Intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system and method thereof

Abstract

The invention relates to an intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system and a method thereof, and belongs to the technical field of sewage purification, the intelligent intermittent double-sludge denitrification nitrogen and phosphorus deep purification system comprises a nitrification tank, a denitrification tank, two anaerobic tanks, an external carbon source storage tank, a water decanter and a controller, based on the principle of a double-sludge denitrification technology, a nitrification process and a denitrification process are separately carried out in two reactors, low activated sludge concentration is adopted, an intelligent on-line control technology is applied, and through the steps of nitrification, activated sludge accurate external carbon source anaerobic treatment, anoxic denitrification, aerobic stripping and the like, the denitrification process is completed. By accurately controlling the nitrification and denitrification end points on line, the quality of purified water finally reaches the surface water quality standard III or above, the problem of eutrophication pollution of a receiving water body caused by direct discharge of secondary effluent of an existing sewage treatment plant is thoroughly solved, the standard improvement and reconstruction of the existing sewage treatment plant are realized, and the water body protection of a water source area is realized. The water quality restoration of the eutrophic water body has important significance.

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 a method thereof. Background Art

[0002] Although the current sewage treatment rates in cities and counties in my country have reached 97.53% and 95.05% respectively, due to the limitations of sewage treatment technology and treatment costs, the current sewage treatment plant discharge standards implemented in my country, even the most stringent standards: the "Emission Limits of Major Water Pollutants from Urban Sewage Treatment Plants" (DB5301 / T43-2020) issued by Kunming City, set the emission limits for total nitrogen at 5 (10) mg / L and total phosphorus at 0.05 mg / L for environmentally sensitive areas. The total nitrogen concentration is still far higher than the surface water quality standard, and also far higher than the internationally recognized critical concentrations for eutrophication of water bodies: TN is 0.2 mg / L and TP is 0.02 mg / L. In addition, the main form of nitrogen in secondary effluent is nitrate nitrogen, which can also form nitrite compounds in the human body, increasing the risk of cancer. It can be seen that the eutrophication pollution and water quality health problems caused by the secondary effluent of my country's sewage plants to the receiving water bodies are a long-term and severe challenge.

[0003] In recent years, with the implementation of the upgrading and transformation of sewage treatment plants, some sewage treatment plants in my country have carried out tertiary treatment (deep treatment). However, the deep treatment processes of sewage treatment plants in my country usually adopt: adsorption, coagulation sedimentation, ion exchange, membrane separation and biological deep purification technology, etc. These technologies and methods have defects such as high cost, unsatisfactory purification effect, and difficulty in removing nitrogen and phosphorus at the same time. Although denitrification filters have been widely used, they lack carbon sources, have poor purification efficiency under low temperature conditions in winter, and have unsatisfactory phosphorus removal efficiency, generally only 20-30%. Although artificial wetlands are simple to manage and have low processing and operation costs, they have a long residence time, occupy a large area, and have unsatisfactory purification effects, especially in winter.

[0004] 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 the current eutrophication problem of water bodies in my country. Summary of the invention

[0005] 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 a sewage plant.

[0006] 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, a plurality of submersible agitators and a controller; The top of the denitrification tank is provided with a denitrification exhaust hole, the bottom of the denitrification tank is provided with a nitrification liquid inlet hole, a denitrification mud discharge hole, a mud inlet hole and a mud outlet 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. The bottom ends of the two anaerobic tanks are provided with mud inlet and outlet holes and the top ends are provided with an external carbon source hole. The two mud inlet and outlet holes are respectively connected with the mud inlet hole and the mud outlet hole through a mud supply pipe and a mud return pipe. Mud supply pumps are installed on the two mud supply pipes, and mud return pumps are installed on the two mud return pipes. Exhaust pipes are installed on the top ends of the two anaerobic tanks, and anaerobic water level controllers and anaerobic exhaust valves are installed on the two exhaust pipes. 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 external carbon source quantitative pumps; 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 an electric valve of the decanter is installed on the pipe wall passing through the perforation. A plurality of submersible agitators are respectively installed in the denitrification tank and the two anaerobic tanks; 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 agitators.

[0007] The beneficial effects of the present invention are: 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 set in the denitrification tank and anaerobic tank can be closed during anaerobic stirring and anoxic stirring, reducing the entry of air and oxygen and reducing the consumption of external carbon sources.

[0008] 2. Two anaerobic tanks are used, and the two anaerobic tanks are connected to the denitrification tank respectively. When one anaerobic tank is carrying out anaerobic treatment of activated sludge, the other is in an idle waiting state, so that 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 can be 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.

[0009] Based on the above technical solution, the present invention can also be improved as follows.

[0010] 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.

[0011] The above further beneficial effect is: the controller uses the detection values ​​of the denitrification pH online detector, the ORP online detector, the conductivity online detector and the denitrification DO online detector to track the denitrification process inside the denitrification tank in real time, accurately identify the end point of the denitrification reaction, 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.

