Method for improving quality of anaerobic granular sludge

Abstract

The invention provides a method for improving the quality of anaerobic granular sludge, which comprises the following steps: protein substance production wastewater is treated in an anaerobic reactor, the ascending velocity of the anaerobic reactor is 2.5 m / h-3. 5m / h, and the load of the anaerobic reactor is 8-10kgCOD / md; when the COD removal rate of the anaerobic reactor reaches 80% or the COD concentration of the effluent of the anaerobic reactor is lower than 2000 mg / L, ferrite is added into the inlet water of the reactor, the ascending velocity of the anaerobic reactor is adjusted to be 3.5 m / h to 5 m / h, treatment is continued, and anaerobic sludge is obtained. According to the method provided by the invention, the flow rates of different treatment stages are adjusted, and the ferrite has a synergistic effect, so that the anaerobic sludge particles with a relatively high effective particle proportion are obtained on the basis of loose requirements on water inlet suspended matters, and the quality of the anaerobic sludge particles produced from the protein substance production wastewater is improved.

Description

[0001] This application claims the priority of the Chinese patent application filed with the State Intellectual Property Office of China on March 29, 2024, with application number 202410378667.9 and invention name “A method for improving the quality of anaerobic granular sludge”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of chemical product processing, and in particular to a method for improving the quality of anaerobic granular sludge. Background Art

[0003] Anaerobic sludge plays an important role in sewage treatment. It is mainly used to treat organic pollutants and reduce the content of inorganic components such as nitrogen and phosphorus. The anaerobic granular sludge currently sold on the market is generally produced by anaerobic treatment of industrial wastewater such as fructose syrup, citric acid, and papermaking. It has the characteristics of high particle size and black and bright color. However, the anaerobic granular sludge produced from soy protein production wastewater has a low effective particle ratio and poor quality. Summary of the invention

[0004] In view of this, the present invention provides a method for improving the quality of anaerobic granular sludge, which can effectively increase the effective particle ratio of anaerobic granular sludge produced from protein production wastewater, thereby improving its overall quality.

[0005] The present application provides a method for improving the quality of anaerobic granular sludge, comprising the following steps: Treating the protein production wastewater in an anaerobic reactor, wherein the anaerobic reactor has an upward flow rate of 2.5 m / h to 3.5 m / h and an anaerobic reactor load of 8 to 10 kg COD / m•d; When the COD removal rate of the anaerobic reactor reaches 80% or the COD concentration of the effluent from the anaerobic reactor is lower than 2000 mg / L, ferrous salt is added and the rising flow rate of the anaerobic reactor is adjusted to 3.5 m / h~5 m / h, and the treatment is continued to obtain anaerobic sludge.

[0006] In some specific implementations, before treating the protein production wastewater in the anaerobic reactor, the method further includes: subjecting the protein production wastewater to hydrolysis and acidification treatment.

[0007] In some specific implementations, the COD concentration of the protein production wastewater is 8000 mg / L ~20000 mg / L, the volatile fatty acid is 30 mmol / L ~50 mmol / L, and the pH value is 3.5~5.5.

[0008] In some specific implementations, the processing temperature of the anaerobic reactor is 35° C. to 38° C., the pH value is 6.8 to 7.5, the volatile fatty acid is 0 to 5 mmol / L, and the alkalinity is greater than 25 mmol / L.

[0009] In some specific implementations, the ferrous salt is selected from ferrous sulfate or ferrous chloride.

[0010] In some specific implementations, the amount of ferrous salt added is 100-200 mg / L of wastewater calculated as ferrous sulfate heptahydrate.

[0011] In some specific implementations, the amount of ferrous salt added is 20-40 mg / L of wastewater in terms of iron element. In some specific implementations, ferrous salt is added to the influent water of the anaerobic reactor.

[0012] In some specific implementations, the continued treatment is specifically continued culturing for 20 days to 30 days.

