 85% of the water from urine. Additionally, a Brine Processor Assembly (BPA) can recover 85% to >90% water from urine by treating concentrated brine utilizing forced convection from ambient air coupled with membrane distillation to separate water from brine as vapor. This water is recovered from the existing condensate system while the concentrated brine is stored for disposal.

[0008] However, these existing systems are still being investigated for improved recovery, broader treatment capabilities, reduced odor, and reduced consumable inputs to achieve a near closed-loop architecture. For example, the hazardous pretreatment chemical for urine creates safety concerns and prevents any possibility of recovery of additional resources. Further, constant use of consumable inputs (i.e., chemical pretreatment, disposable filters, etc.) take up valuable cargo space, require expensive resupply missions, and create waste that requires disposal. Furthermore, to date, no flight-ready biological system has been developed.

[0009] The goals for waste treatment technologies include 98% water recovery and the capability of treating all forms of waste for recovery in sustainable approaches. Furthermore, while recovery of water and nutrients as a potential fertilizer are considerable, treatment systems should be able to handle scaling, corrosion, fouling, eutrophication, and inhibition caused by urine. Alternative treatment technologies need to be explored to reduce consumable inputs, expand resource recovery beyond water, and maintain efficiency and reliability. SUMMARY

[0010] Some embodiments provide a system including a bioreactor and a membrane filter. The bioreactor is configured to receive a waste stream and includes at least one anoxic treatment zone and at least one oxic treatment zone. The membrane filter is fluidly coupled to the bioreactor and is downstream of the at least one anoxic treatment zone and the at least one oxic treatment zone.

[0011] Some embodiments provide a method of waste processing. The method includes flowing a waste stream through a bioreactor comprising at least one anoxic treatment zone and at least one oxic treatment zone. The at least one anoxic treatment zone and the at least one oxic treatment zone comprise microorganisms. The method also includes flowing the waste stream from an outlet of the bioreactor through a membrane filter.

[0012] Some embodiments provide a method of waste processing. The method includes flowing a waste stream through a carbonation unit that mixes the waste stream with carbon dioxide and flowing the waste stream from the carbonation unit through a first anoxic treatment zone in a bioreactor. The method also includes flowing the waste stream from the first anoxic treatment zone through an oxic treatment zone in the bioreactor and flowing the waste stream from the oxic treatment zone through a second anoxic treatment zone in the bioreactor. The method further includes flowing the waste stream from the second anoxic treatment zone through a membrane filter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.

[0014] FIG. 1 illustrates a schematic view of an example bioregenerative system, according to some embodiments.

[0015] FIG. 2A illustrates a schematic view of an example a side stream membrane bioreactor configuration. [0016] FIG. 2B illustrates a schematic view of an example immersed membrane bioreactor configuration.

[0017] FIG. 3 illustrates a perspective view of an example bioregenerative system assembled on a racking system, according to some embodiments.

[0018] FIG. 4 illustrates a schematic view of another example bioregenerative system, according to some embodiments.

[0019] FIG. 5 illustrates a schematic view of an example system, according to some embodiments, comprising a bioregenerative system and a carbonation unit.

[0020] FIG. 6 illustrates a schematic view of another example system, according to some embodiments, comprising a bioregenerative system and a carbonation unit.

[0021] FIG. 7 illustrates an example process for treating wastewater including urine, according to some embodiments.

[0022] FIG. 8 illustrates a plot showing experimental data of pH of a carbonated urine solution over time.

[0023] FIG. 9 illustrates a plot showing experimental data of a chemical oxygen demand profile of a bioregenerative system overtime.

[0024] FIG. 10 illustrates a plot showing experimental data of a total nitrogen profile of a bioregenerative system overtime.

[0025] FIG. 11 illustrates a plot showing experimental data of an ammonia profile of a bioregenerative system overtime.

[0026] FIG. 12 illustrates a plot showing experimental data of a nitrate profile of a bioregenerative system overtime.

[0027] FIG. 13 illustrates a plot showing experimental data of a turbidity profile of a bioregenerative system overtime.

[0028] FIG. 14 illustrates a plot showing experimental data of a dissolved oxygen profile of a bioregenerative system overtime.

[0029] FIG. 15 illustrates a plot showing experimental data of a pH profile of a bioregenerative system overtime.

[0030] FIG. 16 illustrates a plot showing experimental data of a chemical oxygen demand and nitrogen removal profile of a bioregenerative system over time. DETAILED DESCRIPTION

[0031] Due to its concentrated and variable profile, the treatment of urine presents a unique set of challenges and rewards. For example, a plethora of components including ions and nutrients found in urine contribute to its dynamic profile, such as urea, phosphate, potassium, sulfate, calcium, magnesium, as well as biological constituents. As such, urine can cause issues in all sorts of systems.

[0032] The extreme concentrations of total nitrogen (TN), chemical oxygen demand (COD), alkalinity, electrical conductivity, and pH in source separated urine compared to what municipal water treatment technologies on Earth are designed to treat make such technologies impractical for urine treatment. In physical and chemical treatment systems, precipitation and scaling can cause blockages and fouling. In biological systems, the high nitrogen content often results in inhibition of treatment. For example, the high level of nutrients (e g., nitrogen (N), phosphorous (P), and potassium (K)) can cause eutrophication in biological systems and fouling in membrane filtration systems. Additionally, the highly basic pH (>9) of hydrolyzed urine presents challenges for biological treatment systems, which typically prefer a neutral pH.

[0033] In light of the above, some embodiments provide a bioregenerative system for the treatment and recovery of resources in urine, such as water and nitrogen. The bioregenerative system can be a hybrid system that uses carbonation, biological processing, and membrane filtration to treat waste and separate valuable components, e.g., capable of nitrogen conversion and removal for water purification and resource recovery. To reduce mass and volume constraints, this technology can be designed with a small footprint. Thus, the technology disclosed herein addresses the challenges of reducing the size, scale, and consumable inputs, and is a progressive step towards a sustainable architecture to achieve a near closed-loop architecture. These systems can be used for water treatment in space exploration as well as urban and rural settings.

