A wastewater treatment process, control system and control method for nitrogen and phosphorus removal

Abstract

The present application relates to a sewage treatment process, control system and control method for denitrification and phosphorus removal, belonging to the technical field of sewage treatment, and the sewage treatment process includes: a first water inlet pipeline, connected with a first electric butterfly valve; a second water inlet pipeline, connected with a second electric butterfly valve; a front anoxic tank, the water inlet is connected with the first water inlet pipeline; an anaerobic tank, the water inlet is connected with the water outlet of the front anoxic tank and the second water inlet pipeline respectively; an aerobic tank, the water inlet is connected with the water outlet of the anaerobic tank; a membrane tank, the water inlet is connected with the water outlet of the aerobic tank; a water production pump, the water inlet is connected with the water outlet of the membrane tank; a residual sludge pump is connected with the mud outlet opened at the bottom of the membrane tank; a nitrification liquid reflux pump, the water inlet is connected with the water outlet of the aerobic tank, and the water outlet is connected with the water inlet of the front anoxic tank; a sludge reflux pump, the water inlet is connected with the membrane tank, and the water outlet is connected with the water inlet of the aerobic tank. The present application has the beneficial effect of realizing sewage denitrification and phosphorus removal with low consumption and stability.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a sewage treatment process, a control system and a control method for nitrogen and phosphorus removal. Background Art

[0002] In the process of rapid global economic development, the composition of municipal sewage and industrial wastewater has become more complex. Sewage rich in nitrogen and phosphorus enters the sewage treatment system, which continuously impacts the tolerance load of traditional sewage treatment processes. At the same time, with the further deepening of the domestic concept of environmental protection, the standards for sewage discharge have become more and more stringent on water quality. As a relatively mature microbial treatment process in recent years, the membrane bioreactor (MBR) process has been widely used in the treatment of various municipal and industrial wastewaters. Due to its high activated sludge concentration, the MBR process has the characteristics of less residual sludge and strong resistance to sewage quality changes.

[0003] The MBR process has evolved into various forms under different water quality standards, such as the "AO+MBR" process with nitrogen and carbon removal as the goal, the "AAO+MBR" process with nitrogen and phosphorus removal as the goal, and the "AAOA+MBR" process with enhanced nitrogen removal. It can be seen that the current water treatment process is still distorted with "denitrification" as the core, while ignoring the role of the process in phosphorus removal. After engineering and laboratory test calculations, the phosphorus removal effect in the MBR process system is only close to 30%, but through process improvement or system control, the phosphorus removal effect can be increased to about 50%, which will significantly reduce the addition of phosphorus removal agents, and long-term operation can greatly reduce operating costs.

[0004] In the industrial field, such as coking, petrochemical, pharmaceutical, and food wastewater, the water quality after the industrial park sewage treatment meets the minimum requirements of municipal sewage treatment, but the produced water still has unique characteristics in the field. The high content of phosphorus and the low carbon-nitrogen ratio make the downstream sewage treatment more difficult. Therefore, in the low carbon-nitrogen ratio water inlet area, a sewage treatment process and process control method with low consumption and stable nitrogen and phosphorus removal is urgently needed. Summary of the invention

[0005] In order to achieve low-cost and stable denitrification and phosphorus removal in sewage, the present application provides a sewage treatment process for denitrification and phosphorus removal and a process control method.

[0006] In the first aspect, the present application provides a wastewater treatment process for nitrogen and phosphorus removal, which adopts the following technical scheme:

[0007] A wastewater treatment process for nitrogen and phosphorus removal, comprising:

[0008] The first water inlet pipe is connected to a first electric butterfly valve;

[0009] The second water inlet pipe is connected to a second electric butterfly valve;

[0010] A front anoxic tank, the water inlet of which is connected to the first water inlet pipe;

[0011] An anaerobic tank, the water inlet of which is respectively connected with the water outlet of the front anoxic tank and the second water inlet pipe;

[0012] an aerobic tank, the water inlet of which is connected to the water outlet of the anaerobic tank;

[0013] A membrane tank, the water inlet of which is connected to the water outlet of the aerobic tank;

[0014] A water production pump, the water inlet of which is connected with the water outlet of the membrane pool;

[0015] A residual sludge pump is connected to the sludge outlet opened at the bottom of the membrane tank;

[0016] A nitrification liquid reflux pump, whose water inlet is connected to the water outlet of the aerobic tank, and whose water outlet is connected to the water inlet of the front anoxic tank; a sludge reflux pump, whose water inlet is connected to the membrane tank, and whose water outlet is connected to the water inlet of the aerobic tank.

[0017] By adopting the above technical scheme, the water inlet distribution mode of the main water treatment process is a double-point water inlet mode: that is, a part of the raw water flows from the first water inlet pipe to the front anoxic tank, and the water inlet ratio is controlled at 50-70%; the remaining part flows from the second water inlet pipe to the anaerobic tank, and the water inlet ratio is controlled at 30-50%; the ratio of the double-point water inlet is adjusted by the first electric butterfly valve and the second electric butterfly valve; in the front anoxic tank, the organic matter in the sewage is mixed with the nitrification liquid returned from the aerobic tank, and the activated sludge uses the nitrate provided by the nitrification liquid as an electron donor for denitrification; part of the sewage is acidified in the anaerobic tank, and a large amount of VFA is formed in the water, which is convenient for polyphosphate bacteria (such as PAOs and DPBs) to absorb and form poly-β-hydroxybutyric acid (PHB) in the cell, and release a large amount of inorganic phosphate (PO4 3- -P); in the aerobic pool, nitrifying bacteria use oxygen and ammonia nitrogen in the water to nitrify, and aerobic polyphosphate bacteria begin to over-enrich phosphorus in the form of polyphosphates, and finally enter the membrane pool to produce water through the module, so that under the action of the water production pump, the produced water is discharged by suction; since the main water treatment process requires regular sludge discharge, the residual sludge pump is connected through a pipeline to pump the sludge in the membrane pool to the sludge pool;

[0018] In addition, the main water treatment process also has internal reflux, in which the sludge mixture of the aerobic tank flows to the water inlet end of the front anoxic tank through the internal reflux pipeline and mixes with the water in the first water inlet pipeline, and the reflux flow is regulated by the nitrification liquid reflux pump; the main water treatment process also has external reflux, in which the sludge mixture of the membrane tank flows to the front end of the aerobic tank through the external reflux pipeline and mixes with the effluent of the anaerobic tank, and the reflux flow is regulated by the sludge reflux pump;

[0019] Because the process flow has absorbed both the excellent denitrification characteristics of inverted AAO and the idea of ​​double sludge treatment, the separation characteristics of denitrification and phosphorus removal based on sludge age have been realized, allowing aerobic polyphosphate bacteria (PAOs) and denitrifying polyphosphate bacteria (DPBs) to completely experience the anaerobic-aerobic / anoxic environment; therefore, it can achieve low-cost and stable denitrification and phosphorus removal in sewage.

