Energy self-sufficient urban sewage treatment system and method

Abstract

The present invention discloses an energy-self-sufficient urban sewage treatment system, including a carbon capture unit, a pure membrane PN / A-MABR unit, a deep denitrification unit, a tertiary treatment unit, an anaerobic digestion unit, a sludge dehydration unit and a mud-membrane composite PN / A-MABR unit; the carbon capture unit, the pure membrane PN / A-MABR unit, the deep denitrification unit and the tertiary treatment unit are connected in sequence; the anaerobic digestion unit is respectively connected to the carbon capture unit and the deep denitrification unit; the anaerobic digestion unit, the sludge dehydration unit, the mud-membrane composite PN / A-MABR unit and the pure membrane PN / A-MABR unit are connected in sequence. The present invention also discloses a method for treating sewage using an energy-self-sufficient urban sewage treatment system. The present invention takes the PN / A-MABR denitrification process as the core, supplemented by the front-end carbon capture technology, to achieve low-carbon and high-efficiency pollution removal of mainstream and sidestream sewage, and has universal engineering application value.

Description

Technical Field

[0001] The invention relates to an energy self-sufficient urban sewage treatment system and method, belonging to the technical field of sewage treatment. Background Art

[0002] Urban sewage treatment plants are an important part of urban infrastructure. They can effectively remove pollutants such as carbon, nitrogen, and phosphorus from sewage, and play a key role in improving water environment quality and ensuring water ecological safety. However, the traditional sewage treatment system adopts the "high energy consumption in exchange for high water quality" model, which is contrary to the concept of sustainable development in the "dual carbon" era. In particular, the biological denitrification process in the traditional sewage treatment system, which removes nitrogen through the metabolic activities of nitrifying bacteria and denitrifying bacteria, consumes a lot of energy and carbon sources, and produces a large amount of residual sludge, while emitting a large amount of greenhouse gases. Therefore, it is urgent to develop an energy-self-sufficient urban sewage treatment system for the future.

[0003] The membrane aerated biofilm reactor (MABR) coupled with the short-range nitrification / anaerobic ammonium oxidation (PN / A) process is an energy-efficient biological denitrification technology for sewage, which can achieve low-cost and high-efficiency denitrification of urban sewage. Among them, MABR is a new type of oxygen supply device with the significant advantages of high oxygen mass transfer efficiency and low secondary pollution. The PN / A denitrification process has overturned the traditional nitrification / denitrification process, which can greatly reduce aeration energy consumption, carbon source consumption, excess sludge production and greenhouse gas release. The combination of the two can effectively reduce the energy consumption and material consumption input in the sewage denitrification process, and is an economically feasible and environmentally friendly new biological denitrification technology. In addition, sewage contains abundant organic chemical energy. By capturing and extracting organic chemical energy and converting it into electrical energy, part of the energy consumption in the sewage treatment process can be offset, and even energy self-sufficiency can be achieved. Therefore, with the PN / A-MABR biological denitrification process as the core, supplemented by front-end carbon capture technology, an energy-self-sufficient sewage treatment system is constructed to achieve deep decontamination of mainstream and sidestream sewage, which is of great significance to promoting the synergistic efficiency of pollution reduction and carbon reduction in urban sewage treatment. Summary of the invention

[0004] In view of the above-mentioned prior art, in order to solve the drawbacks of the "high energy consumption for high water quality" model of the sewage treatment system, the present invention provides an energy-self-sufficient urban sewage treatment system and method. The present invention takes the PN / A-MABR denitrification process as the core, supplemented by the front-end carbon capture technology, and constructs the mainstream and side stream sewage treatment system and process.

[0005] The present invention is achieved through the following technical solutions:

[0006] An energy-self-sufficient urban sewage treatment system comprises a carbon capture unit, a pure membrane PN / A-MABR unit, a deep denitrification unit, a tertiary treatment unit, an anaerobic digestion unit, a sludge dewatering unit and a mud-membrane composite PN / A-MABR unit; wherein the carbon capture unit, the pure membrane PN / A-MABR unit, the deep denitrification unit and the tertiary treatment unit are connected in sequence; the anaerobic digestion unit is connected to the carbon capture unit and the deep denitrification unit respectively; the anaerobic digestion unit, the sludge dewatering unit, the mud-membrane composite PN / A-MABR unit and the pure membrane PN / A-MABR unit are connected in sequence.

[0007] The carbon capture unit, pure membrane PN / A-MABR unit, deep denitrification unit, tertiary treatment unit, anaerobic digestion unit, and sludge dewatering unit are all existing devices or equipment in the prior art, and their composition structures and working principles are all existing technologies, which will not be elaborated in the present invention.

[0008] The mud membrane composite PN / A-MABR unit can achieve 80% to 85% TN removal in the sludge digestion supernatant through the mud membrane composite PN / A-MABR unit, and its structure is: including a mud membrane composite PN / A-MABR, a water inlet tank, a water outlet tank, an internal reflux pump, an aeration pump, a DO meter and a DO sensor; wherein,

[0009] The mud membrane composite PN / A-MABR is provided with a water inlet, a water outlet and two internal reflux ports, the water inlet is connected to the water inlet tank, the water outlet is connected to the water outlet tank, and the two internal reflux ports are connected through an internal reflux pump;

[0010] The mud-membrane composite PN / A-MABR is provided with a second MABR membrane assembly; the second MABR membrane assembly is composed of a plurality of second hydrophobic and breathable membranes, and the packing density of the membrane area is 100-150 m 2 / m 3 The second MABR membrane assembly is provided with an air inlet and an air outlet, and the air inlet is connected to an aeration pump;

[0011] The DO sensor is placed in the mud membrane composite PN / A-MABR and connected to the DO measuring instrument.

