Sewage treatment system and sewage treatment method

Abstract

The invention provides a sewage treatment system and a sewage treatment method. The sewage treatment system comprises an anaerobic tank and an aerobic tank, the anaerobic tank and the aerobic tank are adjacently arranged, the anaerobic tank is of a sealed structure, a water inlet of the anaerobic tank is positioned above the side wall, a water outlet of the anaerobic tank is positioned at the bottom of the opposite side wall and is communicated with the aerobic tank, a water outlet of the aerobic tank is positioned above the opposite side wall, and the aerobic tank is of an open structure. According to the sewage treatment system provided by the embodiment of the invention, the nitrogen and phosphorus removal efficiency can be exerted to the greatest extent by transforming the single tank body and adjusting the parameters of the tank body, the optimization of reflux and retention time is considered in design, and the denitrification and phosphorus removal effects are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a sewage treatment system and a sewage treatment method. BACKGROUND

[0002] At present, activated sludge method is widely used in wastewater treatment, which has been applied for more than one hundred years, mainly for removing pollution elements such as COD, ammonia nitrogen, total nitrogen and total phosphorus in wastewater. With the acceleration of industrialization, industrial wastewater pollution gradually surpasses municipal wastewater, and activated sludge method is also applied to industrial wastewater treatment. However, due to the high concentration problem of industrial wastewater, in the development process of nearly one hundred years, activated sludge method has evolved into CASS process (periodic activated sludge process, also known as cyclic activated sludge process), AO process (anaerobic-aerobic process), SBR process (sequencing batch reactor process), oxidation ditch process and biofilm process, in order to adapt to the treatment of different wastewater and the development and change of industry. Among them, the process that meets the high COD and denitrification and phosphorus removal of wastewater becomes an important field of wastewater treatment.

[0003] In the existing SBR process, the COD removal rate is only 85.2% in the normal wastewater denitrification and phosphorus removal process, the TN (total nitrogen) removal rate is only 62.4%, and the TP (total phosphorus) removal rate is only 65.7% (from the literature “Exploration of optimal operation condition of SBR denitrification and phosphorus removal”). In the case of fixed inflow mode and prolonged cycle, the COD removal rate can be increased to 87.2%, the TN removal rate can be increased to 82.19%, and the TP removal rate can be increased to 70.39%. However, for papermaking wastewater, prolonging the cycle and fixing the mode will reduce the wastewater treatment capacity. Another AO process with denitrification and phosphorus removal function has a COD removal rate of only 88%, and a TN (total nitrogen) removal rate of only 80% (from the literature “Analysis of denitrification efficiency of A / O improved process”). After increasing the multi-stage A pool, the COD removal rate can be increased to 90%, and the TN (total nitrogen) removal rate can be increased to 90%. However, after the transformation, the anoxic tank and the internal return sludge need to be increased, which increases the construction cost and operation cost. SUMMARY

[0004] The first aspect of the embodiment of the present application provides a sewage treatment system, which comprises an anaerobic tank and an aerobic tank; the anaerobic tank is arranged adjacent to the aerobic tank, the anaerobic tank is a sealed structure, the water inlet of the anaerobic tank is located at the upper position of the side wall, the water outlet is located at the bottom position of the opposite side wall and is communicated with the aerobic tank, the water outlet of the aerobic tank is located at the upper position of the opposite side wall, and the aerobic tank is an open structure.

[0005] In some optional embodiments, the depth of the anaerobic tank and the depth of the aerobic tank are both greater than or equal to 7 meters.

[0006] In some optional embodiments, the anaerobic tank bottom is provided with a first agitator, which is a jet agitator.

[0007] In some optional embodiments, the aerobic tank bottom is provided with a second agitator, which is a jet mixing aeration device.

[0008] In some optional embodiments, the sewage treatment system further comprises a secondary sedimentation tank, which is communicated with the effluent outlet of the aerobic tank through a pipeline.

