Device and method for biodegradation testing

Abstract

Disclosed are a biodegradation testing apparatus and method, related to the field of environmental protection; and the testing apparatus comprises: a fermentation part, a gas metering part, a gas supply and collection part, and a data processing and process control part; the fermentation part is used for performing biodegradation fermentation; the gas metering part is used for obtaining the volume of gas generated or consumed by fermentation, and measuring the concentration of the gas; the gas supply and collection part supplies / collects gas consumed or generated by microorganisms; and the data processing and process control part is used for collecting reaction process data, and according to the collected data, calculating and storing a test result. A testing method based on the biodegradation testing apparatus provided in the present invention can not only perform anaerobic fermentation, but can likewise perform aerobic fermentation, and has a wide range of applications, is capable of automated real-time monitoring, and can be unattended during operation.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of environmental protection, and in particular to a device and method for biodegradation testing. BACKGROUND

[0002] Microorganisms can degrade and transform organic wastes and pollutants through anaerobic fermentation, aerobic fermentation and other reactions. Therefore, it is of great significance to accurately measure the amount of gas production or oxygen consumption during the process of microbial degradation for studying microbial degradation reaction.

[0003] Anaerobic fermentation technology is one of the effective ways to achieve resource utilization of biomass wastes. Organic matters in organic wastewater, kitchen waste, livestock manure, straw and energy crops and other organic wastes are transformed into biogas. Biogas is a gas mixture, including methane, carbon dioxide, water vapor, hydrogen sulfide, carbon monoxide, hydrogen, nitrogen, ammonia and oxygen, etc. In the existing automatic testing device, biogas is subjected to alkali wash, and the volume of gas after elution is metered as the amount of the methane produced. The existing methods cannot measure both the whole and the individual compositions of the biogas, and thus cannot show the entire process of gas production by anaerobic fermentation microbial degradation in detail. Besides methane, the gases in biogas that cannot be absorbed by alkali liquor also include carbon monoxide, hydrogen, nitrogen, ammonia and oxygen, etc. Therefore, the production of methane is theoretically overestimated in this method.

[0004] In the existing device for anaerobic biodegradation testing, a fermentation bottle with fixed volume for fermentation is mainly used. In the fermentation bottle, a part of headspace volume is usually retained and filled with inert gas (e.g., nitrogen), resulting in overestimation of gas production in the early stage of the fermentation reaction, while the total gas production is underestimated by means of compensation correction calculations. After the start of anaerobic fermentation, the airtightness of the device is difficult to check, and the air leakage is hard to detect in time, which is easy to cause the loss of gas production. The efficiency of absorbing the produced carbon dioxide by heterotopic alkali liquor is quite different, especially in the later stage of fermentation, the efficiency of absorbing the carbon dioxide by the alkali liquor is decreased, leading to a large measurement error. In the existing gas measurement technology, such as gas-liquid displacement method, based on the principle of flipping plate type liquid displacement, when the flipping plate is lifted, the water pressure on the gas in the pipeline decreases, which leads to the escape of some unmeasured gas, resulting in a significant increase in the measurement error.

[0005] The degradation ability of aerobic microorganisms can be measured by the volume of oxygen consumed, the consumption of substrates, or the composition of intermediate products and final products of different microorganisms. The existing aerobic biodegradation testing technology is mainly used to determine the degradation ability of aerobic fermentation microorganisms by indirectly measuring the amount of carbon dioxide produced through the absorption of alkaline substances. The measurement process is complicated, and the accuracy is limited by adsorption efficiency. SUMMARY

[0006] An objective of the present disclosure is to provide a device and method for biodegradation testing, so as to solve the problems mentioned above in the prior art. The device and method for biodegradation testing provided in the present disclosure can conduct not only anaerobic fermentation but also aerobic fermentation, which are wide in applicable range, and capable of achieving automatic real-time monitoring and unattended operation.

[0007] To achieve the objective above, the following technical solution is provided in the present disclosure.

[0008] A device for biodegradation testing includes a fermentation portion, a gas metering portion, a gas supply and collection portion, and a data handling and process control portion. The fermentation portion is configured for biodegradation fermentation. The gas metering portion is configured for obtaining a volume of gas produced or consumed by fermentation, and measuring a concentration of the gas. The gas supply and collection portion is configured for supplying gas consumed by microorganisms or collecting gas produced by microorganisms. The data handling and process control portion is configured for collecting reaction process data, calculating and storing test results according to the data collected.

