An intelligent intermittent dual-sludge denitrification nitrogen and phosphorus deep purification system and method

Abstract

The present invention relates to an intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system and method thereof, belonging to the technical field of sewage purification, comprising: a nitrification tank, a denitrification tank, two anaerobic tanks, an external carbon source storage tank, a decanter and a controller. Aiming at the lower nitrogen and phosphorus concentrations and lower organic carbon concentrations of secondary effluent from sewage treatment plants compared with domestic sewage, based on the principle of double-sludge denitrification technology, the nitrification process and the denitrification process are separated and carried out in two reactors, a lower activated sludge concentration is adopted, and intelligent online control technology is applied. After nitrification, anaerobic treatment of activated sludge with precise external carbon source addition, anoxic denitrification, aerobic stripping and other steps, and by precise online control of nitrification and denitrification endpoints, the water quality of the purified water is finally brought to the surface water quality standard Class III or above, and the problem of eutrophication pollution of receiving water bodies caused by direct discharge of secondary effluent from existing sewage treatment plants is completely solved. The system is of great significance for upgrading and transforming existing sewage treatment plants, protecting water bodies in water sources, and repairing the water quality of eutrophic water bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage purification, and in particular to an intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system and method thereof. Background Art

[0002] In recent years, with the implementation of sewage treatment plant upgrades, some Chinese sewage treatment plants have implemented tertiary treatment (deep treatment). However, the advanced treatment processes typically employed in Chinese sewage treatment plants include adsorption, coagulation and sedimentation, ion exchange, membrane separation, and biological deep purification technologies. These technologies and methods are subject to high costs, suboptimal purification effects, and difficulty in simultaneously removing nitrogen and phosphorus. While widely used, denitrifying filters suffer from carbon source shortages, poor purification efficiency in low winter temperatures, and suboptimal phosphorus removal efficiency, typically only 20-30%. While constructed wetlands are simple to manage and offer low treatment and operating costs, they suffer from long retention times, large footprints, and suboptimal purification effects, particularly in winter.

[0003] Therefore, how to deeply treat the secondary effluent from sewage treatment plants has always been one of the difficult problems that need to be solved urgently in order to solve the current eutrophication problem in my country. Summary of the Invention

[0004] The present invention provides an intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system and method thereof, which solves the technical problem of eutrophication of water bodies by secondary effluent from sewage treatment plants.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system, comprising: a denitrification tank, two anaerobic tanks, an external carbon source storage tank, a decanter, multiple submersible agitators and a controller;

[0006] The top of the denitrification tank is provided with a denitrification exhaust hole, the bottom of the tank is provided with a nitrification liquid inlet hole, a denitrification mud discharge hole, a mud inlet hole and a mud discharge hole, and the side wall is provided with a perforation. A denitrification mud discharge pump is installed at the denitrification mud discharge hole, and a denitrification exhaust valve is installed at the denitrification exhaust hole.

[0007] The bottom ends of the two anaerobic tanks are each provided with a mud inlet and outlet hole and the top ends thereof are provided with an external carbon source hole. The two mud inlet and outlet holes are respectively connected to the mud inlet hole and the mud outlet hole through a mud supply pipe and a mud return pipe. A mud supply pump is installed on each of the two mud supply pipes, and a mud return pump is installed on each of the two mud return pipes. An exhaust pipe is installed on the top ends of the two anaerobic tanks, and an anaerobic water level controller and an anaerobic exhaust valve are installed on each of the two exhaust pipes.

[0008] The bottom end of the external carbon source storage tank is provided with an external carbon source outlet hole, and the external carbon source outlet hole is connected to the two external carbon source holes through two carbon supply pipes, and the two carbon supply pipes are both equipped with an external carbon source quantitative pump;

[0009] The decanter is fixed on the electric telescopic rod in the denitrification tank in an inclined manner from top to bottom, and its water inlet is placed in the denitrification tank. The water outlet of the decanter passes through the perforation, and the decanter electric valve is installed on the pipe wall passing through the perforation.

[0010] A plurality of submersible agitators are respectively installed in the denitrification tank and the two anaerobic tanks;

[0011] The controller is electrically connected to the denitrification exhaust valve, the denitrification sludge pump, the two sludge supply pumps, the two sludge return pumps, the two anaerobic water level controllers, the two anaerobic exhaust valves, the two external carbon source metering pumps, the decanter, the decanter electric valve and the plurality of submersible mixers.

[0012] The beneficial effects of the present invention are:

[0013] 1. The denitrification tank is a key device for denitrification and nitrogen removal, denitrification and phosphorus absorption, aerobic phosphorus absorption, nitrogen stripping and solid-liquid separation of the secondary effluent from the sewage treatment plant; the decanter installed in the denitrification tank can automatically adjust the drainage height, so that the denitrification tank can reduce the static sedimentation time and improve the sedimentation and drainage efficiency. The exhaust valves installed in the denitrification tank and anaerobic tank can be closed during anaerobic and anoxic stirring to reduce the entry of air and oxygen and reduce the consumption of external carbon sources.

[0014] 2. Two anaerobic tanks are used, and these two anaerobic tanks are connected to the denitrification tank respectively. When one anaerobic tank is performing anaerobic treatment of activated sludge, the other is in an idle waiting state. As a result, once the denitrification tank cycle is completed, the activated sludge can be immediately transferred to the idle waiting anaerobic tank, and an external carbon source is added at the same time, and then stirred for anaerobic treatment. At this time, the activated sludge that has been anaerobically treated in the other anaerobic tank can be immediately transferred to the denitrification tank. Since the denitrification tank does not need to wait and be idle, the utilization efficiency of the denitrification tank and the activated sludge is improved, and the utilization efficiency of the external carbon source is further improved.

[0015] On the basis of the above technical solution, the present invention can also be improved as follows.

[0016] Furthermore, it also includes a denitrification pH online detector, an ORP online detector, an electrical conductivity online detector and a denitrification DO online detector; the denitrification pH online detector, the ORP online detector, the electrical conductivity online detector and the denitrification DO online detector are installed at intervals in the denitrification tank and are all electrically connected to the controller.

[0017] The above further beneficial effects are: the controller uses the detection values of the denitrification pH online detector, ORP online detector, conductivity online detector and denitrification DO online detector to track the denitrification process inside the denitrification tank in real time, accurately identify the denitrification reaction end point, and avoid the unsatisfactory total nitrogen purification effect caused by the denitrification not reaching the denitrification end point. At the same time, it also avoids the secondary release of phosphorus due to the conversion of the anoxic environment into an anaerobic environment due to the delay in the denitrification end point, which affects the purification of phosphorus; the denitrification DO online detector is used to control the DO concentration of the denitrification tank during the aerobic aeration stage to avoid the consumption of external carbon sources caused by excessive aeration.

[0018] Furthermore, it also includes a denitrification frequency converter, a denitrification aeration pump, a denitrification gas flow sensor, multiple denitrification aeration heads and a denitrification water level controller; the multiple denitrification aeration heads are fixed at intervals in the lower inner part of the denitrification tank; the air outlet of the denitrification aeration pump passes through the denitrification tank and is connected to the multiple denitrification aeration heads; the denitrification gas flow sensor is installed on the connecting pipe between the denitrification aeration pump and the multiple denitrification aeration heads; the denitrification frequency converter is electrically connected to the denitrification aeration pump; the denitrification water level controller is installed in the upper inner part of the denitrification tank; and the controller is electrically connected to the denitrification frequency converter, the denitrification gas flow sensor and the denitrification water level controller respectively.

[0019] The above further beneficial effects are: the controller controls the aeration intensity of the denitrification aeration pump through the denitrification inverter, controls the DO concentration, strengthens the aerobic absorption and removal of phosphorus through aerobic aeration, and blows off the nitrogen produced by denitrification, which facilitates the subsequent sedimentation and separation of activated sludge, while avoiding excessive aerobic aeration that leads to excessive consumption of carbon sources in microorganisms, increasing the amount of external carbon source and treatment costs.

[0020] Furthermore, it also includes a nitrification tank, a water inlet pump, a nitrification frequency converter, a nitrification aeration pump, a nitrification gas flow sensor, a plurality of nitrification aeration heads and a nitrification water level controller; the water inlet of the water inlet pump is connected to the secondary effluent of the sewage treatment plant and its outlet is connected to the nitrification tank; the bottom end of the nitrification tank is provided with a nitrification mud discharge hole and a nitrification liquid discharge hole, the nitrification mud discharge hole is installed with a nitrification mud discharge valve, the nitrification liquid discharge hole is connected to the nitrification liquid inlet hole through a nitrification liquid transfer pump; the lower end of the interior of the nitrification tank is installed with a sieve plate and the nitrification tank corresponds to the sieve plate A plurality of nitrification aeration heads are fixed on the top and a plurality of fillers are placed thereon; the nitrification frequency converter is electrically connected to the nitrification aeration pump; the air outlet of the nitrification aeration pump passes through the nitrification tank via a gas pipeline and is connected to the plurality of nitrification aeration heads; the nitrification gas flow sensor is installed on the connecting pipe between the nitrification aeration pump and the plurality of nitrification aeration heads; the nitrification water level controller is fixed in the nitrification tank; the controller is electrically connected to the water inlet pump, the nitrification frequency converter, the nitrification gas flow sensor and the nitrification water level controller respectively.

