Sewage treatment process and sewage treatment system with multiple operation modes

Abstract

The invention provides a sewage treatment process with multiple operation modes and a sewage treatment system, and belongs to the technical field of sewage treatment. Comprising a first reaction zone, a second reaction zone and a third reaction zone which are used for sewage denitrification and / or dephosphorization and are carried out in sequence, and nitrification liquid treated in the third reaction zone flows back to the first reaction zone; switching among a dephosphorization priority mode, a dephosphorization and denitrification balance mode or a denitrification priority mode is carried out by controlling a nitrification liquid reflux ratio to adjust ORP (oxidation reduction potential) and / or DO (dissolved oxygen) of the first reaction zone. According to the sewage treatment process with the multiple operation modes, different operation modes can be flexibly adjusted and switched in the same sewage treatment system according to different incoming water qualities, extremely high biological denitrification and / or biological phosphorus removal efficiency can be obtained by controlling the reflux ratio of nitrification liquid to adjust ORP and / or DO, and the investment and treatment cost can also be greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a sewage treatment process and a sewage treatment system with multiple operation modes. Background Art

[0002] At present, the activated sludge process is generally used to treat urban sewage. In order to remove nitrogen and phosphorus, the activated sludge process has been improved into AO process and AAO process. There are two types of AO process, one is the anaerobic-aerobic process (AAO) for phosphorus removal. P O), anoxic-aerobic process (A N O); AAO process is a process that removes both nitrogen and phosphorus. AAO process is currently the most widely used urban sewage treatment process. In order to take into account both phosphorus removal and nitrogen removal, anaerobic tanks, anoxic tanks and aerobic tanks are set up. In the activated sludge of this system, the bacterial community is mainly composed of nitrifying bacteria, denitrifying bacteria and polyphosphate bacteria. In the anaerobic section, polyphosphate bacteria release phosphorus and absorb easily degradable organic matter such as low-level fatty acids. In the aerobic section, polyphosphate bacteria absorb phosphorus in excess and remove phosphorus through the discharge of residual sludge; in the anoxic section, denitrifying bacteria convert the nitrate brought in by the internal reflow into nitrogen gas through biological denitrification and escape into the atmosphere, thereby achieving the effect of denitrification; in the aerobic section, the activated sludge degrades most of the organic matter in the water, and nitrifying bacteria convert the ammonia nitrogen in the inflow and the ammonia nitrogen formed by ammoniation of organic nitrogen into nitrates through biological nitrification.

[0003] The AAO process has some defects: (1) The operating parameters for phosphorus removal and nitrogen removal include DO, sludge age, reflow ratio, etc. There are many control parameters, and these parameters can only be limited to a narrow range and are often contradictory and lose one thing while focusing on the other. For example, a short sludge age is beneficial to phosphorus removal but not to nitrogen removal, and a long sludge age is beneficial to nitrogen removal but not to phosphorus removal. (2) The AAO process is biological treatment and sedimentation separation. The sludge returned from the sedimentation is used for anaerobic phosphorus release in section A to enhance phosphorus removal; the anoxic section is used for mixed liquor reflow to enhance nitrogen removal; the AAO process system has both sludge reflow and anoxic mixed liquor reflow, and even some variants of the AAO process have multiple reflows. Since the sludge reflow must take into account the MLSS (sludge concentration) of the entire system and the orp value required for anaerobic phosphorus removal, it is sometimes difficult to have both, and the process and control are relatively complicated. (3) The area occupied is large. The AAO process and its variant processes (such as UCT, Bardenpho process, etc.) at least include: anaerobic tank, anoxic tank, aerobic tank, secondary sedimentation tank, return pump room and other structures. For some AAO variants or optimized processes (such as UCT, Bardenpho process, etc.), there will also be several anaerobic tanks or anoxic tanks, multiple reflows, etc., which increase the complexity of the process.

