Wastewater treatment process and wastewater treatment system with multiple operating modes

Abstract

This invention provides a wastewater treatment process and system with multiple operating modes, belonging to the field of wastewater treatment technology. It includes a first reaction zone, a second reaction zone, and a third reaction zone, which are used for nitrogen and / or phosphorus removal in sequence. The nitrified liquor treated in the third reaction zone is then returned to the first reaction zone. By controlling the nitrified liquor return ratio to adjust the ORP and / or DO of the first reaction zone, the system can switch between a phosphorus removal priority mode, a balanced phosphorus and nitrogen removal mode, or a nitrogen removal priority mode. This multi-mode wastewater treatment process allows for flexible adjustment and switching of different operating modes within the same wastewater treatment system based on different influent water quality. By controlling the nitrified liquor return ratio to adjust the ORP and / or DO, extremely high biological nitrogen and / or phosphorus removal efficiencies can be achieved, while significantly reducing investment and treatment costs.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and particularly relates to a wastewater treatment process and system with multiple operating modes. Background Technology

[0002] Currently, activated sludge processes are commonly used to treat municipal wastewater. To remove nitrogen and phosphorus, the activated sludge process has been improved into AO and AAO processes. There are two types of AO processes: one is an anaerobic-aerobic process used for phosphorus removal (A... P O), one is the anoxic-aerobic process for denitrification (A N The AAO process (anaerobic / anoxic) is a process that removes both nitrogen and phosphorus. It is currently the most widely used municipal wastewater treatment process, and to balance nitrogen and phosphorus removal, it includes anaerobic, anoxic, and aerobic tanks. The activated sludge in this system is mainly composed of nitrifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria. In the anaerobic zone, polyphosphate-accumulating bacteria release phosphorus and absorb easily degradable organic matter such as lower fatty acids. In the aerobic zone, polyphosphate-accumulating bacteria absorb excess phosphorus, which is removed through the discharge of excess sludge. In the anoxic zone, denitrifying bacteria convert nitrates brought in by internal recirculation into nitrogen gas through biological denitrification, thus achieving nitrogen removal. In the aerobic zone, activated sludge degrades most of the organic matter in the water, and nitrifying bacteria convert ammonia nitrogen in the influent, as well as ammonia nitrogen formed from the ammonification of organic nitrogen, into nitrates through biological nitrification.

[0003] The AAO process has some drawbacks: (1) The operating parameters for phosphorus removal and denitrification include DO, sludge age, and recirculation ratio. There are many control parameters, and these parameters can only be limited to a narrow range and are often contradictory and mutually exclusive. For example, a short sludge age is beneficial for phosphorus removal but detrimental to denitrification, while a long sludge age is beneficial for denitrification but detrimental to phosphorus removal. (2) The AAO process involves biological treatment and sedimentation separation. The sludge returned from sedimentation is used for anaerobic phosphorus release in the A section to enhance phosphorus removal; the anoxic section is used for mixed liquor recirculation to enhance denitrification. The AAO process system has both sludge recirculation and anoxic mixed liquor recirculation, and some variants of the AAO process even have multiple recirculations. Since sludge recirculation needs to take into account both the MLSS (sludge concentration) of the entire system and the ORP value required for anaerobic phosphorus removal, it is sometimes difficult to achieve both simultaneously, making the process and control more complex. (3) The AAO process and its variants (such as UCT, Bardenpho process, etc.) include at least the following structures: anaerobic tank, anoxic tank, aerobic tank, secondary sedimentation tank, and return pump station. For some AAO variants or optimized processes (such as UCT, Bardenpho process, etc.), there will also be several anaerobic tanks or anoxic tanks, multiple return processes, etc., which increases the complexity of the process.

[0004] In addition to the above-mentioned drawbacks, the water quality of wastewater varies in different seasons or from different sources. Therefore, different requirements have emerged for wastewater treatment based on different water qualities. For example, for wastewater with high total phosphorus and total nitrogen content but low carbon source, phosphorus removal and denitrification often cannot be achieved simultaneously. In order to enhance phosphorus removal or denitrification, various modified AAO processes (such as UCT process and bardenpho process) are required, which have disadvantages such as many treatment structures, large volume, and complicated processes.

