Low-carbon emission efficient sewage resource treatment method

Abstract

The application discloses a low-carbon emission high-efficiency sewage resource treatment method, which is specifically a carbon capture method through a high-load activated sludge method, and supernatant and settling sludge are obtained after precipitation; the supernatant enters a water treatment system, and is treated through an anaerobic fluidized bed membrane biological reactor and reverse osmosis treatment successively, and reclaimed water and ammonia nitrogen are recovered; the settling sludge enters a sludge treatment system, and is treated through anaerobic digestion for methane production and sludge residue dehydration treatment successively after concentration, and biogas slurry obtained through dehydration is treated for nitrogen and phosphorus recovery. The application solves the problems of a traditional activated sludge process, such as the need of an external carbon source, a large amount of energy consumption of aeration and greenhouse gas emission, so as to shorten sewage treatment time and reduce sewage treatment energy consumption; and the process realizes carbon, nitrogen, phosphorus and water resource recovery in the maximum limit with the lowest carbon emission and the minimum energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of domestic sewage resource utilization, and particularly relates to a low-carbon-emission efficient sewage resource utilization treatment method. BACKGROUND

[0002] Current municipal wastewater treatment plants (WWTPs) are designed and operated with aerobic biological treatment as the core, including conventional activated sludge (CAS) and derived biological nutrient removal processes (BNR), which limit the resource recovery of wastewater. Because in WWTPs, the organic matter in wastewater is oxidized to CO2 by biological oxidation, and most of the ammonia nitrogen in wastewater is finally converted into nitrogen gas through different BNR processes (including nitrification-denitrification, partial nitritation-denitrification, autotrophic anaerobic ammonia oxidation, etc.), making carbon recovery and ammonium recovery impossible (both carbon and nitrogen sources are destructively removed). In addition, another challenge is that these biological oxidation processes consume a large amount of energy, and the energy consumption of activated sludge aeration accounts for about 50% to 60% of the total energy consumption of wastewater treatment plants; and the production and emission of N2O, which accounts for 80% of the total greenhouse gas emissions of wastewater treatment plants.

[0003] Nitrogen (N) and phosphorus (P) are essential elements for plant growth and are widely used as fertilizers in agriculture. However, the synthesis of ammonia requires an energy-intensive process (Haber-Bosch process) to convert nitrogen gas in the air into ammonia, with an energy consumption of 9.1-14.3 kWh / kg N and an average carbon emission of 6.9 kg CO2-equivalent (CO2-eq) / kg N. Phosphorus is mainly extracted from phosphate rock, which is a non-renewable resource. As the demand for phosphorus increases year by year and the reserves of phosphate rock will be depleted in about 50-100 years, it is obvious that the phosphorus crisis has become one of the most concerned problems by researchers. The amount of ammonia nitrogen (NH4 + -N) in domestic sewage is equivalent to 19% of the annual production of NH3-N, and the phosphorus contained in domestic sewage accounts for 22% of the global consumption, most of which ends in the form of phosphate (H2PO4 - , HPO4 2- , PO4 3- ) and can be regarded as a potential phosphorus source. Due to eutrophication of water bodies, nitrogen and phosphorus have become the main removal targets of WWTPs.

[0004] With the gradual transformation of the global economy from the linear economy of take-make-waste to the circular economy, the current urban sewage treatment process designed with the concept of linear economy is facing double pressure of economy and environment due to high energy consumption, greenhouse gas emission and waste generation. Resource recovery from sewage under the premise of meeting emission standards will change the status quo and extend the recycling of nutrients, energy and water to social recycling. Therefore, energy and nutrient recovery from sewage has become an inevitable trend to pursue sustainable sewage treatment. SUMMARY

