Integrated thermal hydrolysis and vacuum digestion for treating fluids using biochemical processes

Abstract

Systems and methods for treating a fluid comprising a particulate portion and a soluble portion include feeding the fluid to a hydrothermal treatment device and subjecting the fluid to heating to a temperature of 121 DEG C or higher to obtain a treated fluid, followed by feeding the hydrothermally treated fluid to a vacuum integrated reactor, wherein at least the particulate portion is subjected to fermentation or digestion, during which the fluid in the vacuum integrated reactor is subjected to vacuum pressure, and at least a portion of the soluble portion of the fluid as condensate is collected from the vacuum integrated reactor, and thereby the remaining portion of the fluid is thickened, and recovering the thickened fluid from the vacuum integrated reactor. Vacuum may also be applied upstream or downstream of the non-vacuum integrated reactor and separated from the non-vacuum integrated reactor.

Description

[0001] This application is a non-provisional application of U.S. Provisional Application No. 63 / 343,903 filed on May 19, 2022, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0002] Global climate change and energy crisis due to the burning of fossil fuels have increased interest in bio-renewable energy. As a result, wastewater treatment plants (WWTPs) are turning to water resource recovery facilities (WRRFs) with the goal of wastewater treatment and recovery of value-added products such as volatile fatty acids and biomethane from sludge generated on-site. In addition, in recent years, due to economic conditions such as increasing oil prices and negative environmental impacts, government initiatives in many countries have focused on increasing the use of various renewable energy sources, including solar, wind, biomass, hydropower, tidal, and energy from waste.

[0003] One of the leading sludge management technologies is anaerobic digestion. Anaerobic digestion (AD) is a promising technology that can convert organic waste into volatile fatty acids or methane or both in two different stages: acidification (first stage) and methanogenesis (second stage). Organic waste is converted into volatile fatty acids via acidogenic and acetogenic microorganisms in the first stage. In addition, hydrogen and volatile fatty acids are converted into methane via methanogenesis in the second stage. Compared with other waste treatment technologies, AD has many benefits, such as solid reduction, reduced greenhouse gas emissions, odor reduction and increased non-market benefits.

[0004] The long hydraulic retention time (HRT) of the soluble part of the fluid and the low methane and VFA production are some challenges associated with anaerobic digestion (AD). The hydrolysis step is the rate-limiting step of AD for complex organic fluids or substrates, while methanogenesis is the rate-limiting step for fluids or substrates that are easily biodegradable. Different pretreatment techniques (including mechanical, chemical, biological and thermal) have been applied in an attempt to promote the hydrolysis step. Hydrothermal treatment (HTP) refers to heating the biomass to above the autoclave temperature (121°C) for a fixed time before AD. The mechanism of HTP is to lyse the cell membrane and subsequently release the intracellular material, which causes the organic compounds to dissolve. Researchers have studied the effects of HTP on both AD and fermentation of municipal sludge using a wide temperature range (from 50°C to 275°C). Summary of the invention

[0005] What remains needed is a method and system to improve the efficiency of anaerobic digestion processes (e.g., in terms of increasing the yield and retention time of value-added products (such as volatile fatty acids and biomethane)) in treating fluids such as sludge (e.g., in wastewater treatment facilities).

[0006] This object and other objects are achieved by the novel systems and methods described herein.

[0007] The disclosed systems and methods address the recalcitrant nature of organic wastes, such as waste activated sludge, for conventional anaerobic digestion. The addition of a hydrothermal pretreatment (HTP) reduces the likelihood of mixing problems in a vacuum reactor due to sludge thickening. Typically, mixing of a digester requires a large amount of energy due to the high viscosity of the sludge. HTP reduces the viscosity of the sludge and facilitates easier operation and less maintenance. Additionally, due to the ability to operate a digester with a more concentrated feed (due to reduced viscosity), a smaller AD volume will be required.

[0008] The combination of HTP and vacuum digestion helps to overcome the respective limitations of each process, because vacuum digestion is limited by viscosity, and heat treatment is limited by ammonia (ammonia produced during HTP has an inhibitory effect on AD). The application overcomes these limitations by combining their respective advantages. Heat treatment will reduce viscosity, thereby eliminating the bottleneck of vacuum digestion, and vacuum digestion will reduce ammonia content (by vacuum stripping under boiling), which will eliminate the bottleneck of heat treatment. Other synergistic effects are also expected: for example, using a nearly perfect biomass retention process (vacuum extraction / evaporation) allows selection of microbial ecology specifically for the less digestible components in the heat-treated feed. Like this, the less biodegradable components present in the feed or produced by HTP can be effectively transformed by a dedicated organism. In addition, the liquid residue produced by the integrated process is not affected by the presence of non-biodegradable total nitrogen, because the latter is retained in the cake and further digested by a dedicated microbial community.

[0009] The disclosed system and method are intended to minimize the space requirement for anaerobic digesters, while enhancing the generation of resources such as VFA and transferring this carbon source to other processes in wastewater treatment facilities. Typically, the floor space of AD tanks is very large (depending on the production capacity of the plant). The hydraulic retention time and load rate of AD determine the volume of the digester that needs to be designed and built. With the population growth in urban areas, most factories need to increase their digestion capacity by loading more organic matter into the digester. However, conveying a higher load to the digester means operating the digester with a lower HRT. In many countries, the biosolids produced by the lower HRT do not meet the biosolids standards, thereby forcing utilities to build new digesters to handle higher loads. The novel combination of hydrothermal treatment and vacuum digestion technology described herein not only allows the digester to operate with a lower HRT by separating (decoupling, decoupling) the hydraulic retention time of the soluble part (the HRT of the soluble components of the processed fluid) from the residence time of the solid part of the processed fluid (the HRT of the solid components of the fluid, or SRT), but also enhances methane and / or hydrogen production. The high ammonia concentration and associated pH after the HTP results in high free ammonia concentration, causing inhibition of methanogenesis. This inhibition can be addressed by the disclosed systems and methods.

[0010] Thus, the subject matter herein includes a method for treating a fluid comprising a particulate fraction and a soluble fraction, the method comprising:

[0011] feeding the fluid to a hydrothermal treatment device and subjecting the fluid to heating to a temperature of 121° C. or higher to obtain a treated fluid;

[0012] subsequently feeding the hydrothermally treated fluid to a reactor, wherein at least the particulate portion undergoes fermentation or anaerobic digestion, wherein the treated fluid is subjected to vacuum pressure upstream of, during or downstream of the fermentation or anaerobic digestion in the process direction;

[0013] wherein if vacuum pressure is applied during fermentation or anaerobic digestion, the reactor is a vacuum integrated reactor, and the method comprises collecting at least a portion of the soluble portion of the fluid (including water and gas) as condensate from the vacuum integrated reactor and collecting residual gas, and thereby thickening the remainder of the fluid;

[0014] wherein if vacuum pressure is applied upstream or downstream of fermentation or anaerobic digestion, the method comprises collecting at least a portion of the soluble portion of the fluid (comprising water and gas) as condensate from the treated fluid or from the treated and fermented or digested fluid and collecting residual gas, and thereby thickening the remainder of the fluid; and

[0015] The thickened fluid is recovered.

[0016] Also described is a method for treating a wastewater fluid comprising biosolids, the method comprising:

[0017] feeding the wastewater fluid to a hydrothermal treatment unit and subjecting the fluid to heating to a temperature of 121° C. or greater to obtain a treated fluid;

[0018] subsequently feeding the treated fluid to a reactor wherein the wastewater fluid undergoes fermentation or anaerobic digestion, wherein the treated fluid is subjected to vacuum pressure upstream of, during, or downstream of the fermentation or anaerobic digestion in the process direction;

[0019] wherein if vacuum pressure is applied during fermentation or anaerobic digestion, the reactor is a vacuum integrated reactor, and the method includes collecting gases (including but not limited to ammonia) as condensate from the vacuum integrated reactor;

[0020] wherein if vacuum pressure is applied upstream or downstream of fermentation or anaerobic digestion, the method includes collecting gases (including but not limited to ammonia) as condensate from the treated fluid or the treated and fermented or digested fluid; and

[0021] Heat is extracted from the condensate and utilized to provide heating to the wastewater fluid in the hydrothermal treatment unit.