[0034] Accordingly, FIG. 1 illustrates a bioregenerative system 100 according to some embodiments. As shown in FIG. 1, the bioregenerative system 100 can include a bioreactor 102, a pump array 104, a membrane filter unit 106, and a control system 108. In some applications, the bioregenerative system 100 can be considered a Suspended Aerobic Membrane Bioreactor (SAMBR). The bioregenerative system 100 further includes a system inlet 110 that allows the introduction of fluids or influent, such as wastewater, urine, and/or fluids from other waste streams such as humidity/condensation, hygiene, urine/flush, and laundry, and a system outlet 112 that releases water or effluent from the bioregenerative system 100. Generally, influent is pumped, via the pump array 104, in through the inlet 110 into the bioreactor 102, where it is treated, then into the membrane filter 106 for filtration, and resulting effluent exits the system 100 through the system outlet 112. Various components within the system 100 can be monitored and/or controlled via the control system 108.

[0035] Referring specifically to the bioreactor 102, according to some aspects, the bioreactor 102 can include a plurality of walls 114, an inlet 116, an outlet 118, and a cover 120. The walls 114 can include five walls, such as four sidewalls and a floor (though only three walls 114 are shown in FIG. 1), suitably configured to house microorganisms (e.g., autotrophs and heterotrophs) selected for biological processing. Each of the inlet 116 and the outlet 118 can be located within a respective wall 114 or the cover 120. In some implementations, the inlet 116 can be coupled to the inlet 110 of the bioregenerative system 100 via an influent line 122. In other implementations, the inlet 116 of the bioreactor 102 can be the same as the inlet 110 of the bioregenerative system 100. Additionally, the cover 120 can extend over an opening formed by the four sidewalls 114 and can allow gaseous byproducts such as O2, N2, and/or CO2 to escape (e.g., through openings) or to otherwise be directed away from the bioreactor 102 (e.g., through one or more valve-controlled openings).

[0036] As used herein, biological processing within the bioreactor 102 can include biological nutrient removal (BNR), which, generally, is the conversion of nitrogen within the nitrogen cycle by microorganisms and/or enzymes. With select microorganisms and environmental conditions, nitrogen can be converted to various forms to achieve a desired form, typically dinitrogen, which can be off gassed into the atmosphere. For example, in the nitrogen cycle, (1) dinitrogen gas is fixed as ammonium, commonly referred to as nitrogen fixation; (2) ammonium is oxidized by microorganisms; (3) nitrite is oxidized to nitrate; (4) nitrate is denitrified to dinitrogen gas; (5) anaerobic ammonium oxidation (anammox) converts ammonia directly to dinitrogen; and (6) nitrate/nitrite is reduced to ammonium. These conversions can be achieved by enzymes such as nitrate reductase, nitrite reductase, nitric oxide reductase, nitrous oxide reductase. These enzymes can be expressed by bacteria within the bioreactor, e.g., nitrite oxidizing bacteria (NOB) and ammonia oxidizing bacteria (AOB). Additionally, or alternatively, isolated enzymes can be added to the bioreactor. For example, in some instances, these microorganisms can be obtained from a municipal wastewater treatment plant and used to inoculate the bioreactor 102. That is, in some applications, activated sludge can be collected from a municipal wastewater treatment plant and be used to inoculate the bioreactor 102. Additionally, or alternatively, the bioreactor 102 can be configured to maintain an enzymatic solution for biological processing.

[0037] In some embodiments, the bioreactor 102 can include at least one anoxic treatment zone and at least one oxic treatment zone, where the anoxic treatment zone and the oxic treatment zone are in separate compartments. For example, AOB nitrify ammonium into nitrate under oxic conditions in the oxic treatment zone, and an anoxic treatment zone, containing NOB, denitrify the nitrate into diatomic nitrogen that then off-gasses into the atmosphere. By adjusting the active oxic and anoxic treatment zones, a blend of nitrogen conversion and removal can be tailored to suit the application. Furthermore, in some embodiments, the bioreactor 102 can include a first anoxic treatment zone, an oxic treatment zone, and a second anoxic treatment zone, where the three zones are in separate compartments. The treatment process through the three compartments can be designed as a median of a Modified-Ludzack Ettinger (MLE) process and a 4-stage Bardenpho process, as further described below.

[0038] Accordingly, in the example shown in FIG. 1, the bioreactor 102 can include three compartments 124, 126, 128, where each of the compartments 124, 126, 128 can be configured to maintain treatment zone conditions that promote the conversion of waste products and recovery of nutrients. For example, the oxidation reduction potential (ORP) can be regulated in each compartment. Additionally, the dissolved oxygen (DO) can be maintained within a specific range. For example, one or more sensors 130 in communication with the control system 108, such as an oxygen sensor, can be used to measure the dissolved oxygen. If the oxygen level is too low for aerobic conditions, e.g., according to a preset value, the control system 108 can signal a gas valve to open to allow oxygen to flow to the compartment in need of oxygen. Additional sensors 130 (e g., pH, turbidity, conductivity, oxygen reduction potential, liquid level, overflow, etc.) can be included in the bioreactor 102 in contact with the waste fluid and in communication with the control system 108.

[0039] Referring still to FIG. 1, in some embodiments, the first compartment 124 of the bioreactor 102 can be a first anoxic compartment (e.g., a pre-anoxic zone); the second compartment 126 can be an oxic compartment (e.g., an oxic zone); and the third compartment 128 can be a second anoxic compartment (e.g., a post-anoxic zone). Table 1 below summarizes the characteristics and functions of each compartment 124, 126, 128. Table 1. Characteristics of each compartment in the bioreactor 102

[0040] While specific processes through each compartment as describe further below with respect to FIG. 7, generally, the first compartment 124 can be a first anoxic treatment zone where the oxygen level is kept low. That is, the first compartment 124 can be capable of maintaining conditions (e.g., ORP and DO) to support heterotrophic microorganisms. The first anoxic zone of the first compartment 124 can allow for some of the organic nitrogen in the influent to ammonify. More specifically, as noted above, a primary function of the first anoxic zone can be denitrification and COD removal, where nitrogen is reduced via denitrification and assimilation.

