Low-temperature synchronous short-cut nitrification and denitrification SBR (sequencing batch reactor) nitrogen removal method

Abstract

A low-temperature synchronous short-cut nitrification and denitrification SBR (sequencing batch reactor) nitrogen removal method relates to the field of biological nitrogen removal of sewage and comprises the following steps: S1, adding common activated sludge into an SBR reactor; s2, starting a short-cut nitrification-denitrification nitrogen removal process under the condition of 28-32 DEG C until the accumulation rate of nitrite in a nitration reaction stage reaches 75-80%; s3, culturing the low temperature resistance of the short-cut nitrification-denitrification nitrogen removal process through stepped cooling; and S4, establishing a synchronous short-cut nitrification-denitrification SBR nitrogen removal process under a low-temperature condition through batch water feeding. The technical problem that the short-cut nitrification process is poor in low-temperature sewage treatment effect can be solved, and the sewage treatment efficiency is further improved.

Description

Technical Field

[0001] The invention relates to the field of biological denitrification of sewage, in particular to a low-temperature synchronous short-range nitrification and denitrification SBR denitrification method. Background Art

[0002] The traditional biological denitrification process of sewage is roughly divided into three processes: ammoniation reaction stage, nitrification reaction stage and denitrification reaction stage. The traditional denitrification process has a large aeration volume and consumes a lot of electricity. In order to ensure the smooth progress of the denitrification stage, additional carbon sources need to be added. According to statistics, the average power consumption of sewage treatment in my country is 0.355 (kWh / m 3 ), the average carbon source consumption was 27.4 tons of water and medicine consumption (g COD / m 3 ), and there are always disadvantages such as high cost investment and complex process flow. It needs to be replaced by a new process with higher technological content, simpler process flow and more obvious treatment effect.

[0003] Nitrite type simultaneous partial nitrification and denitrification (SPND) refers to the short-term nitrification and denitrification stages in the same reactor, the entire denitrification process is composed of NH 4 + -N → NO 2 - -N→N 2 It can be achieved by effectively avoiding the oxidation of nitrite to nitrate. The process can effectively reduce the amount of aeration, save the addition of external carbon sources, reduce the amount of sludge produced, and achieve continuous water discharge, and has broad prospects for engineering applications.

[0004] In actual engineering applications, environmental conditions below the optimum temperature for microbial growth are one of the most difficult bottlenecks to overcome in this process. The most suitable temperature for short-term nitrification is close to 30°C, while the annual average water temperature of sewage treatment plants is around 20°C. The water temperature shows obvious seasonal changes. Even in summer, the water temperature of domestic sewage treatment plants is basically below 30°C. For large-scale sewage treatment plants, it is not feasible to heat sewage due to energy costs. Therefore, it is very important to study the control methods of short-term nitrification processes at normal and low temperatures. In addition, most of the current domestic sewage belongs to low carbon-nitrogen ratio sewage. Sufficient organic matter can ensure a high denitrification efficiency. How to avoid the loss of carbon sources during sewage treatment is an urgent problem to be solved in the field of sewage denitrification.

[0005] A Chinese invention patent with publication number CN 112960772 A discloses a biological denitrification device and method for segmented water inlet coupled with synchronous short-range nitrification and denitrification, which specifically discloses that municipal sewage is treated by inlet in four equal proportions. In the first stage, sewage enters the SBR reactor, is first anoxic and stirred, and then low-oxygen aeration and stirring are performed. When DO reaches about 1.5 g / L, aeration is stopped, and anoxic stirring is performed again; then the second, third, and fourth stages of water inlet are performed. After the anoxic and four-stage water inlet are completed, the SBR reactor is precipitated and drained; the invention combines segmented water inlet with short-range nitrification and denitrification, and the raw water enters each anoxic stage in stages, and denitrification is performed using the carbon source in the raw water to solve the problem of nitrate nitrogen. However, this staged water inlet method is that after the sewage enters the reactor, it is first anoxic stirred and then aerated stirred. That is, the sewage is first sent to the reactor, and then anoxic denitrification reaction is carried out through stirring, then nitrification reaction is carried out, and finally anoxic denitrification is carried out again. During the whole process, water inlet, denitrification reaction, nitrification reaction, and denitrification reaction are carried out alternately in sequence, and the sewage treatment efficiency needs to be further improved. Summary of the invention

[0006] The present invention aims to provide a low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method to solve the technical problem that the short-cut nitrification process has a poor effect on low-temperature sewage treatment and further improve the sewage treatment efficiency.