[0022] Still further described is a system for processing a fluid comprising a particulate fraction and a soluble fraction, the system comprising:

[0023] a hydrothermal treatment device configured to treat a fluid fed thereto by heating,

[0024] a reactor downstream of the hydrothermal treatment device in the process direction, the reactor being configured to receive the treated fluid from the hydrothermal treatment device, subjecting the treated fluid to fermentation or anaerobic digestion, wherein the reactor is selected from: a vacuum integrated reactor having a vacuum pump for applying a vacuum to the vacuum integrated reactor; and a reactor without a vacuum pump,

[0025] wherein if the reactor is a reactor without a vacuum pump, the system further comprises a second reactor or a pipeline (upstream of the reactor in the process direction or downstream of the reactor in the process direction) comprising a vacuum pump for applying a vacuum to the second reactor or the pipeline, and

[0026] wherein condensate is removed using a vacuum; and

[0027] A controller is configured to control the application of the vacuum and the removal of the condensate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of a system including both a hydrothermal treatment device and a vacuum integrated reactor in a system including a downstream anaerobic digester.

[0029] Figure 2 is a schematic diagram of a system including a hydrothermal treatment apparatus, a reactor, and a downstream vacuum integrated processing unit.

[0030] Figure 3 is a schematic diagram of a system including both a hydrothermal treatment device and a vacuum integrated reactor in a system including an upstream anaerobic digester.

[0031] Figure 4-7 A specific exemplary system employing both hydrothermal processing (HTP) (in this case utilizing heating obtained by means including heat recovery from condensate extracted from the digestion process) and vacuum digestion is shown.

[0032] Figure 8 Different soluble components such as VFA, soluble carbohydrates and soluble protein concentrations of the hydrothermally treated and original untreated samples are shown.

[0033] Fig. 9 The percentage reduction of TSS and VSS due to the hydrothermal treatment is shown.

[0034] Fig.10 Particle size distribution (PSD) of original and hydrothermally treated (HTP) samples are shown.

[0035] Fig.11 Shown is the time course of chemical oxygen demand (COD) dissolution in conventional and vacuum fermentation reactors fed with HTP treated sludge.

[0036] Fig.12 The COD dissolution of sludge in two reactors (vacuum and conventional) is shown as a function of time.

[0037] Fig.13The average COD dissolved for four systems (conventional fermentation, HTP-treated sludge with conventional fermentation, vacuum fermentation, and HTP-treated sludge with vacuum fermentation) are shown.

[0038] Fig.14 Shown are the changes in VFA production over time for samples treated in conventional and vacuum integrated reactors for fermentate, condensate and total fermentate+condensate.

[0039] Fig.15 and 16 Specific denitrification rate (SDR) and biomass yield for all carbon sources are shown.

[0040] Fig.17 and 18 Cumulative methane production output over time for the four systems is shown.

[0041] Fig.19 and 20 Methane production rates are shown for HTP treated and original untreated feeds. DETAILED DESCRIPTION

[0042] A system and method comprising a hydrothermal treatment device and vacuum integrated biological and non-biological reactors (e.g., fermentation tanks) are described herein. In one aspect, the present disclosure provides a system and method for processing a fluid comprising a granular portion and a soluble portion. The system and method may include utilizing microorganisms to carry out biochemical conversion (e.g., for fermentation) of solids in the granular portion of the fluid, while subjecting the fluid to vacuum pressure, and evaporating at least a portion of the soluble portion of the fluid, and thus thickening the remainder of the fluid, which remainder may be left in the vacuum integrated reactor for continued processing. The system and method are used to support the system and method for processing fluids using fermentation and / or anaerobic digestion (AD).

[0043] AD is a multi-step biochemical process in which organic waste materials are decomposed by facultative and anaerobic microorganisms in an oxygen-free environment, where the basic steps of anaerobic digestion are hydrolysis, acidogenesis, acetogenesis, and methanogenesis.

[0044] In the first step of hydrolysis, hydrolytic bacteria degrade complex organic polymers (such as proteins, carbohydrates and lipids) into soluble monomers. In waste activated sludge (WAS), most of the organic compounds are surrounded by a polymer network formed by extracellular polymeric substances (EPS). EPS is a highly hydrated structure, which is of great significance in making sludge bioflocculation, sedimentation and dewatering. EPS in WAS is mainly attributed to proteins and carbohydrates, which need to be cracked so that the intracellular contents can be used for microorganisms.

[0045] The second step is acidogenesis, such as fermentation, in which the products of hydrolysis are further degraded to form volatile fatty acids (VFA) (such as acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, etc.), ammonia, hydrogen sulfide, carbon dioxide and other byproducts. In the present disclosure, a vacuum integrated reactor is used for this step, which also results in the dissolution of organic matter.

[0046] The next step, acetogenesis, involves acetogenic bacteria, which convert organic acids into acetic acid, hydrogen, and carbon dioxide.

[0047] The final stage of anaerobic digestion is methanogenesis, where biomethane is produced by two groups of methanogenic organisms: acetoclastic methanogens, which degrade acetate into methane and carbon dioxide, and hydrogenophilic methanogens, which use hydrogen as an electron donor and carbon dioxide as an acceptor to produce methane. In addition, methanogenesis can be controlled to favor the formation of biohydrogen and / or bioethanol rather than biomethane.

[0048] Thus, anaerobic digestion treats and stabilizes sludge and recovers value-added products in the form of methane or hydrogen and volatile fatty acids (VFA) through fermentation. VFA recovered from fermented sludge can be used in a variety of applications, such as carbon source for on-site biological nutrient removal, biodegradable plastic production, and hydrogen production.

[0049] Systems and methods herein focus on the application and integration of vacuum pumps (to extract water and gas from sludge streams) with existing bioprocesses (such as fermentation or digestion) for solids treatment. Vacuum is integrated with bioprocess applications, where a pump is connected to the headspace of a bioprocess container, or vacuum can be applied in an independent container or stream that is hydraulically connected to a main bioprocess reactor. In one embodiment, a vacuum-integrated reactor, such as a fermenter or digestion tank, is fed with a vacuum pump associated therewith for applying vacuum to the vacuum-integrated reactor. In another embodiment, a reactor (without vacuum) is fed with a heat-pretreated fluid in an ex-situ method, and is fed separately to a vacuum-integrated sidestream treatment unit located upstream or downstream of the reactor. In these embodiments, the reactor can be, for example, a fermenter and / or an anaerobic digester. Fermenters and anaerobic digesters are well-known reactors in the art, and therefore operational differences are not discussed further herein.

[0050] Thus, hydrothermal processing (HTP) is utilized in the systems and methods described herein as a step preceding vacuum integrated digestion or fermentation in a vacuum integrated reactor in the process sequence. HTP lyses wastewater sludge, increases soluble chemical oxygen demand (SCOD), breaks down the cell walls of bacteria contained in the sludge (thereby releasing intracellular material), and reduces sludge viscosity.

[0051] The reactor (downstream of the HTP device in the process direction) is used to separate high-quality condensates containing volatile substances (such as VFA and ammonia) and concentrate inert and particulate solids into smaller volumes. The reactor can be a fermentation reactor (fermenter) or a digestion reactor (digester), and as discussed below, a device for applying a vacuum therein (such as a vacuum pump) may be included, or a device for applying a vacuum may be omitted (vacuum integrated reactor). By integrating the HTP with the reactor, the production of valuable materials such as VFA can be enhanced, thereby increasing its recovery in the condensate. In addition, the tendency for mixing problems is reduced.