[0021] A further beneficial effect of the above-mentioned method is that when the ammonia nitrogen concentration in the secondary effluent of the sewage treatment plant is high and or the total nitrogen purification requirement is high, the secondary effluent of the sewage treatment plant can be first transported to the nitrification tank for nitrification reaction, and all the ammonia nitrogen contained in the secondary effluent of the sewage treatment plant is oxidized into nitrate or nitrite, so that deep removal of nitrogen can be achieved through subsequent denitrification.

[0022] Furthermore, it also includes a nitrification pH online detector and a nitrification DO online detector, which are fixed at intervals in the nitrification tank; and the controller is electrically connected to the nitrification pH online detector and the nitrification DO online detector, respectively.

[0023] The above further beneficial effects are: using the detection values of the nitrification pH online detector and the nitrification DO online detector, the nitrification process inside the nitrification tank can be detected in real time, the end point of the nitrification reaction can be accurately identified, and the ammonia nitrogen in the secondary effluent of the sewage treatment plant can be ensured to be completely converted into nitrate or nitrite.

[0024] Furthermore, it also includes a first sampling pump, a second sampling pump and a nitrate nitrogen online detector; the water inlet of the first sampling pump is connected to the connecting pipe between the water inlet pump and the secondary effluent of the sewage treatment plant; the water inlet of the second sampling pump is connected to the interior of the nitrification tank; the water inlet of the nitrate nitrogen online detector is connected to the water outlet of the first sampling pump and the water outlet of the second sampling pump respectively; the controller is electrically connected to the nitrate nitrogen online detector, the first sampling pump and the second sampling pump.

[0025] The above method has the following further beneficial effects: first, the first sampling pump is used to extract the secondary effluent sample from the sewage treatment plant, and then the second sampling pump is used to extract the water sample inside the nitrification tank. The nitrate nitrogen online detector measures the nitrate nitrogen concentration, and the amount of external carbon source required for denitrification in this cycle is calculated based on the set carbon-nitrogen ratio.

[0026] Furthermore, it also includes a regulating tank. When the ammonia nitrogen concentration of the secondary effluent of the sewage treatment plant is low, or there is no high requirement for the purification of total nitrogen and ammonia nitrogen, and only the removal of nitrate nitrogen, nitrite nitrogen and phosphorus in the secondary effluent is considered, the nitrification tank can be omitted and replaced by a regulating tank that does not contain a nitrification aeration pump, a nitrification inverter, a nitrification water level controller and an aeration head, and does not have a nitrification function; the regulating tank is connected to the secondary effluent of the sewage treatment plant through a pipeline, and the outlet of the regulating tank is connected to the nitrification liquid inlet hole of the denitrification tank through a pipeline, and the nitrification liquid transfer pump is arranged on the pipeline connecting the regulating tank and the denitrification tank; the water inlet of the second sampling pump is connected to the interior of the regulating tank; the water inlet of the nitrate nitrogen online detector is connected to the water outlet of the second sampling pump.

[0027] The above-mentioned further beneficial effects are: when a regulating tank is used instead of a nitrification tank, the secondary effluent of the sewage treatment plant first flows into the regulating tank for temporary storage, and then the secondary effluent of the sewage treatment plant is transferred to the denitrification tank when the denitrification tank cycle ends; and the nitrate nitrogen concentration of the water stored in the regulating tank is measured by an online nitrate nitrogen detector, and then the amount of added carbon source is calculated based on the carbon-nitrogen ratio.

[0028] Furthermore, the effective volume of the anaerobic tank is 1 / 40 to 1 / 5 of the effective volume of the denitrification tank, and the higher the total nitrogen concentration of the influent, the higher the ratio. The sludge retention time is 8 to 30 days.

[0029] The above-mentioned further beneficial effect is that the activated sludge in the denitrification tank is kept at a lower concentration due to the smaller anaerobic tank volume, thereby matching the amount of external carbon source, the phosphorus content released by anaerobes, and the nitrogen and phosphorus content of the secondary effluent of the sewage treatment plant, promoting the growth of denitrifying and phosphorus-removing organisms, and enabling nitrogen and phosphorus to be removed and absorbed simultaneously by the denitrification process of microorganisms, and not causing a decrease in phosphorus removal capacity or even a large outflow of phosphorus due to insufficient nitrate nitrogen concentration.

[0030] In addition, an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method is provided, and the specific steps are as follows:

[0031] When the ammonia nitrogen concentration in the secondary effluent of the sewage treatment plant is low or the total nitrogen purification requirements are not high, the secondary effluent of the sewage treatment plant can be nitrified without nitrification tank, but with regulating tank, specifically according to the following operation steps:

[0032] Water inlet method, nitrate nitrogen determination, and carbon-nitrogen ratio calculation: S1. The nitrification tank is omitted, and the secondary effluent of the sewage treatment plant first flows into a regulating tank. When the denitrification tank cycle ends, the nitrification liquid transfer pump transfers the inlet water stored in the regulating tank to the denitrification tank. At regular intervals, a second sampling pump collects water samples from the regulating tank and transfers them to the nitrate nitrogen online detector for nitrate nitrogen determination. The controller calculates the amount of external carbon source required for denitrification in this cycle based on the set carbon-nitrogen ratio (or if the total nitrogen concentration of the influent is known, the amount of external carbon source required for the anaerobic tank is calculated based on the total nitrogen concentration of the influent).

[0033] Activated sludge transfer, external carbon source and anaerobic treatment: At the end of each cycle of S2 and denitrification tanks, the activated sludge in the denitrification tank is transferred to the empty (no activated sludge) anaerobic tank in turn through the return sludge pump; at the same time, the controller adds external carbon source to the anaerobic tank through the external carbon source metering pump according to the calculated amount of external carbon source. When the anaerobic tank reaches the water level set by the anaerobic water level controller, the return sludge pump is turned off; thereafter, the corresponding submersible agitator is started to start stirring for anaerobic treatment. The anaerobic stirring reaction time is controlled at 1.5-3h. The activated sludge releases phosphorus through anaerobism, absorbs the added organic carbon source, and synthesizes the internal carbon source to achieve anaerobic treatment; during the anaerobic treatment process, the controller can also add external carbon source to the anaerobic tank according to the nitrate nitrogen concentration subsequently measured in the regulating tank; one of the two anaerobic tanks is always in an anaerobic state, and the other is idle waiting;

[0034] Anaerobic tank exhaust valve operation method: S3. During anaerobic treatment, close the anaerobic exhaust valve of the anaerobic tank to maintain the anaerobic environment. When the anaerobic tank is transferring activated sludge or adding an external carbon source, open the anaerobic exhaust valve;

[0035] Denitrification process: S4, after the denitrification tank cycle is completed, the activated sludge is transferred to the anaerobic tank in the empty waiting position, and the activated sludge that has been anaerobically treated in another anaerobic tank is immediately added to the denitrification tank through the sludge supply pump. At the same time, the nitrification liquid transfer pump transfers the secondary effluent of the sewage treatment plant in the regulating tank to the denitrification tank until it reaches the water level set by the denitrification water level controller; then the denitrification tank starts the corresponding submersible agitator and starts the anoxic denitrification process until the denitrification end point;

[0036] Denitrification endpoint control method: S5. The controller continuously reads the monitoring data of the denitrification pH online detector, ORP online detector and conductivity online detector in the denitrification tank. When the pH rises during the falling process, the pH can be used as a reliable parameter for denitrification endpoint control, but it has not yet reached the denitrification endpoint. When the pH turns from rising to falling, it indicates that the denitrification reaction has reached the endpoint; at the same time, the lowest ORP control range is set to prevent the pH control method from failing. This ORP control range is lower than the ORP value corresponding to the denitrification endpoint when the pH normally controls the denitrification endpoint. When the ORP is lower than this ORP control range and there is no turning point increase during the pH falling process, the denitrification process is stopped; during the denitrification process, the conductivity changes from a rapid decline to a slow decline, fluctuates back and forth, or even rises as an auxiliary judgment basis for the denitrification endpoint;

[0037] Aerobic process: S6, after denitrification reaches the end point, the controller starts and controls the denitrification aeration pump through the denitrification inverter. The aeration time is 5-10 minutes, and the aeration intensity is such that the final DO concentration is greater than 1.5mg / L and less than 3mg / L;

[0038] Static sedimentation and drainage and sludge discharge process: S7, after the aerobic aeration is completed, the denitrification aeration pump and the corresponding submersible agitator are turned off, and the denitrification tank begins to settle for 10-30 minutes. Then, the electric valve of the decanter is opened, and the electric telescopic rod of the decanter is slowly lowered to drain the water. After the drainage is completed, the electric valve of the decanter is closed, and the electric telescopic rod of the decanter returns to its original position. The denitrification sludge discharge pump is turned on to discharge the remaining sludge. Then, the activated sludge in the denitrification tank is transferred to the anaerobic tank in the empty waiting state through the sludge supply pump. The denitrification tank cycle operation is completed, and the denitrification tank is re-added with nitrification liquid and activated sludge to start a new cycle. The entire system repeats the cycle operation;

[0039] Operation method of denitrification exhaust valve: S8. Open the denitrification exhaust valve when the denitrification tank is in the process of aeration, water intake, drainage and activated sludge transfer. Close the denitrification exhaust valve when the denitrification tank is in the process of anoxic stirring and static sedimentation to minimize air entry and reduce the need for external carbon sources.

