CN110550833A - System and method for recycling carbon, nitrogen, phosphorus and water in sewage - Google Patents

Abstract

The invention discloses a system and method for recycling carbon, nitrogen, phosphorus and water in sewage. The system includes a sump, a grit chamber, a first reactor, a second reactor, a raw material liquid storage device, and a drawing liquid The reservoir, the permeable membrane module and the sedimentation tank, wherein the sump is connected with the sewage pipe network, the sump is connected with the grit chamber through the pipeline, and the grit chamber is also connected with the first reactor through the pipeline, and the first reaction The container is respectively connected with the raw material liquid storage and the second reactor through the pipeline, and the second reactor is also connected with the sedimentation tank through the pipeline. The method is as follows: step 1, the sewage enters the grit chamber through the lifting pump; step 2 1. Anaerobic digestion produces methane; step 3, nitrogen and phosphorus resources are continuously concentrated and then enter the sedimentation tank; step 4, realize the recovery of carbon resources; step 5, return the supernatant to the raw material liquid storage for reprocessing. Beneficial effects: the complete recovery of water, carbon, nitrogen and phosphorus resources is realized; and the method has broad application prospects.

Description

A system and method for recycling carbon, nitrogen, phosphorus and water in sewage

technical field

The invention relates to a system and method for recovering carbon, nitrogen, phosphorus and water, in particular to a system and method for recovering carbon, nitrogen, phosphorus and water in sewage.

Background technique

At present, water is an important resource produced by sewage treatment plants, and it is also the most abundant resource, which can be used for various reuse purposes after proper treatment. At present, the disinfection process is usually used to ensure the biological safety of the effluent water quality. On the basis of the commonly used chlorine disinfection, ultraviolet disinfection is widely used in practice due to its high efficiency, safety, and economic advantages. In recent years, in addition to traditional organic matter, nitrogen and phosphorus pollutants, new trace organic pollutants have appeared in urban sewage, such as endocrine disruptors (EDCs), pharmaceuticals and personal care products (PPCPs), etc. Due to their potential Risk, the removal of these substances should also be considered in the process of reclaimed water treatment. Membrane technology is favored in water recycling due to its high efficiency, stability, and safety.

Each cubic meter of urban sewage contains about 0.5kg of COD, and the annual loss of carbon resources with urban sewage discharge reaches 20 million tons, which is estimated to be about 9.3 times the energy consumed for sewage treatment; 0.35m ³ methane is produced per kilogram of COD removed 1. If the recovery rate of methane is 80%, 6 billion m ³ of methane can be produced; if the residual organic matter after anaerobic digestion is 20%, 4 million tons of organic fertilizer can be produced. It can be seen that the recovery of carbon resources from sewage has a very large potential. The most common and widely used carbon recovery technology is anaerobic digestion. At present, the remaining sludge in the primary sedimentation tank and the secondary sedimentation tank is anaerobically digested, and the organic matter in the sludge is converted into methane, which is further converted into electricity through a biogas generator to supplement the electricity consumption of the sewage treatment plant. However, there are non-biomass components remaining in the sludge during the digestion process, and only about half of the sludge can be converted. Therefore, only about 20% of the organic matter in the sludge is converted into energy for reuse.

Phosphorus is a non-renewable and irreplaceable strategic resource, which is depleted. Inorganic nitrogen in typical urban sewage mainly exists in the form of ammonia nitrogen (free ammonia NH ₃ and ionic ammonium salt NH ₄ ⁺ ), and inorganic phosphorus mainly exists in the form of phosphate (PO ₄ ^3- , HPO ₄ ^2- , H ₂ PO ₄ ^- )exist. The recovery methods of ammonia nitrogen mainly include chemical precipitation (struvite) method, adsorption method, ion exchange method and membrane separation (reverse osmosis, electrodialysis, etc.) method. The chemical precipitation method requires additional addition of phosphorus and magnesium; the adsorption or ion exchange method has low investment and low energy consumption, but requires frequent regeneration; reverse osmosis, electrodialysis, etc. have high energy consumption. There are many techniques for recovering phosphorus resources, mainly chemical precipitation, enhanced biological phosphorus removal, and adsorption. The enhanced biological phosphorus removal method requires secondary treatment; the adsorption method has the advantages of simple process and reliable operation, but additional desorption is required to recover the phosphorus resources in the adsorbent.

Contents of the invention

The main purpose of the present invention is to provide a system and method for recycling carbon, nitrogen, phosphorus and water in sewage in order to realize efficient recovery of resources such as water, carbon, nitrogen and phosphorus in urban sewage.