[0052] In previous systems, low methane and VFA production was partially attributed to the accumulation of inhibitory compounds such as ammonia and other nutrients during fermentation and AD. Removing these inhibitory compounds significantly improves the system. Applying a vacuum to the fermenter or digester allows the HRT to be separated from the solid retention time (SRT) via vacuum evaporation, resulting in a compact process that can be deployed in a wider range of facilities, including small municipalities and farms. In addition, this new approach can facilitate the separation and recovery of resources such as ammonia and VFA while enhancing sludge thickening.

[0053] The system and method herein combines HTP of organic waste with digestion or fermentation and vacuum.Slowly biodegradable fluid or substrate (for example, fluid or solid including difficult-to-degrade organic matter, such as waste activated sludge (TWAS) and / or food garbage of thickening) is through hydrothermal treatment (HTP).Slowly biodegradable fluid or substrate for HTP can be any difficult-to-degrade organic biodegradable compound, including but not limited to TWAS, excrement, source separation organic matter (SSO), garden garbage and cellulosic material and lignocellulosic material.The pH of slowly biodegradable substrate (such as sludge) can be acidic, neutral or alkaline, in the scope of for example 4-10.The solid content of the substrate that is difficult to biodegrade can be in the scope of for example 1% to 20%, such as 1% to 16%.

[0054] The HTP unit can be any suitable device having an inlet for a feed fluid or substrate, a means for applying heat to the feed fluid or substrate within the device (such as an external heat source or a heat exchanger that extracts heat from other materials within the system such as sludge exiting the HTP unit and / or condensate from a vacuum reactor), and an outlet for the treated fluid or substrate. Thus, the HTP unit can utilize heat recovered from condensed gases removed by the vacuum in the vacuum reactor to hydrothermally treat the feed fluid.

[0055] HTP can be carried out in a temperature range of, for example, 130 to 300 ° C (such as 150 to 220 ° C), for example, 5 to 300 minutes (such as 5 to 100 minutes and 10 to 30 minutes). HTP can be carried out under normal atmospheric pressure, but can also be carried out under a pressure of, for example, 1.1 to 10 bar (such as 2 to 8 bar or 2 to 6 bar). A set of preferred conditions for low retention time is, for example, 170 ° C, 6 bar, 30 minutes. The optimum temperature and retention time of HTP for methane production purposes are 160 to 180 ° C and 20 to 40 minutes, respectively.

[0056] Compared with original untreated fluid, HTP can increase the concentration of all soluble compounds (comprising soluble protein, volatile fatty acid and carbohydrate) in fluid. Accordingly, compared with original untreated fluid, the content of total suspended solids (TSS) and volatile suspended solids (VSS) can be reduced by HTP. For example, TSS reduction can be in the scope of for example 10% to about 40%, such as 15% to 35% or 20% to 35%, and VSS reduction can be in the scope of for example 10% to about 50%, such as 15% to 40% or 20% to 40%. In addition, compared with original untreated fluid, HTP can reduce the granularity of treated fluid. For example, when the d10 and d90 of original sample are respectively 27 μm and 187 μm, HTP can reduce these values ​​to 15 μm and 125 μm respectively, and the retention time that wherein increases in HTP reduces the granularity of treated sample. These changes in the treated fluid are significant because they enable higher value-added product recovery from the anaerobic digestion process, including higher VFA yields and higher methane and / or hydrogen recovery and production.

[0057] After leaving the HTP device, the treated fluid (such as treated sludge) can then be mixed with a faster biodegradable fluid or substrate (i.e., a fluid or substrate that biodegrades at a faster rate than the biodegradation rate of a slowly biodegradable fluid or substrate (such as primary sludge). Therefore, the other fluid biodegrades more quickly than the slowly biodegradable fluid because it can, for example, biodegrade more quickly by fermentation. If mixed, the ratio between the two types of fluids or substrates (slowly biodegradable: more quickly biodegradable) depends on the properties of the materials, but can be in the range of 100:0 to 25:75 (such as 75:25 to 25:75), preferably 50:50.

[0058] The treated material leaving the HTP unit (optionally in admixture with untreated fluid or substrate) is fed to a reactor (digester or fermenter). Preferably, to facilitate the fermentation and digestion processes in the reactor, the treated material is cooled to 75°C or less before entering the reactor. Cooling can be achieved using ambient conditions, or can be facilitated by heat removal in any suitable active cooling method and / or heat exchanger (in which case any extracted heat can be reused to heat additional fluid or substrate in the HTP unit).

[0059] As reactor, conventional fermentation or digestion devices and designs can be used. In one embodiment, the fermenter or digester includes a device for applying a vacuum to the reactor, so that a vacuum is applied during fermentation or digestion and condensate (such as water and ammonia) is removed from the reactor during the fermentation or digestion process. The condensate removed via vacuum is used, for example, for a biological nutrient removal (BNR) process, and the remaining fermentate leaving the vacuum integrated reactor can be directed to an anaerobic digester, a post-pasteurization device and / or a dehydration unit.

[0060] Examples of vacuum integrated reactors of the systems and methods described herein, as well as conditions for operating vacuum integrated reactors, are described in US Patent Application No. 17 / 742,905, which is incorporated herein by reference in its entirety.

[0061] In an alternative embodiment, the reactor is a conventional fermentor or digester without a vacuum, in which case the systems and methods further include a treatment unit or feed line having a vacuum associated therewith (collectively referred to herein as a vacuum integrated treatment unit) upstream, downstream, or both of the fermentor or digester in the process direction. In this embodiment, the fermented / digested material exiting the reactor is subjected to a vacuum to remove condensate as described above.

[0062] The fermentation in the reactor can be carried out under mesophilic, thermophilic or hyperthermophilic conditions, with a temperature range of, for example, 20 to 100° C., preferably 20 to 70° C. The pH can be adjusted using acids or bases to obtain acidic, neutral or alkaline conditions, for example, in the range of 3 to 10. The vacuum can reduce the required addition of base due to the additional stripping of CO gas from the reactor.

[0063] Vacuum used herein can be operated so that treatment chamber is, for example, 1 to 999 mbar, 10 to 750 mbar, 25 to 500 mbar, 25 to 400 mbar or 25 to 300 mbar. This vacuum pressure can be achieved by using a vacuum pump. Vacuum can be applied intermittently (including periodically) so that treatment chamber has a time period in which fluid is subjected to biochemical treatment under vacuum pressure and a time period in which fluid is subjected to biochemical treatment under greater than vacuum pressure. Processing can be performed so that the duration of fluid being processed under a pressure greater than vacuum pressure is equal to or longer than (for example, 1 to 100 times long, 2 to 50 times long or 4 to 25 times long) the time period in which fluid is processed under vacuum pressure.

[0064] The vacuum pump can be controlled by an automatic controller that maintains the processing chamber at a desired pressure, closes the vacuum at a desired time (e.g., based on the amount of condensate collected), etc. The temperature can be, for example, in the range of 10 to 90° C., 20 to 80° C., 30 to 70° C., or 40 to 50° C. The vacuum pressure can be controlled so that the treated fluid boils within these desired temperature ranges. The processing chamber can be heated by any suitable means, such as using a heated stream from other parts of the system or using an electric heating element. The pH of the fermentation / digestate can be maintained in the range of, for example, 3 to 10, 4 to 9, 5 to 8, or 5.5 to 6.5. pH and / or temperature adjustments can be made during the process to concentrate the desired chemicals in the evaporation or fermentation / digestate. The controller can be configured to control not only the removal rate of the condensate from the vacuum reactor or processing unit, but also the residence time of the solid (particulate part) of the treated fluid to be at least 25% longer than the residence time of the soluble part in the vacuum reactor or processing unit.