[0041] The second compartment 126 can provide an oxic zone, or an aerobic zone where oxygen is present. For example, in some embodiments, a gas inlet (not shown) can be used to provide gas (e.g., oxygen) to specific zones within the bioreactor 102, such as the second compartment 126, to maintain the oxic conditions. The oxic zone of second compartment 126 can house autotrophic microorganisms and can support nitrification. That is, as noted above, a primary function of the oxic zone can be nitrification, e.g., where nitrogen is oxidized via nitrification and assimilation.

[0042] The third compartment 128 can provide a second anoxic zone and house heterotrophic microorganisms. The third compartment 128 can allow for excess oxygen to expire and supports increased nitrification. More specifically, as noted above, a primary function of the second anoxic zone can be denitrification and COD removal, where nitrogen is reduced via denitrification and assimilation. Thus, the third compartment 128 can provide continued denitrification that was incomplete in the first compartment 124. Furthermore, the third compartment 128 can be fluidly coupled to the first compartment 124 by an internal recycle line 132. For example, the internal recycle line 132 can conduct a waste stream with unconverted nitrogen compounds (e.g., ammonia and nitrate) from the third compartment 128 back to the first compartment 124 for continued treatment. In some embodiments, the third compartment 128 can be larger than the first compartment 124 and/or the second compartment 126.

[0043] The compartments 124, 126, 128 can each be fluidly connected to one another to allow for influent flow from the first compartment 124, to the second compartment 126, to the third compartment 128, and either back to the first compartment 124 or out through the outlet 118. In some embodiments, the compartments 124, 126, 128 can be fluidly connected by tubes such that fluid movement between the compartments can be controlled by the pump array 104 and/or valves (not shown). As noted above, the composition of the compartments 124, 126, 128 can utilize the fundamental principles of BNR, e.g., a process coupling AOB and NOB to nitrify ammonium to nitrate and denitrify nitrate to diatomic nitrogen, respectively, for maximum nitrogen conversion and removal. The designated nitrification and denitrification zones can be modified by expanding or reducing the zones that are aerated, allowing for controlled conversion to nitrate and nitrogen gas.

[0044] Referring now to the membrane filter 106, in some embodiments, the membrane filter 106 can include an ultrafiltration membrane 134 that separates clarified water (e.g., from the third compartment 128) from waste components such as solids, dissolved materials, and microorganisms. In some embodiments, the ultrafiltration membrane 134 can comprise ultrafiltration tubular membranes. In one embodiment, the ultrafiltration membrane 134 can include a pore size of about 0.03 micrometers (um). In some embodiments, as shown in FIGS. 1 and 2A, the membrane filter 106 can be positioned outside the bioreactor 102, e.g., as a side stream MBR (sMBR). In this configuration, one of the pumps of the pump array 104 can move fluid from the outlet 118 of bioreactor 102 through an outlet line 136 into the membrane filter 106, through the ultrafiltration membrane 134, and out the membrane filter 106 to the system outlet 112. That is, clarified water can exit the membrane 134 to the system outlet 112, while remaining solids, dissolved materials, and microorganisms can be returned to the bioreactor 102 via a return line 138. This external configuration permits the ultrafiltration membrane 134 to be cleaned in place, is much easier maintain, and mitigates fouling.

[0045] Additionally, or alternatively, as shown in FIG. 2B, the ultrafiltration membrane 134 can be incorporated within the bioreactor 102 in an internal configuration, e.g., as an immersed MBR (iMBR). In the internal configuration, the ultrafiltration membrane 134 can be submerged in the liquid of the bioreactor 102. In this configuration, an outlet of the ultrafiltration membrane can be considered the outlet 118 of the bioreactor 102. In some implementations, this configuration requires less volume for the membrane 134, allowing the system 100 to be more compact and have a lower energy demand as the pumping requirements are lowered.

[0046] Referring still to FIGS. 2A and 2B, though not shown in FIG. 1, the bioreactor 102 can also include a sludge outlet 140. The sludge outlet 140 can be located in one of the walls 114, e.g., near or at the floor of the bioreactor 102, to allow for the removal of solids, precipitation, debris, or sludge that may collect on the bottom of the bioreactor 102 during use. FIGS. 2A and 2B also show an air inlet 142, for example, for the introduction of oxygen into the bioreactor 102 (e.g., to the second compartment 126, as described above).

[0047] Referring back to FIG. 1 and, specifically, to the pump array 104 of the system 100, in some embodiments, the pump array 104 can include one or more pumps that can conduct the waste stream or influent into and through the bioreactor 102 to the system outlet 112. As described above, the membrane filter 106 can be fluidly coupled with the bioreactor 102 such that the waste stream can be conducted through the ultrafiltration membrane 134 to produce clarified water that exits the bioregenerative system 100, and reject fluid and other waste that is returned to the bioreactor 102 for further processing. In some embodiments, as shown in FIG. 1, the pump array 104 can be fluidly connected to the influent line 122, the internal recycle line 132, the outlet line 136, and/or a system outlet line 144.

[0048] Still referring to FIG. 1, the bioregenerative system 100 can further include the control system 108. The control system 108 can be coupled to, configured to receive data from, and/or configured to control the pump array 104 and the bioreactor 102. For example, as discussed above, the bioreactor 102 can include one or more sensors 130 configured to sense a condition within the bioreactor (e.g., pH, turbidity, dissolved oxygen, oxygen reduction potential), wherein the control system 108 can obtain such information from the sensors 130 to control the pump array 104, air inlet 142, other inlet or outlet valves of the bioreactor 102, or other system components. [0049] In some embodiments, the system 100 can be configured to sit within a small footprint. For example, as shown in FIG. 3, the system 100 can be housed within a racking system 146. In some embodiments, the racking system 146 can include metal framing within similar dimensions of racking systems already in use in the International Space Station, allowing for the system 100 to be easily integrated into existing racking systems 100 and allow for easy visualization of the bioregenerative system 100. More specifically, the racking system 146 of some embodiments can take on a form factor known as Expedite the PRocessing of Experiments to Space Station (EXPRESS) racks. Even though the EXPRESS racks pertain to the International Space Station, this design is a current NASA standard, is compact, easily accessible, and modular for easy integration for possible flight demonstration. Furthermore, any future form factor may likely be derivative of the EXPRESS rack to ease hardware transition. While intricately comprised of many fragments, the active volume of the EXPRESS rack may generally be composed of two shelves and powered drawers.

