A method of determining two-stage anaerobic system reaction zone or reactor volume parameters

Abstract

The present application belongs to the technical field of anaerobic treatment, and particularly relates to a method for determining volume parameters of hydrolysis-acid production and methanogenesis reaction zones or reactors in a two-stage anaerobic fermentation system, which comprises the following steps: 1. determining material hydrolysis-acid production and methanogenesis characteristics through batch test experiments; 2. determining characteristics required by reaction zones or reactors adapted to hydrolysis-acid production process and methanogenesis process functional microorganisms through microbial growth kinetics calculation; 3. selecting specific configurations of hydrolysis-acid production reaction zones or reactors and methanogenesis reaction zones or reactors in the two-stage anaerobic fermentation system; 4. determining volume correction parameters X1 and X2 of the hydrolysis-acid production and methanogenesis reaction zones or reactors; and 5. combining material characteristics obtained through batch test experiments, selected reactor configurations and corresponding volume correction parameters to determine volume parameters of hydrolysis-acid production and methanogenesis reaction zones or reactors in the two-stage anaerobic fermentation system to be designed.

Description

Technical Field

[0001] This invention belongs to the field of anaerobic treatment technology, specifically a method for determining the volume parameters of the hydrolysis acid production and methanogenesis reaction zones or reactors in a two-stage anaerobic fermentation system. Background Technology

[0002] Anaerobic fermentation, as a mature waste and sewage treatment technology, has been widely applied. Two-stage or two-phase anaerobic fermentation systems maximize the metabolic efficiency of functional microorganisms at each stage by separating the hydrolysis-acidification and methanogenesis stages into two reaction zones or reactors with different conditions, thereby improving the overall efficiency of anaerobic conversion of organic waste. Therefore, two-stage anaerobic fermentation systems have better treatment effects than traditional single-stage anaerobic fermentation and have attracted widespread attention from academia and engineering. However, currently, there is a lack of clear calculation and design methods for the volume ratio of the hydrolysis-acidification and methanogenesis stages in two-stage or two-phase anaerobic fermentation systems. This makes it difficult to effectively couple the two functional stages in research and practical engineering to maximize material conversion efficiency. Furthermore, the hydrolysis-acidification and methanogenesis reaction zones or reactors in two-stage anaerobic fermentation systems often fail to reach their optimal operating states, meaning that the designed two-stage anaerobic fermentation systems are prone to insufficient or wasted effective working space for the hydrolysis-acidification and methanogenesis stages. If the working space in the hydrolysis-acidification stage is insufficient, the substrate cannot be fully converted before entering the methanogenesis unit, causing some substrate decomposition to be transferred to the methanogenesis reactor. This can easily lead to acidification and inhibition of the methanogenesis stage. However, if the working space of each unit is deliberately designed to be too large to avoid the potential negative effects of insufficient working space, it is wasteful and can easily lead to excessive construction, operation, and maintenance costs. The configuration and volume of the reaction zone determine the hydraulic retention time and microbial retention characteristics of the reaction zone, which, once determined, limits the utilization efficiency of the organic load. This is especially true for two-stage integrated anaerobic fermentation systems, which are difficult to readjust during operation. Therefore, the ideal two-stage anaerobic fermentation system should be designed to fully utilize the effective working space of the hydrolysis-acidification and methanogenesis reaction zones or reactors while minimizing the waste of space in each stage of the reaction zone or reactor.

[0003] Furthermore, there are differences among the various raw materials used in the two-stage anaerobic fermentation process, and the microbial characteristics, biochemical reaction types, and rates differ during the anaerobic fermentation conversion of different raw materials. Therefore, it is necessary to fully consider factors such as the material properties of the fermentation raw materials and the microbial characteristics in different reactor configurations in order to design a two-stage anaerobic fermentation system that better meets the needs of practical applications.

[0004] To the extent the inventors have known, current research and patents regarding solutions to the problems existing in the aforementioned two-stage anaerobic fermentation systems are very limited. Related patents and research mainly focus on proposing fermentation systems with certain specific combinations or structures, lacking corresponding design methods such as rationale for reactor configuration selection and determination of volume parameters. For example:

[0005] CN103421678A discloses a biomass-based mixed hydrogen-to-alkane system and production method, using a CSTR as the hydrogen production reactor and a UASB as the methane production reactor. The hydrolysis acid-producing reactor and the methanogenic reactor are connected via material pipelines, with a volume ratio of 1:1 to 10. The substrate conversion rate and gas production rate of the acid-producing and methanogenic reactors are adjusted and controlled by an external material reflux device, ultimately increasing the proportion of biomass converted to hydrogen-alkane and obtaining a suitable proportion of hydrogen-alkane. This two-stage reactor is mainly used to process biomass with high solids content, including wood, straw, fallen leaves, sawdust, animal carcasses and manure, municipal waste and domestic organic waste, agricultural waste, lignocellulose, organic waste or sludge, terrestrial and aquatic plants, and mixtures thereof.

[0006] CN102796765A discloses a method for treating easily degradable organic waste using a two-phase hydrogen-to-methane coupled reaction. Its main feature is that the solid, liquid, and gaseous products from the first-stage hydrolysis of organic waste to produce acid are all used in the second-stage methane production. The gaseous products from the first stage undergo pressure swing adsorption (PSA) to remove carbon, achieving a hydrogen concentration of 80%, which is then used in the second stage to increase methane production by approximately 20% and consume some carbon dioxide. The methanogenic reactor in this patent includes all high-efficiency anaerobic reactors, but there are no restrictions on the hydrolysis-to-acid reactor.