[0065] Two streams leave the vacuum integrated reactor or vacuum integrated processing unit, namely (1) a condensate stream consisting of the soluble portion removed from the reactor via vacuum, and (2) a fermentate / digestate stream consisting of the remainder, which consists primarily of the solid portion of the fluid. The fermentate / digestate has a higher solids content than the HTP treated fluid entering the vacuum reactor.

[0066] Reactor can be operated when the hydraulic retention time (HRT) of the soluble part of the processed fluid is, for example, 0-3 days (such as 0.1-3 days or 1-3 days) and the solid part hydraulic retention time (SRT) is, for example, 0.5-10 days or longer (such as 1-5 days or 2-3 days). For example, although the typical retention time of the soluble part (water and volatile compounds) in the vacuum evaporator can be about 1-10 hours, in order to achieve biochemical reactions (such as, particle hydrolysis, biomass synthesis, etc.), the retention time of the solid part and microbial cells must be much longer than this time (such as,>10 hours). This can be achieved by using the evaporation process in the vacuum integrated reactor or vacuum integrated processing unit as the solid part retention time is separated from the soluble part retention time and the solid part retention time, the liquid non-volatile retention time and the liquid volatile retention time. In order to achieve optimal performance, one or more variables, such as temperature, pH, pressure, mass transfer, microbial community, nutrients and particle part retention time, can be considered and controlled simultaneously.

[0067] Thus, the vacuum integrated reactor or vacuum integrated processing unit described herein upstream or downstream of a conventional reactor can achieve selective removal of one or more soluble fractions from the processing chamber by vacuum evaporation, which can achieve effective separation of the retention time of the one or more soluble fractions from the retention time of the one or more solid fractions. In this way, using vacuum as the primary mechanism for removing mass and freeing up volume in the processing chamber, one or more solid fractions can be maintained in the processing chamber for a theoretically infinite period of time (due to their relatively insoluble and non-volatile physicochemical properties). As a result, the one or more solid fractions will not be collected in the condensate, thereby keeping the condensate exceptionally pure and free of nutrients.

[0068] In addition, in order to evaporate the volatile components and water, thereby achieving the separation of HRT and SRT, the vacuum reactor or processing unit can utilize the energy (heat and pressure) already provided to the mixture in the HTP stage. In essence, water evaporation and volatile stripping will be achieved by the change of pressure and temperature between the HTP and the evaporation vessel where the vacuum is applied, and the efficiency of evaporation and stripping can be further enhanced by adjusting the pH and conductivity of the mixture.

[0069] The HTP and vacuum integrated reactor or reactor and vacuum integrated treatment unit can be adopted into the wastewater treatment plant with biological nutrient removal unit.

[0070] Figure 1A system including both a hydrothermal treatment device 100 and a vacuum integrated reactor 200 in a system including a downstream anaerobic digester 300 is shown. In this case, the downstream anaerobic digestion can occur as a conventional treatment system. In view of the fact that the treated fluid has undergone removal of most volatile parts (including water) and removal of digestion inhibition compounds (such as ammonia) in the hydrothermal treatment device and the vacuum integrated reactor, digestion can be optimized, including optimization of retention time and value-added solid product recovery. Specifically, the downstream anaerobic digestion can obtain additional gas from the biomass, thereby further enhancing the recovery and production of methane and / or hydrogen.

[0071] Figure 2 A system is shown comprising a hydrothermal treatment apparatus, a reactor 250 (without vacuum) and a downstream vacuum integrated processing unit 280. The vacuum integrated processing unit may be an anaerobic digester, particularly where the reactor is a fermenter. Figure 3 The treatment unit 280 and the anaerobic digester shown in can be a single unit. In addition, as discussed above, a vacuum integrated treatment unit can be located upstream of the reactor.

[0072] Figure 3 2 shows a system including both a hydrothermal treatment device 100 and a vacuum integrated reactor 200 in a system including an upstream anaerobic digester 300. Figure 3 As shown, the fermentation product from the vacuum integrated reactor (in this case, the fermentation tank) can undergo any further required or desired dehydration (i.e., centrifuge), and any liquid recovered in the dehydration can be returned to the anaerobic digestion or vacuum integrated reactor. In addition, the recycled portion of the fermentation product from the vacuum integrated reactor can be recycled to the anaerobic digester.

[0073] Figure 4-7 Specific exemplary systems are shown that employ both hydrothermal processing (in this case utilizing heating obtained by means including heat recovery from condensate extracted from the digestion process) and vacuum digestion (illustrated using IntensiCarb™ vacuum). In these systems, the biomethanation reactor uses biohydrogen stripped from the digestate and from other biogenic sources via the IntensiCarb™ vacuum to supplement methane production, thereby enhancing the conversion of recycled carbon dioxide to methane from the unit. Figure 5 In the pre-pasteurization unit and vacuum are applied before the digester as a pre-treatment for pre-hydrolysis and pasteurization purposes to help achieve the recovery of Class A biosolids from the digester. Figure 6 In a , a second IntensiCarb™ vacuum can be deployed downstream of the digester to achieve dewatering. Figure 7 In the process, a post-pasteurization tank is used after digestion to obtain Class A biosolids.

[0074] The systems and methods can be used to recover one or more value-added products from the system. Many value-added products (precious metals, nutrients, cellulose, coagulants, pharmaceutical compounds, personal care products, etc.) that may be present in wastewater and biosolids are non-volatile and will tend to accumulate in the processing system, thereby facilitating extraction and further purification into high-purity chemicals. In a conventional anaerobic digestion process, the efficiency of the process and the quality of the biosolids produced are primarily due to biological activity. In the process of the present invention, new biosolids with high quality will be produced due to many factors such as combined biological, thermal and mechanical processes. In addition, separating a portion of the water and extracting the volatile compounds (by vacuum) will produce new solids that are not only rich in nutrients and / or high solids content, but also have new compositions.

[0075] The ability to operate vacuum-based digestion or fermentation without regularly removing solids from the system allows the technology to be operated for an optimal period of time and under optimal thermodynamic conditions. Such optimal times and operating conditions can be selected to maximize the accumulation of certain compounds such as cellulose, with the goal of recovering the accumulated material. The same concept can be applied to other valuable products such as nutrients, microbial products, precious metals, etc.

[0076] Volatile fatty acids and ammonia products can be selectively obtained using flash heating and flash pH adjustment in combination with temperature and vacuum - Volatile fatty acids and ammonia are valuable products of anaerobic digestion. In conventional digesters or fermenters (which have continuous feeds entering the digester / fermenter and digestate / fermentation leaving the digester / fermenter), the VFA and ammonia concentrations in the reactor do not accumulate to high concentrations. In the system and method of the present invention, due to the lack of digestate / fermentation and discontinuous condensate, the concentration in the reactor reaches a much higher level than in a conventional digester / fermenter. When VFA and ammonia reach high levels, flash heating and / or pH adjustment under vacuum can promote the recovery of high-purity condensates rich in VFA and / or ammonia.

[0077] Fertilizer can be recovered by dosing chemicals in a vacuum-based and temperature-assisted digestion process. As a result of the extremely long SRT possible in this process, biosolids are expected to be fully stabilized, i.e., Class A biosolids. In this process, once the biosolids reach full stabilization, chemicals (such as potassium) can be accurately dosed to achieve the NPK (nitrogen:phosphorus:potassium) ratio required for commercial-grade fertilizers. Compared to conventional digesters, even if it has the same stabilization efficiency as a vacuum-based digester, the chemical dosing system must be operated continuously.