[0020] Optionally, the sewage treatment process further comprises:

[0021] The water inlet of the post-anoxic tank is communicated with the water outlet of the aerobic tank, and the water outlet is communicated with the water inlet of the membrane tank.

[0022] By adopting the above technical scheme, in the post-anoxic tank, the oligotrophic environment causes some microorganisms to undergo endogenous respiration, and some denitrifying bacteria and denitrifying polyphosphate bacteria begin to play a role in the facultative anaerobic environment. The nitrogen removal and phosphorus removal effect of the process will be further improved, and the effluent quality will be further stabilized.

[0023] Optionally, the sewage treatment process further comprises:

[0024] A dosing device, used for adding a dephosphorizing agent into the aerobic tank and a carbon source into the post-anoxic tank;

[0025] The dosing device comprises:

[0026] There are two reagent barrels, which are used to contain the dephosphorizing agent and the carbon source respectively;

[0027] There are two metering and dosing pumps, which are connected to the corresponding medicine barrels respectively and are used to pump the medicine into the corresponding pools.

[0028] By adopting the above technical solution, the denitrification and phosphorus removal effects of the main water treatment process can be further improved.

[0029] In the second aspect, the present application provides a wastewater treatment control system for nitrogen removal and phosphorus removal, which adopts the following technical scheme: a wastewater treatment control system for nitrogen removal and phosphorus removal, based on the above-mentioned wastewater treatment process, comprising:

[0030] A first nitrate nitrogen detector is disposed in the front anoxic tank and is used to monitor the nitrate nitrogen concentration in the front anoxic tank;

[0031] an ammonia nitrogen detector, arranged in the front anoxic tank, for detecting the ammonia nitrogen concentration in the front anoxic tank;

[0032] A first ORP detector is disposed in the front anoxic tank and is used to monitor the redox potential of the front anoxic tank;

[0033] A second ORP detector is disposed in the anaerobic tank and is used to monitor the redox potential of the anaerobic tank;

[0034] A second nitrate nitrogen detector is disposed in the aerobic tank and is used to monitor the nitrate nitrogen concentration in the aerobic tank;

[0035] A DO detector is arranged in the aerobic tank and is used to monitor the dissolved oxygen concentration in the aerobic tank;

[0036] The MLSS detector is arranged in the membrane pool and is used to monitor the activated sludge concentration in the membrane pool.

[0037] By adopting the above technical solution, the sewage treatment process can be monitored.

[0038] Optionally, the sewage treatment control system further includes:

[0039] The flow meters are respectively installed on the first water inlet pipe, the second water inlet pipe, the nitrification liquid return pipe, the sludge return pipe and the dosing pipe, and are used to detect the flow of the corresponding pipes.

[0040] By adopting the above technical solution, the sewage treatment process is further monitored.

[0041] Optionally, the sewage treatment process control system further includes:

[0042] An intelligent monitoring module, for acquiring and monitoring a flow data set; the flow data set includes flow information of the first water inlet pipe, the second water inlet pipe, the dosing pipe, the nitrification liquid return pipe and the sludge return pipe; and redox potential information of the front anoxic tank and the anaerobic tank, nitrate nitrogen concentration information of the front anoxic tank and the aerobic tank, ammonia nitrogen concentration information of the front anoxic tank, dissolved oxygen concentration information of the aerobic tank and activated sludge concentration information of the membrane tank;

[0043] An intelligent control module controls the actions of the first electric butterfly valve, the second electric butterfly valve, the nitrification liquid reflux pump, the sludge reflux pump, the produced water pump, the excess sludge pump, and the dosing device based on the flow data set;

[0044] The intelligent decision-making module, based on the traffic data set, issues an early warning prompt when the data is abnormal.

[0045] By adopting the above technical solution, the automatic treatment of sewage in the online sewage treatment process can be realized.

[0046] In the third aspect, the present application provides a wastewater treatment process control method for nitrogen and phosphorus removal, which adopts the following technical solution:

[0047] A sewage treatment process control method for nitrogen and phosphorus removal, based on the above-mentioned sewage treatment process control system, comprises:

[0048] Obtaining a first actual redox potential of the front anoxic tank, a second actual redox potential of the anaerobic tank, an actual dissolved oxygen concentration of the aerobic tank, and an actual activated sludge concentration of the membrane tank;

[0049] Respectively determine whether the first actual oxidation-reduction potential is within a preset first oxidation-reduction potential threshold range, whether the second actual oxidation-reduction potential is within a preset second oxidation-reduction potential threshold range, whether the actual dissolved oxygen concentration is within a preset dissolved oxygen concentration threshold range, and whether the actual activated sludge concentration is within a preset activated sludge concentration threshold range;

[0050] If not, a corresponding early warning prompt will be issued.

[0051] Optionally, the sewage treatment process control method further includes:

[0052] obtaining the actual nitrate nitrogen concentration of the front anoxic pool;

[0053] Determine whether the actual nitrate nitrogen concentration is greater than a preset maximum nitrate nitrogen concentration and whether the duration reaches a first preset duration threshold;

[0054] If yes, the first electric butterfly valve is controlled to increase the flow rate of the first water inlet pipe, and the second electric butterfly valve is controlled to reduce the flow rate of the second water inlet pipe; for every 5% decrease in the flow rate of the second water inlet pipe, the dephosphorization agent dosing flow rate is increased by 1%;

[0055] Determine whether the actual nitrate nitrogen concentration is less than a preset minimum nitrate nitrogen concentration, and whether the duration reaches the first preset duration threshold;

[0056] If so, control the first electric butterfly valve to reduce the flow of the first water inlet pipe, and control the second electric butterfly valve to increase the flow of the second water inlet pipe; for every 5% increase in the flow of the second water inlet pipe, the dephosphorization agent dosing flow is reduced by 1%; wherein, when adjusting the flow of the first water inlet pipe and the second water inlet pipe, the adjustment is performed in an amplitude of 3%; the initial water inlet ratio of the first water inlet pipe is controlled at 50% to 70% of the total water inlet flow, and the initial water inlet ratio of the second water inlet pipe is controlled at 30% to 50% of the total water inlet flow.