[0007] CN101172710A discloses a two-stage, two-phase anaerobic process for treating high-concentration organic wastewater. This method uses a two-stage reactor consisting of an acidification reactor and a methanogenic reactor, which are independent of each other. The main operating parameters (pH, temperature, circulation, stirring, reflux ratio, volumetric loading, influent flow rate, etc.) of the acidification and methanogenic reactors are specified, but there are no explicit methodological restrictions on the selection of reactor configuration and the design of volumetric parameters.

[0008] CN102115258A discloses a two-phase integrated anaerobic reactor. This reactor consists of a left-side acid-producing tank and a right-side methanogenic tank connected at the bottom. The acid-producing tank contains an S-shaped water flow channel composed of baffles and deflectors, while the methanogenic tank contains packing material to enrich microorganisms and form a biofilm, reducing microbial loss. However, the ratio between the methanogenic and acid-producing zones, as well as their respective structural characteristics, may not be suitable for the growth of the corresponding functional microorganisms and the transformation of different substrates.

[0009] CN102603124A discloses a two-phase, two-stage anaerobic bioreactor for treating wastewater. This two-phase, two-stage reactor integrates an acidification reaction chamber and a methane reaction chamber within the same reactor, with the acidification reaction chamber having a height-to-diameter ratio... Methanation reactor height-to-diameter ratio The integrated two-phase anaerobic reactor has a complex structure (e.g., alkali addition device, funnel swirl water distribution device, water inlet and circulation device, internal and external composite structure, etc.), and once built, it is difficult to change. Therefore, it is essential to determine reasonable reactor design parameters in advance based on different substrate characteristics.

[0010] CN106282243A discloses an improved method for two-phase anaerobic fermentation to produce methane. This method is primarily designed for two-phase anaerobic fermentation of high-solids-content organic waste (kitchen waste, sludge, crop straw, etc.). The improved technique involves controlling the headspace gas pressure in the hydrolysis acid production reactor and using the headspace gas for methane production, ultimately improving the hydrolysis acid production efficiency and methane recovery rate. Summary of the Invention

[0011] The purpose of this invention is to provide a method for determining the volume parameters of the reaction zone or reactor in a two-stage anaerobic system, in order to solve the problems of lack of theoretical guidance in determining the volume parameters of the reaction zone or reactor in the hydrolysis acid production stage and methanogenesis stage of a two-stage anaerobic system, which leads to overload of the working space of the reaction zone or reactor or even failure to operate normally, or excess working space that wastes the construction, operation and maintenance costs of the reaction zone or reactor.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A method for determining the volume parameters of the reaction zone or reactor in a two-stage anaerobic system, the method comprising the following steps:

[0014] Step 1: Determine the acid production and methanogenesis characteristics of the material through batch experiments;

[0015] Through small-scale, short-term batch experiments in the laboratory, the time, lag period, gas production potential, and organic matter removal efficiency required for the actual materials to be used in the two-stage fermentation process to complete hydrolysis and acid production and methanogenesis sequentially were determined. Then, the ratio of hydraulic residence time and volume between the hydrolysis and acid production reaction zone or reactor and the methanogenesis reaction zone or reactor was determined by the ratio between the material conversion time and the hydraulic residence time or volume of the two-stage anaerobic system reaction zone or reactor.

[0016] The conversion relationship between batch test results and hydraulic retention time and volume in the reaction zone or reactor is as follows:

[0017] Formula 1

[0018] Among them, BHP is a batch experiment for acid production via hydrolysis, and BMP is a batch experiment for methanogenesis; T BHP In the batch test experiment for acid production by hydrolysis, the time required for the material to hydrolyze and produce acid is expressed in hours (h); T BMP In the methanogenesis batch experiment, HRT1 represents the time required for methanogenesis, in hours (h); HRT2 represents the hydraulic residence time in the reaction zone or reactor during the hydrolysis-to-acidification stage, in hours; HRT2 represents the hydraulic residence time in the reaction zone or reactor during the methanogenesis stage, in hours; V1 represents the volume of the reaction zone or reactor during the hydrolysis-to-acidification stage, in liters (L); V2 represents the volume of the reaction zone or reactor during the methanogenesis stage, in liters (L); X1 and X2 are the volume correction parameters for the configuration of the hydrolysis-to-acidification and methanogenesis reaction zones or reactors, respectively; D is the ratio of the feed concentration of the methanogenesis reactor to the discharge concentration of the hydrolysis-to-acidification stage.

[0019] The material type, fermentation concentration, and material source of the hydrolysis acid production batch experiment and the methanogenesis batch experiment are consistent with those of the material to be used in the two-stage anaerobic fermentation system; the fermentation conditions of the hydrolysis acid production batch experiment and the methanogenesis batch experiment are also consistent with the operating conditions of the two-stage anaerobic fermentation system to be designed; the substrate of the methanogenesis batch experiment BMP in the batch experiment is the fermentation product after the hydrolysis acid production batch experiment BHP is completed.

[0020] Step 2: Calculate the growth and distribution characteristics of functional microorganisms for hydrolysis-acid production and methanogenesis in different types of reactors through microbial growth kinetics calculations, and then determine the characteristics that the reaction zone or reactor to which functional microorganisms for hydrolysis-acid production and methanogenesis should be adapted.

