Resourceful treatment system and method for aquaculture wastewater

Abstract

The invention discloses an aquaculture wastewater treatment and recycling process system which comprises the following steps: S1, feeding aquaculture wastewater into an anaerobic continuous stirring reactor to be mixed with sludge to form a sludge-water mixture, and realizing hydrolysis and acidification of complex organic matters in the aquaculture wastewater and release of phosphate radicals; s2, feeding the mud-water mixture in the S1 into an anaerobic membrane bioreactor to further convert organic matters into biogas, collecting the biogas, and performing solid-liquid separation on the mud-water mixture through a membrane assembly; s3, in the operation process of the reaction system, ferric ions are added into the mud-water mixture, generation of biogas is enhanced, in-situ purification of methane is achieved, and meanwhile blue iron ore is generated and collected. According to the invention, the anaerobic system is utilized to treat the aquaculture wastewater, and synchronous recovery of high-concentration methane and high-value phosphate minerals is realized.

Description

Technical Field

[0001] The present invention belongs to the field of aquaculture wastewater treatment, and in particular relates to a system and method for resource-based aquaculture wastewater treatment. Background Art

[0002] Swine wastewater (SW) is mainly derived from pig urine, breeding and pig house washing wastewater, and is one of the main sources of agricultural pollution. Typical pollutants in SW include 2000-30000 mg COD / L, 110-1650 mg NH 4+ -N / L, 200-2055mg TN / L, 100-620mg TP / L, etc. With the continuous increase in the total amount of livestock and poultry farming, the pressure on the environment is gradually increasing. If these pollutants are directly discharged into the water in large quantities, it will cause abnormal reproduction of algae and plankton, consume dissolved oxygen in the water, cause aquatic animals to die of hypoxia, destroy the ecosystem, and produce black and smelly water bodies. With the gradual expansion of the scale of farming, the aquaculture wastewater has the characteristics of large scale, many types of pollutants and high content. The recyclable resources are very rich, mainly including biomass energy recovery based on biogas and resource recovery based on phosphate rock.

[0003] Anaerobic digestion (AD) treatment process is mostly used in the field of sewage treatment. It usually uses laboratory-scale or pilot-scale wastewater treatment equipment to treat various wastewaters. It can convert complex organic matter in sewage into high calorific value methane fuel through biological hydrolysis, acidification, and methanation. It is currently a generally recognized sewage energy conversion method. As a low-energy biological wastewater treatment technology and its unique economic benefits, the AD process is gradually being valued by society. Therefore, the energy market prospect of using AD to treat aquaculture wastewater is broad, and there is a large market space for biomass energy.

[0004] In addition, phosphorus, as a limited and non-renewable resource, is one of the essential elements for plants and an indispensable substance in emerging industries. It plays an irreplaceable role in industries such as agriculture and lithium batteries. Phosphorus emissions mainly come from agriculture (68.08%), human behavior (29.52%) and industry (2.40%), among which livestock and poultry farming is the main contributor to phosphorus emissions. However, the current livestock and poultry wastewater treatment technology has a low recovery rate for phosphorus resources, and a large amount of phosphorus is ultimately stored in the soil and water environment in various forms. The main products of phosphorus recovery are struvite (MgNH4PO4·6H2O, MAP), hydroxyapatite (Ca 10(PO4)·6(OH)2, HAP) and violet iron ore (Fe3(PO4)2·8H2O, Vivianite), etc. In the international phosphate ore market, the price of unit phosphorus in violet iron ore is about 10,000 euros / ton, far exceeding the value of minerals such as MAP and HAP.

[0005] The AD system is relatively sensitive, and its methane recovery efficiency is affected by factors such as temperature, carbon-nitrogen ratio, organic load shock and heavy metal toxicity. Although the anaerobic digestion biological treatment process has the advantage of energy recovery, most of the existing treatment processes cannot achieve the ideal recovery state, and there are problems such as low COD removal rate and low gas production.

[0006] The continuous stirred tank reactor (CSTR) can completely mix the substrate and sludge, fully contact them, prevent high organic load from impacting the reaction tank, and ensure the smooth progress of the reaction. However, CSTR is a completely mixed reactor that cannot separate the sludge and effluent, which can easily cause sludge loss. The sludge retention time required for AD to treat aquaculture wastewater is relatively long, and improving wastewater treatment efficiency requires reducing the hydraulic retention time. Using only the CSTR process is very likely to cause biomass loss and substandard effluent.

