Device and method for purifying tail water through series connection of ultrasonic cavitation and aerobic starvation sludge

Abstract

The invention provides a device and a method for purifying tail water through series connection of ultrasonic cavitation and aerobic starvation sludge, and belongs to the technical field of sewage treatment. According to the method, the tail water of the sewage plant is pretreated through ultrasonic cavitation, and physicochemical indexes of organic matters in the tail water are preliminarily degraded under high pressure of cavitation bubbles; and an aerobic starvation sludge technology is further connected in series, the activated sludge is aerated, the aerobic starvation state of the sludge is controlled, the sludge particle structure is changed, the microbial community structure is optimized, and the biodegradation efficiency of organic matters in the sewage tail water is improved, so that the biotoxicity of the sewage is effectively reduced. And further adjusting ultrasonic power and sludge aeration time to treat different types of sewage and tail water so as to determine an optimal functional ratio. According to the method disclosed by the invention, the tail water of the sewage plant is treated by using the ultrasonic cavitation in series connection with the aerobic starvation sludge, so that the physicochemical indexes and the biotoxic effect of organic pollutants in the tail water can be effectively reduced, the resource consumption and the treatment cost of tail water treatment are reduced, and the recycling of water resources is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a device and method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge. Background Art

[0002] As an important facility for water environmental pollution control, the tail water discharge of sewage treatment plants poses a potential threat to the ecological environment safety of the receiving water body. Although traditional sewage treatment processes can effectively remove most conventional pollutants (such as COD, BOD, nitrogen, phosphorus, etc.), there are still various refractory toxic and harmful substances remaining in the tail water, such as heavy metals, persistent organic pollutants, pharmaceuticals and personal care products, etc. These trace toxic and harmful substances have bioaccumulation and biomagnification effects, posing a potential threat to the ecological system of the receiving water body and human health.

[0003] However, existing advanced treatment technologies for tail water, such as activated carbon adsorption, advanced oxidation, etc., have problems such as high cost, secondary pollution, unstable treatment effects, etc., and are difficult to meet the increasingly strict environmental protection requirements. The conventional activated sludge process has low removal efficiency for refractory organic matters (such as antibiotics, microplastics) and trace toxic substances (such as heavy metals, drug residues). And it is difficult to stably meet the first-class A standard for tail water discharge through traditional processes, and advanced treatment technologies need to be further combined. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a device and method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge. The device and method can efficiently remove toxic and harmful substances in the tail water, reduce the toxicity of the tail water, and have the advantages of low cost, simple operation, no secondary pollution, etc., ensuring the safety of the recycling of tail water resources.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge. The device includes an ultrasonic cavitation device and an aeration tank, both of which are connected to the tail water reaction system. The tail water reaction system includes a reaction tank, a sedimentation tank, a reservoir, and a collection tank connected in sequence. The ultrasonic cavitation device is used to degrade organic pollutants in the tail water under high-energy ultrasonic waves, obtain pretreated tail water, and transport it to the reaction tank. The aeration tank is used to continuously aerate the activated sludge to keep the sludge in an aerobic starved state, obtain aerobic starved sludge, and also transport it to the reaction tank. The reaction tank is used to mix and aerate the pretreated tail water and aerobic starved sludge to deeply degrade organic pollutants, obtain a tail water mixture, and transport it to the sedimentation tank. The sedimentation tank is used to statically precipitate the tail water mixture. The supernatant is transported to the reservoir, part of the sludge is refluxed to the reaction tank, and the remaining sludge is discharged. The reservoir is used to collect the supernatant and transport it to the collection tank. The collection tank is used to perform solid-phase extraction on the organic matter in the supernatant. The purified water after extraction is discharged for use, and the waste liquid is discharged and collected.

[0007] Further, the ultrasonic cavitation device includes a device body. A high-energy wave converter and a high-energy wave probe are connected inside the device body, and a temperature control device is arranged at the bottom. The high-energy wave converter is also connected to a high-energy wave generator. The number of the high-energy wave probes is several, and several high-energy wave probes are arranged at a position 1 / 3 - 1 / 2 below the tail water liquid level in a uniformly distributed manner. The temperature control device is used to cool the device when the temperature of the device body exceeds 60°C.

