A treatment process for domestic sewage in villages and towns

Abstract

The invention provides a treatment process for domestic sewage in villages and towns, belonging to the technical field of sewage treatment, and comprising the following steps: S1, collecting and separating the domestic sewage in villages and towns through a grid, and then passing the sewage into a sedimentation tank, adding a coagulant into the sedimentation tank, stirring, and adding a flocculant, and the treated effluent is recorded as pretreated sewage; S2, passing the pretreated sewage into an anaerobic tank, the sewage in the anaerobic tank enters an aerobic tank through overflow, the sewage in the aerobic tank is added with nitrifying bacteria and modified biochar loaded with EM bacteria, and finally enters a purification tank through a water pipe, and the effluent of the purification tank is discharge water; the raw materials for preparing the modified biochar include sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde; the invention combines the modified biochar loaded with EM bacteria and nitrifying bacteria in the aerobic tank, so that a close symbiotic relationship is formed between the EM bacteria and the nitrifying bacteria, and the phosphorus, ammonia nitrogen and organic matter contents in the sewage are synergistically reduced, thereby solving the problem of poor treatment effect of domestic sewage in villages and towns.

Description

Technical Field

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

[0002] At present, the main treatment method for village and town sewage is biochemical treatment, including anaerobic treatment and aerobic treatment. Nitrifying bacteria are generally added alone to the aerobic pool, but the nitrifying bacteria are of a single species and focus on denitrification treatment, and the treatment effect on organic matter is poor. EM bacteria contain a variety of aerobic and facultative anaerobic microorganisms, such as photosynthetic bacteria, lactic acid bacteria, yeasts, actinomycetes, fungi, etc. The bacterial community composition is load-bearing and the structure is stable. They can give full play to the symbiotic, mutualistic and competitive relationship between each other, and can remove pollutants in village and town black water through biodegradation metabolism. However, EM bacteria are water-soluble liquids. When treating sewage alone, there is a lack of carriers, which makes its nitrogen and phosphorus removal rate not high, the effluent purification effect is poor, and it is also easy to cause bacterial loss. Summary of the Invention

[0003] The purpose of the present invention is to provide a treatment process for domestic sewage in villages and towns, so as to solve the problem of poor treatment effect of existing domestic sewage in villages and towns.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A process for treating domestic sewage in villages and towns comprises the following steps:

[0006] S1. Collect the domestic sewage from villages and towns and separate it through a grid before passing 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.

[0007] S2. The pretreated sewage is passed into the anaerobic tank. The sewage in the anaerobic tank flows into the aerobic tank through overflow. Nitrifying bacteria and modified biochar-loaded EM bacteria are added to the aerobic tank. Finally, it enters the purification tank through the water pipe. The effluent from the purification tank is the discharge water.

[0008] Furthermore, the modified biochar loaded with EM bacteria is prepared by the following steps:

[0009] 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 EM bacteria.

[0010] Furthermore, the oscillation treatment temperature is 25° C. and the rotation speed is 160 r / min.

[0011] Furthermore, the usage ratio of EM bacterial solution and modified biochar is 10 mL: 1.5-2.5 g.

[0012] Modified biochar is used as the EM bacteria carrier, which has rich pore structure, polar groups and long hydrophobic chains. The pore structure can provide more attachment sites for the EM bacterial solution, which is conducive to the full contact and binding of the bacterial agent and the carrier. The hydrophilic groups combine with the bacterial agent through hydrogen bonds and other effects, enhancing the load stability. The hydrophobic long chains enhance the adsorption performance of the modified biochar for pollutants through hydrophobic interactions, thereby improving the degradation effect of EM bacteria on pollutants.

[0013] Furthermore, the EM bacterial liquid is obtained by activating and fermenting EM bacterial dry powder. Specifically, the EM bacterial dry powder is inoculated on the EM culture medium, and then placed in a sealed plastic bottle, 36±1°C, 200r / min, air is released once a day, and shaking culture is carried out for 48 hours to obtain the activated EM bacterial liquid. The activated EM bacterial liquid and EM culture medium are mixed in a volume ratio of 1:18-20, kept at a constant temperature of 36°C, shaken at 160r / min, air is released once a day, and shaking culture is carried out for 72 hours to obtain the EM bacterial liquid.