[0005] The purpose of the present application is to provide a low-carbon emission and efficient sewage resource treatment method. The method realizes efficient recovery of carbon, nitrogen and phosphorus by combining carbon capture system, water treatment system and sludge treatment system, effectively improves the recovery rate of reclaimed water meeting the process standard, and reduces carbon emission and overall treatment cost during the treatment process.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A low-carbon emission and efficient sewage resource treatment method, characterized in that it comprises a carbon capture system, a water treatment system and a sludge treatment system. Specifically, carbon capture is carried out by high-load activated sludge method, and supernatant and settled sludge are obtained after sedimentation. The supernatant enters the water treatment system and is treated by anaerobic fluidized bed membrane bioreactor (AFMBR) and reverse osmosis (RO) in turn to recover reclaimed water and ammonia nitrogen. The settled sludge enters the sludge treatment system and is treated by anaerobic digestion to produce methane and sludge dewatering in turn. The sludge obtained by dewatering is subjected to nitrogen and phosphorus recovery, and the sludge after recovery of nitrogen and phosphorus is recycled to the carbon capture system for cyclic treatment.

[0008] Further, the high-load activated sludge method (HRAS) used in the carbon capture system is a high-rate contact stabilization process (HRCS), in which iron salt flocculant and biochar are added in the contact tank during the process. After treatment, supernatant and settled sludge are formed by sedimentation.

[0009] Further, the iron salt flocculant includes but is not limited to ferric chloride, polymeric ferric chloride, ferric sulfate or polymeric ferric sulfate, and the addition amount of the flocculant is added according to the molar ratio of metal ions to phosphorus (P) in the sewage of 1-1.5:1.

[0010] Further, the addition amount of the biochar is 45%-55% of the VSS mass in the contact tank during the HRCS treatment process.

[0011] Further, the settled sludge in the sedimentation tank is divided into two parts, one part is returned to the stabilization tank of the HRCS, the sludge return ratio is 60%, and the remaining part is concentrated, the remaining sludge is concentrated for 12 h, then the concentrated sludge is subjected to anaerobic digestion, the temperature is 35°C, the solid retention time is 20 d, the combustible gas generated in the anaerobic digestion process is collected, the biogas residue generated by anaerobic digestion is dewatered, and nitrogen and phosphorus are recovered in the biogas slurry.

[0012] The role of each link in the whole process is as follows:

[0013] High-rate contact stabilization process (HRCS): the alternating mechanism of "hunger" and "satiation" can promote biological flocculation and polymer production and storage process.

[0014] Anaerobic fluidized bed membrane bioreactor (AFMBR): the effluent separated by the sedimentation tank still contains part of the organic matter, which is converted into methane by AFMBR, and then the effluent is filtered by ultrafiltration membrane and discharged.

[0015] Reverse osmosis (RO): can effectively intercept NH4 + in the effluent, which is retained in the concentrated solution, and the effluent after the reverse osmosis membrane reaches the effluent standard of Singapore NEWater process.

[0016] Ammonia recovery in concentrated solution: by separating the concentrated solution of reverse osmosis, the nitrogen resources in the wastewater are recovered by flow measurement, NH3 can be recovered by adding alkali to convert ammonium into NH3, and then by gas membrane.

[0017] Sludge concentration and dewatering: part of the sludge discharged from the sedimentation tank is concentrated in the concentration tank to reduce the water content of the sludge.

[0018] Further, the supernatant flows into the water treatment system, is treated by AFMBR, then is treated by RO, the permeated water is collected, and the intercepted concentrated solution is recovered.

[0019] The role of RO is to intercept ions and organic matter in the effluent, in the RO unit, ammonia nitrogen is intercepted into the concentrated solution after permeation, the permeated water can meet the requirements of the reclaimed water process, and the ammonia nitrogen in the concentrated solution is recovered by existing ammonia nitrogen recovery technology.

[0020] Further, the HRT in the AFMBR treatment process is 2-3 h, the fluidized bed medium is granular activated carbon (GAC), the size is 10-30 mesh, the GAC fluidized expansion volume is 100%, the membrane is a hollow fiber ultrafiltration membrane made of polyvinylidene fluoride material, the pore size is 0.1 μm, the inner diameter is 1.9 mm, after treatment, further reverse osmosis filtration is carried out, under the condition of constant pressure 1.8 MPa, the cross-flow velocity is kept at 0.1 m / s.