[0007] In order to achieve the above object, the specific scheme adopted by the present invention is: a low-temperature synchronous short-range nitrification and denitrification SBR denitrification method, comprising the following steps:

[0008] S1: Adding ordinary activated sludge into the SBR reactor;

[0009] S2: Start the short-cut nitrification-denitrification denitrification process at 28-32°C until the accumulation rate of nitrite in the nitrification reaction stage reaches 75-80%;

[0010] S3: Acclimate the low temperature resistance of the short-range nitrification-denitrification denitrification process through step-by-step cooling;

[0011] S4: Establish a synchronous short-range nitrification-denitrification SBR denitrification process under low temperature conditions through batch water inflow.

[0012] As a further optimization of the above technical solution: in step S1, after adding ordinary activated sludge, the sludge concentration in the reactor is 3500-4500 mg / L.

[0013] As a further optimization of the above technical solution: in step S2, the temperature in the reactor is maintained at 28-32°C and water is introduced into the reactor. Aeration is performed to make the dissolved oxygen content in the reactor 0.4-0.6 mg / L to carry out nitrification reaction. Aeration is stopped to carry out anoxic denitrification reaction. Sedimentation, water discharge, and idleness are repeated N times until the accumulation rate of nitrite in the nitrification reaction stage is 75-80%.

[0014] As a further optimization of the above technical solution: in step S3, the temperature gradient of the step cooling is 28°C, 25°C, 21°C, and 17°C.

[0015] As a further optimization of the above technical solution: Step S3 is specifically,

[0016] S301: maintaining the temperature in the SBR reactor at 28°C and introducing water into the reactor, aerating the reactor so that the dissolved oxygen content in the reactor is 0.4-0.6 mg / L to carry out nitrification reaction, stopping aeration to carry out anoxic denitrification reaction, settling, discharging water, and leaving idle, repeating N times until the accumulation rate of nitrite in the nitrification reaction stage is more than 80%;

[0017] S302: maintaining the temperature in the SBR reactor at 25°C and introducing water into the reactor, and the rest is the same as step S301;

[0018] S303: maintaining the temperature in the SBR reactor at 21° C. and introducing water into the reactor, and the rest is the same as step S301;

[0019] S304: Maintain the temperature in the SBR reactor at 17° C. and add water into the reactor. The rest is the same as step S301.

[0020] As a further optimization of the above technical solution: the accumulation rate of nitrite in the nitrification reaction stage is NAR,

[0021] As a further optimization of the above technical solution: in step S4, the single water inflow volume of the batch water inflow is 1 / 5 of the water discharge volume of each cycle.

[0022] As a further optimization of the above technical solution: in step S4, aeration is performed after a single water inlet is completed, and water is directly added after aeration without stirring, and the cycle is repeated five times.

[0023] As a further optimization of the above technical solution: trace element nutrient solution is added to the sewage when water enters the reactor, and the concentration of ferric chloride in the trace element nutrient solution is 1.25g / L, the concentration of copper sulfate is 0.4g / L, the concentration of manganese chloride is 1.27g / L, the concentration of sodium molybdate is 0.05g / L, the concentration of zinc sulfate is 0.55g / L, the concentration of cobalt chloride is 0.4g / L, the concentration of ethylenediaminetetraacetic acid is 1.25g / L, the concentration of calcium chloride is 1.37g / L, and the concentration of magnesium sulfide is 44.4g / L.

[0024] As a further optimization of the above technical solution: the addition ratio of trace element nutrient solution in sewage is 2mL / L.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention utilizes a gradient cooling method to acclimate the sludge in the SBR reactor, and can realize the rapid start-up of the short-range nitrification and denitrification SBR process under low temperature conditions, thereby being able to denitrify water at normal temperature and low temperature using a short-range nitrification and denitrification process.