[0014] Furthermore, the EM bacterial culture medium is composed of: 100 g brown sugar, 1 g urea, 1 g NaCl, and 1 L distilled water, and the pH is adjusted to 7.0±0.2 after dissolution.

[0015] Furthermore, the raw materials for preparing the modified biochar include sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde.

[0016] Furthermore, the modified biochar is prepared by the following steps:

[0017] Sodium alginate and phosphatidylserine were added to deionized water, stirred evenly, and then magnetic biochar was added. The temperature was raised to 50° C., stirred for 10 minutes, and then glutaraldehyde was added. The stirring was continued for 1.5-2.5 hours, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain modified biochar.

[0018] 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. Sodium alginate and phosphatidylserine are used as modifiers and glutaraldehyde is used as a cross-linking agent to introduce sodium alginate and phosphatidylserine on the surface of magnetic biochar to obtain modified biochar.

[0019] Furthermore, the magnetic biochar is prepared by the following steps:

[0020] Cobalt sulfate, nickel sulfate and ferric sulfate are added to deionized water, stirred in a water bath at 40-60°C for 1 hour, then cooled to 30°C, and sodium hydroxide solution is added dropwise. After the addition is complete, 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 resulting product is washed with distilled water until the washing liquid is neutral, dried and ground to obtain cobalt-nickel ferrite. Sawdust is added to the cobalt-nickel ferrite, and the product is treated at 200°C in an autoclave for 12 hours. The resulting product is washed and dried to obtain magnetic biochar.

[0021] Furthermore, the usage ratio of cobalt sulfate, nickel sulfate, ferric sulfate, deionized water, sodium hydroxide solution and sawdust is 8.43g:0.88g:17.78g:50-100mL:50mL:8-10g, the concentration of sodium hydroxide solution is 3mol / L, and sawdust is used as the carbon source, cobalt sulfate, nickel sulfate and ferric sulfate are used as magnetic raw materials. Cobalt-nickel ferrite-biochar with excellent magnetic properties is prepared by a hydrothermal method.

[0022] Furthermore, the usage amount of the coagulant is 20-30 g per ton of village and town domestic sewage; the usage amount of the flocculant is 10-20 g per ton of village and town domestic sewage.

[0023] Furthermore, the coagulant is basic aluminum chloride and / or aluminum sulfate.

[0024] Furthermore, the flocculant is polyacrylamide.

[0025] Furthermore, 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.

[0026] Furthermore, denitrifying bacteria are added to the anaerobic tank, and the amount of denitrifying bacteria added is 2-5% of the mass of the sewage in the anaerobic tank.

[0027] Furthermore, the hydraulic retention time of the anaerobic tank is 5-7 hours, and the hydraulic retention time of the aerobic tank is 6-8 hours. An aeration device is provided in the aerobic tank, and the aeration time is 2-3 hours every 24 hours.

[0028] Furthermore, the purification pool has a two-layer structure, the upper layer is an adsorption layer, and the lower layer is a filler layer. The thickness of the adsorption layer is 40-60 cm, and the thickness of the filler layer is 15-25 cm; the adsorption layer contains activated carbon, expanded perlite and straw, and the filler layer contains clay red bricks and iron tailings.

[0029] Furthermore, 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 brick and iron tailings is 3-5:1-3.

[0030] Furthermore, the particle sizes of the activated carbon, expanded perlite and straw are independently 0.05-0.15 cm; and the particle sizes of the clay red brick and iron tailings are independently 0.8-2 cm.

[0031] Beneficial effects of the present invention:

[0032] 1. The present invention provides a process for treating sewage in villages and towns, which sequentially reduces the pollutant content in the effluent through flocculation treatment, anaerobic treatment, aerobic treatment, and purification treatment. In particular, the combined use of modified biochar-loaded EM bacteria and nitrifying bacteria in an aerobic tank forms a close symbiotic relationship between the EM bacteria and nitrifying bacteria, synergistically reducing the phosphorus, ammonia nitrogen, and organic matter contents 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 domestic sewage in villages and towns.

[0033] 2. The present invention uses modified biochar as a carrier for EM bacteria, and provides a relatively stable microecological environment for EM bacteria through loading treatment, which is conducive to its growth, reproduction and metabolic activities, reduces the loss or destruction of EM bacteria caused by water flow impact during sewage treatment, improves its stability, and is conducive to increasing the contact area between EM bacteria and pollutants in sewage, thereby enabling EM bacteria to fully exert their degradation and transformation functions and remove pollutants in the environment.

