Efficient treatment method for biogas slurry in pig farm

Abstract

The invention belongs to the technical field of breeding wastewater treatment, and relates to a pig farm biogas slurry efficient treatment method. The biological fiber material, the mineral material, the microbial carrier and the iron powder are subjected to modification treatment and then mixed with the biological activator and the complex microbial inoculant according to a specific proportion to be cured, and the high-performance biological matrix is prepared; and finally, constructing a treatment system consisting of a stone supporting layer, a biological matrix main reaction layer and a modified biological fiber material plant growth layer in the biological matrix pool, and planting specific wetland plants. Through multi-stage material modification and function cooperation, the removal efficiency of the system on pollutants in the biogas slurry is remarkably improved, and meanwhile the problems that a traditional system is prone to blockage, microbial activity is inhibited, and operation is unstable are effectively solved. The method is low in operation energy consumption and simple and convenient to maintain, can convert the waste substrate into the organic fertilizer base material, realizes organic combination of pollution treatment and resource recycling, and has the comprehensive advantages of high efficiency, stability and economy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of breeding wastewater treatment, and relates to a high-efficiency treatment method for biogas slurry of a pig farm. BACKGROUND

[0002] The biogas slurry of a pig farm is a byproduct of fermented pig wastewater, and contains high-concentration pollutants such as organic matter, ammonia nitrogen, phosphorus, suspended solids and pathogenic microorganisms. The treatment thereof has always been a difficulty in breeding wastewater treatment. At present, common treatment methods for the biogas slurry of a pig farm mainly include physical methods (such as sedimentation and filtration), chemical methods (such as flocculation and oxidation) and biological methods (such as aerobic treatment and constructed wetland). However, these methods have many defects in actual application. 1. Low denitrification and dephosphorization efficiency. Traditional biological treatment methods such as activated sludge method or conventional constructed wetland have limited removal effect on high-concentration ammonia nitrogen and total phosphorus in the biogas slurry. Due to the serious imbalance of carbon-nitrogen ratio (usually BOD / TN < 3) in the biogas slurry, the carbon source is insufficient for the denitrification process, resulting in low denitrification efficiency. At the same time, the removal of phosphorus mainly depends on chemical precipitation or adsorption, but the traditional adsorption materials are easy to saturate and difficult to regenerate, causing the treatment effect to decrease after long-term operation.

[0003] 2. System prone to blockage and frequent maintenance. High-concentration suspended solids and colloidal substances in the biogas slurry can easily cause rapid blockage of the treatment system (such as a biological filter or a constructed wetland), which requires frequent backwashing or replacement of the filler, increasing the operation and maintenance cost. Existing mineral adsorption materials such as zeolite and bentonite have a certain adsorption capacity, but lack surface modification and are easy to combine with the negatively charged colloids in the biogas slurry, forming a hardening and shortening the service life.

[0004] 3. Microbial activity is inhibited. The biogas slurry contains high-concentration ammonia nitrogen, salt and heavy metals, which have an inhibitory effect on functional microorganisms (such as nitrifying bacteria and denitrifying bacteria). In the traditional method, the microbial carrier (such as straw and rice husk) is not subjected to enzymatic hydrolysis treatment, and the carbon source is released slowly and insufficiently, which cannot continuously stimulate the activity of denitrifying bacteria, resulting in unstable denitrification process.

[0005] 4. Secondary pollution and resource waste. In the existing treatment process, sludge and waste filler are often disposed as solid waste, without realizing resource utilization. In addition, the use of chemical flocculants may introduce new pollutants such as aluminum or iron salt residues, affecting the safety of effluent.

[0006] 5. High energy consumption and complex operation. The aerobic treatment process requires continuous aeration, which has huge energy consumption. Although anaerobic treatment can produce biogas, the effluent still needs further treatment, and the overall process is long and complex to manage, which is not suitable for small and medium-sized pig farms.

