Method for recycling and utilizing rural domestic sewage

Abstract

The present application relates to the technical field of sewage treatment, in particular to a method for recycling and utilizing rural domestic sewage. Based on rural domestic sewage, the method effectively reduces the concentration of organic matter and the content of nitrogen and phosphorus in the domestic sewage after anaerobic-aerobic treatment. The aerobic effluent still contains sufficient nitrogen, which can be directly used for irrigation after precipitation. The sludge obtained from the sedimentation tank contains rich phosphorus, which can be extracted by carbonization and acid leaching of the sludge, and used for supplementing phosphorus for crops. When the effluent from the sedimentation tank needs to be discharged, it is further treated by artificial wetland, and the carbonization residue of the sludge is made into filler for the artificial wetland, which has good water purification effect, realizes the treatment and recycling of water resources, and has important significance for environmental protection and resource conservation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for the resource recycling of rural domestic wastewater. Background Technology

[0002] Wastewater is generated in people's daily lives. Rural domestic wastewater is characterized by generally high levels of organic matter, nitrogen and phosphorus, generally low levels of heavy metals, and unstable water volume. If it is not effectively treated, it will cause serious environmental pollution and will also hinder the recycling of water resources and the conservation of resources.

[0003] Currently, biological treatment methods are widely used to treat domestic sewage, with A being the most common. 2 The O process, or anaerobic-anoxic-aerobic wastewater treatment process, involves denitrification, which consumes carbon sources and converts nitrogen into nitrogen gas for emission, resulting in resource loss. In addition, the process is relatively complex, making it difficult to operate and manage, and it generates a large amount of sludge, which increases subsequent treatment costs.

[0004] Therefore, a wastewater treatment method with a simpler process that can fully recover usable resources from domestic sewage is a technical problem that needs to be solved in the current treatment of domestic sewage in rural towns. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the resource recycling of rural domestic sewage, in order to solve the problems of excessive sludge production and easy resource loss caused by traditional methods.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for the resource recycling of rural domestic sewage, comprising the following steps:

[0007] S1. Domestic sewage is sequentially fed into an anaerobic reactor and an aerobic reactor for anaerobic and aerobic treatment.

[0008] By controlling the sludge discharge from the aerobic reactor, the nitrification reaction in the aerobic reactor mainly remains at the nitrification stage. Part of the effluent from the aerobic reactor is returned to the front end of the anaerobic reactor, and the other part of the effluent from the aerobic reactor goes to the sedimentation tank.

[0009] S2. Use part of the effluent from the sedimentation tank directly for irrigation, and send part to an artificial wetland to treat the sludge from the sedimentation tank.

[0010] After anaerobic fermentation, the sludge from the sedimentation tank is transferred to the conditioning tank. A mixture of sludge carbonization residue, acid leaching residue and iron powder, as well as clear lime water, are added to the conditioning tank in sequence. After coagulation, flocculation, dewatering and drying, dried sludge is obtained.

[0011] S3. The dried sludge, biomass straw and calcium carbonate powder are compounded and granulated. The resulting sludge-biomass particles are carbonized to obtain carbonized slag. The carbonized slag is crushed, acid-leached and dried to obtain the sludge carbonized slag acid leaching residue in S2. The phosphorus resources in the acid leaching solution of the sludge carbonized slag are recovered.

[0012] S4. Take the carbonized residue and acid leaching residue of S3 sludge, mix it with iron powder, pore-forming agent and binder, granulate and calcinate it to obtain ceramsite filler, and use the obtained ceramsite filler in S2 artificial wetland.

[0013] Furthermore, in S1, the reflux ratio of the aerobic reactor effluent is 50-150%, and the concentration ratio of ammonia nitrogen to nitrate nitrogen in the anaerobic reactor is controlled at 3-5:1. By controlling the sludge discharge from the aerobic reactor, the sludge age in the aerobic reactor is kept at 4-8 days, the dissolved oxygen concentration in the aerobic reactor is controlled at 2-4 mg / L, the temperature in the aerobic reactor is controlled at 25-30℃, and the pH in the aerobic reactor is controlled at 7.5-8.0.

[0014] Furthermore, in S3, the moisture content of the dried sludge is 10-20%. The dried sludge and biomass straw are crushed and granulated. The particle size of the crushed dried sludge is 1-5 mm, the particle size of the crushed biomass straw is 3-8 mm, and the particle size of the calcium carbonate powder is 500-1000 mesh. The mass ratio of dried sludge, biomass straw, and calcium carbonate powder is 100:100-300:1-5.

