Treatment process for domestic sewage of villages and towns

Abstract

The invention provides a treatment process of rural domestic sewage, and belongs to the technical field of sewage treatment, and the treatment process comprises the following steps: S1, concentrated rural domestic sewage is separated by a grid and then introduced into a sedimentation tank, a coagulant is added into the sedimentation tank, a flocculating agent is added after stirring, and treated effluent is marked as pretreated sewage; s2, the pretreated sewage is introduced into an anaerobic tank, the sewage in the anaerobic tank enters an aerobic tank through overflow, nitrifying bacteria and modified charcoal loaded EM bacteria are added into the aerobic tank, the sewage finally enters a purification tank through a water pipe, and effluent of the purification tank is discharged water; the modified biochar is prepared from the following raw materials: sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde; according to the present invention, the modified charcoal loaded EM bacteria and the nitrifying bacteria are jointly used in the aerobic tank so as to form the close symbiotic relationship between the EM bacteria and the nitrifying bacteria, such that the phosphorus content, the ammonia nitrogen content and the organic matter content in the sewage are synergistically reduced, and the problem that the existing rural domestic sewage treatment effect is poor is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a treatment process for rural domestic sewage. Background Art

[0002] At present, the main treatment method for rural sewage is biochemical treatment, including anaerobic treatment and aerobic treatment. Generally, nitrifying bacteria are added alone in the aerobic tank. However, the nitrifying bacteria have a single strain and focus on nitrogen removal treatment, and the treatment effect on organic matter is poor. EM bacterial agents contain a variety of aerobic microorganisms and facultative anaerobic microorganisms, such as photosynthetic bacteria, lactic acid bacteria, yeast, actinomycetes, fungi, etc. The bacterial community composition is complex and the structure is stable, and they can give full play to the symbiotic, mutualistic and competitive relationships among each other. Through biodegradation metabolism, the pollutants in rural black water can be removed. However, EM bacteria are water-soluble liquids, and lack a carrier when treating sewage alone, resulting in low removal rates of nitrogen and phosphorus, poor effluent purification effect, and easy loss of bacterial cells. Summary of the Invention

[0003] The purpose of the present invention is to provide a treatment process for rural domestic sewage to solve the problem of poor treatment effect of existing rural domestic sewage.

[0004] The purpose of the present invention can be achieved by the following technical solutions: A treatment process for rural domestic sewage includes the following steps: S1. Concentrate rural domestic sewage, separate it through a grille, and then introduce it into a sedimentation tank. Add a coagulant to the sedimentation tank, stir, and then add a flocculant. The treated effluent is recorded as pretreated sewage; S2. Introduce the pretreated sewage into an anaerobic tank. The sewage in the anaerobic tank overflows into an aerobic tank. Nitrifying bacteria and modified biochar-loaded EM bacteria are added to the aerobic tank, and finally it enters a purification tank through a water pipe. The effluent from the purification tank is the discharged water.

[0005] Further, the modified biochar-loaded EM bacteria are prepared through the following steps: Dilute the EM bacterial solution with distilled water to 2-5 times, then add modified biochar, oscillate for 120-150 min, filter, and dry to obtain modified biochar-loaded EM bacteria.

[0006] Further, the oscillation treatment temperature is 25°C and the rotation speed is 160 r / min.

[0007] Further, the dosage ratio of the EM bacterial solution to the modified biochar is 10 mL: 1.5-2.5 g.

[0008] Using modified biochar as the carrier for EM bacteria, it has a rich pore structure, polar groups and hydrophobic long chains. The pore structure can provide more attachment sites for the EM bacteria solution, which is conducive to the full contact and combination of the bactericide and the carrier. The hydrophilic groups are combined with the bactericide through hydrogen bonding and other interactions to enhance the loading stability. The hydrophobic long chains enhance the adsorption performance of the modified biochar for pollutants through hydrophobic interactions, improving the degradation effect of EM bacteria on pollutants.

[0009] Furthermore, the EM bacteria solution is obtained by activating and fermenting EM bacteria strain dry powder. Specifically, the EM bacteria strain dry powder is inoculated on the EM culture medium, and then placed in a sealed plastic bottle, at 36±1°C, 200 r / min, with gas released once a day, and shaken and cultured for 48 h to obtain the activated EM bacteria solution. The activated EM bacteria solution and the EM culture medium are mixed at a volume ratio of 1:18 - 20, at a constant temperature of 36°C, shaken at 160 r / min, with gas released once a day, and shaken and cultured for 72 h to obtain the EM bacteria solution.

[0010] Furthermore, the composition of the EM bacteria culture medium is: 100 g of brown sugar, 1 g of urea, 1 g of NaCl, 1 L of distilled water, and the pH is adjusted to 7.0±0.2 after dissolution.

[0011] Furthermore, the raw materials for preparing the modified biochar include sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde.

[0012] Furthermore, the modified biochar is prepared through the following steps: Add sodium alginate and phosphatidylserine to deionized water, stir evenly, then add magnetic biochar, heat up to 50°C, stir for 10 min, then add glutaraldehyde, continue to stir for 1.5 - 2.5 h, filter, wash the filter cake with deionized water and then dry to obtain the modified biochar.