[0050] As shown in FIG. 3, the racking system 146 can house the bioreactor 102, the pump array 104, the membrane filter 106, and the control system 108. Associated hardware for the system 100, such as plumbing, can also be integrated into racking system 146. In some embodiments, as shown in FIG. 3, the bioreactor 102 can be located at a base of the racking system 146, the pump array 104 can be located within drawers, and the control system 108 can be located at a top portion. Components that are meant to be installed during operation and outside of the racking system frame dimensions, such as the membrane filter unit 106, can be detachable to ensure that the system 100 meets requirements for transport. According to some embodiments, in this configuration, the bioreactor 102 can be sized for active reactor volume ranges between 100-110 liters.

[0051] Turning now to FIG. 4, another bioregenerative system 100, according to some embodiments, is illustrated. The system 100 of FIG. 4 may be similar to the system 100 of FIGS. 1 and 3 and, thus, the above description directed toward the system 100 of FIGS. 1 and 3 may be applicable to the system 100 of FIG. 4, while the below description directed toward the system 100 of FIG. 4 may be applicable to the system of FIGS. 1 and 3. As such, while some components of the system 100 may not be specifically shown in FIGS. 1 and 3 but in FIG. 4, or vice versa, such components may still be included in the system 100 in some implementations.

[0052] For example, as shown in FIG. 4, the system 100 can include a bioreactor 102, a membrane filter unit 106, and a control system 108 (though not shown in FIG. 4). The pump array 104 can include a first pump, such as an influent pump 148, a second pump, such as a recirculation pump 150, a third pump, such as a membrane feed pump 152, a fourth pump, such as a membrane permeate pump 154, and/or a fifth pump, such as an aeration pump 156. Each of the pumps 148, 150, 152, 154, 156 can be in communication with and controlled by the control system 108.

[0053] Furthermore, as shown in FIG. 4, in addition to the first compartment 124 (pre-anoxic zone), second compartment 126 (oxic zone), and third compartment 128 (post-anoxic zone), the bioreactor 102 can further include a buffer zone 158 and a filtration zone 160. In some embodiments, the buffer zone 158 can be positioned before the first compartment 124 to increase retention time and, thus, allow for increased treatment. The filtration zone 160 can be positioned after the third compartment 128, in fluid communication with the reactor outlet 118, and concentrate filtered from the membrane filter unit 106 can be returned back to the filtration zone 160.

[0054] Regarding the pump array 104, the influent pump 148 can be positioned and controlled to pump influent from the system inlet 110 to the reactor inlet 116 and may also pump return activated sludge (RAS) from an RAS line 162 to the reactor inlet 116. The recirculation pump 150 can be positioned and controlled to pump recirculation fluid from the third compartment 128 back to the buffer zone 158 via the internal recycle line 132. The membrane feed pump 152 can be positioned and controlled to feed the outlet line 136 between the bioreactor outlet 118 and the membrane filter unit 106. As shown in FIG. 4, the outlet line 136 can also include a valve 164 that can be switched to either allow treated water to the membrane filter unit 106, or biomass or other material out of the bioreactor 102, either to be returned to the bioreactor 102 as RAS via the RAS line 162 or to be expelled as Waste Activated Sludge (WAS) via a WAS line 166. This can help prevent build-up at the bioreactor outlet 118. The membrane permeate pump 154 can be positioned and controlled to pump effluent (permeate) from the membrane filter unit 106 through the system outlet line 144 to the system outlet 112. The aeration pump 156 can be positioned and controlled to pump air, such as cabin air, into the second compartment 126, such as through diffusion stones (not shown). In one embodiment, the aeration pump 156 can operate at approximately 10 liters per minute (LPM).

[0055] Additionally, in some embodiments, the pumps 148-156 can serve as sampling and monitoring points throughout the system 100. For example, sensors 130 in communication with the control system 108 (not shown in FIG. 4) can be located near pump inlets or outlets to sense various characteristics of the system 100. Furthermore, in some embodiments, one or more sensors 130, such as liquid level sensors or overflow sensors, can be located in or adjacent one or more of the compartments 124, 126, 128, 158, 160. The control system 108 can obtain and use such sensor data to control the pump array 104 in order to maintain system stasis, e.g., in the event that liquid levels become too high.

[0056] Turning now to FIG. 5, a system 200, according to some embodiments, is illustrated. The system 200 of FIG. 5 incorporate the bioregenerative system 100 described above with respect to FIGS. 1-4 and may further include a carbonation unit 202.

[0057] For example, a consideration in urine treatment is the increase in pH when urea, the main form of nitrogen in urine, hydrolyzes. As shown in Reaction 1 below, urea hydrolyses with water in the presence of the enzyme, urease, to create ammonium, bicarbonate, and hydroxide. The creation of hydroxide results in a rise in pH, while the ammonium and bicarbonate increase ion concentration (electrical conductivity) and alkalinity.

Urea Hydrolysis:

[0058] Generally, a desired pH range for AOB and NOB in the bioreactor 102 is 6-7.5. When pH is increased due to urine hydrolysis (often to a pH >9), inhibition within the bioreactor 102 is a risk. Traditionally, acid addition is used when pH reduction is necessary; however, if a solution has a high alkalinity, like hydrolyzed urine, it can require large amounts of acid. In the case of space application, the need for large volumes of acid would reduce the sustainability of a bioregenerative treatment technology.

[0059] Accordingly, in some embodiments, the carbonation unit 202 can be introduced into the system 200 to help counteract this increase in pH. For example, as used herein, carbonation means the addition of carbon dioxide, CCh, to a solution for the purpose of reducing the pH. More specifically, as shown in Reaction 2, gaseous CO2 dissolves and becomes aqueous, then reacts with water to form carbonic acid (Reaction 3). The carbonic acid then dissociates to form bicarbonate and releases a hydrogen ion (Reaction 4). The bicarbonate also dissociates to produce carbonate and release another hydrogen ion (Reaction 5). The release of these hydrogen ions contributes to the reduction of pH.