[0078] Gases and volatile compounds can also be fractionated and selectively extracted from the biosolids processing process. Gases and volatiles produced in a digester or fermenter have different vapor pressures, which can be more or less removed by deploying a continuous vacuum gradient due to the cyclic nature of the vacuum evaporator operation, resulting in partial selective removal and condensation of volatiles. The application of vacuum can enhance the stripping of dissolved anaerobic digestion gases from the reactor, including carbon dioxide, hydrogen, ammonia, hydrogen sulfide, etc. The stripping / removal of these various gases directly and indirectly affects many aspects related to the digester, including: (1) The removal of carbon dioxide (an acid gas) causes the sludge pH to rise. In this way, the digester pH can be controlled to a situation where the production of volatile fatty acids is maximized; otherwise, the pH tends to be over-acidified to a situation where the production of alcohols and ketones (solvent generation) is favored; (2) The removal of hydrogen (a key component of methane production) causes a shift to fermentative microorganisms (acidogens), which causes VFA levels to accumulate and methane production to slow; (3) Hydrogen is also required by sulfate-reducing bacteria, and therefore the removal of hydrogen reduces the rate of hydrogen sulfide production. Removal of hydrogen sulfide (a metal binder) releases essential micronutrients (iron, cobalt, nickel) for extracellular production of hydrolytic enzymes and thus accelerates the fermentation process; (4) Removal of ammonia (a microbial inhibitor) prevents its accumulation in the reactor, thereby allowing long solids retention times without experiencing inhibited methane production; (5) Removal of volatile fatty acids (an important supplemental carbon source) prevents their further conversion to methane in the reactor, thereby allowing their recovery to support plant processes such as biological phosphorus removal and denitrification. Therefore, by controlling pH, temperature and vacuum, some of these gases can be made more or less volatile, allowing them to be more or less selectively removed from the reactor. Therefore, the above advantages can be selectively controlled.

[0079] In addition to the aforementioned advantages from using a vacuum integrated reactor or a vacuum integrated processing unit, it is novel to further include an HTP before the vacuum integrated reactor or the vacuum integrated processing unit, and the combined use of the HTP with the vacuum integrated reactor or the vacuum integrated processing unit reduces the viscosity and mixing problems caused by the thickening in the vacuum reactor. The HTP improves the strengthening potential of the reactor. It has been found that the fermentation and AD reactors integrated with the HTP contain a large amount of ammonia, which inhibits the acetogenic and methanogenic activities, thereby resulting in lower VFA and methane production (in view of the large amount of ammonia released during the HTP). However, by integrating the HTP with the vacuum integrated reactor or the vacuum integrated processing unit, ammonia is continuously recovered. The recovered ammonia not only improves the digester / fermenter performance, but also captures ammonia that can be used for other purposes.

[0080] The diversity of the microbial community can also be reduced by HTP, thereby eliminating methanogens in the vacuum reactor when used as a fermenter. In conventional fermenters, methanogens can inhibit the acetogenic process, and in vacuum fermenters integrated with HTP, methanogens cannot survive at high temperatures (e.g., over 70°C). Therefore, integrating HTP into a system with a vacuum integrated reactor also increases organic matter dissolution, VFA production, and ammonia production. Hydrolysis is the rate-limiting step in conventional digesters, and at 170°C, HTP dissolves organic compounds up to, for example, 40%, thereby overcoming this challenge. The vacuum reactor or vacuum integrated processing unit further dissolves the material and ultimately produces and recovers more amounts of VFA and ammonia.

[0081] The subject matter herein will be further illustrated by the following examples.

[0082] Example 1

[0083] The substrate used in this example was thickened waste activated sludge (TWAS) obtained from the Ashbridge's Bay Wastewater Treatment Plant in Toronto, Canada. The hydrothermal treatment of the substrate was carried out under six different conditions - the temperature was fixed at 170°C, and six retention times of 10, 20, 30, 40, 50 and 60 minutes were tested. A Parr 4848 hydrothermal reactor (Parr Instrument Company, IL, US) with a capacity of 2 L was used for HTP. The volume of TWAS treated each time was 1 L.

[0084] All treated samples had higher contents of soluble compounds compared to the original untreated samples. Figure 8 Different soluble components such as VFA, soluble carbohydrates and soluble protein concentrations are shown for the treated samples and the original untreated samples. Comparison of the soluble content in the original samples with the hydrothermally treated samples confirmed that HTP increased the concentration of all soluble compounds.

[0085] Fig. 9 The percentage reduction of TSS and VSS due to hydrothermal treatment is shown. As shown in the figure, increasing the retention time up to 30 minutes causes an increase in solid reduction, and it stabilizes thereafter. The TSS reduction of the hydrothermally pretreated samples ranges from 20% to about 35%. On the other hand, the VSS reduction ranges from 23% to about 40%. At a retention time of 10 minutes, a 23% VSS reduction is achieved; at a retention time of 20 minutes, this percentage increases to 32%, and reaches a maximum of 40% at a retention time of 30 minutes. After a retention time of 30 minutes, the VSS reduction does not change significantly.

[0086] Fig.10 The particle size distribution (PSD) of the original sample and the hydrothermally treated sample is shown. As shown in the figure, all the treated samples have a lower particle size compared to the original sample. The d10 and d90 of the original sample are 27 μm and 187 μm, respectively. For the pretreated samples, these values ​​dropped to 15 μm and 125 μm. Increasing the retention time is associated with a decrease in the particle size of the pretreated samples (p < 0.05). The smallest particle size is observed for the sample pretreated for 60 minutes. At a retention time of 60 minutes, the d10, d50 and d90 are 15.2 ± 2.4 μm, 47.8 ± 11.8 μm and 145.5 ± 1.7 μm, respectively, which is a 45%, 42% and 22% reduction in particle size compared to the original sample.

[0087] Example 2

[0088] The substrates used in this example were thickened waste activated sludge (TWAS) and primary sludge (PS) obtained from the Ashbridge wastewater treatment plant in Toronto, Ontario. The substrates used were subjected to secondary treatment and thickening. The inoculum used was also obtained from the anaerobic digestion (AD) tank at the Ashbridge plant, which was operated at a mesophilic temperature range (34-38°C) and an HRT of 18 days for the sludge. The properties of the original TWAS and the inoculum are shown in Table 1. Return activated sludge (RAS) was collected from the Greenway wastewater treatment plant (London, Ontario) and used as a source of biomass for denitrification testing. The detailed characterization of RAS is also summarized in Table 1.

[0089] Table 1

[0090]

[0091] Both raw sludge and treated sludge were fed to the fermentation process to evaluate the effect of HTP in conventional and vacuum modes. Therefore, four systems were evaluated: S1 = conventional fermentation (no HTP or vacuum) (fed with raw TWAS and PS); S2 = vacuum integrated reactor fermentation (fed with raw TWAS and PS); S3 = HTP and conventional fermentation (fed with HTP-treated TWAS and raw PS); and S4 = HTP + vacuum integrated reactor fermentation (fed with HTP-treated TWAS and raw PS). HTP of TWAS was performed at a temperature of 170°C, a holding time of 30 minutes, and a pressure of 6 bar.

[0092] S4 is capable of achieving enhanced biochemical fermentation and simultaneous thickening of municipal biosolids vacuum-driven evaporation of treated sludge at temperatures of 20-60°C. This process combines thickening, hydrolysis, acidification, gas stripping and dehydration via near-ideal solid-liquid separation, so that biochemical and physico-chemical treatment processes are intensified. The intense bubbling in vacuum boiling intensifies the mass transfer rate between gas, liquid and solid components. In contrast, mass removal by vacuum evaporation allows the non-volatile soluble portion of the fermented biosolids (including nutrients such as ammonia and phosphates) to be fully retained. An auxiliary unit for heat recovery is integrated with the vacuum evaporation chamber to recycle the latent heat of evaporation back into the process. The complete system consists of the following components: (1) a heat exchanger for preheating the feedstock using the recovered latent heat of evaporation, (2) a main reactor vessel operating under vacuum (which can perform both the fermentation process and the thickening process of the biosolids), (3) a vacuum pump for extracting the steam generated during evaporation, and (4) a second heat exchanger for recovering the heat available in the fermented sludge.

