Anaerobic sequencing batch reactor system with batch degassing unit and semi-continuous settling unit for simultaneous operation

Abstract

The present invention relates to a method for treating an aqueous fluid containing biodegradable organic matter, the method comprising: a bioreactor unit batch feeding stage, wherein the aqueous fluid to be treated is fed into the bioreactor unit; a batch reaction stage, wherein the aqueous fluid is subjected to microbial treatment in the bioreactor unit and biogas is produced; a degassing unit feeding stage, wherein an aqueous suspension containing the microbially treated aqueous fluid and biomass is withdrawn from the bioreactor unit and fed into the degassing unit in batches; and a semi-continuous biomass separator unit feeding stage, wherein the degassed aqueous suspension is withdrawn from the batch degassing unit and fed into the biomass separator.

Description

Technical Field

[0001] The present invention relates to a method for treating an aqueous fluid containing biodegradable organic matter, the method comprising a batch reaction stage, wherein the biodegradable organic matter is converted by microorganisms to form biogas (a gas mixture usually mainly containing methane and carbon dioxide). The invention further relates to a simultaneous phase operable sequential batch reaction system. Background Art

[0002] A method for producing biogas from waste containing organic biomass in an anaerobic sequencing batch reactor (AnSBR) was developed in the early 1990s. US 5185079 A) relates to a single-vessel AnSBR operated in a cycle with four main stages: feeding, reaction, settling and decanting; sludge removal when necessary. The advantages of AnSBR include high process flexibility in terms of cycle time and sequence, the possibility of operation without the need for a clarifier, and the possibility of operation with relatively simple instrumentation. In addition, the feast / famine state caused by the sequential operation promotes the degradation of slowly degradable particulate substrates (suspended solids, oils, fats and greases) and / or relatively difficult to degrade compounds, as well as enhanced bioflocculation. In addition, due to the natural selection pressure on poorly settling sludge, sequential operation leads to the development of well-settled sludge. As a result, effective solid separation is promoted, resulting in a longer solid retention time (SRT) and efficient conversion of organic substrates to methane and carbon dioxide.

[0003] Despite the long history of AnSBR development, its industrial application has been limited. The main limitations of AnSBR appear to be the misuse of this configuration, design errors, uncertainty in sludge settling control, and challenges behind batch volume (fluid and gas) management, resulting in the need for large buffer tanks and gas storage units.

[0004] Few attempts have been made to develop variations of the AnSBR configuration to take advantage of the above advantages. For example, a process called "temperature phased AnSBR" has been proposed, in which two reactors are operated in series. The first reaction is carried out at thermophilic temperatures (55°C) and the second reaction is carried out at mesophilic levels (35°C).

[0005] US 5,599,450 A relates to another configuration developed for the AnSBR concept, which is an anaerobic upflow batch reactor. The system is intended to provide plug flow through an anaerobic waste stream treatment reactor, evenly distribute the waste stream at the bottom of the reactor and collect the waste stream at the upper level to produce an upward plug flow through the reactor during filling, recirculation and decanting, and minimize horizontal mixing. According to the inventors, this plug flow promotes the growth of heavier biomass near the bottom of the reactor where the substrate concentration is the highest, and hinders the growth of lighter biomass near the top of the reactor where the substrate concentration is the lowest.

[0006] Although there are various advantages in treating aqueous waste containing organic biomass in AnSBR, there are also typical inherent problems in known systems. In the method as described above, the reaction phase (biogas is formed by organic biomass during the reaction) and the settling phase are carried out in sequence. During the settling process, the solid moves in the direction of the bottom of the reactor, forms (concentrated) sludge at the bottom, and forms a supernatant (a fluid aqueous phase) on the top of the reactor, which has a reduced solid particle content compared to the solid particle content of the fluid content (suspension), and preferably is substantially free of solid particles. After sufficient settling, the supernatant is taken out (withdrawn, extracted) from the reactor as an effluent. In order to obtain a supernatant with low solid particle content or substantially free of solid particles, a long settling time is required because this is conducive to the downstream processing of the effluent. Therefore, at a given process cycle time, the settling duration is a limiting factor in the total decomposition capacity of organic matter and the biogas production capacity because it reduces the available time of the reaction phase. In addition, the process carried out in the AnSBR as described above characteristically has a fluctuating biogas production rate. At the beginning of the process cycle (feeding phase), the biogas production rate will gradually increase until it reaches a maximum value (usually at or near the end of the feeding phase, or in the early part of the reaction phase). After reaching the maximum biogas production rate, the reaction phase usually continues until the production rate reaches a lower threshold, after which the settling phase begins. During the settling phase, some biogas is usually still produced, but the biogas production rate usually decreases further during this phase, becoming lowest (possibly zero) during the decantation phase (where the effluent is removed). Due to fluctuations in the biogas production rate, the biogas flow rate from the reaction system fluctuates greatly, which is undesirable, especially with regard to further processing of the biogas stream downstream of the AnSBR and / or providing a constant supply of biogas for further use (e.g. in energy production).

[0007] In WO 2019 / 115034, an improved process and installation are disclosed, allowing the conversion of organic matter by microorganisms in a bioreactor and the settling of solid particles in a fluid treated in a separate container to be carried out simultaneously, and wherein the flow rate of the produced biogas out of the device can be made more constant. The process comprises (i) a bioreactor feed phase, followed by (ii) a batch reaction phase, in which biogas is formed and the formed biogas is temporarily stored in a separate container (2), and then at least one further phase (iii) comprising a settling phase and / or an aqueous fluid effluent discharge phase, in which the biogas stored in the separate container is used to reduce fluctuations in the flow rate of the biogas discharged from the device. This configuration has now been extensively tested in industrial-scale pilots, and construction of the first full-scale system is about to begin.

[0008] This process and device already offer considerable advantages, for example in terms of capital expenditure (CAPEX), operating expenditure (OPEX), robustness or tolerance to fat in the feed. However, scaling up this process / device adds a degree of complexity to the design of an external container, which can be used as a separator for solids (e.g., biomass, which contains microorganisms for forming biogas from biodegradable substances in a bioreactor) and as a degassing unit. Large volumes then need to be processed, so large diameter pipes and large capacity pumps are required to feed the external container and remove the contents from the container in a short time. For high processing capacity, a wider container is also required, and the container is pressurized in at least part of the process, which increases the complexity of providing a flexible roof. Those skilled in the art will be able to solve this problem based on the disclosure in WO 2019 / 115034, but it does increase capital expenditure. In addition, a wider diameter means a larger installation footprint.

[0009] Therefore, there remains a need to provide alternative methods / devices for treating aqueous fluids, whereby / in which biodegradable organic matter in the fluid is converted into biogas by microorganisms. In particular, there is a need for simpler methods or systems or even more compact methods or systems, more particularly methods or systems that allow for reduced capital expenditures and / or operating expenditures. The present invention addresses this need. Summary of the invention

[0010] The inventors have now discovered that a further improved process can be achieved, whereby a smaller apparatus (smaller total volume of the bioreactor and the units required for degassing the liquid and separating the liquid solids, such as the external container of WO 2019 / 115034, and / or a smaller total area (i.e., footprint) required for installation) can be used in which the process is carried out while maintaining all the biological and physicochemical advantages achieved using the WO2019 / 115034 process and maintaining the same capacity (or increasing the capacity without requiring larger apparatus and / or without requiring a larger footprint) . The inventors are particularly aware of the advantages of a way of solving these problems in an anaerobic process. However, they believe that processes operating under non-anaerobic conditions may also benefit from their discovery.