[0009] Optionally, the fermentation portion includes a constant-temperature water bath, a fermentation bag, and a stirring device. A side of a bottom of the constant-temperature water bath is in communication with a water distributor, an overflow port is arranged on a side of an upper part of the constant-temperature water bath, and the water distributor and the overflow port are in communication with an external heating device through hoses, respectively. The fermentation bag is arranged in the constant-temperature water bath through a tray, an opening is formed at a center of a side of the fermentation bag, and the opening is externally connected with the gas metering portion and the gas supply and collection portion. The stirring device includes a magnetic stirrer arranged in the fermentation bag, and a magnetic base capable of continuously rotating magnetic poles arranged at a center of a bottom of the tray. Fixing clips are arranged on both sides of the tray, and the fermentation bag is installed on the tray through the fixing clips.

[0010] Optionally, the gas metering portion includes a pressure sensor and a gas composition measurement sensor. A connecting rod is fixedly connected at the center of the bottom of the tray, and the connecting rod penetrates through a bottom of the constant-temperature water bath and is fixedly connected with a counterweight block. The pressure sensor is arranged at a bottom of the counterweight block, and a stress surface of the pressure sensor is correspondingly buckled with the counterweight block. The opening is connected with the gas composition measurement sensor and a gas storage container through a discharge pipe in sequence. A valve, which is a check valve, is arranged on an intake pipe.

[0011] Optionally, a telescopic sleeve is arranged at a bottom of the constant-temperature water bath, and the connecting rod is configured to penetrate through the telescopic sleeve and the bottom of the constant-temperature water bath and connected to the counterweight block.

[0012] Optionally, the gas supply and collection portion includes the gas storage container. The gas storage container is a gas collection bag, a discharge pump is arranged on the discharge pipe, and the discharge pump is a gas pump or a peristaltic pump. The gas supply and collection portion further includes a gas supply container, the gas supply container is a gas supply bag, the gas supply bag is in communication with the opening through the intake pipe, a valve and an intake pump are arranged on the intake pipe, the valve is a check valve, and the intake pump is a gas pump or a peristaltic pump. The intake pipe and the discharge pipe are both connected to the opening through a telescopic pipe, a bottom of the telescopic pipe is connected to the opening through a quick connect interface, and a ball is arranged in the quick connect interface.

[0013] Optionally, the data handling and process control portion includes a programmable logic controller (PLC) control system. The PLC control system includes a PLC controller, a data collection module, a display module and a storage module. The PLC controller is connected to the pressure sensor, the gas composition measurement sensor, the magnetic base, the discharge pump, and the intake pump through control lines.

[0014] Optionally, multiple water outlet holes are formed in a part, in the constant-temperature water bath, of the water distributor, and each of the water outlet holes of the water distributor has a diameter less than 1 mm, and is towards the bottom of the constant-temperature water bath. Water in the constant-temperature water bath is purified water with a measured and constant density, and the fermentation bag is immersed in the water bath.

[0015] Optionally, a detection chamber of the gas composition measurement sensor is connected to the discharge pipe, a reflector is arranged at a side of the detection chamber, a transparent plate is arranged at another side of the detection chamber, and a distance between the reflector and the transparent plate is fixed. A probe of the gas composition measurement sensor is not in contact with the gas, thus preventing water vapor in the gas from affecting the gas composition measurement sensor.

[0016] Optionally, a stress surface of the pressure sensor can be tightly buckled with the counterweight block, and a sensitivity of the pressure sensor can be selected according to a fermentation volume or testing requirements, e.g., for a fermentation bag of 1000 mL, the selectivity of the pressure sensor is selected to be accurate to 1 g. The detection chamber of the gas composition measurement sensor is connected to the pipe, the reflector is arranged at the side of the detection chamber, the transparent plate is arranged at another side of the detection chamber, and the distance between the reflector and the transparent plate is fixed. The probe of the sensor is not in contact with the gas, thus preventing water vapor in the gas from affecting the sensor. The PLC controller can set an upper limit value and a lower limit value of the gas production volume which trigger the start and stop of a gas pump and a peristaltic pump, or set the time for the start and stop of the gas pump or the peristaltic pump. The controller can display a curve of gas production with time in real time, and the built-in correction program can automatically replenish the discharged biogas and correct the gas production volume to the volume under standard state.