[0012] Furthermore, it also includes a denitrification frequency converter, a denitrification aeration pump, a denitrification gas flow sensor, a plurality of denitrification aeration heads and a denitrification water level controller; the plurality of denitrification aeration heads are fixed at intervals in the inner lower part of the denitrification tank; the air outlet of the denitrification aeration pump passes through the denitrification tank and is connected with the plurality of denitrification aeration heads; the denitrification gas flow sensor is installed on the connecting pipe between the denitrification aeration pump and the plurality of denitrification aeration heads; the denitrification frequency converter is electrically connected to the denitrification aeration pump; the denitrification water level controller is installed in the inner upper part of the denitrification tank; the controller is electrically connected to the denitrification frequency converter, the denitrification gas flow sensor and the denitrification water level controller respectively.

[0013] 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 is convenient for 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.

[0014] 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 the water outlet thereof 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 provided 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; a sieve plate is installed at the lower end of the interior of the nitrification tank 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; 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 through 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.

[0015] The above further beneficial effect is: 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 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 the deep removal of nitrogen can be achieved through subsequent denitrification.

[0016] 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.

[0017] The further beneficial effect of adopting the above method is: 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.

[0018] 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 respectively connected to the water outlet of the first sampling pump and the water outlet of the second sampling pump; the controller is electrically connected to the nitrate nitrogen online detector, the first sampling pump and the second sampling pump.

[0019] The further beneficial effect of adopting the above method is: first use the first sampling pump to extract the secondary effluent sample of the sewage treatment plant, and then use the second sampling pump to extract the water sample inside the nitrification tank, the nitrate nitrogen online detector determines the nitrate nitrogen concentration, and calculates the amount of external carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio.

[0020] 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.

[0021] The above further beneficial effect is: 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 when the denitrification tank cycle ends, the secondary effluent of the sewage treatment plant is transferred to the denitrification tank; 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.

[0022] 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, and the sludge retention time is 8 to 30 days.

[0023] The above further beneficial effect is: the smaller anaerobic tank volume makes the activated sludge in the denitrification tank at a lower concentration, so that the amount of added carbon source, the phosphorus content released by anaerobes and the nitrogen and phosphorus content of the secondary effluent of the sewage treatment plant match each other, promote the growth of denitrifying phosphorus removal organisms, and enable nitrogen and phosphorus to be removed and absorbed by the denitrification process of microorganisms at the same time, and the phosphorus removal capacity will not be reduced due to insufficient nitrate nitrogen concentration, and even a large amount of phosphorus will not flow out.

[0024] In addition, an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method is provided, 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 a nitrification tank is not required, but a regulating tank is used. The specific operation steps are as follows: Influent mode, 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 is completed, the influent stored in the regulating tank is transported to the denitrification tank through the nitrification liquid transfer pump; at regular intervals, the second sampling pump collects water samples from the regulating tank and transports them to the nitrate nitrogen online detector for nitrate nitrogen determination; the controller calculates the amount of additional carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio (or if the total nitrogen concentration of the influent is known, the amount of additional carbon source required to be added to the anaerobic tank is calculated according to the total nitrogen concentration of the influent); Activated sludge transfer, external carbon source and anaerobic treatment: S2. At the end of each cycle of the denitrification tank, 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 quantitative 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; then, the corresponding submersible agitator is started to stir and anaerobic treatment is carried out. The anaerobic stirring reaction time is controlled at 1.5-3h. The activated sludge releases phosphorus through anaerobism, absorbs the external 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; 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 transfers activated sludge or adds an external carbon source, open the anaerobic exhaust valve; Denitrification process: S4, after the denitrification tank cycle is over, the activated sludge is transferred to the anaerobic tank in the idle 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 secondary effluent of the sewage 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; 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 decline, 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 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 is lower than the ORP value corresponding to the pH normal control of the denitrification endpoint. When the ORP is lower than this ORP control range and there is no turning point rise during the pH decline, the denitrification process is stopped; At the same time, the conductivity changes from a rapid decline to a slow decline, fluctuates back and forth or even rises as an auxiliary basis for judging the denitrification endpoint during the denitrification process; 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; 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, and the nitrification 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 idle waiting state through the sludge supply pump. The cycle operation of the denitrification tank is completed, and the denitrification tank is re-added with nitrification liquid and activated sludge to start a new cycle. The whole system repeats the cycle operation in this way; Operation method of denitrification exhaust valve: S8. Open the denitrification exhaust valve when the denitrification tank is in aeration, water intake, drainage and activated sludge transfer. Close the denitrification exhaust valve when the denitrification tank is in anoxic stirring and static sedimentation to minimize air entry and reduce the need for external carbon sources.

