A / O coupling magnetic flocculation system for rapidly treating urban overflow sewage and operation method of A / O coupling magnetic flocculation system

Abstract

The invention relates to the field of sewage treatment, in particular to an A / O coupling magnetic flocculation system for rapidly treating urban overflow sewage and an operation method thereof, the system comprises an A / O biological treatment system and a magnetic flocculation treatment system; the A / O biological treatment system comprises an anoxic tank, an aerobic tank and a sedimentation tank; the magnetic flocculation treatment system comprises a magnetic seed feeding system, a flocculation agent feeding system, a magnetic flocculation reaction system and a magnetic seed recovery system; the magnetic flocculation reaction system comprises a rapid flocculation reaction tank and a rapid sedimentation tank; wherein the working volume ratio of the anoxic tank to the aerobic tank to the rapid flocculation reaction tank to the rapid sedimentation tank is (1.0-1.5): (5.0-7.0): (0.2-0.3): (0.2-0.3). The method has the advantages that A / O biological treatment and magnetic flocculation are coupled, and the removal performance of nitrogen, phosphorus, organic matters and suspended matters is synchronously enhanced; the biological availability of effluent organic matters is improved, the sewage is oxygenated, and the risk of overflow pollution caused by direct discharge into a river in traditional rapid treatment is reduced.

Description

Technical Field

[0001] The invention relates to the field of water pollution treatment, and in particular to an A / O coupling magnetic flocculation system for rapidly treating urban overflow sewage and an operation method thereof. Background Art

[0002] As the pace of urbanization continues, urban space has expanded significantly, and with it the city's impervious coverage has expanded dramatically. This phenomenon is particularly prominent in rainy weather, because the increase in impervious area makes it difficult for rainwater to penetrate naturally, and instead forms large-scale runoff. Especially during the rainy season or rainstorm period, this runoff effect is significantly enhanced, posing a severe challenge to the drainage capacity of urban drainage networks and natural rivers. The problem is particularly difficult in old urban areas or areas where drainage infrastructure is relatively backward. These areas often face the dilemma of being unable to discharge rainwater in a timely manner, resulting in serious road waterlogging, that is, frequent urban waterlogging. Combined sewer overflow pollution is formed through the combined rainwater and sewage pipe network. When the amount of rainwater exceeds the carrying capacity of the drainage system, overflow will occur. This is not limited to the rainwater itself, but may also carry and mix with untreated sewage to form combined sewer overflow (CSO). This mixed sewage is directly discharged into the water body without treatment, which greatly aggravates the pollution level of the receiving water body and is one of the important sources of the black and smelly problem of urban rivers.

[0003] Therefore, the current focus of urban water environment management has shifted to how to effectively control and reduce the overflow pollution of initial rainwater. By optimizing the design of drainage systems, enhancing rainwater collection and treatment capabilities, and promoting green infrastructure such as permeable pavement and rain gardens, we strive to alleviate urban waterlogging problems at the source, protect urban water bodies from pollution, and promote sustainable urban development.

[0004] Urban initial rainwater and the CSO problems it causes contain a wealth of pollutants such as suspended particulate matter (SS), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP). If discharged into natural water bodies without effective treatment, it will inevitably lead to increased water pollution and pose a potential threat to the balance of aquatic ecosystems and human health. Given that overflow pollution often comes with sudden rainfall, it exhibits characteristics such as intermittency, unpredictability and instantaneous increase in emissions, which greatly increase the complexity and challenge of urban runoff pollution control. In view of the above dilemma, the development of an overflow sewage purification technology that is both efficient, economically feasible and environmentally friendly has become an important issue that needs to be solved urgently. This technology needs to be able to flexibly respond to the uncertainty of pollution emissions, ensure rapid response when pollution incidents occur, effectively intercept and remove pollutants, thereby protecting the urban water environment from harm and promoting the dual sustainable development of ecology and economy.

[0005] In recent years, magnetic flocculation technology has been widely used in the field of sewage treatment. The core of this technology is to integrate magnetic seeds into the traditional flocculation process, and use mechanisms such as charge neutralization, adsorption bridging, compression of double electric layers and net capture effect to promote the close combination of magnetic seeds, flocculants and tiny colloidal particles in the water body to form a heavy and tightly structured magnetic composite flocs. Under natural gravity sedimentation or induction of an external magnetic field, these flocs can be quickly and effectively separated from the water body, significantly removing pollutants such as phosphorus and suspended impurities. However, it is not capable of removing pollutants such as dissolved nitrogen and organic matter. In contrast, biological treatment technology has efficient and stable nitrogen and organic matter removal performance, but is not capable of removing high suspended matter and phosphorus.