[0012] Furthermore, the water inlet is connected to the water inlet tank via a water inlet pump.

[0013] Furthermore, a gas flow meter and a pressure gauge are provided on the connecting pipeline between the air inlet and the aeration pump.

[0014] Furthermore, an exhaust gas regulating valve is provided on the pipeline connected to the gas outlet.

[0015] Furthermore, the second hydrophobic breathable membrane is any one of a hollow fiber membrane, a plate membrane, a roll membrane, and a tubular membrane.

[0016] (Note: The structure of the mud-membrane composite PN / A-MABR is introduced above, and its specific working principle and effect are also specially introduced later) Further, the carbon capture unit is composed of a high-load activated sludge process reaction tank, and the first and second sedimentation tanks connected to the high-load activated sludge process reaction tank. The bottom of the first and second sedimentation tanks can also be connected to the high-load activated sludge process reaction tank through the first sludge return unit. The organic matter in the sewage is captured in the high-load activated sludge process reaction tank. The effluent of the high-load activated sludge process reaction tank enters the first and second sedimentation tanks for mud and water separation. The effluent of the first and second sedimentation tanks enters the pure membrane PN / A-MABR unit, and a part of the concentrated sludge at the bottom can be returned to the high-load activated sludge process reaction tank through the first sludge return unit, and the remaining concentrated sludge enters the anaerobic digestion unit. Of course, the carbon capture unit of the present invention is not limited to the device using the high-load activated sludge process, and other devices that meet the carbon capture requirements can also be used as pretreatment units, such as the use of primary enhanced chemical treatment, magnetic coagulation process devices, etc.

[0017] Furthermore, the pure membrane type PN / A-MABR unit is provided with a plurality of first MABR membrane modules composed of a first hydrophobic breathable membrane; the first hydrophobic breathable membrane is any one of a hollow fiber membrane, a plate membrane, a roll membrane, and a tubular membrane, and the packing density of the membrane area is 150 to 200 m 2 / m 3 The hydraulic retention time (HRT) of the pure membrane PN / A-MABR unit is 6-8h, the liquid phase DO is less than 0.05 mg / L, and the biofilm thickness on the first hydrophobic breathable membrane is 400-800 μm. The unit can remove about 10% of organic matter in the influent, 90% of NH4 + and 75% of TN, of which 93.5% was removed by the Anammox autotrophic denitrification pathway and 6.5% by denitrification heterotrophic denitrification.

[0018] Furthermore, the deep denitrification unit is composed of a denitrification biochemical tank and a second secondary sedimentation tank connected to the denitrification biochemical tank. The bottom of the second secondary sedimentation tank can also be connected to the anoxic tank of the denitrification biochemical tank through a second sludge return unit; wherein, the denitrification biochemical tank is composed of an anoxic tank and an aerobic tank connected to the anoxic tank. The bottom of the aerobic tank can also be connected to the anoxic tank through a nitrification liquid return unit. In the anoxic tank, DO < 0.05 mg / L, denitrifying bacteria use external carbon sources (such as sodium acetate) / microbial internal carbon sources to remove about 10% of TN in the influent; in the aerobic tank, DO is 1 ~ 3 mg / L, and nitrifying bacteria further oxidize residual NH4 +, the removal rate is 5% to 10%. A portion of the mud-water mixture at the end of the aerobic tank can enter the anoxic tank through the nitrification liquid reflux unit, and the remaining mud-water mixture enters the second secondary sedimentation tank for mud-water separation. The supernatant after mud-water separation in the second secondary sedimentation tank enters the tertiary treatment unit, and a portion of the concentrated sludge can be returned to the anoxic tank through the second sludge reflux unit, and the remaining concentrated sludge enters the anaerobic digestion unit through the second residual sludge discharge unit. Of course, the deep denitrification unit of the present invention is not limited to the combination of the denitrification biochemical tank and the second secondary sedimentation tank, and other deep denitrification devices are also possible, such as a sulfur autotrophic denitrification biochemical tank.

[0019] Furthermore, the three-stage treatment unit consists of a coagulation sedimentation tank, a V-type filter tank and an ultraviolet disinfection channel connected in sequence, which can remove pollutants such as phosphorus, suspended solids, pathogenic bacteria, etc. The removal rate of phosphorus in the influent can reach 98%, the removal rate of suspended solids can reach more than 90%, and the effluent E. coli is within the standard range.

[0020] The anaerobic digestion unit can use sludge for anaerobic fermentation (fermentation temperature is 30°C), the reaction time is 15 to 20 days, the external carbon source adsorbed by the sludge and the internal carbon source of the microorganisms are fully anaerobically decomposed and methane is produced. Furthermore, the anaerobic digestion unit can be connected to the methane collection and utilization unit, and the methane produced by anaerobic decomposition in the anaerobic digestion unit can enter the methane collection and utilization unit for efficient recovery and energy conversion. Furthermore, the anaerobic digestion unit can not only receive sludge from the carbon capture unit and the deep denitrification unit, but other substances that can be fermented to produce methane can also be used as raw materials for anaerobic digestion, such as food waste.

[0021] The sludge dewatering unit can use centrifugal, filter belt, plate and frame dewatering machines to separate the digested liquid and sludge in the digested sludge. The dewatering performance of the digested sludge is improved by adding sludge conditioners such as polyacrylamide, and the moisture content is reduced from 95% to 98% to 60% to 80%.

[0022] Furthermore, the sludge dewatering unit may be connected to a sludge disposal unit, and the sludge disposal unit may further process and dispose of the dewatered sludge cake.

[0023] Furthermore, the anaerobic digestion unit is connected to the carbon capture unit via the first excess sludge discharge unit; the anaerobic digestion unit is connected to the deep denitrification unit via the second excess sludge discharge unit. (Note: The above is an introduction to the structural composition, and the introduction to the method steps is below, so there is no lack of the step of "obtaining denitrified sewage" here)

[0024] The energy self-sufficient urban sewage treatment system is used in treating urban sewage.