[0013] Furthermore, the dosage ratio of sodium alginate, phosphatidylserine, deionized water, magnetic biochar and glutaraldehyde is 0.15 - 0.3 g: 0.1 - 0.2 g: 50 - 100 mL: 1 g: 4 mL. Using sodium alginate and phosphatidylserine as modifiers and glutaraldehyde as a crosslinking agent, sodium alginate and phosphatidylserine are introduced onto the surface of the magnetic biochar to obtain the modified biochar.

[0014] Furthermore, the magnetic biochar is prepared through the following steps: Cobalt sulfate, nickel sulfate and iron sulfate are added to deionized water. After stirring in a water bath at 40 - 60 °C for 1 h, the temperature is lowered to 30 °C. Sodium hydroxide solution is added dropwise. After the addition is complete, the temperature is raised to 90 °C and stirred for 1 h, then transferred to an autoclave and treated at 200 °C for 12 h. The obtained product is washed with distilled water until the washing liquid is neutral, dried and ground to obtain cobalt nickel ferrite. Wood chips are added to the cobalt nickel ferrite and treated in a high-pressure reactor at 200 °C for 12 h. The obtained product is washed and dried to obtain magnetic biochar.

[0015] Further, the dosage ratio of cobalt sulfate, nickel sulfate, iron sulfate, deionized water, sodium hydroxide solution and wood chips is 8.43 g : 0.88 g : 17.78 g : 50 - 100 mL : 50 mL : 8 - 10 g. The concentration of the sodium hydroxide solution is 3 mol / L. Using wood chips as the carbon source and cobalt sulfate, nickel sulfate and iron sulfate as magnetic raw materials, cobalt nickel ferrite - biochar is prepared by the hydrothermal method, which has excellent magnetism.

[0016] Further, the dosage of the coagulant is 20 - 30 g per ton of rural domestic sewage; the dosage of the flocculant is 10 - 20 g per ton of rural domestic sewage.

[0017] Further, the coagulant is basic aluminum chloride and / or aluminum sulfate.

[0018] Further, the flocculant is polyacrylamide.

[0019] Further, the addition amount of nitrifying bacteria in the aerobic tank is 1 - 3% of the sewage quality in the aerobic tank, and the addition amount of modified biochar loaded with EM bacteria is 1 - 2% of the sewage quality in the aerobic tank.

[0020] Further, denitrifying bacteria are added to the anaerobic tank, and the addition amount of denitrifying bacteria is 2 - 5% of the sewage quality in the anaerobic tank.

[0021] Further, the hydraulic retention time of the anaerobic tank is 5 - 7 h, the hydraulic retention time of the aerobic tank is 6 - 8 h, an aeration device is arranged in the aerobic tank, and the aeration time is 2 - 3 h per 24 h of aeration.

[0022] Further, the purification tank has a two - layer structure. The upper layer is the adsorption layer, and the lower layer is the packing layer. The thickness of the adsorption layer is 40 - 60 cm, and the thickness of the packing layer is 15 - 25 cm; the adsorption layer contains activated carbon, expanded perlite and straw, and the packing layer contains clay red bricks and iron tailings.

[0023] Further, the mass ratio of the activated carbon, expanded perlite and straw is 5 - 10 : 5 - 10 : 30 - 40; the mass ratio of the clay red bricks and iron tailings is 3 - 5 : 1 - 3.

[0024] Further, the particle sizes of the activated carbon, expanded perlite, and straw are independently 0.05 - 0.15 cm; the particle sizes of the clay red brick and iron tailings are independently 0.8 - 2 cm.

[0025] Advantages of the present invention: 1. The present invention provides a rural sewage treatment process, which sequentially undergoes flocculation treatment, anaerobic treatment, aerobic treatment, and purification treatment to gradually reduce the content of pollutants in the effluent. In particular, the combined use of modified biochar loaded with EM bacteria and nitrifying bacteria in the aerobic tank enables a close symbiotic relationship to form between the EM bacteria and nitrifying bacteria, synergistically reducing the contents of phosphorus, ammonia nitrogen, and organic matter in the sewage, significantly improving the removal rates of phosphorus, ammonia nitrogen, and organic matter in the sewage, and solving the problem of poor treatment effect of existing rural domestic sewage.

[0026] 2. The present invention uses modified biochar as the carrier of the EM bacteria agent. Through the loading treatment, a relatively stable microecological environment is provided for the EM bacteria, which is beneficial to their growth, reproduction, and metabolic activities, reduces the loss or damage of the EM bacteria agent caused by factors such as water flow impact during the sewage treatment process, improves its stability, and is conducive to increasing the contact area between the EM bacteria agent and pollutants in the sewage. Furthermore, the EM bacteria can fully exert their degradation and transformation functions to remove pollutants in the environment.