[0008] Further, an organic matter extraction device is arranged in the collection tank. The organic matter extraction device includes a volumetric flask, a solid-phase extraction column, and a collection tube arranged in sequence from top to bottom. The solid-phase extraction column is also connected to a purified water pipe. An organic phase and ultrapure water are arranged in the volumetric flask. The collection tube is also connected to a waste liquid pipe. The volumetric flask is used to perform operations of activating the organic phase and cleaning with ultrapure water on the solid-phase extraction column in sequence. The solid-phase extraction column is used to enrich the supernatant. After enrichment, the organic matter in the supernatant is rinsed into the collection tube and then discharged and collected for treatment through the waste liquid pipe. The purified tail water is discharged for use through the purified water pipe.

[0009] Further, a water collection pipe and a drain pipe are arranged on the reservoir. The water collection pipe is used to transport the supernatant to the reservoir. A water system filter membrane is arranged on the drain pipe, which is used to filter the supernatant and transport it to the collection tank. Among them, the specification of the water system filter membrane is 0.45μm.

[0010] Further, a sludge inlet pipe and a sludge discharge pipe are provided on the aeration tank. The sludge inlet pipe is used to transport activated sludge into the aeration tank, and the sludge discharge pipe is used to transport aerobic starved sludge into the reaction tank. A water inlet pipe and a water delivery pipe are provided on the reaction tank. The water inlet pipe is used to transport pretreated tail water into the reaction tank, and the water delivery pipe is used to transport the tail water mixture into the sedimentation tank. A sludge return pipe, a surplus sludge pipe, and a water collection pipe are provided on the sedimentation tank. The sludge return pipe is used to return part of the sludge to the reaction tank, and the surplus sludge pipe is used to discharge surplus sludge. The water collection pipe is used to transport the supernatant to the reservoir.

[0011] The present invention also provides a method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge. This method is applied to the device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge as described above. The method includes:

[0012] S1. The ultrasonic cavitation device degrades organic pollutants in the tail water under high-energy ultrasonic waves to obtain pretreated tail water and transports it to the reaction tank. The aeration tank continuously aerates the activated sludge to keep the sludge in an aerobic starved state, and the obtained aerobic starved sludge is also transported to the reaction tank.

[0013] S2. The reaction tank mixes and aerates the pretreated tail water and aerobic starved sludge to deeply degrade organic pollutants, obtains a tail water mixture and transports it to the sedimentation tank.

[0014] S3. The sedimentation tank statically precipitates the tail water mixture. The obtained supernatant is transported to the reservoir, part of the obtained sludge is returned to the sedimentation tank, and the surplus sludge is discharged.

[0015] S4. The reservoir collects the supernatant and transports it to the collection tank. The collection tank performs solid-phase extraction on the organic matter in the supernatant, and the purified water after extraction is discharged for utilization, and the waste liquid is discharged and collected.

[0016] Further, in step S1, the high-energy wave generator in the ultrasonic cavitation device sets the ultrasonic frequency at 20 - 100 kHz, the power density at 0.1 - 1.0 W / mL, and the tail water pretreatment time greater than 0 and less than or equal to 30 min. The concentration of the activated sludge input into the aeration tank is 2000 - 5000 mg / L, the dissolved oxygen is maintained at 2 - 4 mg / L, the activated sludge aeration reaction time is greater than 0 and less than or equal to 10 d, and the power of the sludge aeration pump is set at 50 - 80 W.

[0017] Further, in step S2, in the reaction tank, the dissolved oxygen is 1 - 2 mg / L, the temperature is 25 - 35 °C, the pH value is 6.5 - 8.5, and the hydraulic retention time is greater than 0 and less than or equal to 16 h.