The system for recovering carbon, nitrogen, phosphorus and water in sewage provided by the present invention includes a sump, a grit chamber, a first reactor, a second reactor, a raw material liquid storage, a draw liquid storage, and a permeable membrane assembly And the sedimentation tank, wherein the sump is connected with the sewage pipe network, the sump is connected with the grit chamber through the pipeline, the grit chamber is also connected with the first reactor through the pipeline, and the first reactor is respectively connected with the The raw material storage is connected with the second reactor, the second reactor is also connected with the sedimentation tank through the pipeline, the raw material storage is also connected with the sedimentation tank through the pipeline, the raw material storage and the draw liquid storage are connected through The two pipelines are connected, and the permeable membrane assembly is assembled on the two connecting pipelines of the raw material storage and the drawing storage.

There is a grid in the sump to intercept the suspended matter and floating matter in the sewage. The connecting pipeline between the sump and the grit chamber is equipped with a lift pump to pump the sewage in the sump into the grit chamber. The grit chamber and the grit chamber The connecting pipeline of the first reactor is equipped with a first peristaltic pump, and the grit chamber is an aerated grit chamber.

The first reactor is a high-load membrane bioreactor. The first reactor is equipped with ultrafiltration membrane modules and aeration stones. The effective area of the ultrafiltration membrane in the ultrafiltration membrane module is 0.1m ² , and the size of the membrane is length × width × height = 320 × 220 × 5mm ³ , the membrane pore size is 0.1 μm, a second peristaltic pump is installed on the connecting pipeline between the first reactor and the second reactor, and the The connecting pipeline is equipped with a third peristaltic pump, and the second reactor is also provided with a connecting pipe connected to the connecting pipeline between the first reactor and the raw material liquid storage, and the connecting pipe is equipped with a fourth peristaltic pump , the connecting pipeline between the second reactor and the sedimentation tank is equipped with a fifth peristaltic pump.

The raw material liquid storage is equipped with a conductivity meter and a PH value tester, a sixth peristaltic pump is installed on the connecting pipeline between the raw material liquid storage and the sedimentation tank, and a seventh peristaltic pump is installed on the connecting pipeline between the raw material liquid storage and the permeable membrane module. Peristaltic pump, the eighth peristaltic pump is installed on the connection pipeline between the osmotic membrane module and the draw liquid storage, the osmotic membrane module is composed of forward osmosis membrane, the effective area of the forward osmosis membrane is 30cm ² , and the flow channel depth is 2mm.

The sedimentation tank is equipped with a stirrer and a pH value tester.

The lift pump mentioned above, the first peristaltic pump, the second peristaltic pump, the third peristaltic pump, the fourth peristaltic pump, the fifth peristaltic pump, the conductivity meter, the pH value tester, the sixth peristaltic pump, the seventh peristaltic pump, the Eight peristaltic pumps and agitators are assembled from existing equipment, so the specific models and specifications are not repeated.

The method provided by the invention for reclaiming carbon, nitrogen, phosphorus and water in sewage, its method is as follows:

Step 1. The urban sewage enters the sump through the sewage pipe network, and the sewage entering the sump passes through the grid to intercept most of the suspended matter and floating matter, and then enters the grit chamber through the lift pump;

Step 2. The sewage entering the grit chamber is pumped into the first reactor for treatment. The first reactor is equipped with ultrafiltration membrane modules and aeration stones. After being filtered by the ultrafiltration membrane modules, the separated water is pumped into raw materials The liquid storage tank, the concentrated liquid treated by the first reactor is rich in separated organic matter and enters the second reactor through the pipeline for anaerobic digestion to produce methane;

Step 3. The water in the raw material liquid storage is used as the raw material liquid, and the high-salt solution of KCl, the main component of common agricultural fertilizer potassium fertilizer, is used as the drawing liquid in the drawing liquid storage. With the operation of the forward osmosis system, the high and low osmotic pressure is used Poor, so that the raw material liquid in the raw material liquid storage continuously enters the draw liquid storage through the osmotic membrane module, and the diluted draw liquid can be directly used for farmland irrigation, realizing the irrigation reuse of water resources, and the concentration in the raw material liquid storage After the nitrogen and phosphorus resources in the raw material liquid are continuously concentrated and enriched, they enter the sedimentation tank;

Step 4, the concentrated solution entering the sedimentation tank is adjusted to pH value, nitrogen, magnesium and phosphorus ratio conditions, and struvite precipitation is generated in the sedimentation tank, which is recycled as a slow-release fertilizer, and the supernatant in the sedimentation tank is pumped back to the Anaerobic digestion is carried out in the second reactor to realize the complete recovery of carbon resources;

Step 5: After anaerobic digestion in the second reactor produces methane, the remaining nitrogen and phosphorus resources can be continuously recovered, and the supernatant in the second reactor is returned to the raw material liquid storage for reuse.