[0017] The principle of the device for biodegradation testing in the present disclosure is as follow: in an immersion water bath environment, the volume of the fermentation bag changes due to the production / consumption of gas by microbial respiration, and then the buoyancy of the fermentation bag is increased or decreased. Due to the definite relationship between the volume change and the increase or decrease in buoyancy, the volume of the produced / consumed gas can be obtained by converting buoyancy change data measured by the pressure sensor. The PLC controller can automatically start or stop the peristaltic pump periodically according to the set gas production volume range or fermentation time to discharge the biogas from the fermentation bag and transport the biogas into the gas composition test sensor for composition content measurement. The built-in correction program can replenish the discharged biogas volume back to the accumulated gas production volume, and can correct the gas production volume to the gas production volume under the standard state according to the data recorded by the temperature and pressure sensor, thus obtaining curves of the total gas production / consumption volume and the specific composition volume changing with time.

[0018] A method for biodegradation testing is also provided in the present disclosure, which includes:

[0019] turning on an external heating device and setting a required water bath temperature, and delivering water at a set temperature to a constant-temperature water bath;

[0020] loading a prepared fermentation raw material into a fermentation bag, and placing a magnetic stirrer in the fermentation bag, removing air retained in the bag; connecting a quick connect interface of the fermentation bag to a telescopic pipe, turning on the magnetic stirrer and setting a required rotational speed, and turning on a pressure sensor to record a real-time change in a gas production volume;

[0021] setting, by a PLC controller, an upper limit value and a lower limit value of the gas production volume which trigger an intake pump and a discharge pump to start and stop gas supply and discharge, or setting a time interval value between gas supply and discharge, periodically supplying gas in the fermentation bag and discharging gas from the fermentation bag, and measuring gas composition of a gas flowing through a gas composition measurement sensor; and

[0022] collecting and recording, by a PLC control system, data from a barometric pressure sensor, a gravity sensor and the gas composition measurement sensor; calculating, by a built-in program, data of a volume of the gas periodically supplied / discharged, converting the volume of the gas periodically supplied / discharged into a volume under standard state according to a recorded atmospheric pressure to obtain a curve of the volume under standard state changing with fermentation time and a curve of a volume of a certain gas composition changing with fermentation time, thus obtaining changes in gas production rate, methane production rate, and biodegradation rate.

[0023] Optionally, the gas production rate includes a gas production rate Yt at a temperature of 0 °C under a standard atmospheric pressure calculated by means of the following formula, in N mL / g VS or N ml / g COD: y   Pmcasurement'(mCet'P'^+Et—Eq ) 'Tp t “          P-p-g-(T0+T)-VS or y   Pmeasurement'tmVset'P'g+Ft—Eq ) 'Tp t “         P-p-g-(T0+T)-COD wherein: Pmeasurement denotes an atmospheric pressure measured by the barometric pressure sensor, P denotes the standard atmospheric pressure which is 1.01325 *105 Pa;

[0024]

[0025]

[0026]

[0027]

[0028] in kPa;

[0029]

[0030] m denotes a number of times the gas pump / peristaltic pump discharges gas, m>0;

[0031] Vset denotes a set volume of a gas discharged each time, in mL;

[0032] p denotes a density of purified water in the water bath, which is 1 g / mL;

[0033] g denotes a gravity constant, which is 9.8 N / kg;

[0034] Ft denotes a buoyancy calculated by converting a value measured by a pressure sensor at time t, in N;

[0035] Fo denotes a buoyancy calculated from a value measured by the pressure sensor after the fermentation is terminated and biogas is discharged, in N;

[0036] To denotes a Kelvin temperature at 0°C, which is 273.15 K;

[0037] T denotes a fermentation temperature value, such as 37 °C medium temperature fermentation, then T = 37;

[0038] VS denotes volatile solids added to a fermentation system, in g; and

[0039] COD denotes a total chemical oxygen demand of sewage / wastewater added to the fermentation system, in g.

[0040] The methane production rate includes a total volume Vmethane of methane production calculated by means of the following formula, in mL:

[0041] when the number of times the gas pump / peristaltic pump discharges gas is that m= 0,

[0042] when the number of times the gas pump / peristaltic pump discharges gas is that m>l, VCHI = Cm^+cm • v„t p y

[0043] wherein:

[0044] m denotes the number of times the gas pump / peristaltic pump discharges gas, m>0;

[0045] Vset denotes the set volume of the gas discharged each time, in mL;

[0046] p denotes the density of purified water in the water bath, which is 1 g / mL;

[0047] g denotes the gravity constant, which is 9.8 N / kg;

[0048] F denotes the buoyancy calculated by converting the value measured by the pressure sensor at time t, in N;

[0049] Fo denotes the buoyancy calculated from the value measured by the pressure sensor after the fermentation is terminated and biogas is discharged, in N; and

[0050] Cm denotes a methane concentration of the gas discharged by the gas pump / peristaltic pump, measured by the gas composition measurement sensor, in %.

