Efficient enhanced sewage biological treatment system

Abstract

The invention discloses an efficient enhanced sewage biological treatment system which comprises a light enhancement tank, an anaerobic tank, an anoxic tank and an aerobic tank which are connected in sequence, and each tank is internally provided with activated sludge and a photocatalytic carrier; the sedimentation tank is connected with the aerobic tank and is used for carrying out mud-water separation on the treated water body and refluxing part of settled activated sludge and a photocatalytic carrier to the light strengthening tank and / or the anaerobic tank; the first cyclone is connected with the sedimentation tank and is used for separating the activated sludge and the photocatalytic carrier; the ultrasonic cleaning pipe is connected with the first cyclone and is used for removing a biological membrane on the surface of the photocatalytic carrier; and the second cyclone is connected with the ultrasonic cleaning pipe and is used for separating the photocatalytic carrier from the biological membrane, and the separated photocatalytic carrier flows back to the light enhancement tank and / or the anaerobic tank. According to the system, the treatment capacity of the system on refractory sewage is enhanced by coupling a photocatalysis technology and a biological method.

Description

TECHNICAL FIELD

[0001] The application relates to a high-efficiency reinforced sewage biological treatment system and belongs to the technical field of sewage treatment. BACKGROUND

[0002] Traditional sewage treatment methods often use biological methods, but the biological methods are difficult to deal with the treatment of refractory wastewater and have limited nitrogen removal efficiency. Photocatalysis technology is a technology for converting light energy into chemical energy, which is expected to use solar energy, i.e. natural light, to degrade pollutants in water, which has great significance for environmental protection, ecological balance maintenance, energy saving and sustainable development. SUMMARY

[0003] The application aims to provide a high-efficiency reinforced sewage biological treatment system, which couples photocatalysis technology with biological methods to improve the treatment capacity of the system for refractory wastewater.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows: A high-efficiency reinforced sewage biological treatment system comprises: sequentially connected light reinforcement pool, anaerobic pool, anoxic pool and aerobic pool, and active sludge and photocatalytic carriers are arranged in each pool; a sedimentation tank connected with the aerobic pool, used for separating sludge and water of the treated water body and returning part of the settled active sludge and photocatalytic carriers to the light reinforcement pool and / or the anaerobic pool; a first cyclone connected with the sedimentation tank, used for separating the active sludge and photocatalytic carriers; an ultrasonic cleaning pipe connected with the first cyclone, used for removing the biofilm on the surface of the photocatalytic carriers; a second cyclone connected with the ultrasonic cleaning pipe, used for separating the photocatalytic carriers and biofilm, and the separated photocatalytic carriers are returned to the light reinforcement pool and / or the anaerobic pool.

[0005] Preferably, the preparation method of the photocatalytic carriers is as follows: diatomite and melamine are mixed, ball milled and calcined to obtain catalytic particles; then the catalytic particles are sequentially immersed in an iron ion solution and a phytic acid solution, and after washing and drying, the photocatalytic carriers are obtained.

[0006] Preferably, the mass ratio of diatomite to melamine is 1:(1.2-1.5). The calcination conditions are as follows: under a nitrogen atmosphere, the temperature is raised to 500-600 DEG C at a rate of 3-5 DEG C / min, and the temperature is kept for 3-5 h.

[0007] Preferably, in the iron ion solution, the iron ion source is ferric chloride hexahydrate, and the concentration is 0.2-0.3 mol / L; the concentration of the phytic acid solution is 1-2 wt%. The mass ratio of the catalytic particles to the ferric chloride hexahydrate to the phytic acid is 1: (0.03-0.1) : (0.1-0.2).

[0008] Preferably, the catalytic particles are soaked in the ferric ion solution for 10-15 min and in the phytic acid solution for 15-25 min.

[0009] Preferably, the sewage enters through a water inlet pipe connected to the light intensification tank and the anaerobic tank.

[0010] Preferably, a mixed liquid reflux pipe is arranged on the aerobic tank and connected to the light intensification tank and the anoxic tank, for refluxing the sewage, activated sludge and light catalytic carrier mixed liquid in the aerobic tank to the light intensification tank and / or the anoxic tank.