[0034] 3. The modified biochar in the present invention is a magnetic biochar carrying sodium alginate and phosphatidylserine on its surface. Its good magnetic properties give it the characteristic of easy separation, and the weak magnetic field it generates can promote the aggregation of paramagnetic oxygen near the modified biochar-loaded EM bacteria, thereby increasing the contact degree between EM bacteria and oxygen, and helping to accelerate the reproduction and metabolism of EM bacteria. The magnetic effect has a good stimulating effect on EM bacteria, which can catalyze the enzyme activity of EM bacteria, thereby improving the purification effect of EM bacteria on sewage. In addition, the phosphatidylserine carried by the modified biochar can provide certain nutrients (N and P nutrients) for EM bacteria, which is beneficial to improving the biological activity of EM bacteria. On the other hand, it combines with organic pollutants in sewage through hydrogen bonding or hydrophobic interactions, which is beneficial to promoting the rapid degradation of pollutants by EM bacteria. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers 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 all mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, c can be single or multiple.

[0037] The terms used in the examples of this application are for the purpose of describing specific implementation rules only and are not intended to limit this application. The singular forms "a", "an", "the" and "the" used in the implementation rules of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0038] It should be understood that in the various embodiments of the present application, the size of the serial number 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 on the implementation process of the implementation regulations of this application.

[0039] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0040] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0041] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0042] In order to solve the problem of poor domestic sewage treatment effect to a certain extent, the present application provides a treatment process for domestic sewage in villages and towns, comprising the following steps:

[0043] S1. Collect the domestic sewage from villages and towns and separate it through a grid before passing 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.

[0044] S2. The pretreated sewage is passed into the anaerobic tank. The sewage in the anaerobic tank flows into the aerobic tank through overflow. Nitrifying bacteria and modified biochar-loaded EM bacteria are added to the aerobic tank. Finally, it enters the purification tank through the water pipe. The effluent from the purification tank is the discharge water.

[0045] In some embodiments, the modified biochar loaded with EM bacteria is prepared by the following steps:

[0046] 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 EM bacteria.

[0047] In some specific embodiments, the shaking treatment temperature is 25° C. and the rotation speed is 160 r / min.

[0048] In some specific embodiments, the usage ratio of EM bacterial solution and modified biochar is 10 mL: 1.5-2.5 g.

[0049] In some embodiments, the EM bacterial liquid is obtained by activating and fermenting EM bacterial dry powder. Specifically, the EM bacterial dry powder is inoculated on the EM culture medium, and then placed in a sealed plastic bottle, 36±1°C, 200r / min, and air is released once a day, and shaken culture is carried out for 48 hours to obtain the activated EM bacterial liquid. The activated EM bacterial liquid and EM culture medium are mixed in a volume ratio of 1:18-20, constant temperature of 36°C, oscillation of 160r / min, air is released once a day, and shaken culture is carried out for 72 hours to obtain the EM bacterial liquid.

[0050] In some specific embodiments, the EM bacterial culture medium is composed of: 100 g brown sugar, 1 g urea, 1 g NaCl, and 1 L distilled water, and the pH is adjusted to 7.0±0.2 after dissolution.

[0051] In some embodiments, the modified biochar preparation raw materials include sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde.

[0052] In some specific embodiments, the modified biochar is prepared by the following steps:

[0053] Sodium alginate and phosphatidylserine were added to deionized water, stirred evenly, and then magnetic biochar was added. The temperature was raised to 50° C., stirred for 10 minutes, and then glutaraldehyde was added. The stirring was continued for 1.5-2.5 hours, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain modified biochar.

[0054] In some embodiments, the usage 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.

[0055] In some specific embodiments, the magnetic biochar is prepared by the following steps:

[0056] Cobalt sulfate, nickel sulfate and ferric sulfate are added to deionized water, stirred in a water bath at 40-60°C for 1 hour, then cooled to 30°C, and sodium hydroxide solution is added dropwise. After the addition is complete, 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 resulting product is washed with distilled water until the washing liquid is neutral, dried and ground to obtain cobalt-nickel ferrite. Sawdust is added to the cobalt-nickel ferrite, and the product is treated at 200°C in an autoclave for 12 hours. The resulting product is washed and dried to obtain magnetic biochar.