[0004] In addition to the above-mentioned defects, the water quality of sewage in different seasons or from different sources is different, so there are different demands for sewage treatment with different water qualities. For example, for sewage with high total phosphorus and total nitrogen content but low carbon source, since phosphorus removal and nitrogen removal are often not taken into account at the same time, in order to enhance phosphorus removal or nitrogen removal, various AAO deformation processes (such as UCT process, bardenpho process) need to be adopted, which have the disadvantages of many treatment structures, large volume, and complicated process.

[0005] The core of the activated sludge system in treating sewage is to use non-aerated sludge to achieve phosphorus removal and nitrogen removal under specific conditions: sludge releases phosphorus in the anaerobic zone and removes nitrate nitrogen in the anoxic zone. Current AAO technology usually separates these two areas in space, using sludge return and nitrification liquid return to achieve their respective functions.

[0006] At present, there is still a lack of innovative phosphorus and nitrogen removal methods in the market, and most of them still use different partitions for phosphorus and nitrogen removal. In order to achieve a more efficient and simpler phosphorus and nitrogen removal process to meet increasingly stringent environmental protection requirements, there is an urgent need for a sewage treatment technology that is efficient, easy to operate and saves land to deal with current problems. Summary of the invention

[0007] The object of the present invention is to provide a sewage treatment process and a sewage treatment system with multiple operating modes. In the same sewage treatment system, different operating modes can be flexibly adjusted and switched according to different incoming water qualities. By controlling the nitrification liquid reflux ratio to adjust ORP and / or DO, extremely high biological denitrification and / or biological phosphorus removal efficiency can be obtained, and investment and treatment costs can also be greatly reduced.

[0008] To achieve the above-mentioned objectives, the present invention provides, on the one hand, a sewage treatment process with multiple operating modes, including a first reaction zone, a second reaction zone and a third reaction zone for sewage denitrification and / or dephosphorization, which are performed sequentially, and the nitrification liquid treated in the third reaction zone is returned to the first reaction zone, and the phosphorus removal priority mode, the phosphorus removal and denitrification balanced mode or the nitrogen removal priority mode is switched by controlling the reflux ratio of the nitrification liquid to adjust the ORP and / or DO of the first reaction zone.

[0009] As a preferred technical solution, the reflux ratio of the nitrification liquid in the phosphorus removal priority mode is controlled to be 50% to 200% to adjust the ORP of the first reaction zone to -180mv and below, and the second reaction zone is in an aerobic state; the reflux ratio of the nitrification liquid in the phosphorus removal and denitrification balance mode is controlled to be 100% to 600% to adjust the ORP of the first reaction zone to -180mv to -50mv, and the second reaction zone is in an aerobic state; the reflux ratio of the nitrification liquid in the denitrification priority mode is controlled to be 100% to 600% to adjust the ORP of the first reaction zone to -180mv to -50mv, and the DO is 0 to 0.5mg / L, and the second reaction zone is in anoxic or anaerobic state.

[0010] As a preferred technical solution, the treatment process of the phosphorus removal priority mode of the present invention includes:

[0011] S1 The pretreated sewage enters the first reaction zone and reacts with the nitrification liquid refluxed from the third reaction zone, and the polyphosphate bacteria release phosphorus in the first reaction zone;

[0012] S2: the treated liquid after being treated by S1 enters the second reaction zone to undergo an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state;

[0013] S3: The treated liquid after being treated by S2 enters the third reaction zone for secondary excess phosphorus uptake reaction, secondary nitrification reaction and secondary carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

[0014] As a preferred technical solution, the treatment process of the balanced mode of phosphorus and nitrogen removal of the present invention includes:

[0015] S1 The pretreated sewage enters the first reaction zone and is mixed with the nitrification liquid refluxed from the third reaction zone to undergo denitrification and phosphorus release reactions;

[0016] S2: the treated liquid after being treated by S1 enters the second reaction zone to undergo a carbon oxidation reaction, an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state;

[0017] S3 The treated liquid after being treated by S2 enters the third reaction zone for secondary carbon oxidation reaction, secondary excess phosphorus uptake reaction and secondary nitrification reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

[0018] As a preferred technical solution, the treatment process of the denitrification priority mode of the present invention includes:

[0019] S1 The pretreated sewage enters the first reaction zone and reacts with the nitrification liquid refluxed from the third reaction zone to perform a denitrification process;

[0020] The treated liquid S2 after being treated by S1 enters the second reaction zone for secondary denitrification. The second reaction zone is aerated with a small amount or without aeration to be in anoxic or anaerobic state, so that the denitrifying bacteria have more time to use carbon source to convert NO3 - and NO2 - is reduced to N2;

[0021] S3: The treated liquid after being treated by S2 enters the third reaction zone to undergo one excessive phosphorus uptake, one nitrification reaction, and one carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

[0022] Specifically, the DO of the second reaction zone is 0.5 mg / L or less.