[0007] The current AnMBR system for treating aquaculture wastewater has a low treatment efficiency. The main reason is that the aquaculture wastewater has a high solid content, and the lignin, cellulose, hemicellulose and other substances in the aquaculture wastewater are difficult to degrade, and it is impossible to better realize the recovery of organic matter. The focus is only on converting COD into CH4 for energy recovery, and adding exogenous substances such as biochar can only improve the efficiency of energy recovery and alleviate membrane pollution. However, aquaculture wastewater also contains a large amount of high-quality phosphorus resources. Recycling phosphorus resources from animal manure or other sewage can meet 15-20% of the world's phosphorus demand, and using only AnMBR to treat aquaculture wastewater systems cannot achieve the recovery of phosphorus resources. For this reason, based on the development background of efficient resource recovery and environmental benefits, how to effectively utilize phosphorus in aquaculture wastewater is particularly important. Summary of the invention

[0008] The purpose of the present invention is to provide a system and method for resource treatment of aquaculture wastewater to overcome at least one of the above-mentioned defects in the prior art.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for resource-based treatment of aquaculture wastewater, comprising the following steps S1: feeding the aquaculture wastewater into a continuous stirring reactor, fully mixing the aquaculture wastewater with the sludge inoculated in the continuous stirring reactor to form a mud-water mixture, wherein the organic matter in the aquaculture wastewater is hydrolyzed and acidified, and at the same time, the organic phosphorus and precipitated inorganic phosphorus are converted into phosphate ions; S2: feeding the mud-water mixture formed in step S1 into an anaerobic membrane bioreactor, wherein the organic matter is further converted into biogas, and at the same time, the membrane assembly of the anaerobic membrane bioreactor performs solid-liquid separation on the mud-water mixture to achieve sewage treatment. , S3: During the operation of the reaction system, trivalent iron ions are continuously added to the mud-water mixture. Under the synergistic action of anaerobic microorganisms in the reduction system, the trivalent iron ions are reduced to divalent iron ions; the generated biogas flows back to the anaerobic membrane bioreactor, and while enhancing mass transfer and reducing membrane pollution, the carbon dioxide in the biogas dissolves to form bicarbonate ions, and a part of the divalent iron ions and the bicarbonate ions form ferrous carbonate precipitates, thereby achieving in-situ purification of the biogas and collecting high-concentration methane; the phosphate ions in the mud-water mixture combine with another part of the divalent iron ions to form blue iron ore.

[0011] Preferably, the concentration of added trivalent iron ions is 100-600 mg / L, and the temperature of the mud-water mixture in the anaerobic membrane bioreactor is maintained at 34-37° C. by water bath heating.

[0012] Preferably, before step S3, the method further includes: returning the mud-water mixture of the anaerobic membrane bioreactor to the continuous stirring reactor to maintain the hydrolysis and acidification activities of the microorganisms in the continuous stirring reactor.

[0013] The present invention also provides a system for resource-based treatment of aquaculture wastewater, which is used to implement the above-mentioned method for resource-based treatment of aquaculture wastewater, including a continuous stirring reactor, an anaerobic membrane bioreactor, a mud-water mixture delivery pump, a biogas circulation pipe, and a circulation air pump. A mud-water mixture delivery pump for delivering the mud-water mixture of the continuous stirring reactor into the anaerobic membrane bioreactor is arranged between the continuous stirring reactor and the anaerobic membrane bioreactor. The top of the anaerobic membrane bioreactor is connected to the biogas circulation pipe, the gas outlet end of the biogas circulation pipe is connected to the lower part of the anaerobic membrane bioreactor, and the circulation air pump is connected to the biogas circulation pipe.

[0014] Preferably, it also includes a substrate delivery pipe, a circulating water bath, and a reflux delivery pump. A substrate delivery pipe is arranged between the continuous stirred reactor and the anaerobic membrane bioreactor, the substrate delivery pipe is connected to the circulating water bath, and a reflux delivery pump is arranged between the continuous stirred reactor and the anaerobic membrane bioreactor for returning the mud-water mixture of the anaerobic membrane bioreactor to the continuous stirred reactor.