[0007] 6. The system has poor stability, and the traditional artificial wetland is greatly affected by seasons and temperature, and the treatment efficiency significantly decreases in winter. Meanwhile, the filler layer is easily cemented, and the plant root system is oxygen-deficient, resulting in the attenuation of the system treatment capacity with the extension of the operation time. SUMMARY

[0008] In order to solve the above problems, the application provides a pig farm biogas slurry efficient treatment method, which specifically comprises the following steps: Step one, the biological fiber material is crushed to 40-50 mesh, then mixed with lye at a mass ratio of 1:(3-4), stirred at 70-80 DEG C and 120-150 rpm for 1-2 h, which can effectively dissolve and remove the impurities such as lignin and hemicellulose wrapped on the surface of the fiber in the biological fiber, expose the rich cellulose hydroxyl and large internal pores, filter after stirring, remove the filtrate, wash the filter residue with clean water until the washing liquid is neutral, then mix the filter residue with magnesium iron catalytic liquid at a mass ratio of 1:(3-4), soak at 60-70 DEG C for 5.5-6.5 h, which can load iron and magnesium ions on the surface of the fiber to become catalytic centers in the subsequent treatment. Filter after soaking, remove the filtrate, and irradiate the filter residue with 750-850 W microwave for 4-6 min to generate high temperature and high pressure inside the material instantaneously, further expand the pores. Then, instantaneously release the pressure after 1-2 MPa pressure maintaining for 1.5-2.5 min, which can greatly expand the pore structure of the material, increase the specific surface area by several times, and obtain rich oxygen-containing functional groups, thereby obtaining modified biological fiber material.

[0009] Preferably, the biological fiber material is one or more of plant straw, rice husk, sawdust and coconut shell. Most preferably, the biological fiber material is corn straw, reed straw, rice husk and coconut shell, and the mass ratio is (20-30):(15-25):(8-12):(10-20).

[0010] Preferably, the lye is a sodium hydroxide solution with a mass fraction of 4-6% or a potassium hydroxide solution with a mass fraction of 4-6%.

[0011] Preferably, the magnesium iron catalytic liquid comprises 0.4-0.6 mol / L ferric sulfate and 0.2-0.4 mol / L magnesium chloride based on water.

[0012] Step two, mix the mineral material with the ammonium-calcium solution at a mass ratio of 1:(8-10), soak for 2-3h at 75-85℃, achieve pre-loading of ammonium ions and calcium ions to open the pores, filter after soaking, remove the filtrate, and calcine the residue at 250-350℃ for 1-2h to fix the ammonium ions and partially dehydroxylate the layered structure to stabilize the expanded pores, so that they are not easily retracted in subsequent processing, and low-temperature calcination is far below the sintering temperature, which will not damage the crystal structure. After cooling to room temperature, mix with a polyepoxysuccinic acid (PESA) solution with a mass fraction of 4-6% at a mass ratio of 1:(10-12), and oscillate at 200-300rpm for 40-60min to obtain the modified mineral material. The carboxyl groups on the PESA molecular chain have strong negative electric properties and can be adsorbed on the surface of the material to form a layer of polymer with strong negative electricity. Through electrostatic repulsion, it can effectively prevent the material from combining too quickly with the negative suspended solids such as colloid and humus in the biogas slurry during subsequent processing, thereby delaying the blockage of the adsorption channel and prolonging the service life of the material. PESA itself is an excellent scale inhibitor, which can chelate calcium and magnesium ions in the biogas slurry to inhibit the crystallization and precipitation of slightly soluble salts such as calcium carbonate in the pores of the material, which complements the function of removing ammonium by ion exchange of the material itself.

[0013] Preferably, the mineral material includes one or more of weathered coal, attapulgite, diatomite, bentonite, zeolite, vermiculite, sepiolite and quartz sand. Most preferably, the mineral material includes attapulgite, diatomite, zeolite and vermiculite at a mass ratio of (2-4):(4-6):(3-5):(2-3).