[0023] As a preferred technical solution, the sewage treatment process of the present invention also includes S4: separating the mud-water mixture in the third reaction zone into solid and liquid, returning part of the nitrified liquid to the first reaction zone, discharging the supernatant after detection or entering the next deep treatment stage, and sending the rest as residual activated sludge to sludge treatment.

[0024] As a preferred technical solution, the pretreatment of the present invention includes at least one of grid treatment, sand settling treatment and primary sedimentation treatment.

[0025] On the other hand, the present invention provides a sewage treatment system with multiple operating modes, including a first reaction zone, a second reaction zone and a third reaction zone, the first reaction zone includes a first reaction tank, the second reaction zone includes a second reaction tank, the third reaction zone includes a third reaction tank, the first reaction tank, the second reaction tank and the third reaction tank are connected in sequence, and a first reflux pipe is connected between the third reaction tank and the first reaction tank.

[0026] As a preferred technical solution, a first detector group is provided in the first reaction tank; a first aeration device and a second detector group are provided in the second reaction tank; and a third detector group, a second aeration device and a solid-liquid separation device are provided in the third reaction tank.

[0027] Compared with the prior art, the present invention is an innovative AO technology that couples biological treatment with precipitation. Its uniqueness lies in that it only adopts the nitrification liquid reflux design and abandons the traditional sludge reflux. By controlling the nitrification liquid reflux ratio, the purpose of denitrification and phosphorus removal can be achieved efficiently. This simplified system control not only reduces land and energy consumption, but also significantly enhances the stability of the system. Therefore, this technology is widely applicable to various sewage treatment and wastewater treatment application scenarios, showing great application potential and environmental benefits. Its specific beneficial effects are:

[0028] (1) Synchronous phosphorus release and denitrification can be achieved in the first reaction tank. The principle is as follows: ① In an anaerobic and anoxic environment, facultative anaerobic fermentation bacteria convert biodegradable organic matter in sewage into low-molecular fermentation intermediates such as volatile fatty acids (VFA), providing the necessary material basis for phosphorus release and denitrification; ② Polyphosphate-accumulating bacteria release the polyphosphate stored in their bodies to obtain energy for their survival in an anaerobic environment; ③ Denitrifying bacteria use the nitrate produced in the aerobic stage to carry out denitrification and reduce the nitrate to nitrogen gas, thereby achieving the purpose of denitrification; ④ The present invention utilizes the difference between the internal and external conditions of the activated sludge system to achieve synchronous anaerobic phosphorus release and denitrification: there is a better anaerobic environment inside the activated sludge, which is conducive to the phosphorus release reaction of polyphosphate-accumulating bacteria; there is a better anoxic environment on the surface of the activated sludge, which is conducive to the denitrification reaction of denitrifying bacteria. ⑤ The above reaction conditions only need to maintain the redox potential (ORP) and / or dissolved oxygen (DO) of the first reaction tank to achieve simultaneous phosphorus release and nitrogen removal. Similarly, phosphorus removal priority or nitrogen removal priority can be achieved by adjusting the redox potential (ORP) and / or dissolved oxygen (DO) of the first reaction tank.

[0029] (2) The sewage treatment process of the present invention has three operating modes: phosphorus removal priority, balanced phosphorus removal and denitrification, and nitrogen removal priority. It can be flexibly adjusted according to the different water quality of the influent and adopts different operating modes. By controlling the nitrification liquid reflux ratio to control the oxidation-reduction potential (ORP) and / or dissolved oxygen (DO), extremely high biological denitrification effect and / or biological phosphorus removal effect can be achieved, and the investment and treatment costs can also be greatly reduced.