[0011] The present invention therefore relates to a method for treating an aqueous fluid comprising biodegradable organic matter in a device comprising:

[0012] - a bioreactor unit (1) in which an aqueous fluid is subjected to a microbiological treatment, thereby producing biogas from organic matter,

[0013] - a degassing unit (2) in which an aqueous suspension taken from the bioreactor is batch-wise degassed, said suspension comprising aqueous liquid, biogas and biomass, and

[0014] a semi-continuously operated biomass separator unit (3), wherein the deaerated suspension withdrawn from the deaeration unit is separated into (a) a biomass-rich sludge and (b) an aqueous fluid having a reduced biomass content compared to the deaerated suspension fed into the biomass separator unit (3),

[0015] The method comprises

[0016] - a bioreactor unit fed-batch phase, in which the aqueous fluid to be treated is fed into the bioreactor unit;

[0017] - a batch reaction stage, in which an aqueous fluid is subjected to a microbial treatment and biogas is produced in a bioreactor unit;

[0018] - a semi-continuous biomass separator unit feeding stage, in which the degassed aqueous suspension is taken from the batch degassing unit and fed into the biomass separator; and

[0019] - a degassing unit feed phase, wherein an aqueous suspension comprising the microorganism-treated aqueous fluid and the biomass is withdrawn from the bioreactor unit and fed batchwise into the degassing unit.

[0020] Between the stages, before the first stage and / or after the last stage of the stages, one or more additional stages may be employed. For example, typically, a (further) sludge return stage is performed after the semi-continuous biomass separator unit feed stage.

[0021] Typically the process comprises two or more cycles of the stages. The order of the stages is typically: first a bioreactor unit feed stage (A), then a batch reaction stage (B), then a semi-continuous biomass separator stage (C), then a (further) sludge return stage (D) and then a degassing unit feed stage (E).

[0022] The startup cycle (the first cycle, e.g. when running the method for the first time on a specific plant, or when restarting the method after stopping it, e.g. for maintenance, in which one or more units have been emptied) can have the same sequence of the cycles described, although the degassing unit (if empty) can be provided with a mock-liquid, i.e. any available liquid, e.g. water or effluent from another process, or even wastewater to be treated, etc. In the latter case, the effluent from the first cycle can be redirected to the bioreactor (or buffer tank) in order to be treated therein in the subsequent cycle. In principle, the startup cycle can also be carried out in another way, e.g. by omitting stages (C) and (D) in the first cycle.

[0023] Furthermore, the present invention relates to a sequential batch reaction system operable in simultaneous stages,

[0024] The system comprises a bioreactor unit, wherein there is an agitator for agitating an aqueous suspension in the bioreactor unit to produce biogas, the apparatus further comprises a batch degassing unit, wherein there is an agitator for agitating the aqueous suspension and is configured to degas the aqueous suspension that has been fed from the reactor unit into the batch degassing unit, the system further comprises a biomass semi-continuous separator unit configured to separate the degassed aqueous suspension from the degassing unit into a biomass-rich sludge and an aqueous effluent having a reduced biomass content compared to the degassed suspension,

[0025] The separated biomass separator unit comprises

[0026] a space for receiving the treated aqueous suspension from the degassing chamber, the space containing a liquid-solid separator unit and further comprising an inlet for the degassed aqueous suspension, the inlet being connected via a closable conduit to an outlet for the treated aqueous suspension from the degassing chamber, an outlet for removing sludge and a separate outlet for removing effluent from said separator unit via a closable conduit,

[0027] wherein the bioreactor unit and the degassing unit have a joint or separate headspace for the biogas, one or more of the headspaces comprising an outlet for the biogas,

[0028] The system further comprises an inlet for a fluid aqueous waste stream to enter the bioreactor unit, a provision for feeding an aqueous suspension from the bioreactor unit to the degassing unit.

[0029] Such a reactor system is particularly suitable for the process according to the invention.

[0030] In particular, good results have been obtained using the method according to the invention for treating an aqueous fluid, wherein a plurality of cycles are carried out, in which

[0031] - performing a bioreactor unit batch feed phase (A) (usually as the first phase of a specific cycle), wherein an aqueous fluid to be treated is fed to the bioreactor unit, while the treatment of the aqueous fluid already present in the bioreactor unit can continue, degassing the aqueous suspension in the degassing unit (fed in the previous phase or cycle) while using mixing;

[0032] - followed by a batch reaction phase (B) in which batches of an aqueous fluid are subjected to microbial treatment in a bioreactor unit and biogas is produced, and the aqueous suspension is degassed in a degassing unit while mixing;

[0033] - thereafter a biomass separator unit operation phase (c) is carried out, in which the degassed aqueous suspension is continuously withdrawn from the degassing unit and fed to the biomass separator, at least until the separator is filled to a level at which there is an outlet for the aqueous fluid with a reduced biomass content (b), and from then on, during this phase, a continuous removal of the aqueous fluid with a reduced biomass content is carried out from the biomass separator and a continuous return of the biomass-rich sludge (a) to the bioreactor unit, while the microbiological treatment of the aqueous fluid in the bioreactor unit can continue;

[0034] - a further sludge return phase (D) is then carried out, in which the feeding of the deaerated suspension from the degassing unit to the biomass separator has been completed, the withdrawal of the aqueous fluid with a reduced biomass content from the biomass separator is stopped and the return of the biomass-rich sludge to the bioreactor is continued, while the microbial treatment in the bioreactor unit can continue;

[0035] - This is followed by a batch degassing tank filling phase (E), in which, once the required volume of aqueous fluid with reduced biomass content (equal to the volume fed to the bioreactor during the batch feeding phase (A)) has been withdrawn from the biomass separator unit in the previous phase, the remaining biomass-rich sludge is returned to the bioreactor in this phase, while the microbial treatment in the bioreactor unit can continue. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 An example of a system according to the invention is schematically shown, wherein the bioreactor unit and the degassing unit are separate devices.

[0037] Figure 2 Schematic showing the use of Figure 1 A system according to the method of the present invention. In this article:

[0038] Figure 2 A shows the bioreactor unit fed-batch phase (A);

[0039] Figure 2 B shows the batch reaction stage (B);

[0040] Figure 2 C shows the biomass separator unit operation stage (C);

[0041] Figure 2 D shows a further sludge return stage (D);

[0042] Figure 2 E shows the batch degassing tank filling stage (E).

[0043] Figure 3 An example of a system according to the invention is schematically shown, wherein a bioreactor unit and a degassing unit are integrated in the same housing.