[0011] Preferably, a light-emitting lamp tube and a pusher are further arranged in the light intensification tank.

[0012] Preferably, an ultrasonic cleaning pipe is further arranged between the sedimentation tank and the ultrasonic cleaning pipe, and part of the activated sludge and light catalytic carrier settled in the sedimentation tank enter the ultrasonic cleaning pipe for ultrasonic treatment.

[0013] Preferably, a direct discharge pipe is further arranged at the outlet of the ultrasonic cleaning pipe and connected to the light intensification tank and / or the anaerobic tank.

[0014] The present application has the following advantages: 1. The photocatalyst (g-C3N4 formed on the carrier after calcination of melamine) on the light catalytic carrier is excited by photon energy, and the electrons are transferred from the valence band to the conduction band to generate photoelectron-hole pairs. The photoelectron-hole pairs interact with small molecules such as oxygen molecules and water molecules adsorbed on the surface of the semiconductor to generate super-oxidative hydroxyl radicals and superoxide anions, which can decompose refractory pollutants into small molecules and improve the biodegradability of wastewater. When combined with the biological method, the activated sludge can further mineralize the small molecule products into carbon dioxide and water to achieve the degradation and mineralization of pollutants. Meanwhile, the photoelectrons generated by the photocatalyst have strong reducing properties and can reduce nitrate nitrogen in the wastewater to nitrogen to achieve water denitrification. In addition, the photoelectrons can be utilized by microorganisms to further accelerate the denitrification effect of microorganisms and improve the denitrification performance of the system.

[0015] 2. Fe 3+ As a bridging medium, one end is anchored on the nitrogen-containing functional group of the photocatalyst through a coordination bond, and the other end attracts the phytic acid molecule; the phytic acid molecule contains six phosphate groups and has strong chelating ability, which can chelate Fe 3+Coordination polymerization occurs on the particle surface, forming an organic mineralization network. The uncoordinated phosphate hydroxyl groups on phytic acid undergo deprotonation in the wastewater environment, which in turn makes the surface of the photocatalytic carrier negatively charged. Since most bacteria are also negatively charged, according to the principle of like charges repelling each other, the adhesion of microorganisms to the surface of the photocatalytic carrier can be effectively reduced, thus ensuring the catalytic effect of the photocatalytic carrier. Attached Figure Description

[0016] Figure 1 This is a diagram showing the connection relationships of a biological wastewater treatment system.

[0017] The main reference numerals in the figure are as follows: 1. Light-enhanced tank; 2. Anaerobic tank; 3. Anoxic tank; 4. Aerobic tank; 5. Sedimentation tank; 6. First hydrocyclone; 7. Ultrasonic cleaning pipe; 8. Second hydrocyclone; 9. Outlet pipe; 10. Sludge return pipe; 11. Sludge inlet pipe; 12. Inlet pipe; 13. Valve; 14. Flow meter; 15. Light lamp tube; 16. Mixed liquor return pipe; 17. Overpass pipe; 18. Direct discharge pipe; 19. Sludge discharge pipe. Detailed Implementation

[0018] Example 1: This example provides a highly efficient enhanced biological wastewater treatment system, such as... Figure 1 As shown, it includes a light-enhancing tank 1, an anaerobic tank 2, an anoxic tank 3, an aerobic tank 4, a sedimentation tank 5, a first hydrocyclone 6, an ultrasonic cleaning tube 7, and a second hydrocyclone 8.

[0019] The photointensification tank 1, anaerobic tank 2, anoxic tank 3, and aerobic tank 4 are connected in sequence, and each tank contains activated sludge and photocatalytic carrier. The sedimentation tank 5 is connected to the aerobic tank 4 and is used to separate the sludge from the treated water. The water in the sedimentation tank 5 is discharged through the effluent pipe 9, and part of the settled activated sludge and photocatalytic carrier is returned to the photointensification tank 1 and / or the anaerobic tank 2 through the sludge return pipe 10.