[0025] In addition, an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method is provided, and the specific steps are as follows: 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 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: When continuous water inflow is adopted, continuous water inflow mode, intermittent nitrification reaction end point, continuous aerobic nitrification and nitrification liquid transfer: 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 inflow 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, and starts intermittent aerobic nitrification until the intermittent nitrification reaction reaches the nitrification reaction end point; after that, 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, and realizes continuous nitrification conversion of ammonia nitrogen in the subsequent continuous water inflow; when the nitrification tank reaches the intermittent nitrification end point, and when the denitrification tank cycle operation is completed, 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, and 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, and then restarts aeration, and the cycle is repeated; When intermittent water inflow is adopted, the intermittent water inflow mode, intermittent nitrification reaction end point and nitrification liquid transfer are as follows: S2: When the water inflow of the nitrification pool reaches the water level line set by the nitrification water level controller, 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 stand and wait; after that, when the denitrification tank cycle operation is completed, the controller transfers the nitrification liquid to the denitrification tank through the nitrification liquid transfer pump. After the transfer is completed, the nitrification pool can be refilled with water, and the cycle is repeated; 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 set in the nitrification tank. The controller controls the aeration volume so that the DO is 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; Nitrate nitrogen determination and calculation of added carbon source: S4, the first sampling pump and the second sampling pump take samples from the water inlet pipe and the nitrification tank at regular intervals, and the nitrate nitrogen concentration is determined by the nitrate nitrogen online detector; the controller calculates the amount of added carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio (or if the total nitrogen concentration of the inlet water is known, the amount of added carbon source required to be added to the anaerobic tank is calculated according to the total nitrogen concentration of the inlet water); Activated sludge transfer, external carbon source and anaerobic treatment: S5. At the end of each cycle of the denitrification tank, 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 quantitative 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; then, the corresponding submersible agitator is started to stir 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 external 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. 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 an external carbon source, open the anaerobic exhaust valve. One anaerobic tank is always in an anaerobic state, and the other is idle waiting; Denitrification process: S7, after the denitrification tank cycle is over, the activated sludge is transferred to the anaerobic tank in the idle 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; 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 decline, 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 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 is lower than the ORP value corresponding to the pH normal control of the denitrification endpoint. When the ORP is lower than this ORP control range and there is no turning point rise during the pH decline, the denitrification process is stopped; the denitrification process also uses the conductivity change from rapid decline to slow decline, back and forth fluctuation or even rise as an auxiliary basis for judging the denitrification endpoint; 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; 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. 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 nitrification 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 idle waiting through the sludge supply pump. The cycle operation of the denitrification tank is completed, and the denitrification tank is re-added with nitrification liquid and activated sludge after anaerobic treatment to start a new cycle. The whole system operates in this way repeatedly.

[0026] Operation method of denitrification exhaust valve: S11. Open the denitrification exhaust valve when the denitrification tank is in aeration, water intake, drainage and activated sludge transfer. Close the denitrification exhaust valve when the denitrification tank is in anoxic stirring and static sedimentation to minimize air entry and reduce the need for external carbon sources.

[0027] 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 of a sewage treatment plant relative to domestic sewage. The system is based on the principle of double-sludge denitrification technology, separates the nitrification process and the denitrification process in two reactors, adopts a lower activated sludge concentration, and uses intelligent online control technology. Through nitrification, anaerobic treatment of activated sludge with precise external carbon source, anoxic denitrification, aerobic stripping and other steps, and through precise online control of 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, and is of great significance to the upgrading and transformation of existing sewage treatment plants, the protection of water bodies in water sources, the eutrophication protection of oligotrophic and mesotrophic lakes, and the water quality restoration of eutrophic water bodies.

[0028] Principle of use: The organic matter content of the secondary effluent of the sewage treatment plant is low, and the nitrogen mainly exists in the form of nitrate nitrogen and a small amount of ammonia nitrogen, and the phosphorus is mainly orthophosphate. Based on the principle that double sludge denitrification can remove nitrogen and phosphorus at the same time, the secondary effluent of the sewage treatment plant first enters the nitrification tank, and through aerobic aeration nitrification reaction, the end point of the nitrification reaction is controlled, and all the residual ammonia nitrogen is oxidized to nitrate nitrogen. The nitrate nitrogen concentration is measured or the required external carbon source is calculated according to the total nitrogen concentration of the influent. Accurately add the external carbon source to the anaerobic tank and mix it with the activated sludge for anaerobically mixing. The microorganisms release phosphorus and absorb the external carbon source, and convert it into the internal carbon source of the microorganisms. After the denitrification tank has finished its last cycle, the activated sludge is transferred to the anaerobic tank in the empty waiting state. The activated sludge from another anaerobic tank that has been anaerobically treated can be transferred to the denitrification tank for anoxic mixing with the secondary effluent after nitrification treatment, and anoxic denitrification reaction occurs. By controlling the end point of the denitrification reaction, the complete denitrification removal of nitrate nitrogen and nitrite nitrogen is achieved, and at the same time, denitrification absorption of phosphorus is achieved; after the denitrification is completed, aerobic aeration is performed to further absorb phosphorus through aerobic action, and the nitrogen produced by denitrification is blown off to facilitate the sedimentation of the activated sludge. After that, it is allowed to settle and drained through a decanter. After the drainage is completed, the remaining sludge is discharged, and the activated sludge in the denitrification tank is transferred to the anaerobic tank in the empty waiting state. The two anaerobic tanks take turns to perform anaerobically treatment on the activated sludge. In this way, a nitrification tank, two anaerobic tanks and a denitrification tank can be operated in a cycle over and over again.