[0015] Preferably, it also includes a substrate tank, a first agitator, a water inlet pipe, and a substrate delivery pump. The first agitator is arranged in the substrate tank, the substrate tank is provided with a water inlet pipe, and a substrate delivery pump is arranged between the substrate tank and the continuous stirred reactor for delivering the aquaculture wastewater in the substrate tank into the continuous stirred reactor.

[0016] Preferably, the pump speed ratio of the matrix delivery pump, the mud-water mixture delivery pump, and the reflux delivery pump is 1.5-2.5:2.7-3.7:1.

[0017] Preferably, the continuous stirred reactor comprises a first operating tank, a second agitator, a continuous stirred reactor thermostat, a first gas collecting pipe, and a first valve. The second agitator is arranged in the first operating tank, the periphery of the first operating tank is provided with a continuous stirred reactor thermostat, the top of the first operating tank is connected to the first gas collecting pipe, and the first gas collecting pipe is provided with a first valve.

[0018] Preferably, the anaerobic membrane bioreactor includes a second operating tank, a flat membrane assembly, a second gas collecting pipe, a second valve, a third gas collecting pipe, a third valve, an anaerobic membrane bioreactor thermostat, and a gas collecting component. The anaerobic membrane bioreactor thermostat is arranged around the second operating tank, a flat membrane assembly is arranged in the second operating tank, the top of the second operating tank is connected to the second gas collecting pipe and the third gas collecting pipe, the second gas collecting pipe is provided with a second valve, the third gas collecting pipe is provided with a third valve, and the top of the third gas collecting pipe is connected to the gas collecting component.

[0019] Preferably, it also includes a wet gas flow meter, a suction pipe, and a suction pump. The first gas collecting pipe and the second gas collecting pipe are both connected to the wet gas flow meter. The water outlet of the flat membrane assembly is connected to the suction pipe. The suction pipe is provided with a suction pump. The gas outlet end of the biogas circulation pipe is vertically toward the flat membrane assembly. The pore size of the diaphragm of the flat membrane assembly is 0.2-0.3μm. The working volume ratio of the first operating tank and the second operating tank is 1:1.5-2.5.

[0020] The beneficial effects of the present invention are:

[0021] 1. On the basis of the CSTR-AnMBR system for treating aquaculture wastewater, an Fe(III)-CSTR-AnMBR system is formed by adding Fe(III). In this system, Fe(III) is coupled with CSTR-AnMBR, and Fe(III) can combine with CO2 in the circulating biogas to generate FeCO3 precipitation, thereby increasing the methane concentration. Moreover, Fe(III), as a trace element necessary for microorganisms, can enhance their activity and improve the stability of the reactor, thereby achieving long-term stable operation of Fe(III)-CSTR-AnMBR. In addition, under the biological, physical and chemical effects of the AD system, Fe(III) can combine with part of the phosphorus in the aquaculture wastewater to generate high-value vivianite. Combined with the interception effect of the AnMBR membrane assembly, high-concentration vivianite is formed, which is subsequently recovered.

[0022] 2. By controlling the concentration of trivalent iron ions, it can not only strengthen the anaerobic digestion process, but also purify biogas and react with PO4 in aquaculture wastewater. 3- Combined, it produces high-value blue iron ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the aquaculture wastewater resource treatment system of the present invention.

[0024] Figure 2 It is a diagram of the OLR variation at different operation stages of the present invention.

[0025] Figure 3 It is a graph showing changes in daily methane production and specific methane production at different operating stages of the present invention.

[0026] Figure 4 It is a graph showing the changes in CH4 and CO2 content in biogas at different operating stages of the present invention.

[0027] Figure 5 It is a diagram of the changes of VFAs in different operation stages of the present invention.

[0028] Figure 6 It is a graph showing the changes in the removal rates of TP, TFe and P in the inlet and outlet water at different operation stages of the present invention.

[0029] Figure 7 It is a graph showing the change in the utilization rate of Fe in the inlet and outlet water at different operation stages of the present invention.

[0030] Figure 8 It is the XRD spectrum analysis diagram of the sludge in Phase III and VI of the present invention.

[0031] Fig. 9This is a SEM image of the AnMBR sludge in Phase VI of the present invention (blue is the clustered crystal structure, green is the microorganism, and red is the biomass).