[0027] 3. The modified biochar in the present invention is magnetic biochar carrying sodium alginate and phosphatidylserine on its surface. The good magnetic properties endow it with the characteristic of easy separation, and the weak magnetic field generated by it can promote the aggregation of paramagnetic oxygen near the modified biochar loaded with EM bacteria, increasing the contact degree between the EM bacteria and oxygen, which helps to accelerate the reproduction and metabolism of the EM bacteria. Moreover, the magnetic effect has a good stimulating effect on the EM bacteria, which can catalyze the enzyme activity of the EM bacteria, thereby enhancing the purification effect of the EM bacteria on the sewage. In addition, on the one hand, the phosphatidylserine carried by the modified biochar can provide certain nutrients (N and P nutrients) for the EM bacteria, which is beneficial to improving the biological activity of the EM bacteria. On the other hand, it binds to organic pollutants in the sewage through hydrogen bond action or hydrophobic interaction, which is conducive to promoting the rapid degradation of pollutants by the EM bacteria. Specific embodiments

[0028] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present application clearer, the following further details the present application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can each be single or multiple.

[0030] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] It should be understood that in various embodiments of this application, the magnitude of the serial numbers of each process does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic and should not constitute any limitation to the implementation process of the embodiments of this application.

[0032] The weights of the relevant components mentioned in the specification of the embodiments of this application can not only refer to the specific contents of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the specification of the embodiments of this application are scaled up or down in proportion, they are within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass described in the specification of the embodiments of this application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0033] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0034] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in this application can be obtained through the market or can be prepared by existing methods.

[0035] To solve the problem of poor domestic sewage treatment effect to a certain extent, this application provides a treatment process for rural domestic sewage, including the following steps: S1. Concentrate the rural domestic sewage, separate it through a grille, and then introduce it into a sedimentation tank. Add a coagulant to the sedimentation tank, stir it, and then add a flocculant. The treated effluent is recorded as pretreated sewage; S2. Feed the pretreated sewage into the anaerobic tank. The sewage in the anaerobic tank overflows into the aerobic tank, where nitrifying bacteria and EM bacteria loaded on modified biochar are added. Finally, it enters the purification tank through a water pipe, and the effluent from the purification tank is the discharged water.

[0036] In some embodiments, the EM bacteria loaded on modified biochar are prepared through the following steps: Dilute the EM bacteria liquid with distilled water to 2 - 5 times, then add modified biochar, conduct oscillation treatment for 120 - 150 min, filter, and dry to obtain EM bacteria loaded on modified biochar.

[0037] In some specific embodiments, the temperature of the oscillation treatment is 25°C and the rotation speed is 160 r / min.

[0038] In some specific embodiments, the dosage ratio of the EM bacteria liquid to the modified biochar is 10 mL : 1.5 - 2.5 g.

[0039] In some embodiments, the EM bacteria liquid is obtained by activating and fermenting EM bacteria strain dry powder. Specifically, inoculate the EM bacteria strain dry powder on the EM culture medium, then place it in a sealed plastic bottle, at 36 ± 1°C and 200 r / min, release gas once a day, conduct oscillation culture for 48 h to obtain the activated EM bacteria liquid. Mix the activated EM bacteria liquid and the EM culture medium at a volume ratio of 1 : 18 - 20, at a constant temperature of 36°C and 160 r / min, release gas once a day, and conduct oscillation culture for 72 h to obtain the EM bacteria liquid.

[0040] In some specific embodiments, the composition of the EM bacteria culture medium is: 100 g of brown sugar, 1 g of urea, 1 g of NaCl, 1 L of distilled water. After dissolution, adjust the pH to 7.0 ± 0.2.

[0041] In some embodiments, the raw materials for preparing the modified biochar include sodium alginate, magnetic biochar, phosphatidylserine, and glutaraldehyde.

[0042] In some specific embodiments, the modified biochar is prepared through the following steps: Add sodium alginate and phosphatidylserine to deionized water, stir evenly, then add magnetic biochar, heat up to 50°C, stir for 10 min, add glutaraldehyde, continue to stir for 1.5 - 2.5 h, filter, wash the filter cake with deionized water and then dry to obtain the modified biochar.

[0043] In some embodiments, the dosage ratio of sodium alginate, phosphatidylserine, deionized water, magnetic biochar, and glutaraldehyde is 0.15 - 0.3 g : 0.1 - 0.2 g : 50 - 100 mL : 1 g : 4 mL.

[0044] In some specific embodiments, the magnetic biochar is prepared through the following steps: Cobalt sulfate, nickel sulfate and iron sulfate are added to deionized water. After stirring in a water bath at 40 - 60 °C for 1 h, the temperature is lowered to 30 °C. Sodium hydroxide solution is added dropwise. After the addition is complete, the temperature is raised to 90 °C and stirred for 1 h, then transferred to an autoclave and treated at 200 °C for 12 h. The obtained product is washed with distilled water until the washing liquid is neutral, dried and ground to obtain cobalt nickel ferrite. Wood chips are added to the cobalt nickel ferrite, and it is treated in a high-pressure reactor at 200 °C for 12 h. The obtained product is washed and dried to obtain magnetic biochar.