[0021] The microbial growth kinetics calculation model used is as follows:

[0022] Formula 2

[0023] Where, θ c min The average minimum residence time of microbial cells, expressed in days. -1 Y represents cell yield, in g cells / g COD; k represents specific substrate utilization, in mg COD / g VSS / d; K s S0 is the half-saturation constant, in mg COD / L; S0 is the substrate concentration in the influent, in mg COD / L; b is the specific cell decay rate, in d-1. -1 ;

[0024] The kinetic parameters k, Ks, and b are known from existing literature; Y is calculated using the Gibbs free energy of the microbial growth half-reaction equation, with Y for hydrolytic acid-producing microorganisms being 0.03-0.4 (g cells / g COD) and Y for methanogenic microorganisms being 0.01-0.2 (g cells / g COD); the substrate concentration S0 is calculated based on the conversion rate between substrate, intermediate, and final products in the two-stage anaerobic fermentation metabolic pathway, or specific data obtained experimentally or empirically.

[0025] Because the average sludge retention time (SRT) in the reaction zone or reactor is less than θ c min When the average sludge retention time (SRT) is greater than θ, the corresponding microorganisms can grow normally in the reaction zone or reactor; while when the average sludge retention time (SRT) is greater than θ, the corresponding microorganisms can grow normally in the reaction zone or reactor. c min When the corresponding microorganisms are flushed out of the reaction zone or reactor along with the sludge, the reaction zone or reactor with a smaller average sludge retention time (SRT) can meet the normal growth and metabolism of hydrolytic acid-producing microorganisms, while acetic acid-producing and acetic acid-nutritional methanogenic microorganisms are suitable for growth in reaction zones or reactors with a larger average sludge retention time (SRT).

[0026] Step 3: Select the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system, taking into account the actual physical and chemical characteristics and operating environment;

[0027] Step 4: Combine Step 2 and Step 3 to determine the volume correction parameters X1 and X2 for the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor;

[0028] According to step 2, reaction zones or reactors with a smaller average sludge retention time (SRT) can meet the normal growth and metabolism of hydrolytic acid-producing microorganisms, while acetic acid-producing and acetic acid-nutritional methanogenic microorganisms are suitable for growth in reaction zones or reactors with a larger average sludge retention time (SRT).

[0029] Based on the relationship between the average hydraulic retention time (HRT) and the average sludge retention time (SRT) of various anaerobic reactor configurations, anaerobic reactors are classified into conventional anaerobic reactors and high-efficiency anaerobic reactors; among them, conventional anaerobic reactors: 3 > SRT / HRT ≥ 1, and high-efficiency anaerobic reactors: SRT / HRT ≥ 3.

[0030] Based on the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system selected in step 3:

[0031] When a conventional anaerobic reactor is selected as the hydrolysis acid production reaction zone or reactor in a two-stage anaerobic fermentation system, the corresponding volume correction factor X1 should satisfy: X1≥1.

[0032] When a high-efficiency anaerobic reactor is selected as the hydrolysis acid production reaction zone or reactor in a two-stage anaerobic fermentation system, the corresponding volume correction factor X1 should satisfy 1 > X1 > 0.

[0033] When a conventional anaerobic reactor is selected as the reaction zone or reactor for the methanogenic stage of a two-stage anaerobic fermentation system, the corresponding volume correction factor X2 should satisfy X2≥3.

[0034] When a high-efficiency anaerobic reactor is selected as the reaction zone or reactor for the methanogenic stage of a two-stage anaerobic fermentation system, the corresponding volume correction factor X2 should satisfy 0 < X2 < 30.

[0035] Step 5: Combine the material characteristics obtained from the batch test in Step 1 with the reactor configuration selected in Step 3 and the corresponding volume correction parameters obtained in Step 4 to determine the volume parameters of the hydrolysis acid production and methanogenesis reaction zones or reactors in the proposed two-stage anaerobic fermentation system.

[0036] In step 1, the hydrolysis acid production time T in the batch experiment BHP With methanogenesis time T BMP Take 70-85% of the total reaction time to ensure the processing efficiency of the two-stage anaerobic fermentation system during continuous operation.

[0037] In step 1, the operating conditions include, but are not limited to, the inoculum in the reaction zone or reactor, operating temperature, pH, alkalinity, and the content and type of additives.

[0038] In step 1, the operating conditions further include an inoculum pretreatment step, wherein the inoculum pretreatment includes heating pretreatment, acid pretreatment, and alkali pretreatment. In step 1, the 0 <D≤1。

[0039] In step 2, the normal growth and metabolism of microorganisms in the hydrolysis and acid production stage requires the reaction zone or reactor to meet the condition of 36h > SRT ≥ 1.2h; the normal growth and metabolism of microorganisms in the methanogenesis stage requires the reaction zone or reactor to meet the condition of SRT ≥ 36h.

[0040] In step 4, the conventional anaerobic reactor includes a continuous stirred tank reactor, an anaerobic biofilter, and an anaerobic sequencing batch reactor. In step 4, the high-efficiency anaerobic reactor includes an upflow anaerobic sludge blanket reactor, a packed bed reactor, an internal circulation reactor, an expanded granular sludge blanket reactor, and a membrane bioreactor.