[0015] Furthermore, the carbonization temperature is 800–1000℃, and the carbonization time is 4–8 hours; the combustible gas generated during the carbonization process is used to provide the heat required for carbonization; the obtained carbonized slag is cooled and then crushed, and the crushed carbonized slag is passed through a 200–400 mesh sieve.

[0016] Furthermore, the acid leaching is performed using nitric acid, with a concentration of 2-5 mol / L and a volume-to-mass ratio of nitric acid to carbonized slag of 5-10:1. After acid leaching, solid-liquid separation, water washing, and drying are performed to obtain carbonized slag acid-leached residue. The pH of the acid leaching solution is adjusted to alkaline, and solid-liquid separation, water washing, and drying are performed to obtain composite phosphate.

[0017] Furthermore, in S2, the iron powder has a particle size of 200-400 mesh, the mass ratio of carbonization slag and acid leaching slag to iron powder is 1:1-3, and the dosage of the mixture of sludge carbonization slag, acid leaching slag, and iron powder is 1-5 g / m³. 3 Mud; stir thoroughly for 2-4 hours, adding clear lime water during the process, and controlling the pH in the conditioning tank to be 7-9.

[0018] Furthermore, after the sludge in the conditioning tank is fully stirred and reacted, coagulant PAC is added, and after being fully stirred and allowed to stand, the concentrated sludge is sent to the dewatering equipment for pressing and dewatering. Before dewatering, flocculant PAM is added, with the dosage of PAC being 20-50 ppm and the dosage of PAM being 1-10 ppm. After the sludge is dewatered, it is dried at low temperature.

[0019] Furthermore, in S4, the mass ratio of sludge carbonization residue, acid leaching residue, iron powder, pore-forming agent, and binder is 10:10-30:0.1-0.5:20-50, the pore-forming agent is perlite powder with a particle size of 200-400 mesh, the binder is 20wt.% sodium silicate solution, and the diameter of the granulated pellets is 10±2mm.

[0020] Furthermore, the granulated pellets are dried and then sintered under a protective atmosphere, including nitrogen, at a temperature of 1000–1200°C for 10–30 minutes. After sintering and cooling, the ceramsite filler is obtained.

[0021] Furthermore, the constructed wetland includes interconnected horizontal subsurface flow constructed wetlands and ecological ponds. In the horizontal subsurface flow constructed wetlands, gravel and expanded clay aggregate are arranged sequentially from bottom to top, and wetland plants are rooted in the expanded clay aggregate. The wetland plants include yellow iris and reeds. Gravel is arranged at the bottom of the ecological pond, and the ecological pond plants include willow, reeds, and irises.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention is based on the traditional AO process, namely the anaerobic-aerobic process, to avoid nitrogen loss caused by denitrification; and through process control, the nitrification reaction in the aerobic reactor is mainly controlled at the nitrification stage, thereby effectively reducing sludge production, reducing the load on downstream treatment and treatment costs, and facilitating resource recovery and cost savings.

[0024] 2. This invention combines anaerobic processes to achieve anaerobic phosphorus release and aerobic phosphorus uptake, transferring most of the phosphorus to the sludge. By recirculating the effluent from the aerobic reactor, the nitrite in the aerobic reactor is returned to the anaerobic reactor. In the anaerobic reactor, partial denitrification is achieved through anaerobic ammonia oxidation. By controlling the process parameters, severe eutrophication of the effluent from the aerobic reactor is avoided, facilitating downstream irrigation and artificial wetland treatment. At the same time, the free ammonia nitrogen in the aerobic reactor also promotes the enrichment of nitrite nitrogen.

[0025] 3. This invention treats sludge, avoiding the cost of transporting sludge off-site and realizing the recovery of phosphorus resources. By compounding sludge with biomass straw, it can synergistically treat biomass straw on the one hand, and realize the recovery of phosphorus resources through carbonization and acid leaching on the other hand. The combustible gas generated during carbonization can be used for sludge drying, which helps to reduce energy consumption.