[0006] At present, traditional flocculation technology has shortcomings in the treatment of overflow pollution during flood season, such as low treatment load of suspended solids, organic matter, nitrogen and phosphorus, slow startup and poor impact resistance. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art, and to provide an A / O coupled magnetic flocculation system and its operation method for rapid treatment of urban overflow sewage, which couples A / O biological treatment and magnetic flocculation to form a biological treatment coupled magnetic flocculation system for rapid treatment of overflow pollution, and utilizes the efficient degradation of pollutants such as organic matter and nitrogen by biological treatment technology and the ability of magnetic flocculation technology to rapidly separate pollutants such as phosphorus and suspended matter, fully combining the two organically, and simultaneously enhancing the removal performance of nitrogen, phosphorus, organic matter and suspended matter; improving the bioavailability of effluent organic matter, and oxygenating sewage, reducing the risk of overflow pollution caused by traditional rapid treatment and direct discharge into the river. The operation method of the present invention also effectively improves the efficiency of overflow sewage treatment, greatly shortens the time required for treatment, and realizes rapid and efficient treatment of overflow sewage.

[0008] The present invention is implemented through the following technical solutions: On the one hand, an A / O coupled magnetic flocculation system for rapidly treating urban overflow sewage is provided, the system comprising an A / O biological treatment system and a magnetic flocculation treatment system;

[0009] The A / O biological treatment system includes an anoxic tank, an aerobic tank and a sedimentation tank;

[0010] The magnetic flocculation treatment system includes a magnetic seed dosing system, a flocculation agent dosing system, a magnetic flocculation reaction system and a magnetic seed recovery system; and the magnetic flocculation reaction system includes a rapid flocculation reaction tank and a rapid sedimentation tank;

[0011] Wherein, the working volume ratio of the anoxic tank: the aerobic tank: the rapid flocculation reaction tank: the rapid sedimentation tank is 1.0-1.5: 5.0-7.0: 0.2-0.3: 0.2-0.3.

[0012] Through the above technical solutions, biological treatment technology focuses on the effective removal of ammonia nitrogen and organic pollutants, and magnetic flocculation technology is supplemented by its excellent phosphorus removal and suspended solids purification capabilities. The two work together to successfully build a new urban overflow sewage rapid treatment model that integrates biological technology and magnetic flocculation technology; especially in the efficient removal of organic matter, nitrogen, phosphorus and suspended solids, achieving comprehensive compliance with effluent water quality standards, and significantly reducing the pollution load on natural rivers. Significant progress has been made; through the coupling of A / O and magnetic flocculation processes and determining the optimal treatment time for rapid treatment of urban overflow sewage, through A / O kinetic experiments, the optimal anoxic and aerobic treatment times are determined to be 10 minutes for anoxic, 60 minutes for aerobic, and 10 minutes for sedimentation. While the magnetic flocculation process, under the premise of achieving the same treatment effect, has the shortest treatment time of rapid stirring (350r / min) 2 minutes, sedimentation time 2 minutes, and the total treatment time of magnetic flocculation is 4 minutes. The entire process only takes 84 minutes to achieve rapid treatment of urban overflow sewage. The present invention not only verifies the feasibility of the biological treatment and magnetic flocculation coupling technology in practical applications, but also provides a solution to the combined sewer overflow pollution problem.

[0013] Furthermore, the sludge age of the A / O biological treatment system is 10-12 days, and the sludge return ratio is 0.4-0.5. If the sludge age is too short, the nitrifying microorganisms will be discharged from the system before they have time to reproduce, and they will not be able to form dominant microorganisms, which is not conducive to the degradation of ammonia nitrogen; while if the sludge age is too long, sludge aging will occur. In the present application, the sludge age is controlled at 10-12 days. This range means that the microorganisms in the activated sludge have enough time to grow and reproduce in the system to ensure an effective biological treatment process while avoiding sludge aging. A higher sludge return ratio can increase the sludge concentration in the aeration tank and improve the treatment efficiency, but it may also cause sludge aging. In the present application, the sludge return ratio is controlled between 0.4-0.5. This return ratio range helps to maintain the sludge concentration in the system while ensuring the sludge renewal rate to support effective biological treatment and denitrification processes.