[0051] A methane production rate Ych4 at a temperature of 0 °C under the standard atmospheric pressure is calculated by means of the following formula, in N mL / g VS or N ml / g COD: v    — tQ'vch4'^measurement     \r    _ T0'VCH4'^measurement L J CH4 — VS-P-(TO+T)          CH4 “ COD-P-(To+T)

[0053] wherein:

[0054] Vch4 denotes the total volume of methane production, in mL;

[0055] Pmeasurement denotes the atmospheric pressure measured by the barometric pressure sensor, in kPa;

[0056] P denotes the standard atmospheric pressure which is 1.01325 *105 Pa;

[0057] To denotes the Kelvin temperature at 0°C, which is 273.15 K;

[0058] T denotes the fermentation temperature value, such as 37 °C medium temperature fermentation, then T = 37;

[0059] VS denotes the volatile solids added to the fermentation system, in g; and

[0060] COD denotes the total chemical oxygen demand of sewage / wastewater added to the fermentation system, in g.

[0061] During the calculations of potential for biochemical methane production and specific methanogenic activity of anaerobic sludge, a test result is required to subtract a result of blank control.

[0062] The biodegradation rate includes a total volume of CO2 production calculated by means of the following formula, in mL:

[0063] when the number of times the gas pump / peristaltic pump discharges gas is that m=0,

[0064] when the number of times the gas pump / peristaltic pump discharges gas is that m>l, VCO2 = cm^ + ^cm-vset p y

[0065] wherein:

[0066] m denotes the number of times the gas pump / peristaltic pump discharges gas, m>0;

[0067] Vset denotes the set volume of the gas discharged each time, in mL;

[0068] p denotes the density of purified water in the water bath, which is 1 g / mL;

[0069] g denotes the gravity constant, which is 9.8 N / kg;

[0070] F denotes the buoyancy calculated by converting the value measured by the pressure sensor at time t, in N;

[0071] Fo denotes the buoyancy calculated from the value measured by the pressure sensor after the fermentation is terminated and biogas is discharged, in N;

[0072] Cm denotes a carbon dioxide concentration of the gas discharged by the gas pump / peristaltic pump, measured by the gas composition measurement sensor, in %.

[0073] The biodegradation rate Dt is calculated by means of the following formula:

[0074] Dt =           x 10Q TVcOZ

[0075] wherein:

[0076] Vco2 denotes a total volume of CO2 production measured in a test, in mL;

[0077] VBiank denotes a total volume of CO2 production in the blank control, in mL; and

[0078] TVCO2 denotes a total volume of theoretical CO2 production by complete degradation of a substrate, in mL.

[0079] Compared with the prior art, the device for biodegradation testing in the present disclosure achieves the following beneficial technical effects.

[0080] According to the device for biodegradation testing in the present disclosure, the gas volume is measured in situ in the fermentation bag using the principle of buoyancy, so that underestimation or overestimation of the result caused by ectopic measurement is avoided, and the gas volume can be measured accurately in real time regardless of the speed of gas production / gas consumption. During the process of gas volume measurement and component concentration measurement, there are no removal steps, such as adsorption / elution / condensation / absorption, such that the overestimation or underestimation of the measured value caused by the difference in adsorption / elution / condensation / absorption efficiency is avoided, and the nondestructive measurement is achieved. After measurement, the gas can be collected for further analysis. The fermentation bag is immersed in the water bath all the time, and the airtightness can be checked at any time to ensure that there is no air leakage and no loss of substances throughout the process. For anaerobic fermentation, the present device can achieve the measurement of either biogas, or methane, carbon dioxide and other compositions in biogas. The use of variable-volume fermentation bags can eliminate the influence of the gas retained in the headspace of traditional fermentation tank on the result, allowing the curve of the cumulative gas production to truly restore the gas production process of anaerobic fermentation. For aerobic fermentation, gas is supplied / discharged periodically according to the set time, such that the device has the characteristic of "breathing" and is closer to the natural environmental conditions of microorganism aerobic fermentation.

[0081] The device for biodegradation testing in present disclosure can provide continuous and automatic measurement with high accuracy and high resolution, and can provide favorable assistance for analyzing and studying specific methanogenic activity, biochemical methane production potential, biochemical oxygen demand, microbial respiration and the like during fermentation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] To describe the technical solutions of the embodiments of the present disclosure or in the prior art more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and those skilled in the art may still obtain other drawings from these accompanying drawings without creative efforts.