[0045] In some specific embodiments, the dosage ratio of cobalt sulfate, nickel sulfate, iron sulfate, deionized water, sodium hydroxide solution and wood chips is 8.43 g : 0.876 g : 17.778 g : 50 - 100 mL : 50 mL : 8 - 10 g, and the concentration of the sodium hydroxide solution is 3 mol / L.

[0046] In some embodiments, the dosage of the coagulant is 20 - 30 g per ton of rural domestic sewage; the dosage of the flocculant is 10 - 20 g per ton of rural domestic sewage.

[0047] In some embodiments, the coagulant is basic aluminum chloride and / or aluminum sulfate.

[0048] In some embodiments, the flocculant is polyacrylamide.

[0049] In some embodiments, the addition amount of nitrifying bacteria in the aerobic tank is 1 - 3% of the mass of the sewage in the aerobic tank, and the addition amount of the modified biochar loaded with EM bacteria is 1 - 2% of the mass of the sewage in the aerobic tank.

[0050] In some embodiments, denitrifying bacteria are added to the anaerobic tank, and the addition amount of the denitrifying bacteria is 2 - 5% of the mass of the sewage in the aerobic tank.

[0051] In some embodiments, the hydraulic retention time of the anaerobic tank is 5 - 7 h, the hydraulic retention time of the aerobic tank is 6 - 8 h, and an aeration device is arranged in the aerobic tank, and the aeration time is 2 - 3 h per 24 h.

[0052] In some embodiments, the purification tank has a two-layer structure. The upper layer is an adsorption layer, and the lower layer is a packing layer. The thickness of the adsorption layer is 40 - 60 cm, and the thickness of the packing layer is 15 - 25 cm; the adsorption layer contains activated carbon, expanded perlite and straw, and the packing layer contains clay red bricks and iron tailings.

[0053] In some embodiments, the mass ratio of the activated carbon, expanded perlite and straw is 5 - 10 : 5 - 10 : 30 - 40; the mass ratio of the clay red bricks and iron tailings is 3 - 5 : 1 - 3.

[0054] In some embodiments, the particle sizes of activated carbon, expanded perlite, and straw are independently 0.05 - 0.15 cm; the particle sizes of clay red bricks and iron tailings are independently 0.8 - 2 cm.

[0055] The technical solutions of the present application will be described below through specific examples and comparative examples.

[0056] The EM bacterial strain dry powder in the present application is purchased from Henan Zhongguang Group. The bacterial strain is a yellowish-brown dry powder composite bacterium agent, which is composed of bifidobacteria, lactic acid bacteria, bacillus, photosynthetic bacteria, yeast, actinomycetes, acetic acid bacteria, etc. Sodium alginate: purchased from Qingdao Mingyue Seaweed Group Co., Ltd., viscosity (25 °C) 500 - 550 mPa·s, 250 - 400 mPa·s.

[0057] Preparation Example 1

[0058] The preparation of modified biochar is as follows: Add 0.15 g of sodium alginate and 0.1 g of phosphatidylserine to 50 mL of deionized water. After stirring evenly, add 1 g of magnetic biochar, heat up to 50 °C, stir for 10 min, then add 4 mL of glutaraldehyde, continue to stir for 1.5 h, filter, wash the filter cake with deionized water and then dry to obtain modified biochar.

[0059] Magnetic biochar is prepared through the following steps: Add 8.43 g of cobalt sulfate, 0.88 g of nickel sulfate, and 17.78 g of iron sulfate to 50 mL of deionized water. Stir in a water bath at 40 °C for 1 h, then cool down to 30 °C, dropwise add sodium hydroxide solution with a concentration of 3 mol / L. After dropping, heat up to 90 °C and stir for 1 h, transfer to an autoclave, and treat at 200 °C for 12 h. Wash the obtained product with distilled water until the washing liquid is neutral, dry, grind, and pass through a 200-mesh sieve to obtain cobalt-nickel ferrite. Add 10 g of wood chips with a particle size of 0.15 - 0.25 mm to the cobalt-nickel ferrite, and treat at 200 °C for 12 h in a high-pressure reaction kettle. Wash the obtained product and then dry to obtain magnetic biochar.

[0060] Preparation Example 2

[0061] The preparation of modified biochar is as follows: Add 0.2 g of sodium alginate and 0.15 g of phosphatidylserine to 70 mL of deionized water. After stirring evenly, add 1 g of magnetic biochar, heat up to 50 °C, stir for 10 min, then add 4 mL of glutaraldehyde, continue to stir for 2 h, filter, wash the filter cake with deionized water and then dry to obtain modified biochar.

[0062] Magnetic biochar is prepared through the following steps: 8.43 g of cobalt sulfate, 0.876 g of nickel sulfate and 17.778 g of iron sulfate were added to 80 mL of deionized water. After stirring in a water bath at 40 °C for 1 h, the temperature was lowered to 30 °C, and a sodium hydroxide solution with a concentration of 3 mol / L was added dropwise. After the addition was complete, the temperature was raised to 90 °C and stirred for 1 h, then transferred to an autoclave and treated at 200 °C for 12 h. The resulting product was washed with distilled water until the washing liquid was neutral, dried, ground and passed through a 200-mesh sieve to obtain cobalt-nickel ferrite. 9 g of wood chips with a particle size of 0.15 - 0.25 mm were added to the cobalt-nickel ferrite, and it was treated in a high-pressure reactor at 200 °C for 12 h. The resulting product was washed and dried to obtain magnetic biochar.