The grit chamber in step 1 is an aerated grit chamber.

The ultrafiltration membrane used in the ultrafiltration membrane module in step 2 is a flat membrane, the effective area of a single membrane is 0.1m ² , the size of the membrane is length × width × height = 320 × 220 × 5mm ³ , the membrane pore size is 0.1 μm, the membrane The material is polyvinylidene fluoride, and the support plate is made of acrylonitrile-butadiene-styrene copolymer.

The forward osmosis membrane used in the osmotic membrane module in step 3 is an asymmetric membrane, consisting of an active layer and a support layer, wherein the material of the active layer is triacetate fiber, the material of the support layer is polyester, and the effective area of the forward osmosis membrane is 30cm ² , The runner depth is 2mm.

The struvite in step 4 is a slow-release fertilizer, containing Mg:N:P in a ratio of 1:1:1, and the pH value is controlled at 5-9.5, which is conducive to the formation of this compound fertilizer.

Working principle of the present invention:

Urban sewage enters the sump through the municipal pipe network. After the sewage passes through the grid to intercept most of the suspended solids and floating solids, it enters the grit chamber through the lift pump. The effluent water quality of the grit chamber: COD concentration is 270mg/L, TN concentration is 56.9mg/L, NH ₄ ⁺ -N concentration is 47.8mg/L, TP concentration is 4.9mg/L, PO ₄ ^3- -P concentration is 4.14 mg/L.

Then, the effluent from the grit chamber enters the first reactor through the first peristaltic pump, and the first reactor is provided with ultrafiltration membrane modules and aeration stones. The effective area of the ultrafiltration membrane module is 0.1m ² , the size of the membrane sheet is length×width×height=320×220×5mm ³ , and the membrane pore size is 0.1 μm. After the operation, the concentrated solution of 1/11.5 of the raw water volume is obtained, and the ultrafiltration membrane module of 10.5/11.5 is discharged. While achieving low-carbon recovery of suspended solids and colloidal organic matter in sewage, membrane effluent rich in nitrogen and phosphorus is obtained, and the concentrated solution in the first reactor enters the second reactor for anaerobic digestion to produce methane through the second peristaltic pump , to achieve energy recovery; the effluent from the ultrafiltration membrane module in the first reactor does not contain solid matter and pathogens and is rich in nitrogen and phosphorus elements, and enters the raw material liquid storage through the third peristaltic pump to recover nitrogen and phosphorus resources in sewage. During operation, control parameters such as aeration rate of 50L/h, temperature of 25°C and flux of 20LMH in the first reactor. The cleaning method of the ultrafiltration membrane in the ultrafiltration membrane module is simple and convenient. Gently scrape off the organic matter on the membrane, return to the concentrated solution, and then clean the membrane surface with a certain volume of pure water, and return the cleaning solution to the concentrated solution, and then Rinse the surface of the membrane with water to ensure that no obvious residual pollutants can be seen, and finally soak in sodium hypochlorite solution (available chlorine concentration 2000mg/L) for 2 hours, and then rinse the residual chemical agents on the surface of the membrane with water to restore 75% of the original state. The recovery rate of carbon resources can reach about 80%. The concentration of COD in the effluent of the ultrafiltration section is 42.89mg/L, the concentration of TN is 24.3mg/L, the concentration of NH ₄ ⁺ -N is 16.5mg/L, the concentration of TP is 6.43mg/L, and the concentration of PO ₄ ^3- -P is 6.4mg /L.

The effluent from the raw material storage is introduced into the osmotic membrane module through the seventh peristaltic pump. In the forward osmosis process of the osmotic membrane module, the feed water of the raw material liquid storage is used as the raw material liquid, and the high-salt solution of KCl, which is the main component of common agricultural fertilizer potassium fertilizer, is used as the drawing liquid in the drawing liquid storage. The raw material liquid and the drawing liquid are respectively Enter the osmotic membrane module through the seventh peristaltic pump and the eighth peristaltic pump, and then return to the raw material liquid storage and the draw liquid storage respectively, and the volume of the concentrated liquid is 1/10 of the raw material liquid. Utilizing the high and low osmotic pressure difference, the water in the feed liquid storage continuously passes through the osmotic membrane module and enters the draw liquid storage. The effective area of the forward osmosis membrane in the osmotic membrane module is 30cm ² (50mm×60mm), and the flow channel depth is 2mm . The diluted draw liquid in the draw liquid storage can be directly used for farmland irrigation to realize the recovery of water resources, and the water reuse rate is over 85%; the nitrogen and phosphorus resources in the concentrated raw material liquid in the raw material liquid storage are continuously concentrated Enrichment for subsequent struvite recovery. In the raw material liquid storage, a conductivity meter and a pH value tester are arranged. During the operation, control parameters such as cross-flow velocity of 15cm/s, temperature of 25°C, and concentration of draw solution of 2mol/L. After the forward osmosis membrane in the osmotic membrane module is completed, the membrane pollution is small and easy to clean. It only needs 15 minutes of physical cleaning (air-water ratio: 240L/h: 40L/h) to restore more than 75% of the membrane flux. The COD concentration of the concentrated liquid in the forward osmosis section is 220.88mg/L, the TN concentration is 123.93mg/L, the NH ₄ ⁺ -N concentration is 84.15mg/L, the TP concentration is 57.23mg/L, and the PO ₄ ^3- -P concentration is 56.96 mg/L.