[0020] The first hydrocyclone 6 is connected to the sedimentation tank 5 via the sludge inlet pipe 11 and is used to separate activated sludge and photocatalytic carrier; the ultrasonic cleaning pipe 7 is connected to the first hydrocyclone 6 and is used to remove the biofilm on the surface of the photocatalytic carrier; the second hydrocyclone 8 is connected to the ultrasonic cleaning pipe 7 and is used to separate the photocatalytic carrier and biofilm, and the separated photocatalytic carrier is returned to the photo-enhancing tank 1 and / or the anaerobic tank 2.

[0021] Wastewater enters the photointensification tank 1 and / or the anaerobic tank 2 through the inlet pipe 12. A valve 13 controls the inflow into the photointensification tank 1 and the anaerobic tank 2, and a flow meter 14 is installed on the inlet pipe 12 to detect the flow rate. The proportion of inflow to the photointensification tank 1 and the anaerobic tank 2 can be allocated by adjusting the opening of the valve 13 on the inlet pipe 12. When the biodegradability of the influent is good, the valve 13 on the wastewater inlet pipe to the photointensification tank 1 can be closed, and the sludge return from the sedimentation tank 5 to the photointensification tank 1 can be stopped, thus stopping the operation of the photointensification tank 1 and reducing operating costs. Conversely, when the biodegradability of the influent is poor, the valve 13 on the wastewater inlet pipe to the anaerobic tank 2 can be closed, and the sludge return from the sedimentation tank 5 to the anaerobic tank 2 can be stopped, allowing the wastewater and activated sludge to directly enter the photointensification tank 1.

[0022] Meanwhile, multiple light-emitting tubes 15 are arranged in the light-enhancing tank 1 to activate the photocatalytic carrier and ensure the supply of light source when sunlight is insufficient. After the recalcitrant wastewater flows into the tank, the photocatalytic carrier plays its role in decomposing the recalcitrant pollutants into smaller molecules through photocatalytic reactions, thereby improving the biodegradability of the wastewater. At the same time, activated sludge plays a synergistic role, further decomposing the photocatalytic products. A flow booster is also arranged at the bottom of the light-enhancing tank 1 to ensure that the photocatalytic carrier and activated sludge are evenly distributed in the tank. The dissolved oxygen in the light-enhancing tank 1 is maintained in an anoxic state.

[0023] A mixed liquor return pipe 16 is also installed on the aerobic tank 4, which is connected to the photointensification tank 1 and the anoxic tank 3. This pipe is used to return the wastewater, activated sludge, and photocatalytic carrier mixture from the aerobic tank 4 to the photointensification tank 1 and / or the anoxic tank 3. The mixed liquor return pipe 16 is also equipped with a valve 13 to control the mixed liquor return and a flow meter 14 to control the return flow rate. Adjusting the opening of valve 13 allows for adjustment of the proportion of mixed liquor returned to the photointensification tank 1 and the anoxic tank 3. When the total nitrogen in the effluent from the aerobic tank 4 is high (greater than 10 mg / L), a portion of the mixed liquor can be returned to the photointensification tank 1 to enhance the overall denitrification effect of the system.

[0024] A bypass pipe 17 is also installed between the sedimentation tank 5 and the ultrasonic cleaning pipe 7. Part of the settled activated sludge and photocatalytic carrier in the sedimentation tank 5 enters the ultrasonic cleaning pipe 7 through the bypass pipe 17 for ultrasonic treatment. A valve 13 and a flow meter 14 are also installed on the bypass pipe 17, allowing the sludge and photocatalytic carrier to bypass the first hydrocyclone 6 and directly reach the ultrasonic cleaning pipe 7. A direct discharge pipe 18 is also installed at the outlet of the ultrasonic cleaning pipe 7. The direct discharge pipe 18 is connected to the photoenhancing tank 1 and / or the anaerobic tank 2 (the direct discharge pipe 18 is connected to the photocatalytic carrier discharge line of the second hydrocyclone 8 (used to return the photocatalytic carrier to the photoenhancing tank 1 and / or the anaerobic tank 2; in actual application, a valve is installed on the discharge line at the bottom of the second hydrocyclone 8) to directly return the photocatalytic carrier to the photoenhancing tank 1 and / or the anaerobic tank 2).

