CN104528934A - Shortcut nitrification-denitrification membrane bioreactor and sewage treatment technology thereof - Google Patents

Abstract

The invention discloses a short-range nitrification-denitrification denitrification membrane bioreactor and its sewage treatment process. The short-range nitrification-denitrification denitrification membrane bioreactor includes a denitrification reaction pool and a membrane module. The denitrification reaction pool Divided into multi-stage series reaction chambers, each stage of reaction chamber is divided into anoxic zone and facultative oxygen zone by folded plate wall, and the top and bottom of both are connected; adjacent two-stage reaction chambers are separated by perforated walls , the aperture of the through hole on the perforated wall gradually becomes smaller along the water flow direction; the membrane module is arranged in the aerobic zone of the final reaction chamber, and the short-path nitrification-denitrification denitrification membrane bioreactor also includes The water distribution system for supplying water to the anaerobic zone of the chamber and the aeration device for ventilation to the bottom of the anaerobic zone of each reaction chamber. The reactor can realize the denitrification process of the internal circulation flow of the sewage inside the reactor, and improve the denitrification treatment effect of the sewage.

Description

Short-cut nitrification-denitrification denitrification membrane bioreactor and its sewage treatment process

technical field

The invention relates to a biological denitrification device, which belongs to the field of sewage treatment, in particular to a short-range nitrification-denitrification denitrification membrane bioreactor and a sewage treatment process thereof.

Background technique

Eutrophication of water body refers to that after a large amount of nitrogen, phosphorus and other elements are discharged into the water body, it promotes the growth and reproduction of algae and other aquatic organisms, making the rate of organic matter production far exceed the speed of water body consumption, resulting in the accumulation of organic matter in the water body and destroying the aquatic ecological balance. . Common and more serious manifestations of eutrophication in water bodies include: "algae blooms" and "red tides" in water bodies. Eutrophication of water bodies will pollute water resources and seriously affect human's daily life. However, most of the eutrophication of water bodies is caused by the enrichment of nitrogen, phosphorus and other elements in water bodies during human activities. Therefore, in order to prevent eutrophication of water bodies, the pollutants rich in nitrogen, phosphorus and other external nutrients input into water bodies due to human activities should be reduced or cut off first.

In recent years, a large number of sewage treatment facilities have been built on a large scale, and biological denitrification processes have also been adopted. The purpose is to reduce the pollutants rich in nitrogen, phosphorus and other external nutrients input into water bodies due to human activities. To prevent water pollution. Traditional biological nitrogen removal processes include A ² /O, A/O, oxidation ditch, SBR and its variants, UCT, etc. The basic principle is to convert organic nitrogen into ammonia nitrogen (NH ₄ ⁺ -N), first The synergistic effect of nitrifying bacteria and nitrosifying bacteria in the aerobic section is used to convert ammonia nitrogen into nitrite nitrogen (N-NO ₂ ^- ) and nitrate nitrogen (N-NO ₃ ^- ) through nitrification. Then, N-NO ₂ ^- and N-NO ₃ ^- are converted into nitrogen (N ₂ ) through denitrification under anoxic conditions, which overflow the water surface and release to the atmosphere, participating in the cycle of nitrogen in nature. Reduce the nitrogen content in water, reduce the potential danger of effluent, and achieve the purpose of reducing nitrogen in water.

Denitrifying bacteria are heterotrophic facultative anaerobic bacteria, which use NO _x -N as electron acceptor and organic matter as electron donor under anaerobic conditions. Carbon source is an indispensable substance in the denitrification process, and the C/N of the influent directly affects the effect of biological nitrogen and nitrogen removal. When the influent C/N is lower than 3.4, the traditional biological denitrification process will face the problem of insufficient carbon source and cannot realize biological denitrification. Carbon source measures will cause a significant increase in sewage treatment costs. Moreover, the C/N of aquaculture wastewater, landfill leachate, chemical wastewater and some urban domestic sewage is far lower than this value, and the traditional biological denitrification process will be difficult to achieve the purpose of denitrification. In addition, A ² /O, A/O, oxidation ditch, SBR and its variants, UCT and other traditional biological denitrification process framework combinations contain multiple sludge and mixed liquor reflux, which increases the complexity of the system and improves infrastructure construction. and operating costs; the denitrification process consumes a lot of energy, which does not meet the requirements of low-carbon sustainable development of the environment.