[0057] By adopting the above technical solution, assuming that the NO3-N concentration setting value of the front anoxic tank is =1.0±0.25mg / L; if the NO3-N concentration of the front anoxic tank is greater than 1.25mg / L and lasts for 1h, it means that the denitrification effect of the front anoxic tank of the system is lower than expected due to insufficient carbon source, so it is necessary to control the first electric butterfly valve to increase the flow of the first water inlet pipe, and control the second electric butterfly valve to reduce the flow of the second water inlet pipe; if the NO3-N concentration of the front anoxic tank is less than 0.75mg / L and lasts for 1h, it means that the water in the front anoxic tank is sufficient to meet In order to achieve sufficient denitrification effect, the surplus carbon source can be supplied to the anaerobic tank. The hydrolysis and acidification process in the anaerobic environment will release more volatile fatty acids (VFA), and strengthen the phosphorus release and carbon absorption process of anaerobic polyphosphate bacteria (PAOs) and denitrifying polyphosphate bacteria (DPBs). Therefore, it is necessary to control the first electric butterfly valve to reduce the flow of the first water inlet pipe, and control the second electric butterfly valve to increase the flow of the second water inlet pipe; so when the carbon source is insufficient, the removal of nitrogen by denitrification is given priority. When the carbon source is relatively sufficient, the carbon source can be tilted towards the phosphorus removal part to reduce the use of phosphorus removal agents.

[0058] Optionally, the sewage treatment process control method further includes:

[0059] Get the actual nitrate nitrogen concentration limit C of the aerobic pool 限 ; C 限 =X+q4 / (1+R), q4=K dn2 *MLSS 生化 *H4 / 24,MLSS 生化 =R / (R+1)*MLSS 膜池 ; X is the set concentration of nitrate nitrogen effluent from the membrane pool, q4 is the removal concentration of the post-anoxic pool, R is the sludge return ratio, K dn2 is the denitrification rate of the post-anoxic pool; MLSS 膜池 is the sludge concentration in the membrane pool, H4 is the hydraulic retention time in the post-anoxic pool;

[0060] Judgment C 限 Is it greater than N2, where N2 is the actual nitrate nitrogen effluent concentration detected in the aerobic pool;

[0061] If yes, control the dosing device to increase the carbon source dosing flow rate by 5%;

[0062] If not, the dosing device is controlled to reduce the carbon source dosing flow rate by 1%.

[0063] By adopting the above technical solution, when C 限 >N2, indicating that the carbon source allocation strategy of the dosing device is still unable to remove nitrate nitrogen within the preset threshold range, and will face the risk of water quality exceeding the standard. Therefore, it is necessary to supplement the carbon source to improve the denitrification effect of the post-anoxic tank. Therefore, the dosing device needs to increase the carbon source dosing flow rate by 5%;

[0064] When C 限 ≤N2, indicating that the denitrification effect is good, so the dosing device can reduce the carbon source dosing flow rate by 1%.

[0065] Optionally, the sewage treatment process control method further includes:

[0066] Obtain the theoretical removal amount C of nitrate nitrogen in the aerobic pool 阈 ; C 阈 =(C3-C 限 )*(1+R+r), C3=(C2*(1+r)+X*R) / (1+r+R), C2=N1-q2 / (1+r), q2=K dn1 *MLSS 生化 *H2 / 24; C3 is the nitrate nitrogen inlet concentration of the aerobic tank, r is the nitrification liquid return ratio, C2 is the nitrate nitrogen effluent concentration of the anaerobic tank, N1 is the actual nitrate nitrogen effluent concentration detection value of the anoxic tank, q2 is the removal concentration of the anaerobic tank, K dn1 is the denitrification rate of the anaerobic tank, H2 is the hydraulic retention time of the anaerobic tank;

[0067] Obtaining ammonia nitrogen inlet concentration detection value A of the front anoxic tank;

[0068] Determine the C of the aerobic pool 阈 + Is A less than 0?

[0069] If yes, adjust the judgment frequency to once every 4 hours;

[0070] If not, adjust the nitrification liquid reflux pump according to the adjustment ratio of 0.5Q to increase the nitrification liquid reflux volume, and the adjustment judgment frequency is once every 4 hours; Q is the total water inlet flow of the system.

[0071] By adopting the above technical solution, when the C 阈 +A≥0, indicating that nitrate nitrogen has a tendency to accumulate. The nitrification liquid reflux pump can be adjusted to increase the nitrification liquid reflux rate. The adjustment ratio is 0.5Q and the judgment is repeated every 4 hours. 阈 +A<0, indicating that the denitrification effect is good, so no adjustment is required, and then re-evaluate every 4 hours; the biological denitrification environment is stabilized and the denitrification process is stabilized through the regulating function of internal reflux.

[0072] Optionally, the sewage treatment process control method further includes:

[0073] Determine whether the second actual oxidation-reduction potential is not less than the first oxidation-reduction potential set minimum value, and the first actual oxidation-reduction potential is not less than 0mv, and the duration reaches a second preset duration threshold;

[0074] If yes, the nitrification liquid reflux pump is controlled to reduce the nitrification liquid flow rate by 5%;

[0075] When the second actual oxidation-reduction potential is greater than the first oxidation-reduction potential set minimum value, or the first actual oxidation-reduction potential is greater than 0mv, no response is given.

[0076] By adopting the above technical solution, for example, the first redox potential of the front anoxic tank is set in the range of -50mv to -110mv, the second redox potential of the anaerobic tank is set in the range of -110mv to -300mv, and the second preset time threshold is 2h; when the ORP of the anaerobic tank is ≥-50mv and the ORP of the front anoxic tank is ≥0mv, and it lasts for 2h, it means that the anaerobic tank no longer has an anaerobic environment, so the nitrification liquid reflux pump is controlled to reduce the nitrification liquid flow rate by 5%; when the ORP of the anaerobic tank is greater than -50mv or the ORP of the front anoxic tank is greater than 0mv, it means that the redox properties in the biochemical tank are still being adjusted and no treatment is performed.