[0063] Preparation Example 3

[0064] The preparation of the modified biochar is as follows: 0.3 g of sodium alginate and 0.2 g of phosphatidylserine were added to 100 mL of deionized water. After stirring evenly, 1 g of magnetic biochar was added, and the temperature was raised to 50 °C. After stirring for 10 min, 4 mL of glutaraldehyde was added, and stirring was continued for 2.5 h. Then it was filtered, and the filter cake was washed with deionized water and dried to obtain the modified biochar.

[0065] The magnetic biochar was prepared through the following steps: 8.43 g of cobalt sulfate, 0.876 g of nickel sulfate and 17.778 g of iron sulfate were added to 100 mL of deionized water. After stirring in a water bath at 60 °C for 1 h, the temperature was lowered to 30 °C, and a sodium hydroxide solution with a concentration of 3 mol / L was added dropwise. After the addition was complete, the temperature was raised to 90 °C and stirred for 1 h, then transferred to an autoclave and treated at 200 °C for 12 h. The resulting product was washed with distilled water until the washing liquid was neutral, dried, ground and passed through a 100-mesh sieve to obtain cobalt-nickel ferrite. 8 g of pine wood chips that had passed through a 100-mesh sieve were added to the cobalt-nickel ferrite, and it was treated in a high-pressure reactor at 200 °C for 12 h. The resulting product was washed and dried to obtain magnetic biochar.

[0066] Control Example 1

[0067] The preparation of the modified biochar is different from that of Preparation Example 1 in that the sodium alginate in Preparation Example 1 was replaced with an equal mass of phosphatidylserine.

[0068] Control Example 2

[0069] The preparation of the modified biochar is different from that of Preparation Example 1 in that the phosphatidylserine in Preparation Example 1 was replaced with an equal mass of sodium alginate.

[0070] Control Example 3

[0071] This comparative example is magnetic biochar, and the preparation process is the same as that of Preparation Example 1.

[0072] Control Example 4

[0073] This comparative example is biochar, and the preparation process is as follows: Add 10 g of pine wood sawdust passed through a 100-mesh sieve and 50 mL of deionized water into a reaction kettle, treat at 200 °C for 12 h, wash the product three times alternately with deionized water and absolute ethanol, dry, grind, and pass through a 100-mesh sieve to obtain biochar.

[0074] Example 1

[0075] A treatment process for rural domestic sewage includes the following steps: S1. Concentrate rural domestic sewage, separate it through a grille, and then introduce it into a sedimentation tank. Add basic aluminum chloride to the sedimentation tank, stir for 10 min, then add polyacrylamide. The dosage of basic aluminum chloride is 20 g per ton of rural domestic sewage; the dosage of polyacrylamide is 10 g per ton of rural domestic sewage. Continue to stir for 20 min, and the treated effluent is recorded as pretreated sewage. S2. Introduce the pretreated sewage into an anaerobic tank, and the sewage in the anaerobic tank overflows into an aerobic tank. Denitrifying bacteria are added to the anaerobic tank, and the addition amount of denitrifying bacteria is 2% of the mass of the sewage in the aerobic tank. Nitrifying bacteria and modified biochar-supported EM bacteria are added to the aerobic tank. The addition amount of nitrifying bacteria in the aerobic tank is 1% of the mass of the sewage in the aerobic tank, and the addition amount of modified biochar-supported EM bacteria is 1% of the mass of the sewage in the aerobic tank. Finally, it enters a purification tank through a water pipe, and the effluent from the purification tank is the discharged water.

[0076] The modified biochar-supported EM bacteria are prepared through the following steps: Dilute the EM bacterial liquid with distilled water to 4 times, then add the modified biochar prepared in Preparation Example 1. Control the dosage ratio of the EM bacterial liquid to the modified biochar as 10 mL: 1.5 g, at a temperature of 25 °C, oscillate and treat for 120 min at a rotation speed of 160 r / min, filter, and dry to obtain the modified biochar-supported EM bacteria.

[0077] The EM bacterial liquid is obtained by activating and fermenting EM bacterial strain dry powder. Specifically, inoculate the EM bacterial strain dry powder on an EM culture medium, then place it in a sealed plastic bottle, at 36 ± 1 °C, 200 r / min, release gas once a day, oscillate and culture for 48 h to obtain the activated EM bacterial liquid. Mix the activated EM bacterial liquid with the EM culture medium at a volume ratio of 1:18, keep it at a constant temperature of 36 °C, oscillate at 160 r / min, release gas once a day, and oscillate and culture for 72 h to obtain the EM bacterial liquid.