[0032] Fig.10 It is the EDS diagram of AnMBR sludge in Phase VI of the present invention.

[0033] The markings in the accompanying drawings are: 1-circulating air pump, 2-biogas circulation pipe, 3-mud-water mixture delivery pump, 4-anaerobic membrane bioreactor, 5-continuous stirred reactor, 6-substrate delivery pipe, 7-circulating water bath, 8-reflux delivery pump, 9-substrate tank, 10-first agitator, 11-water inlet pipe, 13-substrate delivery pump, 51-first operating tank, 52-second agitator, 53-continuous stirring reactor thermostat, 54-first gas collecting pipe, 55-first valve, 41-second operating tank, 42-flat membrane assembly, 43-second gas collecting pipe, 44-second valve, 45-third gas collecting pipe, 46-third valve, 47-gas collecting part, 48-anaerobic membrane bioreactor thermostat, 14-wet gas flowmeter, 15-suction pipe, 16-suction pump. DETAILED DESCRIPTION

[0034] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0035] Contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field. In the description of the present invention, it should be understood that the orientation or position relationship indicated by the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0036] A method for resource-based treatment of aquaculture wastewater provided in this embodiment comprises the following steps:

[0037] S1: Send the aquaculture wastewater into the continuous stirred reactor 5 (CSTR), so that the aquaculture wastewater is fully mixed with the sludge inoculated in the continuous stirred reactor 5 to form a sludge-water mixture. In this embodiment, anaerobic reaction is carried out in the continuous stirred reactor 5. The organic matter in the aquaculture wastewater is hydrolyzed and acidified, and at the same time, the organic phosphorus and precipitated inorganic phosphorus are converted into phosphate ions. The setting of the continuous stirred reactor 5 prevents the excessive organic load from causing an impact on the reaction system, and controls the sludge retention time to ensure the hydrolysis of organic matter.

[0038] S2: The mud-water mixture formed in step S1 is sent to the anaerobic membrane bioreactor 4 (AnMBR), so that the organic matter is further converted into biogas. At the same time, the membrane assembly of the anaerobic membrane bioreactor separates the mud-water mixture into solid and liquid to achieve sewage treatment. AnMBR controls the membrane flux and then the hydraulic retention time to achieve the interception of functional microorganisms and strengthen the anaerobic digestion methanogenesis process.

[0039] The mud-water mixture of the anaerobic membrane bioreactor 4 is returned to the continuous stirring reactor 5 to maintain the hydrolysis and acidification activities of the microorganisms in the continuous stirring reactor.

[0040] S3: During the operation of the reaction system, trivalent iron ions are continuously added to the mud-water mixture. Under the synergistic action of anaerobic microorganisms in the reduction system, the trivalent iron ions are reduced to divalent iron ions. The generated biogas flows back to the anaerobic membrane bioreactor. While strengthening mass transfer and reducing membrane pollution, the carbon dioxide in the biogas dissolves to form bicarbonate ions, and a part of the divalent iron ions and bicarbonate ions form ferrous carbonate precipitation, thereby achieving in-situ purification of biogas and collecting high-concentration methane. The phosphate ions in the mud-water mixture combine with another part of the divalent iron ions to form blue iron ore.

[0041] The concentration of trivalent iron ions added in this embodiment is 300 mg / L, and the temperature of the mud-water mixture in the anaerobic membrane bioreactor is maintained at 37°C by water bath heating. By controlling the concentration of trivalent iron ions added, it can not only strengthen the anaerobic digestion process, but also purify biogas and react with PO4 3- Combined, it produces high-value blue iron ore.