[0077] In summary, the present application has at least the following beneficial effects:

[0078] 1. The purpose of setting the first water inlet pipe to be connected with the front anoxic tank, the second water inlet pipe to be connected with the anaerobic tank, and setting the nitrification liquid return pump and the sludge return pump is that in the process flow, it absorbs both the excellent denitrification characteristics of the inverted AAO and the idea of ​​double sludge treatment, realizes the separation characteristics of denitrification and phosphorus removal on the sludge age, and makes aerobic polyphosphate bacteria (PAOS) ​​and denitrifying polyphosphate bacteria (DPBs) completely experience the anaerobic-aerobic / anoxic environment; therefore, it can realize the denitrification and phosphorus removal of sewage with low consumption and stability.

[0079] 2. By controlling the water inlet ratio distribution and nitrification liquid reflux, the overall nitrogen removal and phosphorus removal effect of the system can be guaranteed. When the carbon source is insufficient, the system gives priority to the removal of nitrogen by denitrification; when the carbon source is relatively sufficient, the system tilts the carbon source toward the phosphorus removal part through accounting, thereby reducing the use of the system's phosphorus removal agent; at the same time, the system can also stabilize the biological phosphorus removal environment through the regulation function of internal reflux, so that the polyphosphate bacteria and denitrifying polyphosphate bacteria can simultaneously and completely experience the process of releasing phosphorus and absorbing carbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is the structural connection diagram of the sewage treatment process of this application;

[0081] Figure 2 It is the system connection diagram of the sewage treatment process control system of this application;

[0082] Figure 3 It is a flowchart of an implementation method of a sewage treatment process control method of the present application;

[0083] Figure 4It is a flowchart of another implementation method of the sewage treatment process control method of the present application;

[0084] Figure 5 It is a flow chart of another implementation method of the sewage treatment process control method of the present application.

[0085] Explanation of the reference numerals: 1. first water inlet pipe; 11. first electric butterfly valve; 2. second water inlet pipe; 21. second electric butterfly valve; 3. nitrification liquid reflux pump; 4. sludge reflux pump; 5. water production pump; 6. residual sludge pump; 7. dosing device; 8. flow meter; 9. first nitrate nitrogen detector; 10. first ORP detector; 11. second ORP detector; 12. second nitrate nitrogen detector; 13. DO detector; 14. MLSS detector; 15. ammonia nitrogen detector; 16. intelligent decision-making module; 17. intelligent control module; 18. intelligent monitoring module. DETAILED DESCRIPTION

[0086] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1 -Attached Figure 5 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0087] The first embodiment of the present application discloses a wastewater treatment process for nitrogen and phosphorus removal. Figure 1 As an implementation method of the sewage treatment process, the sewage treatment process may include a first water inlet pipe 1, a second water inlet pipe 2, a front anoxic tank, an anaerobic tank, an aerobic tank, a post anoxic tank, a membrane tank, a water production pump 5, a residual sludge pump 6, a nitrification liquid return pump 3 and a sludge return pump 4.

[0088] Among them, the first water inlet pipe 1 is connected to the first electric butterfly valve 11, and its outlet is connected to the water inlet of the front anoxic tank. The second water inlet pipe 2 is connected to the second electric butterfly valve 21, and its outlet is connected to the water inlet of the anaerobic tank, and the water outlet of the front anoxic tank is also connected to the water inlet of the anaerobic tank. The water inlet of the aerobic tank is connected to the water outlet of the anaerobic tank, the water inlet of the rear anoxic tank is connected to the water outlet of the aerobic tank, and the water inlet of the membrane tank is connected to the water outlet of the rear anoxic tank. The water inlet of the water production pump 5 is connected to the water outlet of the membrane tank, and the water inlet of the residual sludge pump 6 is connected to the mud outlet opened at the bottom of the membrane tank. The water inlet of the nitrification liquid reflux pump 3 is connected to the water outlet of the aerobic tank, and its water outlet is connected to the water inlet of the front anoxic tank. The water inlet of the sludge reflux pump 4 is connected to the membrane tank, and its water outlet is connected to the water inlet of the aerobic tank.

[0089] Part of the raw water flows from the first water inlet pipe 1 to the front anoxic tank, and the remaining part flows from the second water inlet pipe 2 to the anaerobic tank. The water inlet ratio is controlled at 50% to 70% of the total water inlet flow, which is adjusted by the first electric butterfly valve 11 and the second electric butterfly valve 21. In the front anoxic tank, the organic matter in the sewage is mixed with the nitrification liquid returned from the aerobic tank, and the activated sludge uses the nitrate provided by the nitrification liquid as an electron donor for denitrification; part of the sewage is acidified in the anaerobic tank, and a large amount of VFA is formed in the water, which is easy for polyphosphate bacteria (such as PAOs and DPBs) to absorb and form poly-β-hydroxybutyric acid (PHB) in the cell, and release a large amount of inorganic phosphate (PO4 3- -P); in the aerobic pool, nitrifying bacteria use oxygen and ammonia nitrogen in the water to nitrify, and aerobic polyphosphate bacteria begin to over-enrich phosphorus in the form of polyphosphates; in the post-anoxic pool, the oligotrophic environment causes some microorganisms to undergo endogenous respiration, and some denitrifying bacteria and denitrifying polyphosphate bacteria begin to play a role in the facultative anaerobic environment, and the denitrification and phosphorus removal effect of the process will be further improved. Finally, the sewage is sucked out by the membrane, and the activated sludge remains in the membrane pool to participate in the next cycle.

[0090] For membrane pools, the sludge concentration and membrane module type can be adjusted according to the water quality: when the treated water quality is municipal sewage with a low carbon-nitrogen ratio, the sludge concentration in the membrane pool can be controlled at 10g / L-13g / L, and the membrane module can use hollow fiber membranes or flat membranes; when the treated water quality is biodegradable municipal industrial wastewater with a low carbon-nitrogen ratio, the activated sludge concentration needs to be increased to 12g / L-15g / L to ensure the biochemical treatment effect. It is recommended to choose a flat membrane for the membrane module. The flat membrane has good tolerance to high sludge concentration and can form a secondary dynamic membrane during operation.