[0009] In some optional embodiments, the surface load of the secondary sedimentation tank is < 0.6 m 3 / ㎡.h.

[0010] In some optional embodiments, the sewage treatment system further comprises a reflux pipeline, which is used to communicate the bottom of the secondary sedimentation tank and the influent inlet of the anaerobic tank.

[0011] In the second aspect, the embodiments of the present application provide a sewage treatment method, which uses the sewage treatment system of any one of claims 1-7 to treat sewage.

[0012] In some optional embodiments, the hydraulic retention time of the anaerobic tank is ≥ 4 hours, and the dissolved oxygen is maintained at < 0.2 mg / L; the hydraulic retention time of the aerobic tank is > 24 hours, the dissolved oxygen of the front section is maintained at 0.3-1.0 mg / L, and the dissolved oxygen of the rear section is maintained at 1.5-2.0 mg / L.

[0013] In some optional embodiments, the sewage treatment system further comprises a secondary sedimentation tank and a reflux pipeline, the secondary sedimentation tank is communicated with the effluent outlet of the aerobic tank through a pipeline, and the reflux pipeline is used to communicate the bottom of the secondary sedimentation tank and the influent inlet of the anaerobic tank; wherein the reflux amount of the reflux pipeline is 150%-300%.

[0014] The sewage treatment system provided by the embodiments of the present application can maximize the denitrification and phosphorus removal efficiency by reforming the single tank and adjusting the tank parameters, and the optimization of reflux and retention time is considered in the design, thereby improving the denitrification and phosphorus removal effect. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1is a schematic diagram of the overall structure of an embodiment of the sewage treatment system of the present application;

[0017] Figure 2 is Figure 1 is a schematic diagram of the structure of the anaerobic tank in the embodiment;

[0018] Figure 3 is Figure 1 is a schematic diagram of the structure of the aerobic tank in the embodiment;

[0019] Figure 4 is Figure 1 is a schematic diagram of the structure of the secondary sedimentation tank in the embodiment. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with the drawings and embodiments. It is particularly pointed out that the following embodiments are only for illustrating the present application, but do not limit the scope of the present application. Similarly, the following embodiments are only part of the embodiments of the present application, but not all the embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0021] The terms "first", "second", "third" in the embodiments of the present application are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second", "third" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly. The terms "include" and "have" and any variations thereof in the embodiments of the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or components inherent to the process, method, product or device.

[0022] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that the embodiments described herein are merely examples from a multitude of possible embodiments, which can be literally combined or otherwise combined with other embodiments to produce additional embodiments including development sets of the present application.

[0023] The application field of the present application includes papermaking wastewater, chemical wastewater, petroleum wastewater, municipal wastewater, etc. sewage treatment facilities and aquaculture wastewater and black and odorous water treatment. For high ammonia nitrogen, total nitrogen and total phosphorus indicators in wastewater, if not properly controlled, it will lead to high effluent value, and further cause eutrophication of water bodies around the discharge area, endanger the benign cycle of the ecological system of the discharge area for a long time, and even cause ecological imbalance and loss of water species diversity.

[0024] The technical solution of the present application is to further improve the AO process at the present stage, to seal the anaerobic tank, to deepen the tank body and to prolong the residence time, so as to optimize the process, significantly improve the total nitrogen removal efficiency to 88%, the total phosphorus removal efficiency to 95% and the COD removal rate to optimize the effluent water quality.

[0025] The sewage treatment system and method in the embodiments of the present application aim to improve the removal efficiency of three important indicators of COD, TN and TP in wastewater. The removal mechanism of the three important pollution indicators is described below.

[0026] (1) COD refers to the chemical oxygen demand, which indicates the amount of reducing substances in water, and is mainly in the form of organic matter in water. After the microorganisms in the activated sludge take up the organic matter in the water, they decompose the organic matter through biological enzymes, a part of the organic matter is decomposed to provide energy for the physiological activities of the microorganisms and is converted into CO2, and a part of the organic matter is synthesized into new activated sludge, and the above decomposition and metabolism and the synthesis of microbial cells gradually complete the degradation of COD.