[0083] FIG. 1 is a schematic diagram of an overall structure of a device for biodegradation testing according to an embodiment of the present disclosure; and

[0084] FIG. 2 shows curves of the cumulative volumes of biogas and methane changing with time during anaerobic fermentation.

[0085] In the drawings: 1 constant-temperature water bath; 2 heating device; 3 water distributor; 4 overflow port; 5 fermentation bag; 6 tray; 7 pressure sensor; 8 connecting rod; 9 quick connect interface; 10 magnetic stirrer; 11 fixing clip; 12 magnetic base; 13 telescopic sleeve; 14 telescopic pipe; 15 discharge pump; 16 floating ball; 17 intake pump; 18 gas composition measurement sensor; 19 PLC control system; 20 control signal line; 21 gas collection bag; 22 gas supply bag; 23 valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0086] The following clearly and completely describes the technical solutions in the embodiments of the present disclosure with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present disclosure. All other embodiments obtained by a person skilled in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.

[0087] An objective of the present disclosure is to provide a device and method for biodegradation testing, so as to solve the problems mentioned above in the prior art. The device and the method for biodegradation testing provided in the present disclosure can conduct not only anaerobic fermentation but also aerobic fermentation, which are wide in applicable range, and capable of achieving automatic real-time monitoring and unattended operation.

[0088] In order to make the objectives, features and advantages of the present disclosure more clearly, the present disclosure is further described in detail below with reference to the accompanying drawings and the embodiments.

[0089] Embodiment 1

[0090] As shown in FIG. 1, a device for biodegradation testing provided in this embodiment mainly includes a fermentation portion, a gas metering portion, a gas supply and collection portion, and a data handling and process control portion. The fermentation portion includes a constant-temperature water bath 1, an external heating device 2, and a fermentation bag 5. A water distributor 3 is arranged at a bottom of the constant-temperature water bath 1, and an overflow port 4 is arranged at a side of a top of the constant-temperature water bath 1. The heating device 2 is in communication with the water distributor 3 and the overflow port 4 of the constant-temperature water bath 1 through hoses, respectively. The gas metering portion includes a tray 6 for fixing the fermentation bag 5, a pressure sensor 7, and a connecting rod 8 for connecting the tray 6 and the pressure sensor 7. A quick connect interface 9 with a valve 23 and a floating ball 16 are arranged at a center of a side of the fermentation bag 5, and a magnetic stirrer 10 is arranged in the bag. Fixing clips 11 are arranged on both sides of the tray 6, and a magnetic base 12 capable of continuously rotating magnetic poles is arranged at a center of the tray 6. A top of the connecting rod 8 is fixedly connected to the center of the tray 6, the connecting rod 8 penetrates through the bottom of the constant-temperature water bath 1 in the middle, and a bottom of the connecting rod 8 is fixedly connected to a counterweight block through the connection of a telescopic sleeve 13. A stress surface of the pressure sensor 7 can be correspondingly buckled with the counterweight block at the bottom of the connecting rod 8. A biogas composition measurement system includes a telescopic pipe 14, and a gas composition measurement sensor 18. The gas supply and collection portion includes a gas collection bag 21, a gas supply bag 22, a valve 23, an discharge pump 15, and an intake pump 17, and is provided with an interface connected to the quick connect interface at an upper part of the fermentation bag through the telescopic pipe. A outlet of the discharge pump 15 is connected to the gas composition measurement sensor 18. A PLC control system 19 and accessory structures thereof include a PLC controller, a data collection module, a display module and a storage module. The PLC controller is connected to the pressure sensor, the magnetic base, a peristaltic pump / gas pump, and the gas composition measurement sensor through control signal lines 20, respectively.

[0091] Embodiment 2

[0092] A method for biodegradation testing provided in this embodiment is as follows.