[0057] In some specific embodiments, the ratio of cobalt sulfate, nickel sulfate, ferric sulfate, deionized water, sodium hydroxide solution and sawdust is 8.43 g: 0.876 g: 17.778 g: 50-100 mL: 50 mL: 8-10 g, and the concentration of sodium hydroxide solution is 3 mol / L.

[0058] In some embodiments, the amount of the coagulant used is 20-30 g per ton of village and town domestic sewage; the amount of the flocculant used is 10-20 g per ton of village and town domestic sewage.

[0059] In some embodiments, the coagulant is basic aluminum chloride and / or aluminum sulfate.

[0060] In some embodiments, the flocculant is polyacrylamide.

[0061] In some embodiments, the amount of nitrifying bacteria added to the aerobic tank is 1-3% of the mass of the sewage in the aerobic tank, and the amount of modified biochar loaded with EM bacteria added is 1-2% of the mass of the sewage in the aerobic tank.

[0062] In some embodiments, denitrifying bacteria are added to the anaerobic tank, and the amount of denitrifying bacteria added is 2-5% of the mass of the sewage in the aerobic tank.

[0063] In some embodiments, the hydraulic retention time of the anaerobic tank is 5-7 hours, and the hydraulic retention time of the aerobic tank is 6-8 hours. The aerobic tank is provided with an aeration device, and the aeration time is 2-3 hours every 24 hours.

[0064] In some embodiments, the purification tank has a two-layer structure, the upper layer is an adsorption layer, and the lower layer is a filler layer. The thickness of the adsorption layer is 40-60 cm, and the thickness of the filler layer is 15-25 cm; the adsorption layer contains activated carbon, expanded perlite and straw, and the filler layer contains clay red bricks and iron tailings.

[0065] 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 brick and iron tailings is 3-5:1-3.

[0066] In some embodiments, the particle sizes of activated carbon, expanded perlite, and straw are independently 0.05-0.15 cm; and the particle sizes of clay red brick and iron tailings are independently 0.8-2 cm.

[0067] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0068] The EM bacterial strain powder used in this application was purchased from Henan Zhongguang Group. It is a yellow-brown dry powdered composite bacterial agent composed of bifidobacteria, lactic acid bacteria, Bacillus, photosynthetic bacteria, yeast, actinomycetes, and acetic acid bacteria. Sodium alginate was purchased from Qingdao Mingyue Seaweed Group Co., Ltd. with a viscosity (25°C) of 500-550 mPa·s and 250-400 mPa·s.

[0069] Preparation Example 1

[0070] The preparation steps of modified biochar are as follows:

[0071] 0.15 g of sodium alginate and 0.1 g of phosphatidylserine were added to 50 mL of deionized water, stirred evenly, and then 1 g of magnetic biochar was added. The temperature was raised to 50 °C, stirred for 10 min, and then 4 mL of glutaraldehyde was added. The stirring was continued for 1.5 h, filtered, and the filter cake was washed with deionized water and dried to obtain modified biochar.

[0072] Magnetic biochar is made through the following steps:

[0073] 8.43 g of cobalt sulfate, 0.88 g of nickel sulfate and 17.78 g of ferric sulfate were added to 50 mL of deionized water, stirred in a water bath at 40 ° C for 1 hour, then cooled to 30 ° C, and a 3 mol / L sodium hydroxide solution was added dropwise. After the addition was completed, the temperature was 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 was washed with distilled water until the washing liquid was neutral, dried, and ground through a 200 mesh sieve to obtain cobalt-nickel ferrite. 10 g of sawdust with a particle size of 0.15-0.25 mm was added to the cobalt-nickel ferrite. The sawdust was treated in an autoclave at 200 ° C for 12 hours. The obtained product was washed and dried to obtain magnetic biochar.

[0074] Preparation Example 2

[0075] The preparation steps of modified biochar are as follows:

[0076] 0.2 g of sodium alginate and 0.15 g of phosphatidylserine were added to 70 mL of deionized water, stirred evenly, and then 1 g of magnetic biochar was added. The temperature was raised to 50 °C, stirred for 10 min, and then 4 mL of glutaraldehyde was added. The stirring was continued for 2 h, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain modified biochar.