[0040] In addition, an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method is provided, and the specific steps are as follows:

[0041] When the ammonia nitrogen concentration in the secondary effluent of the sewage treatment plant is high or the total nitrogen purification requirement is high, the secondary effluent of the sewage treatment plant needs to enter the nitrification tank to carry out aerobic nitrification treatment of the ammonia nitrogen in the secondary effluent. At this time, the water inlet can be selected in two ways: continuous water inlet and intermittent water inlet. The specific operation steps are as follows:

[0042] When continuous water inflow is used, the continuous water inflow mode, intermittent nitrification reaction endpoint, continuous aerobic nitrification and nitrification liquid transfer are as follows: S1, the controller continuously transports the secondary effluent of the sewage treatment plant to the upper part of the packing layer of the nitrification tank through the water inlet pump; when the water level reaches the control water level set by the nitrification water level controller, the controller controls the nitrification aeration pump through the nitrification inverter to start aeration, starting intermittent aerobic nitrification until the intermittent nitrification reaction reaches the nitrification reaction endpoint; thereafter, the controller switches the aeration volume of the nitrification tank to low aeration volume aeration, so that the DO concentration is greater than 2mg / L and less than 3mg / L, achieving continuous nitrification conversion of ammonia nitrogen in the subsequent continuous water inflow; when the nitrification tank reaches the intermittent nitrification endpoint and when the denitrification tank cycle operation is completed and the activated sludge in the denitrification tank is transferred to the anaerobic tank, the controller can transfer the nitrification liquid to the denitrification tank through the nitrification liquid transfer pump. After the transfer is completed, the nitrification aeration pump is turned off, and the nitrification tank continues to wait for the next water inflow to reach the set water level before restarting aeration, and this cycle is repeated;

[0043] When intermittent water inflow is used, the intermittent water inflow method, intermittent nitrification reaction endpoint and nitrification liquid transfer are as follows: S2: When the water inflow to the nitrification pool reaches the water level set by the nitrification water level controller, water inflow can be stopped; then aeration is started. When the nitrification reaction reaches the nitrification endpoint, aeration is stopped and the water is left to stand for a while; after that, when the denitrification tank cycle is completed, the controller transfers the nitrification liquid to the denitrification tank via the nitrification liquid transfer pump. Only after the transfer is completed can the nitrification pool be refilled with water, and this cycle is repeated;

[0044] Intermittent nitrification endpoint control method: S3, the controller controls the nitrification reaction endpoint through the nitrification pH online detector and the nitrification DO online detector installed in the nitrification tank. The controller controls the aeration volume to make the DO less than 3mg / L. The controller uses the increase in pH value at the end of the nitrification reaction, accompanied by a sudden jump in the DO value of the nitrification DO online detector, as the method for controlling the nitrification reaction endpoint;

[0045] Nitrate nitrogen determination and external carbon source calculation: S4, the first sampling pump and the second sampling pump sample the water from the inlet pipe and the nitrification tank at regular intervals, and the nitrate nitrogen concentration is measured by the nitrate nitrogen online detector; the controller calculates the amount of external carbon source required for denitrification in this cycle based on the set carbon-nitrogen ratio (or if the total nitrogen concentration of the inlet water is known, the amount of external carbon source required to be added to the anaerobic tank is calculated based on the total nitrogen concentration of the inlet water);

[0046] Activated sludge transfer, external carbon source and anaerobic treatment: At the end of each cycle of S5, the activated sludge in the denitrification tank is transferred to the empty (no activated sludge) anaerobic tank in turn through the return sludge pump; at the same time, the controller adds external carbon source to the anaerobic tank in a quantitative manner based on the calculated amount of external carbon source through the external carbon source quantitative pump. When the anaerobic tank reaches the water level set by the anaerobic water level controller, the return sludge pump is turned off; then, the corresponding submersible agitator is started to start stirring and anaerobic treatment is carried out. The anaerobic stirring reaction time is controlled at 1.5h-3h. The activated sludge releases phosphorus through anaerobism, absorbs the added organic carbon source, and synthesizes the internal carbon source to achieve anaerobic treatment; during the anaerobic treatment process, the controller can also add organic carbon source to the anaerobic tank according to the nitrate nitrogen concentration measured after the subsequent nitrification reaction.

[0047] Anaerobic tank exhaust valve operation method: S6. During anaerobic treatment, close the anaerobic exhaust valve of the anaerobic tank to maintain the anaerobic environment. When the anaerobic tank transfers activated sludge or adds external carbon source, open the anaerobic exhaust valve. One anaerobic tank is always in the anaerobic state, and the other is idle waiting.

[0048] Denitrification process: S7, after the denitrification tank cycle ends, the activated sludge is transferred to the anaerobic tank in the empty waiting state, and the activated sludge that has been anaerobically treated in another anaerobic tank is immediately added to the denitrification tank through the sludge supply pump. At the same time, the nitrification liquid transfer pump transfers the nitrification liquid from the nitrification tank to the denitrification tank until it reaches the water level set by the denitrification water level controller; then the denitrification tank starts the corresponding submersible agitator and starts the anoxic denitrification process until the denitrification end point;

[0049] Denitrification endpoint control method: S8, the controller continuously reads the monitoring data of the denitrification pH online detector, ORP online detector and conductivity online detector in the denitrification tank. When the pH rises during the falling process, the pH can be used as a reliable parameter for denitrification endpoint control, but it has not yet reached the denitrification endpoint. When the pH turns from rising to falling, it indicates that the denitrification reaction has reached the endpoint; at the same time, the lowest ORP control range is set to prevent the pH control method from failing. This ORP control range is lower than the ORP value corresponding to the denitrification endpoint when the pH normally controls the denitrification endpoint. When the ORP is lower than this ORP control range and there is no turning point increase during the pH falling process, the denitrification process is stopped; during the denitrification process, the conductivity changes from a rapid decline to a slow decline, fluctuates back and forth, or even rises as an auxiliary judgment basis for the denitrification endpoint;

[0050] Aerobic process: S9, after denitrification reaches the end point, the controller starts and controls the denitrification aeration pump through the denitrification inverter. The aeration time is 5-10 minutes, and the aeration intensity is such that the final DO concentration is greater than 1.5mg / L and less than 3mg / L;

[0051] Static sedimentation and drainage and sludge discharge process: S10, after the aerobic aeration is completed, the denitrification aeration pump and the corresponding submersible agitator are turned off, and the denitrification tank begins to settle for 10-30 minutes. Then, the electric valve of the decanter is opened, and the electric telescopic rod of the decanter is slowly lowered to drain the water. After the drainage is completed, the electric valve of the decanter is closed, and the electric telescopic rod of the decanter returns to its original position. The denitrification sludge discharge pump is turned on to discharge the remaining sludge. Then, the activated sludge in the denitrification tank is transferred to the anaerobic tank in the empty waiting position through the sludge supply pump. The denitrification tank cycle operation is completed, and the denitrification tank is re-added with nitrification liquid and activated sludge after anaerobic treatment to start a new cycle. The entire system operates in this repeated cycle.

[0052] Operation method of denitrification exhaust valve: S11. Open the denitrification exhaust valve when the denitrification tank is in the process of aeration, water intake, drainage and activated sludge transfer. Close the denitrification exhaust valve when the denitrification tank is in the process of anoxic stirring and static sedimentation to minimize air entry and reduce the need for external carbon sources.

[0053] The present invention is an intermittent intelligent low-activated sludge concentration nitrogen and phosphorus deep purification system designed for the lower nitrogen and phosphorus concentrations and lower organic carbon concentrations of the secondary effluent from a sewage treatment plant compared to domestic sewage. The system is based on the principle of double-sludge denitrification technology, separates the nitrification process and the denitrification process into two reactors, adopts a lower activated sludge concentration, and utilizes intelligent online control technology. Through the steps of nitrification, anaerobic treatment of activated sludge with precise addition of carbon source, anoxic denitrification, aerobic stripping, and precise online control of the nitrification and denitrification endpoints, the purified water quality finally reaches the surface water quality standard Class III or above, and completely solves the problem of eutrophication pollution of receiving water bodies caused by direct discharge of secondary effluent from existing sewage treatment plants. It is of great significance to the upgrading and transformation of existing sewage treatment plants, the protection of water bodies in water sources, the eutrophication prevention of oligotrophic and mesotrophic lakes, and the water quality restoration of eutrophic water bodies.