The concentrated liquid in the raw material liquid storage enters the sedimentation tank through the sixth peristaltic pump for chemical precipitation of struvite. The sedimentation tank is equipped with a pH value tester and agitator. By adjusting the pH value to 5-9.5, the reaction time is 20min, n(NH ₄ ⁺ ):n(Mg ²⁺ ):n(PO ₃ ^4- ) is 4:1.2:1, the stirring speed is 200rpm, the precipitation time After collecting the supernatant, the precipitated part was dried at 40° C. for 48 hours. The nitrogen and phosphorus resources in the sewage are continuously concentrated and exist in the form of struvite precipitation. They can be recycled as slow-release fertilizers to realize the recovery of nitrogen and phosphorus resources. The nitrogen recovery rate is over 80%, and the phosphorus recovery rate is over 75%. The effective phosphorus content in the recovered phosphorus products is over 15%. The concentration of COD in the supernatant of the sedimentation tank is 220.88mg/L, the concentration of TN is 48.35mg/L, the concentration of NH ₄ ⁺ -N is 12.44mg/L, the concentration of TP is 10.31mg/L, and the concentration of PO ₄ ^3- -P is 10.2mg /L.

The supernatant of the sedimentation tank enters the second reactor for anaerobic digestion through the fifth peristaltic pump to produce methane. After anaerobic digestion of methane, the gas production capacity is collected to realize the recovery of carbon resources; the sediment can be directly treated as solid waste. Since the nitrogen and phosphorus resources in the concentrated solution of the ultrafiltration section and the supernatant of the struvite recovery section have not been fully recovered, the supernatant after anaerobic digestion of methane in the second reactor is returned to the raw material storage through the fourth peristaltic pump , continue to concentrate enrichment.

Beneficial effects of the present invention:

Compared with the prior art, the technical solution provided by the invention realizes the required sewage treatment effect under the conditions of simple flow, low energy consumption and less carbon emission. Realized the complete recovery of water, carbon, nitrogen and phosphorus resources: efficient recovery of water resources, water reuse rate of more than 85%; efficient recovery of carbon resources, methane recovery rate can reach 80%; efficient recovery of nitrogen, phosphorus resources, nitrogen The recovery rate is more than 80%, the phosphorus recovery rate is more than 75%, and the effective phosphorus content in the recovered phosphorus products is more than 15%. The forward osmosis membrane has little pollution and is easy to clean. After 15 minutes of physical cleaning, the membrane flux can recover 75% above; has broad application prospects.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of the recovery system of the present invention.

The annotations in the above figure are as follows:

1. Water collection tank 2, grit chamber 3, first reactor 4, second reactor 5, raw material liquid storage 6, draw liquid storage 7, osmotic membrane module 8, sedimentation tank 9, grid 10, lift pump 11. First peristaltic pump 12, ultrafiltration membrane module 13, aeration stone 14, second peristaltic pump 15, third peristaltic pump 16, connecting pipe 17, fourth peristaltic pump 18, fifth peristaltic pump 19, conductivity meter 20. PH value tester 21, sixth peristaltic pump 22, seventh peristaltic pump 23, eighth peristaltic pump 24, agitator.

Detailed ways

Please refer to Figure 1:

The system provided by the present invention for recovering carbon, nitrogen, phosphorus and water in sewage includes a sump 1, a grit chamber 2, a first reactor 3, a second reactor 4, a raw material liquid storage 5, a draw liquid storage device 6, permeable membrane module 7 and sedimentation tank 8, wherein the sump 1 is connected with the sewage pipe network, the sump 1 is connected with the grit chamber 2 through the pipeline, and the grit chamber 2 is also connected with the first reactor through the pipeline 3, the first reactor 3 is connected to the raw material liquid storage 5 and the second reactor 4 through pipelines respectively, the second reactor 4 is also connected to the sedimentation tank 8 through pipelines, and the raw material liquid storage 5 is connected to the The pipeline is also connected to the sedimentation tank 8, the raw material storage 5 and the draw solution storage 6 are connected through two pipelines, and the permeable membrane assembly 7 is assembled on the two connections between the raw material storage 5 and the draw solution storage 6 on the pipeline.