[0014] Preferably, the ammonium-calcium solution includes 1-3mol / L of ammonium chloride and 1-3mol / L of calcium chloride based on water.

[0015] Step three, mix the microbial carrier with the complex enzyme solution at a mass ratio of 1:(4-6), soak for 4-5h at 45-55℃, filter, and remove the filtrate. The residue is the enzymatic microbial carrier. This process can partially degrade the microbial carrier and release part of the short-chain polysaccharides and oligosaccharides. These sugar substances can act as slow-release carbon sources in the substrate, continuously stimulating the activity of heterotrophic denitrifying bacteria, and solving the problem of imbalance between carbon and nitrogen in the biogas slurry.

[0016] Preferably, the microbial carrier includes one or more of sugarcane residue, corn cob, mushroom residue and vinasse. Most preferably, the microbial carrier includes sugarcane residue and corn cob at a mass ratio of (1-3):(1-3).

[0017] Preferably, the complex enzyme solution includes 4000-5000U / g of cellulase, 2000-3000U / g of pectinase and 2500-3500U / g of xylanase based on water.

[0018] Step four, mix the iron powder and silane coupling solution with a mass ratio of 1:(2-3), and ultrasonic at 40-50 kHz for 25-35 min, so that the silane coupling agent forms a dense hydrophobic protective film on the surface of the iron powder, which can isolate air and slow down oxidation. Filter out the filtrate, and mix the filter residue with the organic acid solution with a mass ratio of 1:(3-4), and stir at 40-50°C and 150-200 rpm for 1-1.5 h to obtain the modified iron powder. The organic acid can react with the residual oxides on the surface of the iron to form a stable layer of ferric citrate complex, and at the same time, the large number of carboxyl groups on the surface of the iron powder are exposed outward, so that the surface of the zero-valent iron changes from hydrophobic to hydrophilic and becomes negatively charged. This treatment greatly improves the dispersibility of the zero-valent iron in the hydrophilic biological matrix, prevents its agglomeration and sedimentation, and more importantly, the negative charge on the surface of the zero-valent iron enables it to be tightly adsorbed around the positively charged pollutants through electrostatic attraction, achieving targeted reduction while avoiding direct contact with functional microorganisms and eliminating the biological inhibition of the zero-valent iron.

[0019] Preferably, the silane coupling solution includes 1.5-2.5 g / L 3-aminopropyl triethoxysilane and 0.4-0.6 g / L γ-(2,3-epoxypropoxy) propyl trimethoxysilane based on anhydrous ethanol.

[0020] Preferably, the organic acid solution is a citric acid solution with a mass fraction of 4-6% or an acetic acid solution with a mass fraction of 5-7%.

[0021] Step five, mix the modified biological fiber material, modified mineral material, enzymatic microbial carrier, modified iron powder, biological activator, and composite bacterial agent with a mass ratio of (45-55):(20-30):(10-15):(8-12):(2-4):(0.4-0.6) in a double-shaft mixer to mix them evenly. During the mixing process, spray deionized water to make the water content reach 30-35%. After the mixing is completed, age and mature the mixture at room temperature for 22-26 h to allow the components to interact and balance the moisture, and obtain the biological matrix.

[0022] Preferably, the biological activator is one or more of sodium alginate powder, polyvinyl alcohol, guar gum, xanthan gum, polyglutamic acid, and carboxymethyl cellulose. Most preferably, the biological activator is sodium alginate powder.

[0023] Preferably, the composite bacterial agent includes nitrifying bacteria agent, denitrifying bacteria agent, photosynthetic bacteria agent, Bacillus subtilis agent, and Bacillus mucilaginosus agent with a mass ratio of (35-45):(25-35):(10-20):(8-12):(4-6).