Carbon Dioxide Dissolution: CO₂^ <=> CO₂(aq)

Carbonic Acid Formation: CO₂ + H₂O <=> H₂CO₃ (3)

Bicarbonate Formation: H₂CO₃

H⁺ + HCO₃ (3)

Carbonate Formation:

[0060] For the carbonation process, CO2 can be added to an influent by bubbling gaseous CO2 through the solution. Alternatively, solid CO2 can be added to a solution to provide gaseous CO2. For example, referring to FIG. 5, the carbonation unit 202 can include a carbonation column 204 located along the influent line 122. Thus, the outlet of the carbonation unit 202 may be considered the system inlet 110. As such, the pH of influent can be reduced before reaching the bioreactor inlet 116 of the system 100.

[0061] As another example, FIG. 6 illustrates a system 200 including the bioregenerative system 100 with a carbonation unit 202, according to some embodiments. As shown in FIG. 6, the carbonation unit 202 is upstream of the system 100. The carbonation unit 202 and, more specifically, the carbonation column 204, is fluidly coupled with a CO2 source 206, a waste stream source 208 (e.g., a feed tank), and the system inlet 110. The CO2 source 206 can be a cylinder supplying CO2 gas to the carbonation column 204. Excess CO2 and ammonia can be directed back to the feed tank 208 via a waste return line 210.

[0062] Accordingly, influent can be directed through the carbonation column 204 to contact carbonic acid before entering the bioreactor 102 of the system 100. More specifically, in the carbonation column 204, the gaseous CO2 mixes with the influent to form H2CO3 (carbonic acid), which provides hydrogen ions that contribute to lowering the pH of the influent (e.g., to below 8) before it enters the system 100. As shown by the arrows in FIG. 6, influent is fed through the top of an inner tube and flows down, counter-current to CO2 introduced at the bottom of the inner tube through an air stone, allowing for sufficient mass transfer of CO2 to the influent. The carbonated influent then flows up to the top of the outer tube and into the system 100. Furthermore, in some applications, the carbonation unit 202 can be used as a carbon dioxide trap to remove carbon dioxide from a gaseous stream, such as biogas from anaerobic digestion, by using an alkaline liquid such as NaOH or urine.

[0063] In light of the above, FIG. 7 illustrates a process 300, according to some embodiments, to treat waste using the above-described systems 100, 200. Generally, the process 300 can include a carbonation step 302, a pre-anoxic treatment step 304, an oxic treatment step 306, a post-anoxic treatment step 308, and a membrane filtration step 310.

[0064] More specifically, at the carbonation step 302, a waste stream from a source (e.g., a waste system or a feed tank 208) can pass through a carbonation unit 202, where CO2 contacts the waste stream to lower the pH. In some implementations, the carbonation step 302 may be considered an optional step, e.g., only when necessary. As such, in some implementations, the control system 108 can monitor a pH of the influent, e.g., via a sensor 130. If the pH is below a threshold level, e.g., within the ideal range for treatment in the bioreactor 102, the control system 108 can operate one or more valves so that the influent bypasses the carbonation unit 202 and is delivered straight to the system 100. If the pH is above the threshold level, e.g., where pH is outside the ideal range, the control system 108 can operate the valves so that the influent enters the carbonation unit 202 prior to reaching the system 100.

[0065] At the pre-anoxic treatment step 304, the output from the carbonation unit 202, considered carbonated influent, is introduced to the bioreactor 102 of the system 100, where it enters the first anoxic treatment zone in the first compartment 124. For example, the influent enters the first anoxic zone with nitrogen predominantly in the form of organic nitrogen and ammonia. Additionally, a downstream is recycled back to the first compartment 124 that introduces nitrates for nitrogen removal via denitrification, as further described below. In the first compartment 124, at least some of the organic nitrogen in the influent is ammonified. That is, the heterotrophic microorganisms break down nitrogen-containing chemicals from the waste organic matter into ammonia or ammonium salts. These heterotrophic bacteria use organic carbon as electron donors and nitrate as the acceptor. A relatively small fraction of nitrogen may be used in biomass uptake. [0066] At the oxic treatment step 306, the waste stream flows into an the oxic treatment zone, e.g., an aerobic stage, in the second compartment 126. As described above, the second compartment 126 is maintained with aerobic conditions and autotrophic microorganisms. Nitrogen in ammonia form enters this aerobic stage, where nitrification converts ammonia to nitrate. That is, ammonia oxidizing bacteria (AOB) oxidize ammonia to nitrite, plus hydrogen and water (Reaction 6 below) and nitrite oxidizing bacteria (NOB) oxidize the nitrite into nitrate (Reaction 7) in the oxic treatment zone. The overall process can be depicted as a general nitrification process shown in Reaction 8. These autotrophic bacteria use ammonia and nitrite as their non-organic electron donor and oxygen as the acceptor. Consequently, heterotrophic microorganisms oxidize organic constituents, resulting in COD reduction.

Nitritation Reaction: NH + 1.5O₂ NO₂ + 2H⁺ + H₂0 (6)

Nitrification Reaction: N0₂ + 0.50₂ N0₂ (7)

Overall Nitrification Reaction: NH + 2O₂ <-> N0₂ + 2H⁺ + H₂O (8)

[0067] At the post-anoxic treatment step 308, the waste flows into the second anoxic treatment zone in the third compartment 128. The anoxic zone in the third compartment 128 allows for any excess oxygen to expire and supports increased denitrification. In the third compartment 128 under anoxic conditions, such as in the first compartment 124, denitrifying microorganisms convert nitrate into diatomic nitrogen through a series of reduction reactions listed as Reactions 9, 10, 11, and 12 below, with the overall denitrification reaction listed in Reaction 13. Organic carbon is utilized as the electron donor in these reactions. In some examples, additional carbon sources can be used to promote the denitrification process, e.g., from excess biomass or an external source such as methanol.