[0014] Furthermore, the anoxic tank is used to inoculate and cultivate denitrification activated sludge, the sludge concentration is 5000±100 mg / L, and the dissolved oxygen is 0.1-0.3 mg / L;

[0015] The aerobic pool is used to inoculate and cultivate nitrification activated sludge, with a sludge concentration of 5000±100 mg / L and a dissolved oxygen of 4-6 mg / L; an appropriate sludge concentration can maintain a high biomass, increase the diversity of microorganisms, and thus improve the biological activity of the system. This helps to improve the removal efficiency of pollutants in sewage. Too low sludge concentration will result in insufficient sludge activity and fail to achieve the purpose of rapid removal of pollutants, while too high sludge concentration will result in hindered microbial growth, affecting treatment efficiency, and a large number of inactivated cells will release organic matter and nutrients, thereby deteriorating water quality.

[0016] The sedimentation tank is provided with a sludge return pipe for returning the sludge to the anoxic tank.

[0017] Furthermore, a stirring device for stirring the mixed materials is arranged on the top of the anoxic tank; and an aeration system for balancing the dissolved oxygen content is arranged on the bottom of the aerobic tank.

[0018] Furthermore, the magnetic seed dosing system and the flocculant dosing system respectively add the magnetic seed and the magnetic flocculant into the rapid reaction tank; wherein the magnetic seed is Fe3O4; and the magnetic flocculant is PAC and anionic PAM.

[0019] Furthermore, a stirring system for mixing the magnetic seed, magnetic flocculation agent and sewage is arranged on the top of the rapid reaction pool, a magnet for accelerating the sedimentation of flocs is arranged on the outside of the bottom of the rapid reaction pool, and a scraper for discharging the flocs to a mud discharge channel is arranged on the inside of the bottom of the pool.

[0020] Furthermore, the magnetic seed recovery system is composed of a magnetic mud shearing machine and a magnetic separator.

[0021] On the other hand, a method for operating the A / O coupled magnetic flocculation system for rapidly treating urban overflow sewage is provided, the method comprising the following specific steps:

[0022] Step S1, during the system startup period, 5000±100 mg / L of activated sludge from the biological treatment section of the sewage treatment plant is inoculated into the bioreactor and operated stably for a period of time to enrich the microorganisms in the pool;

[0023] Step S2, during the system operation period, the sewage in step S1 flows into the anoxic tank, is mixed with the sludge mixed liquid and the return sludge in the anoxic tank, and then denitrified by denitrifying bacteria to convert nitrate nitrogen into nitrogen gas for removal, thereby obtaining a mixed liquid;

[0024] Step S3, the mixed solution obtained in step S2 is flowed into an aerobic tank, where ammonia nitrogen is converted into nitrate nitrogen under the nitrification action of nitrifying bacteria, and organic matter is removed to obtain an aqueous solution;

[0025] Step S4, the aqueous solution obtained in step S3 flows into a sedimentation tank for mud-water separation, the supernatant of the sedimentation tank enters a rapid flocculation reaction tank, and a certain amount of PAC, magnetic seed Fe3O4 and PAM are added, and after stirring, floccules and sewage are obtained;

[0026] Step S5, the flocs obtained in step S4 and the sewage flow into the rapid sedimentation tank, the magnetic seed Fe3O4 drives the flocs to accelerate the sedimentation to the bottom of the rapid sedimentation tank, the flocs at the bottom of the rapid sedimentation tank are sent to the sludge discharge pipe, the treated sewage supernatant is discharged from the rapid sedimentation tank, and the precipitated flocs are sent to the external magnetic seed recovery system to recover the magnetic seeds.

[0027] Preferably, the hydraulic retention time of the anoxic tank is 10-20 min, the hydraulic retention time of the aerobic tank is 50-70 min, the sedimentation time of the sedimentation tank is 10-20 min, and the hydraulic retention time of the rapid flocculation reaction tank is 2-3 min.

[0028] Furthermore, in step S4, the dosage of PAC is 75-105 mg / L, the dosage of magnetic seed Fe3O4 is 10-30 mg / L, and the dosage of PAM is 0.5-3 mg / L; the stirring speed is 350 r / min.