[0025] After the system has been running for a long time, a certain amount of biofilm will inevitably form on the surface of the photocatalytic carrier. When the biofilm on the surface of the photocatalytic carrier is detected to exceed a certain thickness and affect the photocatalytic effect (this can also be judged by the effluent), but there is no need to discharge sludge, it is necessary to enhance the ultrasonic cleaning of the biofilm on the carrier surface. This can be done by closing valve 13 on the pipe connecting sedimentation tank 5 and the first hydrocyclone 6, closing the valve between ultrasonic cleaning pipe 7 and the second hydrocyclone 8, closing the valve at the bottom of the second hydrocyclone 8, and opening valve 13 on the bypass pipe 17 and valve 13 on the direct discharge pipe 18. This allows the sludge and photocatalytic carrier in sedimentation tank 5 to enter the ultrasonic cleaning pipe 7 directly at a larger flow rate for cleaning, and then directly return to the photoenhancing tank 1 and / or anaerobic tank 2 through the direct discharge pipe 18.

[0026] The sludge and biofilm separated in the first hydrocyclone 6 and the second hydrocyclone 8 are discharged from the system through the top sludge discharge pipe 19.

[0027] In the above scheme, materials that need to be transported by moving equipment can be transported by installing pumps on the corresponding pipelines; and the pipelines are equipped with corresponding flow meters and regulating valves as needed.

[0028] Example 2: This example provides a method for preparing a photocatalytic support for the treatment system in Example 1, comprising the following steps: 100g of diatomaceous earth (particle size 30-80μm, porosity ≥80%) was mixed with 150g of melamine and placed in a ball mill jar. The mixture was then dry-milled for 8 hours (500rpm, ball-to-material mass ratio 10:1). The mixed powder was then placed in a crucible and calcined in a muffle furnace at 550℃ under a nitrogen atmosphere for 4 hours. After cooling, the powder was ground through a 200-mesh sieve to obtain catalytic particles.

[0029] Prepare a 0.2 mol / L iron ion solution and a 1 wt% phytic acid solution (pH adjusted to 3) using 5 g FeCl3·6H2O, 10 g phytic acid, and water, respectively. Then, immerse 100 g of catalyst particles in the iron ion solution and stir at 200 rpm for 10 min. After filtration, rinse quickly with deionized water (10 s), and then immerse the catalyst particles in the phytic acid solution for 20 min. After filtration, wash three times alternately with ethanol and water, and then vacuum dry at 60℃ to constant weight before use.

[0030] Comparative Example 1: It is basically the same as Example 2, except that the catalyst particles were directly applied to the system in Example 1 after preparation.

[0031] Comparative Example 2: It is basically the same as Example 2, except that the catalyst particles are directly immersed in phytic acid solution, but are not immersed in iron ion solution beforehand.

[0032] Sludge from the aerobic tank of the municipal wastewater treatment plant was inoculated into three small-scale reactors consisting of an anaerobic tank, an anoxic tank, and an aerobic tank. The initial sludge concentration in each tank was maintained at 2600±25 mg / L. Photocatalytic carriers prepared in Example 2, Comparative Example 1, and Comparative Example 2 were taken into the tanks at a ratio of 3‰ of the volume of each tank. The hydraulic retention time was set to 8 hours to ensure sufficient nutrients in the biological tank.

[0033] The test water was the influent from a municipal wastewater treatment plant in Nanjing. The specific influent water quality was: COD concentration (303.29±99.7) mg / L, TN concentration (34.98±6.49) mg / L, and NH4+ concentration... + -N concentration (21.91±9.57) mg / L, TP concentration (3.3±0.62) mg / L. This process maintains normal A 2 After 15 days of continuous reaction under the O process without sludge discharge, equal volumes of sludge from three separate tanks were mixed and ultrasonically treated to separate the photocatalytic carrier from the sludge. The ultrasonically treated mixture was then fed into a hydrocyclone. The heavier photocatalytic carrier flowed out from the lower outlet of the hydrocyclone, while the suspended sludge and detached biofilm flowed out from the upper outlet. Sludge from the upper outlet of the hydrocyclone was collected for sludge concentration testing; higher sludge concentration indicated a higher amount of biofilm originally loaded on the photocatalytic carrier. The sludge concentration measurements showed: Comparative Example 1 (5872 mg / L) > Comparative Example 2 (5523 mg / L) > Example 2 (4764 mg / L), indicating that the photocatalytic carrier modification measure using iron ions to introduce phytic acid in Example 2 effectively inhibited biofilm growth on the surface of the photocatalytic carrier.