The sump 1 is provided with a grille 9 for separating the sundries in the sewage, and the connecting pipeline between the sump 1 and the grit chamber 2 is equipped with a lift pump 10 for pumping the sewage in the sump 1 into the grit chamber 2 Inside, the connecting pipeline between the grit chamber 2 and the first reactor 3 is equipped with a first peristaltic pump 11, and the grit chamber 2 is an aerated grit chamber.

The first reactor 3 is a high-load membrane bioreactor. The first reactor 3 is provided with an ultrafiltration membrane module 12 and an aeration stone 13. The effective area of the ultrafiltration membrane in the ultrafiltration membrane module 12 is 0.1m ² . Sheet size length × width × height = 320 × 220 × 5mm ³ , the membrane pore size is 0.1 μm, the connecting pipeline between the first reactor 3 and the second reactor 4 is provided with a second peristaltic pump 14, the first reactor 3 and the raw material liquid storage 5 are equipped with a third peristaltic pump 15 on the connecting pipeline, and the second reactor 4 is also provided with a connecting pipe 16 connected to the first reactor 3 and the raw material liquid storage 5 Pipelines are connected, the connecting pipe 16 is equipped with a fourth peristaltic pump 17, and the connecting pipeline between the second reactor 4 and the sedimentation tank 8 is equipped with a fifth peristaltic pump 18.

A conductivity meter 19 and a pH value tester 20 are arranged in the raw material storage 5, a sixth peristaltic pump 21 is installed on the connecting pipeline between the raw material storage 5 and the sedimentation tank 8, and the raw material storage 5 and the permeable membrane assembly 7 The seventh peristaltic pump 22 is installed on the connecting pipeline of the osmotic membrane module 7 and the eighth peristaltic pump 23 is installed on the connecting pipeline of the osmotic membrane module 7 and the draw solution reservoir 6. The osmotic membrane module 7 is composed of a forward osmosis membrane, and the effective area of the forward osmosis membrane is is 30cm ² , and the depth of the runner is 2mm.

The settling tank 8 is equipped with an agitator 24 and a pH value tester 20 .

The above-mentioned lift pump 10, first peristaltic pump 11, second peristaltic pump 14, third peristaltic pump 15, fourth peristaltic pump 17, fifth peristaltic pump 18, conductivity meter 19, pH value tester 20, sixth peristaltic pump The pump 21 , the seventh peristaltic pump 22 , the eighth peristaltic pump 23 and the agitator 24 are all assembled from existing equipment, so the specific models and specifications are not repeated.

The method provided by the invention for reclaiming carbon, nitrogen, phosphorus and water in sewage, its method is as follows:

Step 1, urban sewage enters the sump 1 through the sewage pipe network, and the sewage entering the sump 1 passes through the grid 9 to intercept most of the suspended matter and floating matter, and then enters the grit chamber 2 through the lift pump 10;

Step 2. The sewage entering the grit chamber 2 is pumped into the first reactor 3 for treatment. The first reactor 3 is provided with an ultrafiltration membrane module 7 and an aeration stone 13, and is separated after being filtered by the ultrafiltration membrane module 7. The water is pumped into the raw material liquid storage 5, and the concentrated liquid treated by the first reactor 3 is rich in separated organic matter and enters the second reactor 4 through the pipeline for anaerobic digestion to produce methane;

Step 3, the feedwater in the raw material liquid storage 5 is used as the raw material liquid, and the high-salt solution of KCl, the main component of the common agricultural fertilizer potassium fertilizer, is used as the drawing liquid in the drawing liquid storage 6. With the operation of the forward osmosis system, the high and low The osmotic pressure difference makes the raw material liquid in the raw material liquid storage 5 continuously enter the draw liquid storage 6 through the osmotic membrane module 7, and the diluted draw liquid can be directly used for farmland irrigation to realize the irrigation reuse of water resources. The nitrogen and phosphorus resources in the concentrated raw material liquid in the liquid storage device 5 are continuously enriched and then enter the sedimentation tank 8;

Step 4, the concentrated solution entering the sedimentation tank 8 generates struvite precipitation in the sedimentation tank 8 by adjusting the pH value, nitrogen, magnesium and phosphorus ratio conditions, and recycles it as a slow-release fertilizer, and the supernatant in the sedimentation tank 8 is pumped again It is returned to the second reactor 4 for anaerobic digestion, so as to realize the complete recovery of carbon resources;

Step 5: After anaerobic digestion in the second reactor 4 produces methane, the remaining nitrogen and phosphorus resources can be continuously recovered, and the supernatant in the second reactor 4 is returned to the raw material liquid storage 5 for reprocessing and utilization .