[0026] 4. This invention comprehensively utilizes sludge carbonization residue and acid leaching residue. On the one hand, it is used in sludge conditioning tanks. Through process control, it can effectively improve the sludge dewatering performance, help reduce energy consumption, and play a positive role in inhibiting equipment scaling. On the other hand, it is also made into packing material and used in constructed wetlands. While realizing the comprehensive utilization of carbonization residue, it can also effectively ensure the effluent quality of constructed wetlands. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

[0028] The principle of this invention is as follows:

[0029] This invention is based on rural domestic sewage, which is characterized by high organic matter, nitrogen and phosphorus content, unstable water volume, and low heavy metal content. It proposes a process that is simple, realizes water resource recycling and can effectively recover resources, is easy to manage, and has low overall energy consumption. It fits the current situation in rural areas and develops a new approach for rural sewage treatment.

[0030] In this invention, an anaerobic-aerobic wastewater treatment process is employed. Village and town wastewater is collected and sent to an anaerobic reactor. During this process, other wastewater generated in the treatment, such as sludge dewatering liquid and wastewater from phosphorus recovery treatment, can be collected. In the anaerobic reactor, organic matter in the wastewater undergoes hydrolysis, acidification, and ammonification reactions, generating small-molecule organic acids. Simultaneously, polyphosphate-accumulating bacteria multiply under anaerobic conditions, synthesizing intracellular PHB and releasing phosphorus. Then, in the aerobic reactor, ammonia nitrogen in the wastewater undergoes nitrification. In this invention, process control, such as sludge age, pH, absence of added carbon source, dissolved oxygen, temperature, and reflux ratio control, is implemented. The process, including the control of nitrogen production, ensures that the nitrification reaction mainly focuses on nitrite nitrogen, without further conversion to nitrate nitrogen. This effectively reduces sludge production. Furthermore, the generated nitrate nitrogen is recycled to the anaerobic reactor, where it undergoes anaerobic ammonia oxidation with ammonia nitrogen, removing some nitrogen and thus reducing the nitrogen content in the effluent. This prevents excessive eutrophication caused by high nitrogen levels, which would hinder irrigation and subsequent artificial treatment. In the aerobic reactor, polyphosphate-accumulating bacteria consume intracellular PHB and excessively absorb phosphorus, transferring most of the phosphorus to the sludge and discharging it into the sedimentation tank.

[0031] The effluent from the sedimentation tank can be used directly for irrigation, while another portion can be sent to an artificial wetland for further treatment, with allocation based on actual water volume and demand. The sludge from the sedimentation tank requires further treatment. First, after anaerobic fermentation to reduce its volume, the sludge is sent to a conditioning tank. A mixture of sludge carbonization residue, acid leaching residue powder, and iron powder is added to the conditioning tank. After addition, the mixture is thoroughly stirred, and lime water is added. This allows the calcium hydroxide in the clarified lime water to react with the carbon dioxide in the fermentation broth, producing calcium carbonate as a byproduct of the sludge carbonization residue and acid leaching residue treatment. The sludge grows with the powder core as its core. When the pH in the conditioning tank no longer decreases, coagulant PAC is added, stirred evenly, and allowed to stand. The lower layer of concentrated sludge is then taken to the dewatering equipment. Flocculant PAM is added at the front end of the dewatering equipment, and then dewatering is carried out in the dewatering equipment. The particles formed above with the sludge carbonization residue and acid leaching residue powder as their core help the sludge dewatering. At the same time, the iron-carbon micro-electrolysis environment also helps the sludge to be further dewatered, thereby improving the dewatering efficiency and reducing energy consumption. The dewatered sludge is then sent to a low-temperature sludge dryer for drying to obtain dried sludge.

[0032] The dried sludge is crushed and mixed with crushed biomass straw and calcium carbonate to form granules. The resulting granulated raw material is then carbonized in a carbonization device. During the process, calcium carbonate decomposes at high temperature, which plays a role in creating pores, loosening the sludge, fixing sulfur, and increasing the calorific value of combustible gas. The resulting combustible gas can be returned to the sludge drying section to provide energy for sludge drying, while the resulting carbonized sludge residue can be further utilized.

[0033] In this invention, the carbonized sludge residue is first acid-leached. Nitric acid leaching can extract soluble phosphates from the carbonized sludge residue. Then, the pH is adjusted to allow the phosphates to precipitate and separate. Subsequently, solid-liquid separation, washing, and drying are performed to obtain composite phosphates, mainly calcium phosphates. The obtained composite phosphates can be used to supplement phosphorus, calcium, iron, etc. in crops. The acid-leached residue of the carbonized sludge obtained from solid-liquid separation has a loose structure and its main component is carbon, which has a good adsorption effect. After mixing it with iron powder, it is added to the sludge conditioning tank. On the one hand, it can act as a core to adsorb calcium carbonate precipitate, forming tiny particles with the acid-leached residue of the carbonized sludge residue as the core. On the other hand, the micro-electrolysis of iron and carbon also helps to efficiently dewater the sludge.