[0013] The method for improving the quality of anaerobic granular sludge provided in the present application comprises the following steps: treating the wastewater produced by protein substances in an anaerobic reactor, wherein the rising flow rate of the anaerobic reactor is 2.5m / h~3.5m / h, and the load of the anaerobic reactor is 8~10kgCOD / m•d; when the COD removal rate of the anaerobic reactor reaches 80% or the COD concentration of the effluent of the anaerobic reactor is lower than 2000mg / L, ferrous salt is added, and the rising flow rate of the anaerobic reactor is gradually adjusted to 3.5m / h~5m / h, and the treatment is continued to obtain the anaerobic sludge. The method provided in the present application adopts the synergistic effect of adjusting the flow rate and ferrous salt in different treatment stages, and obtains anaerobic sludge particles with a high proportion of effective particles without removing suspended matter in the wastewater in advance, thereby improving the quality of anaerobic sludge particles produced by the wastewater produced by protein substances. In addition, the method provided in the present application does not need to be mixed with other wastewaters such as fructose wastewater, and there will be no problems such as sludge loss and reduced granular sludge amount, and it is not limited by the source of fructose wastewater. DETAILED DESCRIPTION

[0014] It should be understood that the expression "one or more of..." includes each of the items recited after the expression individually and in various different combinations of two or more of the recited items, unless otherwise understood from the context and usage. The expression "and / or" in combination with three or more recited items should be understood to have the same meaning, unless otherwise understood from the context.

[0015] The use of the terms "comprising", "having" or "containing", including their grammatical synonyms, should generally be understood as open and non-restrictive, for example not excluding other unrecited elements or steps, unless otherwise specifically stated or otherwise understood from the context.

[0016] It should be understood that the order of steps or the order in which certain actions are performed is not important as long as the present invention remains operable. In addition, two or more steps or actions may be performed simultaneously.

[0017] The use of any and all examples or exemplary language, such as "for example" or "including", herein is intended only to better illustrate the invention and does not limit the scope of the invention unless otherwise claimed. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the invention.

[0018] In addition, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as accurately as possible. However, any numerical value inherently inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise expressly stated, it should be understood that all ranges, quantities, values ​​and percentages used in this disclosure are modified by "about". Here, "about" generally means that the actual value is within plus or minus 10%, 5%, 1% or 0.5% of a specific value or range.

[0019] The present application provides a method for improving the quality of anaerobic granular sludge, comprising the following steps: Treating the protein production wastewater in an anaerobic reactor, wherein the anaerobic reactor has an upward flow rate of 2.5 m / h to 3.5 m / h and an anaerobic reactor load of 8 to 10 kg COD / m•d; When the COD removal rate of the wastewater reaches 80% or the COD concentration of the anaerobic reactor effluent is lower than 2000 mg / L, ferrous salt is added, and the upward flow rate of the anaerobic reactor is adjusted to 3.5 m / h~5 m / h, and the treatment is continued to obtain the anaerobic sludge.

[0020] The present application uses protein production wastewater as raw material to prepare anaerobic sludge particles, and the protein production wastewater is preferably soy protein production wastewater. In some typical implementations, the COD concentration of the protein production wastewater is 8000 mg / L ~20000 mg / L, the volatile fatty acid is 30 mmol / L ~50mmol / L, and the pH value is 3.5~5.5. In some typical implementations, the COD concentration of the protein production wastewater is 10000 mg / L ~18000 mg / L, the volatile fatty acid is 35 mmol / L ~45mmol / L, and the pH value is 4~5.

[0021] This application does not require flocculation treatment in advance when the suspended matter content of protein production wastewater is lower than 2500mg / L, and directly feeds it into the hydrolysis acidification tank of the anaerobic reactor. If the suspended matter content is higher than 2500mg / L, it only needs to be treated to below 2500mg / L. The applicant has found that adding too much flocculant to flocculate suspended particles in wastewater is not only costly, but also causes side effects to the anaerobic reactor due to the use of chemicals. Therefore, the applicant considers using other methods to achieve the effect of flocculation treatment while reducing the impact of chemical addition.

[0022] The applicant found that appropriately increasing the rising flow rate of the anaerobic reactor helps to improve the particle size index of the anaerobic granular sludge, but the improvement effect is limited and needs to be controlled within a certain range to have a positive effect. The experimental results show that when no flocculation treatment is performed in advance, 3.5m / h is the optimal rising flow rate, and the index is close when the rising flow rate is 2.6m / h. When the rising flow rate is lower than 2.6m / h, it is easy to cause uneven water distribution and granular mud to carry flocculent suspended matter. When the rising flow rate is greater than 5m / h, a large amount of granular sludge flows out with the reactor effluent, is broken up by the circulation pump and returns to the anaerobic reactor, causing the sludge quality to decline. Based on this, the present application directly treats the protein production wastewater in the anaerobic reactor, and controls the inlet flow rate and circulation flow rate to make the rising flow rate of the anaerobic reactor 2.5m / h~3.5m / h, and the load of the anaerobic reactor is 8~10kgCOD / m·d. In some specific implementations, the rising flow rate of the anaerobic reactor is 2.8 m / h~3.5 m / h, and the load of the anaerobic reactor is 8.5~9 kgCOD / m·d.