Therefore, in view of the widely existing high ammonia nitrogen concentration and low C/N wastewater such as aquaculture wastewater, landfill leachate, and chemical wastewater, a low-cost, sustainable and efficient denitrification reactor should be developed to improve the removal effect of biological denitrification. Reducing processing costs will be more in line with the trend of low-carbon and sustainable development of the environment.

The patent application with the authorized announcement number CN101863586B discloses a membrane bioreactor for denitrification and its sewage denitrification method. The membrane bioreactor includes a reaction tank, a membrane module in the reaction tank and a water outlet connected to the membrane module. A water inlet and a reflux inlet are respectively provided at the bottom of the reaction tank, and the membrane bioreactor is divided into five small pools connected in series by four vertical guide baffles, and the water inlet is connected with the first anoxic tank; An anoxic tank communicates with the aerobic tank through the baffle outlet at the upper end, and a first aeration device is installed at the bottom of the aerobic tank; the aerobic tank communicates with the second anoxic tank through the baffle outlet at the lower end; the second anoxic tank The pool communicates with the anaerobic pool through the baffle outlet at the upper end; finally, the anaerobic pool communicates with the membrane pool through the baffle outlet at the lower end, and a second aeration device is installed at the bottom of the membrane pool; there are vertically placed membrane modules in the membrane pool, And there is a water outlet connected to the membrane pool; the bottom of the membrane pool is also provided with a sludge discharge port, which is connected to the sludge pump; the top of the membrane pool is also provided with a reflux liquid outlet, which is connected to the first anoxic pool through the reflux pump The reflux liquid inlet at the bottom; among them, the volume ratio of the five small tanks connected in series is 1:1:1:1:1~3, and the ratio of the aeration volume of the first aeration device to the volume of the aerobic tank is 2-4.5h ^-1 , the ratio of the aeration rate of the second aeration device to the volume of the membrane tank is 3-7h ^-1 .

Although the membrane bioreactor can achieve deep denitrification treatment, which can reduce membrane pollution, and utilize the high-efficiency interception and separation characteristics of the membrane, the water quality of the filtered water is good; however, the sewage denitrification treatment process of the membrane bioreactor is too short, and Sewage flows in one direction in the membrane bioreactor, which can easily lead to insufficient denitrification treatment of sewage and poor sewage treatment effect, especially for wastewater with high ammonia nitrogen concentration and low C/N such as aquaculture wastewater, landfill leachate, and chemical wastewater. The processing effect needs to be improved.

Contents of the invention

The invention provides a short-range nitrification-denitrification denitrification membrane bioreactor and its sewage treatment process. The reactor can realize the denitrification process of the sewage inside the reactor through internal circulation flow, and improve the denitrification treatment effect of the sewage.

A short-range nitrification-denitrification denitrification membrane bioreactor, including a denitrification reaction pool and a membrane module, the denitrification reaction pool is divided into multi-stage series reaction chambers, and the inside of each stage reaction chamber is divided into gaps by folded plate walls. Oxygen zone and facultative oxygen zone, and the top and bottom of the two are connected; the adjacent two reaction chambers are separated by a perforated wall, and the aperture of the through hole on the perforated wall gradually becomes smaller along the water flow direction; the membrane module is located in In the aerobic zone of the final reaction chamber, the short-path nitrification-denitrification denitrification membrane bioreactor also includes a water distribution device for supplying water to the anaerobic zone of each reaction chamber and the bottom of the aerobic zone of each reaction chamber. Ventilated aerators.