[0027] (2) The denitrification mechanism of TN is the process of converting organic nitrogen, ammonium nitrogen, nitrite nitrogen and nitrate nitrogen into nitrogen gas (N2) and nitrogen oxides (NxO) under the action of microorganisms. It includes nitrification and denitrification processes.

[0028] Nitrification is the process of converting NH4 + to N02 - and NO3 - under aerobic conditions, which is completed by both nitrite bacteria and nitrate bacteria. These two bacteria are chemoautotrophic microorganisms, and the reaction formula is as follows:

[0029] Nitrosation stage reaction: 2NH4 + + 3O2→ 2NO2 - + 4H + + 2H2O

[0030] Nitrification stage reaction: 2NO2 - + O2→ 2NO3 -

[0031] Nitrifying bacteria are chemoautotrophic bacteria, with low growth rate and sensitive to environmental conditions: ① The optimum temperature is 20-30℃. ② The dissolved oxygen requirement is >2mg / L. ③ The sludge age should be greater than the growth period of nitrifying bacteria. ④ The PH is suitable for 7-8. ⑤ The BOD5 should not be too high, and high BOD5 can easily lead to the proliferation of heterotrophic bacteria. The following table shows the relationship between the ratio of BOD5 / TKN and the proportion of nitrifying bacteria.

[0032] BOD5 / TKN Proportion of nitrifiers BOD5 / TKN Proportion of nitrifiers 0.5 0.35 5 0.054 1 0.21 6 0.043 2 0.12 7 0.037 3 0.083 8 0.033 4 0.064 9 0.029

[0033] Denitrification is the process of reducing nitrate nitrogen (NO3 - ) and nitrite nitrogen (NO2 - ) to nitrogen gas under anaerobic conditions, and the reaction equation is as follows:

[0034]

[0035] Denitrifying bacteria are heterotrophic and facultative anaerobic bacteria. When oxygen exists, it will perform aerobic respiration with O2 as the electron acceptor. When there is no oxygen but N03 - or NO2 - exists, it will perform denitrification reaction with N03 - or NO2 - as the electron acceptor and organic carbon as the electron donor and nutrient source. At the same time of denitrifying bacteria's metabolic activity, it also grows and reproduces, i.e. the synthesis of bacterial cells, and the reaction is as follows:

[0036]

[0037] In the formula, C5H7O2N is the chemical composition of denitrifying microorganisms. The total reaction equation of denitrification reduction and microbial synthesis is as follows:

[0038]

[0039] In the above process, about 96% of NO3 - N is reduced by the dissimilation process, and 4% is synthesized into microorganisms by the assimilation process. In the denitrification reaction, the amount of organic carbon available for denitrification and its biodegradability in wastewater affect the denitrification rate. Empirical analysis data shows that when BOD5 / TKN in wastewater is >3-5, the carbon source can be guaranteed. The suitable PH for denitrification is 6.5-7.5.

[0040] (3)TP removal methods mainly apply to the chemical method and biological method. Among them, the chemical method is mainly based on the reaction of adding aluminum salt, iron salt, lime and other insoluble precipitates, that is, flocculation, but not discussed in this patent. Biological phosphorus removal is to use microorganisms to absorb excess dissolved phosphate in wastewater under aerobic conditions, and then separate and remove phosphorus by precipitation. The sludge containing excess phosphorus is discharged from the system in the form of excess sludge, and most of it enters the anaerobic state with wastewater, at which time the organic matter in the wastewater is converted to acetic acid under the action of anaerobic acid-producing bacteria. The polyphosphorus bacteria in the activated sludge decompose the accumulated polyphosphorus in the body under anaerobic conditions, and part of the energy generated by the decomposition is used for the survival of polyphosphorus bacteria. Another part of the energy is used for polyphosphorus bacteria to actively absorb acetic acid and convert it into PHB (poly-β-hydroxybutyric acid) form stored in the body. The inorganic phosphorus formed by the decomposition of polyphosphorus is released back into the wastewater, which is anaerobic phosphorus release. After entering the aerobic state, the polyphosphorus bacteria in the body decompose the PHB and release a large amount of energy to proliferate the polyphosphorus bacteria, and part of it is used to actively absorb the phosphate in the wastewater and accumulate in the body in the form of polyphosphorus, which is aerobic phosphorus absorption. Due to the continuous enhancement of activated sludge in operation, in order to ensure the stable operation of the system, the activated sludge with the same amount of proliferation must be discharged from the system, which is excess sludge. The excess sludge contains polyphosphorus bacteria that absorb excess phosphorus, which is the phosphorus-containing substance removed from the wastewater. This is the essence of biological phosphorus removal.