[0091] In addition, the sludge mixture of the membrane tank flows to the front end of the aerobic tank through the external return pipeline, and mixes with the effluent from the anaerobic tank flowing into the aerobic tank inlet end. The flow rate is adjusted by the sludge return pump 4 to achieve external return; the sludge mixture of the aerobic tank flows to the front end of the anoxic tank through the internal return pipeline, and mixes with the inlet water of the first inlet pipe 1. The flow rate is adjusted by the nitrification liquid return pump 3 to achieve internal return.

[0092] Furthermore, the sewage treatment process also includes a dosing device 7, which is used to add a dephosphorizing agent into the aerobic tank and a carbon source into the post-anoxic tank.

[0093] The dosing device 7 includes a reagent barrel and a metering dosing pump. Two reagent barrels are provided, which are used to contain the dephosphorizing agent (PAC) and the carbon source (sodium acetate or methanol, etc.) respectively; the metering dosing pump is provided corresponding to the reagent barrel to pump the corresponding reagent into the corresponding pool.

[0094] Based on the above embodiments, the second embodiment of the present application discloses a sewage treatment control system for nitrogen removal and phosphorus removal. Figure 2As an embodiment of the sewage treatment control system, the sewage treatment control system may include a first nitrate nitrogen detector 9, a second nitrate nitrogen detector 12, an ammonia nitrogen detector 15, a first ORP detector 10, a second ORP detector 11, a DO detector 13, an MLSS detector 14 and a flow meter 8.

[0095] Among them, the first nitrate nitrogen detector 9 is installed in the front anoxic tank to monitor the nitrate nitrogen concentration of the front anoxic tank; the first ORP detector 10 is installed in the front anoxic tank to monitor the redox potential of the front anoxic tank; the ammonia nitrogen detector 15 is installed in the front anoxic tank to monitor the ammonia nitrogen concentration of the front anoxic tank. The second ORP detector 11 is installed in the anaerobic tank to monitor the redox potential of the anaerobic tank. The second nitrate nitrogen detector 12 is installed in the aerobic tank to monitor the nitrate nitrogen concentration of the aerobic tank; the DO detector 13 is installed in the aerobic tank to monitor the dissolved oxygen concentration of the aerobic tank. The MLSS detector 14 is installed in the membrane tank to monitor the activated sludge concentration of the membrane tank. The flow meter 8 is installed on the first water inlet pipe 1, the second water inlet pipe 2, the nitrification liquid return pipe, the sludge return pipe and the dosing pipe respectively to monitor the liquid flow in the corresponding pipes.

[0096] In addition, the sewage treatment process control system also includes an intelligent monitoring module 18 , an intelligent control module 17 and an intelligent decision-making module 16 .

[0097] Among them, the intelligent monitoring module 18 is used to obtain and monitor the flow data set, which includes the flow information of the first water inlet pipe 1, the second water inlet pipe 2, the dosing pipe, the nitrification liquid return pipe and the sludge return pipe; as well as the redox potential information of the front anoxic tank and the anaerobic tank, the nitrate nitrogen concentration information of the front anoxic tank and the aerobic tank, the ammonia nitrogen concentration information of the front anoxic tank, the dissolved oxygen concentration information of the aerobic tank and the activated sludge concentration information of the membrane tank.

[0098] The intelligent control module 17 controls the actions of the first electric butterfly valve 11, the second electric butterfly valve 21, the nitrification liquid return pump 3, the sludge return pump 4, the water production pump 5, the excess sludge pump 6 and the dosing device 7 according to the flow data set. The intelligent decision module 16 issues an early warning prompt when the data is abnormal according to the flow data set.

[0099] Based on the above system embodiment, the third embodiment of the present application discloses a sewage treatment process control method for nitrogen and phosphorus removal. As an implementation of the sewage treatment process control method, the sewage treatment process control method may include: obtaining a first actual redox potential of the front anoxic tank, a second actual redox potential of the anaerobic tank, an actual dissolved oxygen concentration of the aerobic tank, and an actual activated sludge concentration of the membrane tank;

[0100] It is respectively determined whether the first actual oxidation-reduction potential is within the preset first oxidation-reduction potential threshold range, whether the second actual oxidation-reduction potential is within the preset second oxidation-reduction potential threshold range, whether the actual dissolved oxygen concentration is within the preset dissolved oxygen concentration threshold range, and whether the actual activated sludge concentration is within the preset activated sludge concentration threshold range; if not, a corresponding early warning prompt is issued, and if so, no response is given.

[0101] For example, the first redox potential threshold range set for the front anoxic tank is ORP = -50mv ~ -110mv, the second redox potential threshold range set for the anaerobic tank is ORP = -110mv ~ -300mv, the dissolved oxygen concentration threshold range set for the aerobic tank is DO = 1.0mg / L ~ 3.0mg / L, and the activated sludge concentration threshold range set for the membrane tank is MLSS = 10g / L ~ 15g / L; when the actual detection indicators of each tank deviate from the set threshold range, the intelligent decision-making module will issue corresponding early warning prompts.

[0102] Reference Figure 3 As another implementation of the sewage treatment process control method, the sewage treatment process control method may further include S310-S350:

[0103] S310, obtaining the actual nitrate nitrogen concentration of the front anoxic pool;

[0104] S320, determining whether the actual nitrate nitrogen concentration is greater than a preset maximum nitrate nitrogen concentration and whether the duration reaches a first preset duration threshold;

[0105] S330, if yes, control the first electric butterfly valve to increase the flow of the first water inlet pipe, and control the second electric butterfly valve to reduce the flow of the second water inlet pipe; for every 5% reduction in the flow of the second water inlet pipe, the dephosphorization agent dosing flow rate increases by 1%;

[0106] S340, determining whether the actual nitrate nitrogen concentration is less than a preset minimum nitrate nitrogen concentration and whether the duration reaches a first preset duration threshold;

[0107] S350, if yes, control the first electric butterfly valve to reduce the flow of the first water inlet pipe, and control the second electric butterfly valve to increase the flow of the second water inlet pipe; for every 5% increase in the flow of the second water inlet pipe, the dephosphorization agent dosing flow is reduced by 1%.