[0093] The device for biodegradation testing according to Embodiment 1 is used for anaerobic fermentation study, and the fermentation bag with a volume of 500 mL, the pressure sensor with a measuring range of 500 g, a methane component detection probe and a peristaltic pump with a flow rate of 60 mL / m are selected. Specific operation steps includes: Firstly, the external heating device is turned on in advance and set to 37°C, and the purified water at a temperature set to 37°C is delivered to a main water bath. Then, the prepared fermentation raw materials with the anaerobic sludge concentration of 10g VSS / L, the load of 1.0g COD / g VSS and the volume of 300 mL are loaded into the fermentation bag and a magnetic stirrer is placed into the fermentation bag, then a quick connect interface of the fermentation bag is connected to a telescopic pipe. A discharge valve is opened and a peristaltic pump is turned on to remove the air retained in the fermentation bag. The magnetic stirrer is turned on, and the rotational speed of the magnetic stirrer is set to be 120 r / min, and the pressure sensor is turned on to record the real-time change of the gas production volume. The PLC controller is set to read and record the data of the pressure sensor every 15 minutes, and an upper limit value of gas production volume that triggers the peristaltic pump to start discharging is set to be 150 mL, and the lower limit value that triggers the peristaltic pump to stop discharging is set to be 50 mL, and the biogas produced in the fermentation bag is periodically discharged into a methane gas measurement sensor to measure and record the methane content therein. A built-in correction program of the PLC controller is started to replenish the data of gas production volume periodically discharged to the corresponding time period, then the gas production volume is converted into the volume under standard state according to the recorded atmospheric pressure and fermentation temperature to obtain a curve of the gas volume under standard state changing with fermentation time, and according to the content of the certain gas composition recorded by a gas composition detector, a curve of the volume of a certain gas composition changing with fermentation time is obtained, thus obtaining a change in gas production rate. The control experiment is carried out in a methane production potential testing device of a certain brand with a working volume of 500 mL. The produced carbon dioxide is absorbed by ectopic alkali liquor, and methane is measured by the principle of flipping plate type liquid displacement.

[0094] The experimental results are shown in FIG. 2. The device of the present disclosure can completely obtain two sets of data of biogas and methane produced by microorganisms during anaerobic fermentation, and accurately reflect the processes of biogas and methane production by anaerobic fermentation microorganisms. However, in the control group, there is only one set of data of methane produced by microorganisms. The device provided in the present disclosure can measure the whole biogas and methane composition, so that a larger amount of data is obtained to reflect the process of gas production by anaerobic fermentation more comprehensively and accurately. The device in the present disclosure can detect the value produced by the change in the pressure sensor on line in real time, and the data acquisition frequency is set according to time, which is denser and more precise. Although the device of the control group replenishes and corrects the influence of N2 in the headspace of a fermentation bottle, the amount of methane is still overestimated in the early stage of fermentation. In the early stage of fermentation, the proportion of CO2 in biogas is particularly high. When eluted by alkali liquor, a large amount of CO2 is not completely absorbed, leading to the overestimation of methane. In the later stage of fermentation, the cumulative methane measured by the device in the present disclosure is higher than that measured by the device in the control group. The anaerobic fermentation efficiency can be increased by reducing the headspace volume of the fermentation device. The device in the present disclosure can reduce the headspace volume through regular discharge, which is beneficial for increasing the methane yield.

[0095] In the description of the present disclosure, it needs to be understood that the orientation or positional relationship indicated by terms "center", "top", "bottom", "left", "right", "vertical", "horizontal", "inside” and "outside “ is based on the orientation or positional relationship shown in the drawings only for convenience of description of the present disclosure and simplification of description rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus are not to be construed as limiting the present disclosure. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

[0096] Specific examples are used herein for illustration of the principles and implementation methods of the present disclosure. The description of the embodiments is merely used to help illustrate the method and its core principles of the present disclosure. In addition, a person skilled in the art can make various modifications in terms of specific embodiments and scope of application in accordance with the teachings of the present disclosure. In conclusion, the content of this description shall not be construed as a limitation to the present disclosure.

Claims

1. A device for biodegradation testing, comprising a fermentation portion, a gas metering portion, a gas supply and collection portion, and a data handling and process control portion, wherein the fermentation portion is configured for biodegradation fermentation; the gas metering portion is configured for obtaining a volume of gas produced or consumed by fermentation, and measuring a concentration of the gas; the gas supply and collection portion is configured for supplying gas consumed by microorganisms or collecting gas produced by microorganisms; and the data handling and process control portion is configured for collecting reaction process data, calculating and storing test results according to the data collected.

2. The device for biodegradation testing according to claim 1, wherein the fermentation portion comprises a constant-temperature water bath, a fermentation bag, and a stirring device; a side of a bottom of the constant-temperature water bath is in communication with a water distributor, an overflow port is arranged on a side of an upper part of the constant-temperature water bath, and the water distributor and the overflow port are in communication with an external heating device through hoses, respectively; the fermentation bag is arranged in the constant-temperature water bath through a tray, and an opening is formed at a center of a side of the fermentation bag, and the opening is externally connected with the gas metering portion and the gas supply and collection portion; the stirring device comprises a magnetic stirrer arranged in the fermentation bag, and a magnetic base capable of continuously rotating magnetic poles arranged at a center of a bottom of the tray; and fixing clips are arranged on both sides of the tray, and the fermentation bag is installed on the tray through the fixing clips.