[0044] Figure 4 A-4E schematically shows the use of Figure 3 The method of the system according to the present invention is similar to Figure 2 A to 2E. DETAILED DESCRIPTION

[0045] As shown in Example 1, significant savings in the volume and occupied space of the entire reactor system are feasible. In addition, the biomass separator unit (see the external container (2) in WO 2019 / 115034) can be simplified, wherein biomass is separated from the treated aqueous fluid. In particular, simplification is achieved because fewer separation internal components (such as the inclined thin sheets preferably present) for improving separation efficiency can be used to achieve the same separation efficiency. According to the present invention, the feeding of the biomass separator, the separation of solids from the treated liquid, the decantation and return of the concentrated sludge (biomass-rich fraction) no longer need to be carried out in a separate subsequent step (also including a degassing step). The main advantage of the present invention is that all these steps can be carried out simultaneously in the biomass separator (in a semi-continuous manner throughout the cycle). Therefore, for the same volume of fluid to be treated, the available time of all these steps can be increased, thereby reducing the required flow rate (flow rate, flow), and thereby reducing the size of the pipeline and pump (which in turn saves capital expenditure). Typically, the available time of these steps is extended by at least about 2 times, preferably by at least about 3 times, and particularly by 3-4 times.

[0046] Typically, the stages of the method according to the invention are repeated multiple times. Typically, at least after the start-up cycle, one or more subsequent process cycle stages are performed, wherein first the subsequent one or more cycles of the bioreactor unit feed stage (A) are performed, followed by the batch reaction stage (B), followed by the biomass separator unit feed stage (C), then typically a further sludge return stage (D), and thereafter, as the last stage of the stage, a degassing unit feed stage (E). Optionally, there are one or more stages between the stages or one or more stages after stage (E), followed by one or more further cycles, typically repeated in the order of stage (A), followed by stage (B), followed by stage (C) (if used), followed by stage (D), followed by stage (E).

[0047] Typically, except when starting the system from the beginning (e.g., for the first time or after maintenance), the reactor usually already contains biogas-producing microorganisms. Once the microorganisms are provided to the reactor, they usually no longer need to be introduced into the reactor in subsequent process cycles.

[0048] The device according to the invention is particularly suitable for the microbiological treatment of aqueous fluids which contain biodegradable organic substances, whereby preferably in the method according to the invention biogas is formed from said biodegradable substances.

[0049] The main advantage of the present invention is that it allows simultaneous conversion of organic matter by microorganisms in a bioreactor, degassing of a batch of aqueous fluid already treated in the bioreactor in a degassing unit and, after degassing, biomass separation treatment in a biomass separator.

[0050] The aqueous fluid treated in the method according to the present invention can in principle be any aqueous fluid containing biodegradable organic matter, particularly under anaerobic conditions. Preferably, the aqueous fluid is selected from the following group: municipal wastewater, industrial wastewater (e.g., from the chemical industry or the food processing industry), agricultural wastewater, sewage, aqueous fluid waste from fermentation processes (e.g., residual fermentation broth, wastewater from brewing processes, wastewater from brewing processes). Further preferred are aqueous slurries and aqueous sludge. The slurry can be derived from the same source mentioned with the wastewater. With regard to the water content of the waste stream treated in the method according to the present invention, this can vary over a wide range. Typically, the water content of the aqueous fluid to be treated is greater than 80wt.%, particularly at least 80wt.%, more particularly 90wt.% or more of the total weight of the fluid. Typically, the water content is 99.9wt.% or less, preferably 99.5wt.% or less, more preferably 99wt.% or less, particularly 98wt.% or less, more particularly 96wt.% or less. The total organic matter content of the aqueous fluid to be treated is generally 0.1 g COD / l or more, preferably in the range of 0.3-100 g COD / l, more preferably in the range of 1.0-50 g COD / l, particularly in the range of 5-50 g COD / l, more particularly in the range of 8-50 g COD / l. In a specific embodiment, the total organic matter content is in the range of 1.0-30 g COD / l, more particularly in the range of 5-15 g / l. According to the present invention, the total organic matter content can be greatly reduced, generally exceeding 50%, preferably 70% to 100%, more preferably 75-99%, more preferably 80-97%. The method of the present invention also provides an effluent with low TSS (total suspended solids) in the aqueous effluent; typically the aqueous effluent from the biomass separator (3) contains less than 1.5 g / l TSS, particularly 1.0 g / l or less, preferably about 0.6 g / l or less. Typically, the TSS content of the aqueous effluent from the biomass separator (3) is about 0.2 g / l or more, in particular about 0.3 g / l or more, more in particular about 0.4 g / l or more. In practice, it is preferred to operate with a TSS content of the effluent in the range of about 0.4 g / l to about 0.6 g / l. The TSS content can be further reduced downstream in a manner known per se, for example by filtration.

[0051] The method according to the invention is also particularly suitable for treating waste streams with a relatively high content of fats, oils and / or grease (FOG) and / or a relatively high content of suspended solids. TSS is the solid fraction of a fluid, which can be obtained by filtering a known weight or volume of fluid using a 1.6 μm filter (dead-end filtration), removing the retentate, washing the retentate with distilled water, drying the washed retentate and determining the residual dry weight. Therefore, TSS may include inorganic substances in addition to organic substances. In order to distinguish between organic and inorganic substances, the sample is burned at 550°C, all organic substances are burned, and the sample residue is inorganic. Combustion tests are generally practical alternatives to COD tests. Typically, the TSS content of fluid waste is in the range of 0-20 g / l. The FOG content is generally in the range of 0-4 g / l. In particular, the process according to the invention (operating under conditions where the solids in the bioreactor are at least substantially flocculent) is also advantageous - for example compared to conventional processes operating under conditions where the solids in the bioreactor are at least substantially granular - for treating fluid wastes having a TSS content of 0.5 g / l or more, in particular 1.0 g / l or more, preferably 1.5-30 g / l, more preferably 2.0-20 g / l and / or a FOG content of 50 mg / l or more, in particular 0.1-4 g / l, more particularly 0.1-2 g / l. One such advantage is that the microorganisms convert the suspended solids more efficiently. A second advantage, in particular in the case of high FOG contents, is that the tendency for solids (including microorganisms) to float, which is usually caused by a high FOG content in a granular system, is reduced or completely avoided, which may result in the microorganisms being washed away.

[0052] Examples of aqueous fluids that are particularly suitable for treatment according to the present invention are aqueous wastes from dairy production or processing (e.g. production / processing of milk, cheese, butter), beverage production or processing (e.g. wine, beer, distilled beverages, juice, milk), biofuel production or processing, chemical plants or aqueous wastes from agricultural facilities.

[0053] Based on common general knowledge, the information disclosed herein and the references mentioned herein, a person skilled in the art will know how to determine the appropriate liquid content, solid content and microorganism content in a bioreactor.

[0054] The system according to the invention (used in the method) comprises several units, i.e. at least a bioreactor unit, a degassing unit and a biomass separator unit. During use, the unit performs a unit operation, such as a microbial conversion of organic matter, thereby producing biogas in the bioreactor unit, degassing in the degassing unit and separating into concentrated sludge and clarified aqueous fluid in the separator unit. In chemical engineering and related fields, a unit operation is a basic step in a process. A unit operation involves a physical change or a chemical transformation. Therefore, a unit can be a piece of equipment configured to perform a unit operation, or a unit can be a compartment of a piece of equipment comprising several compartments (units), each of which is performing a separate unit operation, i.e. a bioreactor unit and a degassing unit can be different (spaced apart) equipment, or they can both form separate parts of a single (integrated) equipment, such as a container having an inner compartment for microbial treatment and an outer compartment for degassing.