[0029] Furthermore, in addition to being applicable to secondary effluent from sewage treatment plants, the patent is also applicable to surface water in rivers and lakes and agricultural wastewater with severe eutrophication pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of an intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system and method of the present invention.

[0031] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 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 frequency converter, 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 valve. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below in conjunction with 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.

[0033] Principles and features of main components: Nitrification tank 22: (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 22 to aerobic nitrification treatment of the ammonia nitrogen in the secondary effluent) The nitrification tank 22 is a cylinder, and a sieve plate 27 is arranged above the bottom. A gas pipeline and a plurality of nitrification aeration heads 28 are installed above the sieve plate 27, and a filler is installed. The filler is volcanic rock, ceramsite, activated carbon particles, zeolite and quartz sand, and the particle size is 0.5-2.5cm. The secondary effluent of the sewage treatment plant is connected to the nitrification tank 22 through the water inlet pipe and the water inlet pump 23, and the bottom drain of the nitrification tank 22 is connected to the denitrification tank 1 through a pipe and a nitrification liquid transfer pump 35. A mud discharge pipe and a nitrification mud discharge valve 38 are arranged at the bottom of the nitrification tank. Multiple nitrification aeration heads 28 are connected to the nitrification gas flow sensor 26 and the gas outlet of the nitrification aeration pump 25 in sequence through a gas pipeline. A nitrification water level controller 34 is provided above the nitrification tank 22, and a nitrification pH online detector 29 and a nitrification DO online detector 30 are provided below the water level line. The nitrification frequency converter 24 is electrically connected to the nitrification aeration pump 25, and the controller 5 is electrically connected to the nitrification frequency converter 24, the nitrification liquid transfer pump 35, the nitrification sludge valve 38, the nitrification gas flow sensor 26, the nitrification water level controller 34, the nitrification pH online detector 29 and the nitrification DO online detector 30. The controller 5 controls the opening and working frequency of the nitrification aeration pump 25 through the nitrification frequency converter 24, reads the gas flow data of the nitrification gas flow sensor 26 and the DO concentration measured by the nitrification DO online detector 30, controls the aeration intensity of the nitrification tank 22, and further controls the DO concentration. The nitrification tank 22 regularly adjusts the nitrification aeration pump 25 to high-intensity aeration through the nitrification frequency converter 24, and then completely empties it to discharge the detached and settled biofilm and activated sludge to avoid plugging of the filler.

[0034] Adjustment tank: When the secondary effluent ammonia nitrogen concentration of the sewage treatment plant is low, or the total nitrogen requirement for the effluent is not high, the nitrification tank 22 is not needed. The nitrification tank 22 can be replaced with an adjustment tank without fillers, aeration pumps, aeration heads, first sampling pumps 31, online pH detectors and online DO detectors. The adjustment tank retains the nitrification water level controller 34, nitrification liquid transfer pump 35 and corresponding pipelines, and is equipped with an online nitrate nitrogen online detector 33 and a second sampling pump 32. The adjustment tank temporarily stores continuous or intermittent influent water. When the denitrification tank 1 cycle is completed, the secondary effluent of the sewage treatment plant stored in the adjustment tank only needs to be transferred to the denitrification tank 1 through the nitrification liquid transfer pump 35.

[0035] Nitrate nitrogen determination: When the nitrification tank 22 is used, 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 inside of the nitrification tank 22, and 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 respectively; when the regulating tank is used, the water inlet of the second sampling pump 32 is connected to the inside of the regulating tank, and the water outlet of the second water inlet pump 32 is connected to the water inlet of the nitrate nitrogen online detector 33. The controller 5 is electrically connected to the first sampling pump 31, the second sampling pump 32 and the nitrate nitrogen online detector 33.

[0036] External carbon source storage tank 3: An external carbon source outlet hole is provided at the bottom of the external carbon source storage tank 3 and the external carbon source outlet hole is connected to two external carbon source holes respectively through two carbon supply pipes, and an external carbon source metering pump 10 is installed on the two carbon supply pipes; the controller 5 is electrically connected to the two external carbon source metering pumps 10.

[0037] Anaerobic tank 2: There are two anaerobic tanks 2, each with a mud inlet and outlet hole at the bottom and an external carbon source hole at the top. The two mud inlet and outlet holes are connected to the mud inlet and mud outlet holes of the denitrification tank 1 through a mud supply pipe and a mud return pipe, respectively. Mud supply pumps 8 are installed on the two mud supply pipes, and mud return pumps 9 are installed on the two mud return pipes. Exhaust pipes are installed at both ends of the two anaerobic tanks, and anaerobic water level controllers 36 and anaerobic exhaust valves 37 are installed on the two exhaust pipes. Submersible agitators 16 are installed in the two anaerobic tanks 2 for mixing and stirring during anaerobic treatment. The controller 5 is electrically connected to the mud supply pump 8, the mud return pump 9, the anaerobic water level controller 36, the submersible agitator 16 and the anaerobic exhaust valve 37.