The anoxic zone is provided with a biological selector, through which the microorganisms are selectively cultivated to prevent sludge bulking during the sewage treatment process, thereby affecting the internal circulation of the mixed liquid of sewage and activated sludge in the reaction chamber.

During the aeration process in the aerobic zone, the compressed air is released from the aeration device into the aerobic zone, and due to the propulsion of the gas and the entrainment and mixing of the compressed air in the water, the density of the mixture of water and air decreases and becomes It flows upwards and reaches the liquid surface in the process of turning over the folded plate wall. At this time, the gas and liquid are separated, the bubbles escape from the water surface, and the liquid turns over the folded plate wall and enters the biological selector in the anoxic zone and enters from the water distribution device. The sewage is mixed to continue the sewage denitrification treatment process. Since the anoxic zone is not connected with the aeration device, the mixture of sewage and activated sludge sinks due to the increase in relative density and re-enters the aerobic zone. Therefore, the mixed solution of sewage and activated sludge flows upward in the anoxic zone and flows downward in the anoxic zone, forming an unpowered internal circulation system, in which the density difference between the anoxic zone and the anoxic zone is With the internal power of circulation, the mixed liquid can alternately circulate in the anoxic zone and the anoxic zone, thereby improving the effect of sewage treatment.

The bottom of the folded plate wall is provided with a folded plate that folds towards the aerobic tank. The bottom of the anoxic zone is provided with an oblique diversion slope on the side away from the anoxic zone. The setting of the folding plate and the diversion slope can play the role of sewage diversion, avoiding part of sewage accumulation in the area where the anoxic zone and the anoxic zone are connected at the bottom of the reaction chamber, thereby affecting the smooth progress of the internal circulation system.

A height-adjustable weir plate is arranged on the top of the folded plate wall. The weir plate can move up and down on the folded plate wall. When the weir plate moves to the highest position, it is higher than the folded plate wall and has the same height as the liquid level. The top flows into the anoxic zone, so that the denitrification effect of the internal circulation denitrification system inside the reaction chamber is better.

Due to the difference in density between gas and liquid, the liquid will move downward under the action of gravity, while the gas will move upward. The upward gas will adhere to the wall of the variable-diameter hole, move along the direction of the enlarged hole diameter, and return to the facultative oxygen zone. Inside, the gas return ratio is greater than 100%, so that the gas in the aerobic pool area will not enter the anoxic area of the next level along with the liquid along the perforated wall. Preferably, the angle between the through hole of the perforated wall and the horizontal direction is 30-60°, and the water inlet end of the through hole is higher than the outlet end.

The anaerobic area of the first-stage reaction chamber is provided with a mud return port, and the anaerobic area of the last-stage reaction chamber is provided with a mud discharge port. The short-range nitrification-denitrification denitrification membrane bioreactor of the present invention, in addition to including the denitrification reaction tank, membrane module, water distribution device and aeration device, is also provided with a sludge return device and a sludge discharge device; the sludge The inlet end of the reflux device is connected with the anaerobic area of the final reaction chamber, and the outlet end is connected with the anoxic area of the first-stage reaction chamber; one end of the sludge discharge device is connected with the anaerobic area of the final reaction chamber.

The present invention also provides a sewage treatment process of the short-range nitrification-denitrification denitrification membrane bioreactor. The sewage is fed into the anoxic zone of the reaction chambers at all levels through the water distribution system, and the aeration system is used in the facultative oxygen zone. Bottom aeration allows the sewage to undergo cyclic denitrification in the anoxic zone and the facultative zone. After the denitrification treatment is completed, the sewage flows out after being filtered by the membrane bioreactor.

Preferably, the hydraulic retention time in the anoxic zone is controlled to be 0.5-3.0 h, and the hydraulic retention time in the facultative oxygen zone is 1.0-5.0 h.