[0093] S1 was fed with 50:50 (by volume) of raw PS and TWAS, while S3 was fed with a mixture of hydrothermally treated TWAS and raw PS (50:50). The semi-continuous conventional fermentation system was operated under thermophilic conditions (45°C). Conventional fermenters (SRT = HRT = 3 days) were operated (1.5 L fermentation volume) by discarding 1 / 3 of the sludge (500 mL). Both S1 and S3 were started by mixing 1 liter of heat-pretreated seed (heated at 70°C for 30 minutes to inhibit methanogenesis) and 0.5 liter of feed.

[0094] S2 and S4 (SRT = 3 days, HRT = 1.5 days) were operated by applying vacuum for 10 hours daily at -900 mbar pressure (or +100 mbar absolute pressure, equivalent to a boiling temperature of 45°C) to evaporate 1,500 mL of the 3 L fermentation volume. In order to maintain the same SRT as the conventional control fermenter S1 (3 days), one-third (1 / 3) of the sludge volume remaining after evaporation was discarded daily and replaced with fresh mixed sludge. Between vacuum applications, S2 and S4 were maintained at 45°C using a water bath, and pressure and temperature were continuously monitored during vacuum operation. All systems S1-S4 were operated until quasi-steady-state conditions were reached.

[0095] Condensate (high grade VFA) was tested for suitability as a carbon source for denitrification testing, and fermented product was used as a feed for anaerobic digestion (AD). In order to evaluate the impact of HTP and vacuum on fermented product and condensed product as a carbon source for biological nutrient removal, a series of batch tests were carried out to enhance denitrification. These samples included fermented products of both conventional and vacuum systems with original sample and treated sample feed. In addition, the condensate of the vacuum system and the supernatant of the fermented product were used as carbon sources. In order to avoid carbon limitation during the test, the ratio of soluble chemical oxygen demand (COD) to nitrate was maintained at a minimum of 8:10. Mixed liquor suspended solids (MLSS control) or RAS without additional carbon source were also tested to check background denitrification activity (MLSS control). In order to compare and analyze the SDNR of external carbon source and commonly used commercial carbon source, acetate was also fed to one of the reactors in the batch series.

[0096] Fermentations and fermentation centers from the four systems were used as substrates for the biochemical methane potential (BMP) test. The BMP test was used to determine the methane productivity and biodegradability fraction of the samples.

[0097] Water and gas quality analysis including total suspended solids (TSS), volatile suspended solids (VSS), total chemical oxygen demand (TCOD), soluble chemical oxygen demand (SCOD), carbohydrates, protein, VFA, biogas production and biogas composition were analyzed. The viscosity of the samples was measured on a Fungilab™ Viscolead One viscometer (Fungilab Inc.) using an L3 spindle and a rotation speed of 100 rpm.

[0098] Hydrothermal treatment and vacuum fermentation significantly affected sludge lysis both as individual factors and in combination (p>0.005). Fig.11 Shown the variation in time of chemical oxygen demand (COD) dissolving in the conventional and vacuum fermentation reactor of the sludge feed processed through HTP.As observed in the figure, compared with conventional fermentation tank, higher dissolving is produced in the vacuum fermentation reactor.During the steady state stage, compared with conventional fermentation, vacuum fermentation demonstrates the 10-15% improvement in COD dissolving.In addition, the total COD of vacuum fermentation is dissolved in the scope of 44-47%, and the total COD of conventional fermentation is dissolved in the scope of 35-40%.Total COD dissolving includes the dissolving caused due to HTP (25-30%) and fermentation.

[0099] On the other hand, two fermentation reactors (conventional and vacuum) fed with raw sludge were studied, highlighting the advantages of vacuum fermentation over conventional fermentation. Fig.12The COD dissolution of sludge in two reactors (vacuum and conventional) is shown to change over time.Compared with conventional reactor, 25-30% improvement was detected in vacuum reactor.Relative to conventional fermentation, the higher cleavage rate in vacuum fermentation may be due to the lower pressure in vacuum reactor and therefore the higher stress to biomass cell wall.In addition, the extraction of liquid from vacuum fermentation may be another factor, because the solid content of vacuum reactor increases over time.Sludge accumulation can contribute to retain higher sludge volume / solids in reactor.

[0100] Furthermore, the results showed that integration of hydrothermal treatment with vacuum fermentation significantly improved overall sludge hydrolysis (p>0.005), while its effect on fermentation was similar to that of the original feed. Fig.13 The average COD dissolving for all four systems is reported, to compare. The figure shows two vacuum fermentation systems (feeding with sludge processed through HTP or with original sludge feeding) with almost similar 29% and 31% dissolving efficiency (due to only fermentation). On the other hand, due to HTP and fermentation, the total COD dissolving of the feed processed through HTP in the vacuum reactor is 32% higher than the original feed reactor. This percentage means that most of the dissolving occurs during the HTP period, rather than during the fermentation period.

[0101] In general, HTP with vacuum fermentation can potentially lead to higher hydrolysis rates, improve solids reduction efficiency, and reduce the energy required to heat the fermentor because the HTP-treated TWAS provides additional heat to the fermentor. For example, with an adiabatic system and minimal heat losses, the heated substrate may be sufficient to maintain the fermentor temperature at a desired temperature or reduce the energy input used to heat the fermentor.

[0102] In the current study, significant differences in VFA production were observed for the four systems (p>0.005). In addition, vacuum and hydrothermal pretreatment integration showed superior results to those without vacuum and pretreatment. Fig.14 The VFA production of fermentation products, condensates and total fermentation products + condensates of treated samples in conventional and vacuum integrated reactors is shown over time. No obvious lag phase was observed during the two fermentation processes, and the VFA production gradually increased throughout the fermentation process, reaching a stable level in the steady state stage. This figure compares the VFA production of conventional fermentation with the new configuration of the integrated HTP-vacuum integrated reactor and the HTP-treated sample feed, highlighting the effect of vacuum application on VFA, which increased it by about 30% (considering the VFA produced by both the condensate and the fermentation product of the integrated system).

[0103] The biological nutrient removal process in wastewater treatment plants requires a carbon source produced by on-site organisms. The VFA produced during fermentation is a significant source of biological carbon source. In this example, the effluents of four different fermentation systems were tested to be used as potential carbon sources for denitrification. In addition, the fermentations of all four reactors were centrifuged to obtain a pure liquid (supernatant) with a low solid content and used as a carbon source. The specific denitrification rate (SDR) and biomass yield of all these carbon sources are shown in Table 1. Fig.15 and 16 The results showed that the condensates from the S2 and S4 reactors without and with HTP treatment had the highest specific denitrification rates of 7.6 and 7.2 mg NO, respectively, compared with all other samples and the control (acetate). 3 -N / g VSS•h. The high efficiency of the condensate may be due to the presence of highly biodegradable compounds (high-grade VFA) and low solids concentration. In addition, due to the low biomass concentration in the condensate, the only active bacteria were denitrifiers. On the other hand, the fermented samples contained fermenting bacteria, which changed the diversity of bacteria in the process and thus reduced the denitrification rate.

[0104] In addition, regardless of the fermentation reactor configuration, HTP improves the denitrification process. Compared with the system fed with the original TWAS, all reactors containing samples treated with HTP show slightly higher SDR (up to 10%). In addition, compared with conventional reactors, carbon sources from S2 and S4 show accelerated denitrification rates. Due to the simultaneous removal of inhibitory compounds such as ammonia, the production of high-grade VFA and higher concentrations of VFA may be the most important factor in terms of the higher efficiency of S2 and S4 effluents. During vacuum fermentation, ammonia is removed and higher concentrations are produced, which can be further recovered by different methods. Ammonia production itself is another advantage of vacuum fermentation. Finally, the integration of vacuum and HTP is also associated with higher ammonia production, which increases the benefits of this new process integration (due to the potential for nutrient recovery to a large extent through ammonia stripping and other pathways).