[0108] Specifically, when adjusting the flow of the first water inlet pipe and the second water inlet pipe, the adjustment is performed with a range of 3%; the initial water inlet ratio of the first water inlet pipe is controlled at 50% to 70% of the total water inlet volume, and the initial water inlet ratio of the second water inlet pipe is controlled at 30% to 50% of the total water inlet volume.

[0109] For example, the NO3-N concentration setting value of the front anoxic pool is = 1.0 ± 0.25 mg / L. When the NO3-N concentration of the front anoxic pool deviates, the system will adjust the dual pool water distribution flow rate by 3% through the intelligent control module, as shown below:

[0110] ① The NO3-N concentration in the front anoxic pool is greater than 1.25 mg / L and lasts for 1 hour. This indicates that the denitrification effect of the front anoxic pool is lower than expected due to insufficient carbon source. The intelligent control module increases the flow of the first water inlet pipe by controlling the first electric butterfly valve, and reduces the flow of the second water inlet pipe by the second electric butterfly valve;

[0111] ② The NO3-N concentration in the front anoxic pool is less than 0.75 mg / L and lasts for 1 hour. This indicates that the water in the front anoxic pool is sufficient to meet the denitrification effect, and the surplus carbon source can be supplied to the anaerobic pool. The hydrolysis and acidification process in the anaerobic environment will release more volatile fatty acids (VFA), strengthen the phosphorus release and carbon absorption process of anaerobic section polyphosphate bacteria (PAOs) and denitrifying polyphosphate bacteria (DPBs), and the intelligent control module reduces the flow of the first water inlet pipe by controlling the first electric butterfly valve, and increases the flow of the second water inlet pipe by the second electric butterfly valve.

[0112] By controlling the influent ratio, the denitrification effect of the anoxic tank can be optimized, which in turn affects the concentration of volatile fatty acids (VFA) produced in the anaerobic tank.

[0113] Reference Figure 4 The sewage treatment process control method may further include S410-S440:

[0114] S410, obtain the actual nitrate nitrogen concentration limit C of the aerobic pool 限 ;

[0115] S420, judgment C 限 Is it greater than N2, where N2 is the actual nitrate nitrogen effluent concentration detected in the aerobic pool?

[0116] S430, if yes, control the dosing device to increase the carbon source dosing flow rate by 5%;

[0117] S440, if not, control the dosing device to reduce the carbon source dosing flow rate by 1%.

[0118] Specifically, C 限 =X+q4 / (1+R), q4=K dn2 *MLSS 生化 *H4 / 24,MLSS 生化 =R / (R+1)*MLSS 膜池 ; X is the set concentration of nitrate nitrogen effluent from the membrane pool, q4 is the removal concentration of the post-anoxic pool, R is the sludge return ratio, K dn2is the denitrification rate of the post-anoxic pool; MLSS 膜池 is the sludge concentration in the membrane pool, and H4 is the hydraulic retention time in the post-anoxic pool.

[0119] For example, the denitrification rate of the anoxic tank is set to K dn2 =3mgNO3-N / (MLSS·d); the hydraulic retention time of the post-anoxic tank is 2.5h; the sludge return ratio is 2, the sludge concentration of the membrane tank is 13.5g / L, and the sludge concentration of the biochemical section is: MLSS 生化 =2 / (2+1)*13.5=9g / L, the NO3-N effluent concentration of the membrane pool is set to 4.2mg / L, the NO3-N effluent concentration of the aerobic pool is detected to be 4.8mg / L, and the NO3-N control concentration limit of the aerobic pool is C 限 .

[0120] The removal concentration of the post-anoxic tank is: q4 = 3*9*2.5 / 24 = 2.81 mg / L

[0121] The nitrate nitrogen limit for aerobic pools is: C 限 =4.2+2.81 / (1+2)=5.13mg / L

[0122] At this time, the C of the aerobic pool 限 >N2, indicating that the pre-carbon source allocation strategy still cannot remove nitrate nitrogen within the predetermined range, the system will face the risk of water quality exceeding the standard, and it is necessary to supplement the carbon source to improve the denitrification effect of the post-anoxic tank. The system will control the dosing device through the intelligent control module to increase the carbon source dosing flow by 5%. The strategy is adjusted every 4 hours. After each adjustment, the system will reverse the denitrification rate of the post-anoxic tank based on the test value to update the data.

[0123] Reference Figure 5 The sewage treatment process control method also includes S510-S550:

[0124] S510, obtaining the theoretical removal amount C of nitrate nitrogen in the aerobic pool 阈 ;

[0125] S520, obtaining a detection value A of the ammonia nitrogen influent concentration of the front anoxic tank;

[0126] S530, determine the C of the aerobic pool 阈 + Is A less than 0?

[0127] S540: If yes, adjust the judgment frequency to once every 4 hours;

[0128] S550, if not, adjust the nitrification liquid reflux pump according to the adjustment ratio of 0.5Q to increase the nitrification liquid reflux volume, and the adjustment judgment frequency is once every 4 hours.

[0129] Specifically, C阈 =(C3-C 限 )*(1+R+r), C3=(C2*(1+r)+X*R) / (1+r+R), C2=N1-q2 / (1+r), q2=K dn1 *MLSS 生化 *H2 / 24; C3 is the nitrate nitrogen inlet concentration of the aerobic tank, r is the nitrification liquid return ratio, C2 is the nitrate nitrogen effluent concentration of the anaerobic tank, N1 is the actual nitrate nitrogen effluent concentration detection value of the anoxic tank, q2 is the anaerobic tank removal concentration, K dn1 is the denitrification rate of the anaerobic tank, and H2 is the hydraulic retention time of the anaerobic tank.

[0130] For example, based on the above set data, the denitrification rate of the anaerobic tank is set to K dn1 =7.8mgNO3-N / (MLSS·d), the nitrification liquid reflux ratio is 3, the hydraulic retention time of the anaerobic tank is 2h, the NO3-N effluent concentration detection value of the front anoxic tank is 1.27mg / L; the ammonia nitrogen inlet concentration detection value A of the front anoxic tank is 25mg / L.