[0034] Simultaneously, sludge carbonization residue and acid leaching residue are used as fillers in constructed wetlands. In this invention, the constructed wetland adopts a horizontal subsurface flow constructed wetland combined with an ecological pond, which is more in line with the actual conditions of villages and towns. Gravel is first laid at the bottom of the horizontal subsurface flow constructed wetland and the ecological pond as a support. Then, the substrate of this invention is laid in the horizontal subsurface flow constructed wetland, which is ceramsite made by mixing sludge carbonization residue, acid leaching residue, iron powder, pore-forming agent and binder and firing it at high temperature. The ceramsite is laid as a substrate in the constructed wetland. Then, plants of the horizontal subsurface flow constructed wetland and plants of the ecological pond are planted. The plants of the horizontal subsurface flow constructed wetland include yellow iris and reeds, which are rooted in the substrate. The plants of the ecological pond include reeds, irises and willows. Through the combination of horizontal subsurface flow constructed wetland and ecological pond, nitrogen and phosphorus in the sedimentation tank effluent are further removed, beautifying the environment while effectively ensuring the quality of the effluent.

[0035] Example 1

[0036] The wastewater treatment facility in a certain village / town adopts the technical solution of this invention. The village / town has a permanent population of approximately 1000 people, and the designed wastewater treatment capacity is 200 m³. 3 / sky.

[0037] A collection pond was set up to collect domestic sewage from villages and towns. Multiple samples were taken from the collection pond for testing. The key water quality indicators of the collection pond are as follows: COD 400-500 mg / L, total nitrogen 70-90 mg / L, ammonia nitrogen 60-80 mg / L, total phosphorus 5-7 mg / L, and pH 6.5-7.5.

[0038] In this embodiment, the daily sewage treatment volume is approximately 100m³. 3 / day, the influent is collected from the wastewater generated in the downstream treatment, such as the supernatant during sludge thickening, the filter press liquid generated by the dewatering equipment, and the wastewater generated from the acid leaching and collection of compound phosphate, as well as the nitrification reaction liquid returned from the aerobic reactor, and is fed into the anaerobic reactor. In this embodiment, the concentration ratio of ammonia nitrogen to nitrite nitrogen in the anaerobic reactor is controlled at 4:1; the sludge age in the aerobic reactor is 6 days, DO is 3±0.5mg / L, the temperature is controlled at 28±2℃, and the pH value is controlled at 7.8±0.2.

[0039] The effluent from the aerobic reactor was monitored. The COD in the effluent was 70-90 mg / L, the total nitrogen was 30-40 mg / L, the ammonia nitrogen was 6-10 mg / L, the nitrite nitrogen was 15-20 mg / L, and the total phosphorus was 1-3 mg / L.

[0040] The effluent from the aerobic reactor is sent to a sedimentation tank for sedimentation. The supernatant from the sedimentation tank is used directly for irrigation and for sampling artificial wetlands for further treatment.

[0041] In this embodiment, the irrigation water volume is relatively small, and river water can be used for irrigation according to the actual situation. The sludge is conditioned using the carbonized sludge and acid leaching residue of the present invention, and the substrate made from the carbonized sludge and acid leaching residue is used for the artificial wetland. The effluent water quality of the artificial wetland ecological pond has COD of 20-30 mg / L, total nitrogen of 10-15 mg / L, ammonia nitrogen of 1-3 mg / L, and total phosphorus of 0.1-0.3 mg / L, which fully meets the requirements of relevant standards.

[0042] In this embodiment, the sludge generated from the sedimentation tank is treated to avoid environmental pollution and resource waste. The sludge from the sedimentation tank is first sent to an anaerobic digester for fermentation and volume reduction. The biogas produced can be used for subsequent sludge drying. After volume reduction, the anaerobic digester sends the sludge to a conditioning tank for conditioning. A mixed powder of sludge carbonization residue, acid leaching residue, and iron powder is added to the conditioning tank. The particle size of the sludge carbonization residue, acid leaching residue, and iron powder is controlled at 200-400 mesh, the mass ratio of carbonization residue, acid leaching residue, and iron powder is 1:2, and the dosage of the mixed powder is 3 g / m³. 3 After the sludge is added, it is stirred and mixed evenly. Then, under stirring conditions, clear lime water is slowly added to control the pH in the conditioning tank to fluctuate around 8. When the pH rises to more than 9, it indicates that the reaction is complete, and the addition of clear lime water is stopped.