[0018] Further, in step S4, the solvent contained in the volumetric flask in the collection pool is anhydrous methanol and ultrapure water, the injection volume is 10 mL, the flow rate is 10 mL / min, the specification of the solid-phase extraction column is HLB (hydrophilic-lipophilic balance) 500 mg / 6 mL, and the tail water flow rate is 10 mL / min.

[0019] The present invention also provides an application of the method as described above in purifying the tail water of a sewage treatment plant. The influent COD content of the tail water of the sewage treatment plant is 40 - 50 mg / L, the BOD5 content is 10 - 20 mg / L, the effluent COD content is 10 - 20 mg / L, and the BOD5 content is 5 - 10 mg / L. And the toxicity test of the tail water organic waste liquid is carried out with Daphnia magna as a model organism.

[0020] In actual operation, in the ultrasonic cavitation device, when the ultrasonic frequency is 40 kHz, the power density is 0.5 W / mL, and the treatment time is 20 min, the degradation rate of antibiotic substances in the tail water can reach 40% - 50%. In the aeration tank, the sludge concentration is controlled by adjusting the tail water flow rate and the sludge return ratio. In actual operation, when the sludge concentration is controlled at 3000 mg / L, the removal effect of toxic and harmful substances in the tail water is the best. Further, the sludge treatment system returns part of the treated sludge to the front end of the reaction tank through the sludge return system to maintain the sludge concentration and activity in the reaction tank. The excess sludge is discharged through the sludge discharge system for subsequent sludge treatment and disposal. Compared with the traditional activated sludge method, after adopting this technology, the excess sludge production is reduced by about 50%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention utilizes the synergistic effect of ultrasonic cavitation and aerobic starved sludge technology, gives full play to the advantages of the two technologies, can significantly improve the removal efficiency of toxic and harmful substances in the tail water, effectively reduce the toxicity of the tail water, and improve the effluent quality;

[0023] (2) The present invention uses ultrasonic cavitation pretreatment to reduce the difficulty and load of aerobic starved sludge treatment, reduce the sludge dosage and treatment time, thereby reducing the operating cost. At the same time, this method does not require the use of expensive chemical agents, avoiding secondary pollution. At the same time, the excess sludge is reasonably utilized to reduce the excess sludge production. Description of the Drawings

[0024] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a proportional limitation.

[0025] Figure 1Schematic structural diagram of a device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge provided by an embodiment of the present invention;

[0026] Figure 2 Schematic structural diagram of an ultrasonic cavitation device in an embodiment of the present invention;

[0027] Figure 3 COD content changes in tail water treated by single ultrasonic treatment and ultrasonic in series with aerobic starved sludge;

[0028] Figure 4 Toxicity characterization of Daphnia magna after ultrasonic in series with aerobic starved sludge treating organic matter in tail water.

[0029] In the figure: 1 - ultrasonic cavitation device, 2 - aeration tank, 3 - reaction tank, 4 - sedimentation tank, 5 - reservoir, 6 - collection tank, 7 - high-energy wave generator, 8 - high-energy wave converter, 9 - high-energy wave probe, 10 - temperature control device, 11 - water inlet pipe, 12 - sludge inlet pipe, 13 - sludge discharge pipe, 14 - sludge return pipe, 15 - excess sludge pipe, 16 - water delivery pipe, 17 - water collection pipe, 18 - drain pipe, 19 - water system filter membrane, 20 - volumetric flask, 21 - solid-phase extraction column, 22 - collection pipe, 23 - waste liquid pipe, 24 - purified water pipe. Detailed implementation manners

[0030] The inventors' research found that the use of ultrasonic cavitation technology and aerobic starved sludge technology to treat refractory organic pollutants in sewage has attracted wide attention. Ultrasonic cavitation technology utilizes the cavitation effect of ultrasonic waves in liquids to generate local high temperature and high pressure and strong shear force, which can effectively degrade organic matter and inactivate microorganisms. The aerobic starved sludge technology induces stress responses in sludge microorganisms by controlling the starvation time of the sludge, improving their adsorption and degradation capabilities for toxic and harmful substances. However, when using ultrasonic cavitation technology or aerobic starved sludge technology alone to treat the tail water of sewage treatment plants, there are problems such as low treatment efficiency, high energy consumption, and high operating costs.