3. The device for biodegradation testing according to claim 2, wherein the gas metering portion comprises a pressure sensor and a gas composition measurement sensor; a connecting rod is fixedly connected to the center of the bottom of the tray, the connecting rod penetrates through the bottom of the constant-temperature water bath and is fixedly connected with a counterweight block; the pressure sensor is arranged at a bottom of the counterweight block, and a stress surface of the pressure sensor is correspondingly buckled with the counterweight block; the opening is connected with the gas composition measurement sensor and a gas storage container through a discharge pipe in sequence; and a valve, which is a check valve, is arranged on an intake pipe.

4. The device for biodegradation testing according to claim 3, wherein a telescopic sleeve is arranged at the bottom of the constant-temperature water bath, and the connecting rod is configured to penetrate through the telescopic sleeve and the bottom of the constant-temperature 13water bath and connected to the counterweight block.

5. The device for biodegradation testing according to claim 3, wherein the gas supply and collection portion comprises the gas storage container, the gas storage container is a gas collection bag, an discharge pump is arranged on the discharge pipe, and the discharge pump is an gas pump or a peristaltic pump; the gas supply and collection portion further comprises a gas supply container, the gas supply container is a gas supply bag, the gas supply bag is in communication with the opening through the intake pipe, a valve and an intake pump are arranged on the intake pipe, the valve is a check valve, and the intake pump is an gas pump or a peristaltic pump; and the intake pipe and the discharge pipe are both connected to the opening through a telescopic pipe, a bottom of the telescopic pipe is connected to the opening through a quick connect interface, and a ball is arranged in the quick connect interface.

6. The device for biodegradation testing according to claim 5, wherein the data handling and process control portion comprises a programmable logic controller (PLC) control system; the PLC control system comprises a PLC controller, a data collection module, a display module and a storage module; the PLC controller is connected to the pressure sensor, the gas composition measurement sensor, the magnetic base, the discharge pump, and the intake pump through control lines, respectively.

7. The device for biodegradation testing according to claim 2, wherein a plurality of water outlet holes are formed in a part, in the constant-temperature water bath, of the water distributor, each of the water outlet holes of the water distributor has a diameter less than 1 mm, and is towards the bottom; water in the constant-temperature water bath is purified water with a measured and constant density, and the fermentation bag is immersed in the water bath.

8. The device for biodegradation testing according to claim 3, wherein a detection chamber of the gas composition measurement sensor is connected to the discharge pipe, a reflector is arranged at a side of the detection chamber, a transparent plate is arranged at another side of the detection chamber, and a distance between the reflector and the transparent plate is fixed; and a probe of the gas composition measurement sensor is not in contact with the gas, thus preventing water vapor in the gas from affecting the gas composition measurement sensor.

9. A method for biodegradation testing, comprising:turning on an external heating device and setting a required water bath temperature, and delivering water at a set temperature to a constant-temperature water bath;loading a prepared fermentation raw material into a fermentation bag, and placing a magnetic stirrer in the fermentation bag, removing air retained in the bag; connecting a quickconnect interface of the fermentation bag to a telescopic pipe, turning on the magnetic stirrer and setting a required rotational speed, and turning on a pressure sensor to record a real-time change in a gas production volume;setting, by a PLC controller, an upper limit value and a lower limit value of the gas production volume which trigger an intake pump and a discharge pump to start and stop gas supply and discharge, or setting a time interval value between gas supply and discharge, periodically supplying gas in the fermentation bag and discharging gas from the fermentation bag, and measuring gas composition of a gas flowing through a gas composition measurement sensor; andcollecting and recording, by a PLC control system, data from a barometric pressure sensor, a gravity sensor and the gas composition measurement sensor; calculating, by a built-in program, data of a volume of the gas periodically supplied / discharged, converting the volume of the gas periodically supplied / discharged into a volume under standard state according to a recorded atmospheric pressure to obtain a curve of the volume under standard state changing with fermentation time and a curve of a volume of a certain gas composition changing with fermentation time, thus obtaining changes in gas production rate, methane production rate and biodegradation rate.