[0021] In the carbon capture process, high rate contact stabilization process (HRCS) is adopted. Compared with the traditional HRAS process, although the combination of high load rate and short SRT of HRCS process can further improve the recovery rate of organic matter, the recovery rate can only reach 50%~60% of COD. Secondly, in this process, more than 80% of phosphates remain in the supernatant and enter the water treatment route. The organic matter entering the water treatment route produces methane gas in the subsequent AFMBR anaerobic treatment, affecting the water quality of the recovered water, which is also the recognized defect of HRCS, and at the same time, it causes more carbon emissions. In addition, a large amount of phosphates will scale in the water treatment process, pollute the interception membrane, cause the interception effect of the interception membrane to decrease, and the phosphorus and ammonia nitrogen entering the water treatment route form a mixture in the concentrate, which needs to increase the separation and recovery step, resulting in cost increase.

[0022] The present application increases the capture effect of organic matter in sewage by adding iron salt flocculant and biochar in the contact tank during carbon capture, and precipitates more organic matter into the sludge treatment route. Due to the short HRT of HRCS unit, it cannot meet the growth and reproduction conditions of nitrifying bacteria, so the ammonia nitrogen in the supernatant still remains in the form of ammonia nitrogen and enters the subsequent water treatment unit. In this process, it is found that the addition of biochar and iron salt flocculant can not only increase the carbon capture effect, but also effectively intercept the phosphates in the supernatant, so that they enter the sludge, which is transferred from the original water treatment route to the sludge treatment route, reducing the pollution of the interception membrane in the water treatment process, improving the water quality of the reclaimed water, and saving the subsequent nitrogen and phosphorus separation and treatment step. Due to the presence of biochar in the sludge, biochar significantly affects the microbial community structure, promotes interspecies direct electron transfer and mutual metabolism of methanogens and bacteria, and further increases the relative abundance of hydrogenotrophic methanogens in the methane production process of residual sludge, effectively improving the methane production in the anaerobic digestion process of sludge. In addition, biochar plays a role in supporting the framework in the mud cake, forming a water filtration channel, and promoting the dewatering of biogas residue.

[0023] The biogas slurry obtained by dewatering the biogas residue is recycled back to the HRCS system after nitrogen and phosphorus recovery, which can relatively reduce the concentration of phosphates in the supernatant and improve the generation efficiency of reclaimed water meeting the standards.

[0024] Most specifically, a low-carbon emission and efficient sewage resource treatment method, characterized in that it comprises the following steps:

[0025] (1) Carbon capture treatment

[0026] The sewage pretreated by screen and grit chamber is introduced into the HRCS unit for treatment, iron salt flocculant and biochar are added during the treatment, and after the treatment, the supernatant and settled sludge are obtained by separating the mud and water in the sedimentation tank;

[0027] (2) Water treatment

[0028] The supernatant obtained in step (1) is introduced into an anaerobic fluidized bed membrane bioreactor (AFMBR) for treatment, and after the treatment is completed, reverse osmosis is further performed, the water permeating through the osmosis membrane is recovered as reclaimed water, and the concentrated solution blocked by the osmosis membrane is subjected to ammonia nitrogen recovery;

[0029] (3) Sludge treatment

[0030] The settled sludge obtained in step (1) is divided into two parts, one part is returned to the stabilization tank of the HRCS at a sludge return ratio of 60%, and the remaining part is subjected to concentration treatment, and then subjected to anaerobic digestion, the combustible gas generated in the anaerobic digestion process is collected for utilization, the biogas residue generated in the anaerobic digestion is dewatered, and the biogas slurry obtained by dewatering is subjected to nitrogen and phosphorus recovery, and the biogas slurry after recovery of nitrogen and phosphorus is returned to the carbon capture system for recycling treatment.

[0031] The present application has the following technical effects:

[0032] The present application forms a complete sewage treatment process by a two-line three-system, efficiently recovers carbon, nitrogen and phosphorus in sewage, fully resources the sewage, converts more sewage into reclaimed water meeting the standards, and solves the problems of traditional activated sludge process, such as the need for additional carbon source, large energy consumption of aeration and greenhouse gas emission, so as to shorten the sewage treatment time and reduce the energy consumption of sewage treatment, and the process recovers carbon, nitrogen, phosphorus and water resources with the lowest carbon emission and the smallest energy consumption, effectively reduces the treatment cost. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 : Sewage resourceization process flow diagram. DETAILED DESCRIPTION

[0034] The present application will be specifically described below by examples, and it is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application, and those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above content of the present application.