[0041] (4) The existing biological denitrification and phosphorus removal process mainly includes A2 / O method, improved Bardenpho process (pre-position denitrification process of denitrification energy), UCT process (simultaneous denitrification and phosphorus removal), and SBR process. The first three processes all need to complete denitrification and phosphorus removal through multi-stage anaerobic and aerobic series connection, and the process is complex and the highest removal rate is not more than 85%.

[0042] Through the analysis of the above four common wastewater treatment processes, the deficiencies are improved, and the process is reformed to achieve a true anaerobic state by sealing the anaerobic tank under the most suitable denitrification and phosphorus removal process mechanism, and the anaerobic tank residence time is increased to more than 4 hours. The anoxic-anaerobic alternating state is achieved, and the denitrification effect is achieved. At the same time, the high COD of the front section of the water ensures the conversion of acetic acid to PHB by polyphosphorus bacteria under anaerobic conditions, so that the polyphosphorus bacteria can absorb a large amount of phosphorus under aerobic conditions. Compared with the Bardenpho process and the UCT process, the process section is simplified, the anaerobic and anoxic tank bodies are combined, the residence time is increased, but the anaerobic and anoxic alternating processes are still ensured, and the anaerobic and anoxic denitrification states and phosphorus absorption are optimized. The denitrification efficiency can be increased to 90%. In order to better utilize energy and oxygen transfer efficiency, the tank height is designed to be more than 7 meters, which can accelerate the removal of COD and the effect of denitrification and phosphorus removal.

[0043] Please refer to Figure 1 , Figure 1is the overall structure schematic diagram of an embodiment of the sewage treatment system of the present application, which comprises an anaerobic tank 100, an aerobic tank 200 and a secondary sedimentation tank 300.

[0044] Specifically, please refer to Figure 2 , Figure 2 is Figure 1 The structure schematic diagram of the anaerobic tank in the embodiment, wherein the anaerobic tank (i.e. A tank) 100 is arranged adjacent to the aerobic tank 200, the anaerobic tank 100 is sealed at the periphery and the top (by using the upper cover 110), the tank depth D1 is greater than or equal to 7 meters, and in some preferred embodiments, the tank depth is greater than or equal to 8 meters, which can ensure the exertion of anaerobic state. Only the water inlet 101 at the tank surface (near the upper position of the side wall) and the water outlet 102 at the tank bottom are reserved, the water inlet 101 and the water outlet 102 are in a diagonal form, the water inlet 101 is located at the upper water inlet, and the water outlet (i.e. the water inlet of the aerobic tank 200) 102 is located at the lower (bottom position of the side wall) water outlet, which maximizes the water flow mixing without dead angle, and the first agitator 103 is installed in the tank, wherein the first agitator 103 can be a common blade agitator or a jet agitator, the jet agitator can make the mixed liquid completely mixed and circulated, and play the role of repeated alternation of anaerobic and anoxic. The construction cost is saved by saving the traditional anaerobic-anoxic tank shunt step procedure. The reaction area is designed in an integrated manner, which plays the role of anaerobic-anoxic facultative oxygen type.