[0031] Therefore, it is of great practical significance to develop an efficient, low-cost, and environmentally friendly method for purifying the tail water of sewage treatment plants. In view of the above situation, the present invention provides a method for purifying the tail water of sewage treatment plants by ultrasonic cavitation in series with aerobic starved sludge, which has the advantages of high pollutant removal efficiency, reduction of tail water toxicity, no secondary pollution, low cost, and low energy consumption, ensuring the effective removal of organic matter in the tail water, reducing the toxicity of the tail water, and ensuring the safety of the recycled utilization of tail water resources.

[0032] The present invention will be described in detail below in combination with specific implementation manners.

[0033] The present invention provides a device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge, as Figure 1As shown in the figure, the device includes an ultrasonic cavitation device 1 and an aeration tank 2, both of which are connected to the tail water reaction system. The tail water reaction system includes a reaction tank 3, a sedimentation tank 4, a reservoir 5, and a collection tank 6 connected in sequence. The ultrasonic cavitation device 1 is used to degrade organic pollutants in the tail water under high-energy ultrasonic waves, obtain pretreated tail water, and transport it to the reaction tank 3. The aeration tank 2 is used to continuously aerate the activated sludge to keep the sludge in an aerobic starvation state, obtain aerobic starvation sludge, and also transport it to the reaction tank 3. The reaction tank 3 is used to mix and aerate the pretreated tail water and aerobic starvation sludge to deeply degrade organic pollutants, obtain a tail water mixture, and transport it to the sedimentation tank 4. The sedimentation tank 4 is used to statically precipitate the tail water mixture. The supernatant is transported to the reservoir 5, part of the sludge is refluxed to the reaction tank 3, and the remaining sludge is discharged. The reservoir 5 is used to collect the supernatant and transport it to the collection tank 6. The collection tank 6 is used to perform solid-phase extraction on the organic matter in the supernatant. The purified water after extraction is discharged for use, and the waste liquid is discharged and collected.

[0034] As Figure 2 shown, the ultrasonic cavitation device 1 includes a device body. Inside the device body, a high-energy wave converter 8 and a high-energy wave probe 9 are connected. A temperature control device 10 is arranged at the bottom. The high-energy wave converter 8 is also connected to a high-energy wave generator 7. The number of high-energy wave probes 9 is several, and several high-energy wave probes 9 are arranged at a position 1 / 3 to 1 / 2 below the tail water liquid level in a uniformly distributed manner. The temperature control device 10 is used to cool the device when the temperature of the device body exceeds 60°C.

[0035] It can be understood that an organic matter extraction device is arranged in the collection tank 6. The organic matter extraction device includes a volumetric flask 20, a solid-phase extraction column 21, and a collection tube 22 arranged in sequence from top to bottom. The solid-phase extraction column 21 is also connected to a purified water pipe 24. An organic phase and ultrapure water are arranged in the volumetric flask 20. The collection tube 22 is also connected to a waste liquid pipe 23. The volumetric flask 20 is used to perform operations of activating the organic phase and cleaning with ultrapure water on the solid-phase extraction column 21 in sequence. The solid-phase extraction column 21 is used to enrich the supernatant. After enrichment, the organic matter in the supernatant is rinsed into the collection tube 22 and then discharged and collected for treatment through the waste liquid pipe 23. The purified tail water is discharged for use through the purified water pipe 24.

[0036] A water collection pipe 17 and a drain pipe 18 are arranged on the reservoir 5. The water collection pipe 17 is used to transport the supernatant to the reservoir 5. A water system filter membrane 19 is arranged on the drain pipe 18, which is used to filter the supernatant and transport it to the collection tank 6. Among them, the specification of the water system filter membrane 19 is 0.45 μm.