[0005] The core of activated sludge systems in wastewater treatment lies in utilizing non-aerated sludge under specific conditions to achieve phosphorus and nitrogen removal: phosphorus is released by the sludge in the anaerobic zone; and nitrate nitrogen is removed in the anoxic zone. Current AAO (Anaerobic-Oxygen-Acid) technologies typically separate these two zones spatially, employing sludge recirculation and nitrification liquor recirculation to achieve their respective functions.

[0006] Currently, there is a lack of phosphorus and nitrogen removal methods on the market specifically designed for this technological innovation. Most still rely on separate phosphorus and nitrogen removal processes in different zones. To achieve a more efficient and simpler phosphorus and nitrogen removal process and meet increasingly stringent environmental protection requirements, there is an urgent need for a wastewater treatment technology that is highly efficient, easy to operate, and saves land to address the current challenges. Summary of the Invention

[0007] The purpose of this invention is to provide a wastewater treatment process and system with multiple operating modes. Within the same wastewater treatment system, different operating modes can be flexibly adjusted and switched according to different influent water quality. By controlling the nitrification liquor return ratio and adjusting ORP and / or DO, extremely high biological denitrification and / or biological phosphorus removal efficiency can be obtained, and investment and treatment costs can be greatly reduced.

[0008] To achieve the above objectives, the present invention provides a wastewater treatment process with multiple operating modes, including a first reaction zone, a second reaction zone, and a third reaction zone for denitrification and / or phosphorus removal of wastewater, which are carried out sequentially. The nitrified liquid treated in the third reaction zone is then returned to the first reaction zone. By controlling the nitrified liquid return ratio to adjust the ORP and / or DO of the first reaction zone, the phosphorus removal priority mode, the phosphorus and nitrogen removal balance mode, or the nitrogen removal priority mode can be switched.

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

[0010] As a preferred technical solution, the phosphorus removal priority mode processing technology of the present invention includes: S1 The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone. Polyphosphate-accumulating bacteria carry out phosphorus release reaction in the first reaction zone. The treated liquid after S1 enters the second reaction zone to carry out an excess phosphorus uptake reaction, a nitration reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state. The treated liquid after S2 enters the third reaction zone for a secondary excess phosphorus uptake reaction, a secondary nitrification reaction, and a secondary carbon oxidation reaction. The third reaction zone is continuously aerated to maintain an aerobic state.

[0011] As a preferred technical solution, the phosphorus and nitrogen removal balanced mode treatment process of the present invention includes: S1 The pretreated wastewater enters the first reaction zone and mixes with the nitrification liquid returned from the third reaction zone to carry out denitrification and phosphorus release reactions; The treated liquid after S1 enters the second reaction zone to carry out one carbon oxidation reaction, one excess phosphorus uptake reaction, one nitration reaction and one carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state. The treated liquid after S2 enters the third reaction zone for secondary carbon oxidation, secondary excess phosphorus uptake and secondary nitrification, and the third reaction zone is continuously aerated to maintain an aerobic state.

[0012] As a preferred technical solution, the denitrification priority mode processing method of the present invention includes: S1 The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone to carry out one denitrification. The treated liquid from S1 enters the second reaction zone for secondary denitrification. The second reaction zone is partially aerated or not aerated to maintain an anaerobic or facultative-anaerobic state, allowing the denitrifying bacteria more time to utilize the carbon source to denitrify NO3-. - and NO2 - It was reduced to N2; The treated liquid after S2 enters the third reaction zone to undergo one excess phosphorus uptake, one nitration reaction, and one carbon oxidation reaction. The third reaction zone is continuously aerated to maintain an aerobic state.

[0013] Specifically, the DO in the second reaction zone is 0.5 mg / L or less.

[0014] As a preferred technical solution, the wastewater treatment process of the present invention further includes S4: solid-liquid separation of the mud-water mixture in the third reaction zone, partial nitrification liquid being returned to the first reaction zone, supernatant being discharged after detection or entering the next deep treatment stage, and the remainder being sent to sludge treatment as residual activated sludge.

[0015] 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.

[0016] Another aspect of the present invention provides a wastewater 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, and 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 return pipe is connected between the third reaction tank and the first reaction tank.