[0105] In addition, the depletion of nitrate and COD over time showed better results for HTP treated and vacuumed samples (compared to original samples). All HTP treated samples were associated with higher nitrate removal rates, as the peak of nitrite occurred within 45 minutes compared to acetate and original samples which were delayed to 60 minutes and 120 minutes, respectively.

[0106] The BMP results showed that the novel configuration of the HTP and vacuum integrated reactor promoted hydrolysis and VFA production and significantly enhanced the methane production yield. Fig.17 and 18The cumulative methane production of the four systems over time is shown. As can be seen in both figures, the samples treated with hydrothermal treatment generally show higher enhancement potential than the original samples. Compared with the original feed, the methane production of the samples after HTP and fermentation increased by 46-59%. In addition, the effect of HTP on each fermentation reactor was compared with the HTP conventional fermentation sample (255 mL CH 4 / g added TCOD), the original conventional fermentation sample had a lower methane yield (225 mL CH 4 / g added TCOD). Similarly, in S2 and S4, the original vacuum fermentation samples (237 mL CH 4 / g added TCOD) compared to the treated sample with higher methane yield (267 mL CH 4 / g added TCOD).

[0107] Conventional fermentation contributed to the enhanced methane production, but vacuum fermentation showed a higher impact on the improvement of methane production. Ignoring the HTP effect, the original conventional fermentation sample and the original vacuum fermentation sample showed 28% and 36% increase in methane production compared to the original sample, which means the impact of the integrated system (HTP+vacuum) on the AD performance.

[0108] Likewise, the biodegradability of the samples was improved by the application of HTP and vacuum. The biodegradability of both systems fed with the original samples (56-59%) was lower than that of both systems fed with the HTP-treated samples (64-67%), implying the advantage of HTP regardless of the fermentation reactor configuration.

[0109] In batch BMP tests, in addition to methane production yield, methane production rate is also a key process response parameter for evaluating the biodegradability of substrates. The methane production rates of HTP-treated feed and original feed are shown in Fig.19 and 20 Given that the origin of the inoculum and the substrate were identical, no clear lag phase was observed for all samples. Two main peaks were observed throughout the BMP test for all samples. The first peak, associated with the greatest methane production, was between days 2-4 for the pretreated samples and between days 2-3 for the original samples. The second minor peak was detected in the second week of the test, when slowly biodegradable organic matter began to degrade. In addition, 64 mL CH 4 The maximum methane production of 100 g / g added COD demonstrated the methane production efficiency of the HTP-treated samples.

[0110] Furthermore, the BMP data showed that the application of vacuum enhanced the methane production rate by up to 25% compared to a conventional reactor without vacuum. The maximum methane production for the HTP treated sample in the vacuum reactor was 64 mL CH 4 / g added COD, while this was reduced to 48 mL CH 4 / g added COD. The effect of vacuum application in improving methane production rate may be related to the high solubility during vacuum fermentation, which is caused by high heat and microbial activity, and finally produces a large amount of easily biodegradable compounds for AD. In conclusion, the novel configuration of HTP and vacuum reactor improved VFA production and showed excellent results in terms of methane production rate and yield.

[0111] According to this embodiment, the integration of vacuum in the fermentation reactor results in the following benefits: (1) vacuum application enhances mass transfer due to bubbling when the reactor is operated above boiling point, as well as the possibility of simultaneously concentrating solids and evaporating liquids; (2) fermentation process performance is enhanced due to the removal of inhibitory substances produced during the fermentation process. VFA production is increased by about 40% by vacuum application; (3) acid accumulation is controlled due to the continuous extraction of VFA from the system. Integration of HTP with vacuum fermentation results in the following additional benefits: (1) acceleration of the fermentation process and reduction of the required HRT to 1.5 days; (2) enhanced fermentation productivity, i.e., higher VFA yield (330 mg COD / g VSS) for vacuum fermentation (using HTP) compared to VFA yield (210 mg COD / g VSS) for conventional fermentation (using HTP); (3) enhanced solubility (45% for vacuum (using HTP) and 39% for conventional (using HTP)) and improved solids reduction efficiency; and (4) reduced energy required to heat the fermentor, since the pretreated TWAS provides additional heat to the fermentor, i.e., has an excellent insulation system with minimal heat loss; the heated substrate can be sufficient to maintain the fermentor temperature at the desired temperature or at least reduce the energy input used to heat the fermentor.

[0112] Example 3

[0113] The microbial communities of novel configurations of hydrothermal treatment and vacuum fermentation were investigated, thereby comparing the application of vacuum fermentation with conventional and HTP treatment and no HTP treatment integration. In the investigation, each semi-continuous system was operated using similar conditions in terms of HTP (170°C temperature and 30 minutes RT) and HRT (1.5 days) using a feed of TWAS + raw PS for about 20 days.

[0114] Genomic DNA was extracted from biomass using PowerSoil DNA isolation kit (MoBio Laboratories Inc.). DNA samples were sent to the Genome Quebec research and testing laboratory in Montreal, Quebec (Montréal, Québec) to carry out 16S rRNA gene sequencing (Illumina MiSeq). PCR amplification DNA samples were used for amplicon preparation. Primers 347F (GGAGGCAGCAGTRRGGAAT) and 803R (CTACCRGGGT ATCTAATCC) were used to amplify the V3-V4 region of the 16SrRNA gene. Second PCR reaction was performed to integrate sample-specific barcodes. Picogreen was used to measure the DNA concentration of all PCR reactions so that all samples of equimolar concentrations can be used for sequencing. Paired end 250 kits (Illumina MiSeq) were utilized to sequence the amplicon library with an insertion size of about 450 bases. Operational taxonomic unit (OTU) table and corresponding FASTA files were generated using 16S rRNA gene sequences. The analysis was performed by the Canadian Centre for Computational Genomics at McGill University. The GenPipes version 4.0.0 (Bourgey et al., 2019) amplicon sequencing pipeline was used for analysis. The process is based on the DADA2 package in the R environment. First, Trimmomatic (Bolger et al., 2014) was used to trim and 16 bp was removed from the beginning of the fragment (reads). Then, 5,308,340 paired-end fragments were passed through the applied quality filtering parameters [truncLen=c(234,234); max N = 0; max EE=c(2,2); trunc Q = 2], with an average of 186,983 fragments / sample, and therefore merged (minimum overlap of 20 bp) and subjected to de novo chimera removal. The resulting amplicon sequence variants (ASVs) were classified using the Silva database version 123.

[0115] The results show that bacteria were observed to be abundant microorganisms in all four systems (no HTP, no vacuum; no HTP, vacuum; HTP, no vacuum; and HTP, vacuum). The most abundant bacterial type was Coprothermobacteraeota, followed by Synergistetes, Thermotogae, and Firmicutes, which are mainly anaerobes grown under thermophilic conditions (55°C-70°C). The presence of these bacteria indicates that anaerobic conditions were well maintained during the experiment. All of the above-mentioned bacteria were not detected in the feed.