[0025] A method for treating sewage using an energy self-sufficient urban sewage treatment system comprises the following steps:

[0026] (1) The sewage enters the carbon capture unit and is treated by the carbon capture unit to obtain low-carbon nitrogen-containing sewage and carbon-rich sludge; the low-carbon nitrogen-containing sewage is discharged to the pure membrane PN / A-MABR unit, and the carbon-rich sludge is discharged to the anaerobic digestion unit; most of the organic matter in the sewage is captured in this unit;

[0027] (2) After the low-carbon nitrogen-containing sewage is treated by the pure membrane PN / A-MABR unit, the initial denitrification sewage is obtained and discharged to the deep denitrification unit;

[0028] The low-carbon and nitrogen-containing sewage undergoes the Anammox short-process autotrophic denitrification process in the pure membrane PN / A-MABR unit; ammonia oxidizing bacteria (AOB) and anaerobic ammonia oxidizing bacteria (AnAOB) are attached to the surface of the first hydrophobic breathable membrane in the form of biofilms, AOB mainly grows in the aerobic layer inside the biofilm, and AnAOB mainly colonizes in the anoxic layer outside the biofilm; under the cooperation of AOB and AnAOB, most of the NH4 + be removed;

[0029] (3) After the initial denitrification wastewater is treated in the deep denitrification unit, deep denitrification wastewater and sludge are obtained. The deep denitrification wastewater is discharged to the tertiary treatment unit, and the sludge is discharged to the anaerobic digestion unit;

[0030] The deep denitrification unit uses biological denitrification technology to remove the remaining NO3 - and NH4 + Further removal plays an important role in ensuring that the effluent meets the standards;

[0031] (4) After the deep denitrification wastewater is treated in the tertiary treatment unit, the reclaimed water is obtained and reused or discharged to the corresponding receiving water body;

[0032] After denitrification and carbon removal, the sewage is deeply treated in the tertiary treatment unit (including coagulation, sedimentation, filtration, disinfection, etc.) to remove pollutants such as phosphorus, suspended solids, and pathogenic bacteria. The water quality of the obtained reclaimed water meets the Class A standard of "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" GB18918-2002;

[0033] (5) After the sludge is treated in the anaerobic digestion unit, a sludge-water mixture is obtained and discharged to the sludge dewatering unit;

[0034] The residual sludge discharged from the carbon capture unit and the deep denitrification unit is anaerobically digested in the anaerobic digestion unit. The external carbon source adsorbed on the sludge surface and the carbon source within the microorganisms are converted into methane in the anaerobic digestion unit. The generated methane gas can be used to generate electricity through the methane collection and utilization unit, thus realizing resource utilization while reducing the sludge.

[0035] (6) After the sludge-water mixture is treated in the sludge dehydration unit, sludge digestion supernatant and dehydrated water cake are obtained. The supernatant is discharged to the sludge membrane composite PN / A-MABR unit, and the dehydrated water cake can enter the sludge disposal unit for further treatment and disposal;

[0036] (7) The supernatant of sludge digestion is treated by the mud-membrane composite PN / A-MABR unit to obtain denitrified wastewater, which is discharged to the pure membrane PN / A-MABR unit;

[0037] The supernatant of high-ammonia-nitrogen sludge digestion undergoes Anammox autotrophic denitrification in the mud-membrane composite PN / A-MABR unit; AOB is attached to the aerobic area on the surface of the second hydrophobic breathable membrane in the form of a biofilm, and AnAOB exists in the anoxic liquid phase in the form of Anammox granular sludge; AOB and AnAOB are each in a suitable ecological niche, achieving efficient and low-consumption denitrification of the supernatant of high-ammonia-nitrogen sludge digestion, and the effluent of the side-stream mud-membrane composite PN / A-MABR unit is discharged to the mainstream pure membrane PN / A unit.

[0038] The nitrogen metabolism process of the mud-film composite PN / A-MABR unit is as follows: in the MABR, there is a heterogeneous mass transfer feature, O2 enters the biofilm from the membrane cavity, and is transferred from the inner layer of the biofilm to the outer layer of the biofilm, NH4 + The AOB in the biofilm uses the O2 provided by the second hydrophobic and breathable membrane as an electron acceptor to diffuse the NH4 + Oxidized to NO2 - ; NO2 produced - Diffusion from the biofilm into the liquid phase, and combined with the residual NH4 + Under the action of AnAOB, it is converted into N2 and a small amount of NO3 - , completing the autotrophic denitrification process of nitrogen-containing sewage. AOB mainly grows in aerobic biofilms, and AnAOB mainly exists in anoxic liquid phases, which effectively alleviates the contradiction between the two in the regulation of DO ecological factors. At the same time, it can avoid the problem of limited matrix mass transfer caused by excessively thick biofilms in pure membrane PN / A-MABR and the loss of AnAOB caused by biofilm shedding. The specific working process is:

[0039] (1) Inoculate the mud membrane composite PN / A-MABR with traditional nitrification and denitrification activated sludge, control the sludge concentration to 2000-4000 mg / L, and use the sequencing batch method to carry out biofilm cultivation of hydrophobic breathable membrane; pump nitrogen-containing sewage (sludge digestion supernatant) from the inlet tank into the mud membrane composite PN / A-MABR, stop the water inlet after it is full (turn off the inlet pump), turn on the aeration pump to blow air into the second MABR membrane assembly (control the aeration pressure to 10-30 kPa), and turn on the internal reflux pump to circulate the sewage in the mud membrane composite PN / A-MABR (the flow rate of the internal reflux pump is adjusted according to the actual operating conditions); take water samples regularly to measure the NH4 + When the concentration is lower than 20 mg N / L, the aeration pump and the internal reflux pump stop working, and the supernatant is discharged to the outlet tank after the sludge settles. The above operation is repeated again to accelerate the biofilm culture of microorganisms on the surface of the hydrophobic breathable membrane.