[0027] 2. The present invention adopts a batch water inlet method to synchronize the nitrification and denitrification reactions in the SBR reactor, greatly shortening the sewage denitrification time and improving the sewage treatment efficiency. The sludge is domesticated by step cooling, which, on the one hand, enables it to start the short-range nitrification-denitrification process under low temperature environment, and on the other hand, the domesticated sludge combined with the batch water inlet method can not only utilize the carbon source in the sewage for denitrification, but also treat the sewage more efficiently and shorten the sewage treatment time.

[0028] In the reaction process of the synchronous short-range nitrification and denitrification of the present invention, there is no need to add an anoxic denitrification stage, and denitrification is carried out simultaneously during the water intake and the subsequent aerobic aeration stage. During batch water intake, the environment of the water intake stage is equivalent to an anoxic environment, and the rich carbon source contained in the water intake can participate in the denitrification reaction, without the need to add an additional carbon source. Aeration is started after water intake, and a low dissolved oxygen content (0.4-0.6 mg / L) is maintained. The oxygen introduced by aeration reacts with the ammonia nitrogen in the water intake to generate nitrite and a small amount of nitrate. Since the reactor maintains a high sludge concentration (>6g·MLSS / L), the low aeration volume cannot maintain the entire SBR in a uniform aerobic environment, and anoxic zones will exist. At the same time, the carbon source in the water intake acts as an electron donor to make NO 2 - -N and NO 3 - -N can be basically completely removed by denitrification reaction, and the nitrification reaction and denitrification reaction in the reactor can realize the denitrification treatment of sewage simultaneously during the water inlet and aeration stages.

[0029] 3. Directly adding water after the aeration stage without stirring can prevent the carbon source in the water from being consumed by other heterotrophic microorganisms too early, so that the carbon source can be retained as much as possible until the aeration stage and used by denitrifying bacteria.

[0030] 4. The present invention uses real-time monitoring data of dissolved oxygen and redox potential to accurately control the oxidation reaction of ammonia nitrogen, provide a basis for the operation process of SBR, and effectively improve the startup efficiency of the short-range nitrification-denitrification process.

[0031] 5. The present invention solves the problems of large carbon source loss in water, need for external carbon source, high operating cost, and susceptibility to low temperature in traditional biological denitrification processes. The present invention utilizes the operation strategy of gradient cooling and batch water inlet, combined with the technical advantages of synchronous short-range nitrification and denitrification technology, to maximize the use of carbon sources in low carbon-nitrogen ratio domestic sewage while achieving high-efficiency and low-energy denitrification of domestic sewage, and has the characteristics of easy control of process flow and strong resistance to low-temperature shock load. The start-up of the nitrite-type synchronous nitrification and denitrification process was achieved by adopting the method of five batches of water inlet. The concentrations of ammonia nitrogen and total nitrogen in the effluent meet the Class A emission standard of "Pollutant Discharge from Urban Sewage Treatment Plants" (GB 18918-2002). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The changes of DO and ORP in two SBR consecutive cycles in the short-cut nitrification-denitrification denitrification process at a temperature of 30°C;

[0033] Figure 2 This is the change diagram of the accumulation rate of nitrite in the SBR reactor after it is started at a temperature of 30°C;

[0034] Figure 3 This is the change diagram of nitrite accumulation rate in SBR reactor under direct cooling conditions;

[0035] Figure 4 This is the change diagram of ammonia nitrogen removal rate in SBR reactor under direct cooling conditions;

[0036] Figure 5 This is a graph showing the change in nitrite accumulation rate in the SBR reactor under step-cooling conditions;

[0037] Figure 6 This is the change diagram of ammonia nitrogen removal rate in SBR reactor under step cooling conditions;

[0038] Figure 7 This is the denitrification effect diagram of each stage of SBR during water influent-aerobic (5 cycles);

[0039] Figure 8 This is a diagram of the denitrification effect of each stage of SBR during water inlet-aerobic-anoxic (5 cycles). DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts not described and disclosed in detail in the following embodiments of the present invention should be understood as the prior art known or should be known to those skilled in the art, such as the structure of the SBR reactor.