[0077] Magnetic biochar is made through the following steps:

[0078] 8.43 g of cobalt sulfate, 0.876 g of nickel sulfate and 17.778 g of ferric sulfate were added to 80 mL of deionized water, stirred in a water bath at 40 ° C for 1 hour, and then cooled to 30 ° C. A 3 mol / L sodium hydroxide solution was added dropwise. After the addition was completed, the temperature was 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 was washed with distilled water until the washing liquid was neutral, dried, and ground through a 200 mesh sieve to obtain cobalt-nickel ferrite. 9 g of sawdust with a particle size of 0.15-0.25 mm was added to the cobalt-nickel ferrite. The sawdust was treated in an autoclave at 200 ° C for 12 hours. The obtained product was washed and dried to obtain magnetic biochar.

[0079] Preparation Example 3

[0080] The preparation steps of modified biochar are as follows:

[0081] 0.3 g of sodium alginate and 0.2 g of phosphatidylserine were added to 100 mL of deionized water, stirred evenly, and then 1 g of magnetic biochar was added. The temperature was raised to 50 °C, stirred for 10 min, and then 4 mL of glutaraldehyde was added. The stirring was continued for 2.5 h, filtered, and the filter cake was washed with deionized water and dried to obtain modified biochar.

[0082] Magnetic biochar is made through the following steps:

[0083] 8.43 g of cobalt sulfate, 0.876 g of nickel sulfate and 17.778 g of ferric sulfate were added to 100 mL of deionized water, stirred in a water bath at 60 ° C for 1 hour, and then cooled to 30 ° C. A 3 mol / L sodium hydroxide solution was added dropwise. After the addition was completed, the temperature was 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 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 sawdust was added to the cobalt-nickel ferrite, and the pine sawdust was passed through a 100 mesh sieve. The product was treated at 200 ° C for 12 hours in an autoclave. The obtained product was washed and dried to obtain magnetic biochar.

[0084] Comparative Example 1

[0085] The preparation of the modified biochar is different from that of Preparation Example 1 in that the sodium alginate in Preparation Example 1 is replaced by phosphatidylserine of equal mass.

[0086] Comparative Example 2

[0087] The preparation of the modified biochar is different from that of Preparation Example 1, in that the phosphatidylserine in Preparation Example 1 is replaced by an equal mass of sodium alginate.

[0088] Comparative Example 3

[0089] This comparative example is magnetic biochar, and the preparation process is the same as that of Preparation Example 1.

[0090] Comparative Example 4

[0091] This comparative example is biochar, and the preparation process is as follows:

[0092] 10 g of pine sawdust passed through a 100-mesh sieve and 50 mL of deionized water were added to a reactor and treated at 200°C for 12 h. The product was washed alternately with deionized water and anhydrous ethanol three times, dried, and ground through a 100-mesh sieve to obtain biochar.

[0093] Example 1

[0094] A process for treating domestic sewage in villages and towns comprises the following steps:

[0095] S1. The domestic sewage from villages and towns is concentrated and separated through a grid and then passed into a sedimentation tank. Basic aluminum chloride is added to the sedimentation tank. After stirring for 10 minutes, polyacrylamide is added. The amount of basic aluminum chloride used is 20g per ton of domestic sewage from villages and towns; the amount of polyacrylamide used is 10g per ton of domestic sewage from villages and towns. Stirring is continued for 20 minutes. The treated effluent is recorded as pretreated sewage.

[0096] S2. The pretreated sewage is passed into the anaerobic tank. The sewage in the anaerobic tank flows into the aerobic tank through overflow. Denitrifying bacteria are added to the anaerobic tank. The amount of denitrifying bacteria added is 2% 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 amount of nitrifying bacteria added to the aerobic tank is 1% of the mass of the sewage in the aerobic tank. The amount of modified biochar-loaded EM bacteria added is 1% of the mass of the sewage in the aerobic tank. Finally, it enters the purification tank through a water pipe. The effluent from the purification tank is the discharge water.

[0097] Modified biochar loaded with EM bacteria is prepared by the following steps:

[0098] The EM bacterial solution was diluted to 4 times with distilled water, and then the modified biochar prepared in Preparation Example 1 was added. The ratio of EM bacterial solution to modified biochar was controlled to be 10 mL:1.5 g. The mixture was shaken at 25°C and a speed of 160 r / min for 120 min, filtered, and dried to obtain modified biochar loaded with EM bacteria.