[0041] In step 4, the volume correction factor X1 for conventional anaerobic reactors is between 1 and 2, and the volume correction factor X1 for high-efficiency anaerobic reactors is between 0.2 and 1; the volume correction factor X2 for conventional anaerobic reactors is between 10 and 30, and the volume correction factor X2 for high-efficiency anaerobic reactors is between 0.5 and 5.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] Compared to previous design methods and processes for two-stage anaerobic fermentation systems, the design approach proposed in this application requires only simple, small-scale, low-cost, and short-term batch experiments and parameter-based derivation calculations to ensure that the designed two-stage anaerobic reactor conforms to both practical realities and fundamental theories, exhibiting considerable reliability. Therefore, the design approach proposed in this invention significantly reduces the human and material costs associated with conducting numerous experiments or trials to continuously explore and optimize two-stage fermentation systems, and allows for the scientific and rational design of more efficient and stable two-stage anaerobic fermentation systems. Attached Figure Description

[0044] Figure 1 This is a flowchart of the method for determining the volume parameters of the reaction zone or reactor in a two-stage anaerobic system according to the present invention. Detailed Implementation

[0045] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0046] A method for determining the volume parameters of the reaction zone or reactor in a two-stage anaerobic system includes the following steps:

[0047] Step 1: Determine the acid production and methanogenesis characteristics of the material through batch experiments.

[0048] Through small-scale, short-duration batch experiments in the laboratory, the time, lag period, gas production potential, and organic matter removal efficiency required for the actual materials to sequentially complete hydrolysis and methanogenesis in the two-stage fermentation process were determined. Furthermore, the ratio of hydraulic residence time and volume between the hydrolysis-to-acidification reaction zone or reactor and the methanogenesis reaction zone or reactor was determined by the proportional relationship between the material conversion time and the hydraulic residence time or volume of the two-stage anaerobic system reaction zone or reactor.

[0049] The conversion relationship between batch test results and hydraulic retention time and volume in the reaction zone or reactor is as follows:

[0050] Formula 1

[0051] Among them, BHP is a batch experiment for acid production via hydrolysis, and BMP is a batch experiment for methanogenesis; T BHP In the batch test experiment for acid production by hydrolysis, the time required for the material to hydrolyze and produce acid is expressed in hours (h); T BMPIn the batch test for methane production, T is the time required for methane production, with the unit of h; HRT1 is the hydraulic retention time in the reaction zone or reactor during the hydrolysis and acidogenesis stage, with the unit of h; HRT2 is the hydraulic retention time in the reaction zone or reactor during the methane production stage, with the unit of h; V1 is the volume of the reaction zone or reactor during the hydrolysis and acidogenesis stage, with the unit of L; V2 is the volume of the reaction zone or reactor during the methane production stage, with the unit of L; X1 and X2 are the volume correction parameters for the configurations of the reaction zones or reactors during hydrolysis and acidogenesis and methane production respectively; D is the ratio of the feed concentration of the methane production reactor to the effluent concentration of the hydrolysis and acidogenesis stage.

[0052] The hydrolysis and acidogenesis time T in the batch test BHP And the methane production time T BMP Take 70 - 85% of the complete reaction time to ensure the treatment efficiency when the two-stage anaerobic fermentation system operates continuously. The hydraulic retention times of the hydrolysis and acidogenesis and methane production reaction zones or reactors in the two-stage anaerobic fermentation system and those in the batch test And Are proportional, as shown in Equation 1. However, since different reaction zones or reactor configurations may be selected for the hydrolysis and acidogenesis stage and the methane production stage, the volume correction coefficients X1 and X2 of the reaction zones or reactors themselves need to be considered.

[0053] It should also be noted that the material types, fermentation concentrations, and material sources of the hydrolysis and acidogenesis batch test and the methane production batch test of the present invention are consistent with those of the materials intended for the two-stage anaerobic fermentation system. The fermentation conditions of the hydrolysis and acidogenesis batch test and the methane production batch test are also consistent with the operating conditions of the two-stage anaerobic fermentation system to be designed, and the operating conditions include, but are not limited to, the inoculum of the reaction zone or reactor, operating temperature, pH, alkalinity, additive content and types, etc. According to the operating characteristics of the two-stage anaerobic fermentation system, the substrate of the methane production batch test BMP in the batch test is the fermented product after the hydrolysis and acidogenesis batch test BHP ends. Preferably, the operating conditions further include inoculum pretreatment, and the inoculum pretreatment includes heat pretreatment, acid pretreatment, and alkali pretreatment.

[0054] The volumes of the hydrolysis and acidogenesis reaction zone or reactor and the methane production reaction zone or reactor in the two-stage anaerobic fermentation system are proportional to the hydraulic retention time. Considering that in some specific cases, solid-liquid separation or dilution may be required for the material from the hydrolysis and acidogenesis reaction zone or reactor to the methane production reaction zone or reactor. The ratio of the feed concentration of the methane production stage to the effluent concentration of the hydrolysis and acidogenesis stage is used as the proportionality coefficient D between the hydrolysis and acidogenesis reaction zone or reactor and the methane production reaction zone or reactor in the two-stage system, where 0 < D ≤ 1, making the volume ratio of the reaction zones or reactors between the hydrolysis and acidogenesis stage and the methane production stage more in line with the actual situation.

[0055] Step 2: Calculate the growth and distribution characteristics of functional microorganisms for hydrolysis-acid production and methanogenesis in different types of reactors through microbial growth kinetics calculations, and then determine the characteristics that the reaction zone or reactor to which functional microorganisms for hydrolysis-acid production and methanogenesis should be adapted.

[0056] The microbial growth kinetics calculation model used is as follows:

[0057] Formula 2

[0058] Where, θ c min The average minimum residence time of microbial cells, expressed in days. -1 Y represents cell yield, in g cells / g COD; k represents specific substrate utilization, in mg COD / g VSS / d; K s S0 is the half-saturation constant, in mg COD / L; S0 is the substrate concentration in the influent, in mg COD / L; b is the specific cell decay rate, in d-1. -1 .