[0041] The present invention discloses a low-temperature synchronous short-range nitrification and denitrification SBR denitrification method. The method adopts the SBR reactor in the prior art. For ease of understanding, the structure of the SBR reactor is briefly introduced first:

[0042] The present invention adopts a cylindrical SBR reactor made of organic glass, and the effective volume of the reactor is 12L, and the effective working volume is 10L. The size of the reactor is: 40cm in height and 20cm in inner diameter. The water inlet is 3L in each cycle, and the water inlet ratio is 0.3. The inlet and outlet water are realized by a peristaltic pump and a hose. The mode of aeration in the reactor is blast aeration. The outside of the reactor is wrapped with an electric heating insulation belt, and the temperature in the SBR reactor can be monitored by a temperature sensor. The SBR reactor is equipped with a sensor for detecting various data such as dissolved oxygen (DO), redox potential (ORP) and pH. The control system of the SBR reactor is composed of a PLC control cabinet and an intelligent control system software. By setting parameters, the operation of the SBR reactor can be controlled in real time: the start and end of the units such as water inlet, aeration, stirring, precipitation, water outlet, and standing.

[0043] After the SBR reactor is started, an intelligent control system is used to monitor the operation of the reactor in real time, detect the SBR online monitoring signal of the biological denitrification process of sewage treatment, and control the short-range nitrification-denitrification biological denitrification process. The sensors installed in the SBR reactor can transmit the detected data to the computer in real time. The control system can process and record the temperature, DO, pH, ORP and other data detected by the sensors in the SBR reactor online, and form a dynamic curve that can be viewed in real time, and store it in the form of a file to the computer hard disk. PLC associates each operating device, and controls the switches of the water inlet pump, water outlet pump, aeration pump, and agitator through software. The start and stop of each device can be freely combined. According to the needs of the experiment, the reactor's "water inlet", "aeration", "stirring", "idle", "drainage" and other working conditions can be manually set and timed to achieve different research purposes.

[0044] The low-temperature synchronous short-range nitrification and denitrification SBR denitrification method provided by the present invention comprises the following steps:

[0045] S1: Adding ordinary activated sludge into the SBR reactor, and making the activated sludge concentration reach about 4000 mg / L, preferably 3500-4500 mg / L through sequencing batch operation; in this embodiment, the sludge concentration in the SBR reactor is 4000 mg / L.

[0046] S2: Start the short-cut nitrification-denitrification denitrification process at 28-32°C until the accumulation rate of nitrite in the nitrification reaction stage reaches 75-80%; when starting the SBR reactor for short-cut nitrification-denitrification denitrification, the operation mode is pre-aeration (in order to remove the remaining COD in the reactor in the previous cycle), water inlet, aeration stage (nitrification process), anoxic stirring (denitrification process), sedimentation, water outlet and idle.

[0047] Specifically, since the most suitable temperature for the short-cut nitrification operation is close to 30°C, the short-cut nitrification and denitrification process is first started at 28-32°C to acclimate the sludge in the reactor, and the temperature environment in the reactor is maintained by heating with an electric heating belt;

[0048] In this embodiment, the temperature in the reactor is set to 30° C. by heating with an electric heating belt, and then water is introduced into the reactor. Introducing water into the reactor means introducing sewage to be treated, and the composition of the sewage to be treated is ammonium sulfate (237.5 mg / L), sodium bicarbonate (600 mg / L), potassium dihydrogen phosphate (42 mg / L), calcium chloride (194 mg / L) and magnesium sulfate heptahydrate (456 mg / L).

[0049] In order to maintain the normal growth of microorganisms in the SBR reactor, trace element nutrient solution needs to be added to the influent sewage to be treated, with a dosing ratio of 2mL / L. The composition of the trace element nutrient solution is: ferric chloride (1.25g / L), copper sulfate (0.4g / L), manganese chloride (1.27g / L), sodium molybdate (0.05g / L), zinc sulfate (0.55g / L), cobalt chloride (0.4g / L), ethylenediaminetetraacetic acid (1.25g / L), calcium chloride (1.37g / L), magnesium sulfide (44.4g / L). It should be noted that pre-aeration is required before each water inlet to remove the remaining COD in the reactor in the previous cycle.