Nitrate reductase

Nitrate Reduction Reaction: NO₂ + 2H⁺ + 2e~ < > NO₂ + H₂O (9)

Nitrite reductase

Nitrite Reduction Reaction: NO₂ + 2H⁺ + e~ < > NO + H₂O (10)

Nitric oxide reductase

Nitric Oxide Reduction Reaction: 2NO + 2H⁺ + 2e~ < > N₂O + H₂O (11)

Nitrous oxide reductase

Nitrous Oxide Reduction Reaction N₂O + 2//⁺ + 2e~ < => N₂ + H₂O (12)

Overall Denitrification Reaction: 2NO₂ + 12H⁺ + 10e“ <-> N₂ + 6H₂O (13) [0068] Still referring to the post-anoxic treatment step 308, the recently converted nitrogen can be off-gassed into the atmosphere or collected for re-use, the reactor contents can flow back to the first compartment 124 (or the buffer zone 158) via the internal recycle line 132, and the treated water can exit the bioreactor 102 via the reactor outlet 118. Additionally, as noted above, the designated nitrification and denitrification zones in the compartments can be modified by expanding or reducing the zones that are aerated, allowing for controlled conversion to nitrate and nitrogen gas. Such monitoring and modification can be completed by the control system 108. [0069] At the membrane filtration step 310, the treated waste stream is conducted to the membrane filter unit 106, where the waste stream is filtered via the ultrafiltration membrane 134 to produce clarified water and reject material. The reject material (e.g., solids and micro-organisms retained by the ultrafiltration membrane 134) is returned to the third compartment 128 (or the filtration zone 160), while the clarified water exits the system 100 via the system outlet 112. The control system 108 can control the pump array 104 to maintain a desired transmembrane pressure (TMP) across the ultrafiltration membrane 134.

[0070] The membrane permeate produced from the membrane filtration step 310 can be a high- quality, particulate-free effluent that is rich in nutrients for, e.g., fertigation applications. Additionally or alternatively, the membrane permeate can be further treated downstream to produce drinking water.

[0071] As noted above, this treatment process 300 can be designed as a median of a Modified- Ludzack Ettinger (MLE) process and a 4-stage Bardenpho process. For example, in contrast to a traditional MLE process, the present treatment process 300 contains both pre- and post-anoxic zones. Further, in contrast to a more complicated 4-stage Bardenpho process, a secondary aerobic zone is not included.

[0072] In light of the above, the present systems 100, 200, incorporating a Suspended Aerobic Membrane Bioreactor (SAMBR), use BNR principles in a scaled-down application with a membrane bioreactor and provides a bio generative alternative for urine treatment in locations such as space and planetary bases. The systems 100, 200 can be capable of a compact design, appropriate for such locations, can reduce the pH of hydrolyzed urine substantially to create a more ideal treatment environment, and can execute substantial nitrogen and carbon treatment of urine with hygiene dilution. Testing of components of some embodiments has been completed and the results are described in the following paragraphs.

[0073] An investigation of urine carbonation at the benchtop was completed to determine the feasibility of bubbling CO2 into urine and its ability to reduce the pH. The carbonation of urine was initially investigated by bubbling CO2 at a rate of 1 liter per minute (LPM) into 500 milliliters (mL) of hydrolyzed urine for one hour and then ceased. Samples were taken before carbonation, the hour that carbonation ceased, and 24 hours later. FIG. 8 illustrates a graph showing pH levels at time zero, i.e., pre-carbonation (bar 402), at 60 minutes when carbonation ceased (bar 404), and at 1440 minutes, i.e., 24 hours post-carbonation (bar 406). As shown in FIG. 8, the CO2 addition lowered the pH from 9.5 to 7.4 after one hour of carbonation, indicating that the CO2 dissolved into bicarbonate and a significant portion was retained as the pH stayed below 8 a day after carbonation had stopped.

[0074] Further testing was conducted to evaluate the capability of the system 100 to treat synthetic and real urine waste. Generally, one core objective of some embodiments is to convert and remove the high levels of nitrogen found in urine. Looking to space applications, with an estimated urine and flush generation of 2 and 0.3 kg/CM-day, respectively, the estimated nominal hydraulic loading for four crew members is 9.2 listers per day (L/d) (assuming ~1 kg/L density). However, to immediately begin operating the system 100 with the high -nitrogen waste would likely invite complications stemming from Free Ammonia (FA) and Free Nitrous Acid (FNA) inhibition, potentially resulting in perceived failure before fully evaluating the system 200. For example, AOB and NOB, the primary treatment consortia of the system 100, 200, can be inhibited by FA at concentrations as low as 8 and 0.08 mg-N/L respectively. For FNA, AOB and NOB can suffer inhibition at concentrations as low as 0.2 and 0.06 mg-N/L respectively. However, there is a lack of study into the maximum tolerance of FA and FNA and at nitrogen levels exceeding 1000 mg-N/L and for scenarios such as source separated urine.

[0075] Due to this knowledge gap, a phased approach was planned to allow for the consortia to acclimate increasing levels of nitrogen. The characteristics of each stage of this phased approach to testing the system 100 are shown below in Table 2. The phased approach can assess the capability of the system 100 to tolerate increasing strengths of urine and potentially at what concentration inhibition is observed.

[0076] More specifically, initial oxic and anoxic treatment assessment and validation was started with a simulated influent (synthetic waste) like that of domestic wastewater (Stages A-l to B). That is, the main objective of Stages A-l and A-2 was to assess and validate oxic zone performance and operation. The main objective of Stage B was to couple the anoxic and oxic zones and assess and validate the performance and operation with internal recirculation. Stage A-l used ammonium bicarbonate dissolved into water at approximate municipal levels. Acetic acid was subsequently added to the feed mixture to provide a carbon source for dentification in the pre-and post-anoxic zones for Stage A-2, and internal recirculation was implemented in Stage B.

[0077] Stage B is followed by introducing increasing strengths of real urine until full strength is reached (Stages C to H). That is, the main objective of Stages C to H was to assess the system’s performance and operation and acclimate consortia with increasing concentrations of urine to reach full strength. In further stages, treatment may be expanded to include simulated hygiene water. As inhibition is likely to occur as higher strengths of urine is introduced, dilution may help to reduce the FA and FNA concentrations, which can be achieved by the addition of hygiene waste stream. For example, in space applications, a crew member generates approximately 7.25 L/d of hygiene water from activities such as handwashing, showering, rinsing etc., and could dilute the urine and flush down to about 22% of its full-strength nature and reduce the likelihood of inhibition. Accordingly, in some embodiments, the feed tank 208 of the system 200 can include any or all of urine, flush water, and hygiene waste.