[0035] A low-carbon emission efficient sewage resourceization treatment method, comprising the following steps:

[0036] (1) Carbon capture treatment

[0037] The sewage pretreated by screen and grit chamber is introduced into the HRCS unit for treatment, the HRT of the stabilization tank is 40 min, the dissolved oxygen is maintained at 2-4 mg / L, the HRT of the contact tank is 15 min, and iron salt flocculants and biochar are added during the treatment process. After the treatment, the sewage is discharged into the sedimentation tank for mud-water separation to obtain supernatant and settled sludge. The iron salt flocculants include but are not limited to ferric chloride, polymeric ferric chloride, ferric sulfate or polymeric ferric sulfate. The iron salt flocculants are added in a molar ratio of iron ion: phosphorus of 1-1.5:1. The phosphorus is the total phosphorus in the sewage. The addition amount of biochar is 45%-55% of the total VSS mass in the contact tank during the HRCS treatment process.

[0038] (2) Water treatment

[0039] The supernatant obtained in step (1) is introduced into the AFMBR for treatment, the HRT is 2-3 h, the fluidized bed medium is GAC, the size is 10-30 mesh, the GAC fluidized expansion volume is 100%, the membrane is a hollow fiber ultrafiltration membrane made of polyvinylidene fluoride, the pore size is 0.1 μm, and the inner diameter is 1.9 mm. After treatment, further reverse osmosis filtration is carried out (the reverse osmosis membrane is BW-30, DOW FilmTec TM , USA), operated under constant pressure of 1.8 MPa, the cross-flow velocity is maintained at 0.1 m / s, the water permeated through the membrane is recovered as reclaimed water, and the concentrated liquid blocked by the membrane is used for ammonia nitrogen recovery;

[0040] (3) Sludge treatment

[0041] The settled sludge in the sedimentation tank in step (1) is divided into two parts, one part is backflowed into the stabilization tank of the HRCS, the sludge backflow ratio is 60%, and the remaining part is concentrated. The remaining sludge is left to concentrate for 12 h, then the concentrated sludge is subjected to anaerobic digestion at a temperature of 35℃ and a solid retention time of 20 d. The combustible gas generated during anaerobic digestion is collected, the biogas residue generated by anaerobic digestion is dewatered, nitrogen and phosphorus are recovered from the biogas slurry, and the biogas slurry after recovery of nitrogen and phosphorus is backflowed to the carbon capture system for recycling.

[0042] The steps of recovering ammonia nitrogen from the concentrated liquid are as follows:

[0043] An alkali solution is added to the concentrated liquid blocked by the membrane, the pH is adjusted to above 10, and the concentrated liquid is heated to 35-50℃ to make the ammonium ion into free gaseous ammonia.

[0044] The steps of recovering nitrogen and phosphorus from the biogas slurry are as follows:

[0045] The biogas slurry is taken, the pH of the biogas slurry is adjusted, a magnesium source MgCl2 is added, so that the molar ratio of Mg:P is 1.2:1, the reaction is stirred at 400 rpm for 20 min, the precipitation is performed for 50 min, the solution after the reaction is completed is centrifuged to obtain struvite.

[0046] The sewage treated in the application is municipal sewage, wherein (COD is 500±46 mg / L, TKN is 49±7 mg / L, TP is 16±2 mg / L, and SS is 200±41 mg / L).

[0047] Example 1

[0048] A low-carbon emission efficient sewage resource treatment method, comprising the following steps:

[0049] (1) Carbon capture treatment

[0050] The sewage pretreated by a screen and a grit chamber is introduced into an HRCS unit for treatment, the HRT of a stabilization tank is 40 min, the dissolved oxygen is maintained at 2-4 mg / L, the HRT of a contact tank is 15 min, ferric sulfate flocculant and biochar are added during the treatment, after the treatment, the sewage is discharged into a sedimentation tank for mud-water separation to obtain supernatant and settled sludge, the ferric sulfate flocculant is added according to a molar ratio of iron ions to phosphorus of 1.2:1, the phosphorus is total phosphorus in the sewage, and the addition amount of the biochar is 50% of the total VSS mass in the contact tank during the HRCS treatment;