[0017] As a preferred technical solution, the first reaction tank is equipped with a first detection instrument group; the second reaction tank is equipped with a first aeration device and a second detection instrument group; and the third reaction tank is equipped with a third detection instrument group, a second aeration device, and a solid-liquid separation device.

[0018] Compared with existing technologies, this invention is an innovative AO technology coupling biological treatment and sedimentation. Its unique feature lies in its use of only nitrification liquor recirculation, eliminating the traditional sludge recirculation. By controlling the nitrification liquor recirculation ratio, nitrogen and phosphorus removal can be efficiently achieved. This simplified system control not only reduces land use and energy consumption but also significantly enhances system stability. Therefore, this technology is widely applicable to various wastewater treatment and sewage treatment scenarios, demonstrating enormous application potential and environmental benefits. Its specific beneficial effects include: (1) Simultaneous phosphorus release and denitrification can be achieved in the first reaction tank. The principle is as follows: ① In an anaerobic environment, facultative anaerobic fermentation bacteria convert biodegradable organic matter in wastewater into low-molecular-weight fermentation intermediates such as volatile fatty acids (VFA), providing the necessary material basis for phosphorus release and denitrification; ② Polyphosphate 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, reducing the nitrate to nitrogen gas, thereby achieving the purpose of denitrification; ④ This invention utilizes the difference between the internal and external conditions of the activated sludge system to achieve simultaneous anaerobic phosphorus release and denitrification: the activated sludge has a better anaerobic environment, which is conducive to the phosphorus release reaction of polyphosphate bacteria; the activated sludge surface has a better anoxic environment, which is conducive to the denitrification reaction of denitrifying bacteria. ⑤ The above reaction conditions only require maintaining the oxidation-reduction potential (ORP) and / or dissolved oxygen (DO) of the first reaction tank to achieve simultaneous phosphorus release and nitrogen removal. Similarly, by adjusting the oxidation-reduction potential (ORP) and / or dissolved oxygen (DO) of the first reaction tank, phosphorus removal or nitrogen removal can be prioritized.

[0019] (2) The wastewater treatment process of the present invention has three operating modes: phosphorus removal priority, phosphorus and nitrogen removal balance, and nitrogen removal priority. It can be flexibly adjusted according to the different influent water quality and different operating modes can be adopted. By controlling the nitrification liquid reflux ratio to control the oxidation-reduction potential (ORP) and / or dissolved oxygen (DO), extremely high biological nitrogen removal effect and / or biological phosphorus removal effect can be achieved, and investment and treatment costs can be greatly reduced.

[0020] (3) The wastewater treatment system of the present invention includes a first reaction tank, a second reaction tank and a third reaction tank connected in sequence. The process flow is simple and saves land. Wastewater can be biologically dephosphorized and / or denitrified in these three reaction tanks by controlling the nitrification liquid reflux ratio and can meet the treatment standards.

[0021] (4) An aeration device is installed in the second reaction tank, which can be used as an anaerobic / anoxic tank or an aerobic tank depending on the quality of the influent water, thereby achieving targeted biological phosphorus removal and / or denitrification.

[0022] (5) A solid-liquid separation device is installed in the third reaction tank. The sludge and supernatant can be separated by the solid-liquid separation device. The solid-liquid separation device is installed in the third reaction tank, which eliminates the need for the secondary sedimentation tank, saves land, and also shortens the process flow of sewage treatment.

[0023] (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 land area and making the land utilization rate higher; Second, the present invention only uses nitrification liquid recirculation, eliminating the complex sludge recirculation system, which not only simplifies the entire treatment process, but also makes the control method more flexible and efficient.

[0024] (7) Compared with the inverted AAO process: The inverted AAO process is designed for better denitrification by returning a large flow of sludge to the anoxic tank, where denitrifying bacteria utilize high-quality carbon sources for denitrification. However, this process can lead to poor phosphorus removal and subsequent sedimentation. In contrast, this invention can achieve better denitrification by using a denitrification priority mode, without sludge return, and without affecting the sedimentation effect.