[0055] The bioreactor unit in the system or method according to the invention is typically a bioreactor configured for operation under anaerobic conditions (gas-tight; typically at 2-50 mbar above atmospheric pressure).

[0056] The bioreactor can be based on known systems for batch microbial processing of aqueous fluids. The bioreactor typically comprises an agitator, such as one or more agitators, for stirring the aqueous fluid in the bioreactor. Preferably, the bioreactor is configured to operate using flocculent biomass (including microorganisms that degrade organic matter into biogas).

[0057] The degassing unit in the system according to the present invention is typically also an agitation system, such as a stirring system, which is configured to operate under anaerobic conditions (airtight, typically at 2-50 mbar above atmospheric pressure). Typically, the head space is connected to the bioreactor head space to allow biogas to be transferred from one to another when the contents are transferred from / to the bioreactor. Preferably, a plurality of agitators, in particular agitators, are present at different heights in the degassing unit. The agitators are agitators that are preferably positioned to cause the fluid to circulate in a substantially vertical direction, respectively. Therefore, agitators are preferably provided so that they can rotate around a substantially horizontal axis. Compared to external containers such as WO 2019 / 115034, the present invention allows the use of relatively slender and tall degassing tanks. In order to save occupied space, the height of the degassing unit is typically about 3m or more, preferably about 5m or more. Relatively tall degassing units are effective because no sedimentation is required in the degassing unit (which is advantageous for units with relatively shallow sedimentation, as is the case in the external container of WO 2019 / 115034), thereby allowing a smaller diameter in the horizontal direction, saving space. The height is usually about 10m or less, in particular 6-8m. The internal space (volume) of the bioreactor (1) for accommodating the fluid to be treated by microorganisms plus the top space is usually about 1.5 to about 10 times, preferably about 2 to about 6 times, and especially 3-5 times, the internal space (volume) for accommodating the fluid suspension to be degassed plus the top space of the degassing unit.

[0058] The degassing unit is a unit separate from the biomass separator. Like the external container of WO 2019 / 115034, it can also be used as a biogas storage unit, but it is not mandatory. Its top plate is usually made of a rigid material, i.e. it will not deform, expand or contract due to changes in the (biogas) pressure in the head space; it can be the same or similar to one or more side walls in terms of material properties (e.g. stiffness, mechanical strength). The degassing unit can be opened during the method according to the invention, for example for maintenance, during the phases of the process that are not used for biomass separation. In this case, the gas connection between the bioreactor head space and the degassing unit is usually closed. During the sedimentation / decantation phase, it usually operates as a continuous flow through the settler; i.e. overall, it is usually used in a semi-continuous manner.

[0059] Biomass separator unit, such as biomass settling tank, is typically a system with tilted internals (tilted internals) (such as tilted plates), which are configured to enhance the settling capacity of solid particles in aqueous fluids (such as suspensions or sludge). The tilted internals can be flat or corrugated, for example, by tilted pipes or tilted plates. The tilted internals are usually placed at an angle of about 55 to about 60 °. They are usually placed at a distance of at least about 2 to about 10 cm from each other to enhance separation and avoid separator clogging. This tilted internal further promotes the separation of remaining biogas (if any) with liquid phase and solid phase.

[0060] The inclined internal members (4), preferably lamellae, of the biomass separator unit (3) are generally about 1 / 4 of the working volume of the biomass separator. 1 / 4 to approx. 2 / 3. Preferred 1 / 3 to about 1 / 2 occupies part of the working volume of the biomass separator unit (3). In the upper part or above the space occupied by the internals, an outlet for the effluent 'b' is usually provided. Below the internals, space is usually provided for concentrated sludge. There is usually a head space above the internals. Particularly good results are obtained using a system in which the inclined internals are in the form of sheets and are 1 / 2 to 1 / 3 of the working volume of the semi-continuous settling tank (3).

[0061] The suspension treated in the biomass separator is already well degassed in the degassing tank, allowing good settling. Due to the semi-continuous operation of the biomass separator unit (simultaneous sludge return, filling and decanting) and the subsequent lower flow rates, the area required for settling is much lower and therefore the space / area occupied by the internals can be relatively low, since it is usually sufficient if they effectively settle the solids (including biomass), thereby (a) continuously returning the concentrated sludge to the bioreactor, reducing the total solids concentration in the biomass separator, thereby allowing faster separation of solids due to the reduced solids gradient, and (b) forming an aqueous fluid (effluent from the separator) with a reduced biomass content and also leaving the system in a semi-continuous manner.

[0062] Considering further that for the same processing capacity, the total volume of the system can be considerably smaller, the volume saving by separating the internal components (eg, sheets) can be more than 50%, for example, about 75%.

[0063] Next reference Figure 1-4 The method and system according to the invention are further described.

[0064] The bioreactor (1) comprises an inlet for an aqueous fluid, preferably at the top of the bioreactor. The inlet is usually fluidly connected to a buffer tank (5) via a conduit (c). The buffer tank buffers the rate fluctuations of the fluid to be treated (usually a waste stream). It also allows for temporary storage of the fluid (influent) fed into the system before the next bioreactor feed cycle begins (as will be further described below). Typically, the buffer tank (95) contains an agitator, such as a stirrer, to keep the contents relatively uniform (e.g., suspended solids). It may also include a device for adding additives, such as microbial nutrients or additives (acid / base / buffer) to adjust pH.

[0065] The bioreactor (1) has an outlet for biogas (d), arranged in the head space of the bioreactor. The bioreactor does need to have separator internals for degassing. It is usually a stirred bioreactor, so it contains one or more stirrers, although other types of stirring devices can be provided. It also has an inlet for recycling concentrated sludge from the biomass separator, which is connected to the sludge outlet fluid in the biomass separator unit (3) via a pipeline (a). The inlet or outlet is usually arranged in the lower part of the bioreactor or biomass separator unit. The bioreactor (1), pipeline (a) or biomass separator (3) usually has a drain pipe ( Figure 1 and Figure 3 Preferably, the drain is arranged in the bioreactor, usually at or near its bottom. Furthermore, the bioreactor (1) comprises an outlet for the aqueous suspension (comprising the treated aqueous fluid and the biomass), which outlet is connected to the inlet fluid of the degassing unit (2) via a conduit (e). In one embodiment, the outlet for the aqueous suspension of the bioreactor is located in the lower part of the reactor. This allows at least substantially complete removal from the bioreactor into the degassing unit. Figure 1 and Figure 2 Such an embodiment is shown in . Figure 1 and Figure 2 Also shown is an embodiment in which the bioreactor unit (1) and the degassing unit (2) are spaced apart.