[0131] The removal concentration in the anaerobic tank is: q4 = 7.8 * 9 * 2 / 24 = 5.85 mg / L

[0132] The nitrate nitrogen inlet concentration of the anaerobic tank is: C2 = 1.27-5.85 / (1+3) = -0.18 mg / L

[0133] The nitrate nitrogen inlet concentration of the aerobic pool is: C3 = (-0.18*(1+3)+4.2*2) / (1+2+3) = 1.28 mg / L

[0134] The amount of nitrate nitrogen removed in the aerobic pool is: C 阈 =(1.28-5.13)*(1+2+3)=-23.1mg / L

[0135] At this time, the C threshold + A of the aerobic pool is ≥ 0, indicating that the nitrate nitrogen in the system tends to accumulate. The system will adjust the nitrification liquid reflux pump through the intelligent control module to increase the nitrification liquid reflux volume. The adjustment ratio is 0.5Q, and the adjustment judgment frequency is once every 4 hours; Q is the total water inlet flow of the system.

[0136] System fixes:

[0137] The nitration liquid reflux ratio r is adjusted to 3.5. At this time, the system:

[0138] The predicted value of nitrate nitrogen influent concentration in the anaerobic tank is: C2 = 1.27-5.85 / (1+3.5) = -0.03 mg / L

[0139] The predicted value of the nitrate nitrogen inlet concentration in the aerobic pool is: C3 = (-0.003*(1+3.5)+4.2*2) / (1+2+3.5) = 1.27 mg / L The predicted value of the nitrate nitrogen concentration in the aerobic pool is: C 阈 =(1.27-5.13)*(1+2+3.5)=--25.09mg / L

[0140] At this time, the C threshold + A of the aerobic pool is less than 0, indicating that the system has an improved tendency to remove nitrate nitrogen, and the adjustment judgment frequency is once every 4 hours.

[0141] It should be noted that for the control of biological phosphorus removal effect: in addition to carbon source supplementation, the polyphosphate bacteria in the inverted AAO process can sequentially experience anaerobic-aerobic environment, and the denitrifying polyphosphate bacteria can also sequentially experience anaerobic-anoxic environment. In addition to the separate supplementation of carbon sources, the anaerobic environment is also a key link in biological phosphorus removal.

[0142] The sewage treatment process control method may include:

[0143] Determine whether the second actual oxidation-reduction potential is not less than the minimum value set for the first oxidation-reduction potential, and whether the first actual oxidation-reduction potential is not less than 0mv, and whether the duration reaches a second preset duration threshold; if so, control the nitrification liquid reflux pump to reduce the nitrification liquid flow rate by 5%; if the second actual oxidation-reduction potential is greater than the minimum value set for the first oxidation-reduction potential, or when the first actual oxidation-reduction potential is greater than 0mv, do not respond.

[0144] Specifically, the ORP setting range of the front anoxic tank is -50mv to -110mv, the ORP setting range of the anaerobic tank is between -110mv and -300mv, and the second preset time threshold is 2h. Since multiple tanks are linked, the redox properties of the water body are significantly affected by the reflux:

[0145] ① When the ORP of the anaerobic tank is ≥-50mv and the ORP of the front anoxic tank is ≥0mv and lasts for 2h, it means that the anaerobic tank no longer has an anaerobic environment. The system will control the nitrification liquid reflux pump to reduce the nitrification liquid flow rate by 5% through the intelligent control module.

[0146] ② When the ORP of the anaerobic tank is greater than -50mv or the ORP of the front anoxic tank is greater than 0mv, it means that the redox properties in the biochemical tank are still being adjusted and the system does not take any action.

[0147] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application in sequence. Any feature disclosed in this specification (including the abstract and drawings), unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Claims

1. A sewage treatment process control method for nitrogen and phosphorus removal, characterized in that: The sewage treatment process based on nitrogen removal and phosphorus removal is realized, and the sewage treatment process includes: The first water inlet pipe (1) is connected to a first electric butterfly valve; The second water inlet pipe (2) is connected to a second electric butterfly valve (21); A front anoxic tank, the water inlet of which is connected to the first water inlet pipe (1); An anaerobic tank, the water inlet of which is respectively connected to the water outlet of the front anoxic tank and the second water inlet pipe (2); an aerobic tank, the water inlet of which is connected to the water outlet of the anaerobic tank; a post-anoxic tank, the water inlet of which is connected to the water outlet of the aerobic tank; A membrane tank, wherein the water inlet is connected to the water outlet of the post-anoxic tank; A water production pump (5), the water inlet of which is connected to the water outlet of the membrane pool; A residual sludge pump (6) is connected to the sludge outlet provided at the bottom of the membrane tank; A nitrification liquid reflux pump (3), the water inlet of which is connected to the water outlet of the aerobic tank, and the water outlet of which is connected to the water inlet of the front anoxic tank; A sludge return pump (4), the water inlet of which is connected to the membrane tank, and the water outlet of which is connected to the water inlet of the aerobic tank; The sewage treatment process control method comprises: Obtaining a first actual redox potential of the front anoxic tank, a second actual redox potential of the anaerobic tank, an actual dissolved oxygen concentration of the aerobic tank, and an actual activated sludge concentration of the membrane tank; Respectively determine whether the first actual oxidation-reduction potential is within a preset first oxidation-reduction potential threshold range, whether the second actual oxidation-reduction potential is within a preset second oxidation-reduction potential threshold range, whether the actual dissolved oxygen concentration is within a preset dissolved oxygen concentration threshold range, and whether the actual activated sludge concentration is within a preset activated sludge concentration threshold range; If not, a corresponding early warning prompt will be issued; The sewage treatment process control method also includes: obtaining the actual nitrate nitrogen concentration of the front anoxic pool; Determine whether the actual nitrate nitrogen concentration is greater than a preset maximum nitrate nitrogen concentration and whether the duration reaches a first preset duration threshold; If yes, the first electric butterfly valve is controlled to increase the flow rate of the first water inlet pipe, and the second electric butterfly valve is controlled to reduce the flow rate of the second water inlet pipe; for every 5% decrease in the flow rate of the second water inlet pipe, the dephosphorization agent dosing flow rate is increased by 1%; Determine whether the actual nitrate nitrogen concentration is less than a preset minimum nitrate nitrogen concentration, and whether the duration reaches the first preset duration threshold; If so, control the first electric butterfly valve to reduce the flow of the first water inlet pipe, and control the second electric butterfly valve to increase the flow of the second water inlet pipe; for every 5% increase in the flow of the second water inlet pipe, the dephosphorization agent dosing flow is reduced by 1%; wherein, when adjusting the flow of the first water inlet pipe and the second water inlet pipe, the adjustment is performed in an amplitude of 3%; the initial water inlet ratio of the first water inlet pipe is controlled at 50% to 70% of the total water inlet flow, and the initial water inlet ratio of the second water inlet pipe is controlled at 30% to 50% of the total water inlet flow.