[0045] Wherein, the hydraulic retention time is kept for more than 4 hours, and the dissolved oxygen is less than 0.2 mg / L, which ensures that the activated sludge system is in an anoxic-anaerobic reaction state, improves the denitrification effect, and synchronously enters the water into the anaerobic tank to ensure the carbon source supply for the nitrifying bacteria in the anaerobic-anoxic area, and maximizes the denitrification and dilution phosphorus aggregation effect.

[0046] Wherein, the water outlet 102 of the anaerobic tank 100 is communicated with the water inlet 203 of the aerobic tank 200, the water outlet 201 of the aerobic tank 200 is located at the upper position of the opposite side wall, and the aerobic tank 200 is in an open structure. Please refer to Figure 3 , Figure 3 is Figure 1The structure of the aerobic tank in the embodiment is shown in the schematic diagram. The O tank (aerobic tank) adopts an open mode, the tank depth D2 is greater than or equal to 7 meters, in some preferred embodiments, the tank depth is greater than or equal to 8 meters, and the depth of the anaerobic tank 100 is kept consistent, which can improve the aeration and oxygen dissolution efficiency. The water flow presents forward and backward, the water inlet is located at the bottom of the front section of the tank, and the water outlet 102 of the anaerobic tank 100 is connected. The water outlet 201 of the aerobic tank 200 is located at the upper part of the rear section (above the side wall, 0.5 meters below the height of the tank body, to ensure stable water inflow and outflow). The second agitator 202 is installed on the bottom of the tank in all directions. The second agitator 202 can be a jet mixing aeration device. The jet mixing aeration device can make the water flow and aeration fully mixed, the oxygen utilization rate is high, the activated sludge system is in an aerobic reaction state, the hydraulic retention time is kept above 24 hours, and the nitrification and phosphorus accumulation reaction is maximized. The dissolved oxygen in the front section is kept at 0.3-1.0 mg / L (specifically, it can be 0.3 mg / L, 0.5 mg / L, 0.8 mg / L, 1.0 mg / L, etc.), and the dissolved oxygen in the rear section is kept at 1.5-2.0 mg / L, to ensure the nitrification reaction and phosphorus accumulation in the tank, and to maximize the nitrogen and phosphorus removal.

[0047] The aerobic tank 200 can be designed in a rectangular strip shape, and the fluid flows from front to back as the space moves. The degradation of COD in water and the nitrification reaction are more sufficient, and the jet mixing aeration device jet is used. In 24 hours of hydraulic retention time, the aerobic tank fluid can be fully mixed and circulated 10 times, fully achieving the complete mixing reaction efficiency.

[0048] The jet mixing aeration device can include a jet pump, a multi-stage centrifugal blower, a water jet pipe, an air pipe, etc. The air pipe wraps the water jet pipe, and the water jet pipe and the air pipe are integrally formed. The air cavity wraps the water jet. The power fluid enters the power nozzle through the flow guide ring of the jet, forming a high-speed water flow. The high-pressure air is pressed into the air pipe by the multi-stage centrifugal blower, and the air is carried into the air suction port due to the entraining effect of the fluid. The carried air expands rapidly, and the expanded air is cut into tiny bubbles by the high-speed power fluid. The bubbles enter the mixing chamber under the carrying of the power fluid, and the gas, water and sludge are fully mixed in the mixing chamber. The mixed gas-liquid-solid mixture enters the diffusion chamber, and the kinetic energy is gradually converted into potential energy in the chamber, and is shot out at high speed under the counterpressure of the outlet. The oxygenation efficiency of the jet aeration increases with the increase of the water depth. The oxygenation efficiency of the new jet aeration device can reach 35% at a water depth of 8 meters, and the gas-water ratio is only 4:1. The water used to charge the same amount of air is relatively small, and the energy consumption is also reduced, greatly reducing the cost of sewage treatment. The gas is cut into extremely fine bubbles by the high-speed fluid, which is one of the reasons for high oxygen utilization. The turbulent flow generated by the jet mixing aeration device constantly updates the gas / liquid interface, which is also beneficial to the transfer of oxygen. The detailed structure of the jet mixing aeration device is within the understanding range of those skilled in the art, and will not be described here.