[0054] Principle of Use: The secondary effluent from a sewage treatment plant has a low organic matter content. Nitrogen mainly exists in the form of nitrate nitrogen and a small amount of ammonia nitrogen, and phosphorus mainly exists as orthophosphate. Based on the principle that dual sludge denitrification can simultaneously remove nitrogen and phosphorus, the secondary effluent from the sewage treatment plant first enters the nitrification tank. Through aerobic aeration nitrification reaction, the endpoint of the nitrification reaction is controlled and all residual ammonia nitrogen is oxidized to nitrate nitrogen. The nitrate nitrogen concentration is measured or the required external carbon source is calculated based on the total nitrogen concentration of the influent. The external carbon source is accurately added to the anaerobic tank and anaerobically mixed with the activated sludge. Microorganisms release phosphorus and absorb the external carbon source, which is converted into an internal carbon source for the microorganisms. After the denitrification tank completes its previous cycle, the activated sludge is transferred to an empty, waiting anaerobic tank. The activated sludge from the other anaerobic tank is then transferred to the denitrification tank for anoxic mixing with the secondary effluent from the nitrification treatment, triggering anoxic denitrification. By controlling the endpoint of the denitrification reaction, complete denitrification of nitrate and nitrite nitrogen is achieved, while phosphorus absorption is also achieved through denitrification. After denitrification, aerobic aeration is performed to further absorb phosphorus and remove nitrogen generated by denitrification, facilitating the settling of the activated sludge. The sludge is then allowed to settle and drained through a decanter. After this, the remaining sludge is discharged and the activated sludge from the denitrification tank is transferred to the empty, waiting anaerobic tank. The two anaerobic tanks then alternately treat the activated sludge. This cyclical system of a nitrification tank, two anaerobic tanks, and a denitrification tank can be repeated.

[0055] Furthermore, in addition to being applicable to secondary effluent from sewage treatment plants, the patent is also applicable to surface water from rivers and lakes and agricultural wastewater with severe eutrophication pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a structural schematic diagram of an intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system and method of the present invention.

[0057] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0058] 1. Denitrification tank, 2. Anaerobic tank, 3. External carbon source storage tank, 4. Decanter, 5. Controller, 6. Denitrification exhaust valve, 7. Denitrification sludge pump, 8. Sludge supply pump, 9. Sludge return pump, 10. External carbon source quantitative pump, 11. Decanter electric valve, 12. Denitrification pH online detector, 13. ORP online detector, 14. Conductivity online detector, 15. Denitrification DO online detector, 16. Submersible mixer, 17. Denitrification inverter, 18. Denitrification aeration pump, 19. Denitrification gas flow sensor, 20. Nitrification aeration head, 21. Denitrification water level controller, 22. Nitrification tank, 23. Water inlet pump, 24. Nitrification inverter, 25. Nitrification aeration pump, 26. Nitrification gas flow sensor, 27. Sieve plate, 28. Nitrification aeration head, 29. Nitrification pH online detector, 30. Nitrification DO online detector, 31. First sampling pump, 32. Second sampling pump, 33. Nitrate nitrogen online detector, 34. Nitrification water level controller, 35. Nitrification liquid transfer pump, 36. Anaerobic water level controller, 37. Anaerobic exhaust valve, 38. Nitrification sludge discharge valve. DETAILED DESCRIPTION

[0059] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0060] Principles and characteristics of main components:

[0061] Nitrification tank 22: (When the secondary effluent from the sewage treatment plant has a high ammonia nitrogen concentration or requires high total nitrogen purification, the secondary effluent must enter the nitrification tank 22 for aerobic nitrification of the ammonia nitrogen in the secondary effluent.) The nitrification tank 22 is cylindrical, with a sieve plate 27 positioned above the bottom. A gas pipeline and multiple nitrification aeration heads 28 are installed above the sieve plate 27. The filler material consists of volcanic rock, ceramsite, activated carbon granules, zeolite, and quartz sand, with a particle size of 0.5-2.5 cm. The secondary effluent from the sewage treatment plant is connected to the nitrification tank 22 via an inlet pipeline and an inlet pump 23. The bottom outlet of the nitrification tank 22 is connected to the denitrification tank 1 via a pipeline and a nitrification liquid transfer pump 35. A sludge discharge pipe and a nitrification sludge discharge valve 38 are installed at the bottom of the nitrification tank. Multiple nitrification aeration heads 28 are connected in sequence to the nitrification gas flow sensor 26 and the outlet of the nitrification aeration pump 25 via gas pipelines. A nitrification water level controller 34 is installed above the nitrification tank 22, and an online nitrification pH monitor 29 and an online nitrification DO monitor 30 are located below the water level. The nitrification inverter 24 is electrically connected to the nitrification aeration pump 25. The controller 5 is electrically connected to the nitrification inverter 24, the nitrification liquid transfer pump 35, the nitrification sludge discharge valve 38, the nitrification gas flow sensor 26, the nitrification water level controller 34, the online nitrification pH monitor 29, and the online nitrification DO monitor 30. The controller 5 controls the start and operating frequency of the nitrification aeration pump 25 via the nitrification inverter 24. It reads the gas flow data from the nitrification gas flow sensor 26 and the DO concentration measured by the online nitrification DO monitor 30 to control the aeration intensity and, consequently, the DO concentration in the nitrification tank 22. The nitrification inverter 24 periodically adjusts the nitrification aeration pump 25 to high aeration intensity, and then completely drains the nitrification tank 22 to remove any detached and settled biofilm and activated sludge, thereby preventing packing clogging.

[0062] Equalization Tank: When the ammonia nitrogen concentration in the secondary effluent of a sewage treatment plant is low, or when the total nitrogen requirement for the effluent is low, the nitrification tank 22 is not required. The nitrification tank 22 can be replaced with an equalization tank without the packing, aeration pump, aeration head, first sampling pump 31, online pH meter, and online DO meter. The equalization tank retains the nitrification water level controller 34, nitrification liquid transfer pump 35, and corresponding piping, and is equipped with an online nitrate nitrogen detector 33 and second sampling pump 32. The equalization tank temporarily stores continuous or intermittent influent water. When the denitrification tank 1 cycle ends, the secondary effluent stored in the equalization tank is transferred to the denitrification tank 1 via the nitrification liquid transfer pump 35.

[0063] Nitrate Nitrogen Determination: When using a nitrification tank 22, the water inlet of the first sampling pump 31 is connected to the connecting pipe between the water inlet pump 23 and the secondary effluent of the sewage treatment plant. The water inlet of the second sampling pump 32 is connected to the interior of the nitrification tank 22. The water inlet of the online nitrate nitrogen detector 33 is connected to the water outlets of the first sampling pump 31 and the second sampling pump 32, respectively. When using a regulating tank, the water inlet of the second sampling pump 32 is connected to the interior of the regulating tank, and the water outlet of the second sampling pump 32 is connected to the water inlet of the online nitrate nitrogen detector 33. The controller 5 is electrically connected to the first sampling pump 31, the second sampling pump 32, and the online nitrate nitrogen detector 33.

[0064] External carbon source storage tank 3: An external carbon source outlet is provided at the bottom of the external carbon source storage tank 3 and the external carbon source outlet is connected to two external carbon source holes through two carbon supply pipes respectively. An external carbon source metering pump 10 is installed on both carbon supply pipes; the controller 5 is electrically connected to the two external carbon source metering pumps 10.

[0065] Anaerobic Tanks 2: Two anaerobic tanks 2 are provided, each with a mud inlet and outlet at the bottom and a carbon source port at the top. Both inlet and outlet ports are connected to the mud inlet and outlet of denitrification tank 1 via a mud supply pipe and a mud return pipe, respectively. Mud supply pumps 8 are installed on each mud supply pipe, and mud return pumps 9 are installed on each mud return pipe. Exhaust pipes are installed at both ends of the anaerobic tanks, each equipped with an anaerobic water level controller 36 and an anaerobic exhaust valve 37. Submersible agitators 16 are installed within each anaerobic tank 2 for mixing during anaerobic treatment. A controller 5 is electrically connected to the mud supply pumps 8, mud return pumps 9, anaerobic water level controller 36, submersible agitators 16, and anaerobic exhaust valve 37.