[0030] (3) The sewage treatment system of the present invention comprises a first reaction tank, a second reaction tank and a third reaction tank which are connected in sequence. The process flow is short and land-saving. The sewage can be biologically dephosphorized and / or denitrified in the three reaction tanks by controlling the nitrification liquid reflux ratio, and can meet the treatment standards.

[0031] (4) An aeration device is arranged in the second reaction tank, which can be operated as an anaerobic / anoxic tank or an aerobic tank according to the different water quality of the influent, thereby achieving the effect of biological phosphorus removal and / or nitrogen removal in a targeted manner.

[0032] (5) A solid-liquid separation device is provided in the third reaction tank, through which the sludge and the supernatant can be separated. The solid-liquid separation device is provided in the third reaction tank, and the secondary sedimentation tank is omitted, which saves land and shortens the process flow of sewage treatment.

[0033] (6) Compared with ordinary AAO and various modified processes (such as UCT process and bardenpho process), the present invention has the following significant advantages: first, the secondary sedimentation tank is omitted, thereby significantly reducing the occupied area and making the land utilization rate higher; second, the present invention only adopts the nitrification liquid return, eliminating the complex sludge return system, which not only simplifies the entire treatment process, but also makes the control method more flexible and efficient.

[0034] (7) Compared with the inverted AAO process: The inverted AAO process is for better denitrification. By returning a large amount of sludge into the anoxic tank, denitrifying bacteria use high-quality carbon sources to carry out denitrification reactions, but this will lead to poor phosphorus removal and subsequent precipitation effects. The present invention can adopt a denitrification priority mode to achieve better denitrification, without sludge return, and has no effect on the precipitation effect.

[0035] (8) Compared with the integrated process of oxidation ditch and secondary sedimentation tank: the plug flow state of the oxidation ditch has a large disturbance on the water distribution and sedimentation of the secondary sedimentation tank, resulting in poor sedimentation effect. The solid-liquid separation device of the present invention (specifically, it can be the solid-liquid separation device in CN201911391372.0, or any device in the prior art that uses airlift power to perform solid-liquid separation) performs solid-liquid separation by airlift power, and the flow lines of water distribution and sedimentation are clear, and the sedimentation effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a process flow chart of the sewage treatment process with multiple operation modes of the present invention;

[0037] Figure 2 It is a schematic diagram of a sewage treatment system with multiple operation modes according to the present invention.

[0038] In the accompanying drawings, 100-first reaction zone, 110-first reaction tank, 120-first plug flow stirring device, 130-first detector group, 200-second reaction zone, 210-second reaction tank, 220-first aeration device, 230-second detector, 240-second plug flow stirring device, 300-third reaction zone, 310-third reaction tank, 320-second aeration device, 330-solid-liquid separation device, 340-third detector group, 410-first reflux pipe. DETAILED DESCRIPTION

[0039] On one hand, the present invention provides a wastewater treatment process with multiple operation modes, including a first reaction zone, a second reaction zone and a third reaction zone for denitrification and / or dephosphorization of wastewater, which are performed in sequence, and the nitrification liquid treated in the third reaction zone is refluxed to the first reaction zone, and the phosphorus removal priority mode, the phosphorus removal and denitrification balance mode or the nitrogen removal priority mode are switched by controlling the reflux ratio of the nitrification liquid to adjust the ORP and / or DO of the first reaction zone. Figure 1 The specific processes of the phosphorus removal priority mode, the phosphorus removal and nitrogen removal balanced mode and the nitrogen removal priority mode are respectively described in detail.