[0099] The EM bacterial liquid is obtained by activating and fermenting the EM bacterial strain dry powder. Specifically, the EM bacterial strain dry powder is inoculated on the EM culture medium, and then placed in a sealed plastic bottle, at 36±1°C, 200r / min, with air released once a day, and shaken cultured for 48 hours to obtain the activated EM bacterial liquid. The activated EM bacterial liquid and EM culture medium are mixed in a volume ratio of 1:18, at a constant temperature of 36°C, oscillated at 160r / min, with air released once a day, and shaken cultured for 72 hours to obtain the EM bacterial liquid.

[0100] The composition of EM bacterial culture medium is: 100g brown sugar, 1g urea, 1g NaCl, 1L distilled water, and the pH is adjusted to 7.0±0.2 after dissolution.

[0101] The hydraulic retention time of the anaerobic tank is 5 hours, and the hydraulic retention time of the aerobic tank is 6 hours. The aerobic tank is equipped with an aeration device, and the aeration time is 2 hours every 24 hours.

[0102] The purification pool has a two-layer structure, the upper layer is the adsorption layer, and the lower layer is the filler layer. The thickness of the adsorption layer is 40 cm, and the thickness of the filler layer is 15 cm. The adsorption layer contains activated carbon, expanded perlite and straw, and the filler layer contains clay red bricks and iron tailings.

[0103] The mass ratio of activated carbon, expanded perlite and straw is 1:1:6; the mass ratio of clay red brick and iron tailings is 3:1.

[0104] The particle sizes of activated carbon, expanded perlite and straw are independently 0.05-0.15 cm; the particle sizes of clay red brick and iron tailings are independently 0.8-2 cm.

[0105] Example 2

[0106] A process for treating domestic sewage in villages and towns comprises the following steps:

[0107] S1. The domestic sewage from villages and towns was separated by a grid and then passed into a sedimentation tank. Aluminum sulfate was added to the sedimentation tank. After stirring for 10 minutes, polyacrylamide was added. The amount of aluminum sulfate used was 25g per ton of domestic sewage from villages and towns; the amount of polyacrylamide used was 15g per ton of domestic sewage from villages and towns. Stirring was continued for 25 minutes. The treated effluent was recorded as pretreated sewage.

[0108] S2. The pretreated sewage is passed into the anaerobic tank. The sewage in the anaerobic tank enters the aerobic tank through overflow. Denitrifying bacteria are added to the anaerobic tank. The amount of denitrifying bacteria added 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 amount of nitrifying bacteria added to the aerobic tank is 2% of the mass of the sewage in the aerobic tank. The amount of modified biochar-loaded EM bacteria added is 1.5% of the mass of the sewage in the aerobic tank. Finally, the sewage enters the purification tank through a water pipe. The effluent from the purification tank is the discharge water.

[0109] Modified biochar loaded with EM bacteria is prepared by the following steps:

[0110] The EM bacterial solution was diluted to 5 times with distilled water, and then the modified biochar prepared in Preparation Example 1 was added. The ratio of EM bacterial solution to modified biochar was controlled to be 10 mL:2 g. The temperature was 25°C and the rotation speed was 160 r / min for 140 min. The mixture was filtered and dried to obtain modified biochar loaded with EM bacteria.

[0111] The preparation process of EM bacterial solution is the same as that in Example 1.

[0112] The hydraulic retention time of the anaerobic tank is 6 hours, and the hydraulic retention time of the aerobic tank is 7 hours. The aerobic tank is equipped with an aeration device, and the aeration time is 3 hours every 24 hours.

[0113] The purification pool has a two-layer structure, the upper layer is the adsorption layer, and the lower layer is the filler layer. The thickness of the adsorption layer is 50 cm, and the thickness of the filler layer is 20 cm. The adsorption layer contains activated carbon, expanded perlite and straw, and the filler layer contains clay red bricks and iron tailings.

[0114] The mass ratio of activated carbon, expanded perlite and straw is 8:10:31; the mass ratio of clay red brick and iron tailings is 5:1.

[0115] The particle sizes of activated carbon, expanded perlite and straw are independently 0.05-0.15 cm; the particle sizes of clay red brick and iron tailings are independently 0.8-2 cm.