[0066] Denitrification tank: The denitrification tank 1 is connected to the anaerobic tank 2 through the return sludge pump 9 and the pipeline. The anaerobic tank 2 is connected to the denitrification tank 1 through the sludge supply pump 8 and the pipeline. The denitrification tank 1 is used to discharge the purified water through the decanter 4, the corresponding pipeline, and the decanter electric valve 11 on the pipeline; the bottom of the denitrification tank 1 is used to discharge the remaining activated sludge to the outside through the denitrification sludge pump 7 and the corresponding pipeline; the bottom of the denitrification tank 1 is conical, with a cylinder on the top. A denitrification water level controller 21 and a water level line are set near the top. 1 is provided with an exhaust pipe at the top and a denitrification exhaust valve 6 on the pipe; when the denitrification tank 1 is in anoxic stirring denitrification, the denitrification exhaust valve 6 is closed to prevent outside air from entering; when the denitrification tank 1 is in water intake, drainage, mud discharge or aeration, the denitrification exhaust valve 6 is opened; at the lower part of the denitrification tank 1, a gas pipeline and multiple denitrification aeration heads 20 are provided above the cone, and the multiple denitrification aeration heads 20 are connected to the denitrification gas flow sensor 19 and the denitrification aeration pump 18 in sequence through the gas pipeline; at the lower part of the denitrification tank 1, a submersible is installed. Agitator 16; below the water level line, a denitrification pH online detector 12, an ORP online detector 13, an electrical conductivity online detector 14, and a denitrification DO online detector 15 are set; a denitrification frequency converter 17 is electrically connected to a denitrification aeration pump 18, a controller 5 is connected to a decanter 4, a decanter electric valve 11, a denitrification sludge pump 7, a denitrification water level controller 21, a denitrification exhaust valve 6, a denitrification frequency converter 17, a denitrification gas flow sensor 19, a denitrification pH online detector 12, an ORP online detector 13, the conductivity online detector 14, the submersible mixer 16 and the denitrification DO online detector 15 are electrically connected; the controller 5 accurately controls the denitrification reaction endpoint through an internal program, controls the start and operating frequency of the denitrification aeration pump 18 through the denitrification inverter 17, reads the gas flow value of the denitrification gas flow sensor 19, the DO concentration of the denitrification DO online detector and the ORP value of the ORP online detector 13, controls the aeration intensity of the denitrification tank 1, and further controls the DO concentration or the ORP range.

[0067] Process operation and running method:

[0068] When the ammonia nitrogen concentration in the secondary effluent of the sewage treatment plant is high or the total nitrogen purification requirements are high, the secondary effluent of the sewage treatment plant needs to enter the nitrification tank to perform aerobic nitrification treatment on the ammonia nitrogen in the secondary effluent. When the inlet water is continuously inlet, the specific operating steps of the nitrification tank 22 are as follows: When the nitrification tank 22 is continuously inletted by the water inlet pump 23, when the water level reaches the control water level set by the nitrification water level controller 34, the controller 5 controls the nitrification aeration pump 25 through the nitrification inverter 24 to start aeration and aerobic nitrification; the controller 5 controls the nitrification end point through the nitrification pH online detector 29 and the nitrification DO online detector 30 set in the nitrification tank 22, and the aeration amount should be less than 3mg / L; the controller 5 controls the nitrification end point according to the nitrification reaction end point. , the pH value increases, and the DO value of the nitrification DO online detector 30 suddenly jumps as a method for controlling the end point of the nitrification reaction; after the nitrification reaction is completed, the controller 5 adjusts the aeration volume through the nitrification inverter 24, switches the aeration volume of the nitrification tank 22 to low aeration volume aeration, so that the DO concentration is greater than 2 mg / L and less than 3 mg / L, and aerobic nitrification conversion of the subsequent ammonia nitrogen in the influent is carried out until the nitrification liquid is transferred from the nitrification tank 22 to the denitrification tank 1, and then the nitrification aeration pump 25 is turned off, and the nitrification tank 22 starts a new cycle. When water is fed in intermittently, the specific operating steps of the nitrification tank 22 are as follows: as long as the water inflow to the nitrification tank 22 reaches the water level set by the nitrification water level controller 34, the water inflow can be stopped and aeration can be started. The controller continuously monitors the changes in pH and DO values. When the pH value increases and the DO value suddenly jumps, it indicates that the nitrification reaction has reached the end point. Then, aeration is stopped and the denitrification tank 1 cycle is completed. Then, the nitrification liquid can be transferred to the denitrification tank 1. When the nitrification liquid is transferred, water can be re-fed and the nitrification tank 22 can start a new cycle.

[0069] When the ammonia nitrogen concentration in the secondary effluent of the sewage treatment plant is low or the requirement for total nitrogen purification is not high, the secondary effluent of the sewage treatment plant does not need to be aerobic nitrified, nor does it need a nitrification tank 22. The secondary effluent of the sewage treatment plant only needs to be stored in the regulating tank for treatment in the denitrification tank 1. The operation mode of the regulating tank is as follows: the secondary effluent of the sewage treatment plant flows into the regulating tank continuously or intermittently. When the operation cycle of the denitrification tank 1 ends, the secondary effluent of the sewage treatment plant in the regulating tank is transferred to the denitrification tank 1 through the nitrification liquid transfer pump 35 to be mixed with the anaerobic activated sludge to carry out a denitrification reaction.

[0070] Nitrate Nitrogen Measurement and External Carbon Source Calculation: When using a nitrification tank 22, the first and second sampling pumps 31 and 32 periodically sample the water from the inlet pipe and nitrification tank 22. The online nitrate nitrogen detector 33 measures the nitrate nitrogen concentration and calculates the amount of external carbon source required for denitrification during this cycle based on the set carbon-nitrogen ratio. When using an equalization tank, the online nitrate nitrogen detector 33 uses the second inlet pump 32 to measure the nitrate nitrogen concentration of the sewage treatment plant's secondary effluent within the equalization tank and calculates the amount of external carbon source required for denitrification during this cycle based on the set carbon-nitrogen ratio. If the total nitrogen concentration of the inlet water is known, the online nitrate nitrogen detector 33, first and second sampling pumps 31 and 32, and the corresponding piping can be omitted.

[0071] The external carbon source storage tank 3 and anaerobic tank 2 operate as follows: At the end of each cycle in denitrification tank 1, activated sludge from denitrification tank 1 is transferred to the empty (deactivated sludge-free) anaerobic tank 2 via the return sludge pump 9. Simultaneously, based on the calculated amount of added carbon source, the controller 5 quantitatively adds external carbon source from the external carbon source storage tank 3 to the anaerobic tank 2 via the external carbon source metering pump 10. When the water level in anaerobic tank 2 reaches the anaerobic water level controller 36, the return sludge pump 9 is shut off, and the corresponding submersible agitator 16 is activated to initiate agitation, thus achieving anaerobic treatment. The anaerobic agitation reaction time is controlled between 1.5 and 3 hours. During anaerobic treatment, the activated sludge releases phosphorus and absorbs the added organic carbon source, synthesizing an internal carbon source, thereby achieving anaerobic treatment. During anaerobic treatment, the anaerobic exhaust valve 37 in anaerobic tank 2 is closed to maintain the anaerobic environment. The anaerobic exhaust valve 37 is opened when transferring activated sludge or adding an external carbon source to anaerobic tank 2. One of the anaerobic tanks 2 is always in the anaerobic state, and the other is idle waiting.

[0072] The operation mode of the denitrification tank 1 is as follows: after the denitrification tank 1 is drained and sludged, the activated sludge is transferred to the empty anaerobic tank 2. At the same time, the external carbon source metering pump 10 quantitatively adds an external carbon source to the anaerobic tank 2, and the anaerobic tank 2 enters anaerobic operation. The denitrification tank 1 begins a new operation cycle. The nitrification liquid transfer pump 35 transfers the nitrification supernatant or the secondary effluent of the sewage treatment plant in the regulating tank to the denitrification tank 1. At the same time, the activated sludge that has been anaerobically treated in advance in the anaerobic tank 2 is returned to the denitrification tank 1 through the sludge supply pump 8. Then, the denitrification tank 1 starts the corresponding submersible agitator 16 to start the anoxic denitrification process. At this time, the controller 5 continuously reads the monitoring data of the denitrification tank 1 on the denitrification pH online detector 12, the ORP online detector 13 and the conductivity online detector 14. When the pH rises during the falling process, the mark close to the pH can be used as the denitrification end point judgment parameter. When the pH changes from rising to falling, it indicates that the denitrification reaction has reached the end point. At this time, the general situation is that the conductivity will slow down, fluctuate, stagnate or even increase. The controller 5 uses the rise and then fall of pH as the main basis for judging the denitrification endpoint, and uses conductivity as an auxiliary basis to judge the denitrification endpoint. At the same time, a minimum ORP control range is set. This ORP control range is lower than the ORP value corresponding to the pH normal control of the denitrification endpoint to avoid the pH continuously falling, the pH never rising or rising and then falling. At the same time, the slowdown of the conductivity decline rate, the fluctuation, stagnation or even increase are used as auxiliary judgment bases to avoid delaying the denitrification endpoint, resulting in the conversion of the anoxic environment into an anaerobic environment and the release of phosphorus, which affects the purification of phosphorus. When denitrification reaches its endpoint, the denitrification inverter 17 immediately activates and controls the denitrification aeration pump 18. The aeration time is controlled to 5-10 minutes. The optimal aeration intensity is to achieve a final DO concentration greater than 1.5 mg / L and less than 3 mg / L. Aerobic aeration enhances the further absorption and removal of phosphorus and blows off the nitrogen generated by denitrification, facilitating the sedimentation and separation of the activated sludge. After aerobic aeration is completed, the denitrification inverter 17 shuts off the denitrification aeration pump 18, the submersible agitator 16 is turned off, and static sedimentation begins for 10-30 minutes. The decanter valve 11 is then opened, and the electric support rod of the decanter 4 is slowly lowered to drain the water. After drainage is complete, the decanter valve 11 is closed, the electric support rod of the decanter 4 is raised back to its original position, and the denitrification sludge pump 7 is activated to discharge the remaining activated sludge. Simultaneously, the return sludge pump 9 is activated to transfer some or all of the activated sludge to the vacant, waiting anaerobic tank 2. Denitrification tank 1 starts a new cycle and runs over and over again.