[0029] Further, in step S5, the NH4 + The -N removal efficiency was 99.7%, COD removal efficiency was 91.3%, TP removal efficiency was 99.5%, and SS removal efficiency was 93.3%.

[0030] Beneficial Effects

[0031] 1) Couple biological treatment with magnetic flocculation to form a biological treatment coupled magnetic flocculation system for rapid treatment of overflow pollution. It utilizes the efficient degradation of pollutants such as organic matter and nitrogen by biological treatment technology and the ability of magnetic flocculation technology to quickly separate pollutants such as phosphorus and suspended solids, fully combining the two organically to simultaneously enhance the removal performance of nitrogen, phosphorus, organic matter and suspended solids.

[0032] 2) It improves the bioavailability of organic matter in the effluent and oxygenates the sewage, reducing the risk of overflow pollution caused by traditional rapid treatment and direct discharge into the river.

[0033] 3) The operation method of the present invention effectively improves the overflow sewage treatment efficiency, greatly shortens the time required for treatment, and realizes rapid and efficient treatment of overflow sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1The embodiment 1 of the present invention embodies the determination of the minimum removal time of the anoxic tank and the aerobic tank, and the determination of the time is obtained through the sequencing batch AO kinetics experiment data chart;

[0035] Figure 2 This is a process flow chart of a biotechnology-coupled magnetic flocculation system for rapid treatment of urban overflow sewage;

[0036] Figure 3 The biological technology coupling magnetic flocculation system for rapid treatment of urban overflow sewage is used to evaluate the treatment efficiency of overflow sewage with traditional biological treatment (AO). DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The experimental methods without specific conditions in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, all percentages, ratios, proportions or parts are by weight.

[0039] Unless otherwise specified, the reagents and raw materials used in the examples and comparative examples of the present invention can be obtained through commercial channels.

[0040] Example 1

[0041] A small-scale test device for rapid treatment of urban overflow sewage by biotechnology coupled magnetic flocculation system was constructed. The process flow is as follows: Figure 2 As shown. Under room temperature conditions, the collected overflow sewage is used as the inlet water. The water quality is COD = 300mg / L, total nitrogen (TN) = 70mg / L, ammonia nitrogen (NH4 +-N)=50mg / L, total phosphorus (TP)=5mg / L and turbidity=80NTU. The system includes an A / O biological treatment system and a magnetic flocculation treatment system; the A / O biological treatment system includes an anoxic tank, an aerobic tank and a sedimentation tank; the magnetic flocculation treatment system includes a magnetic seed dosing system, a flocculant dosing system, a magnetic flocculation reaction system and a magnetic seed recovery system; and the magnetic flocculation reaction system includes a rapid flocculation reaction tank and a rapid sedimentation tank; wherein, the working volume ratio of the anoxic tank: aerobic tank: rapid flocculation reaction tank: rapid sedimentation tank is 1:6:0.2:0.2. The effective volume of the anoxic tank and the aerobic tank are both 1L, separated by a perforated partition in the middle. An agitator is set inside the anaerobic tank for complete mixing; the mixed liquid in the aerobic tank flows in the reactor in a plug flow state, and an aeration system is set on the top. The initial inoculated sludge concentration of the biological treatment system is 5000±100mg / L. The speed of the agitator in the anaerobic tank is set to 200r / min, and the dissolved oxygen concentration is 0.2mg / L; the dissolved oxygen concentration in the aerobic tank is 5mg / L. The hydraulic retention time in the anoxic tank is 10min, the aerobic tank is 60min, and the sedimentation time in the sedimentation tank is 10min. The sludge age of the biological treatment system is 12 days, the sludge return ratio is 0.5, and the influent pH is controlled to be stable at 7.3.