Claims

1. A highly efficient enhanced biological wastewater treatment system, characterized in that, include: The light-enhancing tank, anaerobic tank, anoxic tank, and aerobic tank are connected in sequence, and each tank contains activated sludge and photocatalytic carrier. The sedimentation tank, connected to the aerobic tank, is used to separate the sludge from the treated water and to return some of the settled activated sludge and photocatalytic carrier to the photo-enhancing tank and / or anaerobic tank. The first hydrocyclone, connected to the sedimentation tank, is used to separate activated sludge and photocatalytic carrier; The ultrasonic cleaning tube, connected to the first hydrocyclone, is used to remove the biofilm from the surface of the photocatalytic carrier. The second hydrocyclone, connected to the ultrasonic cleaning tube, is used to separate the photocatalytic carrier and the biofilm. The separated photocatalytic carrier is returned to the photo-enhancing tank and / or the anaerobic tank.

2. The high-efficiency enhanced biological wastewater treatment system according to claim 1, characterized in that, The photocatalytic carrier is prepared by mixing diatomaceous earth and melamine, ball milling and calcining to obtain catalytic particles; then the catalytic particles are successively immersed in iron ion solution and phytic acid solution, and then washed and dried.

3. The high-efficiency enhanced biological wastewater treatment system according to claim 2, characterized in that, The mass ratio of diatomaceous earth to melamine is 1:(1.2-1.5); The calcination conditions are as follows: under a nitrogen atmosphere, the temperature is increased to 500-600℃ at a rate of 3-5℃ / min, and held for 3-5 hours.

4. The high-efficiency enhanced biological wastewater treatment system according to claim 2, characterized in that, In the iron ion solution, the iron ions are derived from ferric chloride hexahydrate, and the concentration is 0.2-0.3 mol / L; the concentration of the phytic acid solution is 1-2 wt%. The mass ratio of the catalyst particles to ferric chloride hexahydrate and phytic acid is 1:(0.03-0.1):(0.1-0.2).

5. The high-efficiency enhanced biological wastewater treatment system according to claim 2, characterized in that, The catalytic particles were soaked in iron ion solution for 10-15 minutes and in phytic acid solution for 15-25 minutes.

6. The high-efficiency enhanced biological wastewater treatment system according to claim 1, characterized in that, Wastewater enters through the inlet pipe, which is connected to the photointensification tank and the anaerobic tank.

7. The high-efficiency enhanced biological wastewater treatment system according to claim 1, characterized in that, A mixed liquor return pipe is installed on the aerobic tank, which is connected to the photointensification tank and the anoxic tank. It is used to return the wastewater, activated sludge and photocatalytic carrier mixture in the aerobic tank to the photointensification tank and / or the anoxic tank.

8. The high-efficiency enhanced biological wastewater treatment system according to claim 1, characterized in that, The light-enhancing pool is also equipped with light-emitting tubes and a flow booster.

9. The high-efficiency enhanced biological wastewater treatment system according to claim 1, characterized in that, An overpass pipe is also installed between the sedimentation tank and the ultrasonic cleaning pipe. Some of the settled activated sludge and photocatalytic carrier in the sedimentation tank enter the ultrasonic cleaning pipe through the overpass pipe for ultrasonic treatment.

10. The high-efficiency enhanced biological wastewater treatment system according to claim 9, characterized in that, A direct discharge pipe is also installed at the outlet of the ultrasonic cleaning pipe, which is connected to the light-enhancing tank and / or anaerobic tank.

Images