[0023] In some specific implementations, the processing temperature of the anaerobic reactor is 35°C to 38°C, the pH value is 6.8 to 7.5, the volatile fatty acid is 0 to 5 mmol / L, and the alkalinity is greater than 25 mmol / L. In some specific implementations, the processing temperature of the anaerobic reactor is 35°C to 38°C, the pH value is 7 to 7.2, the volatile fatty acid is 0 to 3 mmol / L, and the alkalinity is greater than 30 mmol / L.

[0024] In some specific implementations, the wastewater is preferably subjected to hydrolysis and acidification treatment in a hydrolysis and acidification tank before entering the anaerobic reactor for treatment. The present application has no special restrictions on the hydrolysis and acidification treatment, and the process conditions well known to those skilled in the art can be used.

[0025] Under the above conditions, when the COD removal rate of the anaerobic reactor reaches 80% or the COD concentration of the anaerobic reactor effluent is lower than 2000mg / L, ferrous salt is added to the reactor inlet water, and the rising flow rate of the anaerobic reactor is gradually increased so that the effluent contains a small amount of flocculent suspended matter, but does not contain sludge particles, until the rising flow rate of the anaerobic reactor is 3.5m / h~5m / h, and the treatment is continued to obtain anaerobic sludge. Specifically, under the above conditions, ferrous salt can be added when the wastewater COD removal rate is maintained above 80% or the anaerobic reactor effluent COD concentration is stably lower than 2000mg / L. If the above conditions are not met, the addition of ferrous salt will increase the treatment load of the anaerobic reactor and affect the reactor treatment efficiency. At the same time, too many pollutants will consume more ferrous salt, resulting in a decrease in the addition effect and a waste of ferrous salt. Ferrous salts can generate black ferrous sulfide in an anaerobic environment, which can change the color of anaerobic granular sludge, thereby improving the appearance quality of anaerobic granular sludge, and fully react with flocculent suspended matter in wastewater to form flocculation, promote the separation of flocculent suspended matter and granular sludge, and further increase the effective particle ratio of anaerobic granular sludge. In some specific implementation methods, the continued treatment is specifically to continue to culture for 20 days to 30 days.

[0026] In some specific implementations, the ferrous salt is selected from ferrous sulfate or ferrous chloride, preferably ferrous chloride. In some specific implementations, the amount of the ferrous salt added is 100 mg / L wastewater to 200 mg / L wastewater in terms of ferrous sulfate heptahydrate, preferably 120 mg / L wastewater to 180 mg / L wastewater. Alternatively, the amount of the ferrous salt added is 20 mg / L wastewater to 40 mg / L wastewater in terms of iron element, preferably 24 mg / L wastewater to 30 mg / L wastewater. In some specific implementations, the ferrous salt is mixed with the wastewater in advance and then enters the anaerobic reactor, i.e., is added to the reactor inlet water. In some specific implementations, the ferrous salt can also be directly added to the hydrolysis acidification tank.

[0027] The applicant has found that after adding ferrous salts, further increasing the rising flow rate of the anaerobic reactor can further improve the quality of anaerobic sludge. In some specific implementations, after adding ferrous salts, the rising flow rate of the anaerobic reactor is gradually increased, so that the effluent contains a small amount of flocculent suspended matter, but does not contain sludge particles, until the rising flow rate of the anaerobic reactor is 3.5m / h~5m / h, preferably 4m / h~5m / h, and after 20~30 days of cultivation, preferably 30 days, high-quality anaerobic granular sludge can be obtained.

[0028] It is understood that after adding ferrous salt and adjusting the rising flow rate, other parameters and conditions of the anaerobic reactor remain unchanged, for example, the processing temperature of the anaerobic reactor is 35°C~38°C, the pH value is 6.8~7.5, the volatile fatty acid is 0~5mmol / L, and the alkalinity is greater than 25mmol / L. In some specific implementations, the processing temperature of the anaerobic reactor is 35°C~38°C, the pH value is 7~7.2, the volatile fatty acid is 0~3mmol / L, and the alkalinity is greater than 30mmol / L.