[0024] Step six, place the biological matrix in a biological matrix pool with a volume of 0.15-0.2 m 3The 10-12 cm stone material is laid as a supporting layer, 80-100 cm biological matrix is laid as a main reaction layer, and 10-15 cm modified biological fiber material is laid as a plant growth layer from bottom to top in the head tank, and wetland plants with oxygen excretion function such as acorus calamus and water celery can be planted, and the planting density is 5-7 plants / m 2 .

[0025] Preferably, the stone material comprises one or more of marble, granite, dolomite, limestone, sandstone, shale, slate, pebble, vermiculite and zeolite.

[0026] Preferably, the plant growth layer plants one or more of acorus calamus, water celery, water lily, cattail, reed, water taro, water horn, water tiger tail, bamboo cane, water fir and water plant.

[0027] Step six, after the pig farm biogas slurry removes large suspended solids through a grid, the pH is adjusted to 6.5-7.5 by using dilute sulfuric acid, and the biogas slurry enters the first end of the biological matrix pool at a speed of 0.5-0.8 m 3 / h, so that it slowly flows to the end in the form of surface flow combined with internal filtration of the biological matrix. A reflux system is arranged at the end of the pool body to reflux 25-35% of the effluent to the first end and mix with fresh biogas slurry. The design of this “reflux ratio” can bring the generated nitrite and nitrate in the main reaction layer back to the front end to complete denitrification under the action of zero-valent iron and anaerobic microorganisms; on the other hand, the domesticated microorganisms rich in the reflux water can accelerate the degradation of new pollutants. The entire hydraulic retention time is 6-8 days, and the system is continuously operated. Every quarter of operation, the material in the upper 8-12 cm of the biological matrix can be checked, and if it is found to be hardened, it can be replaced with an equal amount of newly prepared biological matrix. The replaced old matrix can be used as a high-quality organic fertilizer base material to realize full recycling of resources.

[0028] Preferably, a plurality of biological matrix pools can be connected in series; a hydraulic impact type aerator is installed at the bottom of the matrix pool, the specification is Φ215 mm, the aerator is 250-270 mm away from the bottom of the pool, the air pipe design needs to adopt a ring network layout, the branch pipe flow rate is 5 m / s, and the dry pipe flow rate is 10-15 m / s. Aerating for 1 hour at 7:00 in the morning and 7:00 in the evening each day can meet the needs, and the aerator is stopped during the rest of the time.

[0029] The present application has the following advantages: (1) High-efficiency denitrification and phosphorus removal and pollutant removal, through the synergistic effect of modified biological fiber material and mineral material, the system forms a multi-stage adsorption-catalysis-biodegradation chain. The modified biological fiber material has a super large specific surface area and abundant functional groups, which can efficiently adsorb organic matter and ammonia nitrogen; the modified mineral material is treated by PESA, the surface is strongly negatively charged, the clogging is delayed by electrostatic repulsion, and the ammonium is stabilized by ion exchange; the complex bacterial agent (nitrifying bacteria, denitrifying bacteria, photosynthetic bacteria, etc.) forms a dominant flora in the biological matrix, which significantly improves the denitrification and phosphorus removal efficiency. Especially through the reflux system, the nitrate in the effluent is brought back to the front end, and the denitrification is completed under the action of modified iron powder and anaerobic microorganisms, completely solving the problem of carbon-nitrogen ratio imbalance, greatly improving the removal rate of ammonia nitrogen and total phosphorus, and making the effluent water quality stable and up to standard.

[0030] 2) Long-term anti-clogging and stable system operation, the present application fundamentally alleviates the clogging problem through material modification and structure design. The mineral material is calcined by ammonium-calcium solution and modified by PESA to form a stable expanded pore channel and a negative electric protective layer, effectively resisting the adsorption of colloids and humus; the biological matrix layer has a loose structure, which cooperates with the stone support layer to ensure smooth water flow. The system only needs to be checked and replaced with the upper consolidated material every quarter, with low maintenance frequency and high running stability compared with traditional artificial wetlands or biological filters.