[0051] (2) Water treatment

[0052] The supernatant obtained in step (1) is introduced into an AFMBR for treatment, the HRT is 2.5 h, the fluidized bed medium is GAC, the size is 10-30 mesh, the GAC fluidized expansion volume is 100%, the membrane is a hollow fiber ultrafiltration membrane made of polyvinylidene fluoride, the pore size is 0.1 μm, and the inner diameter is 1.9 mm, after the treatment, reverse osmosis filtration is further performed (the reverse osmosis membrane is BW-30, DOW FilmTec TM , USA), under the condition of a constant pressure of 1.8 MPa, the cross-flow speed is kept at 0.1 m / s, the water permeated through the membrane is recovered as reclaimed water, and the concentrated liquid blocked by the membrane is used for ammonia nitrogen recovery;

[0053] (3) Sludge treatment

[0054] The settled sludge in the step (1) sedimentation tank is divided into two parts, one part is returned to the stabilization tank of the HRCS, the sludge return ratio is 60%, and the remaining part is concentrated, the remaining sludge is concentrated for 12 h, then the concentrated sludge is subjected to anaerobic digestion, the temperature is 35°C, the solid retention time is 20 d, the combustible gas generated in the anaerobic digestion process is collected for utilization, the biogas residue generated in the anaerobic digestion is subjected to dewatering treatment, phosphorus is recovered from the biogas slurry, and the biogas slurry after recovering nitrogen and phosphorus is returned to the carbon capture system for recycling treatment.

[0055] The dewatered biogas residue can also be further treated as a resource.

[0056] Comparative Example 1

[0057] Compared with Example 1, no flocculant and biochar are added in the carbon capture step, and the remaining steps are completely the same.

[0058] Comparative Example 2

[0059] Compared with Example 1, an equal amount of ferric sulfate flocculant is added in the carbon capture step, but no biochar is added, and the remaining steps are completely the same.

[0060] Comparative Example 3

[0061] Compared with Example 1, an appropriate amount of flocculant and biochar are added, the flocculant is polyacrylamide instead of ferric sulfate in Example 1, and the remaining steps are the same as Example 1.

[0062] The water quality of the supernatant after treatment by different carbon capture systems is shown in Table 1.

[0063] Table 1: Water quality of supernatant after treatment by different carbon capture systems

[0064]

[0065] It can be seen that after the carbon capture system treatment, the contents of COD, total phosphorus, total nitrogen and SS in the supernatant of Example 1 of the present application are significantly reduced, while the contents of COD, total phosphorus, total nitrogen and SS in Comparative Example 1 are the highest among all carbon capture schemes. The overall effect is not ideal after adding other flocculants and biochar to the carbon capture system or using a single flocculant.

[0066] After the supernatant is treated by the water treatment system, the water passing through the reverse osmosis is reclaimed water, and the reclaimed water quality is referenced to the NEWater process effluent standard of Singapore, as shown in Table 2.

[0067] Table 2: NEWater process effluent standard

[0068]

[0069] According to the NEWater process effluent standard, the reclaimed water treated by the scheme of Example 1 and each comparative example is detected, and the detection results are shown in Table 3.

[0070] Table 3: Reclaimed water effluent parameters in each scheme

[0071]

[0072] As can be seen from the above table, the ammonium nitrogen in the reclaimed water of Comparative Examples 1-3 cannot meet the process effluent requirements, and needs to be further treated subsequently, while the effluent of the present application meets the reclaimed water process effluent standard.

[0073] By counting the cost of treating 1 ton of sewage, the benefits of recovering nitrogen, phosphorus and methane, and the carbon emissions generated during the entire treatment process, the results are shown in Table 4, wherein the recovery of phosphorus includes the possible recovery of phosphorus in the sludge, biogas slurry and water treatment route, and the recovery of nitrogen includes the recovery of ammonia nitrogen in the water treatment route and the recovery of nitrogen and phosphorus in the biogas slurry. Due to the need for additional treatment steps in the comparative examples to achieve better nitrogen and phosphorus recovery, reprocessing of reclaimed water, etc., the data corresponding to each comparative example in the following table is the final data result obtained by adding additional treatment steps.