[0050] After the water inlet stage is completed, aeration is added to the reactor to carry out short-term nitrification reaction. Since there is a corresponding relationship between the changes in dissolved oxygen, redox potential and ammonia nitrogen in the process of short-term nitrification and denitrification, in order to prevent excessive aeration from causing nitrite nitrogen to convert into nitrate nitrogen, the joint control of dissolved oxygen and redox potential has become the key to judging the end of short-term nitrification.

[0051] The specific process of short-term nitrification-denitrification denitrification is as follows: During the aeration stage, ammonia nitrogen in the influent will consume oxygen in the water. At this time, the dissolved oxygen in the reactor is in a stable state. The aeration degree is controlled to maintain DO at 0.4-0.6 mg / L. The low dissolved oxygen level can effectively inhibit the activity of nitrite oxidizing bacteria (NOB); when the degradation of ammonia nitrogen is about to be completed, the dissolved oxygen and redox potential will rise rapidly, and the increase in dissolved oxygen will be relatively large. The changes in the two serve as a sign of the completion of the short-term nitrification stage, and the system stops aeration at this time.

[0052] After aeration is stopped, the system is in the anoxic stage. Since there are still some heterotrophic microorganisms in the water, the dissolved oxygen will be rapidly degraded, the dissolved oxygen and redox potential will drop rapidly, and the system will begin the denitrification stage.

[0053] During the denitrification stage, the dissolved oxygen content is 0 and remains unchanged. During the process of nitrite being converted into nitrogen, the redox potential will drop rapidly. When the nitrite nitrogen is completely degraded, the redox potential will have an inflection point and then begin to slowly decline. This phenomenon is used as the end of the denitrification process.

[0054] After the denitrification process is completed, sedimentation, water discharge and idleness are carried out to complete an operation cycle of the short-range nitrification-denitrification denitrification process.

[0055] By real-time monitoring of the changes in dissolved oxygen and redox potential, aeration is performed to keep the dissolved oxygen content in the reactor at 0.4-0.6 mg / L to carry out short-range nitrification. Low dissolved oxygen levels can effectively inhibit the activity of NOB.

[0056] Figure 1 This is a diagram showing the changes in dissolved oxygen and redox potential during the two operating cycles of this embodiment. The intelligent control system can monitor the short-term nitrification and denitrification stages in real time online based on the changes in dissolved oxygen content and redox potential, effectively improving the reaction efficiency.

[0057] Figure 2 The figure shows the result of the change of nitrite accumulation rate over time in this embodiment. The denitrification effect in the reactor is not obvious in the early stage of startup. After the reactor has been running for 30 days, the nitrification process reaches stability and the NAR reaches about 78%, indicating that the short-range nitrification has been successfully started under normal temperature conditions and the system stops heating.

[0058] The effect of the short-range nitrification process is expressed by NAR (nitrite accumulation rate).

[0059] S3: The low temperature resistance of the short-range nitrification-denitrification denitrification process is acclimated by step cooling, that is, the low temperature resistance of the relevant microorganisms in the SBR reactor is acclimated; the cooling temperature gradient of the step cooling is 28°C → 25°C → 21°C → 17°C. After the short-range nitrification is stably operated under a certain temperature condition, the temperature is lowered; the step cooling of this embodiment specifically includes the following steps:

[0060] S301: maintaining the temperature in the SBR reactor at 28°C and pre-aerating the reactor to remove the remaining COD in the reactor in the previous cycle, then introducing water into the reactor, aerating the reactor so that the dissolved oxygen content in the reactor is 0.4-0.6 mg / L to carry out nitrification reaction, stopping aeration to carry out anoxic denitrification reaction, settling, discharging water, and idling, repeating N times until the accumulation rate of nitrite in the nitrification reaction stage is more than 80%;

[0061] S302: maintaining the temperature in the SBR reactor at 25°C and introducing water into the reactor, and the rest is the same as step S301;

[0062] S303: maintaining the temperature in the SBR reactor at 21° C. and introducing water into the reactor, and the rest is the same as step S301;

[0063] S304: maintaining the temperature in the SBR reactor at 17° C. and introducing water into the reactor, and the rest is the same as step S301;

[0064] like Figure 5 , 6 The NAR and ammonia nitrogen removal rate of SBR under step cooling conditions. When the step cooling method is adopted, the average NAR of the four temperature stages are 85.37%, 92.77%, 88.54%, and 86.54% respectively. The NAR value of the whole process can always be maintained above 80%, and the operation is stable. The ammonia nitrogen removal rate is above 88%. In some operating cycles, the ammonia nitrogen removal rate can reach 100%. This shows that the step cooling method is conducive to the operation of short-range nitrification under low temperature conditions.