[0049] The 24-hour hydraulic retention time can make the sludge age greater than the generation growth cycle of nitrifying bacteria, keep the activated sludge in the logarithmic growth phase, and play the best performance of COD degradation and nitrification reaction. The abnormal high load impact should be responded.

[0050] Please continue to refer to Figure 1 The sewage treatment system in the embodiment further includes a secondary sedimentation tank 300, which is communicated with the water outlet 201 of the aerobic tank 200 through a pipeline 302 (water inlet pipeline in the figure). Please refer to Figure 4 , Figure 4 is Figure 1 The structure diagram of the secondary sedimentation tank in the embodiment. The secondary sedimentation tank 300 adopts a radial flow sedimentation tank, the tank depth D3 is greater than 4 meters, the tank capacity guarantees that the surface load is less than 0.6 m 3 / ㎡.h, and the tank capacity hydraulic retention time is greater than 6 hours, which can guarantee the layered sedimentation of the activated sludge. The sludge can consume dissolved oxygen in the sedimentation, and assist the sludge reflux anaerobic tank to perform denitrification and phosphorus aggregation, thereby reducing the influence of the aerobic state on the anaerobic state. The sludge reflux pump adopts a large-flow low-lift type, and the reflux amount is greater than the design inlet flow, so as to ensure that the sludge reflux ratio is greater than 1:1, and the denitrification and phosphorus removal performance is guaranteed.

[0051] The sewage treatment system further comprises a (sludge and nitrification liquid) backflow pipe 400 for connecting the bottom of the secondary sedimentation tank 300 and the water inlet 101 of the anaerobic tank 100. The backflow amount of the backflow pipe 400 is 150%-300%, and the specific backflow amount can be 150%, 180%, 200%, 250%, 300% and the like. The backflow pipe 400 can also be used for nitrification liquid backflow. The secondary sedimentation tank 300 is designed to have a small surface load and a long residence time of 8 hours. Different from the traditional nitrification liquid backflow of the aerobic tank, the present application can perform large-scale backflow of the mixed liquid in the secondary sedimentation tank, reduce the dissolved oxygen brought into the anaerobic tank, and increase the denitrification of the anaerobic tank.

[0052] The sludge can consume dissolved oxygen in the sedimentation, assist the sludge backflow into the anaerobic tank for denitrification and dilute phosphorus aggregation, and reduce the influence of the aerobic state on the anaerobic state. The sludge backflow pump adopts a large flow and a low lift, and the backflow amount is greater than the designed water inflow, so as to ensure that the sludge backflow ratio is greater than 1:1.

[0053] In addition, the sewage treatment system in the embodiment further comprises a sludge discharge pipe 500 connected with the bottom of the secondary sedimentation tank 300 and used for discharging sludge.

[0054] The sewage treatment system in the embodiment can reduce the construction and use of the A tank (anaerobic tank), improve the removal efficiency of COD, total nitrogen and total phosphorus by changing the capacity, prolonging the residence time, strengthening the anaerobic environment, improving the growth cycle of activated sludge and shortening the process flow, and the like.

[0055] The sewage treatment system and the treatment method in the embodiment can maximize the denitrification and phosphorus removal efficiency. The comparison cases and test data are as follows.

[0056] The following is the actual application of SBR process denitrification and phosphorus removal efficiency ratio of a large pulp and paper enterprise. The design treatment capacity is 45000m 3 / day, and the influent is periodic intermittent water.

[0057]

[0058] The effluent indicators are as follows: the COD removal rate is about 86%, the total nitrogen removal rate is about 68%, and the total phosphorus removal rate is about 66%.