[0043] At this point, PAC is added to the conditioning tank and stirred until well mixed. The PAC dosage is 30 ppm. After settling, the lower layer of concentrated sludge is taken and sent to the dewatering equipment. In this embodiment, the dewatering equipment is a plate and frame filter press. PAM is added to the concentrated sludge before it enters the plate and frame filter press. The PAM dosage is 3 ppm. After testing, the sludge moisture content after dewatering is about 55%. Then it goes to the drying section for low-temperature drying. The second drying uses a low-temperature drying equipment. The sludge is cut into strips and then enters the drying equipment for drying. The sludge moisture content is about 15%.

[0044] The dried sludge was crushed and then mixed with crushed biomass straw and calcium carbonate (800 mesh) to form granules. The particle size of the crushed sludge was controlled at about 3 mm, and the particle size of the crushed biomass straw was controlled at about 5 mm. The mass ratio of sludge, biomass straw and calcium carbonate was 100:200:3. The particle size of the resulting granules was 3-8 mm.

[0045] The granules prepared above are carbonized in a carbonization device. The carbonization temperature is controlled at 850℃ for 6 hours. The combustible gas produced by carbonization can be used to power carbonization and sludge drying. After carbonization, sludge carbonization residue is obtained. The sludge carbonization residue is crushed and passed through a 400-mesh sieve. Then, it is acid-leached with 4 mol / L nitric acid. The volume mass ratio (L / kg) of nitric acid to sludge carbonization residue is 8:1. After acid leaching, alkali is added to the system to adjust the pH to alkaline. After complete precipitation, solid and liquid are separated. The solid product is washed with water until neutral and dried to obtain composite phosphate, thus realizing the recovery of phosphorus resources.

[0046] The above-mentioned sludge carbonization residue and acid leaching residue are mixed with iron powder, pore-forming agent and binder and then granulated. In this embodiment, the pore-forming agent is perlite powder (400 mesh) and the binder is 20 wt.% sodium silicate solution. The mass ratio of sludge carbonization residue, acid leaching residue, iron powder, pore-forming agent and binder is 10:30:0.3:40, and small balls with a diameter of about 10 mm are formed. After drying the prepared small balls, they are calcined at 1150°C for 20 min under nitrogen protection. After calcination and cooling, the artificial wetland matrix filler of the present invention can be obtained.

[0047] Expanded ceramsite substrate is laid in the horizontal subsurface flow constructed wetland. In the horizontal subsurface flow constructed wetland, the gravel layer is 20cm thick and the expanded ceramsite substrate layer is 40cm thick. Yellow iris, reeds, etc. are planted. The water from the horizontal subsurface flow constructed wetland flows to an ecological pond. Reeds, irises, and willows are planted in the ecological pond.

[0048] This embodiment achieves the treatment of rural domestic sewage, the comprehensive disposal of the generated sludge, and the recycling of resources. It has low operating costs, with the overall operating cost reduced by about 35% compared to traditional processes.

[0049] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for the resource-based recycling of rural domestic sewage, characterized in that, Includes the following steps: S1. Domestic sewage is sequentially fed into an anaerobic reactor and an aerobic reactor for anaerobic and aerobic treatment. By controlling the sludge discharge from the aerobic reactor, the nitrification reaction in the aerobic reactor mainly remains at the nitrification stage. Part of the effluent from the aerobic reactor is returned to the front end of the anaerobic reactor, and the other part of the effluent from the aerobic reactor goes to the sedimentation tank. S2. Use part of the effluent from the sedimentation tank directly for irrigation, and send part to an artificial wetland to treat the sludge from the sedimentation tank. After anaerobic fermentation, the sludge from the sedimentation tank is transferred to the conditioning tank. A mixture of sludge carbonization residue, acid leaching residue and iron powder, as well as clear lime water, are added to the conditioning tank in sequence. After coagulation, flocculation, dewatering and drying, dried sludge is obtained. S3. The dried sludge, biomass straw and calcium carbonate powder are compounded and granulated. The resulting sludge-biomass particles are carbonized to obtain carbonized slag. The carbonized slag is crushed, acid-leached and dried to obtain the sludge carbonized slag acid leaching residue in S2. The phosphorus resources in the acid leaching solution of the sludge carbonized slag are recovered. S4. Take the carbonized residue and acid leaching residue of S3 sludge, mix it with iron powder, pore-forming agent and binder, granulate and calcinate it to obtain ceramsite filler, and use the obtained ceramsite filler in S2 artificial wetland.