[0042] like Figure 1As shown, the present invention also provides a system for resource-based treatment of aquaculture wastewater, which is used to realize the above-mentioned resource-based treatment method of aquaculture wastewater, including a continuous stirring reactor 5, an anaerobic membrane bioreactor 4, a mud-water mixture delivery pump 3, a biogas circulation pipe 2, and a circulation gas pump 1. A mud-water mixture delivery pump 3 for delivering the mud-water mixture of the continuous stirring reactor 5 to the anaerobic membrane bioreactor 4 is arranged between the continuous stirring reactor 5 and the anaerobic membrane bioreactor 4, the top of the anaerobic membrane bioreactor 4 is connected with a biogas circulation pipe 2, the gas outlet end of the biogas circulation pipe 2 is connected to the lower part of the anaerobic membrane bioreactor 4, and the circulation gas pump 1 is connected to the biogas circulation pipe 2. The aquaculture wastewater is stirred in the continuous stirring reactor 5 so that the sludge and the aquaculture wastewater are fully mixed. The mud-water mixture of the continuous stirring reactor 5 is delivered to the anaerobic membrane bioreactor 4 for treatment by the second delivery pump 3. The biogas produced by the anaerobic membrane bioreactor 4 enters the biogas circulation pipe 2 and is sent to the anaerobic membrane bioreactor 4 through the circulation gas pump 1 to form a circulation, so that the biogas and the anaerobic membrane bioreactor 4 are fully mixed, which is conducive to the formation of bicarbonate ions.

[0043] The substrate delivery pipe 6, the circulating water bath 7, and the reflux delivery pump 8 are also included. The substrate delivery pipe 6 is arranged between the continuous stirring reactor 5 and the anaerobic membrane bioreactor 4. The substrate delivery pipe 6 is connected to the circulating water bath 7. The reflux delivery pump 8 for returning the mud-water mixture of the anaerobic membrane bioreactor 4 to the continuous stirring reactor 5 is arranged between the continuous stirring reactor 5 and the anaerobic membrane bioreactor 4. The reaction temperature of the continuous stirring reactor 5 and the anaerobic membrane bioreactor 4 is maintained at 37°C by the arrangement of the substrate delivery pipe 6 and the circulating water bath 7. The reflux delivery pump 8 returns the mud-water mixture of the anaerobic membrane bioreactor 4 to the continuous stirring reactor 5, and cooperates with the mud-water mixture delivery pump 3 to achieve full mixing of the sludge in the continuous stirring reactor 5 and the anaerobic membrane bioreactor 4, and maintain the activity of the microorganisms in the continuous stirring reactor.

[0044] The method further comprises a substrate tank 9, a first agitator 10, a water inlet pipe 11, and a substrate delivery pump 13. The first agitator 10 is arranged in the substrate tank 9, the substrate tank 9 is provided with a water inlet pipe 11, and a substrate delivery pump 13 is arranged between the substrate tank 9 and the continuous stirring reactor 5 for delivering the aquaculture wastewater in the substrate tank 9 to the continuous stirring reactor 5. The aquaculture wastewater first enters the substrate tank 9, and the aquaculture wastewater is uniformly mixed by the first agitator 10 to prevent large particles from sinking to the bottom. The aquaculture wastewater enters the substrate tank 9 through the water inlet pipe 11, and is delivered to the continuous stirring reactor 5 through the substrate delivery pump 13.

[0045] The pump speed ratio of the first delivery pump 13, the second delivery pump 3, and the third delivery pump 8 is 2:3:1. By setting the pump speed ratio, the inlet and outlet water balance of each reaction device in the reaction system is ensured, and there will be no liquid level imbalance.

[0046] The continuous stirring reactor 5 includes a first operation tank 51, a second agitator 52, a continuous stirring reactor thermostat 53, a first gas collection pipe 54, and a first valve 55. The second agitator 52 is arranged on the first operation tank 51. The periphery of the first operation tank 51 is provided with a continuous stirring reactor thermostat 53. The top of the first operation tank 51 is connected with a first gas collection pipe 54, and the first gas collection pipe 54 is provided with a first valve 55. The continuous stirring of the second agitator 52 makes the aquaculture wastewater and the sludge evenly mixed. The thermostat 53 of the continuous stirring reactor plays a role in constant temperature. The biogas generated by the continuous stirring reaction is collected through the first gas collection pipe 54. When collection is required, the first valve 55 is opened, and when collection is not required, the first valve 55 is closed.