[0073] The controller 5 controls the denitrification tank 1's drainage water level and inlet water level by controlling the denitrification tank 1's decanter 4's elevation during drainage. Simultaneously, the anaerobic tank 2's effective volume is controlled to be 1 / 40 to 1 / 5 of the denitrification tank 1's effective volume, and the sludge retention time is controlled to be 8 to 30 days, thereby maintaining a relatively low concentration of activated sludge in the denitrification tank. This allows the amount of added carbon source, the phosphorus content released by anaerobic means, and the nitrogen and phosphorus content of the sewage treatment plant's secondary effluent to match, thereby promoting the growth of denitrifying and phosphorus-removing organisms and enabling nitrogen and phosphorus to be simultaneously removed and absorbed by the microbial denitrification process. This prevents insufficient nitrate nitrogen concentration from causing a decrease in phosphorus removal efficiency and even a large outflow of phosphorus. The lower the influent total nitrogen concentration, the smaller the required ratio of the anaerobic tank 2's effective volume to the denitrification tank 1's effective volume. When the influent phosphorus content is high and the phosphorus purification efficiency is poor, the phosphorus removal efficiency can be improved by reducing the sludge retention time.

[0074] Applicable scope: Secondary effluent from sewage treatment plants with TN concentration greater than 4 mg / L and less than 30 mg / L, TP concentration greater than 0.2 mg / L and less than 3 mg / L, as well as surface water from rivers and lakes and agricultural wastewater with serious eutrophication pollution.

[0075] To achieve simultaneous nitrogen and phosphorus removal, the denitrification tank's denitrification cycle is controlled to run for 20-60 minutes. Controller 5 adjusts the denitrification cycle by adjusting the carbon-nitrogen ratio. A shorter denitrification cycle can reduce phosphorus removal efficiency, while a longer cycle can achieve deep, simultaneous nitrogen and phosphorus removal, but it can reduce the efficiency of denitrification tank 1 and the entire system.

[0076] The added carbon sources were methanol, sodium acetate, acetic acid and alcohol.

[0077] Example 1: When the CODcr concentration of the secondary effluent from a sewage treatment plant is 13 mg / L, the total nitrogen concentration is 15 mg / L, the total phosphorus concentration is 1 mg / L, and the ammonia nitrogen concentration is 1.2 mg / L, and the effective volume of the anaerobic tank is 1.5 / 20 of the effective volume of the denitrification tank, the secondary effluent from the sewage treatment plant first enters the nitrification tank 22 for nitrification, converting all ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and then enters the denitrification tank for denitrification, denitrification and phosphorus removal, aerobic treatment, and sedimentation. The carbon-nitrogen ratio of the added carbon source is 5.6, and the added carbon source is sodium acetate. The effluent CODcr concentration is 11 mg / L, the total nitrogen concentration is 0.7 mg / L, and the total phosphorus concentration is 0.19 mg / L. Deep purification of nitrogen and phosphorus is achieved, and the total nitrogen and total phosphorus indicators of the effluent meet the surface water quality standards of Class III or higher for lakes and reservoirs. The inlet volume of the denitrification tank is 18.5 / 20 of the effective volume. The water inlet time is 20 minutes, the anoxic stirring time is 35-42 minutes, the pH changes from decreasing to increasing, and then turns to decreasing to reach the denitrification end point, the ORP minimum control range is -170mv, static sedimentation is 10 minutes, drainage is 30 minutes, aeration time is 10 minutes, the final DO concentration of aeration is 2.2mg / L, the sludge retention time is 15 days, the operation time of each cycle is 120 minutes, and 12 cycles are operated per day.

[0078] Example 2: When the influent CODcr concentration of the secondary effluent of a sewage treatment plant is 12 mg / L, the total nitrogen concentration is 7 mg / L, the ammonia nitrogen concentration is 0.9 mg / L, and the total phosphorus concentration is 0.6 mg / L, and the effective volume of the anaerobic tank is 1 / 20 of the denitrification tank, the secondary effluent of the sewage treatment plant first enters the nitrification tank 22 for nitrification to convert all ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and then enters the denitrification tank for denitrification, dephosphorization, aerobic treatment, and sedimentation. The carbon-nitrogen ratio of the added carbon source is 6.2, and the added carbon source is sodium acetate. The effluent CODcr concentration is 8.5 mg / L, the total nitrogen concentration is 0.6 mg / L, and the total phosphorus concentration is 0.2 mg / L. Deep purification of nitrogen and phosphorus is achieved, and the total nitrogen and total phosphorus indicators of the effluent meet the surface water quality standards of Class III or above. The influent volume of the denitrification tank is 19.2 / 20 of the effective volume. The water inlet time is 20 minutes, the anoxic stirring time is 20-35 minutes, the pH changes from decreasing to increasing, and then turns to decreasing to reach the denitrification end point, the ORP minimum control range is -165mv, the aerobic aeration time is 10 minutes, the static sedimentation is 10 minutes, the drainage is 30 minutes, the sludge retention time is 14 days, the final DO concentration of aeration is 2.4mg / L, the cycle operation time is less than 120 minutes, and more than 12 cycles are operated per day.

[0079] Example 3: When the influent CODcr concentration of the secondary effluent from a sewage treatment plant is 18 mg / L, the total nitrogen concentration is 23.5 mg / L, the ammonia nitrogen concentration is 1.8 mg / L, and the total phosphorus concentration is 1.6 mg / L, the secondary effluent from the sewage treatment plant first enters the nitrification tank 22 for nitrification, converting all ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and then enters the denitrification tank for denitrification, dephosphorization, aerobic treatment, and sedimentation. The anaerobic tank has an effective volume of 2 / 20 of the denitrification tank, a carbon-nitrogen ratio of 5.2, and sodium acetate as the added carbon source. The effluent CODcr concentration is 11 mg / L, the total nitrogen concentration is 0.8 mg / L, and the total phosphorus concentration is 0.16 mg / L, achieving deep purification of nitrogen and phosphorus. The total nitrogen and total phosphorus indicators of the effluent meet the surface water quality standards for lakes and reservoirs of Class III or higher. The influent volume of the denitrification tank is 18.5 / 20 of the effective volume. The water inlet time is 20 minutes, the anoxic stirring time is 40-45 minutes, the pH changes from decreasing to increasing, and then turns to decreasing to reach the denitrification end point, the ORP minimum control range is -175mv, the aerobic aeration time is 10 minutes, the static sedimentation is 10 minutes, the drainage is 30 minutes, the sludge retention time is 16 days, the final DO concentration of aeration is 2.6mg / L, the average cycle operation time is 120 minutes, and 12 cycles are operated per day.

[0080] Compared with the pyrite autotrophic denitrification process, the microalgae biological treatment system, and the solid organic carbon source denitrification process (see Table 1), this process has a shorter cycle time, high reactor operation efficiency, no by-products, and can simultaneously achieve deep removal of nitrogen and phosphorus. It is more suitable for water body restoration, deep reuse of wastewater, and recycling of water resources.

[0081] Table 1. Comparison of this process's intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system with various advanced processes

[0082]