[0066] In another embodiment (e.g., Figure 3 and Figure 4(as shown), the outlet is located in the middle or higher part of the bioreactor, above the inlet of the aqueous suspension into the degassing unit. This allows the suspension to be removed from the bioreactor (1) and fed to the degassing unit (2) at least partially by gravity flow. The degassing unit is typically a stirred degassing unit. It does not require separator internals. An outlet for biogas (f) is provided in the head space of the degassing unit (2). A pipe (g) connects the outlet for the degassed aqueous suspension provided in the degassing unit (2) with the inlet for the degassed aqueous suspension to enter the biomass separator (3). The outlet of the degassing unit (2) is typically provided at or near the bottom of the degassing unit to allow substantially complete removal of the degassed suspension. The position of the inlet into the biomass separator unit depends on the type of separator. Particularly preferred is a biomass separator having separator internals (4) in the middle or upper part of the biomass separator, wherein the inlet for the degassed suspension is arranged at or below the lowest level of the separator internals, and wherein the outlet (b) for the effluent is located at a higher height, preferably at, near or above the highest level of the separator internals, thereby providing an upward liquid flow through the internals during at least a part of the separation phase, while there is a net downward movement of solids, such as biomass, and achieving a reduced solids content at the outlet (b) of the effluent. This design allows semi-continuous use of the biomass separator, during which the feeding of the aqueous suspension and the removal of (b) effluent and optionally (a) sludge from the biomass separator are carried out. Optionally, a biogas outlet (h) is provided in the head space of the biomass separator, typically at or near the top plate (above the effluent outlet (b)).

[0067] like Figure 3 and Figure 4 As shown, the bioreactor unit (1) and the degassing unit (2) can be integrated in a single housing. Therefore, they can form part of a single tank / container. Nevertheless, the bioreactor unit and the degassing unit remain separate compartments, thereby avoiding accidental mixing of the contents. Therefore, the aqueous suspension in the bioreactor unit and the aqueous suspension in the degassing unit are separated by a partition (i) that is impermeable to the aqueous fluid. However, the top space can be shared. This design allows the footprint of the system to be further reduced. From a horizontal point of view, the bioreactor usually forms the inner part of a single housing, while the degassing unit forms the outer part (essentially surrounding the bioreactor). The ratio behind this is that the internal volume of the degassing unit needs to be smaller than that of the bioreactor. Having a larger volume inside reduces the strength requirements of the materials used in the system. If the bioreactor is located outside, when the bioreactor is full and the degassing unit is empty, the force applied to the partition will be much greater, and if the partition is not strong enough, it will bring the risk of collapse.

[0068] Particularly preferred is an integrated at least substantially cylindrical container, in which the bioreactor (1) forms an inner at least substantially cylindrical container and in which the bioreactor is at least substantially surrounded by the degassing unit (2).

[0069] As mentioned above, the method according to the invention comprises at least four stages. In the following, when it is mentioned that the pipeline is closed, this may mean that the valve has been closed to prevent flow, or it may mean that the pump is not pumping. In other words, this means that there is no flow in the pipeline.

[0070] During the (A) bioreactor unit batch feeding phase, the aqueous fluid to be treated is fed into the bioreactor unit. The aqueous fluid is usually fed into the bioreactor (1) via a pipeline (c) fluidly connected to the outlet of the buffer tank (5). The fluid can be fed at any position in the reactor. During this phase, the pipeline (e) between the bioreactor (1) and the degassing unit (2) is usually closed to avoid sending the new incoming fluid to be treated into the degassing unit, but in principle it can be open. It should be noted that microorganisms can already transform biodegradable substances while feeding (batch feeding). After the first cycle, the contents of the degassing unit are also degassed at this stage. Therefore, the pipeline (g) between the degassing unit and the biomass separator (3) is also usually closed. Usually, the recycling of the sludge (a) from the previous one has been completed. Therefore, the pipeline (a) can also be closed. Usually, the removal of the effluent (b) from the previous one has been completed. Therefore, the pipeline (b) can also be closed.

[0071] The batch reaction phase (B) is followed by the bioreactor batch feeding phase (A). In this phase, generally no feed enters the bioreactor and no treated suspension is taken out, i.e., pipes (c) and (e) are closed. Degassing is allowed to continue in the degassing unit (2) (after the first start-up-cycle). Therefore, pipe (g) is also generally still closed, although if a sufficient degree of degassing has been carried out before the microbial treatment in the bioreactor (1) is fully carried out, in principle, the degassed suspension can be started to be taken from the degassing unit (2) to the biomass separator unit (3). At this stage, the separator generally remains stationary. The volume of the aqueous suspension in the bioreactor (1) (wherein the microbial treatment of the aqueous fluid is carried out in batches (by cycle)) is generally the same as or larger than the volume of the aqueous suspension degassed in the degassing unit (2) by batches (by cycle). Generally, the volume in the bioreactor (1) is less than 10 times the volume in the degassing unit (2). Preferably, the volume in the bioreactor (1) is about 1.5 to about 4 times the volume in the degassing unit, more preferably about 2 to about 3 times the volume in the degassing unit. A relatively large volume bioreactor is advantageous in reducing the footprint of the apparatus used.

[0072] During the semi-continuous biomass separator unit feeding phase (C) following phase (B), at least after the start-up cycle, the microbial treatment in the bioreactor (1) will generally continue (although the biogas production rate will decrease during this phase). During this phase, the degassed contents of the degassing unit are pumped into the biomass separator via conduit (g). The degassing unit is therefore generally at least substantially empty; typically 90-100% of the degassed suspension is fed to the biomass separator (3). As the separator fills, separation will occur into a concentrated sludge (a) and an aqueous fluid with a reduced solids content; both the concentrated sludge (a) and the aqueous fluid (b) can be taken out of the separator while the separator continues to be fed. At the beginning of this phase, the biomass separator unit is generally substantially empty. At least, the liquid level will be below the outlet (b) for the clarified aqueous liquid. The outlet of the clarified aqueous liquid is usually higher than the outlet of the concentrated sludge (the outlet of the sludge is usually located at or close to the bottom), usually higher than the inlet level of the deaerated aqueous suspension, and usually at or above the upper level of the separator internals. Therefore, at this stage, the separator unit is usually continuously fed to fill the separator unit to a liquid level at the height of the clarified aqueous liquid outlet, and then the sludge (a) and the fluid (b, effluent) are removed from the separator. Therefore, at this stage, the feeding, the separation and removal of the sludge (a) and the clarified aqueous liquid (b) are advantageously carried out semi-continuously (i.e., an initial stage with feeding but no removal of clarified liquid, followed by a continuous stage in which the feeding and removal are carried out continuously), although in principle it is also possible to feed the suspension to be separated and remove the sludge (a) and the clarified aqueous fluid (b) intermittently. The removal of the clarified liquid (b) can usually be simply accomplished by gravity overflow without the need for a pump. The recycling of the concentrated sludge (a) to the bioreactor unit usually requires the use of a pump.

[0073] Solid particles other than biomass, which may be present in the aqueous fluid, such as mineral particles, will also preferentially enter the thickened sludge, so that the clarified aqueous fluid has not only a reduced biomass content, but also a reduced total solids content.