[0025] (8) Compared with the integrated process of oxidation ditch and secondary sedimentation tank: the plug flow state of oxidation ditch causes significant disturbance to the water distribution and sedimentation in 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 air lift power for solid-liquid separation) performs solid-liquid separation through air lift power, with clear flow lines for water distribution and sedimentation, and excellent sedimentation effect. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the wastewater treatment process with multiple operating modes according to the present invention; Figure 2 This is a schematic diagram of the wastewater treatment system with multiple operating modes according to the present invention.

[0027] In the attached diagram, 100-first reaction zone, 110-first reaction tank, 120-first stirring device, 130-first detection instrument group, 200-second reaction zone, 210-second reaction tank, 220-first aeration device, 230-second detection instrument, 240-second stirring device, 300-third reaction zone, 310-third reaction tank, 320-second aeration device, 330-solid-liquid separation device, 340-third detection instrument group, 410-first return pipe. Detailed Implementation

[0028] This invention provides a wastewater treatment process with multiple operating modes, including a first reaction zone, a second reaction zone, and a third reaction zone for wastewater denitrification and / or phosphorus removal, which proceed sequentially. The nitrified liquor treated in the third reaction zone is then returned to the first reaction zone. The phosphorus removal priority mode, the balanced phosphorus and nitrogen removal mode, or the denitrification priority mode are switched by controlling the nitrified liquor return ratio to adjust the ORP and / or DO of the first reaction zone. The following is a related description... Figure 1The specific processes of the phosphorus removal priority mode, the phosphorus removal and nitrogen removal equilibrium mode, and the nitrogen removal priority mode are described in detail.

[0029] When the TP of the sewage inflow i When the total phosphorus content in the influent is high, such as TPi ≥ 4 mg / L (4 mg / L is just one example and is not a limitation of this invention), or when it is desirable to reduce the dosage of chemical agents and enhance the biological phosphorus removal effect, the phosphorus removal priority mode of this invention can be adopted. The treatment process of the phosphorus removal priority mode of this invention includes: S1 The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone. Polyphosphate-accumulating bacteria carry out phosphorus release reaction in the first reaction zone. The return ratio is controlled at 50%~200% to adjust the ORP of the first reaction zone to -180mv and below. The treated liquid after S1 enters the second reaction zone to carry out an excess phosphorus uptake reaction, a nitrification reaction and a carbon oxidation reaction. The second reaction zone is continuously aerated to maintain an aerobic state. The treated liquid after S2 enters the third reaction zone for a secondary excess phosphorus uptake reaction, a secondary nitrification reaction, and a secondary carbon oxidation reaction. The third reaction zone is continuously aerated to maintain an aerobic state. S4 performs solid-liquid separation on the mud-water mixture in the third reaction zone. Part of the nitrification liquid is returned to the first reaction zone, and the supernatant is either discharged after testing or enters the next deep treatment stage. The remainder is sent to the sludge treatment plant as residual activated sludge for dewatering and drying.

[0030] Furthermore, the phosphorus release reaction specifically involves polyphosphate-accumulating bacteria using the carbon source in the incoming water for anaerobic phosphorus release; the excess phosphorus uptake reaction specifically involves polyphosphate-accumulating bacteria absorbing more phosphorus than they need for growth under sufficient oxygen conditions; the nitrification reaction specifically involves converting ammonia nitrogen into nitrate nitrogen; and the carbon oxidation reaction specifically involves aerobic bacteria decomposing organic matter in wastewater under sufficient oxidation conditions.

[0031] Furthermore, the pretreatment specifically includes at least one of the following: bar screen treatment, sand settling treatment, and initial sedimentation treatment.

[0032] When the TP of the sewage inflow i (Total phosphorus in incoming water) and TN i When the total nitrogen content of the incoming water is relatively balanced (e.g., BOD5 / TP ≥ 17, BOD5 / TN ≥ 4; this data is only one example and is not limited to this invention), the phosphorus and nitrogen removal balanced mode of this invention can be adopted. The treatment process of the phosphorus and nitrogen removal balanced mode of this invention includes: S1 The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone to carry out denitrification and phosphorus release reactions. The nitrified liquid return ratio is controlled at 100%~600% to adjust the ORP of the first reaction zone to -180mv~-50mv. The treated liquid after S1 enters the second reaction zone to carry out one carbon oxidation reaction, one excess phosphorus uptake reaction, one nitration reaction and one carbon oxidation reaction. The second reaction zone is continuously aerated to maintain an aerobic state. The treated liquid after S2 enters the third reaction zone for secondary carbon oxidation, secondary excess phosphorus uptake and secondary nitrification. The third reaction zone is continuously aerated to maintain an aerobic state.