[0031] 3) Continuous activation of microbial activity, enzyme-treated microbial carriers (such as sugarcane bagasse and corn cob) release short-chain polysaccharides and oligosaccharides as slow-release carbon sources, continuously stimulating the activity of denitrifying bacteria, solving the problem of insufficient carbon source in biogas slurry. At the same time, the modified iron powder is treated with organic acid, which is hydrophilic and negatively charged on the surface, which can target the reduction of pollutants and avoid the inhibition of functional microorganisms, ensuring the health and persistence of the microbial system.

[0032] 4) Resource recycling and no secondary pollution, the present application realizes the full recycling of waste. The replaced old biological matrix, which is rich in organic matter and nutrients, can be directly used as high-quality organic fertilizer base material for farmland or gardening, avoiding the generation of solid waste. The whole treatment process mainly uses biological and natural means, without adding chemical flocculants, and the effluent is non-toxic and harmless, in line with the concept of green agriculture.

[0033] 5) Low energy consumption and economical operation cost, the present application adopts the combination of surface flow and internal infiltration, with long hydraulic retention time and extremely low energy consumption. Only 1 hour of aeration is needed in the morning and evening, which is much lower than the continuous aeration requirement of traditional aerobic process. The biological matrix is prepared from widely available raw materials (such as straw, rice husk, weathered coal, etc.), which is low in cost and suitable for large-scale promotion.

[0034] 6) Strong adaptability and long-term high efficiency: This invention considers the variable factors in actual operation. By connecting multiple biological substrate tanks in series and controlling the reflux ratio, it adapts to different concentrations and volumes of biogas slurry; the oxygen secretion of wetland plants (such as calamus and water celery) enhances the aerobic-anaerobic alternation environment of the substrate layer, improving the treatment stability throughout the four seasons. Long-term operation shows that the system can operate sustainably and efficiently for many years without large-scale modifications, with no significant decline in treatment effect. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 This is a diagram showing the series connection of the biological substrate pool in Example 1. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1 Raw material preparation: Bio-fiber materials: corn stalks, reed stalks, rice husks and coconut shells, in a mass ratio of 25:25:10:15.

[0039] Magnesium-iron catalyst solution: based on water, it includes 0.5 mol / L ferric sulfate and 0.3 mol / L magnesium chloride.

[0040] Mineral materials: attapulgite, diatomite, zeolite and vermiculite, in a mass ratio of 3:5:4:1.5.

[0041] Ammonium-calcium solution: Based on water, it consists of 2 mol / L ammonium chloride and 2 mol / L calcium chloride.

[0042] Microbial carriers: sugarcane bagasse and corn cobs in a 1:1 mass ratio.

[0043] Complex enzyme solution: Based on water, it contains 4500 U / g cellulase, 2500 U / g pectinase and 3000 U / g xylanase.

[0044] Silane coupling solution: Based on anhydrous ethanol, it includes 2 g / L of 3-aminopropyltriethoxysilane and 0.5 g / L of γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0045] Compound microbial agents: nitrifying bacteria (purchased from Guangzhou Qingwo Biotechnology Co., Ltd.), denitrifying bacteria (purchased from Hubei Zhongyan Biotechnology Co., Ltd.), photosynthetic bacteria (purchased from Jinan Shengshi Biotechnology Co., Ltd.), Bacillus subtilis (purchased from Shandong Borui Chemical Co., Ltd.), and Bacillus mucilaginosus (purchased from Hubei Xingdongcheng Chemical Co., Ltd.), with a mass ratio of 40:30:15:10:5.

[0046] Stone materials: marble, granite and pebbles, in a mass ratio of 2:1:5.

[0047] Wetland plants: sweet flag, cattail, and reed, with a plant ratio of 1:3:2.