The grit chamber 2 in step 1 is an aerated grit chamber.

The ultrafiltration membrane used in the ultrafiltration membrane module 12 in step 2 is a flat membrane, the effective area of a single membrane is 0.1m ² , the size of the membrane is length×width×height=320×220×5mm ³ , and the membrane pore size is 0.1 μm. The material of the membrane is polyvinylidene fluoride, and the material of the support plate is acrylonitrile-butadiene-styrene copolymer.

The forward osmosis membrane used in the osmotic membrane module 7 in step 3 is an asymmetric membrane, consisting of an active layer and a support layer, wherein the material of the active layer is triacetate fiber, the material of the support layer is polyester, and the effective area of the forward osmosis membrane is 30cm ² , the runner depth is 2mm.

The struvite in step 4 is a slow-release fertilizer, containing Mg:N:P in a ratio of 1:1:1, and the pH value is controlled at 5-9.5, which is conducive to the formation of this compound fertilizer.

Working principle of the present invention:

Urban sewage enters the sump 1 through the municipal pipe network. After the sewage passes through the grid 9 to intercept most of the suspended solids and floating solids, it enters the grit chamber 2 through the lift pump 10 . The effluent water quality of grit chamber 2: COD concentration is 270mg/L, TN concentration is 56.9mg/L, NH ₄ ⁺ -N concentration is 47.8mg/L, TP concentration is 4.9mg/L, PO ₄ ^3- -P concentration is 4.14mg/L.

Then, the effluent from the grit chamber 2 enters the first reactor 3 through the first peristaltic pump 11 , and the first reactor 3 is provided with an ultrafiltration membrane module 12 and an aeration stone 13 . The effective area of the ultrafiltration membrane in the ultrafiltration membrane module 12 is 0.1 m ² , the size of the membrane is length×width×height=320×220×5 mm ³ , and the membrane pore diameter is 0.1 μm. After the operation is finished, a concentrated solution with a volume of 1/11.5 of the raw water is obtained, and the ultrafiltration membrane module 12 with a volume of 10.5/11.5 is discharged. While achieving low-carbon recovery of suspended solids and colloidal organic matter in sewage, membrane effluent rich in nitrogen and phosphorus is obtained, and the concentrated solution in the first reactor 3 enters the second reactor 4 anaerobically through the second peristaltic pump 14 Digestion produces methane to realize energy recovery; the effluent from the ultrafiltration membrane module 12 in the first reactor 3 does not contain solid matter and pathogens and is rich in nitrogen and phosphorus elements, and enters the raw material liquid storage 5 through the third peristaltic pump 15 to recover sewage Nitrogen and phosphorus resources. During operation, parameters such as aeration rate of 50 L/h, temperature of 25° C. and flux of 20 LMH in the first reactor 3 were controlled. The cleaning method of the ultrafiltration membrane in the ultrafiltration membrane module 12 is simple and convenient. Gently scrape off the organic matter on the membrane, return to the concentrated solution, and then clean the membrane surface with a certain volume of pure water, and return the cleaning solution to the concentrated solution. Then rinse the surface of the membrane with water to ensure that no obvious residual pollutants can be seen, and finally soak in sodium hypochlorite solution (available chlorine concentration 2000mg/L) for 2 hours, and then rinse the residual chemical agent on the surface of the membrane with water to restore 75% of the original state. The recovery rate of carbon resources can reach about 80%. The concentration of COD in the effluent of the ultrafiltration section is 42.89mg/L, the concentration of TN is 24.3mg/L, the concentration of NH ₄ ⁺ -N is 16.5mg/L, the concentration of TP is 6.43mg/L, and the concentration of PO ₄ ^3- -P is 6.4mg /L.