[0078] The composition of the EM bacterial culture medium is: 100 g of brown sugar, 1 g of urea, 1 g of NaCl, 1 L of distilled water. After dissolution, adjust the pH to 7.0 ± 0.2.

[0079] The hydraulic retention time of the anaerobic tank is 5 h, and the hydraulic retention time of the aerobic tank is 6 h. An aeration device is arranged in the aerobic tank, and the aeration time is 2 h per 24 h.

[0080] The purification tank has a two-layer structure. The upper layer is an adsorption layer, and the lower layer is a packing layer. The thickness of the adsorption layer is 40 cm, and the thickness of the packing layer is 15 cm. The adsorption layer contains activated carbon, expanded perlite and straw, and the packing layer contains clay red bricks and iron tailings.

[0081] The mass ratio of activated carbon, expanded perlite and straw is 1:1:6; the mass ratio of the clay red bricks and iron tailings is 3:1.

[0082] The particle sizes of activated carbon, expanded perlite and straw are independently 0.05 - 0.15 cm; the particle sizes of clay red bricks and iron tailings are independently 0.8 - 2 cm.

[0083] Example 2

[0084] A treatment process for rural domestic sewage includes the following steps: S1. Concentrate the rural domestic sewage, separate it through a grille, and then introduce it into a sedimentation tank. Add aluminum sulfate to the sedimentation tank, stir for 10 min, then add polyacrylamide. The dosage of aluminum sulfate is 25 g per ton of rural domestic sewage; the dosage of polyacrylamide is 15 g per ton of rural domestic sewage. Continue to stir for 25 min, and the treated effluent is recorded as pretreated sewage. S2. Introduce the pretreated sewage into the anaerobic tank, and the sewage in the anaerobic tank overflows into the aerobic tank. Denitrifying bacteria are added to the anaerobic tank, and the addition amount of denitrifying bacteria is 3% of the mass of the sewage in the aerobic tank. Nitrifying bacteria and modified biochar-loaded EM bacteria are added to the aerobic tank. The addition amount of nitrifying bacteria in the aerobic tank is 2% of the mass of the sewage in the aerobic tank, and the addition amount of modified biochar-loaded EM bacteria is 1.5% of the mass of the sewage in the aerobic tank. Finally, it enters the purification tank through a water pipe, and the effluent from the purification tank is the discharged water.

[0085] The modified biochar-loaded EM bacteria are prepared through the following steps: Dilute the EM bacteria liquid with distilled water to 5 times, then add the modified biochar prepared in Preparation Example 1. Control the dosage ratio of the EM bacteria liquid and the modified biochar to be 10 mL:2 g, oscillate at a temperature of 25 °C and a rotation speed of 160 r / min for 140 min, filter, and dry to obtain the modified biochar-loaded EM bacteria.

[0086] The preparation process of the EM bacteria liquid is the same as that in Example 1.

[0087] The hydraulic retention time of the anaerobic tank is 6 h, and the hydraulic retention time of the aerobic tank is 7 h. An aeration device is arranged in the aerobic tank, and the aeration time is 3 h per 24 h.

[0088] The purification tank has a two-layer structure, with an upper adsorption layer and a lower packing layer. The thickness of the adsorption layer is 50 cm, and the thickness of the packing layer is 20 cm. The adsorption layer contains activated carbon, expanded perlite, and straw, and the packing layer contains clay red bricks and iron tailings.

[0089] The mass ratio of activated carbon, expanded perlite, and straw is 8:10:31; the mass ratio of the clay red bricks and iron tailings is 5:1.

[0090] The particle sizes of activated carbon, expanded perlite, and straw are independently 0.05 - 0.15 cm; the particle sizes of clay red bricks and iron tailings are independently 0.8 - 2 cm.

[0091] Example 3

[0092] A treatment process for rural domestic sewage includes the following steps: S1. Concentrate the rural domestic sewage, separate it through a grille, and then introduce it into a sedimentation tank. Add basic aluminum chloride to the sedimentation tank, stir for 10 min, then add polyacrylamide. The dosage of basic aluminum chloride is 30 g per ton of rural domestic sewage; the dosage of polyacrylamide is 20 g per ton of rural domestic sewage. Continue to stir for 30 min, and the treated effluent is recorded as pretreated sewage. S2. Introduce the pretreated sewage into an anaerobic tank, and the sewage in the anaerobic tank overflows into an aerobic tank. Denitrifying bacteria are added to the anaerobic tank, and the addition amount of denitrifying bacteria is 5% of the mass of the sewage in the aerobic tank. Nitrifying bacteria and modified biochar-supported EM bacteria are added to the aerobic tank. The addition amount of nitrifying bacteria in the aerobic tank is 3% of the mass of the sewage in the aerobic tank, and the addition amount of modified biochar-supported EM bacteria is 2% of the mass of the sewage in the aerobic tank. Finally, it enters the purification tank through a water pipe, and the effluent from the purification tank is the discharged water.