[0048] Step 1: Crush the bio-cellulose material to 45 mesh, then mix it with a 5% sodium hydroxide solution at a mass ratio of 1:3, stir at 75℃ and 135 rpm for 1.5 h, filter, remove the filtrate, wash the filter residue with water until the washing liquid is neutral, then mix the filter residue with magnesium iron catalytic solution at a mass ratio of 1:4, soak at 65℃ for 6 h, filter, remove the filtrate, irradiate the filter residue with 800W microwave for 5 min, hold at 1.5 MPa for 2 min and then release the pressure instantly to obtain the modified bio-cellulose material.

[0049] Step 2: Mix the mineral material with calcium ammonium solution at a mass ratio of 1:9, soak at 80℃ for 2.5h, filter, remove the filtrate, calcine the filter residue at 300℃ for 1.5h, mix with 5% PESA solution at a mass ratio of 1:11, and shake at 250rpm for 50min to obtain the modified mineral material.

[0050] Step 3: Mix the microbial carrier and the compound enzyme solution at a mass ratio of 1:5, soak at 50℃ for 4.5 hours, filter, remove the filtrate, and the filter residue is the enzymatically hydrolyzed microbial carrier.

[0051] Step 4: Mix iron powder and silane coupling solution at a mass ratio of 1:2.5, sonicate at 45 kHz for 30 min, filter, remove filtrate, mix the filter residue with 5% citric acid solution at a mass ratio of 1:3, stir at 45 ℃ and 175 rpm for 1.25 h to obtain modified iron powder.

[0052] Step 5: The modified bio-fiber material, modified mineral material, enzymatically hydrolyzed microbial carrier, modified iron powder, sodium alginate powder and compound bacterial agent are thoroughly mixed in a twin-shaft mixer at a mass ratio of 50:25:13:10:3:0.5. During the mixing process, deionized water is sprayed to make the water content reach 32%. After mixing, the mixture is aged at room temperature for 24 hours to obtain the bio-matrix.

[0053] Step six, in a volume of 0.18m³ 3 In the bio-matrix pool for each head of pig (175cm deep), from bottom to top, an 11cm layer of stones is laid as a support layer, a 90cm layer of bio-matrix as the main reaction layer, and a 13cm layer of modified bio-fiber material as a plant growth layer. Wetland plants are then planted at a density of 6 plants / m². 2 .

[0054] Step seven, as Figure 1 As shown, three biological substrate tanks (primary, secondary, and tertiary tanks) are connected in series by PVC pipes. The walls and bottom of the biological substrate tanks are waterproof. The walls are made of brick-concrete structure with a thickness of 27cm, and the bottom is made of concrete structure with a thickness of 20cm. Hydraulic impact aerators with a diameter of Φ215mm are installed at the bottom of the substrate tanks, 260mm from the bottom. The air duct design adopts a ring network layout, with a branch pipe flow velocity of 5m / s and a main pipe flow velocity of 12m / s.

[0055] After large suspended solids are removed from the biogas slurry from the pig farm through a screen, the pH is adjusted to 7.0±0.5 with dilute sulfuric acid, and then... 3 The water enters the primary tank from the upper inlet at a rate of [amount missing] / h, then flows into the secondary tank through the lower pipe, and then into the tertiary tank through the upper pipe at the end of the secondary tank. Finally, it flows out from the bottom outlet at the end of the tertiary tank (30% of the effluent is returned to the primary tank inlet). Aeration is carried out for 1 hour each at 7:00 AM and 7:00 PM daily, and aeration is stopped at other times. The total hydraulic retention time is 7 days. The system operates continuously. Every quarter, the top 10cm of the biological substrate can be inspected. If compaction is found, it should be removed and replaced with an equal amount of newly prepared biological substrate. The replaced old substrate, due to its rich nutrients, can be used as a high-quality organic fertilizer substrate, achieving a complete resource cycle.