[0029] The method provided by the present application adopts the synergistic effect of adjusting the flow rate and ferrous salt in different treatment stages, and on the basis of the allowable concentration range of suspended matter in the wastewater ≤2500mg / L, the ferrous salt is used to fully react with the flocculent suspended matter in the wastewater to form a flocculation effect, promote the separation of flocculent suspended matter and granular sludge, and further improve the effective particle ratio of anaerobic granular sludge, thereby improving the quality of anaerobic sludge particles produced by protein production wastewater. In addition, the method provided by the present application does not need to be mixed with other wastewaters such as fructose wastewater, and there will be no problems such as sludge loss and reduction in the amount of granular sludge. It is not limited by the source of fructose wastewater, and there is no need to make a large number of modifications to existing equipment, which has little impact on operating costs.

[0030] It can be understood by those skilled in the art that the present application can also mix different types of wastewater in a certain proportion, such as mixing a part of fructose wastewater. When fructose wastewater and protein wastewater are mixed into the water, the sedimentation of some flocculent mud decreases, so that flocculent mud and broken sludge are eliminated, and the quality of the remaining anaerobic granular sludge is improved to a certain extent. However, if the proportion of fructose wastewater is too high, it is easy to cause the sedimentation of flocculent mud to decrease, and the suspended solids in the effluent increase, thereby causing sludge loss and a decrease in the amount of granular sludge. In some specific implementations, the optimal ratio of fructose wastewater to protein wastewater is 1:3, that is, fructose wastewater accounts for 25% of the total influent.

[0031] The experimental results show that the effective particle ratio of the anaerobic granular sludge prepared by the method provided in the present application is increased from 50% to more than 65%, the effective particle size is maintained below 5 mm, and the volatile solid ratio is maintained above 65%, meeting the T / CBFIA14001-2017 anaerobic granular sludge product standard.

[0032] The present invention will be further described below in conjunction with embodiments:

[0033] Example 1 Provide soybean protein production wastewater with COD concentration of 12000 mg / L ~15000 mg / L, volatile fatty acids of 40 mmol / L ~45mmol / L, and pH value of 4~5.

[0034] After the above wastewater is treated in the hydrolysis acidification tank, it enters the anaerobic reactor for treatment, and the inlet flow rate and the circulation flow rate are controlled to make the anaerobic reactor rise velocity 3.5m / h, and the inlet flow rate is further adjusted to make the anaerobic reactor load 9kgCOD / m•d, and the treatment temperature of the anaerobic reactor is maintained at 35℃~38℃, the pH value is 6.8~7.5, the volatile fatty acid is less than 5mmol / L, and the alkalinity is greater than 25mmol / L to treat the wastewater; When the COD removal rate of the wastewater reaches 80% or the COD concentration of the anaerobic reactor effluent is lower than 2000mg / L, add about 150mg / L of ferrous chloride calculated as ferrous sulfate heptahydrate to the influent, and adjust the rising flow rate of the anaerobic reactor to 4m / h. Keep the above conditions and continue the treatment until the effluent contains a small amount of flocculent suspended matter but no sludge particles, and high-quality anaerobic granular sludge can be obtained. The obtained anaerobic granular sludge is characterized, and its effective particle ratio is more than 65%, specifically 76%, the average particle size is 2~5mm, specifically 2.7mm, the particles are uniform, complete, black and bright, and all indicators meet the standard requirements.

[0035] Example 2 Provide soybean protein production wastewater with COD concentration of 12000 mg / L ~15000 mg / L, volatile fatty acids of 40 mmol / L ~45mmol / L, and pH value of 4~5.

[0036] After the above wastewater is treated in the hydrolysis acidification tank, it enters the anaerobic reactor for treatment, and the inlet flow rate and the circulation flow rate are controlled to make the anaerobic reactor rise velocity 3.5m / h, and the inlet flow rate is further adjusted to make the anaerobic reactor load 9kgCOD / m•d, and the treatment temperature of the anaerobic reactor is maintained at 35℃~38℃, the pH value is 6.8~7.5, the volatile fatty acid is less than 5mmol / L, and the alkalinity is greater than 25mmol / L. The wastewater is treated under the conditions that the effluent COD concentration is stably less than 2000mg / L; Add about 30 mg / L of ferrous chloride (about 107 mg / L as ferrous chloride tetrahydrate) into the influent, and gradually increase the upward flow rate of the anaerobic reactor so that the effluent contains a small amount of flocculent suspended matter but no sludge particles. Continue the treatment under the above conditions until the upward flow rate of the anaerobic reactor reaches 4 m / h. After 30 days of cultivation, high-quality anaerobic granular sludge can be obtained.