[0033] S4 performs solid-liquid separation on the mud-water mixture in the third reaction zone. Part of the nitrification liquid is returned to the first reaction zone, and the supernatant is either discharged after testing or enters the next deep treatment stage. The remainder is sent to the sludge treatment plant as residual activated sludge for dewatering and drying.

[0034] Specifically, the phosphorus release reaction is an anaerobic phosphorus release reaction in which polyphosphate-accumulating bacteria use the carbon source of the incoming water; the excess phosphorus uptake reaction is in which polyphosphate-accumulating bacteria absorb more phosphorus than they need for growth under sufficient oxygen conditions; the nitrification reaction is in which ammonia nitrogen is converted into nitrate nitrogen; the carbon oxidation reaction is in which aerobic bacteria decompose organic matter in wastewater under sufficient oxidation conditions; and the denitrification reaction is in which denitrifying bacteria use organic matter in wastewater as an electron donor to reduce nitrate nitrogen into nitrogen gas and release it.

[0035] Furthermore, the pretreatment specifically includes at least one of the following: bar screen treatment, sand settling treatment, and initial sedimentation treatment.

[0036] When the TN of the sewage inflow i When the total nitrogen (TNi) in the influent is high (e.g., TNi ≥ 50 mg / L, where 50 mg / L is just one example and is not a limitation of this invention), or when the denitrification effect of the effluent is poor, the denitrification priority mode of this application can be adopted. The treatment process of the denitrification priority mode includes: S1 The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone to carry out one denitrification. The nitrified liquid return ratio is controlled at 100%~600% to adjust the ORP of the first reaction zone to -180mv~-50mv and DO to 0~0.5mg / L. The treated liquid after S1 enters the second reaction zone for secondary denitrification. The second reaction zone is aerated in small amounts or not at all to be in anoxic or facultative anaerobic state, and the DO is kept at 0.5 mg / L or below. The second reaction zone is aerated only slightly or not at all to create an anaerobic environment, allowing denitrifying bacteria more time to utilize the carbon source to convert NO3.- and NO2 - It was reduced to N2.

[0037] The treated liquid after S2 enters the third reaction zone for carbon oxidation, excess phosphorus uptake and nitration. The third reaction zone is continuously aerated to maintain an aerobic state. S4 separates the sludge-water mixture in the third reaction zone into solid and liquid components. Part of the nitrification liquid is returned to the first reaction zone, and the supernatant is either discharged after testing or enters the next deep treatment stage. The remainder is sent to the sludge treatment plant as residual activated sludge for dewatering and drying.

[0038] Specifically, the excess phosphorus uptake reaction is the process by which polyphosphate-accumulating bacteria absorb more phosphorus than they need for growth under sufficient oxygen conditions; the nitrification reaction is the conversion of ammonia nitrogen into nitrate nitrogen; the carbon oxidation reaction is the decomposition of organic matter in wastewater by aerobic bacteria under sufficient oxidizing conditions; and the denitrification reaction is the process by which denitrifying bacteria use organic matter in wastewater as an electron donor to reduce nitrate nitrogen into nitrogen gas, which is then released.

[0039] Furthermore, the pretreatment specifically includes at least one of the following: bar screen treatment, sand settling treatment, and initial sedimentation treatment.

[0040] In another aspect, the present invention also provides a wastewater treatment system with multiple operating modes. (Specifically combined with...) Figure 2 The wastewater treatment system of the present invention will be described in detail below.

[0041] The wastewater treatment system of the present invention includes a first reaction zone, a second reaction zone, and a third reaction zone.

[0042] The first reaction zone 100 includes a first reaction tank 110, within which a first detection instrument group 130 is installed. The first detection instrument group 130 includes a redox potential meter (not shown in the figure) for detecting the redox potential of the mixture within the first reaction tank 110. The first detection instrument group may also include a dissolved oxygen meter (not shown in the figure) for detecting dissolved oxygen within the first reaction tank 110. A first flow-propelling and stirring device 120 may also be installed within the first reaction tank 110. Multiple first flow-propelling and stirring devices 120 may be installed within the first reaction tank 110. Specifically, the first flow-propelling and stirring device 120 may be a flow promoter or a stirrer. Alternatively, depending on the hydraulic conditions, a first flow-propelling and stirring device 120 may not be installed.