The traditional whole-process nitrification-denitrification biological denitrification pathway is:

NH ₄ ⁺ -N→NO ₂ ^- -N→NO ₃ ^- -N→NO ₂ ^- -N→N ₂

The short-cut nitrification-denitrification biological nitrogen removal pathway is:

NH ₄ ⁺ -N→NO ₂ ^- -N→N ₂

Compared with the traditional whole-process nitrification-denitrification biological denitrification approach, the short-cut nitrification-denitrification approach adopted by the present invention saves the oxygen consumption of NO ₂ ^- -N→NO ₃ ^- -N, and the oxygen supply can be saved up to 25 % or more, it can also save 40% of carbon source in the denitrification process and save operating costs.

In order to facilitate the occurrence of the short-range nitrification-denitrification process, preferably, the dissolved oxygen concentration in the anoxic zone is less than 1.5mg/L, and the dissolved oxygen concentration in the anoxic zone is less than 0.5mg/L, and the free ammonia in the anoxic zone The concentration is 9~300mg/L, and the pH value is 7.0-9.0. By controlling the aeration rate and the height of the weir plate, the dissolved oxygen concentration in the anoxic zone and the facultative zone can be adjusted to meet the above requirements. By controlling the opening degree of the valve of the water distribution branch line, the influent flow in the anoxic zone can be adjusted, so that the concentration of free ammonia in the anoxic zone can be controlled within the above range, and the concentration of the free ammonia is greater than the transformation effect of nitrite oxidizing bacteria The threshold value is lower than the threshold value of ammonia oxidizing bacteria transformation and utilization, which can ensure that the denitrification process in the reactor of the present invention is a short-range nitrification-denitrification biological denitrification pathway.

In addition to controlling the concentration of dissolved oxygen and free ammonia in the reactor, the pH value of the reactor should also be controlled within the range of 7.0 to 9.0, and the flow rate of sewage flowing through the through holes on the perforated wall should be controlled by changing the size of the through holes. 3 ~ 10m/min, make the ammonia oxidizing bacteria in the reactor become the dominant bacterial group, realize the accumulation of NO ₂ ^- -N, and ensure that the denitrification process is a short-range nitrification-denitrification biological denitrification pathway.

In the present invention, the dissolved oxygen concentration, the free ammonia concentration and the pH value of the liquid in the reactor are all measured by conventional measurement means.

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

(1) The present invention divides the short-range nitrification-denitrification denitrification membrane bioreactor into a multi-stage anoxic zone and anoxic zone alternately connected reactors through the setting of the folded plate wall and the perforated wall. Aeration is introduced into the zone, sewage is introduced into the anoxic zone, and the density difference of the mixed liquid is used to realize the process of circulating denitrification in the anoxic zone and the facultative oxygen zone in the whole reactor, so that the sewage in the reactor of the present invention The denitrification process in the plant is extended, the denitrification effect is improved, and the final effluent water quality is better;

(2) In the present invention, a biological selector is set in the anoxic zone, so that the ammonia oxidizing bacteria in the reactor become the dominant flora, which can not only realize the short-range nitrification-denitrification denitrification process, but also treat waste water with high ammonia nitrogen and low C/N. The expansion problem of the activated sludge during the denitrification treatment process is avoided, and the smooth circulation of the activated sludge in the reactor internal circulation denitrification system of the present invention is ensured.

Description of drawings

Fig. 1 is the structural side view of short-range nitrification-denitrification denitrification membrane bioreactor of the present invention;

Fig. 2 is the plane top view of short-range nitrification-denitrification denitrification membrane bioreactor of the present invention;

1. Water distribution branch line; 2. Regulating valve; 3. First-level anoxic zone; 4. First-level anaerobic zone; 5. Folded plate wall; 6. Folded plate; 7. Weir plate; 8. Diversion slope; 9 , perforated wall; 10, secondary anoxic area; 11, secondary anoxic area; 12, fifth anoxic area; 13, fifth anoxic area; 14, membrane module; 15, aeration device; 16, supply 17. Sludge return device; 18. Sludge discharge device; 19. Sludge discharge device. the

Detailed ways

The short-cut nitrification-denitrification denitrification membrane bioreactor of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figures 1 and 2, a short-range nitrification-denitrification denitrification membrane bioreactor consists of a water distribution device, a denitrification reaction tank, a membrane module 14, an aeration device 15, a sludge return device 17 and a sludge discharge device 18 compositions.