[0037] The obtained anaerobic granular sludge was characterized, and the effective particle ratio was 82%, the average particle size was 2.9 mm, the particles were uniform, complete, and black, and all indicators met the standard requirements.

[0038] Example 3 Provide soybean protein production wastewater with COD concentration of 12000 mg / L ~15000 mg / L, volatile fatty acids of 40 mmol / L ~45mmol / L, and pH value of 4~5.

[0039] After the above wastewater is treated in the hydrolysis acidification tank, it enters the anaerobic reactor for treatment, and the inlet flow rate and the circulation flow rate are controlled to make the anaerobic reactor rise velocity 2.5m / h, and the inlet flow rate is further adjusted to make the anaerobic reactor load 9kgCOD / m•d, and the treatment temperature of the anaerobic reactor is maintained at 35℃~38℃, the pH value is 6.8~7.5, the volatile fatty acid is less than 5mmol / L, and the alkalinity is greater than 25mmol / L. The wastewater is treated under the conditions that the effluent COD concentration is stably less than 2000mg / L; Add about 30 mg / L of ferrous chloride (about 107 mg / L as ferrous chloride tetrahydrate) into the influent, and gradually increase the rising flow rate of the anaerobic reactor so that the effluent contains a small amount of flocculent suspended matter but no sludge particles. Continue the treatment under the above conditions until the rising flow rate of the anaerobic reactor reaches 3.5 m / h. After 30 days of cultivation, high-quality anaerobic granular sludge can be obtained.

[0040] The obtained anaerobic granular sludge was characterized, and the effective particle ratio was 77%, the average particle size was 2.8 mm, the particles were uniform, complete, and black, and all indicators met the standard requirements.

[0041] Example 4 Provide soybean protein production wastewater with COD concentration of 12000 mg / L ~15000 mg / L, volatile fatty acids of 40 mmol / L ~45mmol / L, and pH value of 4~5.

[0042] After the above wastewater is treated in the hydrolysis acidification tank, it enters the anaerobic reactor for treatment, and the inlet flow rate and the circulation flow rate are controlled to make the anaerobic reactor rise velocity 3m / h, and the inlet flow rate is further adjusted to make the anaerobic reactor load 9kgCOD / m•d, and the treatment temperature of the anaerobic reactor is maintained at 35℃~38℃, the pH value is 6.8~7.5, the volatile fatty acid is less than 5mmol / L, and the alkalinity is greater than 25mmol / L. The wastewater is treated under the conditions that the effluent COD concentration is stably less than 2000mg / L; Add about 30 mg / L of ferrous chloride (about 107 mg / L as ferrous chloride tetrahydrate) into the influent, and gradually increase the rising velocity of the anaerobic reactor so that the effluent contains a small amount of flocculent suspended matter but no sludge particles. Continue the treatment under the above conditions until the rising velocity of the anaerobic reactor reaches 5 m / h. After 30 days of cultivation, high-quality anaerobic granular sludge can be obtained.

[0043] The obtained anaerobic granular sludge was characterized, and the effective particle ratio was 75%, the average particle size was 3.2 mm, the particles were uniform and black and shiny, and a small amount of sludge was broken but it did not affect the overall quality. All indicators met the standard requirements.

[0044] Comparative Example 1 Provide soybean protein production wastewater with COD concentration of 12000 mg / L ~15000 mg / L, volatile fatty acids of 40 mmol / L ~45mmol / L, and pH value of 4~5.