[0059] The kinetic parameters k, Ks, and b are known from existing literature; Y is calculated using the Gibbs free energy of the microbial growth half-reaction equation, with Y for hydrolytic acid-producing microorganisms being 0.03-0.4 (g cells / g COD) and Y for methanogenic microorganisms being 0.01-0.2 (g cells / g COD); the substrate concentration S0 can be calculated based on the conversion rate between substrate, intermediate, and final products in the two-stage anaerobic fermentation metabolic pathway, or it can be obtained from experimental or empirical data.

[0060] Because the average sludge retention time (SRT) in the reaction zone or reactor is less than θ c min When the average sludge retention time (SRT) is greater than θ, the corresponding microorganisms can grow normally in the reaction zone or reactor; while when the average sludge retention time (SRT) is greater than θ, the corresponding microorganisms can grow normally in the reaction zone or reactor. c min When this happens, the corresponding microorganisms will be flushed out of the reaction zone or reactor along with the sludge. Therefore, based on the above thermodynamic calculations of microbial growth, it can be seen that reaction zones or reactors with a smaller average sludge retention time (SRT) can meet the normal growth and metabolism of hydrolytic acid-producing microorganisms, while acetic acid-producing and acetic acid-trophic methanogenic microorganisms are suitable for growth in reaction zones or reactors with a larger average sludge retention time (SRT). Preferably, for the normal growth and metabolism of microorganisms in the hydrolytic acid-producing stage, the reaction zone or reactor needs to meet 36 h > SRT ≥ 1.2 h; for the normal growth and metabolism of microorganisms in the methanogenic stage, the reaction zone or reactor needs to meet SRT ≥ 36 h.

[0061] Step 3: Based on the actual physical and chemical characteristics and operating environment, select the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system.

[0062] Step 4: Combine Step 2 and Step 3 to determine the volume correction parameters X1 and X2 for the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor.

[0063] According to step 2, reaction zones or reactors with a smaller average sludge retention time (SRT) can meet the normal growth and metabolism of hydrolytic acid-producing microorganisms, while acetic acid-producing and acetic acid-nutritional methanogenic microorganisms are suitable for growth in reaction zones or reactors with a larger average sludge retention time (SRT).

[0064] Based on the relationship between the average hydraulic retention time (HRT) and average sludge retention time (SRT) of various anaerobic reactor configurations, anaerobic reactors are classified into conventional anaerobic reactors and high-efficiency anaerobic reactors. Specifically, for conventional anaerobic reactors: 3 > SRT / HRT ≥ 1, and for high-efficiency anaerobic reactors: SRT / HRT ≥ 3.

[0065] Preferably, the alternative conventional anaerobic reactors include, but are not limited to, Continuous Stirred Tank Reactor (CSTR), Anaerobic Biological Filter (AF), and Anaerobic Sequencing Batch Reactor (ASBR).

[0066] Preferably, the high-efficiency anaerobic reactor includes, but is not limited to, up-flow anaerobic sludge blanket (UASB), packed bed reactor (PBR), internal circulation reactor (IC), expanded granular sludge bed (EGSB), and membrane bioreactor (MBR).

[0067] Based on the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system selected in step 3:

[0068] When a conventional anaerobic reactor is selected as the hydrolysis acid production reaction zone or reactor in a two-stage anaerobic fermentation system, the corresponding volume correction factor X1 should satisfy: X1≥1.

[0069] When a high-efficiency anaerobic reactor is selected as the hydrolysis acid production reaction zone or reactor in a two-stage anaerobic fermentation system, the corresponding volume correction factor X1 should satisfy 1 > X1 > 0.

[0070] When a conventional anaerobic reactor is selected as the reaction zone or reactor for the methanogenic stage of a two-stage anaerobic fermentation system, the corresponding volume correction factor X2 should satisfy X2≥3.

[0071] When selecting a high-efficiency anaerobic reactor as the reaction zone or reactor for the methanogenic stage of a two-stage anaerobic fermentation system, the corresponding volume correction factor X2 should satisfy 0 < X2 < 30.

[0072] Preferably, the volume correction factor X1 for conventional anaerobic reactors is between 1 and 2, and the volume correction factor X1 for high-efficiency anaerobic reactors is between 0.2 and 1; the volume correction factor X2 for conventional anaerobic reactors is between 10 and 30, and the volume correction factor X2 for high-efficiency anaerobic reactors is between 0.5 and 5.

[0073] Step 5: Combine the material characteristics obtained from the batch test in Step 1 with the reactor configuration selected in Step 3 and the corresponding volume correction parameters obtained in Step 4 to determine the volume parameters of the hydrolysis acid production and methanogenesis reaction zones or reactors in the proposed two-stage anaerobic fermentation system.

[0074] Example 1

[0075] Objective: To determine the configuration and volumetric parameters of the hydrolysis-acidification zone and the methanogenesis zone in an integrated two-stage anaerobic fermentation system for treating molasses wastewater. The system needs to treat 1 m³ of wastewater per day. 3 The wastewater concentration is 5 g COD / L, the organic load requirement is 40 g COD / L / d, and the fermentation temperature is 35-37℃.

[0076] Step 1: Conduct batch experiments on hydrolysis to produce acid and methanogens using honey wastewater. After the acid production batch experiment is completed, continue to use the wastewater for the methanogen production batch experiment.