[0043] The second reaction zone 200 includes a second reaction tank 210, which is equipped with a first aeration device 220 and a second detection instrument group 230. The first aeration device 220 can be an aerator, and there can be multiple aerators arranged in the second reaction tank. The second detection instrument group 230 includes a redox potential meter (not shown in the figure) for detecting the redox potential of the mixed solution in the second reaction tank 210. The second detection instrument group may also include a dissolved oxygen meter (not shown in the figure) for detecting the dissolved oxygen in the second reaction tank 210. A second flow-promoting and stirring device 240 may also be provided in the second reaction zone 200. Multiple second flow-promoting and stirring devices 240 may be provided in the second reaction tank 210. Specifically, the second flow-promoting and stirring device 240 can be a flow promoter or a stirrer. Of course, the second flow-promoting and stirring device 240 may not be provided depending on the hydraulic conditions.

[0044] The third reaction zone 300 includes a third reaction tank 310, which is equipped with a third detection instrument group 340, a second aeration device 320, and a solid-liquid separation device 330. The third detection instrument 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 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 existing device that uses airlift power for solid-liquid separation.

[0045] The first reaction tank 110, the second reaction tank 210, and the third reaction tank 310 are connected sequentially (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 a pipe, or by a water channel or a water passage. A first return pipe 410 is connected between the third reaction tank 310 and the first reaction tank 110, which is used to transport the sludge or nitrification liquid in the third reaction tank 310 to the first reaction tank 110.

[0046] The wastewater treatment system with multiple operating modes of the present invention also includes a pump house (not shown in the figure), which is equipped with a waste sludge pump (not shown in the figure) and a return sludge pump (not shown in the figure). The waste sludge pump is used to transport the remaining 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.

[0047] In this invention, a wastewater treatment system with multiple operating modes is used. Wastewater (i.e., incoming water) after being treated by a screen enters the first reaction tank 110. Nitrified liquid from the third reaction tank 310 is transported to the first reaction tank 110 via the first return pipe 410. The first agitator 120 is turned on, allowing the incoming water and the microorganisms in the nitrified liquid to fully mix and react. The first detection instrument group 130 monitors the ORP and DO of the first reaction tank 110. The treated liquid from the first reaction tank 110 enters the second reaction tank 210, where the second agitator 240 continues to react. In the phosphorus removal priority mode and the phosphorus and nitrogen removal balanced mode, the first aeration device 220 is turned on; in the nitrogen removal priority mode, the first aeration device 220 is turned on only slightly or not at all. The treated liquid from the second reaction tank 210 enters the third reaction tank 310, where the second aeration device 320 is kept on for aerobic reaction. The sludge and supernatant are separated by a solid-liquid separation device 330. 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 testing. The rest is sent to the sludge treatment as residual activated sludge (not shown in the figure).

[0048] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0049] Example 1 The main process of the wastewater treatment project in the residential area of ​​a factory in Wuhan adopts the phosphorus-priority mode of this wastewater treatment process, controlling MLSS at 2500mg / L~3000mg / L, nitrification liquor recirculation ratio at 300%, and ORP in the first reaction tank at <-180mV. The effluent exhibits excellent performance, meeting the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB18918-2002)". The influent TP of this wastewater is 2.1mg / L~2.5mg / L. Without the addition of coagulants (chemical phosphorus removal agents), the effluent index is between 0.09~0.13mg / L, which is significantly better than the Class A standard.

[0050] Example 2 A project in an industrial park in Foshan uses industrial wastewater (containing some nanofiltration concentrate) as raw water. A denitrification priority mode is adopted. By controlling MLSS at 3000mg / L~3500mg / L, nitrification liquor recirculation ratio at 200%, ORP in the first reaction tank at -180mV~-100mV, and DO value below 0.2mg / L, the effluent exhibits excellent levels. Specifically, total nitrogen in the influent is 25.6mg / L~28.1mg / L, and in the effluent it is 3.6mg / L~5.6mg / L, significantly exceeding the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB18918-2002)".