[0083] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system, characterized in that: include: A denitrification tank (1), wherein the top of the denitrification tank (1) is provided with a denitrification exhaust hole, the bottom of the denitrification tank (1) is provided with a nitrification liquid inlet hole, a denitrification mud discharge hole, a mud inlet hole and a mud discharge hole, and a side wall thereof is provided with a perforation, a denitrification mud discharge pump (7) is installed at the denitrification mud discharge hole, and a denitrification exhaust valve (6) is installed at the denitrification exhaust hole; two anaerobic tanks (2), the bottom ends of the two anaerobic tanks (2) are provided with mud inlet and outlet holes and the top ends are provided with an external carbon source hole, and the two mud inlet and outlet holes are connected through a mud supply pipe and a mud return pipe. The two anaerobic tanks (2) are connected to the mud inlet and the mud outlet respectively, and the two mud supply pipes are both installed with a mud supply pump (8), and the two mud return pipes are both installed with a mud return pump (9); the tops of the two anaerobic tanks (2) are both installed with an exhaust pipe, and the two exhaust pipes are both installed with an anaerobic water level controller (36) and an anaerobic exhaust valve (37); the external carbon source storage tank (3), the bottom end of the external carbon source storage tank (3) is provided with an external carbon source outlet, and the external carbon source outlet is connected to the two external carbon sources through two carbon supply pipes. The holes are connected, and an external carbon source metering pump (10) is installed on each of the two carbon supply pipes; a decanter (4), the decanter (4) is tilted and fixed on the electric telescopic rod in the denitrification tank (1) from top to bottom, and its water inlet is placed in the denitrification tank (1), the water outlet of the decanter (4) passes through the perforation, and a decanter electric valve (11) is installed on the pipe wall passing through the perforation; a plurality of submersible agitators (16), the plurality of submersible agitators (16) are respectively installed in the denitrification tank (1). A controller (5) is provided in the nitrification tank (1) and the two anaerobic tanks (2); the controller (5) is electrically connected to the denitrification exhaust valve (6), the denitrification sludge pump (7), the two sludge supply pumps (8), the two sludge return pumps (9), the two anaerobic water level controllers (36), the two anaerobic exhaust valves (37), the two external carbon source metering pumps (10), the decanter (4), the decanter electric valve (11) and the plurality of submersible agitators (16); The intelligent intermittent dual-sludge denitrification nitrogen and phosphorus deep purification system further includes a denitrification pH online detector (12), an ORP online detector (13), an electrical conductivity online detector (14), and a denitrification DO online detector (15); the denitrification pH online detector (12), the ORP online detector (13), the electrical conductivity online detector (14), and the denitrification DO online detector (15) are installed at intervals in the denitrification tank (1) and are all electrically connected to the controller (5); The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system further comprises a denitrification frequency converter (17), a denitrification aeration pump (18), a denitrification gas flow sensor (19), a plurality of denitrification aeration heads (20) and a denitrification water level controller (21); the plurality of denitrification aeration heads (20) are fixed at intervals in the lower inner part of the denitrification tank (1); the gas outlet of the denitrification aeration pump (18) passes through the denitrification tank (1) and is connected to the plurality of denitrification aeration heads (20); the denitrification aeration pump (18) ... The denitrification gas flow sensor (19) is installed on the connecting pipe between the denitrification aeration pump (18) and the plurality of denitrification aeration heads (20); the denitrification frequency converter (17) is electrically connected to the denitrification aeration pump (18); the denitrification water level controller (21) is installed on the inner upper part of the denitrification tank (1); the controller (5) is electrically connected to the denitrification frequency converter (17), the denitrification gas flow sensor (19) and the denitrification water level controller (21) respectively; The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system also includes a nitrification tank (22), a water inlet pump (23), a nitrification frequency converter (24), a nitrification aeration pump (25), a nitrification gas flow sensor (26), a plurality of nitrification aeration heads (28) and a nitrification water level controller (34); the water inlet of the water inlet pump (23) is connected to the secondary effluent of the sewage treatment plant and the water outlet thereof is connected to the nitrification tank (22); the bottom end of the nitrification tank (22) is provided with a nitrification mud discharge hole and a nitrification liquid discharge hole, the nitrification mud discharge hole is installed with a nitrification mud discharge valve (38), the nitrification liquid discharge hole is connected to the nitrification liquid inlet hole through the nitrification liquid transfer pump (35); the lower end of the interior of the nitrification tank (22) is installed with a sieve plate (27) and the nitrification tank (22) corresponds to the A plurality of nitrification aeration heads (28) are fixed above the sieve plate (27) and a plurality of fillers are placed thereon; the nitrification frequency converter (24) is electrically connected to the nitrification aeration pump (25); the air outlet of the nitrification aeration pump (25) passes through the nitrification tank (22) through a gas pipeline and is in communication with the plurality of nitrification aeration heads (28); the nitrification gas flow sensor (26) is installed on the connecting pipe between the nitrification aeration pump (25) and the plurality of nitrification aeration heads (28); the nitrification water level controller (34) is fixed in the nitrification tank (22); the controller (5) is electrically connected to the water inlet pump (23), the nitrification frequency converter (24), the nitrification gas flow sensor (26) and the nitrification water level controller (34), respectively; The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system further includes a nitrification pH online detector (29) and a nitrification DO online detector (30), wherein the nitrification pH online detector (29) and the nitrification DO online detector (30) are fixed at intervals in the nitrification tank (22); the controller (5) is electrically connected to the nitrification pH online detector (29) and the nitrification DO online detector (30), respectively; The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system further comprises a first sampling pump (31), a second sampling pump (32) and a nitrate nitrogen online detector (33); the water inlet of the first sampling pump (31) is connected to the connecting pipe between the water inlet pump (23) and the secondary effluent of the sewage treatment plant; the water inlet of the second sampling pump (32) is connected to the interior of the nitrification tank (22); the water inlet of the nitrate nitrogen online detector (33) is connected to the water outlet of the first sampling pump (31) and the water outlet of the second sampling pump (32); the controller (5) is electrically connected to the nitrate nitrogen online detector (33) and the first sampling pump (31) and the second sampling pump (32); The effective volume of the anaerobic tank (2) is 1 / 40 to 1 / 5 of the effective volume of the denitrification tank (1), and the higher the total nitrogen concentration of the influent, the higher the ratio. The sludge retention time is 8 to 30 days.

2. An intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method, characterized in that: The invention comprises an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system as described in claim 1, and the specific steps are as follows: when the ammonia nitrogen concentration of the secondary effluent of the sewage treatment plant is low or the total nitrogen purification requirement is not high, the secondary effluent of the sewage treatment plant may not be nitrified, and the nitrification tank (22) is not used, and the specific operation steps are as follows; water inlet mode, nitrate nitrogen determination and carbon-nitrogen ratio calculation: S1, omitting the nitrification tank (22), the secondary effluent of the sewage treatment plant first flows into a regulating tank, and the nitrification tank (22) is used as the regulating tank. When the denitrification tank (1) cycle operation is completed, the inlet water is transferred to the denitrification tank (1) through the nitrification liquid transfer pump (35); at regular intervals, the second sampling pump (32) collects water samples from the regulating tank and transports them to the nitrate nitrogen online detector (33) to measure nitrate nitrogen; the controller (5) calculates the amount of external carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio; activated sludge transfer, external carbon source and anaerobic treatment: S2, denitrification tank (1) at the end of each cycle, the activated sludge in the denitrification tank (1) is transferred to the empty anaerobic tank (2) in turn through the return sludge pump (9); at the same time, the controller (5) adds external carbon source to the anaerobic tank (2) in a quantitative manner according to the calculated amount of external carbon source through the external carbon source quantitative pump (10), and when the anaerobic tank (2) reaches the water level line set by the anaerobic water level controller (36), the return sludge pump (9) is turned off; thereafter, the corresponding submersible agitator (16) is started to start stirring and anaerobic treatment is carried out, and the anaerobic stirring reaction time is controlled at 1.5h-3h, the activated sludge releases phosphorus through anaerobism, absorbs the added organic carbon source, and synthesizes the internal carbon source to achieve anaerobic treatment; during the anaerobic treatment process, the controller (5) can also add the organic carbon source to the anaerobic tank (2) according to the nitrate nitrogen concentration subsequently measured in the regulating tank; the operation method of the anaerobic exhaust valve (37): S3, during anaerobic treatment, close the anaerobic exhaust valve (37) of the anaerobic tank (2) to maintain the anaerobic environment. When the anaerobic tank (2) transfers the activated sludge or adds the added carbon source, open the anaerobic exhaust valve (37), and the anaerobic tank (2) is always in an anaerobic state , one is idle and waiting; denitrification process: S4, after the denitrification tank (1) cycle is completed, the activated sludge is transferred to the anaerobic tank (2) in the idle waiting state, and the activated sludge that has been anaerobically treated in another anaerobic tank (2) is immediately added to the denitrification tank (1) through the sludge supply pump (8). At the same time, the nitrification liquid transfer pump (35) transfers the secondary effluent of the sewage treatment plant in the regulating tank to the denitrification tank (1) until it reaches the water level line set by the denitrification water level controller (21); then the denitrification tank (1) starts the corresponding submersible agitator (16) and starts the anoxic denitrification process until Denitrification endpoint; Denitrification endpoint control method: S5, the controller (5) continuously reads the monitoring data of the denitrification pH online detector (12), the ORP online detector (13) and the conductivity online detector (14) in the denitrification tank (1). When the pH rises during the falling process, the pH can be used as a reliable parameter for denitrification endpoint control, but the denitrification endpoint has not yet been reached. When the pH changes from rising to falling, it indicates that the denitrification reaction has reached the endpoint; at the same time, the lowest ORP control range is set to prevent the pH control method from failing. This ORP control range The ORP value corresponding to the denitrification endpoint is lower than the normal pH control. When the ORP is lower than this ORP control range and there is no turning point increase during the pH decrease, the denitrification process is stopped; the denitrification process is also judged by the conductivity changing from a rapid decrease to a slow decrease, a back-and-forth fluctuation or even an increase as an auxiliary basis for judging the denitrification endpoint; aerobic process: S6, after the denitrification reaches the endpoint, the controller (5) starts and controls the denitrification aeration pump (18) through the denitrification inverter (17). The aeration time is 5-10 minutes, and the aeration intensity is determined by the final DO concentration being greater than 1.5mg / L, less than 3mg / L to determine; static sedimentation and drainage and sludge discharge process: S7, aerobic aeration is completed, the denitrification aeration pump (18) and the corresponding submersible mixer (16) are turned off, the denitrification tank (1) begins to settle for 10-30 minutes, then the decanter electric valve (11) is opened, the electric telescopic rod of the decanter (4) is slowly lowered to drain, after the drainage is completed, the decanter electric valve (11) is closed, the electric telescopic rod of the decanter (4) returns to its original position, the denitrification sludge discharge pump (7) is turned on, the remaining sludge is discharged, and then the denitrification sludge is discharged through the sludge supply pump (8). The activated sludge in the nitrification tank (1) is transferred to the anaerobic tank (2) which is in an empty waiting state. The denitrification tank (1) ends its cycle operation, and the denitrification tank (1) is re-added with nitrification liquid and activated sludge to start a new cycle. The entire system repeats this cycle operation. The operation mode of the denitrification exhaust valve (6): S8, when the denitrification tank (1) is in the process of aeration, water intake, drainage and activated sludge transfer, the denitrification exhaust valve (6) is opened, and when the denitrification tank (1) is in the process of anoxic stirring and static sedimentation, the denitrification exhaust valve (6) is closed to minimize air entry and reduce the need for external carbon sources.