[0038] Denitrification tank: The denitrification tank 1 is connected to the anaerobic tank 2 through the return mud pump 9 and the pipeline. The anaerobic tank 2 is connected to the denitrification tank 1 through the mud supply pump 8 and the pipeline. The denitrification tank 1 is used to discharge the purified water of the system through the decanter 4, the corresponding pipeline, and the decanter electric valve 11 on the pipeline; the bottom of the denitrification tank 1 discharges the remaining activated sludge to the outside through the denitrification mud pump 7 and the corresponding pipeline; the bottom of the denitrification tank 1 is conical, and the top is a cylinder. The denitrification water level controller 21 and the 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 the 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 a plurality of denitrification aeration heads 20 are provided above the cone, and the plurality of denitrification aeration heads 20 are connected with 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 agitator 16; 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 arranged below the water level line; 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 end point of the denitrification reaction through an internal program, controls the start and working 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 then controls the DO concentration or controls the ORP range.

[0039] Process operation and operation method: 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 aerobic nitrification treatment of the ammonia nitrogen in the secondary effluent. When the inlet water is continuously inlet, the specific operation 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 volume is preferably DO 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, and 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 the subsequent ammonia nitrogen in the influent is aerobic nitrified until the nitrification liquid is transferred from the nitrification tank 22 to the denitrification tank 1, and then the nitrification aeration pump 25 is closed, and the nitrification tank 22 starts a new cycle. When water is fed in intermittently, the specific operation steps of the nitrification tank 22 are as follows: the nitrification tank 22 only needs to stop feeding water and start aeration when the water reaches the water level set by the nitrification water level controller 34. The controller continuously monitors the changes in pH and DO values. When the pH value increases, the DO value suddenly jumps, indicating 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.

[0040] 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 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 denitrification tank 1 cycle is completed, 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 and mixed with the activated sludge treated anaerobically to carry out a denitrification reaction.

[0041] Nitrate nitrogen determination and calculation of added carbon source: When the nitrification tank 22 is used, 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 online detector 33 determines the nitrate nitrogen concentration, and calculates the amount of added carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio; when the regulating tank is used, the nitrate nitrogen online detector 33 determines the nitrate nitrogen concentration of the secondary effluent of the sewage treatment plant in the regulating tank through the second water inlet pump 32, and calculates the amount of added carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio. If the total nitrogen concentration of the inlet water is known, the nitrate nitrogen online detector 33, the first sampling pump 31, the second sampling pump 32 and the corresponding pipelines can be omitted.

[0042] Operation mode of external carbon source storage tank 3 and anaerobic tank 2: At the end of each cycle of denitrification tank 1, the activated sludge of denitrification tank 1 is transferred to the empty (no activated sludge) anaerobic tank 2 in turn through the return mud pump 9. At the same time, the controller 5 quantitatively adds the external carbon source of the external carbon source storage tank 3 to the anaerobic tank 2 through the external carbon source quantitative pump 10 according to the calculated amount of external carbon source. When the anaerobic tank 2 reaches the water level set by the anaerobic water level controller 36, the return mud pump 9 is turned off, and then the corresponding submersible agitator 16 is started to start stirring for anaerobic treatment. The anaerobic stirring reaction time is controlled at 1.5h-3h. The activated sludge releases phosphorus through anaerobes, absorbs the added organic carbon source, and synthesizes the internal carbon source to achieve anaerobic treatment. During anaerobic treatment, the anaerobic exhaust valve 37 of the anaerobic tank 2 is closed to maintain the anaerobic environment. When the anaerobic tank 2 transfers the activated sludge or adds the external carbon source, the anaerobic exhaust valve 37 is opened. Anaerobic tank 2 always has one in anaerobic state and the other in idle waiting state.

[0043] Operation mode of denitrification tank 1: after denitrification tank 1 is drained and sludged, activated sludge is transferred to vacant anaerobic tank 2, and external carbon source metering pump 10 quantitatively adds external carbon source to anaerobic tank 2, anaerobic tank 2 enters anaerobic operation, denitrification tank 1 starts a new operation cycle, nitrification liquid transfer pump 35 transfers nitrification supernatant or secondary effluent of sewage treatment plant in regulating tank to denitrification tank 1, and activated sludge of anaerobic tank 2 that has been anaerobically treated in advance is returned to denitrification tank 1 through sludge supply pump 8, and then denitrification tank 1 starts corresponding submersible agitator 16 to start anoxic denitrification process, at this time, controller 5 continuously reads monitoring data of denitrification tank 1 in denitrification pH online detector 12, ORP online detector 13 and conductivity online detector 14, when pH rises during the falling process, the mark close to pH can be used as the denitrification end point judgment parameter, when pH changes from rising to falling, it marks that the denitrification reaction has reached the end point. At this time, it is usually the case that the conductivity decreases slowly, fluctuates, stagnates or even increases. 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, which is lower than the ORP value corresponding to the pH normal control of the denitrification endpoint to avoid the continuous decline of pH, the situation where pH never rises or rises and then falls, and at the same time, the conductivity decreases slowly, fluctuates, stagnates or even increases as an auxiliary basis for judgment to avoid delaying the denitrification endpoint, resulting in the conversion of anoxic environment into anaerobic environment and the release of phosphorus, which affects the purification of phosphorus. When denitrification reaches the end point, the denitrification frequency converter 17 is immediately used to start and control the denitrification aeration pump 18. The aeration time can be controlled within 5-10 minutes. The aeration intensity is preferably such that the final DO concentration is greater than 1.5 mg / L and less than 3 mg / L. Aerobic aeration is used to strengthen the further absorption and removal of phosphorus, and the nitrogen produced by denitrification is blown off to facilitate the sedimentation and separation of the activated sludge. After the aerobic aeration is completed, the denitrification frequency converter 17 is used to turn off the denitrification aeration pump 18, the submersible agitator 16 is turned off, and static sedimentation begins for 10-30 minutes. After that, the electric valve 11 of the decanter is opened, and the electric support rod of the decanter 4 is slowly lowered to drain. After the drainage is completed, the electric valve 11 of the decanter is closed, and the electric support rod of the decanter 4 is lifted back to its original position. The denitrification sludge pump 7 is turned on to discharge the remaining activated sludge. At the same time, the return sludge pump 9 is turned on to transfer part or all of the activated sludge to the anaerobic tank 2 that is waiting in the empty state. Denitrification tank 1 starts a new cycle and runs over and over again.