[0074] Preferably, the concentrated sludge (a) rich in biomass is recycled to the bioreactor unit and the clarified aqueous fluid (b) with reduced biomass content is taken out of the biomass separator unit and discarded as effluent or subjected to further downstream treatment. The sludge (a) is returned to the bioreactor (1) via the pipeline (a). The recycling of the sludge (a) and the removal of the clarified aqueous fluid (b) are usually carried out during the biomass separator unit feed phase (C), but can also be carried out after it but before the start of the next said phase (E) or (A). According to experience, the clarified aqueous fluid (b) will account for 20-45 vol%, in particular 25-40 vol%, more particularly 30-35 vol% of the degassed suspension separated in the biomass separator, while the concentrated sludge (a) will form the remainder. Thus, when recycled, the biomass-rich sludge (a) will represent 55-80 vol%, in particular 60-75 vol%, more in particular 65-70 vol% of the total amount of said sludge (a) plus the aqueous fluid with reduced biomass content (b).

[0075] If excess biomass is formed, a portion of the sludge can be discarded. An aqueous fluid (b) is withdrawn from the system (effluent) and can be discarded as is, or subjected to further downstream processing (not shown). Suitable downstream processing processes are generally known in the art.

[0076] Typically, substantially all of the degassed contents of the degassing unit are transferred to the biomass separator unit. A small amount of liquid level may remain at the bottom, for example about 10-25 cm. When the degassing unit is to be completely emptied, it is usually necessary to use a liner at the bottom of the degassing unit. Once all of the degassed suspension has been fed into the separation unit (2) in this cycle, the pipe (g) can be closed. Preferably, the contents are continued to be removed from the biomass separator until the separator is at least substantially emptied. At this stage ('D', e.g. Figure 2 D and 4E), the sludge (b) is usually recirculated to the biomass separator via the pipe (a). When the biomass separator stops feeding, or shortly after the start of this phase, the effluent is usually stopped. In principle, the degassing unit (2) can be filled with the contents of the bioreactor (2) via the pipe (e) at this stage.

[0077] However, the filling of the degassing unit usually starts in a separate stage (E), or at least continues in this stage, e.g. Figure 2 E and Figure 4 As shown in E.

[0078] Phase (E) is the degassing unit feed phase, in which an aqueous suspension comprising an aqueous fluid treated with microorganisms and biomass is withdrawn from the bioreactor unit and fed batchwise into the degassing unit. Thus, pipeline (e) is open, while the other pipeline can remain closed.

[0079] Once the bioreactor (1) has been sufficiently emptied by feeding its contents into the degassing unit (2), the next cycle can begin: the bioreactor is again fed with the aqueous fluid to be treated in the bioreactor, etc., followed by stages (B), (C), (D) and (E).

[0080] The method according to the present invention is particularly conducive to anaerobic treatment, wherein biogas is formed by biodegradable organic matter. Usually, anaerobic conditions are maintained not only in bioreactor but also in degassing unit, and biomass separator unit can be operated under anaerobic conditions, but does not need to be maintained. For example, it can be opened regularly during the use of bioreactor and / or degassing unit to maintain or clean, such as in (A) bioreactor feed stage, (B) batch reaction stage and / or (E) degassing unit feed stage. The pressure in the head space can be atmospheric pressure (0 bar gauge pressure (barg)). However, preferably, anaerobic conditions are maintained while in the head space of bioreactor and degassing unit, there is (little) superatmospheric pressure, such as up to 100 mbar gauge pressure, particularly 5-70 mbar gauge pressure, ideally under the pressure of 0-70 mbar gauge pressure.

[0081] The design of the device according to the invention (used in the method) is also advantageous in that the headspace of the bioreactor (1) (i.e. the upper part of the reactor interior above the fluid phase, in which the biogas is present) is connected to the headspace of the degassing unit via a channel. Thus, a gas-tight system is provided, thereby eliminating the significant risk of odor and biogas emissions, which is a frequent problem, especially in anaerobic contact reactors. Optionally, a biogas connection to the separator (3) is also provided.

[0082] The method according to the invention allows convenient real-time system monitoring, optimization and stage automation based on continuous biogas production curves (biogas production rate as a function of time). By tracking the biogas production in each curve, system capacity can be monitored in real time.

[0083] In the method or the device according to the invention, the system load and the duration of the reaction / settling phases can be adjusted and optimized based on a "standard" biogas curve, i.e. a benchmark / reference biogas curve defined by the operator for the specific process in question. The biogas curve allows to link the feed and sequence to the biogas production, facilitating effective control and avoiding any potential overloading of the system. In the known continuously operated processes, it is not possible to have a biogas curve that can be used adequately for this purpose. This use of the biogas curve is relevant to continuously operated processes such as treatment in anaerobic membrane reactors (AnMBR), treatment in continuous stirred tank reactors with dissolved biogas flotation units (DBF) or in processes such as in the early 1990s. A major advantage of the process described in Wat. Sci Tech. Vol. 24, No. 8, 00 179-191 (1991) over the contact process. For example, Continuous processes such as those described above are particularly susceptible to TSS and / or FOG overload in the bioreactor or effluent. This is due to the fact that in continuously operated systems (e.g. The system described in the present invention lacks the targeted degradation of TSS and FOG. After all, in continuous processing, the fresh substrate (biodegradable material) of biomass is continuously supplied to biomass. Waste streams are usually relatively non-uniform streams, containing a variety of different degradable components in terms of chemical composition and / or physical state (dissolved / suspended, small particles / large particles). This usually means that relatively easily degradable feed components (such as digestible soluble / dissolved components) and difficult to degrade feed components (such as suspended solids, FOG) are continuously introduced into the bioreactor containing biomass, thereby continuously providing relatively easily degradable substrates for microorganisms (biomass). Therefore, in continuous operation, easily degradable substrates are usually abundant. Microorganisms usually prefer components that are easily degraded. Therefore, continuous operation is easy to accumulate relatively difficult to degrade components (such as suspended solids, FOG) until there are too many to make biomass float and cause the loss of undesirable or even unacceptable biomass and / or non-degradable organic matter through effluent. The present invention allows to produce a feast / famine scenario by batch operation in a bioreactor, the goal of which is to force the biomass to degrade fats and solids before feeding the biomass again. This is combined in the present invention with appropriate degassing of the biomass to allow it to settle. Thus, by the measures described in the present disclosure, the inventors have in particular achieved an efficient way to implement the method according to the present invention, including efficient operation of the batch phase in the method, and efficient operation when treating aqueous fluids such as wastewater with relatively high contents of TSS and / or FOG. Thus, important biological performance advantages are achieved compared to essentially fully continuous methods. This can in particular be achieved by one or more of the following measures:

[0084] • Simultaneous reaction / settling phases - this allows for much longer settling time periods (typically at least about 2 times longer than conventional AnSBRs) without compromising the duration of the reaction phase, which is not achievable in conventional AnSBRs.

[0085] Simultaneous feed / withdrawal phases - The system can also achieve simultaneous feed and withdrawal (decantation) phases, reducing the number of phases required per cycle, which is not possible in conventional AnSBRs.

[0086] • Reduction in required inclined internals (lamellae) volume / area; it is generally feasible to reduce required lamellae volume / area by up to about 2 / 3 while maintaining essentially the same separation efficiency.

[0087] No pressurized internals are required in the degassing tank. This provides simplification, improved safety, easier construction and easier maintenance of inclined internals (e.g. lamellae) in the biomass separator in case of blockage.