[0074] Table 4: Cost, benefit and carbon emission of each scheme for treating 1 ton of sewage

[0075]

[0076] As can be seen from the above table, Example 1 of the present application can produce 94.13 L of methane per ton of sewage treated, the nitrogen recovery rate reaches 88.4%, the phosphorus recovery rate reaches 97.6%, the carbon emission is only 0.12 kg CO2e, and the treatment cost is also low. However, Comparative Examples 1-3 need to add additional treatment steps, which requires more treatment cost, and the carbon emission is significantly higher than that of the present application. As can be seen from the comparison between Example 1 and Comparative Example 2, the addition of biochar improves the efficiency of methane production from sludge.

[0077] Example 2

[0078] A low-carbon emission and efficient sewage resource treatment method, comprising the following steps:

[0079] (1) Carbon capture treatment

[0080] The sewage pretreated by screen and grit chamber is introduced into the HRCS unit for treatment, the HRT of the stabilization tank is 40 min, the dissolved oxygen is maintained at 2-4 mg / L, the HRT of the contact tank is 15 min, and the ferric chloride flocculant and biochar are added during the treatment process, and the supernatant and settled sludge are obtained after the treatment ends and the sludge-water separation in the sedimentation tank, the ferric chloride flocculant is added according to the molar ratio of iron ion to phosphorus of 1.5:1, the phosphorus is the total phosphorus in the sewage, and the addition amount of biochar is 45% of the total VSS mass in the contact tank during the HRCS treatment process;

[0081] (2) Water treatment

[0082] The supernatant obtained in step (1) is introduced into the AFMBR for treatment, the HRT is 2-3 h, the fluidized bed medium is GAC, the size is 10-30 mesh, the GAC fluidized expansion volume is 100%, the membrane is a hollow fiber ultrafiltration membrane made of polyvinylidene fluoride, the pore size is 0.1 μm, and the inner diameter is 1.9 mm, and after the treatment, reverse osmosis filtration is further carried out (the reverse osmosis membrane is BW-30, DOW FilmTec TM , USA), under the condition of constant pressure 1.8 MPa, the cross-flow velocity is kept at 0.1 m / s, the water permeated through the membrane is recovered as reclaimed water, and the concentrated liquid blocked by the membrane is used for ammonia nitrogen recovery;

[0083] (3) Sludge treatment

[0084] The settled sludge in the sedimentation tank in step (1) is divided into two parts, one part is backflowed into the stabilization tank of the HRCS, the sludge backflow ratio is 60%, and the remaining part is concentrated, the remaining sludge is concentrated for 12 h, then the concentrated sludge is subjected to anaerobic digestion, the temperature is 35℃, the solid retention time is 20 d, the combustible gas generated in the anaerobic digestion process is collected for utilization, the biogas residue generated in the anaerobic digestion is subjected to dewatering treatment, and the biogas slurry obtained by dewatering is subjected to nitrogen and phosphorus recovery.

[0085] This embodiment can produce 93.75 L of methane per ton of sewage treated, the nitrogen recovery rate reaches 87.3%, the phosphorus recovery rate reaches 97.1%, and the carbon emission is only 0.13 kg CO2e.

[0086] Example 3

[0087] A low-carbon emission efficient sewage resource treatment method, characterized in that it comprises the following steps:

[0088] (1) Carbon capture treatment

[0089] The sewage pretreated by screen and grit chamber is introduced into the HRCS unit for treatment, the HRT of the stabilization tank is 40 min, the dissolved oxygen is maintained at 2-4 mg / L, the HRT of the contact tank is 15 min, and the iron salt flocculant and biochar are added during the treatment process. After the treatment, the sewage is discharged into the sedimentation tank for mud-water separation to obtain the supernatant and settled sludge. The iron salt flocculant is added according to the molar ratio of iron ion to phosphorus of 1:1, and the phosphorus is the total phosphorus in the sewage. The addition amount of biochar is 55% of the total VSS mass in the contact tank during the HRCS treatment process.