The effluent in the raw material liquid storage 5 is introduced into the osmotic membrane module 7 through the seventh peristaltic pump 22 . In the forward osmosis process of the osmotic membrane module 7, the raw material liquid reservoir 5 is used as the raw material liquid, and the high-salt solution of the main component KCl in the common agricultural fertilizer potassium fertilizer is used as the drawing liquid in the drawing liquid storage device 6, and the raw material liquid and The drawing liquid enters the permeable membrane module 7 through the seventh peristaltic pump 22 and the eighth peristaltic pump 23 respectively, and then returns to the raw material liquid storage 5 and the drawing liquid storage 6 respectively, and the volume of the concentrated liquid is 1/10 of the raw material liquid . Utilizing the high and low osmotic pressure difference, the water in the raw material storage 5 continuously enters the draw solution storage 6 through the osmotic membrane module 7, the effective area of the forward osmosis membrane in the osmotic membrane module ⁷ is 30cm2 (50mm×60mm), and the flow The track depth is 2mm. The diluted draw solution in the draw solution storage 6 can be directly used for farmland irrigation to realize the recovery of water resources, and the water reuse rate is over 85%; the nitrogen and phosphorus resources in the concentrated raw material liquid in the raw material storage 5 Concentrate and enrich continuously for subsequent struvite recovery. A conductivity meter 19 and a pH value tester 20 are arranged in the raw material liquid storage 5 . During the operation, control parameters such as cross-flow velocity of 15cm/s, temperature of 25°C, and concentration of draw solution of 2mol/L. After the forward osmosis membrane in the osmotic membrane module 7 is finished running, the membrane pollution is small and easy to clean. It only needs 15 minutes of physical cleaning (air-water ratio: 240L/h: 40L/h) to restore more than 75% of the membrane flux. The COD concentration of the concentrated liquid in the forward osmosis section is 220.88mg/L, the TN concentration is 123.93mg/L, the NH ₄ ⁺ -N concentration is 84.15mg/L, the TP concentration is 57.23mg/L, and the PO ₄ ^3- -P concentration is 56.96 mg/L.

The concentrated liquid in the raw material liquid storage 5 enters the sedimentation tank 8 through the sixth peristaltic pump 21 for chemical precipitation of struvite. The settling tank 8 is provided with a pH value tester 20 and an agitator 24 . By adjusting the pH value to 9.2, the reaction time is 20min, n(NH ₄ ⁺ ):n(Mg ²⁺ ):n(PO ₃ ^4- ) is 4:1.2:1, the stirring speed is 200rpm, and the precipitation time is 1h After collecting the supernatant, the precipitated part was dried at 40° C. for 48 hours. The nitrogen and phosphorus resources in the sewage are continuously concentrated and exist in the form of struvite precipitation. They can be recycled as slow-release fertilizers to realize the recovery of nitrogen and phosphorus resources. The nitrogen recovery rate is over 80%, and the phosphorus recovery rate is over 75%. The effective phosphorus content in the recovered phosphorus products is over 15%. The concentration of COD in the supernatant of sedimentation tank 8 is 220.88mg/L, the concentration of TN is 48.35mg/L, the concentration of NH ₄ ⁺ -N is 12.44mg/L, the concentration of TP is 10.31mg/L, and the concentration of PO ₄ ^3- -P is 10.2mg/L.

The supernatant from the sedimentation tank 8 enters the second reactor 4 through the fifth peristaltic pump 18 for anaerobic digestion to produce methane. After anaerobic digestion of methane, the gas production capacity is collected to realize the recovery of carbon resources; the sediment can be directly treated as solid waste. Since the nitrogen and phosphorus resources in the concentrated solution of the ultrafiltration section and the supernatant of the struvite recovery section have not been completely recovered, the supernatant after anaerobic digestion of methane in the second reactor 4 is returned to the raw material solution through the fourth peristaltic pump 17 Reservoir 5 continues to concentrate and enrich.

Claims (10)