[0040] When sewage comes to TP i When (total phosphorus in the inlet water) is high, such as TPi≥4 mg / L (4 mg / L here is only an example, and the present invention is not limited thereto), or when it is desired to reduce the addition of chemical agents and enhance the biological phosphorus removal effect, the phosphorus removal priority mode of the present invention can be adopted. The treatment process of the phosphorus removal priority mode of the present invention includes:

[0041] The pretreated sewage of S1 enters the first reaction zone and reacts with the nitrification liquid returned from the third reaction zone. The polyphosphate bacteria release phosphorus in the first reaction zone, and the reflux ratio is controlled to be 50% to 200% to adjust the ORP of the first reaction zone to -180mv or below;

[0042] The treated liquid S2 after being treated by S1 enters the second reaction zone to undergo an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state;

[0043] S3: the treated liquid after being treated by S2 enters the third reaction zone for secondary excess phosphorus uptake reaction, secondary nitrification reaction and secondary carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state;

[0044] S4 separates the solid-liquid mixture of the mud and water in the third reaction zone, and part of the nitrified liquid flows back to the first reaction zone. The supernatant is discharged after detection or enters the next deep treatment stage, and the rest is sent to sludge treatment as residual activated sludge for dehydration and drying.

[0045] Furthermore, the phosphorus release reaction is specifically the anaerobic phosphorus release reaction of polyphosphate bacteria using the carbon source of the incoming water; the excess phosphorus uptake reaction is specifically the absorption of phosphorus by polyphosphate bacteria in excess of its own growth requirements under sufficient oxygen conditions; the nitrification reaction is specifically the conversion of ammonia nitrogen into nitrate nitrogen; and the carbon oxidation reaction is specifically the decomposition of organic matter in sewage by aerobic bacteria under sufficient oxidation conditions.

[0046] Furthermore, the pretreatment specifically includes at least one of grid treatment, sand settling treatment and primary sedimentation treatment.

[0047] When sewage comes to TP i(Total phosphorus in incoming water) and TN i When (total nitrogen in the incoming water) is relatively balanced (such as BOD5 / TP≥17, BOD5 / TN≥4, the data here is only an example, and the present invention is not limited thereto), the phosphorus removal and nitrogen removal balance mode of the present invention can be adopted. The treatment process of the phosphorus removal and nitrogen removal balance mode of the present invention includes:

[0048] The pretreated wastewater of S1 enters the first reaction zone and is mixed with the nitrification liquid refluxed from the third reaction zone to undergo denitrification and phosphorus release reactions. The nitrification liquid reflux ratio is controlled to be 100% to 600% to adjust the ORP of the first reaction zone to -180mv to -50mv;

[0049] The treated liquid S2 after being treated by S1 enters the second reaction zone for a carbon oxidation reaction, an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state;

[0050] The treated liquid S3 after being treated by S2 enters the third reaction zone for secondary carbon oxidation reaction, secondary excess phosphorus uptake reaction and secondary nitrification reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

[0051] S4 separates the solid-liquid mixture of the mud and water in the third reaction zone, and part of the nitrified liquid flows back to the first reaction zone. The supernatant is discharged after detection or enters the next deep treatment stage, and the rest is sent to sludge treatment as residual activated sludge for dehydration and drying.

[0052] Specifically, the phosphorus release reaction refers to the anaerobic phosphorus release reaction of polyphosphate bacteria using the carbon source of the incoming water; the excess phosphorus uptake reaction refers to the absorption of phosphorus by polyphosphate bacteria in excess of its own growth requirements under sufficient oxygen conditions; the nitrification reaction refers to the conversion of ammonia nitrogen into nitrate nitrogen; the carbon oxidation reaction refers to the decomposition of organic matter in sewage by aerobic bacteria under sufficient oxidation conditions; the denitrification reaction refers to the use of organic matter in sewage as electron donors by denitrifying bacteria to reduce nitrate nitrogen into nitrogen gas for discharge.

[0053] Furthermore, the pretreatment specifically includes at least one of grid treatment, sand settling treatment and primary sedimentation treatment.

[0054] When sewage comes to TN i When (total nitrogen in the inlet water) is high (for example, when TNi≥50 mg / L, 50 mg / L here is only an example, and the present invention is not limited thereto), or when the denitrification effect of the effluent is not good, the denitrification priority mode of the present application can be adopted. The treatment process of the denitrification priority mode includes:

[0055] The pre-treated wastewater of S1 enters the first reaction zone and reacts with the nitrification liquid refluxed from the third reaction zone to perform a denitrification. The nitrification liquid reflux ratio is controlled to 100% to 600% to adjust the ORP of the first reaction zone to -180mv to -50mv and the DO to 0 to 0.5mg / L.