[0040] (2) When obvious microorganisms are observed to be attached and growing on the surface of the hydrophobic breathable membrane, the sludge in the PN / A-MABR composite membrane is drained and the system starts to operate in a continuous inlet and outlet mode with an internal recirculation ratio of 3 to 10. The gas flow meter and tail gas regulating valve are adjusted to achieve low-pressure aeration (the pressure gauge displays a value of 0 to 10 kPa), and NOB suppression washing is performed to start the short-range nitrification system.

[0041] (3) NH4 in the PN / A-MABR composite mud membrane + The concentration is less than 30-50 mg N / L (it is recommended to be modified to: less than 50, preferably less than 30), and the nitrite accumulation rate [NAR; NAR = NO2 - -N / (NO2 - -N+ NO3 - -N)] reaches more than 90%, inoculating AnAOB into the mud-film composite PN / A-MABR to complete the construction of the mud-film composite PN / A-MABR process; the AnAOB is inoculated in the form of Anammox granular sludge;

[0042] (4) During the operation of the PN / A-MABR composite mud film, the gas flow meter and the tail gas regulating valve are adjusted according to the DO value on the DO meter to control the aeration pressure (0-10 kPa), so that the PN / A-MABR composite mud film biofilm is controlled to be an aerobic environment and the liquid phase is controlled to be an anoxic environment (DO < 0.05 mg / L). In this way, the ecological niche distribution of AOB and AnAOB is regulated so that AOB is mainly enriched in the aerobic biofilm and AnAOB is mainly present in the anoxic liquid phase; NH4 + First oxidized to NO2 under the action of AOB - , NO2 -and the remaining NH4 + It is converted into N2 under the action of AnAOB, and the low-energy denitrification of nitrogen-containing wastewater is achieved through the synergistic denitrification of AOB and AnAOB; the purified water is discharged from the outlet to the outlet tank.

[0043] The energy self-sufficient urban sewage treatment system and method of the present invention has the following beneficial effects:

[0044] (1) Using carbon capture technology to achieve carbon redirection in sewage treatment and tap into the organic chemical energy in sewage will help sewage treatment plants approach the goal of energy self-sufficiency;

[0045] (2) MABR is used to supply oxygen to the biological treatment system, with high oxygen mass transfer efficiency and low aeration energy consumption;

[0046] (3) Using the PN / A autotrophic denitrification process to denitrify mainstream and sidestream wastewater can significantly reduce aeration energy consumption, carbon source consumption, excess sludge production and greenhouse gas emissions;

[0047] (4) Coupling MABR with PN / A denitrification process can fully combine the advantages of both processes to improve the quality and efficiency of biological denitrification of sewage.

[0048] In the energy-self-sufficient urban sewage treatment system of the present invention, the mainstream urban sewage passes through the carbon capture unit, the pure membrane PN / A-MABR unit, the deep denitrification unit and the tertiary treatment unit in sequence to complete the removal of pollutants such as carbon, nitrogen and phosphorus, and then the tail water is discharged in compliance with the standards; the supernatant of the side stream sludge digestion completes the Anammox autotrophic denitrification in the mud membrane composite PN / A-MABR unit, and the effluent enters the pure membrane PN / A-MABR unit. The present invention organically combines various process units to achieve low-carbon and high-efficiency pollution removal of mainstream and side stream sewage, and has universal engineering application value. The present invention is scientifically and rationally designed and is a sewage treatment system that can be widely applied to current and future sewage treatment plants.

[0049] Various terms and phrases used herein have the general meanings that are well known to those skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1: Schematic diagram of the structure of an energy-self-sufficient urban sewage treatment system, wherein: 1-carbon capture unit, 2-pure membrane PN / A-MABR unit, 3-deep denitrification unit, 4-tertiary treatment unit, 5-anaerobic digestion unit, 6-sludge dewatering unit, 7-sludge membrane composite PN / A-MABR unit, 8-high-load activated sludge reaction tank, 9-first and second sedimentation tanks, 10-first sludge return unit, 11-first excess sludge discharge unit, 12-first MABR membrane assembly, 13-first hydrophobic breathable membrane, 14-denitrification biochemical tank, 15-second and second sedimentation tank, 16-anoxic tank, 17-aerobic tank, 18-nitrification liquid return unit, 19-second sludge return unit, 20-second excess sludge discharge unit, 21-methane collection and utilization unit, 22-sludge disposal unit, 23-second MABR membrane assembly, 24-second hydrophobic breathable membrane, 25-Anammox granular sludge. The arrows in the figure indicate the flow direction of sewage or sludge.

[0051] Figure 2 : Schematic diagram of the structure of the mud-membrane composite PN / A-MABR unit.

[0052] Among them, 26-water inlet tank, 27-water inlet pump, 28-mud membrane composite PN / A-MABR, 29-water outlet tank, 30-internal reflux pump, 31-aeration pump, 32-gas flow meter, 33-pressure gauge, 23-second MABR membrane assembly, 35-DO measuring instrument, 36-DO sensor, 37-water inlet, 38-water outlet, 39-internal reflux port, 24-second hydrophobic breathable membrane, 40-air inlet, 41-air outlet, 42-exhaust gas regulating valve. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with the embodiments. However, the scope of the present invention is not limited to the following embodiments. It will be appreciated by those skilled in the art that various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention.