1. A system for reclaiming carbon, nitrogen, phosphorus and water in sewage, characterized in that: it includes a sump, a grit chamber, a first reactor, a second reactor, a raw material liquid storage container, and a draw liquid storage device, permeable membrane module and sedimentation tank, wherein the sump is connected with the sewage pipe network, the sump is connected with the grit chamber through the pipeline, and the grit chamber is also connected with the first reactor through the pipeline, and the first reactor The raw material liquid storage and the second reactor are respectively connected through pipelines, the second reactor is also connected with the sedimentation tank through the pipeline, the raw material liquid storage is also connected with the sedimentation tank through the pipeline, the raw material liquid storage and The draw liquid storage is connected through two pipelines, and the permeable membrane assembly is assembled on the two connecting pipelines of the raw material storage and the draw liquid storage. 2. A system for reclaiming carbon, nitrogen, phosphorus and water in sewage according to claim 1, characterized in that: said sump is provided with a grid for intercepting suspended solids and floating solids in sewage The connection pipeline between the sump and the grit chamber is equipped with a lift pump for pumping the sewage in the sump into the grit chamber, and the connection pipeline between the grit chamber and the first reactor is equipped with a first peristaltic pump. The pool is an aerated grit chamber. 3. A system for reclaiming carbon, nitrogen, phosphorus and water in sewage according to claim 1, characterized in that: the first reactor is a high-load membrane bioreactor, and the first reactor An ultrafiltration membrane module and aeration stone are provided. The effective area ^of the ultrafiltration membrane in the ultrafiltration membrane module is 0.1m ² . A second peristaltic pump is installed on the connecting pipeline between the first reactor and the second reactor, a third peristaltic pump is installed on the connecting pipeline between the first reactor and the raw material liquid storage, and a second peristaltic pump is installed on the second reactor. There is a connecting pipe connected to the connecting pipe between the first reactor and the raw material liquid storage, the connecting pipe is equipped with a fourth peristaltic pump, and the connecting pipe between the second reactor and the sedimentation tank is equipped with a fifth peristaltic pump. 4. A system for reclaiming carbon, nitrogen, phosphorus and water in sewage according to claim 1, characterized in that: a conductivity meter and a pH value tester are arranged in the raw material liquid storage, and the raw material A sixth peristaltic pump is installed on the connecting pipeline between the liquid storage tank and the sedimentation tank, a seventh peristaltic pump is installed on the connecting pipeline between the raw material storage tank and the osmotic membrane module, and a seventh peristaltic pump is installed on the connecting pipeline between the osmotic membrane module and the draw solution storage tank. For the eighth peristaltic pump, the osmotic membrane module is composed of a forward osmosis membrane, the effective area of the forward osmosis membrane is 30cm ² , and the flow channel depth is 2mm. 5. A system for recovering carbon, nitrogen, phosphorus and water in sewage according to claim 1, characterized in that: said sedimentation tank is equipped with a stirrer and a pH value tester. 6. A method for reclaiming carbon, nitrogen, phosphorus and water in sewage, characterized in that: its method is as follows: Step 1. The urban sewage enters the sump through the sewage pipe network, and the sewage entering the sump passes through the grid to intercept most of the suspended matter and floating matter, and then enters the grit chamber through the lift pump; Step 2. The sewage entering the grit chamber is pumped into the first reactor for treatment. The first reactor is equipped with ultrafiltration membrane modules and aeration stones. After being filtered by the ultrafiltration membrane modules, the separated water is pumped into raw materials The liquid storage tank, the concentrated liquid treated by the first reactor is rich in separated organic matter and enters the second reactor through the pipeline for anaerobic digestion to produce methane; Step 3. The water in the raw material liquid storage is used as the raw material liquid, and the high-salt solution of KCl, the main component of common agricultural fertilizer potassium fertilizer, is used as the drawing liquid in the drawing liquid storage. With the operation of the forward osmosis system, the high and low osmotic pressure is used Poor, so that the raw material liquid in the raw material liquid storage continuously enters the draw liquid storage through the osmotic membrane module, and the diluted draw liquid can be directly used for farmland irrigation, realizing the irrigation reuse of water resources, and the concentration in the raw material liquid storage After the nitrogen and phosphorus resources in the raw material liquid are continuously concentrated and enriched, they enter the sedimentation tank; Step 4, the concentrated solution entering the sedimentation tank is adjusted to pH value, nitrogen, magnesium and phosphorus ratio conditions, and struvite precipitation is generated in the sedimentation tank, which is recycled as a slow-release fertilizer, and the supernatant in the sedimentation tank is pumped back to the Anaerobic digestion is carried out in the second reactor to realize the complete recovery of carbon resources; Step 5: After anaerobic digestion in the second reactor produces methane, the remaining nitrogen and phosphorus resources can be continuously recovered, and the supernatant in the second reactor is returned to the raw material liquid storage for reuse. 7. A method for recovering carbon, nitrogen, phosphorus and water in sewage according to claim 6, characterized in that: the grit chamber in step 1 is an aerated grit chamber. 8. A kind of method for reclaiming carbon, nitrogen, phosphorus and water in sewage according to claim 6, is characterized in that: the used ultrafiltration membrane of the ultrafiltration membrane assembly in the described step 2 is a flat membrane, and a single The effective area of the membrane is 0.1m ² , the size of the membrane is length×width×height=320×220×5mm ³ , the membrane aperture is 0.1μm, the membrane material is polyvinylidene fluoride, and the support plate material is acrylonitrile-butadiene - styrene copolymers. 9. A method for reclaiming carbon, nitrogen, phosphorus and water in sewage according to claim 6, characterized in that: the forward osmosis membrane used in the osmotic membrane assembly in the described step 3 belongs to an asymmetric membrane, and is formed by The active layer is composed of a support layer, wherein the material of the active layer is triacetate fiber, the material of the support layer is polyester, the effective area of the forward osmosis membrane is 30cm ² , and the depth of the flow channel is 2mm. 10. A kind of method for reclaiming carbon, nitrogen, phosphorus and water in sewage according to claim 6, is characterized in that: the struvite in the described step 4 is a kind of slow-release fertilizer, containing Mg: The ratio of N:P is 1:1:1, and the pH value is controlled at 5-9.5, which is conducive to the formation of this compound fertilizer.