[0059] The following table is the experimental data of the sewage treatment system and the treatment method in the embodiment.

[0060]

[0061] The actual continuous processing capacity of the above table is greater than the design capacity, and the effluent indicators show that the actual removal rate is more than 85%, with a maximum of 96%, which can meet the requirements of the pulp and papermaking wastewater discharge standard (total nitrogen < 12 mg / L). COD can also be discharged up to standard (COD < 90 mg / L), with a very high removal efficiency. The average removal rate of COD is 94.02%, the average removal rate of total nitrogen is 88.61%, and the average removal rate of total phosphorus is 95.21%, which is higher than the conventional AO process and SBR process.

[0062] The sewage treatment system and the treatment method in the embodiments of the present application optimize the internal reactor from the mechanism of denitrification and phosphorus removal by changing the shape of the monomer structure, so that the biological reaction is more complete. The modified monomer structure is more suitable for high COD removal and denitrification and phosphorus removal of pulp and papermaking wastewater, with a COD removal rate of ≥ 94%, a total nitrogen removal rate of ≥ 88%, and a total phosphorus removal rate of ≥ 95%. The modified structure is connected in series, simplifying the process flow, facilitating practical operation and saving costs; the removal rates of COD, total nitrogen and total phosphorus are increased by 1%, and the addition of chemicals in the later stage is reduced by 20 g / m 3 That is, 20 g of chemicals can be saved for each cubic meter of wastewater, reducing costs.

[0063] The above only describes some embodiments of the present application, and does not limit the protection scope of the present application, and any equivalent device or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A sewage treatment system characterised in that, The sewage treatment system comprises an anaerobic tank and an aerobic tank; the anaerobic tank is arranged adjacent to the aerobic tank; the anaerobic tank is of a sealed structure; the water inlet of the anaerobic tank is located at an upper position of a side wall; the water outlet is located at a bottom position of an opposite side wall and is communicated with the aerobic tank; the water outlet of the aerobic tank is located at an upper position of an opposite side wall; and the aerobic tank is of an open structure.

2. The sewage treatment system of claim 1, wherein, The depth of the anaerobic tank and the aerobic tank is greater than or equal to 7 meters.

3. The sewage treatment system of claim 1, wherein, The anaerobic tank is provided with a first agitator at the bottom, which is a jet agitator.

4. The sewage treatment system of claim 3, wherein, The aerobic tank is provided with a second agitator at the bottom, which is a jet mixing aerator.

5. The sewage treatment system of claim 1, wherein, The sewage treatment system further comprises a secondary sedimentation tank, which is communicated with the water outlet of the aerobic tank through a pipeline.

6. The sewage treatment system of claim 5, wherein, The surface load of the secondary sedimentation tank is <0.6 m 3 / m2.h.

7. The sewage treatment system of claim 5, wherein, The sewage treatment system further comprises a reflux pipe, which is used to communicate the bottom of the secondary sedimentation tank with the water inlet of the anaerobic tank.

8. A method of sewage treatment, characterised in that, The sewage treatment method is performed by using the sewage treatment system according to any one of claims 1-7.

9. The method of sewage treatment according to claim 8, characterized in that, The hydraulic retention time of the anaerobic tank is greater than or equal to 4 hours, and the dissolved oxygen is kept less than 0.2 mg / L; the hydraulic retention time of the aerobic tank is greater than 24 hours, the dissolved oxygen of the front section is kept at 0.3-1.0 mg / L, and the dissolved oxygen of the rear section is kept at 1.5-2.0 mg / L.

10. The method of sewage treatment according to claim 9, characterized in that, The sewage treatment system further comprises a secondary sedimentation tank and a reflux pipe; the secondary sedimentation tank is communicated with the water outlet of the aerobic tank through a pipeline; and the reflux pipe is used to communicate the bottom of the secondary sedimentation tank with the water inlet of the anaerobic tank; wherein the reflux amount of the reflux pipe is 150%-300%.

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