[0056] The treated liquid S2 after being treated by S1 enters the second reaction zone for secondary denitrification. The second reaction zone is aerated with a small amount or without aeration to be in anoxic or anaerobic state, and the DO is kept at 0.5 mg / L or below.

[0057] The second reaction zone is aerated with a small amount or without aeration to form an anoxic environment, so that the denitrifying bacteria have more time to use carbon sources to convert NO3 - and NO2 - is reduced to N2.

[0058] S3: The treated liquid after being treated by S2 enters the third reaction zone for carbon oxidation reaction, excessive phosphorus uptake and nitrification reaction, and the third reaction zone is continuously aerated to be in an aerobic state;

[0059] S4 separates the solid-liquid mixture of the mud and water in the third reaction zone, and part of the nitrified liquid flows back to the first reaction zone. The supernatant is discharged after detection or enters the next deep treatment stage, and the rest is sent to sludge treatment as residual activated sludge for dehydration and drying.

[0060] Specifically, the excessive phosphorus uptake reaction refers to the polyphosphate bacteria absorbing phosphorus in excess of their own growth requirements under sufficient oxygen conditions; the nitrification reaction refers to the conversion of ammonia nitrogen into nitrate nitrogen; the carbon oxidation reaction refers to the decomposition of organic matter in sewage by aerobic bacteria under sufficient oxidation conditions; the denitrification reaction refers to the denitrifying bacteria using organic matter in sewage as electron donors to reduce nitrate nitrogen into nitrogen gas for discharge.

[0061] Furthermore, the pretreatment specifically includes at least one of grid treatment, sand settling treatment and primary sedimentation treatment.

[0062] Another aspect of the present invention is to provide a sewage treatment system with multiple operation modes. Figure 2 , the sewage treatment system of the present invention is described in detail.

[0063] The sewage treatment system of the present invention comprises a first reaction zone, a second reaction zone and a third reaction zone.

[0064] The first reaction zone 100 includes a first reaction tank 110, and a first detector group 130 is provided in the first reaction tank 110. The first detector group 130 includes an oxidation-reduction potential meter (not shown in the figure) for detecting the oxidation-reduction potential of the mixed solution in the first reaction tank 110. The first detector group may also include a dissolved oxygen meter (not shown in the figure) for detecting the dissolved oxygen in the first reaction tank 110. A first plug-flow stirring device 120 may also be provided in the first reaction tank 110. A plurality of first plug-flow stirring devices 120 may be provided in the first reaction tank body 110, and specifically, the first plug-flow stirring device 120 may be a flow-propelling device or a stirrer. Of course, the first plug-flow stirring device 120 may also be not provided according to the hydraulic conditions.

[0065] The second reaction zone 200 includes a second reaction tank 210, and a first aeration device 220 and a second detector group 230 are provided in the second reaction tank 210. The first aeration device 220 can be an aerator, and the aerator can have multiple, which are arranged in the second reaction tank. The second detector group 230 includes an oxidation-reduction potential meter (not shown in the figure) for detecting the oxidation-reduction potential of the mixed solution in the second reaction tank 210. The second detector group can also include a dissolved oxygen meter (not shown in the figure) for detecting the dissolved oxygen in the second reaction tank 210. A second plug flow stirring device 240 can also be provided in the second reaction zone 200, and the second plug flow stirring device 240 can be provided with multiple in the second reaction tank 210, and specifically, the second plug flow stirring device 240 can be a plug flow device, and can also be a stirrer. Of course, the second plug flow stirring device 240 can also be not provided according to the hydraulic situation.