[0077] The organic matter concentration of the honey wastewater used in the batch experiments was 5 g COD / L. The hydrolysis acid production batch experiments were conducted at a temperature of 35-37℃, and the pH was adjusted to 4.5-6.5. After the hydrolysis acid production batch experiments, the aqueous phase used for the methanogenesis batch experiments had an organic matter concentration of 4 g COD / L. The methanogenesis experiment was conducted at a temperature of 35-37℃, and the pH was 6.5-8.5.

[0078] The hydrolysis-induced acid production and methanogenesis batch experiments showed that the time required for complete hydrolysis and acid production of the honey wastewater was 12 hours, and the time required for complete methanogenesis in the aqueous phase was 96 hours. Taking 80% of the maximum time required for hydrolysis-induced acid production and methanogenesis as the design value, the following results were obtained: Then, based on the batch test results, estimate the HRT ratio and volume ratio between the hydrolysis acid production zone and the methanogenesis zone. This is derived from the results obtained in step 1. , can be obtained .

[0079] Step 2: Calculate the growth and distribution characteristics of functional microorganisms for hydrolysis-acid production and methanogenesis in different types of reactors through microbial growth kinetics calculations, and then determine the characteristics that the reaction zone or reactor to which functional microorganisms for hydrolysis-acid production and methanogenesis should be adapted.

[0080] Based on the results of microbial growth kinetic calculations, the structural characteristics of the hydrolysis-acid-producing and methanogenic reaction zones, respectively, were determined. Reaction zones with smaller HRT and SRT can meet the normal growth and metabolism needs of hydrolysis-acid-producing microorganisms, while acetogenic and acetyltrophic methanogenic microorganisms are best suited for growth in reaction zones with larger HRT and SRT.

[0081] Step 3: Based on the actual physical and chemical characteristics and operating environment, select the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system.

[0082] Among the known conventional anaerobic reactors and high-efficiency anaerobic reactors, packed bed PBR was selected as the hydrolysis and acid production reaction zone of the two-stage anaerobic fermentation system, and upflow anaerobic sludge blanket (UASB) was selected as the methanogenesis reaction zone of the two-stage anaerobic system.

[0083] Step 4: Combine Step 2 and Step 3 to determine the volume correction parameters X1 and X2 for the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor.

[0084] Since both packed bed PBR and upflow sludge blanket UASB are high-efficiency anaerobic reactors, we take X1=0.5 and X2=1.

[0085] Step 5: Combine the material characteristics obtained from the batch test in Step 1 with the reactor configuration selected in Step 3 and the corresponding volume correction parameters obtained in Step 4 to determine the volume parameters of the hydrolysis acid production and methanogenesis reaction zones or reactors in the proposed two-stage anaerobic fermentation system.

[0086] Based on the configuration of the hydrolysis acid production reaction zone and the methanogenesis reaction zone selected in step 3, the proportional relationship obtained in step 1, and the corresponding volume correction parameters obtained in step 4, the volume ratio of the hydrolysis acid production reaction zone and the methanogenesis reaction zone in the two-stage anaerobic fermentation system is finally determined.

[0087] Since this is an integrated anaerobic fermentation system, solid-liquid separation and dilution are not considered, therefore D=1. In summary, the volumes V1 (hydrolysis acid production zone) and V2 (methanogenesis zone) in this two-stage anaerobic fermentation system should satisfy the following conditions: .

[0088] Based on the influent flow rate, influent concentration, and the target organic load of 40 g COD / L / d for the proposed integrated two-stage anaerobic fermentation system, the total volume of the system is determined to be 125 L. Therefore, from It can be known that the volume of the hydrolysis acid production reaction zone in the reverse fermentation system is V1 = 25 L, and the volume of the methanogenesis reaction zone is V2 = 100 L.

[0089] Example 2

[0090] Objective: To determine the volumetric parameters of the hydrolysis-acidification stage reactor and the methanogenesis stage reactor in a two-stage anaerobic reactor system for treating food waste. The system needs to process 100 kg of food waste per day (main properties are shown in Table 1), and the organic loading of the hydrolysis-acidification stage needs to reach 17.5 kg VS / m³. 3 / d, operating temperature is 35-37℃.

[0091] Table 1. Main characteristics of the food waste to be treated

[0092] parameter value unit TS 18.5±0.1 % w / w VS 17.5±0.1 % w / w VS / TS 0.92 - TCOD 1.12±0.05 g COD / g VS SCOD 0.31±0.02 g COD / g VSV C / N 21.1 - pH 5.0-6.0 -

[0093] TS: Total solids; VS: Volatile solids; TCOD: Total chemical oxygen demand; SCOD: Soluble chemical oxygen demand

[0094] Step 1: Conduct hydrolysis acid production and methanogenesis batch experiments using the food waste to be treated. The wastewater from the hydrolysis acid production batch experiment is then used for the methanogenesis batch experiment.

[0095] The food waste used in the hydrolysis-induced acid production batch experiment had the same properties as the food waste to be treated by the proposed two-stage anaerobic system (Table 1), with a temperature of 35-37℃ and a pH adjustment of 4.5-6.5. After the hydrolysis-induced acid production batch experiment, an aqueous phase product with a VS of 14% w / w (SCOD of 0.58±0.03 g COD / g VS) was used in the methanogenesis batch experiment, with a temperature of 35-37℃ and a pH of 6.5-8.5.

[0096] The hydrolysis-induced acid production batch experiments and methanogenesis batch experiments showed that the time required for complete hydrolysis and acid production of this food waste was 36 h, and the time required for complete methanogenesis in the aqueous phase was 720 h. Taking 80% and 70% of the time required for complete hydrolysis and acid production, respectively, as design values, the following results were obtained: Then, based on the results of batch experiments, the HRT ratio and volume ratio between the hydrolysis acid-producing reactor and the methanogenic reactor were estimated. .