[0054] The devices involved in the present invention, such as high-load activated sludge process reaction tank, secondary sedimentation tank, sludge return unit, sludge discharge unit, hydrophobic breathable membrane, denitrification biochemical tank, anoxic tank, aerobic tank, coagulation sedimentation tank, V-type filter, ultraviolet disinfection channel, methane collection and utilization unit, etc., unless otherwise specified, are all existing devices or equipment in the prior art, and their composition structure and working principle are all prior art, and the present invention will not elaborate on this.

[0055] Example 1

[0056] An energy-self-sufficient urban sewage treatment system, such as Figure 1As shown, it includes a carbon capture unit 1, a pure membrane PN / A-MABR unit 2, a deep denitrification unit 3, a tertiary treatment unit 4, an anaerobic digestion unit 5, a sludge dehydration unit 6 and a mud-membrane composite PN / A-MABR unit 7; wherein the carbon capture unit 1, the pure membrane PN / A-MABR unit 2, the deep denitrification unit 3 and the tertiary treatment unit 4 are connected in sequence; the anaerobic digestion unit 5 is respectively connected to the carbon capture unit 1 (through the first excess sludge discharge unit 11) and the deep denitrification unit 3 (through the second excess sludge discharge unit 20); the anaerobic digestion unit 5, the sludge dehydration unit 6, the mud-membrane composite PN / A-MABR unit 7 and the pure membrane PN / A-MABR unit 2 are connected in sequence;

[0057] The pure membrane PN / A-MABR unit 2 is provided with a plurality of first MABR membrane modules 12 composed of first hydrophobic breathable membranes 13;

[0058] The structure of the mud membrane composite PN / A-MABR unit 7 is detailed in Example 3.

[0059] Example 2

[0060] The method for treating sewage using the energy self-sufficient urban sewage treatment system of Example 1 comprises the following steps:

[0061] (1) The sewage enters the carbon capture unit 1, and after being treated by the carbon capture unit 1, low-carbon nitrogen-containing sewage and carbon-rich sludge are obtained; the low-carbon nitrogen-containing sewage is discharged to the pure membrane PN / A-MABR unit 2, and the carbon-rich sludge is discharged to the anaerobic digestion unit 5;

[0062] (2) After the low-carbon nitrogen-containing sewage is treated by the pure membrane PN / A-MABR unit 2, the initial denitrification sewage is obtained and discharged to the deep denitrification unit 3;

[0063] (3) After the initial denitrification wastewater is treated in the deep denitrification unit 3, deep denitrification wastewater and sludge are obtained. The deep denitrification wastewater is discharged to the tertiary treatment unit 4, and the sludge is discharged to the anaerobic digestion unit 5;

[0064] (4) After the deep denitrification wastewater is treated in the tertiary treatment unit 4, the reclaimed water is obtained, and the reclaimed water is reused or discharged to the corresponding receiving water body;

[0065] (5) After the sludge is treated by the anaerobic digestion unit 5, a sludge-water mixture is obtained and discharged to the sludge dehydration unit 6; the generated methane gas can be used for power generation through the methane collection and utilization unit 21, thereby realizing resource utilization while reducing the amount of sludge;

[0066] (6) After the sludge-water mixture is treated by the sludge dehydration unit 6, sludge digestion supernatant and dehydrated water cake are obtained. The supernatant is discharged to the sludge membrane composite PN / A-MABR unit 7, and the dehydrated water cake can enter the sludge disposal unit 22 for further treatment and disposal;

[0067] (7) The supernatant of sludge digestion is treated by the mud-membrane composite PN / A-MABR unit 7 to obtain denitrified water, which is discharged to the pure membrane PN / A-MABR unit 2.

[0068] The carbon capture unit 1 is composed of a high-load activated sludge reaction tank 8 and a first secondary sedimentation tank 9 connected to the high-load activated sludge reaction tank 8 (the bottom of the first secondary sedimentation tank 9 is also connected to the high-load activated sludge reaction tank 8 through a first sludge return unit 10). Organic matter in urban sewage is captured in the high-load activated sludge reaction tank 8, with an MLSS of 5000 mg / L, an HRT of 20 to 30 min, and a sludge retention time (SRT) of 3 to 5 d. About 65% of the organic matter in the influent can be removed in the high-load activated sludge reaction tank 8. The effluent of the high-load activated sludge reaction tank 8 enters the first secondary sedimentation tank 9 for mud-water separation, with an HRT of 1 h. The effluent of the first secondary sedimentation tank 9 enters the pure membrane PN / A-MABR unit 2, and a portion of the bottom concentrated sludge is returned to the high-load activated sludge reaction tank 8 through the first sludge return unit 10, and the remaining concentrated sludge enters the anaerobic digestion unit 5 through the first residual sludge discharge unit 11.

[0069] The pure membrane PN / A-MABR unit 2 is mainly used to treat NH4 + and TN, and can further remove residual organic matter in the effluent of the carbon capture unit 1. The first hydrophobic breathable membrane 13 is in the form of a hollow fiber, and the packing density of the membrane area is 150-200 m 2 / m 3 The HRT of pure membrane PN / A-MABR unit 2 is 6-8 h, the liquid phase DO is less than 0.05 mg / L, and the biofilm thickness on the first hydrophobic breathable membrane 13 is 400-800 μm. This unit can remove about 10% of organic matter and 90% of NH4 + and 75% of TN, of which 93.5% was removed by the Anammox autotrophic denitrification pathway and 6.5% by denitrification heterotrophic denitrification.