[0037] An inlet sludge pipe 12 and an outlet sludge pipe 13 are arranged on the aeration tank 2. The inlet sludge pipe 12 is used to transport activated sludge into the aeration tank 2, and the outlet sludge pipe 13 is used to transport aerobic starved sludge into the reaction tank 3. An inlet water pipe 11 and a water delivery pipe 16 are arranged on the reaction tank 3. The inlet water pipe 11 is used to transport pretreated tail water into the reaction tank 3, and the water delivery pipe 16 is used to transport the tail water mixture to the sedimentation tank 4. A sludge return pipe 14, a surplus sludge pipe 15 and a water collecting pipe 17 are arranged on the sedimentation tank 4. The sludge return pipe 14 is used to return part of the sludge to the reaction tank 3, and the surplus sludge pipe 15 is used to discharge surplus sludge. The water collecting pipe 17 is used to transport the supernatant to the reservoir 5.

[0038] The present invention also provides a method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge. This method is applied to the device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge as described above. The method includes:

[0039] S1. The ultrasonic cavitation device 1 degrades organic pollutants in the tail water under high-energy ultrasonic waves to obtain pretreated tail water and transports it to the reaction tank 3. The aeration tank 2 continuously aerates the activated sludge to keep the sludge in an aerobic starved state, and the obtained aerobic starved sludge is also transported to the reaction tank 3.

[0040] S2. The reaction tank 3 mixes and aerates the pretreated tail water and the aerobic starved sludge to deeply degrade organic pollutants, obtains a tail water mixture and transports it to the sedimentation tank 4.

[0041] S3. The sedimentation tank 4 statically precipitates the tail water mixture. The obtained supernatant is transported to the reservoir 5, part of the obtained sludge is returned to the reaction tank 3, and the surplus sludge is discharged.

[0042] S4. The reservoir 5 collects the supernatant and transports it to the collection tank 6. The collection tank 6 performs solid-phase extraction on the organic matter in the supernatant. The purified water after extraction is discharged for use, and the waste liquid is discharged and collected.

[0043] Example 1

[0044] In this example, the activated sludge and tail water of a certain municipal sewage treatment plant in Changzhou City were used for experiments. The quality of the tail water was as follows: COD was 50 mg / L, ammonia nitrogen was 5 mg / L, total phosphorus was 0.5 mg / L, and the concentrations of heavy metals copper, zinc, lead, and cadmium were 0.05 mg / L, 0.1 mg / L, 0.02 mg / L, and 0.01 mg / L respectively. Using the method of the present invention to treat this tail water, the specific steps are as follows:

[0045] (1) Ultrasonic cavitation pretreatment: Introduce the tail water into the ultrasonic reactor. When the ultrasonic frequency is 30 kHz and the sound intensity is 1.2 W / cm 2Ultrasonic cavitation treatment was carried out under the condition of , and the treatment time was 20 min. (2) Aerobic starved sludge treatment: The tail water pretreated by ultrasonic cavitation was introduced into the aerobic starved sludge reactor, and the dissolved oxygen concentration was controlled at 3 mg / L, the sludge concentration was 2500 mg / L, and the sludge starvation times were selected as 0 d, 2 d, 5 d, and 10 d. (3) The mixing reaction time of aerobic starved sludge and tail water was set for 16 h, and then the effluent from the aerobic starved sludge reactor was introduced into the sedimentation tank for sedimentation separation, and the sedimentation time was 24 h. (4) The treated tail water was subjected to organic matter extraction, and the organic matter indexes of the treated tail water were detected.

[0046] The experimental results are as Figure 3 (a) After single ultrasonic treatment for 20 min, the COD content in the tail water decreased to 32 mg / L. Figure 3 (b) When ultrasonic was in series with aerobic starved sludge, the starved sludge with 0 d had no significant effect on COD degradation, while the COD content decreased after the tail water was treated with the starved sludge for 2 d, 5 d, and 10 d. Among them, the starved sludge with 10 d had the best COD degradation effect, reaching 10 mg / L. The quality of the treated effluent was as follows: COD was 10 mg / L, ammonia nitrogen was 1 mg / L, total phosphorus was 0.1 mg / L, and the concentrations of heavy metals copper, zinc, lead, and cadmium were 0.01 mg / L, 0.02 mg / L, 0.005 mg / L, and 0.002 mg / L respectively, and the organic matter content in the tail water decreased significantly.