[0065] S4: Establish a synchronous short-range nitrification-denitrification SBR denitrification process under low temperature conditions through batch water inflow.

[0066] The batch water inlet adopts five batches, and the single water inlet volume is 1 / 5 of the drainage volume of each cycle. Aeration is carried out after the single water inlet is completed. After the aeration is completed, water is directly added without stirring, and the cycle is repeated five times.

[0067] In this embodiment, the water inflow is 600 mL each time, the temperature in the SBR reactor is 17°C, and the test process includes pre-aeration (to remove the remaining COD in the reactor in the previous cycle), water inflow, aeration stage (nitrification process), sedimentation, water discharge and idleness. The water inflow and aeration stages are divided into five cycles, and the sludge concentration in the reactor is 6.57 (g·MLSS / L).

[0068] It should be noted that the concentration of ordinary sludge after adding in step S1 is 4000 mg / L. During the start-up of the short-range nitrification-denitrification denitrification process in step S2 and the step-by-step cooling and acclimatization of the short-range nitrification-denitrification denitrification process to the low temperature resistance in step S3, the sludge pump will be turned on to discharge the sludge appropriately after sedimentation and discharge to control the sludge concentration in the reactor. After five water inflows in the same cycle of the batch water inflow stage, the sludge concentration in the reactor is 6.57 (g·MLSS / L).

[0069] Through the control of the intelligent control system, the dissolved oxygen and redox potential are monitored in real time to achieve the best treatment effect. The drainage volume of each cycle is 3L, the water inlet ratio is 0.3, and the aeration method adopts intermittent aeration, so that AOB (ammonia oxidizing bacteria) can reproduce rapidly, while the activity of NOB will be inhibited, maintaining the stability of short-range nitrification capacity.

[0070] When the water inlet and aeration stages are divided into five cycles, the main reactions produced are as follows:

[0071] First water inflow: At this time, there is no nitrite nitrogen in the reactor, so no denitrification reaction occurs during the first water inflow;

[0072] First aeration: During the first water inflow, the sewage introduced into the reactor is aerated and comes into contact with oxygen, thereby causing nitrification to generate nitrite nitrogen.

[0073] Second water inflow: The environment at the water inflow stage is equivalent to an anoxic environment. The nitrite nitrogen generated in the first aeration stage undergoes anoxic denitrification reaction at this time (i.e., the second water inflow);

[0074] Second aeration: The sewage introduced into the reactor during the second water inflow is brought into contact with oxygen to cause nitrification reaction to generate nitrite nitrogen;

[0075] The third water inflow: The environment at the water inflow stage is equivalent to an anoxic environment. The nitrite nitrogen generated in the second aeration stage undergoes anoxic denitrification reaction at this time (i.e., the third water inflow);

[0076] The third aeration: The sewage introduced into the reactor during the third water inflow is contacted with oxygen to cause nitrification reaction to generate nitrite nitrogen;

[0077] The fourth water inflow: The environment at the water inflow stage is equivalent to an anoxic environment. The nitrite nitrogen generated in the third aeration stage undergoes anoxic denitrification reaction at this time (i.e., the fourth water inflow);

[0078] Fourth aeration: The sewage introduced into the reactor during the fourth water inflow is contacted with oxygen to cause nitrification reaction to generate nitrite nitrogen;

[0079] The fifth water inflow: The environment at the water inflow stage is equivalent to an anoxic environment. The nitrite nitrogen generated in the fourth aeration stage undergoes anoxic denitrification reaction at this time (i.e., the fifth water inflow);

[0080] The fifth aeration: the sewage introduced into the reactor during the fifth water inflow is contacted with oxygen to cause nitrification reaction to generate nitrite nitrogen;