2. A sewage treatment process control method for nitrogen and phosphorus removal according to claim 1, characterized in that: The sewage treatment process control method also includes: Get the actual nitrate nitrogen concentration limit C of the aerobic pool 限 ; C 限 =X+q4 / (1+R), q4=K dn2 *MLSS 生化 *H4 / 24,MLSS 生化 =R / (R+1)*MLSS 膜池 ; X is the set concentration of nitrate nitrogen effluent from the membrane pool, q4 is the removal concentration of the post-anoxic pool, R is the sludge return ratio, K dn2 is the denitrification rate of the post-anoxic pool; MLSS 膜池 is the sludge concentration in the membrane pool, H4 is the hydraulic retention time in the post-anoxic pool; Judgment C 限 Is it greater than N2, where N2 is the actual nitrate nitrogen effluent concentration detected in the aerobic pool; If yes, the dosing device is controlled to increase the carbon source dosing flow rate by 5%; If not, the dosing device is controlled to reduce the carbon source dosing flow rate by 1%.

3. A sewage treatment process control method for nitrogen and phosphorus removal according to claim 2, characterized in that: The sewage treatment process control method also includes: Obtain the theoretical removal amount C of nitrate nitrogen in the aerobic pool 阈 ; C 阈 =(C3-C 限 )*(1+R+r), C3=(C2*(1+r)+X*R) / (1+r+R), C2=N1-q2 / (1+r), q2=K dn1 *MLSS 生化 *H2 / 24; C3 is the nitrate nitrogen inlet concentration of the aerobic tank, r is the nitrification liquid return ratio, C2 is the nitrate nitrogen effluent concentration of the anaerobic tank, N1 is the actual nitrate nitrogen effluent concentration detection value of the anoxic tank, q2 is the anaerobic tank removal concentration, K dn1 is the denitrification rate of the anaerobic tank, H2 is the hydraulic retention time of the anaerobic tank; Obtaining ammonia nitrogen inlet concentration detection value A of the front anoxic tank; Determine the C of the aerobic pool 阈 + Is A less than 0? If yes, adjust the judgment frequency to once every 4 hours; If not, adjust the nitrification liquid reflux pump according to the adjustment ratio of 0.5Q to increase the nitrification liquid reflux volume, and the adjustment judgment frequency is once every 4 hours; Q is the total water inlet flow of the system.

4. The sewage treatment process control method for nitrogen and phosphorus removal according to claim 1 is characterized in that: The sewage treatment process control method also includes: Determine whether the second actual oxidation-reduction potential is not less than the first oxidation-reduction potential set minimum value, and the first actual oxidation-reduction potential is not less than 0mv, and the duration reaches a second preset duration threshold; If yes, the nitrification liquid reflux pump is controlled to reduce the nitrification liquid flow rate by 5%; When the second actual oxidation-reduction potential is greater than the first oxidation-reduction potential set minimum value, or the first actual oxidation-reduction potential is greater than 0mv, no response is given.

5. The sewage treatment process control method for nitrogen and phosphorus removal according to claim 1 is characterized in that: The sewage treatment process also includes: A dosing device (7) is used to add a dephosphorizing agent to the aerobic tank and a carbon source to the post-anoxic tank; The dosing device (7) comprises: There are two reagent barrels, which are used to contain the dephosphorizing agent and the carbon source respectively; There are two metering and dosing pumps, which are connected to the corresponding medicine barrels respectively and are used to pump the medicine into the corresponding pools.

6. A sewage treatment control system for nitrogen and phosphorus removal, based on the sewage treatment process control method as claimed in claim 1; The sewage treatment control system comprises: A first nitrate nitrogen detector (9), arranged in the front anoxic tank, for monitoring the nitrate nitrogen concentration in the front anoxic tank; an ammonia nitrogen detector (15), arranged in the front anoxic tank, for detecting the ammonia nitrogen concentration in the front anoxic tank; A first ORP detector (10), arranged in the front anoxic tank, for monitoring the redox potential of the front anoxic tank; A second ORP detector (11), arranged in the anaerobic tank, for monitoring the redox potential of the anaerobic tank; A second nitrate nitrogen detector (12), arranged in the aerobic tank, for monitoring the nitrate nitrogen concentration in the aerobic tank; A DO detector (13), arranged in the aerobic tank, for monitoring the dissolved oxygen concentration in the aerobic tank; The MLSS detector (14) is arranged in the membrane pool and is used to monitor the activated sludge concentration in the membrane pool.

7. A sewage treatment control system for nitrogen and phosphorus removal according to claim 6, characterized in that: The sewage treatment control system also includes: The flow meters (8) are respectively installed on the first water inlet pipe (1), the second water inlet pipe (2), the nitrification liquid return pipe, the sludge return pipe and the dosing pipe, and are used to detect the flow rates of the corresponding pipes.

8. A sewage treatment control system for nitrogen and phosphorus removal according to claim 7, characterized in that: The sewage treatment process control system also includes: An intelligent monitoring module (18) is used to obtain and monitor a flow data set; the flow data set includes flow information of the first water inlet pipe (1), the second water inlet pipe (2), the dosing pipe, the nitrification liquid return pipe and the sludge return pipe; and redox potential information of the front anoxic tank and the anaerobic tank, nitrate nitrogen concentration information of the front anoxic tank and the aerobic tank, ammonia nitrogen concentration information of the front anoxic tank, dissolved oxygen concentration information of the aerobic tank and activated sludge concentration information of the membrane tank; An intelligent control module (17) controls the actions of the first electric butterfly valve, the second electric butterfly valve (21), the nitrification liquid return pump (3), the sludge return pump (4), the produced water pump (5), the residual sludge pump (6) and the dosing device (7) based on the flow data set; The intelligent decision-making module (16) is based on the traffic data set and issues an early warning prompt when the data is abnormal.

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