[0047] Example 2

[0048] In this example, the activated sludge and tail water of a certain industrial wastewater treatment plant in Changzhou were used for the experiment. The quality of the tail water of this wastewater treatment plant was as follows: COD was 48 mg / L, ammonia nitrogen was 12 mg / L, total phosphorus was 1 mg / L, and the concentration of persistent organic pollutant polychlorinated biphenyls (PCBs) was 0.08 mg / L. The method of the present invention was used to treat this tail water, and the specific steps were as follows: (1) Ultrasonic cavitation pretreatment: The tail water was introduced into the ultrasonic reactor, and ultrasonic cavitation treatment was carried out under the conditions of ultrasonic frequency of 35 kHz and sound intensity of 1.5 W / cm 2 , and the treatment time was 25 min. (2) Aerobic starved sludge treatment: The tail water pretreated by ultrasonic cavitation was introduced into the aerobic starved sludge reactor, and the dissolved oxygen concentration was controlled at 3.5 mg / L, the sludge concentration was 3000 mg / L, and the sludge starvation times were 0 d, 2 d, 5 d, and 10 d. (3) The mixing reaction time of aerobic starved sludge and tail water was set for 16 h, and then the effluent from the aerobic starved sludge reactor was introduced into the sedimentation tank for sedimentation separation, and the sedimentation time was 36 h. (4) The treated tail water was subjected to solid-phase extraction of organic matter, and the toxicity test was carried out with Daphnia magna as the model organism.

[0049] The experimental results are as Figure 4(a) After the ultrasonic wave is serially connected to aerobic starved sludge, the development of Daphnia magna is normal, and the spawning time is significantly advanced. Among them, the spawning time is earlier when the starved sludge for 5 days is used and the tail water is treated for 8 hours. Figure 4 (b) It shows that the number of spawning of Daphnia magna significantly increases after the ultrasonic wave is serially connected to aerobic starved sludge. The number of spawning is the largest when the starved sludge for 5 days is treated for 16 hours. Similarly, Figure 4 (c) The total number of spawning is the largest when the starved sludge for 5 days is treated for 16 hours. (d) The molting times of Daphnia magna gradually increase, indicating that the development of Daphnia magna is good and the reproduction is normal after the ultrasonic wave is serially connected to aerobic starved sludge to treat the tail water. However, Figure 4 (e) and (f) There are no obvious changes in the body length and heart rate of Daphnia magna. In summary, the quality of the treated effluent is as follows: COD is 30 mg / L, ammonia nitrogen is 6.4 mg / L, total phosphorus is 0.5 mg / L, and the concentration of persistent organic pollutant polychlorinated biphenyls (PCBs) is 0.002 mg / L. The toxicity of the tail water is significantly reduced.

[0050] The mechanism research of the present invention is that under the action of ultrasonic waves, a large number of cavitation bubbles are generated in the liquid. When these bubbles collapse instantaneously, extreme conditions such as high temperature, high pressure, and strong shock waves can destroy the molecular structures of toxic and harmful substances in the tail water, partially degrade them or convert them into forms that are more easily removed by subsequent treatment units, improve their biodegradability, and inactivate pathogenic microorganisms in the tail water at the same time. Since the activated sludge is in a starved state after aerobic aeration, it has a high affinity and metabolic activity for substrates, and can remove residual toxic and harmful substances in the tail water through adsorption, biodegradation, etc. At the same time, microorganisms in the sludge will secrete some enzymes and surface active substances during the metabolic process, further promoting the decomposition and transformation of toxic and harmful substances.