[0066] The third reaction zone 300 includes a third reaction tank 310, in which a third detector group 340, a second aeration device 320 and a solid-liquid separation device 330 are arranged. The third detector group 340 includes a dissolved oxygen meter (not shown in the figure) for detecting dissolved oxygen in the third reaction tank 310. The second aeration device 320 can be an aerator, and there can be multiple aerators, which are arranged in the third reaction tank 310. The solid-liquid separation device 330 can be the solid-liquid separation device in CN201911391372.0, or any device in the prior art that uses air lift power to perform solid-liquid separation.

[0067] The first reaction tank 110, the second reaction tank 210 and the third reaction tank 310 are connected in sequence (not shown in the figure). Specifically, the first reaction tank 110, the second reaction tank 210 and the third reaction tank 310 can be connected by pipelines, or can be connected by channels or water holes. A first reflux pipe 410 is connected between the third reaction tank 310 and the first reaction tank 110 to transport the sludge or nitrification liquid in the third reaction tank 310 to the first reaction tank 110.

[0068] The sewage treatment system with multiple operation modes of the present invention further includes a pump room (not shown in the figure), in which a residual sludge pump (not shown in the figure) and a return sludge pump (not shown in the figure) are arranged. The residual sludge pump is used to transport the residual activated sludge to the sludge treatment (not shown in the figure), and the return sludge pump is used to transport part of the nitrification liquid to the first reaction tank 110.

[0069] When the sewage treatment system with multiple operation modes of the present invention is in use, the sewage (i.e., incoming water) treated by the fence enters the first reaction tank 110, the nitrification liquid in the third reaction tank 310 is transported to the first reaction tank 110 through the first reflux pipe 410, the first plug flow stirring device 120 is in an open state, so that the incoming water and the microorganisms and bacteria in the nitrification liquid are fully mixed and reacted, and the ORP and DO of the first reaction tank 110 are detected by the first detector group 130, and the treated liquid treated by the first reaction tank 110 enters the second reaction tank 210 and continues to react and treat in the state where the second plug flow stirring device 240 is turned on, if it is a phosphorus removal priority mode and a phosphorus removal and denitrification balance mode, the first aeration device 220 is turned on in a small amount or not turned on in a denitrification priority mode. The treated liquid treated by the second reaction tank 210 enters the third reaction tank 310, and in the third reaction tank 310, the second aeration device 320 is maintained in an open state to perform an aerobic reaction. The sludge and the supernatant are separated by the solid-liquid separation device 330, and part of the nitrification liquid is returned to the first reaction tank 110. The supernatant (i.e., effluent) is discharged or enters the next deep treatment stage after detection, and the rest is sent to sludge treatment as residual activated sludge (not shown in the figure).

[0070] In order to better illustrate the purpose, technical scheme and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0071] Example 1

[0072] The main process of a factory living area sewage project in Wuhan adopts the phosphorus removal priority mode of this sewage treatment process, controlling MLSS at 2500mg / L~3000mg / L, nitrification liquid reflux ratio of 300%, and ORP of the first reaction tank at <-180mV. The effluent is at an excellent level and meets the Class A standard of "Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB18918-2002)". The TP influent of the sewage is 2.1mg / L~2.5mg / L. In the absence of coagulant (chemical phosphorus removal agent), the effluent index is between 0.09 and 0.13mg / L, which is significantly better than the Class A standard.

[0073] Example 2

[0074] In a project in an industrial zone in Foshan, the raw water is industrial sewage (including some nanofiltration concentrate), and the denitrification priority mode is adopted. By controlling MLSS 3000mg / L~3500mg / L, nitrification liquid reflux ratio 200%, first reaction tank ORP -180mV~-100mV, DO value below 0.2mg / L, the effluent shows excellent level, among which the total nitrogen influent is 25.6mg / L~28.1mg / L, and the effluent is 3.6mg / L~5.6mg / L, which is significantly better than the Level A standard of "Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB18918-2002)".

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A sewage treatment process with multiple operation modes, characterized in that: The invention comprises a first reaction zone, a second reaction zone and a third reaction zone which are used for denitrification and / or dephosphorization of sewage and are performed sequentially. The nitrification liquid treated in the third reaction zone is refluxed to the first reaction zone. The phosphorus removal priority mode, the phosphorus removal and denitrification balanced mode or the nitrogen removal priority mode is switched by controlling the reflux ratio of the nitrification liquid to adjust the ORP and / or DO of the first reaction zone.