[0056] Experimental Example 1 The method described in Example 1 was used to treat the biogas slurry from a local pig farm. Sampling began after the system had been running stably for 30 days. Influent and effluent samples were collected weekly for four consecutive weeks, and the average value was taken as the final result. The results are shown in Table 1. Water quality analysis methods: COD was determined according to the "Determination of Chemical Oxygen Demand in Water - Dichromate Method" (HJ 828-2017); ammonia nitrogen was determined according to the "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometric Method" (HJ 535-2009); total phosphorus was determined according to the "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method" (GB / T 11893-1989); suspended solids (SS) were determined according to the "Determination of Suspended Solids in Water - Gravimetric Method" (GB 11901-89). Removal rate = (Influent concentration - Effluent concentration) / Influent concentration × 100%.

[0057] Table 1 Removal effect

[0058] As shown in Table 1, the efficient treatment method for pig farm biogas slurry of this invention achieves extremely high removal rates (all exceeding 93%) for COD, ammonia nitrogen, total phosphorus, and SS, with consistently compliant effluent quality. The system operates stably, requiring minimal maintenance except for quarterly checks, demonstrating its advantages in long-term anti-clogging and resource recycling. The synergistic effect of modified materials (such as modified bio-fiber materials and modified mineral materials), along with the application of compound microbial agents and enzymatic microbial carriers, effectively solves the problems of carbon-nitrogen ratio imbalance and microbial inhibition, ensuring treatment efficiency. Experimental data verify that this invention achieves efficient treatment with low energy consumption (only 2 hours of aeration per day), making it suitable for large-scale application of pig farm biogas slurry.

[0059] Furthermore, existing wastewater treatment projects require the construction of anaerobic ponds, aeration tanks, and the installation of corresponding mechanical equipment such as blowers and aerators. The construction and equipment investment for a wastewater treatment project for a pig farm with 1000 pigs typically ranges from 1.5 million to 2 million yuan, which is unaffordable for most small businesses. The pig farm biogas slurry treatment method of this invention has a one-time total investment cost plus annual operating expenses of only about 210,160 yuan. Even with subsequent ecological treatment projects, the annual operating cost is 66,000 yuan, and the total expenditure is only 276,160 yuan, less than one-fifth of the cost of conventional industrial wastewater treatment projects. Therefore, the pig farm biogas slurry treatment method of this invention is generally acceptable to pig farmers.

[0060] Existing conventional wastewater treatment technologies all require electricity for aeration equipment. Taking the UASB-SBBR (coagulation-flotation) combined process for treating wastewater from a pig farm with 1,000 pigs as an example, the typical electricity cost is about 30 yuan / day, and the average daily cost of chemicals is about 100 yuan. Including labor and maintenance costs, the total annual operating cost is about 84,000 yuan. In contrast, the aeration equipment in this treatment method aerates for 2 hours per day with a power of 5.5kW, and the electricity cost is 100 yuan / month. The total operating cost of this system mainly includes the addition of substrate materials 2-3 times a year and the cost of back-end labor maintenance, totaling about 92,000 yuan. If we deduct the annual wetland plant revenue of 20,000-30,000 yuan, the net annual operating cost of the system of this invention is only about 60,000-70,000 yuan.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for efficient treatment of biogas slurry from pig farms, characterized in that, Includes the following steps: Step 1: After the bio-fiber material is crushed, it is mixed with alkaline solution at a mass ratio of 1:(3-4), filtered, the filtrate is removed, the filter residue is washed with clean water, and then mixed with magnesium iron catalytic solution at a mass ratio of 1:(3-4) and soaked, filtered, the filtrate is removed, and the filter residue is successively subjected to microwave irradiation and high pressure treatment to obtain modified bio-fiber material. Step 2: Mix the mineral material with calcium ammonium solution at a mass ratio of 1:(8-10), soak, filter, remove the filtrate, calcine the filter residue at 250-350℃ for 1-2 hours, mix with PESA solution at a mass ratio of 1:(10-12) and shake to obtain the modified mineral material; Step 3: After soaking the microbial carrier and the compound enzyme solution at a mass ratio of 1:(4-6), the enzymatically hydrolyzed microbial carrier is obtained. Step 4: Mix iron powder and silane coupling solution at a mass ratio of 1:(2-3) and sonicate. Filter the mixture and remove the filtrate. Mix the filter residue with organic acid solution at a mass ratio of 1:(3-4) and stir to obtain modified iron powder. Step 5: Mix the modified bio-fiber material, modified mineral material, enzymatically hydrolyzed microbial carrier, modified iron powder, bio-activator and compound bacterial agent in a mass ratio of (45-55):(20-30):(10-15):(8-12):(2-4):(0.4-0.6). During the mixing process, spray deionized water to make the water content reach 30-35%. Then, mature at room temperature for 22-26 hours to obtain the bio-matrix. Step 6: In the bio-substrate pool, lay 10-12cm of stones, 80-100cm of bio-substrate, and 10-15cm of modified bio-fiber material from bottom to top. Plant wetland plants on the modified bio-fiber material at a density of 5-7 plants / m². 2 ; Step 7: After the biogas slurry from the pig farm is passed through a screen to remove large suspended solids, the pH is adjusted to 6.5-7.5 with dilute sulfuric acid at a concentration of 0.5-0.8 mg / L. 3 The biomass enters the head end of the biomass tank at a rate of / h. 25-35% of the effluent is returned to the head end and mixed with fresh biogas slurry. The hydraulic retention time is 6-8 days. The system runs continuously. Every quarter, check the material in the top 8-12cm of the biomass. If compaction is found, remove it and replace it with an equal amount of biomass. The replaced old substrate can be used as a high-quality organic fertilizer substrate.

2. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The bio-fiber material mentioned in step one is one or more of plant straw, rice husk, wood chips, and coconut shell.

3. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The alkaline solution mentioned in step one is a sodium hydroxide solution or a potassium hydroxide solution with a mass fraction of 4-6%; the magnesium-iron catalyst solution, based on water, includes 0.4-0.6 mol / L ferric sulfate and 0.2-0.4 mol / L magnesium chloride.

4. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The mineral materials mentioned in step two include one or more of the following: weathered coal, attapulgite, diatomite, bentonite, zeolite, vermiculite, sepiolite, and quartz sand.

5. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The ammonium-calcium solution mentioned in step two, based on water, comprises 1-3 mol / L of ammonium chloride and 1-3 mol / L of calcium chloride.

6. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The microbial carrier mentioned in step three includes one or more of sugarcane bagasse, corn cob, mushroom residue, and distiller's grains. The compound enzyme solution, based on water, includes 4000-5000 U / g of cellulase, 2000-3000 U / g of pectinase, and 2500-3500 U / g of xylanase.

7. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The silane coupling solution in step four, based on anhydrous ethanol, comprises 1.5-2.5 g / L of 3-aminopropyltriethoxysilane and 0.4-0.6 g / L of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the organic acid solution is a citric acid solution with a mass fraction of 4-6% or an acetic acid solution with a mass fraction of 5-7%.

8. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The bioactivator mentioned in step five is one or more of sodium alginate powder, polyvinyl alcohol, guar gum, xanthan gum, polyglutamic acid, and carboxymethyl cellulose.

9. The method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The compound microbial agent mentioned in step five includes nitrifying bacteria, denitrifying bacteria, photosynthetic bacteria, Bacillus subtilis, and Bacillus mucilaginosus, with a mass ratio of (35-45):(25-35):(10-20):(8-12):(4-6).

10. A method for efficient treatment of biogas slurry in pig farms according to claim 1, characterized in that, The stone material mentioned in step six includes one or more of marble, granite, dolomite, limestone, sandstone, shale, slate, pebbles, vermiculite, and zeolite, and the wetland plants include one or more of calamus, water celery, water lily, cattail, reed, taro, water star anise, water sedge, reed, dawn redwood, water pine, and water lettuce.

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