[0042] The effective volumes of the rapid flocculation reaction tank and the rapid sedimentation tank are both 500mL. The rapid flocculation reaction tank is equipped with an agitator, and the speed is set to 350r / min. A strong magnet with a radius of 2cm and a height of 0.5cm is installed at the bottom of the rapid sedimentation tank. In the magnetic flocculation system, the dosages of PAC, Fe3O4 and PAM are 105mg / L, 30mg / L and 3mg / L, respectively. The reaction time of the rapid flocculation reaction tank is 2min, and the sedimentation time of the rapid sedimentation tank is 2min. Among them, the determination of the minimum removal time of the anoxic tank and the aerobic tank, as well as the determination of the flocculant dosage and the shortest sedimentation time of the magnetic flocculation are obtained through sequencing batch AO kinetic experiments and orthogonal optimization experiments, as follows Figure 1 As shown in the figure: The A / O process was used to treat the initial urban rainwater in anoxic and aerobic processes for 2 hours each. In the anoxic process, after 10 minutes of anoxic process, NH4 + -N removal rate was 49.8%, COD removal rate was 57.8%, and TP removal rate was 70.6%. The anoxic treatment was continued for 2 hours, and NH4 + -N and COD removal rates increased slowly, NH4 + -N removal rate increased from 49.8% to 55.9%, an increase of only 6.1%, and COD removal rate increased from 57.8% to 65.6%. After 2 hours of anoxic treatment, the effluent entered the aerobic tank and was treated aerobically for 60 minutes. NH4 + -N removal rate reached 99.1%, COD removal rate reached 89.0%, TP removal rate reached 94.9%, and then aerobic for 2h, NH4+ -N, COD and TP removal rates did not change much. The anoxic time was selected as 10 min (A10) and the aerobic treatment was 60 min (O 60 min). The treatment process did not achieve the optimal treatment effect of the two treatment units at the two points. Here, the treatment efficiency was sacrificed in exchange for the treatment time.

[0043] Table 1 Factors and levels in Taguchi orthogonal experiment

[0044]

[0045] Note: In Table 1, A, B, C, and D represent four factors, and 1, 2, and 3 represent three levels. For example, A represents the PAC dosage, and the PAC dosage is divided into 75 mg / L, 90 mg / L, and 105 mg / L, namely A1, A2, and A3. The same is true for B, C, and D.

[0046] Table 2 Results of Taguchi orthogonal test and range analysis

[0047] (a)

[0048]

[0049] Note: The best combination of factors obtained through orthogonal experiments is A3B3C3D2, i.e. 105 mg / L PAC, 3 mg / L PAM, 30 mg / L Fe3O4, and precipitation time 2 min.

[0050] (b)

[0051]

[0052]

[0053] Note: The best combination of factors obtained through orthogonal experiments is A3B3C3D2, i.e. 105 mg / L PAC, 3 mg / L PAM, 30 mg / L Fe3O4, and precipitation time 2 min.

[0054] pass Figure 1 From the combined analysis of Table (a) and Table (b), it can be obtained that the dosages of PAC, Fe3O4 and PAM were selected as 105 mg / L, 30 mg / L and 3 mg / L respectively, and the sedimentation time was 2 min. Figure 3 As shown, the NH4 + -N removal rate is 99.7%, COD removal rate is 91.3%, TP removal rate is 99.5%, SS removal rate is 93.3%, and the effluent concentrations are 0.17mg / L, 24.20mg / L, 0.03mg / L and 6.10mg / L respectively, meeting the requirements for river discharge. The TP and SS removal performance of this process is significantly better than that of a single A / O process.

[0055] Example 2

[0056] The influent water quality and the pilot plant were the same as those in Example 1, COD = 300 mg / L, total nitrogen (TN) = 70 mg / L, ammonia nitrogen (NH4 + -N)=50mg / L, total phosphorus (TP)=5mg / L and turbidity=80NTU. The working volume ratio of anoxic tank: aerobic tank: rapid flocculation reaction tank: rapid sedimentation tank is 1.5:5:0.3:0.3. The effective volume of anoxic tank and aerobic tank is 1L, separated by a perforated partition. A stirrer is set inside the anaerobic tank, which is a complete mixing type; the flow state of the mixed liquid in the aerobic tank is plug flow in the reactor, and an aeration system is set on the top. The initial inoculum sludge concentration of the biological treatment system is 5000±100mg / L. The speed of the stirrer in the anaerobic tank is set to 200r / min, the dissolved oxygen concentration is 0.2mg / L; the dissolved oxygen concentration in the aerobic tank is 5mg / L. The hydraulic retention time in the anoxic tank is 20min, the aerobic tank is 10min, and the sedimentation time in the sedimentation tank is 20min. The sludge age of the biological treatment system is 12 days, the sludge return ratio is 0.5, and the influent pH is controlled at 7.3.