[0070] The deep denitrification unit 3 is composed of a denitrification biochemical tank 14 and a second secondary sedimentation tank 15 connected to the denitrification biochemical tank 14 (the bottom of the second secondary sedimentation tank 15 is also connected to the anoxic tank 16 of the denitrification biochemical tank 14 through a second sludge return unit 19), wherein the denitrification biochemical tank 14 is composed of an anoxic tank 16 and an aerobic tank 17 connected to the anoxic tank 16 (the bottom of the aerobic tank 17 is also connected to the anoxic tank 16 through a nitrification liquid return unit 18), MLSS is 2000-3000 mg / L, HRT is 1-2 h, and SRT is 10-15d. In the anoxic tank 16, DO <0.05 mg / L, denitrifying bacteria use external carbon sources (such as sodium acetate) / microorganisms Internal carbon source to remove about 10% of TN in the influent; in the aerobic tank 17, DO is 1-3 mg / L, and nitrifying bacteria further oxidize residual NH4 + -N, the removal rate is 5% to 10%. A part of the mud-water mixture at the end of the aerobic tank 17 enters the anoxic tank 16 through the nitrification liquid return unit 18, and the remaining mud-water mixture enters the second secondary sedimentation tank 15 for mud-water separation. The HRT of the second secondary sedimentation tank 15 is 1 h. The supernatant after mud-water separation enters the tertiary treatment unit 4, and a part of the concentrated sludge is returned to the anoxic tank 16 through the second sludge return unit 19, and the remaining concentrated sludge enters the anaerobic digestion unit 5 through the second residual sludge discharge unit 20.

[0071] The tertiary treatment unit 4 mainly involves conventional deep treatment, which consists of a coagulation sedimentation tank, a V-type filter tank and an ultraviolet disinfection channel connected in sequence, to achieve the removal of pollutants such as phosphorus, suspended solids, pathogenic bacteria, etc. The removal rate of phosphorus in the influent can reach 98%, the removal rate of suspended solids can reach more than 90%, and the effluent E. coli is within the standard range.

[0072] The anaerobic digestion unit 5 mainly receives the activated sludge from the carbon capture unit 1 and the deep denitrification unit 3. The medium-temperature anaerobic fermentation is adopted, the temperature is controlled at about 30°C, and the SRT is 15-20 days. The external carbon source adsorbed by the sludge and the internal carbon source of the microorganisms are fully anaerobically decomposed and methane is produced. The methane enters the methane collection and utilization unit 21 for efficient recovery and energy conversion.

[0073] The sludge dehydration unit 6 uses a centrifugal dehydrator to separate the digested liquid and sludge in the digested sludge, and the dehydration performance of the digested sludge is improved by adding polyacrylamide, and the moisture content is reduced from 95% to 65%.

[0074] The sludge membrane composite PN / A-MABR unit 7 realizes autotrophic denitrification of the sludge digestion supernatant by the Anammox process. The second hydrophobic breathable membrane 24 is in the form of hollow fibers, and the packing density of the membrane area is 100-150 m 2 / m 3, DO in the liquid phase is less than 0.05 mg / L, HRT is 8-10 h, the biofilm thickness on the second hydrophobic breathable membrane 24 is 300-500 μm, and the Anammox granular sludge MLSS is 6000-7000 mg / L. Through process control optimization, 80%-85% TN removal in the sludge digestion supernatant can be achieved. The effluent of the mud-membrane composite PN / A-MABR unit 7 is returned to the pure membrane PN / A-MABR unit 2.

[0075] Through the above-mentioned energy-self-sufficient urban sewage treatment system, efficient and low-carbon denitrification effect of urban sewage can be achieved, and the effluent water quality meets the Level A standard of "Pollutant Emission Standard for Urban Sewage Treatment Plants" GB18918-2002.

[0076] Example 3

[0077] Mud membrane composite PN / A-MABR unit, such as Figure 2 As shown, it includes a mud-film composite PN / A-MABR 28, a water inlet tank 26, a water outlet tank 29, an internal reflux pump 30, an aeration pump 31, a DO meter 35 and a DO sensor 36; wherein,

[0078] The mud membrane composite PN / A-MABR28 is provided with a water inlet 37, a water outlet 38 and two internal reflux ports 39, the water inlet 37 is connected to the water inlet tank 26 via a water inlet pump 27, the water outlet 38 is connected to the water outlet tank 29, and the two internal reflux ports 39 are connected via an internal reflux pump 30;

[0079] The mud-membrane composite PN / A-MABR 28 is provided with a second MABR membrane assembly 23; the second MABR membrane assembly 23 is composed of a plurality of second hydrophobic breathable membranes 24 (the second hydrophobic breathable membranes 24 are hollow fiber membranes, and the packing density of the membrane area is 120 m 2 / m 3 ,), the second MABR membrane assembly 23 is provided with an air inlet 40 and an air outlet 41, the air inlet 40 is connected to the aeration pump 31, and a gas flow meter 32 and a pressure gauge 33 are provided on the connecting pipeline; the air outlet 41 can discharge the gas to the outside of the PN / A-MABR28, and a tail gas regulating valve 42 is installed on the pipeline connected to the air outlet 41;

[0080] The DO sensor 36 is placed in the mud membrane composite PN / A-MABR28 and connected to the DO measuring instrument 35.

[0081] The operation process of the MABR-based mud membrane composite high-efficiency autotrophic denitrification system is as follows: nitrogen-containing sewage is pumped into the mud membrane composite PN / A-MABR28 from the water inlet tank 26 through the water inlet pump 27; air is blown into the second MABR membrane assembly 23 through the aeration pump 31, and oxygen is supplied to the mud membrane composite PN / A-MABR28 through the second hydrophobic breathable membrane 24 of the hollow fiber, and the aeration pressure is jointly adjusted by the gas flow meter 32 and the tail gas regulating valve 42, and the aeration pressure value is displayed by the pressure gauge 33; the internal reflux pump 30 realizes the circulation of sewage in the PN / A-MABR28; the purified water flows from the outlet 38 to the outlet tank 29.