3. An intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method, characterized in that: The invention comprises an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system as described in claim 1, and the specific steps are as follows: when the ammonia nitrogen concentration of the secondary effluent of the sewage treatment plant is high or the total nitrogen purification requirement is high, the secondary effluent of the sewage treatment plant needs to enter the nitrification tank to perform aerobic nitrification treatment on the ammonia nitrogen in the secondary effluent. At this time, the water inlet can be selected to adopt two modes: intermittent water inlet and continuous water inlet. The specific operation steps are as follows; when continuous water inlet is adopted, the continuous water inlet mode, the end point of the intermittent nitrification reaction, the continuous aerobic nitrification and the nitrification liquid transfer: S1, the controller (5) continuously transports the secondary effluent of the sewage treatment plant to the upper part of the packing layer of the nitrification tank (22) through the water inlet pump (23); when the water level reaches the control water level set by the nitrification water level controller (34), the controller ( 5) The nitrification frequency converter (24) controls the nitrification aeration pump (25) to start aeration and start intermittent aerobic nitrification until the intermittent nitrification reaction reaches the end point of the nitrification reaction; thereafter, the controller (5) switches the aeration volume of the nitrification tank (22) to low aeration volume aeration, so that the DO concentration is greater than 2 mg / L and less than 3 mg / L, and realizes continuous nitrification conversion of the ammonia nitrogen in the subsequent continuous influent; when the nitrification tank (22) reaches the end point of intermittent nitrification, and when the cycle operation of the denitrification tank (1) is completed, the activated sludge in the denitrification tank (1) is transferred to the anaerobic tank (2), the controller (5) can transfer the nitrification liquid to the denitrification tank (1) through the nitrification liquid transfer pump (35). After the transfer is completed, the nitrification aeration pump (25) is turned off, and the nitrification tank (22) is nitrified. The pool (22) then continues to wait for the next water inflow to reach the set water level, and then restarts aeration, and the cycle repeats; when intermittent water inflow is adopted, the intermittent water inflow method, the intermittent nitrification reaction end point and the nitrification liquid transfer: S2: When the water inflow of the nitrification pool (22) reaches the water level line set by the nitrification water level controller (34), the water inflow can be stopped; then aeration is started, and when the nitrification reaction reaches the nitrification end point, aeration is stopped and the system is left to wait; after that, when the denitrification tank (1) cycle operation is completed, the controller (5) transfers the nitrification liquid to the denitrification tank (1) through the nitrification liquid transfer pump (35). After the transfer is completed, the nitrification pool (22) can be re-inflowed, and the cycle repeats; intermittent nitrification end point control method: S3, the controller (5) is set The nitrification pH online detector (29) and the nitrification DO online detector (30) in the nitrification tank (22) control the end point of the nitrification reaction, and the controller (5) controls the aeration volume so that the DO is less than 3 mg / L; the controller (5) uses the fact that the pH value stops decreasing and increases at the end of the nitrification reaction, accompanied by a sudden jump in the DO value of the nitrification DO online detector (30) as a method for controlling the end point of the nitrification reaction; nitrate nitrogen determination and external carbon source calculation: S4, the first sampling pump (31) and the second sampling pump (32) take samples from the water inlet pipe and the nitrification tank (22) at regular intervals, and the nitrate nitrogen concentration is determined by the nitrate nitrogen online detector (33); the controller (5) calculates the amount of external carbon source required for denitrification in this cycle based on the set carbon-nitrogen ratio;Activated sludge transfer, external carbon source and anaerobic treatment: At the end of each cycle of S5, denitrification tank (1), the activated sludge in the denitrification tank (1) is transferred to the empty anaerobic tank (2) in turn through the return sludge pump (9); at the same time, the controller (5) adds the external carbon source to the anaerobic tank (2) in a quantitative manner through the external carbon source quantitative pump (10) according to the calculated amount of the external carbon source. When the anaerobic tank (2) reaches the water level set by the anaerobic water level controller (36), the return sludge pump (9) is turned off; thereafter, the corresponding submersible agitator (16) is started to stir and perform anaerobic treatment. The anaerobic stirring reaction time is controlled to be 1.5h-3h. The activated sludge releases phosphorus through anaerobism, absorbs the external organic carbon source, and synthesizes the internal carbon source to achieve anaerobic treatment; in During the anaerobic treatment process, the controller (5) can also add organic carbon source to the anaerobic tank (2) according to the nitrate nitrogen concentration measured after the nitrification reaction in the nitrification tank (22); the operation method of the anaerobic exhaust valve (37): S6, during the anaerobic treatment, close the anaerobic exhaust valve (37) of the anaerobic tank (2) to maintain the anaerobic environment. When the anaerobic tank (2) transfers the activated sludge or adds an external carbon source, open the anaerobic exhaust valve (37). The anaerobic tank (2) is always in an anaerobic state and the other is idle and waiting; denitrification process: S7, after the denitrification tank (1) cycle is completed, the activated sludge is transferred to the anaerobic tank (2) that is idle and waiting, and the activated sludge that has been anaerobically treated in the other anaerobic tank (2) is immediately added to the denitrification tank (1) through the sludge supply pump (8). Denitrification tank (1), while the nitrification liquid transfer pump (35) transfers the nitrification liquid to the denitrification tank (1) until it reaches the water level line set by the denitrification water level controller (21); then the denitrification tank (1) turns on the corresponding submersible agitator (16) to start the anoxic denitrification process until the denitrification end point; denitrification end point control method: S8, the controller (5) continuously reads the monitoring data of the denitrification pH online detector (12), the ORP online detector (13) and the conductivity online detector (14) in the denitrification tank (1). When the pH rises during the falling process, the pH can be used as a reliable parameter for denitrification end point control, but the denitrification end point has not yet been reached. When the pH changes from rising to falling, it indicates that the denitrification reaction has begun. Reach the end point; at the same time, set the lowest ORP control range to prevent the pH control method from failing. This ORP control range is lower than the ORP value corresponding to the denitrification end point when the pH is normally controlled. When the ORP is lower than this ORP control range and there is no turning point increase during the pH drop, the denitrification process is stopped; the denitrification process is also based on the conductivity changing from a rapid drop to a slow drop, back and forth fluctuations or even an increase as an auxiliary judgment basis for the denitrification end point; aerobic process: S9, after the denitrification reaches the end point, the controller (5) starts and controls the denitrification aeration pump (18) through the denitrification inverter (17). The aeration time is 5-10 minutes, and the aeration intensity is determined by the final DO concentration being greater than 1.5 mg / L and less than 3 mg / L.Static sedimentation and drainage and sludge discharge process: S10, aerobic aeration is completed, the denitrification aeration pump (18) and the corresponding submersible agitator (16) are turned off, and the denitrification tank (1) begins to settle for 10-30 minutes, then the decanter electric valve (11) is opened, and the electric telescopic rod of the decanter (4) is slowly lowered to drain. After the drainage is completed, the decanter electric valve (11) is closed, and the electric telescopic rod of the decanter (4) returns to its original position, and the denitrification sludge discharge pump (7) is turned on to discharge the remaining sludge. Then, the sludge in the denitrification tank (1) is discharged through the sludge supply pump (8). The activated sludge is transferred to the anaerobic tank (2) which is in an empty waiting state. The denitrification tank (1) ends its cycle operation. The denitrification tank (1) is refilled with nitrification liquid and activated sludge to start a new cycle. The entire system repeats the cycle operation. The operation mode of the denitrification exhaust valve (6): S11, when the denitrification tank (1) is in the process of aeration, water intake, drainage and activated sludge transfer, the denitrification exhaust valve (6) is opened. When the denitrification tank (1) is in the process of anoxic stirring and static sedimentation, the denitrification exhaust valve (6) is closed to minimize air entry and reduce the need for external carbon sources.

4. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method according to claim 3 is characterized in that: The secondary effluent from the sewage treatment plant is replaced by surface water from rivers and lakes or agricultural wastewater that is severely eutrophicated.

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