[0047] The anaerobic membrane bioreactor 4 includes a second operation tank 41, a flat membrane assembly 42, a second gas collection pipe 43, a second valve 44, a third gas collection pipe 45, a third valve 46, an anaerobic membrane bioreactor thermostat 48, and a gas collection part 47. The anaerobic membrane bioreactor thermostat 48 is arranged on the periphery of the second operation tank 41, and the flat membrane assembly 42 is arranged in the second operation tank 41. The flat membrane assembly 42 of this embodiment is a polyvinyl chloride membrane assembly. The top of the second operation tank 41 is connected with the second gas collection pipe 43 and the third gas collection pipe 45, the second gas collection pipe 43 is provided with a second valve 44, the third gas collection pipe 45 is provided with a third valve 46, and the top of the third gas collection pipe 45 is connected with the gas collection part 47. The pore size of the membrane of the flat membrane assembly 42 is 0.22 μm, and the working volume ratio of the first operation tank 51 and the second operation tank 41 is 1:2. The flat membrane assembly 42 is built into the second operation tank 41. The flat membrane assembly 42 is used for filtering. When the second valve 44 is opened, the biogas generated by the treatment is collected by the second gas collection pipe 43. When the third valve 46 is opened, the purified biogas with high methane concentration enters the gas collection part 47 through the third gas collection pipe 45 for collection. The anaerobic membrane bioreactor thermostat 48 plays a constant temperature role. The continuous stirring reactor thermostat 53 and the anaerobic membrane bioreactor thermostat 48 of this embodiment are both constant temperature layers. In other embodiments, they can also be low-temperature circulating water baths and other equipment that can play a constant temperature role.

[0048] Among them, it also includes a wet gas flowmeter 14, a suction pipe 15, and a suction pump 16. The first gas collection pipe 54 and the second gas collection pipe 43 are both connected to the wet gas flowmeter 14. The water outlet of the flat membrane assembly 42 is connected to the suction pipe 15, and the suction pipe 15 is provided with a suction pump 16. The gas outlet end of the biogas circulation pipe 2 is vertically oriented to the flat membrane assembly 42, increasing the longitudinal shear force to achieve membrane flushing, alleviate membrane pollution, and fully mix the sludge and aquaculture wastewater. The flat membrane assembly 42 will intercept the generated blue iron ore, and the produced water will be discharged through the suction pipe 15 through the suction pump 16. The purified biogas with high concentration of methane is collected by the gas collection part 47. In this way, the energy recovery efficiency in aquaculture wastewater can be improved, the concentration of methane in biogas can be increased in situ, and the high-value recovery of phosphorus resources can be achieved simultaneously. The gas production is recorded by the wet gas flowmeter 14, and the gas passing through the wet gas flowmeter 14 is connected to a gas collection device such as an air bag for gas collection.

[0049] The added concentration of trivalent iron ions is crucial, and the following experiment was conducted by adding different concentrations of trivalent iron ions.

[0050] The invention was operated in the laboratory for more than 190 days, including 7 operation stages. The sewage treatment performance of each stage is as follows: Figure 2-5 shown. Figure 3-4 A, B, C, and D are the results of significance analysis, and no duplication indicates significant differences. In Phase I, II, and III, by shortening the HRT, the organic loading rate (OLR) increased from 0.54 to 0.90 gCOD / L. reactor / day. The results showed that the average CH4 yield of Phase I (HRT = 5d) was 0.18L / L / d, and that of Phase III (HRT = 3d) was 0.30L / L / d. The SMY of Phase I, II, and III were relatively stable at 0.20±0.05CH4 L / g COD( Figure 3 In addition, the contents of CH4 and CO2 in biogas were also stable at 61.4±2.0% and 38.5±2.0% ( Figure 4 ). Under the same OLR conditions, different concentrations of exogenous Fe(III) (ferric ions) were added in stages. When the amount of exogenous Fe(III) increased from 100 mg / L to 600 mg / L, the average SMY increased from 0.24±0.01 (Phase IV) to 0.29±0.02 L / gCOD (Phase VI) ( Figure 3) and remained stable. Similarly, the CH4 content gradually increased from 61.4% to 89.3% and remained stable. The main mechanism is: 1. Fe(III) is reduced to Fe(II) by dissimilatory iron-reducing bacteria in the AD system, and CO2 in the biogas is easily dissolved in water to form HCO3 under the action of circulating aeration. - . Fe(II) and HCO3 - Combined with FeCO3 precipitation, high-concentration methane can be recovered. 2. Fe(III) generates Fe3O4 in the system, which cooperates with AD to complete electron transfer between microorganisms and establish a DIET pathway.