[0044] The controller 5 controls the drainage water level and the inlet water level of the denitrification tank 1 by controlling the lifting height of the decanter 4 of the denitrification tank 1 when draining water. At the same time, by controlling the effective volume of the anaerobic tank 2 to be 1 / 40 to 1 / 5 of the effective volume of the denitrification tank 1 and the sludge retention time to be 8 to 30 days, the activated sludge of the denitrification tank is at a lower concentration, so that the amount of added carbon source, the phosphorus content released by anaerobes and the nitrogen and phosphorus content of the secondary effluent of the sewage treatment plant are matched, and the growth of denitrifying phosphorus removal organisms is promoted, so that nitrogen and phosphorus can be removed and absorbed by the denitrification process of microorganisms at the same time, and the phosphorus removal power will not be reduced due to insufficient nitrate nitrogen concentration, and even a large amount of phosphorus will flow out. When the total nitrogen concentration of the influent is lower, the required effective volume of the anaerobic tank 2 is smaller than the effective volume of the denitrification tank 1. When the phosphorus content of the influent is high and the phosphorus purification efficiency is poor, the phosphorus removal efficiency can be improved by reducing the sludge retention time.

[0045] 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.

[0046] In order to better achieve the simultaneous removal of nitrogen and phosphorus, the cycle operation time of the denitrification stage of the denitrification tank is controlled to be 20-60 minutes. The controller 5 adjusts the denitrification operation time by adjusting the carbon-nitrogen ratio. A shorter denitrification time may lead to a decrease in the removal efficiency of phosphorus, and a longer denitrification time may achieve the simultaneous deep removal of nitrogen and phosphorus, but it will reduce the operation efficiency of the denitrification tank 1 and the entire system.

[0047] The added carbon sources were methanol, sodium acetate, acetic acid and alcohol.

[0048] Example 1: When the CODcr concentration of the secondary effluent of the 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, the effective volume of the anaerobic tank is 1.5 / 20 of the effective volume of the denitrification tank, the secondary effluent of the sewage treatment plant first enters the nitrification tank 22 for nitrification, converts all the ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and then enters the denitrification tank for denitrification, denitrification and phosphorus removal, aerobic and sedimentation processes, the carbon-nitrogen ratio of the added carbon source is 5.6, 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, achieving deep purification of nitrogen and phosphorus, and the effluent total nitrogen and total phosphorus indicators meet the surface water quality lake reservoir Class III or above standards. The denitrification tank inlet volume 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, standing and settling for 10 minutes, drainage for 30 minutes, aeration time for 10 minutes, the final DO concentration of aeration is 2.2mg / L, the sludge retention time is 15 days, the operating time of each cycle is 120 minutes, and 12 cycles are operated per day.

[0049] Example 2: When the inlet CODcr concentration of the secondary effluent of the 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, 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 the ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and then enters the denitrification tank for denitrification, denitrification and phosphorus removal, aerobic and sedimentation processes, the carbon-nitrogen ratio of the added carbon source is 6.2, 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, achieving deep purification of nitrogen and phosphorus, and the effluent total nitrogen and total phosphorus indicators meet the surface water quality lake reservoir Class III or above standards. The inlet 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 it runs more than 12 cycles a day.

[0050] Example 3: When the inlet CODcr concentration of the secondary effluent of the 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 of the sewage treatment plant first enters the nitrification tank 22 for nitrification to convert all the ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and then enters the denitrification tank for denitrification, denitrification and phosphorus removal, aerobic and sedimentation processes. The effective volume of the anaerobic tank is 2 / 20 of the denitrification tank, the carbon-nitrogen ratio is 5.2, the added carbon source is sodium acetate, 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, and the effluent total nitrogen and total phosphorus indicators meet the surface water quality lake reservoir Class III or above standards. 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 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 a day.