2. The method for resource recycling of rural domestic sewage according to claim 1, characterized in that: In S1, the reflux ratio of the aerobic reactor effluent is 50-150%, and the concentration ratio of ammonia nitrogen to nitrate nitrogen in the anaerobic reactor is controlled at 3-5:

1. By controlling the sludge discharge from the aerobic reactor, the sludge age in the aerobic reactor is kept at 4-8 days, the dissolved oxygen concentration in the aerobic reactor is controlled at 2-4 mg / L, the temperature in the aerobic reactor is controlled at 25-30℃, and the pH in the aerobic reactor is controlled at 7.5-8.

0.

3. The method for resource recycling of rural domestic sewage according to claim 1, characterized in that: In step S3, the moisture content of the dried sludge is 10-20%. The dried sludge and biomass straw are crushed and then granulated. The particle size of the crushed dried sludge is 1-5 mm, the particle size of the crushed biomass straw is 3-8 mm, and the particle size of the calcium carbonate powder is 500-1000 mesh. The mass ratio of dried sludge, biomass straw, and calcium carbonate powder is 100:100-300:1-5.

4. The method for resource recycling of rural domestic sewage according to claim 3, characterized in that: The carbonization temperature is 800~1000℃ and the carbonization time is 4~8h; the combustible gas generated during the carbonization process is used to provide the heat required for carbonization; the obtained carbonized slag is cooled and then crushed, and the crushed carbonized slag is passed through a 200~400 mesh sieve.

5. A method for the resource-based recycling of rural domestic sewage according to claim 4, characterized in that: The acid leaching process uses nitric acid with a concentration of 2-5 mol / L and a volume-to-mass ratio of nitric acid to carbonized slag of 5-10:

1. After acid leaching, solid-liquid separation, water washing, and drying are performed to obtain carbonized slag acid-leached residue. The pH of the acid leaching solution is adjusted to alkaline, and solid-liquid separation, water washing, and drying are performed to obtain composite phosphate.

6. A method for the resource-based recycling of rural domestic sewage according to claim 5, characterized in that: In S2, the iron powder has a particle size of 200-400 mesh, the mass ratio of carbonization slag and acid leaching slag to iron powder is 1:1-3, and the dosage of the mixture of sludge carbonization slag, acid leaching slag, and iron powder is 1-5 g / m³. 3 Mud; stir thoroughly for 2-4 hours, adding clear lime water during the process to control the pH in the conditioning tank to 7-9.

7. A method for the resource-based recycling of rural domestic sewage according to claim 6, characterized in that: After the sludge in the conditioning tank is fully stirred and reacted, coagulant PAC is added. After being fully stirred and allowed to stand, the concentrated sludge is sent to the dewatering equipment for pressing and dewatering. Before dewatering, flocculant PAM is added. The dosage of PAC is 20~50ppm and the dosage of PAM is 1~10ppm. After the sludge is dewatered, it is dried at low temperature.

8. A method for the resource-based recycling of rural domestic sewage according to claim 5, characterized in that: In S4, the mass ratio of sludge carbonization residue, acid leaching residue, iron powder, pore-forming agent, and binder is 10:10~30:0.1~0.5:20~50, the pore-forming agent is perlite powder with a particle size of 200~400 mesh, the binder is 20wt.% sodium silicate solution, and the diameter of the granulated pellets is 10±2mm.

9. A method for the resource-based recycling of rural domestic sewage according to claim 8, characterized in that: After granulation, the pellets are dried and then fired in a protective atmosphere, including nitrogen, at a temperature of 1000-1200℃ for 10-30 minutes. After firing and cooling, the ceramsite filler is obtained.

10. A method for the resource-based recycling of rural domestic sewage according to claim 9, characterized in that: The constructed wetland includes interconnected horizontal subsurface flow constructed wetlands and ecological ponds. In the horizontal subsurface flow constructed wetlands, gravel and expanded clay aggregate are arranged sequentially from bottom to top, and wetland plants are rooted in the expanded clay aggregate. The wetland plants include yellow iris and / or reeds. Gravel is arranged at the bottom of the ecological pond, and the ecological pond plants include willow, reeds and / or irises.