[0051] The present invention has proved that Fe(III) assists the CSTR-AnMBR system to achieve in-situ purification of biogas in the reactor, so that the methane concentration reaches 89.3%, thereby achieving the recovery of high-concentration methane, which is significantly higher than other research reports.

[0052] like Figure 6-7 As shown in the figure, when the Fe(III) concentration was 300 mg / L, the TP removal rate in the aquaculture wastewater reached 96.8%, and the Fe utilization rate was 98.7%. When the Fe(III) concentration was further increased to 600 mg / L, the TP removal rate was 98.7%, but the Fe utilization rate dropped to 82.6%. Combined with the results of energy recovery, under this reaction condition, 300 mg Fe 3+ / L can meet the needs of microbial growth and metabolism inside the reactor, energy recovery and utilization, and the Fe element demand for FePs binding. Continuing to increase the input of Fe(III) will lead to a decrease in iron utilization and increase operating costs.

[0053] Fe(III) is bioreduced to Fe(II) in the AD system, and TP in the aquaculture wastewater is degraded to PO4 by microorganisms. 3- , and Fe(II) to form high-value cyanite. The intercepted Fe-P crystalline material was determined to be cyanite ( Figure 8 In order to further accurately identify the elemental composition of the crystalline mineral, the present invention uses EDS to scan the specific area marked by the SEM and analyze it ( Figure 9-10 ). Using precise surface element analysis, it was found that the elements in the spectrum are mainly composed of Fe, O, P, Al, Ca and other elements, but the area of ​​clustered crystalline material is mainly composed of Fe-PO overlapping, which is consistent with the elemental composition of blue iron ore and has obvious differences from the distribution area of ​​Ca and Al. 3- The two are combined to form blue iron ore and are retained in the AnMBR, achieving the enrichment of P in aquaculture wastewater W and the recovery of high-value products.

[0054] The present invention forms a Fe(III)-CSTR-AnMBR system by adding Fe(III) on the basis of treating aquaculture wastewater in a CSTR-AnMBR system. In the system, Fe(III) is coupled with CSTR-AnMBR, and Fe(III) can combine with CO2 in circulating biogas to generate FeCO3 precipitation, thereby increasing the methane concentration. Moreover, Fe(III), as a trace element necessary for microorganisms, can enhance their activity and improve the stability of the reactor, thereby realizing the long-term stable operation of Fe(III)-CSTR-AnMBR. In addition, Fe(III) can combine with part of the phosphorus in the aquaculture wastewater to generate high-value vivianite under the biological, physical and chemical effects of the AD system. Combined with the interception effect of the AnMBR membrane assembly, high-concentration vivianite is formed, which is subsequently recovered. Therefore, in the process system, the addition of Fe(III) can improve the energy recovery efficiency in aquaculture wastewater, increase the concentration of methane in biogas in situ, and simultaneously realize the high-value recovery of phosphorus resources.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for resource treatment of aquaculture wastewater, characterized in that: The following steps are involved: S1: The aquaculture wastewater is sent into a continuous stirring reactor to fully mix the aquaculture wastewater with the sludge inoculated in the continuous stirring reactor to form a sludge-water mixture. The organic matter in the aquaculture wastewater is hydrolyzed and acidified. At the same time, the organic phosphorus and precipitated inorganic phosphorus are converted into phosphate ions. S2: sending the mud-water mixture formed in step S1 into an anaerobic membrane bioreactor to further convert organic matter into biogas, while the membrane assembly of the anaerobic membrane bioreactor separates the mud-water mixture into solid and liquid to achieve sewage treatment; S3: During the operation of the reaction system, trivalent iron ions are continuously added to the mud-water mixture, and the trivalent iron ions are reduced to divalent iron ions under the synergistic action of anaerobic microorganisms in the reduction system; the generated biogas flows back to the anaerobic membrane bioreactor, and while enhancing mass transfer and reducing membrane pollution, the carbon dioxide in the biogas dissolves to form bicarbonate ions, and a part of the divalent iron ions and the bicarbonate ions form ferrous carbonate precipitates, thereby achieving in-situ purification of the biogas and collecting high-concentration methane; the phosphate ions in the mud-water mixture combine with another part of the divalent iron ions to form blue iron ions.