[0051] 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 treatment time, high reactor operation efficiency, no by-products, and can simultaneously achieve deep removal of nitrogen and phosphorus, making it more suitable for water body restoration, deep reuse of sewage and recycling of water resources.

[0052]

[0053] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope 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 the 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), each having a mud inlet and outlet hole at its bottom and an external carbon source hole at its top, the two mud inlet and outlet holes being connected to the mud inlet hole and the mud outlet hole through a mud supply pipe and a mud return pipe respectively, the two mud supply pipes being equipped with a mud supply pump (8), and the two mud return pipes being equipped with a mud return pump (9); the two anaerobic tanks (2) being equipped with an exhaust pipe at their top and an anaerobic water level controller (36) and an anaerobic exhaust valve (37) being equipped on the two exhaust pipes; An external carbon source storage tank (3), wherein the bottom end of the external carbon source storage tank (3) 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 respectively through two carbon supply pipes, and the two carbon supply pipes are both equipped with an external carbon source metering pump (10); A decanter (4), the decanter (4) being fixed on the electric telescopic rod in the denitrification tank (1) in an inclined manner from top to bottom, and having its water inlet placed in the denitrification tank (1), the water outlet of the decanter (4) passing through the perforation, and having a decanter electric valve (11) installed on the pipe wall passing through the perforation; A plurality of submersible agitators (16), wherein the plurality of submersible agitators (16) are respectively installed in the denitrification tank (1) and the two anaerobic tanks (2); A controller (5), wherein 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).

2. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system according to claim 1 is characterized in that: It also 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 in the denitrification tank (1) at intervals and are all electrically connected to the controller (5).

3. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system according to claim 1 is characterized in that: The invention also 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 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); and 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.

4. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system according to claim 1 is characterized in that: The nitrification tank (22) 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 provided with a nitrification mud discharge valve (38), and the nitrification liquid discharge hole is connected to the nitrification liquid inlet hole through a nitrification liquid transfer pump (35); a sieve plate (27) is installed at the lower end of the interior of the nitrification tank (22), and the nitrification tank (22) corresponds to the upper side of the sieve plate (27). A plurality of nitrification aeration heads (28) are fixed and a plurality of fillers are placed; the nitrification frequency converter (24) is electrically connected to the nitrification aeration pump (25); the gas outlet of the nitrification aeration pump (25) passes through the nitrification tank (22) through a gas pipeline and is connected to 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); and 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.

5. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system according to claim 4 is characterized in that: It also 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 pool (22); and the controller (5) is electrically connected to the nitrification pH online detector (29) and the nitrification DO online detector (30), respectively.

6. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system according to claim 4 is characterized in that: It also includes 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 inside 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) respectively; 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).

7. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system according to claim 1 is characterized in that: 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 this ratio is. The sludge retention time is 8 to 30 days.

8. An intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method, characterized in that: The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system comprises the following specific steps: When the ammonia nitrogen concentration in 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 (1) is not required. The specific operation steps are as follows: Influent method, nitrate nitrogen determination and carbon-nitrogen ratio calculation: S1. The nitrification tank (22) is omitted, and the secondary effluent of the sewage treatment plant first flows into a regulating tank. When the denitrification tank (1) cycle operation is completed, the influent 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) for nitrate nitrogen determination; the controller (5) calculates the amount of external carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio (or if the total nitrogen concentration of the influent is known, the amount of external carbon source required to be added to the anaerobic tank (2) is calculated according to the total nitrogen concentration of the influent); Activated sludge transfer, external carbon source addition and anaerobic treatment: S2, at the end of each cycle of the denitrification tank (1), the activated sludge in the denitrification tank (1) is transferred in turn to the empty (no activated sludge) anaerobic tank (2) 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, and 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 start stirring and anaerobic treatment is performed. 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; 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; Anaerobic tank exhaust valve (37) operation method: 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 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 waiting; Denitrification process: S4, after the cycle of the denitrification tank (1) is completed, the activated sludge is transferred to the anaerobic tank (2) which is in an empty waiting state, and the activated sludge which 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 set by the denitrification water level controller (21); then, the denitrification tank (1) starts the corresponding submersible agitator (16) to start the anoxic denitrification process until the denitrification end point; 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 decline 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 is lower than the ORP value corresponding to the pH normal control of the denitrification endpoint. When the ORP is lower than this ORP control range and there is no turning point rise during the pH decline process, the denitrification process is stopped; At the same time, the conductivity changes from a rapid decline to a slow decline, fluctuates back and forth or even rises as an auxiliary basis for judging the denitrification endpoint during the denitrification process; Aerobic process: S6, 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 such that the final DO concentration is greater than 1.5 mg / L and less than 3 mg / L; Static sedimentation and drainage and sludge discharge process: S7, after the 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 electric valve (11) of the decanter is opened, and the electric telescopic rod of the decanter (4) is slowly lowered to drain. After the drainage is completed, the electric valve (11) of the decanter is closed, and the electric telescopic rod of the decanter (4) returns to its original position. The nitrification sludge discharge pump (7) is turned on to discharge the remaining sludge. Then, the activated sludge in the denitrification tank (1) is transferred to the anaerobic tank (2) which is in an idle waiting state through the sludge supply pump (9). The cycle operation of the denitrification tank (1) is completed, and the denitrification tank (1) is re-added with nitrification liquid and activated sludge to start a new cycle. The entire system is repeatedly operated in this way; Operation method 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; 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.