[0116] Example 3

[0117] A process for treating domestic sewage in villages and towns comprises the following steps:

[0118] S1. The domestic sewage from villages and towns is concentrated and separated through a grid and then passed into a sedimentation tank. Basic aluminum chloride is added to the sedimentation tank. After stirring for 10 minutes, polyacrylamide is added. The amount of basic aluminum chloride used is 30g per ton of domestic sewage from villages and towns; the amount of polyacrylamide used is 20g per ton of domestic sewage from villages and towns. Stirring is continued for 30 minutes. The treated effluent is recorded as pretreated sewage.

[0119] S2. The pretreated sewage is passed into the anaerobic tank. The sewage in the anaerobic tank enters the aerobic tank through overflow. Denitrifying bacteria are added to the anaerobic tank. The amount of denitrifying bacteria added is 5% 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 amount of nitrifying bacteria added to the aerobic tank is 3% of the mass of the sewage in the aerobic tank. The amount of modified biochar-loaded EM bacteria added is 2% of the mass of the sewage in the aerobic tank. Finally, the sewage enters the purification tank through a water pipe. The effluent from the purification tank is the discharge water.

[0120] Modified biochar loaded with EM bacteria is prepared by the following steps:

[0121] The EM bacterial solution was diluted to 5 times with distilled water, and then the modified biochar prepared in Preparation Example 1 was added. The ratio of EM bacterial solution to modified biochar was controlled to be 10 mL:2.5 g. The mixture was shaken at 25°C and a speed of 160 r / min for 150 min. The mixture was filtered and dried to obtain modified biochar loaded with EM bacteria.

[0122] The preparation process of EM bacterial solution was the same as that in Example 1.

[0123] The hydraulic retention time of the anaerobic tank is 7 hours, and the hydraulic retention time of the aerobic tank is 8 hours. The aerobic tank is equipped with an aeration device, and the aeration time is 2 hours every 24 hours.

[0124] The purification pool has a two-layer structure, the upper layer is the adsorption layer, and the lower layer is the filler layer. The thickness of the adsorption layer is 60 cm, and the thickness of the filler layer is 25 cm. The adsorption layer contains activated carbon, expanded perlite and straw, and the filler layer contains clay red bricks and iron tailings.

[0125] The mass ratio of activated carbon, expanded perlite and straw is 10:10:40; the mass ratio of clay red brick and iron tailings is 5:3.

[0126] The particle sizes of activated carbon, expanded perlite and straw are independently 0.05-0.15 cm; the particle sizes of clay red brick and iron tailings are independently 0.8-2 cm.

[0127] Example 4

[0128] A process for treating domestic sewage in villages and towns, compared with Example 1, the difference is that the modified biochar in Example 1 is replaced by the product obtained in Preparation Example 2 of equal mass.

[0129] Example 5

[0130] A process for treating domestic sewage in villages and towns, compared with Example 1, the difference is that the modified biochar in Example 1 is replaced by the product obtained in Preparation Example 3 of equal mass.

[0131] Example 6

[0132] A process for treating domestic sewage in villages and towns is different from Example 1 in that the ratio of the EM bacterial solution to the modified biochar in this embodiment is controlled to be 10 mL:2 g.

[0133] Example 7

[0134] A process for treating domestic sewage in villages and towns, compared with Example 1, differs in that the usage ratio of EM bacterial liquid and modified biochar in this embodiment is controlled to be 10 mL:2.5 g.

[0135] Example 8

[0136] A process for treating domestic sewage in villages and towns, compared with Example 1, differs in that the amount of nitrifying bacteria added to the aerobic tank in Example 1 is 3% of the mass of the sewage in the aerobic tank, the amount of modified biochar-loaded EM bacteria added is 2% of the mass of the sewage in the aerobic tank, and the preparation process of modified biochar-loaded EM bacteria is the same as that of Example 1.

[0137] Comparative Example 1

[0138] A process for treating domestic sewage in villages and towns, compared with Example 1, the difference is that the modified biochar in Example 1 is replaced by the product obtained in Control Example 1 of equal quality.

[0139] Comparative Example 2

[0140] A process for treating domestic sewage in villages and towns, compared with Example 1, the difference is that the modified biochar in Example 1 is replaced by the product obtained in Control Example 2 of equal quality.

[0141] Comparative Example 3

[0142] A process for treating domestic sewage in villages and towns, compared with Example 1, differs in that the modified biochar in Example 1 is replaced by a substance of equal mass in Control Example 3.