2. The method for resource-based treatment of aquaculture wastewater according to claim 1, characterized in that: The concentration of added ferric ions is 100-600 mg / L; The temperature of the sludge-water mixture in the anaerobic membrane bioreactor was maintained at 34-37°C by water bath heating.

3. The method for resource-based treatment of aquaculture wastewater according to claim 1, characterized in that: Before step S3, the method further includes: The mud-water mixture of the anaerobic membrane bioreactor is returned to the continuous stirring reactor to maintain the hydrolysis and acidification activities of the microorganisms in the continuous stirring reactor.

4. Aquaculture wastewater resource treatment system, used to implement the aquaculture wastewater resource treatment method according to any one of claims 1 to 3, characterized in that: It includes a continuous stirring reactor, an anaerobic membrane bioreactor, a mud-water mixture delivery pump, a biogas circulation pipe, and a circulation air pump; A mud-water mixture delivery pump for delivering the mud-water mixture from the continuous stirring reactor to the anaerobic membrane bioreactor is provided between the continuous stirring reactor and the anaerobic membrane bioreactor; The top of the anaerobic membrane bioreactor is connected with a biogas circulation pipe, the gas outlet end of the biogas circulation pipe is connected with the lower part of the anaerobic membrane bioreactor, and a circulation air pump is connected with the biogas circulation pipe.

5. The aquaculture wastewater resource treatment system according to claim 4 is characterized in that: It also includes a substrate delivery pipe, a circulating water bath, and a reflux delivery pump; A substrate delivery pipe is provided between the continuous stirring reactor and the anaerobic membrane bioreactor; The substrate delivery pipe is connected to a circulating water bath; A reflux delivery pump for returning the mud-water mixture of the anaerobic membrane bioreactor to the continuous stirring reactor is arranged between the continuous stirring reactor and the anaerobic membrane bioreactor.

6. The aquaculture wastewater resource treatment system according to claim 4 is characterized in that: It also includes a substrate tank, a first agitator, a water inlet pipe, and a substrate delivery pump; The first agitator is disposed in the substrate tank; The substrate tank is provided with a water inlet pipe; A substrate delivery pump for delivering aquaculture wastewater in the substrate tank into the continuous stirring reactor is arranged between the substrate tank and the continuous stirring reactor.

7. The aquaculture wastewater resource treatment system according to claim 6 is characterized in that: The pump speed ratio of the matrix delivery pump, the mud-water mixture delivery pump, and the reflux delivery pump is 1.5-2.5:2.7-3.7:

1.

8. The aquaculture wastewater resource treatment system according to claim 7 is characterized in that: The continuous stirring reactor comprises a first operation tank, a second stirrer, a continuous stirring reactor thermostat, a first gas collecting pipe, and a first valve; The second agitator is disposed in the first operating tank; The periphery of the first operation tank is provided with a continuous stirring reactor thermostat; The top of the first operating tank is connected to a first gas collecting pipe, and the first gas collecting pipe is provided with a first valve.

9. The aquaculture wastewater resource treatment system according to claim 8 is characterized in that: The anaerobic membrane bioreactor comprises a second operation tank, a flat membrane assembly, a second gas collection pipe, a second valve, a third gas collection pipe, a third valve, an anaerobic membrane bioreactor thermostat, and a gas collection part; An anaerobic membrane bioreactor constant temperature component is disposed on the periphery of the second operation tank; A flat membrane assembly is provided in the second operation tank; The top of the second operating tank is connected with a second gas collecting pipe and a third gas collecting pipe; The second gas collecting pipe is provided with a second valve, the third gas collecting pipe is provided with a third valve, and the top end of the third gas collecting pipe is connected with a gas collecting member.

10. The aquaculture wastewater resource treatment system according to claim 9, characterized in that: Also included is a wet gas flow meter, a suction pipe, and a suction pump; The first gas collecting pipe and the second gas collecting pipe are both connected to the wet gas flow meter; The water output outlet of the flat membrane module is connected with a suction pipe, and the suction pipe is provided with a suction pump; The gas outlet end of the biogas circulation pipe is vertically oriented toward the flat membrane module; The pore size of the membrane of the flat membrane assembly is 0.2-0.3 μm; The working volume ratio of the first operation tank and the second operation tank is 1:1.5-2.5.

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