[0081] It should be noted that during the five aerations for nitrification, the oxygen content is low, and aerobic and anaerobic zones are formed in the reactor. In the aerobic zone, the sewage contacts with oxygen to cause nitrification to generate nitrite nitrogen, while the anaerobic zone can provide nitrite nitrogen for anoxic denitrification. Therefore, the anoxic denitrification process can run through the entire water inlet stage and aeration stage, and there is no need to set up an additional anoxic stirring section. This is because the short-term nitrification-denitrification denitrification process was started and stepped cooling was carried out in the early stage to acclimate the short-term nitrification-denitrification denitrification process, so that the acclimated sludge in the reactor has higher activity. In the low oxygen content environment of the aeration stage, nitrification and denitrification reactions can be carried out simultaneously, thereby improving the treatment efficiency of sewage denitrification. In addition, although there was no denitrification reaction after the fifth aeration, the amount of nitrite nitrogen produced during the fifth aeration was very small, and the aeration process was accompanied by denitrification reaction, so no special denitrification was required to meet the discharge water requirements.

[0082] like Figure 7 The figure shows the denitrification effect of the five cycle stages of the SBR five-time water inlet-aeration cycle. In the process of establishing the synchronous short-range nitrification-denitrification SBR denitrification process under low temperature conditions by batch water inlet of the present invention, water is directly inlet after the aeration stage without stirring. At this time, the environment of the water inlet stage is equivalent to an anoxic environment, and anoxic denitrification is completed synchronously during water inlet. In addition, each water inlet contains a rich carbon source, and the denitrification speed is particularly fast, NO 2 - -N and NO 3 - -N can be completely removed in this process, and the denitrification stage can be completed quickly. Each cycle takes about 4.2 hours, and 6 cycles can be run every day. The final effluent inorganic nitrogen concentration is 11.06 mg / L, which meets the national Class A emission standard.

[0083] In order to further prove the experimental effect of the present invention, the following comparative experiments were carried out:

[0084] Comparative experiment 1

[0085] The overall steps of this comparative experiment 1 are the same as those of the above embodiment, except that in step S3 of this embodiment, a direct cooling method is used to cultivate the low temperature tolerance of relevant microorganisms in the sludge in the SBR reactor.

[0086] When direct cooling is adopted, after the SBR reactor with a temperature of 30°C in step S2 ends the current cycle, the temperature is reduced to 17°C, and pre-aeration is performed in the reactor to remove the remaining COD in the reactor in the previous cycle, and then water is introduced into the reactor, and aeration is performed to make the dissolved oxygen content in the reactor 0.4-0.6 mg / L to carry out nitrification reaction, and aeration is stopped to carry out anoxic denitrification reaction, sedimentation, water discharge, and idleness are repeated N times.

[0087] The test results are as follows Figure 3 , 4 As shown in the figure, when the direct cooling method is adopted, the NAR value is not high. It is not until the reaction is run for 51 days that the NAR can reach more than 80%. The removal rate of ammonia nitrogen is above 89%. Although most of the ammonia nitrogen can be removed, when the ammonia nitrogen is converted into nitrite nitrogen, the nitrite nitrogen will further convert into nitrate nitrogen, resulting in unsatisfactory short-range nitrification effect. This is because the sludge that has been domesticated at 30℃ is not suitable for direct low temperature conditions.

[0088] Comparative experiment 2

[0089] The overall steps of this comparative experiment 2 are the same as those of the above embodiment, except that, in this embodiment, step S4 adopts the water inlet-aerobic-anoxic (5 cycles) method to establish a short-range nitrification-denitrification SBR denitrification process under low temperature conditions, wherein aeration stirring is performed in the aerobic stage, and anoxic stirring is performed in the anoxic stage without adding additional carbon source.