9. An intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method, characterized in that: The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification system comprises the following specific steps: When the secondary effluent of the sewage treatment plant has a high ammonia nitrogen concentration or the total nitrogen purification requirement is high, the secondary effluent of the sewage treatment plant needs to enter the nitrification tank to aerobic nitrification treatment of the ammonia nitrogen in the secondary effluent. At this time, the water inlet can be selected in two ways: intermittent water inlet and continuous water inlet. The specific operation steps are as follows; When continuous water inflow is adopted, the continuous water inflow mode, the end point of intermittent nitrification reaction, continuous aerobic nitrification and 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 inflow 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 starts 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 continuous nitrification conversion of ammonia nitrogen in the subsequent continuous influent water is achieved; when the nitrification tank (22) reaches the end of intermittent nitrification, and when the denitrification tank (1) cycle operation is completed, the activated sludge in the denitrification tank (1) is transferred to the anaerobic tank (2), and 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) continues to wait for the next influent to reach the set water level, and then restarts aeration, and the cycle is repeated; When intermittent water inflow is adopted, the intermittent water inflow mode, the intermittent nitrification reaction end point and the nitrification liquid transfer are as follows: 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 stand and wait; thereafter, 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), and after the transfer is completed, the nitrification pool (22) can be refilled with water, and the cycle is repeated; Intermittent nitrification endpoint control method: S3, the controller (5) controls the nitrification reaction endpoint through the nitrification pH online detector (29) and the nitrification DO online detector (30) installed in the nitrification tank (22), and the controller (5) controls the aeration volume so that the DO is less than 3 mg / L; the controller (5) uses the pH value stopping decreasing and rising 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 nitrification reaction endpoint; Nitrate nitrogen determination and calculation of added carbon source: S4, the first sampling pump (31) and the second sampling pump (32) sample 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 added carbon source required for denitrification in this cycle according to the set carbon-nitrogen ratio (or if the total nitrogen concentration of the inlet water is known, the amount of added carbon source required to be added to the anaerobic tank (2) is calculated according to the total nitrogen concentration of the inlet water); Activated sludge transfer, external carbon source addition and anaerobic treatment: S5, at the end of each cycle of the denitrification tank (1), the activated sludge in the denitrification tank (1) is transferred in turn to the empty (no activated sludge) anaerobic tank (2) through the return sludge pump (9); at the same time, the controller (5) adds a quantitative amount of external carbon source to the anaerobic tank (2) through the external carbon source quantitative pump (10) according to the calculated amount of external carbon source, and 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 start stirring and anaerobic treatment is performed. 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; 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); Anaerobic exhaust valve (37) operation method: S6. 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 activated sludge or adds an external carbon source, open the anaerobic exhaust valve (37). One of the anaerobic tanks (2) is always in an anaerobic state, while the other is idle and waiting. Denitrification process: S7, after the cycle of the denitrification tank (1) is completed, the activated sludge is transferred to the anaerobic tank (2) which is in an empty waiting state, and the activated sludge which 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 set by the denitrification water level controller (21); then, the denitrification tank (1) starts the corresponding submersible agitator (16) to start the anoxic denitrification process until the denitrification end point; Denitrification endpoint 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 decline, 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 is lower than the ORP value corresponding to the pH normal control of the denitrification endpoint. When the ORP is lower than this ORP control range and there is no turning point rise during the pH decline, the denitrification process is stopped. At the same time, the conductivity changes from a rapid decline to a slow decline, fluctuates back and forth, or even rises as an auxiliary basis for judging the denitrification endpoint during the denitrification process. 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 such that the final DO concentration is greater than 1.5 mg / L and less than 3 mg / L; Static sedimentation and drainage and sludge discharge process: S10, after the 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 electric valve (11) of the decanter is opened, and the electric telescopic rod of the decanter (4) is slowly lowered to drain the water. After the drainage is completed, the electric valve (11) of the decanter is closed, and the electric telescopic rod of the decanter (4) returns to its original position, and the nitrification sludge discharge pump (7) is turned on to discharge the remaining sludge. Then, the activated sludge in the denitrification tank (1) is transferred to the anaerobic tank (2) in an idle waiting state through the sludge supply pump (9). The cycle operation of the denitrification tank (1) is completed, and the denitrification tank (1) is re-added with nitrification liquid and activated sludge to start a new cycle. The entire system repeats the cycle operation in this way; Operation method 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.

10. The intelligent intermittent double sludge denitrification nitrogen and phosphorus deep purification method according to claim 9, characterized in that: The secondary effluent from the sewage treatment plant can also be replaced by surface water from rivers and lakes or agricultural wastewater that is seriously eutrophicated.

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