[0093] The modified biochar-supported EM bacteria are prepared through the following steps: Dilute the EM bacteria solution with distilled water to 5 times, then add the modified biochar prepared in Preparation Example 1. Control the dosage ratio of the EM bacteria solution to the modified biochar to be 10 mL:2.5 g, oscillate at a temperature of 25°C and a rotation speed of 160 r / min for 150 min, filter, and dry to obtain the modified biochar-supported EM bacteria.

[0094] The preparation process of the EM bacteria solution is the same as that in Example 1.

[0095] The hydraulic retention time of the anaerobic tank is 7 h, and the hydraulic retention time of the aerobic tank is 8 h. An aeration device is arranged in the aerobic tank, and the aeration time is 2 h every 24 h.

[0096] The purification pond has a two-layer structure, with an upper adsorption layer and a lower packing layer. The thickness of the adsorption layer is 60 cm, and the thickness of the packing layer is 25 cm. The adsorption layer contains activated carbon, expanded perlite, and straw, and the packing layer contains clay red bricks and iron tailings.

[0097] The mass ratio of activated carbon, expanded perlite, and straw is 10:10:40; the mass ratio of the clay red bricks and iron tailings is 5:3.

[0098] The particle sizes of activated carbon, expanded perlite, and straw are independently 0.05 - 0.15 cm; the particle sizes of clay red bricks and iron tailings are independently 0.8 - 2 cm.

[0099] Example 4

[0100] A treatment process for rural domestic sewage, compared with Example 1, is different in that the modified biochar in Example 1 is replaced with the product obtained in Preparation Example 2 of equal mass.

[0101] Example 5

[0102] A treatment process for rural domestic sewage, compared with Example 1, is different in that the modified biochar in Example 1 is replaced with the product obtained in Preparation Example 3 of equal mass.

[0103] Example 6

[0104] A treatment process for rural domestic sewage, compared with Example 1, is different in that in this example, the dosage ratio of EM bacterial liquid and modified biochar is controlled at 10 mL:2 g.

[0105] Example 7

[0106] A treatment process for rural domestic sewage, compared with Example 1, is different in that in this example, the dosage ratio of EM bacterial liquid and modified biochar is controlled at 10 mL:2.5 g.

[0107] Example 8

[0108] A treatment process for rural domestic sewage, compared with Example 1, is different in that in this Example 1, the addition amount of nitrifying bacteria in the aerobic tank is 3% of the mass of the sewage in the aerobic tank, and the addition amount of modified biochar loaded with EM bacteria is 2% of the mass of the sewage in the aerobic tank. The preparation process of the modified biochar loaded with EM bacteria is the same as that in Example 1.

[0109] Control Example 1

[0110] A treatment process for rural domestic sewage, compared with Example 1, is different in that the modified biochar in Example 1 is replaced with the product obtained in Control Example 1 of equal mass.

[0111] Control Example 2

[0112] A treatment process for rural domestic sewage. Compared with Example 1, the difference is that the modified biochar in Example 1 is replaced with the product obtained in Comparative Example 2 with the same mass.

[0113] Comparative Example 3

[0114] A treatment process for rural domestic sewage. Compared with Example 1, the difference is that the modified biochar in Example 1 is replaced with the substance in Comparative Example 3 with the same mass.

[0115] Comparative Example 4

[0116] A treatment process for rural domestic sewage. Compared with Example 1, the difference is that the modified biochar in Example 1 is replaced with the substance in Comparative Example 4 with the same mass.

[0117] Comparative Example 5

[0118] A treatment process for rural domestic sewage. Compared with Example 1, the difference is that the modified biochar loaded with EM bacteria in Example 1 is replaced with the EM bacteria liquid with the same mass, and the preparation process of the EM bacteria liquid is the same as that in Example 1.

[0119] The treatment processes provided by the above Examples 1 - 8 and Comparative Examples 1 - 5 are used to treat the domestic sewage generated in a certain town in Anhui. The quality of this domestic sewage is as follows: the COD content is 865 mg / L, the TN content is 214.6 mg / L, and the TP content is 24.5 mg / L. After the treatment is completed, the effluent from the purification tank is detected, and the results are shown in Table 1: Table 1

[0120] It can be seen from the test results in Table 1 that for the effluent water obtained by the treatment processes of Examples 1 - 8, the COD content ≤ 16.2 mg / L, the TN content ≤ 5.14 mg / L, and the TP content ≤ 0.08 mg / L, and the effluent water quality is significantly better than that of Comparative Examples 1 - 5.

[0121] Specifically, it can be seen from the test results in Example 1, Comparative Example 1, and Comparative Example 2 that the effluent water quality of Example 1 is significantly better than that of Comparative Example 1 and Comparative Example 2, indicating that when using sodium alginate or phosphatidylserine alone as a modifier during the preparation of the modified biochar, the modified biochar loaded with EM bacteria has a poor purification effect on sewage. However, in the present invention, sodium alginate and phosphatidylserine are used together as modifiers, and there is a synergistic effect between them. The modified biochar loaded with EM bacteria prepared has a good purification effect on sewage.