[0090] The experimental results of the comparative experiment 2 are as follows Figure 8 As shown, Figure 7 The experimental results of the synchronous short-cut nitrification-denitrification SBR denitrification process under low temperature conditions in the embodiment of the present invention are shown in FIG. Figure 7 , 8By comparison, it can be seen that after the anoxic stage is omitted in the present invention, not only can the water quality of sewage denitrification meet the effluent requirements, but also the sewage denitrification time can be significantly shortened. This is because in the present invention, the environment at the water inlet stage is equivalent to an anoxic environment, and anoxic denitrification is completed simultaneously during water inlet, which can save hydraulic retention time, reduce anoxic stage compared to the traditional operation mode (i.e., comparative test 2), save operating costs, and fully utilize the carbon source in the raw water for denitrification at the water inlet stage. Under traditional experimental conditions, the carbon source will be consumed by other aerobic heterotrophic bacteria in the aerobic stage, thereby reducing the denitrification capacity of the anoxic stage, thereby improving the carbon source utilization rate.

[0091] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-temperature synchronous short-range nitrification and denitrification SBR denitrification method, characterized in that: The following steps are involved: S1: Adding ordinary activated sludge into the SBR reactor; S2: Start the short-cut nitrification-denitrification denitrification process at 28-32°C until the accumulation rate of nitrite in the nitrification reaction stage reaches 75-80%; S3: Acclimate the low temperature resistance of the short-range nitrification-denitrification denitrification process through step-by-step cooling; S4: Establish a synchronous short-range nitrification-denitrification SBR denitrification process under low temperature conditions through batch water inflow.

2. A low-temperature synchronous short-range nitrification and denitrification SBR denitrification method as claimed in claim 1, characterized in that: In step S1, after adding ordinary activated sludge, the sludge concentration in the reactor is 3500-4500 mg / L.

3. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 1, characterized in that: Step S2 is specifically as follows: maintaining the temperature in the reactor at 28-32° C. and introducing water into the reactor, aerating the reactor so that the dissolved oxygen content in the reactor is 0.4-0.6 mg / L to carry out nitrification reaction, stopping aeration to carry out anoxic denitrification reaction, settling, discharging water, and idling, repeating N times until the accumulation rate of nitrite in the nitrification reaction stage is 75-80%.

4. A low-temperature synchronous short-range nitrification and denitrification SBR denitrification method as claimed in claim 1, characterized in that: In step S3, the temperature gradient of the step cooling is 28°C, 25°C, 21°C, and 17°C.

5. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 4, characterized in that: Step S3 specifically comprises: S301: maintaining the temperature in the SBR reactor at 28°C and introducing water into the reactor, aerating the reactor so that the dissolved oxygen content in the reactor is 0.4-0.6 mg / L to carry out nitrification reaction, stopping aeration to carry out anoxic denitrification reaction, settling, discharging water, and leaving idle, repeating N times until the accumulation rate of nitrite in the nitrification reaction stage is more than 80%; S302: maintaining the temperature in the SBR reactor at 25°C and introducing water into the reactor, and the rest is the same as step S301; S303: maintaining the temperature in the SBR reactor at 21° C. and introducing water into the reactor, and the rest is the same as step S301; S304: Maintain the temperature in the SBR reactor at 17° C. and add water into the reactor. The rest is the same as step S301.

6. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 3 or 5, characterized in that: The accumulation rate of nitrite in the nitrification reaction stage is NAR.

7. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 1, characterized in that: In step S4, the single water intake volume of the batch water intake is 1 / 5 of the water discharge volume of each cycle.

8. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 1, characterized in that: In step S4, the incoming water is divided into five equal parts, and the water inlet mode is adjusted to batch water inlet. Aeration is performed after a single water inlet is completed. After aeration is completed, the next batch of water is directly inlet without stirring, and the cycle is repeated five times.

9. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 1, characterized in that: Trace element nutrient solution is added to the sewage when it enters the reactor. The concentration of ferric chloride in the trace element nutrient solution is 1.25g / L, the concentration of copper sulfate is 0.4g / L, the concentration of manganese chloride is 1.27g / L, the concentration of sodium molybdate is 0.05g / L, the concentration of zinc sulfate is 0.55g / L, the concentration of cobalt chloride is 0.4g / L, the concentration of ethylenediaminetetraacetic acid is 1.25g / L, the concentration of calcium chloride is 1.37g / L, and the concentration of magnesium sulfide is 44.4g / L.

10. A low-temperature synchronous short-cut nitrification and denitrification SBR denitrification method as claimed in claim 9, characterized in that: The addition ratio of trace element nutrient solution in sewage is 2mL / L.

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