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A wastewater treatment process with multiple operating modes, characterized in that, It includes a first reaction zone, a second reaction zone, and a third reaction zone for denitrification and / or phosphorus removal of wastewater, which are carried out sequentially. The nitrified liquid treated in the third reaction zone is then returned to the first reaction zone. The phosphorus removal priority mode, the phosphorus and nitrogen removal balance mode, or the denitrification priority mode are switched by controlling the nitrified liquid return ratio to adjust the ORP and / or DO of the first reaction zone. In the phosphorus removal priority mode, the nitrification liquor reflux ratio is controlled at 50%~200% to adjust the ORP of the first reaction zone to -180mV or below, and the second reaction zone is in an aerobic state; in the phosphorus removal and nitrogen removal equilibrium mode, the nitrification liquor reflux ratio is controlled at 100%~600% to adjust the ORP of the first reaction zone to -180mV~-50mV, and the second reaction zone is in an aerobic state; in the nitrogen removal priority mode, the nitrification liquor reflux ratio is controlled at 100%~600% to adjust the ORP of the first reaction zone to -180mV~-50mV, DO to 0~0.5mg / L, and the second reaction zone is in anoxic or facultative anoxic state; The phosphorus removal priority mode processing technology includes: A1. The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone. Polyphosphate-accumulating bacteria carry out phosphorus release reaction in the first reaction zone. A2. The treated liquid after A1 enters the second reaction zone to carry out an excess phosphorus uptake reaction, a nitration reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state. A3. The treated liquid after A2 enters the third reaction zone for a second excess phosphorus uptake reaction, a second nitrification reaction and a second carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state. The phosphorus and nitrogen removal balanced mode treatment process includes: B1. The pretreated wastewater enters the first reaction zone and mixes with the nitrification liquid returned from the third reaction zone to carry out denitrification and phosphorus release reactions; B2. The treated liquid after B1 enters the second reaction zone to carry out an excess phosphorus uptake reaction, a nitration reaction and a carbon oxidation reaction, and the second reaction zone is continuously aerated to be in an aerobic state. B3. The treated liquid after B2 enters the third reaction zone for a second excess phosphorus uptake reaction, a second nitrification reaction and a second carbon oxidation reaction, and the third reaction zone is continuously aerated to be in an aerobic state. The denitrification priority mode processing technology includes: C1. The pretreated wastewater enters the first reaction zone and mixes with the nitrified liquid returned from the third reaction zone to undergo one denitrification process. C2. The treated liquid after C1 enters the second reaction zone for secondary denitrification. The second reaction zone is aerated with a small amount or not at all to be in a hypoxic or facultative anaerobic state. C3. The treated liquid after C2 treatment enters the third reaction zone for excess phosphorus uptake, nitration and carbon oxidation reactions, and the third reaction zone is continuously aerated to maintain an aerobic state.

2. The wastewater treatment process with multiple operating modes according to claim 1, characterized in that, In the denitrification priority mode of the treatment process, the DO in the second reaction zone is 0.5 mg / L or less.

3. The wastewater treatment process with multiple operating modes according to any one of claims 1 to 2, characterized in that, It also includes S4: performing solid-liquid separation on the mud-water mixture in the third reaction zone, returning part of the nitrification liquid to the first reaction zone, discharging the supernatant after detection or entering the next deep treatment stage, and sending the remainder as residual activated sludge to sludge treatment.

4. The wastewater treatment process with multiple operating modes according to claim 3, characterized in that, The pretreatment includes at least one of bar screen treatment, sand settling treatment, and initial sedimentation treatment.

5. The wastewater treatment process with multiple operating modes according to claim 1, characterized in that, The wastewater treatment system used in the wastewater treatment process with multiple operating modes includes 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, and 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 return pipe connects the third reaction tank to the first reaction tank.

6. The wastewater treatment process with multiple operating modes according to claim 5, characterized in that, The first reaction tank is equipped with a first detection instrument group; the second reaction tank is equipped with a first aeration device and a second detection instrument group; the third reaction tank is equipped with a third detection instrument group, a second aeration device and a solid-liquid separation device.

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