[0122] It can be seen from the test results in Example 1 and Comparative Example 3 that by omitting the use of sodium alginate and phosphatidylserine and directly using magnetic biochar as a carrier to load EM bacteria agents, the modified biochar loaded with EM bacteria has a poor sewage purification effect.

[0123] It can be seen from the test results in Example 1 and Comparative Examples 4 and 5 that compared with using biochar as a carrier for EM bacteria agents or directly adding EM bacteria agents to the aerobic tank, the effluent water quality in Example 1 is higher. The reason is that the modified biochar in Example 1 is magnetic biochar with sodium alginate and phosphatidylserine on its surface, and the weak magnetic field generated by it can promote the aggregation of paramagnetic oxygen near the modified biochar loaded with EM bacteria, improving the contact degree between EM bacteria and oxygen, which helps to accelerate the reproduction and metabolism of EM bacteria. Moreover, the magnetic effect has a good stimulating effect on EM bacteria, which can catalyze the enzyme activity of EM bacteria, thereby enhancing the sewage purification effect of EM bacteria. In addition, on the one hand, the phosphatidylserine carried by the modified biochar can provide certain nutrients (N and P nutrient elements) for EM bacteria, which is beneficial to improving the biological activity of EM bacteria. On the other hand, it binds to organic pollutants in sewage through hydrogen bond action or hydrophobic interaction, which is beneficial to promoting the rapid degradation of pollutants by EM bacteria.

[0124] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0125] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for treating domestic sewage in villages and towns, characterized in that: The following steps are involved: S1. The domestic sewage of villages and towns is concentrated and separated through the grid and then passed into the sedimentation tank, a coagulant is added to the sedimentation tank, and a flocculant is added after stirring. The treated effluent is recorded as pre-treated sewage; S2, the pre-treated sewage is passed into the anaerobic tank, the sewage in the anaerobic tank enters the aerobic tank through overflow, nitrifying bacteria and modified biochar loaded EM bacteria are added to the aerobic tank, and finally enters the purification tank through the water pipe, and the effluent of the purification tank is the discharge water; The modified biochar preparation raw materials include sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde.

2. A process for treating domestic sewage in villages and towns according to claim 1, characterized in that: The modified biochar loaded with EM bacteria is prepared by the following steps: The EM bacterial solution was diluted to 2-5 times with distilled water, and then the modified biochar was added, shaken for 120-150 minutes, filtered, and dried to obtain the modified biochar loaded with EM bacteria.

3. A process for treating domestic sewage in villages and towns according to claim 2, characterized in that: The dosage ratio of EM bacterial solution and modified biochar is 10mL:1.5-2.5g.

4. A process for treating domestic sewage in villages and towns according to claim 2, characterized in that: The EM bacterial liquid is obtained by activating and fermenting EM bacterial dry powder.

5. A process for treating domestic sewage in villages and towns according to claim 1, characterized in that: The modified biochar is prepared by the following steps: Sodium alginate and phosphatidylserine were added into deionized water, and magnetic biochar was added after stirring evenly. The temperature was raised to 50° C., and glutaraldehyde was added after stirring for 10 min. The stirring was continued for 1.5-2.5 h, and the filter cake was washed with deionized water and dried to obtain modified biochar.

6. A process for treating domestic sewage in villages and towns according to claim 5, characterized in that: The dosage ratio of sodium alginate, phosphatidylserine, deionized water, magnetic biochar and glutaraldehyde is 0.15-0.3g:0.1-0.2g:50-100mL:1g:4mL.

7. A process for treating domestic sewage in villages and towns according to claim 5, characterized in that: The magnetic biochar is prepared by the following steps: Cobalt sulfate, nickel sulfate and ferric sulfate are added into deionized water, stirred in a water bath at 40-60°C for 1 hour, then cooled to 30°C, sodium hydroxide solution is added dropwise, and after the addition is completed, the temperature is raised to 90°C and stirred for 1 hour, then transferred to an autoclave and treated at 200°C for 12 hours. The obtained product is washed with distilled water until the washing liquid is neutral, dried and ground to obtain cobalt-nickel ferrite. Sawdust is added into the cobalt-nickel ferrite, and the product is treated at 200°C for 12 hours in an autoclave. The obtained product is washed and dried to obtain magnetic biochar.

8. A process for treating domestic sewage in villages and towns according to claim 5, characterized in that: The dosage ratio of cobalt sulfate, nickel sulfate, iron sulfate, deionized water, sodium hydroxide solution and sawdust is 8.43g:0.88g:17.78g:50-100mL:50mL:8-10g, and the concentration of sodium hydroxide solution is 3mol / L.

9. A process for treating domestic sewage in villages and towns according to claim 1, characterized in that: The amount of nitrifying bacteria added to the aerobic pool is 1-3% of the mass of the sewage in the aerobic pool, and the amount of modified biochar-loaded EM bacteria added is 1-2% of the mass of the sewage in the aerobic pool.

10. A process for treating domestic sewage in villages and towns according to claim 1, characterized in that: The hydraulic retention time of the aerobic pool is 6-8 hours. An aeration device is installed in the aerobic pool, and the aeration time is 2-3 hours every 24 hours.

Images