[0078] During this phased approach, multiple parameters were used for evaluation of system performance during each stage. Furthermore, it should be noted that any of these parameters may be evaluated by the control system 108 during operation of the system 100, 200 in some embodiments. As such, any sensors or method described herein may be incorporated into the sensor 130 of the system 100, 200, as described above. For example, COD (soluble) can be evaluated (e.g., via Hach Method 8000) to monitor the available organic substrate removed and utilized by the biological consortia (e.g., for denitrification). Total nitrogen (soluble), TN, can be evaluated (e.g., using Hach Method 10072) to track the levels of nitrogen and capture any species of nitrogen outside of ammonia and nitrate that may be produced. Ammonia-nitrogen (soluble), AN, can be evaluated (e.g., using Hach Method 10031) to track the levels of ammonia and indicate nitrification rates and ammonia consumption. Nitrate-nitrogen (soluble), NN, can be evaluated (e.g., using Hach Method 10020) to track the levels of nitrate and indicate nitrification rates. These nitrogen analyses were used to assess the system’s capability to convert and remove nitrogen via nitrification and denitrification. pH can be evaluated (e.g., using an ion selective probe) to inform the current pH environment in each sample and provide necessary information to correct pH to an ideal range, if necessary. Oxidation reduction potential, ORP can be evaluated (e.g., using an electron sensitive probe) to indicate oxic or anoxic conditions for nitrifying and denitrifying consortia, respectively. Dissolved oxygen, DO, can be evaluated (e g., using an oxygen sensitive probe) as an additional indicator of oxic or anoxic conditions for nitrifying and denitrifying consortia, respectively. Electrical conductivity, EC, can be evaluated (e.g., using a current sensitive probe) to monitor the ion content throughout the system. Turbidity was evaluated (e.g., using Mach Method 8237) as an indicator of effluent water quality. Transmembrane pressure was evaluated (e g., using a pressure transducer) to monitor the performance and health of the fdtration membrane 134.

Table 2. Characteristics of each stage of testing.

[0079] With reference to the phased approach and the results in Table 2, FIGS. 9-16 illustrate graphs of various parameters measured over time during operation of the system 100, measured from the influent, the pre-anoxic treatment zone, the oxic treatment zone, the post-anoxic treatment zone, and the permeate (or effluent). That is, FIG. 9 illustrates a graph 500 of a chemical oxygen demand (COD) profile of the system 100 over time, including measurements of the influent 502, the pre-anoxic treatment zone 504, the oxic treatment zone 506, the post-anoxic treatment zone 508, and the permeate 510. FIG. 10 illustrates a graph 600 of a total nitrogen (TN) profile of the system 100 over time, including measurements of the influent 602, the pre-anoxic treatment zone 604, the oxic treatment zone 606, the post-anoxic treatment zone 608, and the permeate 610. FIG. 11 illustrates a graph 700 of an ammonia profile of the system 100 over time, including measurements of the influent 702, the pre-anoxic treatment zone 704, the oxic treatment zone 706, the post-anoxic treatment zone 708, and the permeate 710. FIG. 12 illustrates a graph 800 of a nitrate profile of the system 100 over time, including measurements of the influent 802, the pre- anoxic treatment zone 804, the oxic treatment zone 806, the post-anoxic treatment zone 808, and the permeate 810. FIG. 13 illustrates a graph 900 of a turbidity profile of the system 100 overtime, including measurements of the permeate 902. FIG. 14 illustrates a graph 1000 of a dissolved oxygen (DO) profile of the system 100 over time, including measurements of the influent 1002, the pre-anoxic treatment zone 1004, the oxic treatment zone 1006, and the post-anoxic treatment zone 1008. FIG. 15 illustrates a graph 1100 of a pH profile of the system 100 over time, including measurements of the influent 1102, the pre-anoxic treatment zone 1104, the oxic treatment zone 1106, the post-anoxic treatment zone 1108, and the permeate 1110. FIG. 16 illustrates a graph 1200 of a COD and nitrogen removal profile of the system 100 over time, including measurements of COD 1202, total nitrogen (TN) 1204, and ammonia-nitrogen (AN) 1206.

[0080] In addition to the results shown in FIGS. 9-16, Table 3 below summarizes influent/ effluent water quality averages from the testing through Stage F. Note that influent value for turbidity exceeded a measurable range (>1000 NTU) and, thus, only effluent values are shown in Table 3.

Table 3. System influent/effluent water quality averages

[0081] In view of the results shown in Tables 2 and 3 and FIGS. 9-16, Stages Al-E have displayed considerable success. The results showed a continuous decline in COD (FIG. 9), indicating organic substrate is being consumed, presumably for denitrification (and a small fraction for assimilation) as there was an average removal of 66% of COD. This was further supported by a reduction in TN (FIG. 10) and AN (FIG. 11) with an average removal of 65% and 94%, respectively, indicating denitrification is occurring and diatomic nitrogen is being off-gassed into the atmosphere. Some fraction may have off-gassed as ammonia however, since the pH was consistently lower than 9.3 (FIG. 15), most of the nitrified nitrogen would be present as ammonium and therefore it is likely to be a marginal fraction. Nitrification as also evident as an increase throughout the system and at the effluent composed, on average, 83% of the nitrogen content. This remaining nitrate can be valuable as a fertilizer source for crop production and hydroponics. The DO in the oxic zone was consistently around 3 mg/L (FIG. 14), an ideal level for nitrification, indicating a sufficient amount of mass transfer from the air diffusion stones such that the oxygen expired by the time it reached the pre-anoxic zone. Additionally, the drop in turbidity (FIG. 13) from an unmeasurable level (>1000) to a single digit demonstrated a significant retention of particulates by the membrane and that a high-quality effluent, rich in soluble nutrients was being produced.