[0088] Optimized biomass separation: Semi-continuous biomass separation in a separate unit after (batch degassing) allows longer decantation and sludge return times, which in turn allows for smaller pipe diameters and lower pumping requirements.

[0089] Reduced space usage - Although a batch degassing tank of at least 2 times the batch size is required, this new improvement has no height restriction; this means that the tank can be a thin and tall tank (preferably about 6-8m high), which takes up less space. In addition, the present invention achieves a compact configuration by integrating the batch degassing tank into the reaction tank, which will further optimize and reduce the space usage.

[0090] Extend degassing time without affecting cycle length.

[0091] As used herein, the term "or" is defined as "and / or" unless stated otherwise.

[0092] The terms "a" or "an", as used herein, are defined as "at least one", unless otherwise stated.

[0093] When referring to a noun (eg, compound, additive, etc.) in the singular, it is intended to include the plural.

[0094] The term "(at least) substantially" is generally used herein to indicate that it has the specified general property or function. When referring to a quantifiable characteristic, the term is particularly used to indicate at least 50% of the maximum value of the characteristic, more particularly more than 75%, even more particularly more than 90%. The term "substantially free" is generally used herein to indicate that the substance is not present (below the detection limit achievable using analytical techniques available on the effective filing date) or is present in an amount so low that it does not significantly affect the properties of the product that is substantially free of the substance. In fact, in terms of quantity, if the content of a substance is 0-1wt.%, particularly 0-0.5wt.%, more particularly 0-0.1wt.%, then the product is generally considered to be substantially free of the substance.

[0095] In the context of the present application, the term "about" generally refers to a deviation of 15% or less, particularly a deviation of 10% or less, more particularly a deviation of 5% or less from a given value.

[0096] As used herein, "biodegradable organic matter" is organic matter that can be converted by biomass in a reactor, typically under substantially anaerobic conditions, particularly to biomass or methane.

[0097] The term "fluid" is used herein for liquids and mixtures of liquids with at least one other phase, such as suspensions, which flow without the application of external pressure (other than gravity).

[0098] As used herein, "organic matter" is any organic matter that is chemically oxidizable, as determined by the Chemical Oxygen Demand (COD) test as described in ISO 6060: 1989. The amount of organic matter is usually expressed in g COD, which is the grams of oxygen consumed to oxidize the organic matter.

[0099] The skilled person will be familiar with terms such as 'above', 'below', 'in', 'at the bottom', 'near the bottom', 'at the top' and 'near the top' etc. Generally, these are to be read relative to one another and based on common general knowledge, the information disclosed herein and citations, and the details of the units of the apparatus (e.g. bioreactors, individual containers or volumes of material contained in a bioreactor or part), the skilled person will be able to put them into practice.

[0100] As a rule of thumb, unless the context indicates otherwise, 'near' a reference point (e.g. 'bottom' or 'top') generally means 'at a relative height of at most + / - 20% from the reference point', particularly 'at a relative height of at most + / - 15% from the reference point', more particularly 'at a relative height of at most + / - 10% from the reference point'. The relative height is the distance from the bottom divided by the total height of the unit (the height difference between the bottom and the top).

[0101] As a rule of thumb, unless otherwise indicated by the context, the 'upper' portion generally refers to the upper 1 / 2 of the unit, particularly the upper 1 / 3 of the unit, and the 'lower' portion generally refers to the lower 1 / 2 of the unit and particularly the lower 1 / 3 of the unit. When the middle portion is mentioned, this particularly refers to the middle 1 / 3 of the unit (from the bottom 1 / 3 to the top 1 / 3).

[0102] For the purpose of clarity and concise description, features are described herein as part of the same or separate embodiments, however, it should be understood that the scope of the invention may include embodiments having a combination of all or some of the features described. Unspecifically defined terms used herein are as defined in WO 2013 / 139823 or WO 2019 / 115034, or - if not defined therein - are used in accordance with common general knowledge.

[0103] The invention will now be illustrated by the following examples.

[0104] Example 1: Case study, comparison with WO 2019 / 115034

[0105] A case study was performed to illustrate in a quantifiable way the advantages of the method according to the present invention compared to WO 2019 / 115034.

[0106] The case study is based on the following feed stream and composition.

[0107]

[0108] Text description:

[0109] COD = Chemical Oxygen Demand

[0110] VFA-COD = COD formed from volatile fatty acids

[0111] TSS = Total Suspended Solids

[0112] VSS = Volatile Suspended Solids

[0113] The following parameter requirements and savings were calculated

[0114]

[0115] Example 2: Industrial scale validation, comparison with WO 2019 / 115034

[0116] First, the wastewater from wineries and breweries was treated for about 60 days according to WO 2019 / 115034. Thereafter, it was changed to the method according to the present invention.

[0117] The feed and system conditions are as follows:

[0118]

[0119] It was found that after changing to the method of the present invention, the TCOD, SCOD (soluble COD), VLR (volume loading rate, expressed as kg COD / m 3 The performance was maintained essentially the same in terms of SRT (solids retention time, expressed in days) and MLSS (mixed liquor suspended solids, expressed in g / L). The performance was maintained as shown in the following table, taking into account that for the new configuration, both the degassing tank and the semi-continuous settler were operated at the operating parameters, cycle times and flow rates required for full scale.

[0120]

[0121] Therefore, it is concluded that the method according to the present invention is a good alternative to the method of WO 2019 / 115034. The biomass separator meets the settling velocity requirements. In addition, the process cycle can be reduced. It has high performance at a VLR of at least 5g COD / L day. Good SCOD removal and TCOD removal efficiency are achieved.

Claims

1. A method for treating an aqueous fluid containing biodegradable organic matter in an apparatus comprising - A bioreactor unit (1), wherein: The aqueous fluid is treated with anaerobic microorganisms, thereby producing biogas from the organic matter, - a degassing unit (2), in which an aqueous suspension is taken out of the bioreactor, said suspension comprising aqueous liquid, biogas and biomass being subjected to batch degassing, and - a semi-continuously operated biomass separator unit (3), wherein the degassed suspension withdrawn from the degassed unit is separated into (a) a biomass-rich sludge and (b) an aqueous fluid having a reduced biomass content compared to the degassed suspension fed to the biomass separator unit (3), The method comprises - a bioreactor unit fed-batch phase, wherein the aqueous fluid to be treated is fed to the bioreactor unit; - a batch reaction stage, in which the aqueous fluid is subjected to a microbiological treatment under anaerobic conditions and biogas is produced in the bioreactor unit; - a semi-continuous biomass separator unit feeding phase, wherein a degassed aqueous suspension is withdrawn from the batch degassing unit and fed into the biomass separator unit, the semi-continuous feeding phase comprising an initial phase in which no aqueous fluid with a reduced biomass content is withdrawn, followed by a continuous phase in which the feeding and withdrawal are carried out continuously; - A degassing unit feed phase, wherein an aqueous suspension comprising a microbial treated aqueous fluid and biomass is withdrawn from the bioreactor unit and fed batchwise into the degassing unit.