[0057] The effective volume of the rapid flocculation reaction tank and the rapid sedimentation tank is 500mL. The rapid flocculation reaction tank is equipped with an agitator, and the speed is set to 350r / min. A strong magnet with a radius of 2cm and a height of 0.5cm is installed at the bottom of the rapid sedimentation tank. In the magnetic flocculation system, the dosages of PAC, Fe3O4 and PAM are 105mg / L, 30mg / L and 3mg / L respectively. The reaction time of the rapid flocculation reaction tank is 3min, and the sedimentation time of the rapid sedimentation tank is 3min.

[0058] After the hydraulic retention time of the anoxic tank was extended from 10 minutes in the embodiment to 15 minutes, the experimental results showed that NH4 + -N, COD, TP removal rates changed slightly, NH4 + -N removal rate increased from 49.6% to 49.7%, COD removal rate increased from 56.7% to 56.0%, and TP removal rate increased from 70.6% to 70.9%. Then, a 50-minute aerobic treatment process was carried out. The results showed that NH4 + The removal rate of -N was significantly increased to 96.8%, the removal rate of COD was also increased to 88.5%, and the removal rate of TP was as high as 93.0%. During the magnetic flocculation process, the dosages of PAC, Fe3O4 and PAM were 105 mg / L, 30 mg / L and 3 mg / L respectively. The reaction time of the rapid flocculation reaction tank was 3 min. The sedimentation time of the rapid sedimentation tank was 3 min. The NH4 +-N removal rate is 97.1%, COD removal rate is 88.9%, TP removal rate is 99.4%, SS removal rate is 93.2%, and the effluent concentrations are 1.66mg / L, 30.9mg / L, 0.03mg / L and 6.8mg / L respectively. + The treatment effects of -N and COD are not much different from the significant effects achieved in Example 1.

[0059] Comparative Example 1

[0060] The influent water quality and the pilot plant were the same as those in Example 1, COD = 300 mg / L, total nitrogen (TN) = 70 mg / L, ammonia nitrogen (NH4 + -N)=50mg / L, total phosphorus (TP)=5mg / L and turbidity=80NTU. The working volume ratio of anoxic tank: aerobic tank: rapid flocculation reaction tank: rapid sedimentation tank is 2:1:0.2:0.2. The effective volume of anoxic tank and aerobic tank is 1L, separated by a perforated partition in the middle. A stirrer is set inside the anaerobic tank, which is a complete mixing type; the mixed liquid in the aerobic tank flows in the reactor in a plug flow type, and an aeration system is set on the top. The initial inoculated sludge concentration of the biological treatment system is 5000±100mg / L. The stirrer speed of the anaerobic tank is set to 200r / min, the dissolved oxygen concentration is 0.2mg / L; the dissolved oxygen concentration of the aerobic tank is 5mg / L. The hydraulic retention time in the anoxic tank is 20min, the aerobic tank is 10min, and the sedimentation time in the sedimentation tank is 20min. The sludge age of the biological treatment system is 12 days, the sludge return ratio is 0.5, and the influent pH is controlled to be 7.3.

[0061] The effective volume of the rapid flocculation reaction tank and the rapid sedimentation tank is 500mL. The rapid flocculation reaction tank is equipped with an agitator, and the speed is set to 350r / min. A strong magnet with a radius of 2cm and a height of 0.5cm is installed at the bottom of the rapid sedimentation tank. In the magnetic flocculation system, the dosages of PAC, Fe3O4 and PAM are 75mg / L, 10mg / L and 0.5mg / L respectively. The reaction time of the rapid flocculation reaction tank is 2min, and the sedimentation time of the rapid sedimentation tank is 2min.

[0062] After the hydraulic retention time of the anoxic tank was extended from 10 minutes in the embodiment to 20 minutes, the experimental results showed that NH4 + -N removal increased only slightly, from 49.6% to 49.8%, an increase of only 0.2%. At the same time, COD removal increased slightly from 56.7% to 57.8%, and TP removal also increased slightly from 70.6% to 71.4%. Overall, these changes are relatively small, indicating that extending the hydraulic retention time of the anoxic tank has limited effect on the removal of pollutants. This was followed by a 10-minute aerobic treatment process, and the results showed that NH4 +-N removal rate significantly increased to 79.8%, COD removal rate also increased to 76.8%, and TP removal rate reached 93.6%. This result shows that the aerobic process plays a key role in improving the removal efficiency of pollutants. In the magnetic flocculation process, the dosages of PAC, Fe3O4 and PAM were 60mg / L, 10mg / L and 0.5mg / L respectively. The reaction time of the rapid flocculation reaction tank is 2min. The sedimentation time of the rapid sedimentation tank is 1min. The NH4 + -N removal rate was 81.2%, COD removal rate was 77.4%, TP removal rate was 99.2%, SS removal rate was 92.1%, and the effluent concentrations were 9.40mg / L, 67.80mg / L, 0.04mg / L and 7.9mg / L respectively. Compared with the significant effect achieved in Example 1, the current + -N and COD treatment efficiency decreased significantly. Comparative Example 1 changed the parameters proposed by the present invention, such as working volume ratio, A / O treatment time and flocculant dosage, resulting in NH4 + The treatment effects of -N and COD are not good, and the present invention solves this problem by controlling relevant parameters.