[0045] After the above wastewater is treated in the hydrolysis acidification tank, it enters the anaerobic reactor for treatment, and the inlet flow rate and the circulation flow rate are controlled to make the anaerobic reactor rise velocity 2m / h, and the inlet flow rate is further adjusted to make the anaerobic reactor load 9kgCOD / m•d, and the treatment temperature of the anaerobic reactor is maintained at 35℃~38℃, the pH value is 6.8~7.5, the volatile fatty acid is less than 5mmol / L, and the alkalinity is greater than 25mmol / L. The wastewater is treated under the conditions that the effluent COD concentration is stably less than 2000mg / L; Add about 30 mg / L of ferrous chloride (about 107 mg / L as ferrous chloride tetrahydrate) into the influent, and gradually increase the rising flow rate of the anaerobic reactor so that the effluent contains a small amount of flocculent suspended matter but no sludge particles. Continue the treatment under the above conditions until the rising flow rate of the anaerobic reactor reaches 3 m / h. After 30 days of cultivation, high-quality anaerobic granular sludge can be obtained.

[0046] The obtained anaerobic granular sludge was characterized, and the effective particle ratio was 64%, the average particle size was 2.2 mm, and the particles were uniform, complete, and black and shiny, but the suspended matter content was high and the effective particle ratio was lower than the standard. Other indicators met the standard requirements.

[0047] Comparative Example 2 Provide soybean protein production wastewater with COD concentration of 12000 mg / L ~15000 mg / L, volatile fatty acids of 40 mmol / L ~45mmol / L, and pH value of 4~5.

[0048] After the above wastewater is treated in the hydrolysis acidification tank, it enters the anaerobic reactor for treatment, and the inlet flow rate and the circulation flow rate are controlled to make the anaerobic reactor rise velocity 4m / h, and the inlet flow rate is further adjusted to make the anaerobic reactor load 9kgCOD / m•d, and the treatment temperature of the anaerobic reactor is maintained at 35℃~38℃, the pH value is 6.8~7.5, the volatile fatty acid is less than 5mmol / L, and the alkalinity is greater than 25mmol / L. The wastewater is treated under the conditions that the effluent COD concentration is stably less than 2000mg / L; Add about 30 mg / L of ferrous chloride (about 107 mg / L as ferrous chloride tetrahydrate) into the influent, and gradually increase the rising velocity of the anaerobic reactor so that the effluent contains a small amount of flocculent suspended matter but no sludge particles, until the rising velocity of the anaerobic reactor reaches 5.5 m / h. Maintain the above conditions and continue the treatment. After 30 days of cultivation, high-quality anaerobic granular sludge can be obtained.

[0049] The obtained anaerobic granular sludge was characterized, and the effective particle ratio was 72%, the average particle size was 2.1 mm, the particles were uniform and shiny black, but there were many broken particles, which had a significant impact on the sensory quality. Other indicators met the standard requirements.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the quality of anaerobic granular sludge, comprising the following steps: Treating protein production wastewater in an anaerobic reactor, wherein the anaerobic reactor has an upward flow rate of 2.5 m / h to 3.5 m / h and an anaerobic reactor load of 8 to 10 kg COD / m·d; When the COD removal rate of the anaerobic reactor reaches 80% or the COD concentration of the effluent from the anaerobic reactor is lower than 2000 mg / L, ferrous salt is added and the rising flow rate of the anaerobic reactor is adjusted to 3.5 m / h~5 m / h, and the treatment is continued to obtain anaerobic sludge.

2. The method according to claim 1, characterized in that Before treating the protein material production wastewater in the anaerobic reactor, the method further includes: subjecting the protein material production wastewater to hydrolysis and acidification treatment.

3. The method according to claim 1 or 2, characterized in that: The COD concentration of the protein production wastewater is 8000 mg / L ~20000 mg / L, the volatile fatty acid is 30 mmol / L ~50 mmol / L, and the pH value is 3.5~5.

5.

4. The method according to claim 3, characterized in that The treatment temperature of the anaerobic reactor is 35° C. to 38° C., the pH value is 6.8 to 7.5, the volatile fatty acid is 0 to 5 mmol / L, and the alkalinity is greater than 25 mmol / L.

5. The method according to claim 4, characterized in that The ferrous salt is selected from ferrous sulfate or ferrous chloride.

6. The method according to claim 5, characterized in that The amount of the ferrous salt added is 100-200 mg / L of wastewater calculated as ferrous sulfate heptahydrate.

7. The method according to claim 5, characterized in that The amount of ferrous salt added is 20-40 mg / L of wastewater in terms of iron element.

8. The method according to claim 1, characterized in that Add ferrous salt into the influent water of the anaerobic reactor.

9. The method according to claim 1, characterized in that: The continued treatment specifically includes continuing the culture for 20 to 30 days.