2. The method according to claim 1, wherein: The method comprises a plurality of cycles, wherein after the start cycle, one or more subsequent processing cycles are performed, and in the one or more subsequent cycles - carrying out a batch feed phase (A) of the bioreactor unit, wherein the aqueous fluid to be treated is fed into the bioreactor unit, while the treatment of the aqueous fluid already present in the bioreactor unit continues, degassing the aqueous suspension fed into the degassing unit in a previous phase or cycle while using mixing; - the batch reaction phase (B) is then carried out, wherein the batches of aqueous fluid are subjected to microbial treatment in the bioreactor unit (1) to produce biogas, and the aqueous suspension is degassed in the degassing unit (2); - a biomass separator unit operation phase (C) is then carried out, in which the degassed aqueous suspension is continuously withdrawn from the degassing unit (2) and fed to the biomass separator unit (3) until the biomass separator unit is filled to a height level at which there is an outlet for the clarified aqueous fluid with a reduced biomass content (b), and from then on during this phase the aqueous fluid with a reduced biomass content is continuously removed from the biomass separator unit and the biomass-rich sludge (a) is continuously returned to the bioreactor unit, while the microbiological treatment of the aqueous fluid in the bioreactor unit is continued; - followed by a further sludge return phase (D) in which the feeding of the deaerated suspension from the deaeration unit to the biomass separator unit has been completed, the removal of the aqueous fluid with reduced biomass content from the biomass separator unit has been stopped and the return of the biomass-rich sludge to the bioreactor has been continued, while the microbial treatment in the bioreactor unit continues; - A batch degassing tank filling phase (E) is then carried out, wherein, once a required volume of aqueous fluid with reduced biomass content has been withdrawn from the biomass separator unit during the previous phase, said required volume being equal to the volume fed to the bioreactor during the batch feeding phase (A), the remaining biomass-rich sludge is returned to the bioreactor in this phase, while the microbial treatment in the bioreactor unit continues.

3. The method according to claim 2, wherein: The aqueous fluid having a reduced biomass content is removed from the biomass separator unit by gravity overflow.

4. The method according to claim 2, wherein: In the batch reaction stage (B), the aqueous suspension in the degassing unit (2) is degassed while using mixing in the degassing unit.

5. The method according to any one of claims 1 to 4, wherein: The biomass-rich concentrated sludge (a) is recycled to the bioreactor unit and the clarified aqueous fluid (b) having a reduced biomass content is removed from the biomass separator unit and either discarded as effluent or subjected to further downstream processing.

6. The method according to claim 2, 3 or 4, wherein: During or after said biomass separator unit operation stage (C), but before the start of the next said stage (E) or (A), the recycling of said sludge (a) and the removal of clarified aqueous fluid (b) are carried out.

7. The method according to any one of claims 1 to 4, wherein: The biomass separator unit has inclined internal components adapted to enhance the settling properties of the biomass.

8. The method according to claim 7, wherein: The inclined inner member is a thin sheet.

9. The method according to claim 7, wherein: The inclined internal member defines a volume between 1 / 2 and 1 / 3 of the working volume of the biomass separator unit.

10. The method according to any one of claims 1 to 4, wherein: The volume of the aqueous fluid subjected to the microbial treatment in the bioreactor unit in batch is 2 to 3 times the volume of the aqueous suspension degassed in the batch degassing unit.

11. The method according to any one of claims 1 to 4, wherein: The microbial treatment in the bioreactor unit is anaerobic, and wherein anaerobic conditions are maintained in the bioreactor unit and the degassing unit.

12. The method according to any one of claims 1 to 4, wherein: The aqueous fluid is a fluid waste having a total chemical oxygen demand in the range of 1.0-50 g / L.

13. The method according to claim 12, wherein: The total chemical oxygen demand is in the range of 5-50 g / L.

14. The method according to claim 13, wherein: The total chemical oxygen demand is in the range of 8-50 g / L.

15. The method according to claim 14, wherein: The total chemical oxygen demand is in the range of 8-30 g / L.

16. The method according to any one of claims 1 to 4, wherein: The aqueous fluid is a fluid waste having a total suspended solids content of 0.5 g / L or more.

17. The method according to claim 16, wherein: The aqueous fluid is a fluid waste having a total suspended solids content of 1.0-30 g / L.

18. The method according to any one of claims 1 to 4, wherein: The aqueous fluid is a fluid waste having a total suspended solids content of 0-20 g / L.

19. The method according to any one of claims 1 to 4, wherein: The aqueous fluid is a fluid waste having a total fat, oil and / or grease content in the range of 0-4 g / L.

20. The method according to any one of claims 1 to 4, wherein: The aqueous fluid is a fluid waste having a total fat, oil and / or grease content of 50 mg / L or more.

21. The method according to claim 20, wherein: The total fat, oil and / or grease content of the fluid waste is in the range of 0.1-2 g / L.

22. A sequencing batch reaction system operable in simultaneous stages, the system comprising a bioreactor unit, wherein: an agitator is present for agitating the aqueous suspension in the bioreactor unit to produce biogas, the apparatus further comprising a batch degassing unit, wherein an agitator is present for agitating the aqueous suspension and the agitator is configured to degas the aqueous suspension that has been fed from the bioreactor unit into the batch degassing unit, the system further comprising a biomass semi-continuous separator unit, the biomass semi-continuous separator unit being configured to separate the degassed aqueous suspension from the degassing unit into a sludge rich in biomass compared to the degassed suspension and an aqueous effluent having a reduced biomass content, Among them, the separate biomass semi-continuous separator unit includes a space for containing the treated aqueous suspension from the degassing chamber, said space comprising a liquid-solid separator unit; and further comprising an inlet for said degassing aqueous suspension, said inlet being connected by a closable conduit to an outlet for the treated aqueous suspension from said degassing chamber; an outlet for removing said sludge from said separator unit and a separate outlet for removing said effluent from said separator unit by means of a closable conduit, wherein the bioreactor unit and the degassing unit have a joint or separate headspace for biogas, one or more of the headspaces comprising an outlet for biogas, The system further comprises an inlet for a fluid aqueous waste stream to enter the bioreactor unit, means for feeding an aqueous suspension from the bioreactor unit to the degassing unit.

23. The system of claim 22, wherein: The liquid-solid separator has an inclined internal member adapted to enhance the settling of biomass in an aqueous fluid.

24. The system of claim 22 or 23, the internal volume of the bioreactor unit being 2 to 10 times the internal volume of the batch degassing unit.

25. The system of claim 22 or 23, wherein the internal volume of the bioreactor unit is 3-6 times the internal volume of the batch degassing unit.

26. The system of claim 22 or 23, wherein the internal volume of the bioreactor unit is 3-5 times the internal volume of the batch degassing unit.

27. The system of claim 22 or 23, wherein: The bioreactor unit and the degassing unit are separate parts of a single piece of equipment, wherein the bioreactor unit is located in a central part of the equipment and is substantially surrounded by the degassing unit.

28. The system of claim 27, wherein: The single piece of equipment is a single container.

29. The system of claim 28, wherein: The bioreactor unit and the degassing unit are parts of the single container and both units share the same headspace.

30. The system of claim 27, wherein: The bioreactor unit and the degassing unit are separated by an intermediate wall and provided with a channel configured to transfer the aqueous suspension from the bioreactor unit to the degassing unit by gravity flow.

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