[0051] In summary, the device and method for purifying tail water by ultrasonic cavitation serially connected to aerobic starved sludge provided by the present invention pre-treat the tail water of the sewage treatment plant through ultrasonic cavitation, and initially degrade the physical and chemical indexes of the organic matter in the tail water under the high pressure of cavitation bubbles; further serially connect the aerobic starved sludge technology, aerate the activated sludge, control the aerobic starved state of the sludge, change the sludge particle structure, optimize the microbial community structure, and improve the biodegradation efficiency of the organic matter in the sewage tail water, so as to effectively reduce the biological toxicity of the sewage. Further, by adjusting the ultrasonic power and the sludge aeration time, different types of sewage tail water are treated to determine the best functional ratio. The method of the present invention uses ultrasonic cavitation serially connected to aerobic starved sludge to treat the tail water of the sewage treatment plant, which can effectively reduce the physical and chemical indexes and biological toxicity effects of organic pollutants in the tail water, reduce the resource consumption and disposal costs of tail water treatment, and realize the recycling of water resources.

[0052] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention. In actual applications, various changes can be made to them in form and details without departing from the spirit and scope of the present invention. Any person skilled in the art can make their respective changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. An ultrasonic cavitation tandem aerobic starved sludge tail water purification device, characterized in that: The device comprises: an ultrasonic cavitation device (1) and an aeration tank (2) both connected to a tail water reaction system, wherein the tail water reaction system comprises a reaction tank (3), a sedimentation tank (4), a water storage tank (5) and a collection tank (6) connected in sequence; The ultrasonic cavitation device (1) is used to degrade organic pollutants in tail water under high-energy ultrasonic waves to obtain pretreated tail water and transport it to the reaction tank (3); the aeration tank (2) is used to continuously aerate the activated sludge to keep the sludge in an aerobic starved state, and the obtained aerobic starved sludge is also transported to the reaction tank (3); The reaction tank (3) is used to mix and aerate the pretreated tail water and aerobic hungry sludge to deeply degrade organic pollutants, obtain a tail water mixture and transport it to the sedimentation tank (4); The sedimentation tank (4) is used to statically precipitate the tail water mixture, and the obtained supernatant is transported to the water storage tank (5), and the obtained part of the sludge is returned to the reaction tank (3), and the remaining sludge is discharged; The water reservoir (5) is used to collect the supernatant and transport it to the collection tank (6). The collection tank (6) is used to perform solid phase extraction on organic matter in the supernatant. The clean water after extraction is discharged for utilization, and the waste liquid is discharged for collection.

2. The device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 1 is characterized in that: The ultrasonic cavitation device (1) comprises a device body, wherein a high-energy wave converter (8) and a high-energy wave probe (9) connected to each other are arranged in the device body, and a temperature control device (10) is arranged at the bottom, wherein the high-energy wave converter (8) is also connected to a high-energy wave generator (7); the number of the high-energy wave probes (9) is several, and the several high-energy wave probes (9) are arranged at 1 / 3 to 1 / 2 below the tail water surface in a uniformly distributed manner; the temperature control device (10) is used to cool the device when the temperature of the device body exceeds 60°C.

3. The device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 1, characterized in that: An organic matter extraction device is arranged in the collection pool (6), and the organic matter extraction device comprises a volumetric flask (20), a solid phase extraction column (21) and a collection tube (22) arranged in sequence from top to bottom, the solid phase extraction column (21) is also connected to a water purification pipe (24), an organic phase and ultrapure water are arranged in the volumetric flask (20), and the collection tube (22) is also connected to a waste liquid pipe (23); The volumetric flask (20) is used to sequentially activate the organic phase and clean the solid phase extraction column (21) with ultrapure water. The solid phase extraction column (21) is used to enrich the supernatant. After the enrichment is completed, the organic matter in the supernatant is flushed into the collection tube (22) and then discharged from the waste liquid pipe (23) for collection and treatment. The purified tail water is discharged from the clean water pipe (24) for utilization.