10. The method for biodegradation testing according to claim 9, wherein the gas production rate comprises a gas production rate Yt at a temperature of 0 °C under a standard atmospheric pressure calculated by means of the following formula, in N mL / g VS or N ml / g COD:Y _ Pmeasurement■ (mVset ■ p ■ g + Ft — Fo) -Tor               P ■ p ■ g ■ (To + T) ■ VSorY _ Pmeasurement■ (mVset ■ p ■ g + Ft — Fo) -Tot-         P ■ p ■ g ■ (To + T) ■ CODwherein:Pmeasurement denotes an atmospheric pressure measured by the barometric pressure sensor, in kPa;P denotes the standard atmospheric pressure which is 1.01325 *105 Pa;m denotes a number of times a gas pump / peristaltic pump discharges gas, m>0;Vset denotes a set volume of gas discharged each time, in mL;p denotes a density of purified water in the water bath, which is 1 g / mL;g denotes a gravity constant, which is 9.8 N / kg;Ft denotes a buoyancy calculated by converting a value measured by a pressure sensor at time t, in N;Fo denotes a buoyancy calculated from a value measured by the pressure sensor after the fermentation is terminated and biogas is discharged, in N;To denotes a Kelvin temperature at 0°C, which is 273.15 K;T denotes a fermentation temperature value, such as 37 °C medium temperature fermentation, then T = 37;VS denotes volatile solids added in a fermentation system, in g;COD denotes a total chemical oxygen demand of sewage / wastewater added to the fermentation system, in g;the methane production rate comprises a total volume Vmethane of methane production calculated by means of the following formula, in mL:when the number of times the gas pump / peristaltic pump discharges gas is that m= 0,when the number of times the gas pump / peristaltic pump discharges gas is that m>l,P awherein:m denotes the number of times the gas pump / peristaltic pump discharges gas, m>0;Vset denotes the set volume of gas discharged each time, in mL;p denotes the density of purified water in the water bath, which is 1 g / mL;g denotes the gravity constant, which is 9.8 N / kg;F denotes the buoyancy calculated by converting the value measured by the pressure sensor at time t, in N;Fo denotes the buoyancy calculated from the value measured by the pressure sensor after the fermentation is terminated and biogas is discharged, in N;Cm denotes a methane concentration of the gas discharged by the gas pump / peristaltic pump measured by the sensor, in %;a methane production rate Ych4 at a temperature of 0 °C under the standard atmospheric pressure is calculated by means of the following formula, in N mL / g VS or N ml / g COD:YT0'VCH4'^measurement _ \r       T0'VCH4'^measurementru4 — ----------------- OF Yr Li J — -----------------CH4 VS-P-(T0+T)          CH4 COD-P-(To+T)wherein:Vch4 denotes the total volume of methane production, in mL;Pmeasurement denotes the atmospheric pressure measured by the barometric pressure sensor, in kPa;P denotes the standard atmospheric pressure which is 1.01325 *105 Pa;To denotes the Kelvin temperature at 0°C, which is 273.15 K;T denotes the fermentation temperature value, such as 37 °C medium temperature fermentation, then T = 37;VS denotes the volatile solids added to the fermentation system, in g,COD denotes the total chemical oxygen demand of sewage / wastewater added to the fermentation system, in g;during calculations of potential for biochemical methane production and specific methanogenic activity of anaerobic sludge, a test result is required to subtract a result of blank control;the biodegradation rate comprises a total volume of CO2 production calculated by means of the following formula, in mL:when the number of times the gas pump / peristaltic pump discharges gas is that m=0,when the number of times the gas pump / peristaltic pump discharges gas is that m>l,VCO2 = cm^ + ^cm-vset p ywherein:m denotes the number of times the gas pump / peristaltic pump discharges gas, m>0;Vset denotes the set volume of gas discharged each time, in mL;p denotes the density of purified water in the water bath, which is 1 g / mL;g denotes the gravity constant, which is 9.8 N / kg;F denotes the buoyancy calculated by converting the value measured by the pressure sensor at time t, in N;Fo denotes the buoyancy calculated from the value measured by the pressure sensor after the fermentation is terminated and biogas is discharged, in N;Cm denotes a carbon dioxide concentration of the gas discharged by the gas pump / peristaltic pump measured by the sensor, in %;the biodegradation rate Dt is calculated by means of the following formula:Dt(Vc02 ~ V Blank) TV co2x 100wherein:Vco2 denotes a total volume of CO2 production measured in a test, in mL;VBiank denotes a total volume of CO2 production in the blank control, in mL;TVCO2 denotes a total volume of theoretical CO2 production by complete degradation of a substrate, in mL.

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