The denitrification reaction pool is divided into five levels of reaction chambers, each of which is connected in turn and separated by a perforated wall 9, and the interior of each level of reaction chamber is divided into an anoxic zone and a facultative oxygen zone by a folded wall 5, and 3 in the figure is The first-level anoxic zone, 4 is the first-level facultative oxygen zone. The first-level anoxic zone is set as a biological selection zone, and the bottom of the anoxic zone is provided with a diversion slope 8 arranged obliquely, and the diversion surface of the diversion slope 8 faces the folded plate wall 5 . The top of the folded plate wall 5 is below the liquid level, and the bottom is provided with a folded plate 6 that folds toward the aerobic zone. The folded plate 6 maintains an angle of 60° with the horizontal surface of the bottom of the reaction tank, and the horizontal width is 30 cm. The top of the folded plate wall 5 is provided with a weir plate 7, which can adjust the flow rate of the mixed liquid flowing through the weir plate 7 from the top of the aerobic zone into the anoxic zone by controlling the height of the weir plate 7; Aeration devices 15 are provided at the bottom of the zone; membrane modules 14 are set in the fifth-level aerobic zone 13 of the fifth-level reaction chamber. The angle between the through hole of the perforated wall 9 and the horizontal direction is 30-60°, and the water inlet end of the through hole is higher than the outlet end.

During the aeration process in the aerobic zone, the compressed air is released from the aeration device into the aerobic zone, and due to the propulsion of the gas and the entrainment and mixing of the compressed air in the water, the density of the mixture of water and air decreases and becomes It flows upwards and reaches the liquid surface in the process of turning over the weir plate. At this time, the gas and liquid are separated, and the air bubbles escape from the water surface, while the liquid turns over the weir plate and enters the biological selector in the anoxic zone and the sewage entering from the water distribution device Mix and continue with the sewage treatment process. Since the anoxic zone is not connected to the non-aeration device, the mixture of sewage and activated sludge sinks due to the increase in relative density and re-enters the facultative zone. Therefore, the mixed solution of sewage and activated sludge flows upward in the facultative zone and downward in the anoxic zone, forming an unpowered internal circulation system.

Application example 1

The existing process of leachate treatment in a waste incineration power plant is "adjustment tank + primary sedimentation tank + upflow anaerobic composite bed + oxidation ditch + MBR" process, the design treatment scale is 600m ³ /d, and the actual treatment capacity is 400-500m ³ /d, see Table 1 for the quality of influent and effluent water.

In order to improve the denitrification effect, the pilot plant of the short-cut nitrification-denitrification denitrification membrane bioreactor of the present invention is used for leachate treatment of a waste incineration power plant, and the treatment flow rate of the pilot plant is 24m ³ /d.

In the start-up process of the short-range nitrification-denitrification denitrification membrane bioreactor, first inject 1/10 of the landfill leachate into the primary reaction chamber of the short-range nitrification-denitrification denitrification membrane bioreactor, and then inject clean water to the ground , inoculate activated sludge with good nitrification activity, aerate the facultative oxygen zone through the aeration device, and start the sludge return device, adjust the weir plate 7 to a height lower than the folded plate wall, and continuously aerate until the ammonia nitrogen concentration is 10 After ~30mg/L, start water continuous operation. The distribution ratios of sewage flow from the first-stage reaction chamber to the fifth-stage reaction chamber are 30%, 25%, 20%, 15% and 10% respectively. The effective water depth in the anoxic zone and the anoxic zone is 4.5m, and the hydraulic retention time in the anoxic zone is controlled at 0.5-3.0h, and the hydraulic retention time in the anoxic zone is controlled at 1.0-5.0h. Adjust the aeration rate so that the dissolved oxygen concentration in the anoxic tank DO<1.5mg/L, adjust the height of the weir plate, change the distribution ratio of the mixed solution in the anoxic zone and the facultative zone, and make the dissolved oxygen concentration DO in the anoxic zone <0.5mg/L. Adjust the aperture of the through hole so that the flow rate of the sewage flowing through the through hole on the perforated wall is 3-10m/min, and the aperture of the through hole is DN150.