4. The device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 1, characterized in that: The water reservoir (5) is provided with a water collecting pipe (17) and a drainage pipe (18), wherein the water collecting pipe (17) is used to transport the supernatant to the water reservoir (5); the drainage pipe (18) is provided with a water filter membrane (19) for filtering the supernatant and transporting it to the collection pool (6); Wherein, the specification of the water filter membrane (19) is 0.45 μm.

5. The device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 1, characterized in that: The aeration tank (2) is provided with a sludge inlet pipe (12) and a sludge discharge pipe (13), wherein the sludge inlet pipe (12) is used to transport the activated sludge into the aeration tank (2), and the sludge discharge pipe (13) is used to transport the aerobic starved sludge into the reaction tank (3); The reaction tank (3) is provided with a water inlet pipe (11) and a water delivery pipe (16), wherein the water inlet pipe (11) is used to deliver the pretreated tail water to the reaction tank (3), and the water delivery pipe (16) is used to deliver the tail water mixture to the sedimentation tank (4); The sedimentation tank (4) is provided with a sludge return pipe (14), a residual sludge pipe (15) and a water collecting pipe (17); the sludge return pipe (14) is used to return part of the sludge to the reaction tank (3); the residual sludge pipe (15) is used to discharge the residual sludge; and the water collecting pipe (17) is used to transport the supernatant to the water storage tank (5).

6. A method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge, characterized in that: The method is applied to a device for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to any one of claims 1 to 4; the method comprises: S1, ultrasonic cavitation device (1) degrades organic pollutants in tail water under high energy ultrasonic waves to obtain pretreated tail water and transport it to reaction tank (3); aeration tank (2) continuously aerates activated sludge to keep the sludge in an aerobic starved state, and obtains aerobic starved sludge which is also transported to reaction tank (3); S2, reaction tank (3) aerates the pretreated tail water and aerobic hungry sludge to deeply degrade organic pollutants, obtains tail water mixture and transports it to sedimentation tank (4); S3, the tail water mixture is statically precipitated in a sedimentation tank (4), the obtained supernatant is transported to a water storage tank (5), part of the obtained sludge is returned to the reaction tank (3), and the remaining sludge is discharged; S4, the water reservoir (5) collects the supernatant and transports it to the collection tank (6), the collection tank (6) performs solid phase extraction on the organic matter in the supernatant, and the clean water after extraction is discharged for utilization, and the waste liquid is discharged and collected.

7. The method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 6, characterized in that: In step S1, the high-energy wave generator (7) in the ultrasonic cavitation device (1) is set to have an ultrasonic frequency of 20 to 100 kHz, a power density of 0.1 to 1.0 W / mL, and a tail water pretreatment time of greater than 0 and less than or equal to 30 min; The concentration of activated sludge input into the aeration tank (2) is 2000-5000 mg / L, the dissolved oxygen is maintained at 2-4 mg / L, the activated sludge aeration reaction time is greater than 0 and less than or equal to 10 days, and the power of the sludge aeration pump is set at 50-80W.

8. The method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 6, characterized in that: In step S2, in the reaction tank (3), the dissolved oxygen is 1-2 mg / L, the temperature is 25-35° C., the pH value is 6.5-8.5, and the hydraulic retention time is greater than 0 and less than or equal to 16 h.

9. The method for purifying tail water by ultrasonic cavitation in series with aerobic starved sludge according to claim 6, characterized in that: In step S4, the solvents contained in the volumetric flask (20) in the collection pool (6) are anhydrous methanol and ultrapure water, the injection volume is 10 mL, the flow rate is 10 mL / min, the specification of the solid phase extraction column (21) is HLB 500 mg / 6 mL, and the tail water flow rate is 10 mL / min.

10. Use of the method according to any one of claims 6 to 9 in purifying tail water of a sewage plant, characterized in that: The influent COD content of the sewage treatment plant is 40-50 mg / L, and the BOD5 content is 10-20 mg / L; the effluent COD content is 10-20 mg / L, and the BOD5 content is 5-10 mg / L.

Images