[0082] The method for treating sewage using a mud-membrane composite PN / A-MABR unit is as follows:

[0083] (1) The residual activated sludge from a certain city sewage treatment plant was inoculated into the PN / A-MABR28, so that the sludge concentration in the PN / A-MABR28 was about 3000 mg / L; the nitrogen-containing sewage (sludge digestion supernatant) was pumped into the PN / A-MABR28 from the inlet tank 26, and the PN / A-MABR28 was operated in a batch mode, that is, a non-continuous water inlet and outlet mode; after the water inlet was completed, the inlet pump 27 was turned off, and the internal reflux pump 30 was turned on to allow the sewage to circulate in the PN / A-MABR28, and the aeration pump 31 was turned on and the gas flow meter 32 and the tail gas regulating valve 42 were adjusted. The pressure gauge showed an aeration pressure of 20 kPa. Water samples were taken regularly to detect the NH4 + When the concentration is lower than 20 mgN / L, the aeration pump 31 and the internal reflux pump 30 are stopped, and the supernatant is discharged to the water outlet tank 29 after the sludge settles, and the above steps are repeated again to accelerate the biofilm culture of nitrifying bacteria on the surface of the second hydrophobic breathable membrane 24.

[0084] (2) After 6 days, it was observed that there were obvious microorganisms attached and growing on the surface of the second hydrophobic breathable membrane 24. The activated sludge in the sludge-membrane composite PN / A-MABR28 was emptied and the continuous water inlet and outlet mode was started, that is, the water inlet pump 27, the internal reflow pump 30, and the aeration pump 31 were all in the normally open state. The HRT was 4 to 6 h, the internal reflow ratio was 10, and the biofilm thickness on the surface of the second hydrophobic breathable membrane 24 was 300 to 500 μm. Low-pressure aeration was used throughout the process, and the aeration pressure was 10 kPa.

[0085] (3) After 30 days of operation, the effluent NH4 of the mud membrane composite PN / A-MABR28 +The concentration was less than 30 mg N / L, and the NAR was greater than 90%. The mature Anammox granular sludge was inoculated into the mud-membrane composite PN / A-MABR28, and the sludge concentration was 6000 mg / L to complete the construction of the mud-membrane hybrid PN / A-MABR process.

[0086] (4) During the operation of the mud membrane hybrid PN / A-MABR, the gas flow meter 32 and the tail gas regulating valve 42 are adjusted according to the DO value on the DO measuring instrument 35 to control the oxygen supply, and the biofilm in the MABR system is controlled to be an aerobic environment, the liquid phase is an anoxic environment, and the DO in the liquid phase is 0.02 mg / L. At this stage, the HRT of the mud membrane composite PN / A-MABR28 is 3 to 5 h. Deep denitrification of urban sewage is achieved through the collaborative cooperation of AOB and AnAOB.

[0087] Nitrogen conversion process during operation: NH4 in the influent + First oxidized to NO2 under the action of AOB - , NO2 - and the remaining NH4 + It is converted into N2 under the action of AnAOB, and the low-energy denitrification of nitrogen-containing wastewater is achieved through the synergistic denitrification of AOB and AnAOB.

[0088] The distribution characteristics of functional bacteria during operation are as follows: AOB is mainly attached to the biofilm on the surface of the second hydrophobic breathable membrane 24, and AnAOB is mainly present in the form of granular sludge in the liquid phase.

[0089] The above-mentioned MABR-based mud membrane composite high-efficiency autotrophic nitrogen removal system is used to treat the influent NH4 + The effluent quality after treatment can be stabilized at NH+ 4-N: 15.0±3.5 mg / L, TN: 120.5±12.4 mg / L.

[0090] The above examples are provided to those skilled in the art to fully disclose and describe how to make and use the claimed embodiments, and are not intended to limit the scope of the disclosure herein. Modifications that are obvious to those skilled in the art will fall within the scope of the appended claims.

Claims

1. An energy-self-sufficient urban sewage treatment system, characterized by: It includes a carbon capture unit, a pure membrane PN / A-MABR unit, a deep denitrification unit, a tertiary treatment unit, an anaerobic digestion unit, a sludge dehydration unit and a mud-membrane composite PN / A-MABR unit; wherein the carbon capture unit, the pure membrane PN / A-MABR unit, the deep denitrification unit and the tertiary treatment unit are connected in sequence; the anaerobic digestion unit is connected to the carbon capture unit and the deep denitrification unit respectively; the anaerobic digestion unit, the sludge dehydration unit, the mud-membrane composite PN / A-MABR unit and the pure membrane PN / A-MABR unit are connected in sequence; the anaerobic digestion unit is connected to a methane collection and utilization unit; the anaerobic digestion unit is connected to the carbon capture unit through a first residual sludge discharge unit; the anaerobic digestion unit is connected to the deep denitrification unit through a second residual sludge discharge unit.

2. The energy self-sufficient urban sewage treatment system according to claim 1 is characterized in that: The structure of the mud membrane composite PN / A-MABR unit is as follows: it includes a mud membrane composite PN / A-MABR, a water inlet tank, a water outlet tank, an internal reflux pump, an aeration pump, a DO meter and a DO sensor; wherein, The mud membrane composite PN / A-MABR is provided with a water inlet, a water outlet and two internal reflux ports, the water inlet is connected to the water inlet tank, the water outlet is connected to the water outlet tank, and the two internal reflux ports are connected through an internal reflux pump; The mud-membrane composite PN / A-MABR is provided with a second MABR membrane assembly; the second MABR membrane assembly is composed of a plurality of second hydrophobic breathable membranes, the second MABR membrane assembly is provided with an air inlet and an air outlet, and the air inlet is connected to an aeration pump; The DO sensor is placed in the mud membrane composite PN / A-MABR and connected to the DO measuring instrument.