[0143] Comparative Example 4

[0144] A process for treating domestic sewage in villages and towns, compared with Example 1, differs in that the modified biochar in Example 1 is replaced by a substance of equal mass in Control Example 4.

[0145] Comparative Example 5

[0146] A process for treating domestic sewage in villages and towns is provided, which differs from Example 1 in that the modified biochar loaded with EM bacteria in Example 1 is replaced with an EM bacterial solution of equal mass, and the preparation process of the EM bacterial solution is the same as that in Example 1.

[0147] The treatment processes provided in Examples 1 to 8 and Comparative Examples 1 to 5 were used to treat domestic sewage generated in a town in Anhui Province. The water quality of the domestic sewage was as follows: COD content was 865 mg / L, TN content was 214.6 mg / L, and TP content was 24.5 mg / L. After the treatment, the effluent from the purification tank was tested, and the results are shown in Table 1:

[0148] Table 1

[0149]

[0150] It can be seen from the test results in Table 1 that the COD content of the effluent obtained by the treatment processes of Examples 1 to 8 is ≤16.2 mg / L, TN content is ≤5.14 mg / L, and TP content is ≤0.08 mg / L, and the effluent quality is significantly better than that of Comparative Examples 1 to 5.

[0151] Specifically, it can be seen from the test results of Example 1 and Comparative Example 1 and Comparative Example 2 that the effluent quality of Example 1 is significantly better than that of Comparative Example 1 and Comparative Example 2, indicating that when sodium alginate or phosphatidylserine is used alone as a modifier in the preparation of modified biochar, the obtained modified biochar loaded with EM bacteria has a poor purification effect on sewage. However, the present invention uses sodium alginate and phosphatidylserine as modifiers, and there is a synergistic effect between the two. The prepared modified biochar loaded with EM bacteria has a better purification effect on sewage.

[0152] 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 the EM bacterial agent, the obtained modified biochar loaded with EM bacteria has a poor sewage purification effect.

[0153] It can be seen from the test results in Example 1 and Comparative Examples 4 and 5 that the effluent quality in Example 1 is higher than that using biochar as a carrier of the EM bacterial agent or directly adding the EM bacterial agent to the aerobic tank. The reason is that the modified biochar in Example 1 is a magnetic biochar carrying sodium alginate and phosphatidylserine on the surface, and the weak magnetic field generated by it can promote the aggregation of paramagnetic oxygen near the modified biochar-loaded EM bacteria, thereby increasing the contact degree between EM bacteria and oxygen, and helping to accelerate the reproduction and metabolism of EM bacteria. The magnetic effect has a good stimulating effect on EM bacteria, which can catalyze the enzyme activity of EM bacteria, thereby improving the purification effect of EM bacteria on sewage. In addition, the phosphatidylserine carried by the modified biochar can provide certain nutrients (N and P nutrients) for EM bacteria, which is beneficial to improving the biological activity of EM bacteria. On the other hand, it combines with organic pollutants in sewage through hydrogen bonding or hydrophobic interactions, which is beneficial to promoting the rapid degradation of pollutants by EM bacteria.

[0154] It should be noted that, in this document, relational terms such as first and second, etc., are used only 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 terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0155] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the 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. Collect the domestic sewage from villages and towns and separate it through a grid before passing 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. The pretreated wastewater is passed into the anaerobic tank. The wastewater in the anaerobic tank flows into the aerobic tank through overflow. Nitrifying bacteria and modified biochar-loaded EM bacteria are added to the aerobic tank. Finally, the wastewater flows into the purification tank through a water pipe. The effluent from the purification tank is the discharge water. The raw materials for preparing the modified biochar include sodium alginate, magnetic biochar, phosphatidylserine and glutaraldehyde; The modified biochar is prepared by the following steps: Sodium alginate and phosphatidylserine were added to deionized water, stirred evenly, and then magnetic biochar was added. The temperature was raised to 50° C., stirred for 10 minutes, and then glutaraldehyde was added. The stirring was continued for 1.5-2.5 hours, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain modified biochar.

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 EM bacteria.

3. A process for treating domestic sewage in villages and towns according to claim 2, characterized in that: The usage 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 usage 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.

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

7. A process for treating domestic sewage in villages and towns according to claim 6, characterized in that: The usage ratio of cobalt sulfate, nickel sulfate, ferric 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.

8. 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.

9. 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.

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