[0090] (2) Water treatment

[0091] The supernatant obtained in step (1) is introduced into the AFMBR for treatment, the HRT is 2-3 h, the fluidized bed medium is GAC, the size is 10-30 mesh, the GAC fluidized expansion volume is 100%, the membrane is a hollow fiber ultrafiltration membrane made of polyvinylidene fluoride, the pore size is 0.1 μm, and the inner diameter is 1.9 mm. After treatment, further reverse osmosis filtration is carried out (the reverse osmosis membrane is BW-30, DOW FilmTec TM , USA), and the operation is carried out under the condition of constant pressure 1.8 MPa, the cross-flow velocity is kept at 0.1 m / s, the water permeated through the membrane is recovered as reclaimed water, and the concentrated liquid blocked by the membrane is used for ammonia nitrogen recovery;

[0092] (3) Sludge treatment

[0093] The settled sludge in the sedimentation tank in step (1) is divided into two parts, one part is backflowed into the stabilization tank of the HRCS, the sludge backflow ratio is 60%, and the remaining part is concentrated. The remaining sludge is concentrated for 12 h, and then the concentrated sludge is subjected to anaerobic digestion at a temperature of 35℃ and a solid retention time of 20 d. The combustible gas generated during anaerobic digestion is collected for use, and the biogas residue produced by anaerobic digestion is subjected to dewatering treatment, and the dewatered biogas liquid is subjected to nitrogen and phosphorus recovery.

[0094] This embodiment can produce 93.37 L of methane per ton of sewage treated, the nitrogen recovery rate reaches 87.7%, the phosphorus recovery rate reaches 96.9%, and the carbon emission is only 0.13 kg CO2e.

Claims

1. A low-carbon emission, high-efficiency wastewater resource utilization treatment method, characterized in that: The application relates to a carbon capture system, a water treatment system and a sludge treatment system, and specifically relates to carbon capture through a high-rate contact stabilization process (HRCS), supernatant and settled sludge are obtained after precipitation, the supernatant enters the water treatment system, and is sequentially treated through an anaerobic fluidized bed membrane bioreactor and reverse osmosis treatment, recycled water and ammonia nitrogen are recovered, the settled sludge enters the sludge treatment system, and is sequentially treated through anaerobic digestion to produce methane and sludge dewatering after concentration, slurry is obtained through dewatering, nitrogen and phosphorus are recovered from the slurry, the slurry after recovery of nitrogen and phosphorus is returned to the carbon capture system for cyclic treatment, the hydraulic retention time (HRT) of a stabilization tank of the HRCS is 40 min, dissolved oxygen is maintained at 2-4 mg / L, the HRT of a contact tank is 15 min, iron salt flocculants and biochar are added in the contact tank in the process, supernatant and settled sludge are formed after precipitation after treatment; the iron salt flocculants include but are not limited to ferric chloride, polymeric ferric chloride, ferric sulfate or polymeric ferric sulfate, the addition amount of the flocculants is added according to the molar ratio of metal ions to phosphorus in the sewage of 1-1.5:1, and the addition amount of the biochar is 45%-55% of the VSS mass in the contact tank in the HRCS treatment process.

2. The low-carbon emission and high-efficiency wastewater resourceful treatment method according to claim 1, characterized in that: The supernatant enters the water treatment system, the supernatant is treated through an anaerobic fluidized bed membrane bioreactor (AFMBR), then is treated through reverse osmosis (RO), collected permeate water is recycled water, and concentrated liquid intercepted during the treatment is recovered for ammonia nitrogen recovery.

3. The low-carbon emission and high-efficiency wastewater resourceful treatment method according to claim 2, characterized in that: The HRT of the AFMBR treatment is 2-3 h, the fluidized bed medium is granular activated carbon (GAC) with a size of 10-30 meshes, the GAC fluidized expansion volume is 100%, the hollow fiber ultrafiltration membrane made of polyvinylidene fluoride material is adopted, the pore size is 0.1 mu m, the inner diameter is 1.9 mm, and the treatment is further carried out through reverse osmosis filtration under the condition that the constant pressure is 1.8 MPa and the cross-flow speed is kept at 0.1 m / s.

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