3. The energy self-sufficient urban sewage treatment system according to claim 2 is characterized in that: The water inlet is connected to the water inlet tank via a water inlet pump; Or: a gas flow meter and a pressure gauge are provided on the connecting pipeline between the air inlet and the aeration pump; Or: an exhaust gas regulating valve is provided on the pipeline connected to the gas outlet; Or: the second hydrophobic breathable membrane is any one of a hollow fiber membrane, a plate membrane, a roll membrane, and a tubular membrane.

4. The energy self-sufficient urban sewage treatment system according to claim 1 is characterized in that: The carbon capture unit consists of a high-load activated sludge process reaction tank and a first and second sedimentation tank connected to the high-load activated sludge process reaction tank.

5. The energy self-sufficient urban sewage treatment system according to claim 1 is characterized in that: The pure membrane type PN / A-MABR unit is provided with a plurality of first MABR membrane modules composed of first hydrophobic breathable membranes; the first hydrophobic breathable membranes are in the form of hollow fibers, plate membranes or roll membranes.

6. The energy self-sufficient urban sewage treatment system according to claim 1 is characterized in that: The deep denitrification unit is composed of a denitrification biochemical pool and a second secondary sedimentation pool connected to the denitrification biochemical pool, wherein the denitrification biochemical pool is composed of an anoxic pool and an aerobic pool connected to the anoxic pool.

7. The energy self-sufficient urban sewage treatment system according to claim 1 is characterized by: The three-stage treatment unit consists of a coagulation sedimentation tank, a V-type filter tank and an ultraviolet disinfection channel connected in sequence; Or: the sludge dewatering unit is connected to the sludge disposal unit.

8. Use of the energy self-sufficient urban sewage treatment system according to any one of claims 1 to 7 in treating urban sewage.

9. A method for treating sewage using the energy self-sufficient urban sewage treatment system according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) The sewage enters the carbon capture unit and is treated by the carbon capture unit to obtain low-carbon nitrogen-containing sewage and carbon-rich sludge; the low-carbon nitrogen-containing sewage is discharged to the pure membrane PN / A-MABR unit, and the carbon-rich sludge is discharged to the anaerobic digestion unit; (2) After the low-carbon nitrogen-containing sewage is treated by the pure membrane PN / A-MABR unit, the initial denitrification sewage is obtained and discharged to the deep denitrification unit; (3) After the initial denitrification wastewater is treated in the deep denitrification unit, deep denitrification wastewater and sludge are obtained. The deep denitrification wastewater is discharged to the tertiary treatment unit, and the sludge is discharged to the anaerobic digestion unit; (4) After the deep denitrification wastewater is treated in the tertiary treatment unit, it is converted into reclaimed water; (5) After the sludge is treated in the anaerobic digestion unit, a sludge-water mixture is obtained and discharged to the sludge dewatering unit; (6) After the sludge-water mixture is treated by the sludge dehydration unit, the sludge digestion supernatant and dehydrated water cake are obtained, and the supernatant is discharged to the sludge-membrane composite PN / A-MABR unit; (7) The supernatant of sludge digestion is treated by the mud-membrane composite PN / A-MABR unit to obtain denitrified wastewater, which is discharged to the pure membrane PN / A-MABR unit.

10. The method for treating sewage according to claim 9, characterized in that: The process of treating sewage by the mud-membrane composite PN / A-MABR unit is as follows: (1) Inoculate the mud-membrane composite PN / A-MABR with traditional nitrification and denitrification activated sludge, and use the sequencing batch method to cultivate the hydrophobic breathable membrane; pump the nitrogen-containing sewage or sludge digestion supernatant from the water inlet tank into the mud-membrane composite PN / A-MABR, stop the water inlet after it is full, start the aeration pump to blow air into the second MABR membrane module, and start the internal reflux pump to circulate the sewage in the mud-membrane composite PN / A-MABR; take water samples regularly to determine the NH4 + When the concentration is lower than 20 mg N / L, the aeration pump and the internal reflux pump stop working, and the supernatant is discharged to the outlet tank after the sludge settles. The above operation is repeated again to accelerate the biofilm culture of microorganisms on the surface of the hydrophobic breathable membrane. (2) When obvious microorganisms are observed to be attached and growing on the surface of the hydrophobic breathable membrane, the sludge in the PN / A-MABR composite membrane is drained and the system starts to operate in a continuous water inlet and outlet mode with an internal recirculation ratio of 3 to 10. The gas flow meter and tail gas regulating valve are adjusted to achieve low-pressure aeration, NOB suppression washing is performed, and the short-range nitrification system is started. (3) NH4 in the PN / A-MABR composite mud membrane + When the concentration of nitrite is less than 50 mg N / L and the nitrite accumulation rate reaches more than 90%, AnAOB is inoculated into the sludge membrane composite PN / A-MABR to complete the construction of the sludge membrane composite PN / A-MABR process; the AnAOB is inoculated in the form of Anammox granular sludge; (4) During the operation of the PN / A-MABR composite mud film, the gas flow meter and the tail gas regulating valve are adjusted according to the DO value on the DO meter to control the aeration pressure, so that the PN / A-MABR composite mud film biofilm is controlled to be an aerobic environment and the liquid phase is controlled to be an anoxic environment. In this way, the ecological niche distribution of AOB and AnAOB is regulated so that AOB is mainly enriched in the aerobic biofilm and AnAOB is mainly present in the anoxic liquid phase. The NH4 + First oxidized to NO2 under the action of AOB - , NO2 - and the remaining NH4 + It is converted into N2 under the action of AnAOB, and the low-energy denitrification of nitrogen-containing wastewater is achieved through the synergistic denitrification of AOB and AnAOB; the purified water is discharged from the outlet to the outlet tank.

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