2. The sewage treatment process with multiple operation modes according to claim 1, characterized in that: The reflux ratio of the nitrification liquid in the phosphorus removal priority mode is controlled to be 50% to 200% to adjust the ORP of the first reaction zone to -180mv and below, and the second reaction zone is in an aerobic state; the reflux ratio of the nitrification liquid in the phosphorus removal and denitrification balanced mode is controlled to be 100% to 600% to adjust the ORP of the first reaction zone to -180mv to -50mv, and the second reaction zone is in an aerobic state; the reflux ratio of the nitrification liquid in the denitrification priority mode is controlled to be 100% to 600% to adjust the ORP of the first reaction zone to -180mv to -50mv, and the DO is 0 to 0.5mg / L, and the second reaction zone is in anoxic or anaerobic state.

3. The sewage treatment process with multiple operation modes according to claim 2, characterized in that: The treatment process of the phosphorus removal priority mode includes: S1 The pretreated sewage enters the first reaction zone and reacts with the nitrification liquid refluxed from the third reaction zone, and the polyphosphate bacteria release phosphorus in the first reaction zone; S2: the treated liquid after being treated by S1 enters the second reaction zone to undergo an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state; S3: The treated liquid after being treated by S2 enters the third reaction zone for secondary excess phosphorus uptake reaction, secondary nitrification reaction and secondary carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

4. The sewage treatment process with multiple operation modes according to claim 2, characterized in that: The treatment process of the balanced mode of phosphorus removal and nitrogen removal includes: S1 The pretreated sewage enters the first reaction zone and is mixed with the nitrification liquid refluxed from the third reaction zone to undergo denitrification and phosphorus release reactions; S2: the treated liquid after being treated by S1 enters the second reaction zone to undergo a carbon oxidation reaction, an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state; S3: The treated liquid after being treated by S2 enters the third reaction zone for secondary excess phosphorus uptake reaction, secondary nitrification reaction and secondary carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

5. The sewage treatment process with multiple operation modes according to claim 2, characterized in that: The treatment process of the denitrification priority mode includes: S1 The pretreated sewage enters the first reaction zone and reacts with the nitrification liquid refluxed from the third reaction zone to perform a denitrification process; S2 The treated liquid after being treated by S1 enters the second reaction zone for secondary denitrification. The second reaction zone is aerated with a small amount or without aeration to be in anoxic or anoxic state; S3 The treated liquid after being treated by S2 enters the third reaction zone to undergo excessive phosphorus uptake reaction, nitrification reaction and carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state.

6. The sewage treatment process with multiple operation modes according to claim 5, characterized in that: The DO of the second reaction zone is 0.5 mg / L or less.

7. The sewage treatment process with multiple operation modes according to any one of claims 3 to 6, characterized in that: The process also includes S4: separating the mud-water mixture in the third reaction zone into solid and liquid, returning part of the nitrified liquid to the first reaction zone, discharging the supernatant after detection or entering the next deep treatment stage, and sending the rest as residual activated sludge to sludge treatment.

8. The sewage treatment process with multiple operation modes according to claim 7, characterized in that: The pretreatment includes at least one of grid treatment, sand settling treatment and primary sedimentation treatment.

9. A sewage treatment system based on the sewage treatment process with multiple operation modes according to any one of claims 1 to 8, characterized in that: The invention comprises a first reaction zone, a second reaction zone and a third reaction zone, wherein the first reaction zone comprises a first reaction pool, the second reaction zone comprises a second reaction pool, the third reaction zone comprises a third reaction pool, the first reaction pool, the second reaction pool and the third reaction pool are connected in sequence, and a first reflux pipe is connected between the third reaction pool and the first reaction pool.

10. The sewage treatment system with a sewage treatment process having multiple operation modes according to claim 9, characterized in that: The first reaction tank is provided with a first detector group; the second reaction tank is provided with a first aeration device and a second detector group; the third reaction tank is provided with a third detector group, a second aeration device and a solid-liquid separation device.

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