[0063] In summary, the combined process of the present invention is only suitable for the rapid treatment of overflow sewage, and its characteristic is "rapid". Since overflow pollution is a sudden water pollution incident, once it occurs, the water volume is large, the concentration of pollutants increases instantaneously, and it is almost directly discharged into the river through pipes, directly polluting the water body. In-situ treatment needs to follow the requirements of rapid treatment. Conventional biochemical treatment requires 6-8h or even longer processing time, and although magnetic flocculation technology is fast, the single magnetic flocculation technology is only effective in removing suspended matter and TP, and has poor removal effects on pollutants such as nitrogen and COD, and can hardly meet the river discharge standards. In order to meet the demand for rapid treatment, the present invention reduces the treatment time by controlling the sewage retention time in the anoxic tank, aerobic tank and magnetic flocculation processes. The three units do not reach the conventional optimal biochemical treatment time, such as the anoxic tank is reduced from the conventional 2-3h to 10min, the aerobic tank is reduced from the conventional 6-8h to 60min, and the magnetic flocculation cancels the medium-speed stirring and slow stirring. The final reaction time is 2min, the sedimentation time is 2min, and the overall process, plus the sedimentation tank time, is 84min. Under the condition of a significant reduction in hydraulic retention time, the treatment effect of each unit alone is not excellent, but the three systems are coupled, and the flocculant dosage is optimized and the sludge concentration in the biochemical tank is increased, so that the nitrogen, phosphorus, organic matter and suspended solids in the overflow sewage are gradually reduced, so that the effluent meets the river discharge standard. The present invention sacrifices the treatment efficiency of a single treatment unit, but achieves a short treatment time and can achieve the effect of improving the treatment efficiency of multiple types of pollutants through the combination of three processes. To achieve this technical effect, it is necessary to control the sludge concentration of the anoxic tank and the aerobic tank to be greater than 5000mg / L. Too low will greatly reduce the treatment effect. Strictly control the dissolved oxygen in the anoxic tank to 0.1-0.3mg / L and the dissolved oxygen in the aerobic tank to 4-6mg / L. Insufficient control of dissolved oxygen will not achieve the effect of step-by-step reduction of pollutant concentration to a controllable range. The PAC, PAM and magnetic seed dosages in the above magnetic flocculation process are all the optimal maximum doses for actual overflow sewage treatment.

[0064] Therefore, after treatment by the biotechnology coupled magnetic flocculation system, the effluent water quality is clear, and the treatment process effectively reduces suspended particles and improves water transparency. + The -N removal rate is 99.7%, the COD removal rate is 91.3%, the TP removal rate is 99.5%, and the SS removal rate is 93.3%, which are all higher than those of traditional biological treatment technologies and have higher advantages in SS and TP removal.

[0065] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage, characterized in that: The system includes an A / O biological treatment system and a magnetic flocculation treatment system; The A / O biological treatment system includes an anoxic tank, an aerobic tank and a sedimentation tank; The magnetic flocculation treatment system includes a magnetic seed dosing system, a flocculation agent dosing system, a magnetic flocculation reaction system and a magnetic seed recovery system; and the magnetic flocculation reaction system includes a rapid flocculation reaction tank and a rapid sedimentation tank; Wherein, the working volume ratio of the anoxic tank: the aerobic tank: the rapid flocculation reaction tank: the rapid sedimentation tank is 1.0-1.5: 5.0-7.0: 0.2-0.3: 0.2-0.

3.

2. The A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage according to claim 1 is characterized in that: The sludge age of the A / O biological treatment system is 10-12 days, and the sludge return ratio is 0.4-0.