[0116] The alpha diversity measurement evaluated the richness of the diversity of the microbial communities compared between the control and vacuum fermentation reactors. The number of amplicon sequence variants (ASVs) observed in both systems gradually decreased with fermentation time, indicating that the diversity in these systems was lower as the fermenters grew into the dominant microbial community. The ASV of all systems decreased during the steady state period compared to when they were started, indicating good performance of the reactor (fermenter). In addition, the vacuum application showed a great impact on alpha diversity. For all sample points, the ASV for vacuum reactors was 15-20% lower than that for conventional reactors. Considering the steady state data, the average ASV values ​​for vacuum and conventional reactors were 14 and 16, respectively. Typically, 10 phyla types were detected for the fermented samples in both reactors, and the presence of a lower number of phyla in the vacuum reactor confirmed the effect of vacuum on the changes in microbial structure. The main bacteria present in all samples were divided into two main phyla (Thermobacteria and Syntrophobia), followed by Firmicutes, Thermobacteria, Actinobacteria, and Euryarchaeota as the next relatively abundant phyla. In addition, as the pH of the reactor increased during fermentation, the Euryarchaeota phylum (which belongs to the archaea and is responsible for methane production) was completely suppressed. During the steady-state stage of fermentation, the average relative abundance of Thermobacteria in the vacuum and conventional systems was 75% and 65%, respectively, compared to 15% and 25% for Syntrophobia, respectively, confirming favorable conditions for each phylum.

[0117] Considering that there were significant differences between the number of ASVs observed, hydrothermal treatment significantly affected the diversity of the microbial community. Regardless of the fermentation technology, the ASV of the HTP-treated samples was higher than that of the original samples. Compared with the original samples, about 12% and 20% enhancements were observed for the ASV values ​​of the HTP-treated samples from the vacuum and conventional systems, respectively. The richness of the diversity of the HTP-treated samples may be due to the changes in the chemical composition of the feed and the elimination of bacteria present in the TWAS during the HTP. In addition, the results from the alpha diversity analysis showed that the type of fermentation reactor was a key factor in the richness of microbial diversity when the system was fed with HTP-treated sludge. In contrast, in the absence of hydrothermal treatment, the type of technology did not have a prominent effect on the diversity of the microbial community. In addition, the relative abundance analysis of microorganisms further demonstrated the effect of HTP on the microbial community and the enrichment of specific bacterial communities. The dominant bacterial types found for the HTP-treated samples from both systems and the original samples for the vacuum system were the Thermococcus and Intertrophic bacteria, while on the other hand, for the original-conventional samples, the Thermococcus and Intertrophic bacteria were the most abundant phyla. HTP has been shown to nourish and accelerate the growth of thermophilic bacteria.

[0118] In addition to fermentation and hydrolytic bacteria, low percentages of small communities of methanogens and nitrifiers were observed. The low relative abundance of Archaea and Bacteria, such as Euryarchaea (methane producers) and Planctomycetes (nitrifiers), indicated excellent fermentation performance and configuration to mitigate the function and growth rate of inhibitory microbial communities.

[0119] Bacteria were the dominant microbial community in all the systems studied. Microbial community analysis showed that the application of vacuum fermentation significantly affected the microbial diversity and composition. This effect was confirmed by the lower ASV values ​​for vacuum compared to conventional reactors and the presence of a large number of Faecalibacterium and Syntrophobacteria communities in the vacuum system. In addition, hydrothermal HTP treatment enriched the thermophilic microbial community and had higher ASV values ​​than the original samples.

[0120] Although specific embodiments are described herein, the scope of the present invention is not limited to these specific embodiments. The scope of the present invention is defined by the appended claims and any equivalents thereof. As will be appreciated by those skilled in the art, aspects of the present disclosure may be embodied as devices, systems or methods.

[0121] The diagrams in the accompanying drawings illustrate possible implementations of the apparatus and methods according to various embodiments of the present disclosure, the architecture, functions and operations. In this regard, each block or feature in the accompanying drawings may represent a module, segment or portion of a method or apparatus, and the functions indicated therein may not occur in the order indicated in the accompanying drawings. For example, two blocks or features shown in succession may actually be executed substantially simultaneously, or the blocks or features may sometimes be executed in reverse order, depending on the functions involved.

Claims

1. A method for treating a fluid comprising a particulate fraction and a soluble fraction, the method comprising: feeding the fluid to a hydrothermal treatment device and subjecting the fluid to heating to a temperature of 121° C. or higher to obtain a treated fluid; subsequently feeding the hydrothermally treated fluid to a reactor, wherein at least the particulate fraction undergoes fermentation or anaerobic digestion, wherein the treated fluid is subjected to vacuum pressure upstream of, during or downstream of the fermentation or anaerobic digestion in the process direction; wherein if the vacuum pressure is applied during the fermentation or anaerobic digestion, the reactor is a vacuum integrated reactor, and the method comprises collecting at least a portion of the soluble portion of the fluid (comprising water and gas) as condensate from the vacuum integrated reactor and collecting residual gas, and thereby thickening the remainder of the fluid; wherein if the vacuum pressure is applied upstream or downstream of the fermentation or anaerobic digestion in a vacuum integrated processing unit, the method comprises collecting at least a portion of the soluble portion of the fluid comprising water and gas from the treated fluid or from the treated and fermented or digested fluid as condensate and collecting residual gas and thereby thickening the remainder of the fluid; as well as The thickened fluid is recovered.

2. The method according to claim 1, wherein the reactor is a vacuum integrated reactor selected from a vacuum integrated fermenter and a vacuum integrated digester.

3. The method according to claim 1, wherein the heating in the hydrothermal treatment device is at 130 to 300°C for 5 to 100 minutes at a pressure of 2 to 10 bar.

4. The method of claim 1, wherein the fluid is thickened waste activated sludge having a solids content of 1% to 16%.

5. The method of claim 1, wherein prior to subsequently feeding the hydrothermally treated fluid to the reactor, the treated fluid is mixed with an additional fluid comprising a particulate fraction and a soluble fraction, the additional fluid having a higher degree of biodegradability than the fluid.

6. The method according to claim 1 or 2, wherein the vacuum pressure is 10 to 750 mbar.

7. The method of claim 6, wherein the vacuum is applied intermittently during the fermentation or anaerobic digestion.

8. The method of claim 1, wherein water evaporation and volatile stripping are achieved by changes in pressure and temperature between the hydrothermal treatment device and the vacuum integrated reactor or vacuum integrated processing unit, and the efficiency of the evaporation and volatile stripping is further enhanced by adjusting the pH and conductivity of the treated fluid.

9. The method of claim 1, wherein heat is extracted from the condensate and used to provide heating to a fluid in the hydrothermal treatment device.

10. The method of claim 1, wherein the recovered thickened fluid is subjected to further processing comprising one or more of anaerobic digestion, dehydration, and post-pasteurization.

11. The method of claim 1 , wherein the condensate is subjected to further processing comprising denitrification or biomethanation.

12. The method of claim 1, wherein the fluid is subjected to a treatment selected from the group consisting of anaerobic digestion and pre-pasteurization prior to feeding the fluid to the hydrothermal treatment unit.

13. The method of claim 1, further comprising feeding at least a portion of the recovered thickened fluid to a biological nutrient removal process.

14. The method of claim 1, further comprising cooling the hydrothermally treated fluid to 75°C or less before feeding the hydrothermally treated fluid to the reactor.

15. A system for treating a fluid comprising a particulate fraction and a soluble fraction, the system comprising: a hydrothermal treatment device configured to treat a fluid fed thereto by heating, a reactor downstream of the hydrothermal treatment device in the process direction, the reactor being configured to receive the treated fluid from the hydrothermal treatment device and subject the treated fluid to fermentation or anaerobic digestion, wherein the reactor is selected from: a vacuum integrated reactor having a vacuum pump for applying a vacuum to the vacuum integrated reactor; and a reactor without a vacuum pump, Wherein if the reactor is a reactor without a vacuum pump, the system further comprises a vacuum integrated processing unit upstream and / or downstream of the reactor in the process direction, the vacuum integrated processing unit comprising a vacuum pump for applying vacuum to the vacuum integrated processing unit, and wherein the condensate is removed by utilizing the vacuum; as well as A controller is configured to control the vacuum and the removal of the condensate and to control the residence time of the particulate fraction in the reactor to be at least 25% longer than the residence time of the soluble fraction.

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