[0097] Step 2: Calculate the growth and distribution characteristics of functional microorganisms for hydrolysis-acid production and methanogenesis in different types of reactors through microbial growth kinetics calculations, and then determine the characteristics that the reaction zone or reactor to which functional microorganisms for hydrolysis-acid production and methanogenesis should be adapted.

[0098] Based on the results of microbial growth kinetic calculations, the structural characteristics of hydrolytic acid-producing and methanogenic microorganisms suitable for hydrolytic acid-producing and methanogenic reactors, respectively, were determined. Reactors with smaller HRT and SRT can meet the normal growth and metabolism of hydrolytic acid-producing microorganisms, while acetic acid-producing and acetic acid-nutritional methanogenic microorganisms are suitable for growth in reactors with larger HRT and SRT.

[0099] Step 3: Based on the actual physical and chemical characteristics and operating environment, select the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system.

[0100] Considering the large total trace amount (TS) of food waste, a continuous stirred tank reactor (CSTR) can be selected from known conventional and high-efficiency anaerobic reactors as the hydrolysis acid-producing reactor for this two-stage anaerobic fermentation system, and an upflow sludge blanket reactor (UASB) can be selected as the methanogenic reactor for this two-stage anaerobic system.

[0101] Step 4: Combine Step 2 and Step 3 to determine the volume correction parameters X1 and X2 for the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor.

[0102] The continuous stirred tank reactor (CSTR) is a conventional anaerobic reactor, while the upflow anaerobic sludge blanket reactor (UASB) is a high-efficiency anaerobic reactor. We take X1=1.5 and X2=0.5.

[0103] Step 5: Based on the configuration of the hydrolysis acid-producing reactor and the methanogenic reactor selected in Step 3, the proportional relationship obtained in Step 1, and the corresponding volume correction parameters obtained in Step 4, the volume ratio of the hydrolysis acid-producing reactor and the methanogenic reactor in the two-stage anaerobic fermentation system is finally determined.

[0104] To ensure the normal operation of the methanogenic reactor, solid-liquid separation and dilution of the residue in the hydrolysis-acidification reactor are necessary. Based on the aqueous product concentration (14% VS) obtained after the hydrolysis-acidification batch test, a 10-fold dilution can ensure that the methanogenesis stage is not inhibited due to excessive organic load. Therefore, D = 0.1 is obtained from the concentration ratio before and after dilution. In summary, the volumes V1 and V2 of the hydrolysis-acidification reaction zone and the methanogenesis reaction zone in this two-stage anaerobic fermentation system should satisfy the following... .

[0105] Based on the feed rate, feed concentration, and target organic load of the proposed integrated two-stage anaerobic fermentation system, the reactor volume V1 = 1 m³ for the hydrolysis and acid production stage of the fermentation system is determined. 3 And then according to The volume of the methane-producing reactor in this fermentation system can be calculated to be V2 = 5.91 m³. 3 .

[0106] The above embodiments are for illustrative purposes only, and the scope of protection of this patent is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the methods proposed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this patent should be determined by the claims.