The water quality of the short-range nitrification-denitrification denitrification membrane bioreactor and the effluent of the landfill leachate plant were measured respectively, and the results are as follows:

Table 1:

As can be seen from the above results, the effluent quality of the short-path nitrification-denitrification denitrification membrane bioreactor of the present invention is obviously better than the effluent at the oxidation ditch of the conventional landfill leachate treatment plant, and the effluent quality of the short-path nitrification-denitrification denitrification membrane bioreactor The TN and COD _Cr indexes are obviously better than those of the oxidation ditch process effluent of the landfill leachate treatment plant, and the TP removal effect is also better.

Claims (10)

1. a short-cut nitrification-denitrification denitrogenation membrane bioreactor, comprise denitrification reaction pond, membrane module, it is characterized in that, described denitrification reaction pond is divided into the reaction chamber of plural serial stage, every order reaction chamber interior is divided into oxygen-starved area and aerobic area by flap wall, and both tops are all connected with bottom; Separated by perforated wall between adjacent two-stage reaction room, the through hole on perforated wall diminishes gradually along water (flow) direction aperture; Described membrane module is located in the aerobic area of final stage reaction chamber, and described short-cut nitrification-denitrification denitrogenation membrane bioreactor also comprises the aerating apparatus of the water distribution system that supplies water the anaerobic zone toward every order reaction room and the aerobic area bottom ventilation toward every order reaction room.

2. short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 1, it is characterized in that, the bottom of described flap wall is provided with the flap being folded to oxygen compatibility pool.

3. short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 1, it is characterized in that, described flap coping is provided with adjustable for height weir plate.

4. short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 1, it is characterized in that, the bottom of described oxygen-starved area is provided with the water conservancy diversion slope be obliquely installed away from side, aerobic area.

5. short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 1, it is characterized in that, the through hole of described perforated wall and the angle of horizontal direction are 30 ~ 60 °, and the water inlet inlet end of through hole is higher than exit end.

6. short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 1, it is characterized in that, the anaerobic zone of first step reaction chamber is provided with mud return mouth, and the aerobic area of last step reaction chamber is provided with mud discharging mouth.

7. the sewage treatment process of the short-cut nitrification-denitrification denitrogenation membrane bioreactor as described in any one of claim 1 ~ 6, it is characterized in that, sewage is passed into the oxygen-starved area of reaction chamber at different levels by water distribution system, by aerating apparatus aeration bottom aerobic area, sewage is made to carry out cycling denitrification in oxygen-starved area and aerobic area, after denitrogenation processing terminates, sewage flows out after membrane bioreactor filters.

8. the sewage treatment process of short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 7, is characterized in that, the hydraulic detention time controlling oxygen-starved area is 0.5 ~ 3.0h, and the hydraulic detention time of aerobic area is 1.0 ~ 5.0h.

9. the sewage treatment process of short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 8, it is characterized in that, the dissolved oxygen concentration of aerobic area is less than 1.5mg/L, the dissolved oxygen concentration of oxygen-starved area is less than 0.5mg/L, in described oxygen-starved area, the concentration of free ammonia is 9 ~ 300mg/L, and pH value is 7.0-9.0.

10. the sewage treatment process of short-cut nitrification-denitrification denitrogenation membrane bioreactor as claimed in claim 7, is characterized in that, the flow velocity controlling through hole on effluent stream perforated wall is 3 ~ 10m/min.