5.

3. The A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage according to claim 1 is characterized in that: The anoxic tank is used to inoculate and cultivate denitrification activated sludge, with a sludge concentration of 5000±100 mg / L and a dissolved oxygen of 0.1-0.3 mg / L; The aerobic tank is used to inoculate and cultivate nitrification activated sludge, with a sludge concentration of 5000±100 mg / L and a dissolved oxygen of 4-6 mg / L; The sedimentation tank is provided with a sludge return pipe for returning the sludge to the anoxic tank.

4. The A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage according to claim 3 is characterized in that: The top of the anoxic tank is provided with a stirring device for stirring the mixed materials; the bottom of the aerobic tank is provided with an aeration system for balancing the dissolved oxygen content.

5. The A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage according to claim 1 is characterized in that: The magnetic seed dosing system and the flocculating agent dosing system respectively add the magnetic seed and the magnetic flocculating agent into the rapid reaction pool; wherein the magnetic seed is Fe3O4; and the magnetic flocculating agent is PAC and anionic PAM.

6. The A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage according to claim 1, characterized in that: The top of the rapid reaction pool is provided with a stirring system for mixing the magnetic seed, magnetic flocculation agent and sewage, the outside of the bottom of the rapid reaction pool is provided with a magnet for accelerating the sedimentation of flocs, and the inside of the bottom of the pool is provided with a scraper for discharging the flocs to the mud discharge channel.

7. The A / O coupled magnetic flocculation system for rapid treatment of urban overflow sewage according to claim 1 is characterized in that: The magnetic seed recovery system is composed of a magnetic mud shearing machine and a magnetic separator.

8. An operating method of the A / O coupled magnetic flocculation system for rapidly treating urban overflow sewage according to any one of claims 1 to 7, characterized in that: The method comprises the following specific steps: Step S1, during the system startup period, 5000±100 mg / L of activated sludge from the biological treatment section of the sewage treatment plant is inoculated into the bioreactor and operated stably for a period of time to enrich the microorganisms in the pool; Step S2, during the system operation period, the sewage in step S1 flows into the anoxic tank, is mixed with the sludge mixed liquid and the return sludge in the anoxic tank, and then denitrified by denitrifying bacteria to convert nitrate nitrogen into nitrogen gas for removal, thereby obtaining a mixed liquid; Step S3, the mixed solution obtained in step S2 is flowed into an aerobic tank, where ammonia nitrogen is converted into nitrate nitrogen under the nitrification action of nitrifying bacteria, and organic matter is removed to obtain an aqueous solution; Step S4, the aqueous solution obtained in step S3 flows into a sedimentation tank for mud-water separation, the supernatant of the sedimentation tank enters a rapid flocculation reaction tank, and a certain amount of PAC, magnetic seed Fe3O4 and PAM are added, and after stirring, floccules and sewage are obtained; Step S5, the flocs obtained in step S4 and the sewage flow into the rapid sedimentation tank, the magnetic seed Fe3O4 drives the flocs to accelerate the sedimentation to the bottom of the rapid sedimentation tank, the flocs at the bottom of the rapid sedimentation tank are sent to the mud discharge pipeline, the treated sewage supernatant is discharged from the rapid sedimentation tank, and the precipitated flocs are sent to the external magnetic seed recovery system to recover the magnetic seeds; Wherein, in step S5, the NH4 + The -N removal efficiency was 99.7%, COD removal efficiency was 91.3%, TP removal efficiency was 99.5%, and SS removal efficiency was 93.3%.

9. The operating method of the A / O coupling magnetic flocculation system for rapidly treating urban overflow sewage according to claim 8 is characterized in that: The hydraulic retention time of the anoxic tank is 10-15 minutes, the hydraulic retention time of the aerobic tank is 50-70 minutes, and the sedimentation time of the sedimentation tank is 10-20 minutes. ， The hydraulic retention time in the rapid flocculation reaction tank is 2-3 minutes.

10. The operating method of the A / O coupling magnetic flocculation system for rapidly treating urban overflow sewage according to claim 8, characterized in that: In step S4, the dosage of PAC is 75-105 mg / L, the dosage of magnetic seed Fe3O4 is 10-30 mg / L, and the dosage of PAM is 0.5-3 mg / L; the stirring speed is 350 r / min.

Images