[0082] In light of the above, urine offers a renewable source of nitrogen and other trace elements that can support sustainable crop production as well as water recovery. As no flight-ready bioregenerative technology exists, the systems and methods described herein can expand what is known about bioregenerative waste treatment and resource recovery in space applications. In addition to expanding the knowledge of space waste treatment, the present systems and methods offer alternative bioregenerative treatment to the traditional physical/chemical technologies that require constant consumable inputs and generate hazardous byproducts. Current bioregenerative technologies under development cannot treat urine directly, are not optimized for partial gravity habitats (PGH), or are still being optimized for maximum nitrogen removal. The present systems and methods may be optimized for early planetary bases (EPB) or PGH and serve as a hybrid alternative to currently utilized treatment technologies, supporting the resource recovery loop for treating all forms of waste. For example, the system’s minimal need of consumable inputs and ability to remove 94% of the ammonia present and convert at least up to 83% of the remaining nitrogen into nitrate that can be used in fertigation applications, making it ideal for PGH applications. Accordingly, the technology of some embodiments can have an impact on sustainable urine treatment in space and on Earth.

[0083] Unless otherwise specified or indicated by context, the terms “a”, “an”, and “the” mean “one or more.” For example, “a molecule” should be interpreted to mean “one or more molecules.” [0084] As used herein, “about”, “approximately,” “substantially,” and “significantly” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which they are used. If there are uses of the term which are not clear to persons of ordinary skill in the art given the context in which it is used, “about” and “approximately” will mean plus or minus <10% of the particular term and “substantially” and “significantly” will mean plus or minus >10% of the particular term.

[0085] As used herein, the terms “include” and “including” have the same meaning as the terms “comprise” and “comprising.” The terms “comprise” and “comprising” should be interpreted as being “open” transitional terms that permit the inclusion of additional components further to those components recited in the claims. The terms “consist” and “consisting of’ should be interpreted as being “closed” transitional terms that do not permit the inclusion additional components other than the components recited in the claims. The term “consisting essentially of’ should be interpreted to be partially closed and allowing the inclusion only of additional components that do not fundamentally alter the nature of the claimed subject matter.

[0086] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0087] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0088] Preferred aspects of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred aspects may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect a person having ordinary skill in the art to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. A system comprising: a bioreactor configured to receive a waste stream; and a membrane filter fluidly coupled to the bioreactor, wherein the bioreactor comprises at least one anoxic treatment zone and at least one oxic treatment zone, wherein the membrane filter is downstream of the at least one anoxic treatment zone and the at least one oxic treatment zone.

2. The system of claim 1 further comprising a carbonation unit fluidly coupled to the bioreactor upstream of the at least one anoxic treatment zone and the at least one oxic treatment zone, wherein the carbonation unit comprises a source of CO2 and a column where a stream of CO2 from the source of CO2 mixes with the waste stream before the waste stream enters the bioreactor.

3. The system of claim 2, wherein the carbonation unit is configured to adjust a pH of the waste stream to less than 8 before entering the bioreactor.

4. The system of claim 2, wherein the carbonation unit is further configured to remove carbon dioxide from a biogas using urine.

5. The system of claim 1, wherein the at least one anoxic treatment zone and the at least one oxic treatment zone comprise microorganisms.

6. The system of claim 1, wherein the at least one oxic treatment zone comprises ammonia oxidizing bacteria and nitrite oxidizing bacteria.

7. The system of claim 1, wherein the at least one anoxic treatment zone comprises bacteria expressing nitrate reductase, nitrite reductase, nitric oxide reductase, and nitrous oxide reductase.

8. The system of claim 1, wherein the at least one anoxic treatment zone and the at least one oxic treatment zone includes a first anoxic treatment zone, an oxic zone, and a second anoxic treatment zone.

9. The system of claim 8, further comprising an internal return line, wherein the internal return line fluidly couples the first anoxic treatment zone with the second anoxic treatment zone.

10. The system of claim 1, further comprising a pump array configured to pump the waste stream through the bioreactor and the membrane filter.

11. The system of claim 10, further comprising a control system configured to control the pump array.

12. The system of claim 11, further comprising at least one sensor in the bioreactor in communication with the control system.

13. The system of claim 1, further comprising an air inlet in the bioreactor configured to provide oxygen to the at least one oxic treatment zone.

14. A method of waste processing comprising: flowing a waste stream through a bioreactor comprising at least one anoxic treatment zone and at least one oxic treatment zone, wherein the at least one anoxic treatment zone and the at least one oxic treatment zone comprise microorganisms; and flowing the waste stream from an outlet of the bioreactor through a membrane filter.

15. The method of waste processing of claim 14, further comprising pretreating the waste stream by carbonation before the waste stream enters the bioreactor, wherein the waste stream is carbonated by mixing with CO2.

16. The method of waste processing of claim 15, further comprising removing carbon dioxide from a biogas using urine from the waste stream.

17. The method of waste processing of claim 14, wherein flowing the waste stream through the bioreactor comprising the at least one anoxic treatment zone and the at least one oxic treatment zone comprises flowing the waste stream through a first anoxic treatment zone, an oxic treatment zone, and a second anoxic treatment zone.

18. The method of waste processing of claim 17, further comprising recycling a portion of the waste stream from the second anoxic treatment zone to the first anoxic treatment zone.

19. The method of waste processing of claim 14, further comprising returning a concentrate from the membrane filter back to the bioreactor.

20. The method of waste processing of claim 14, further comprising flowing the waste stream through a buffer zone in the bioreactor prior to the at least one anoxic treatment zone.

21. The method of waste processing of claim 14, further comprising off gassing nitrogen from the bioreactor.

22. A method of waste processing comprising: flowing a waste stream through a carbonation unit that mixes the waste stream with carbon dioxide; flowing the waste stream from the carbonation unit through a first anoxic treatment zone in a bioreactor; flowing the waste stream from the first anoxic treatment zone through an oxic treatment zone in the bioreactor; flowing the waste stream from the oxic treatment zone through a second anoxic treatment zone in the bioreactor; and flowing the waste stream from the second anoxic treatment zone through a membrane filter.