Claims

1. A method of determining a two-stage anaerobic system reaction zone or reactor volume parameter, characterized by: The method comprises the following steps: Step 1, determining the hydrolysis acid production and methanogenesis characteristics of the material through batch experiments; Through small-scale and short-time batch experiments in the laboratory, the time required for the actual material to be used in the two-stage fermentation treatment to complete hydrolysis acid production and methanogenesis, the lag phase, the gas production potential and the organic matter removal efficiency are determined; and then the hydraulic retention time ratio and the volume ratio of the hydrolysis acid production reaction zone or reactor to the methanogenesis reaction zone or reactor are determined according to the proportional relationship between the material conversion time and the hydraulic retention time and the volume of the reaction zone or reactor of the two-stage anaerobic system; The conversion relationship between the batch experiment results and the hydraulic retention time and the volume of the reaction zone or reactor is as follows: Formula 1 wherein BHP is the hydrolysis acidogenesis batch test, BMP is the methanogenesis batch test; T BHP T is the time required for hydrolysis acidogenesis in the hydrolysis acidogenesis batch test, unit: h; BMP T is the time required for methanogenesis in the methanogenesis batch test, unit: h; HRT1 is the hydraulic retention time in the reaction zone or reactor for hydrolysis acidogenesis, unit: h; HRT2 is the hydraulic retention time in the reaction zone or reactor for methanogenesis, unit: h; V1 is the volume of the reaction zone or reactor for hydrolysis acidogenesis, unit: L; V2 is the volume of the reaction zone or reactor for methanogenesis, unit: L; X1 and X2 are the volume correction parameters for the configuration of the reaction zone or reactor for hydrolysis acidogenesis and methanogenesis, respectively; D is the ratio of the feed concentration of the methanogenesis reactor to the effluent concentration of the hydrolysis acidogenesis stage; 0 < D ≤ 1; The material type, fermentation concentration, material source of the hydrolysis acid production batch experiment and the methanogenesis batch experiment are consistent with the material to be used in the two-stage anaerobic fermentation system; the fermentation conditions of the hydrolysis acid production batch experiment and the methanogenesis batch experiment are also consistent with the operating conditions of the two-stage anaerobic fermentation system to be designed; the substrate of the methanogenesis batch experiment BMP in the batch experiment is the fermentation material after the end of the hydrolysis acid production batch experiment BHP; Step 2, the growth distribution characteristics of the functional microorganisms in the hydrolysis acid production process and the methanogenesis process in different types of reactors are calculated through microbial growth kinetics, and then the characteristics required for the reaction zone or reactor adapted to the functional microorganisms in the hydrolysis acid production process and the methanogenesis process are determined; The microbial growth kinetics calculation model used is as follows: Formula 2 where θ c min is the average minimum residence time of the microbial cells, in days -1 ; Y is the cell yield, in g cells / g COD; k is the specific substrate utilization rate, in mg COD / g VSS / d; K s is the half-saturation constant, in mg COD / L; S0 is the substrate concentration in the influent, in mg COD / L; b is the specific cell decay rate, in d -1 ; The kinetic parameters k, Ks and b are known from existing literature; Y is obtained by calculating the Gibbs free energy of the microbial growth half-reaction equation, and the Y of the hydrolysis acid production microorganism is 0.03-0.4, with the unit of g cell / g COD; the Y of the methanogenesis microorganism is 0.01-0.2, with the unit of g cell / g COD; the substrate concentration S0 is calculated according to the conversion rate between the substrates, intermediate products and end products in the metabolic pathway of the two-stage anaerobic fermentation, and can also take specific data obtained from experiments or experience; When the average sludge retention time SRT in the reaction zone or reactor is less than θ c min the corresponding microorganisms can grow normally in the reaction zone or reactor; while when the average sludge retention time SRT is greater than θ c min the corresponding microorganisms will be washed out of the reaction zone or reactor with the sludge. Step 3, the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system is selected in combination with the actual material chemical characteristics and operating environment; Step 4, the volume correction parameters X1 and X2 of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor are determined in combination with step 2 and step 3; According to the relationship between the average hydraulic retention time HRT and the average sludge retention time SRT of various configuration anaerobic reactors, the anaerobic reactor zones are divided into conventional anaerobic reactors and high-efficiency anaerobic reactors; wherein, the conventional anaerobic reactor: 3>SRT / HRT≥1, the high-efficiency anaerobic reactor: SRT / HRT≥3; According to the specific configuration of the hydrolysis acid production reaction zone or reactor and the methanogenesis reaction zone or reactor in the two-stage anaerobic fermentation system selected in step 3: When the conventional anaerobic reactor is selected as the hydrolysis acid production reaction zone or reactor of the two-stage anaerobic fermentation system, the corresponding volume correction coefficient X1 should satisfy: X1≥1; When the high-efficiency anaerobic reactor is selected as the hydrolysis acid production reaction zone or reactor of the two-stage anaerobic fermentation system, the corresponding volume correction coefficient X1 should satisfy: 1>X1>0; When a conventional anaerobic reactor is selected as the reaction zone or reactor of the methanogenesis stage of the two-stage anaerobic fermentation system, the corresponding volume correction coefficient X2 should satisfy X2≥3; When a high-efficiency anaerobic reactor is selected as the reaction zone or reactor of the methanogenesis stage of the two-stage anaerobic fermentation system, the corresponding volume correction coefficient X2 should satisfy 0X2<30; Step 5, combine the material properties obtained in Step 1 with the reactor configuration selected in Step 3 and the corresponding volume correction parameters obtained in Step 4 to determine the volume parameters of the hydrolysis-acid production and methanogenesis reaction zones or reactors in the two-stage anaerobic fermentation system. In Step 1, the acid production time T in batch experiment BHP With the methane production time T BMP Take 70-85% of the complete reaction time to ensure the processing efficiency of the two-stage anaerobic fermentation system in continuous operation.

2. The method of determining two-stage anaerobic system reaction zone or reactor volume parameters according to claim 1, wherein: In Step 1, the operating conditions include but are not limited to reactor inoculum, operating temperature, pH, alkalinity, additive content and type.

3. The method of determining two-stage anaerobic system reaction zone or reactor volume parameters according to claim 2, wherein: In Step 1, the operating conditions also include inoculum pretreatment, wherein the inoculum pretreatment includes heating pretreatment, acid pretreatment and alkali pretreatment.

4. The method of determining two-stage anaerobic system reaction zone or reactor volume parameters according to claim 1, wherein: In Step 2, the hydrolysis-acid production stage microorganisms require a reaction zone or reactor for normal growth and metabolism to satisfy 36h>SRT≥1.2h; the methanogenesis stage microorganisms require a reaction zone or reactor for normal growth and metabolism to satisfy SRT≥36h.

5. The method of determining two-stage anaerobic system reaction zone or reactor volume parameters according to claim 1, wherein: In Step 4, the conventional anaerobic reactor includes a continuous stirred tank reactor, an anaerobic biofilter and an anaerobic sequencing batch reactor.

6. The method of determining two-stage anaerobic system reaction zone or reactor volume parameters according to claim 1, wherein: In Step 4, the high-efficiency anaerobic reactor includes an upflow anaerobic sludge bed, a packed bed reactor, an internal circulation reactor, an expanded granular sludge bed and a membrane bioreactor.

7. The method of determining two-stage anaerobic system reaction zone or reactor volume parameters according to claim 1, wherein: In Step 4, the volume correction coefficient X1 of the conventional anaerobic reactor is between 1 and 2, and the volume correction coefficient X1 of the high-efficiency anaerobic reactor is between 0.2 and 1; the volume correction coefficient X2 of the conventional anaerobic reactor is between 10 and 30, and the volume correction coefficient X2 of the high-efficiency anaerobic reactor is between 0.5 and 5.

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