Anaerobic ammonia oxidation denitrification process using an anaerobic membrane reactor

Abstract

This invention relates to the field of wastewater treatment technology and discloses an anaerobic ammonia oxidation denitrification process using an anaerobic membrane reactor. The process includes an A / O reaction unit and an upflow anaerobic membrane treatment unit. The A / O reaction unit treats wastewater to obtain ammonia-nitrogen-containing wastewater from section A and nitrite-nitrogen-containing wastewater from section O. These two wastewaters are then mixed and used as the influent to the upflow anaerobic membrane treatment unit. The upflow anaerobic membrane treatment unit includes a reactor, a sludge settling zone at the bottom of the reactor, a membrane module in the middle of the reactor, and a gas storage chamber at the top of the reactor. The influent is filtered through the membrane module to obtain treated effluent. This anaerobic ammonia oxidation denitrification process effectively intercepts anaerobic ammonia-oxidizing bacteria, enabling rapid start-up of the anaerobic ammonia oxidation process. By mixing the ammonia-nitrogen-rich section A effluent from the A / O reaction unit with the nitrate- and nitrite-nitrogen-rich section O effluent as the influent to the anaerobic membrane treatment unit, the removal of total nitrogen during the start-up of the anaerobic ammonia oxidation process is enhanced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an anaerobic ammonia oxidation denitrification process using an anaerobic membrane reactor. Background Technology

[0002] Compared to traditional nitrification-denitrification nitrogen removal technologies (application number CN201310472118.X: A Short-Cut Nitrification-Denitrification Nitrogen Removal Technology Control Method), which have low volumetric loading, high aeration energy consumption, large carbon source dosage, and large sludge production, anammox has a high loading rate but produces less sludge due to its autotrophic nature. Anammox bacteria use nitrite as an oxidant to oxidize ammonia to nitrogen or use ammonia as an electron donor to reduce nitrite to nitrogen, requiring no additional carbon source and using nitrite as a substrate, theoretically saving 58% of oxygen consumption. Therefore, this nitrogen removal process can significantly reduce operating costs. However, the difficulty in enriching anammox bacteria, long process start-up time, insufficient total nitrogen treatment capacity during start-up, and the need for further removal of a small amount of nitrate nitrogen in the anammox reaction products are important factors hindering the widespread adoption of anammox technology. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide an anaerobic ammonia oxidation (ANO) denitrification process using an anaerobic membrane reactor. This process employs an A / O reaction unit combined with an upflow anaerobic membrane treatment unit to accelerate the start-up of ANO. The influent to the anaerobic membrane treatment unit is a mixture of the ammonia-rich A-stage effluent from the A / O reaction unit and the nitrate- and nitrite-rich O-stage effluent, thus enhancing total nitrogen removal during the ANO start-up process. The A / O reaction unit utilizes partial aeration, dissolved oxygen limitation, and sludge age control strategies to achieve nitrification.

[0004] To achieve the above objectives, the present invention provides the following technical solution: An anaerobic ammonia oxidation denitrification process using an anaerobic membrane reactor includes an A / O reaction unit and an upflow anaerobic membrane treatment unit. The A / O reaction unit treats wastewater to obtain ammonia-nitrogen-containing wastewater from stage A and nitrite-nitrogen-containing wastewater from stage O, and the two wastewaters are mixed as the influent to the upflow anaerobic membrane treatment unit. The upflow anaerobic membrane treatment unit includes a reactor, a sludge settling zone at the bottom of the reactor, a membrane module in the middle of the reactor, and a gas storage chamber at the top of the reactor. The influent is filtered by the membrane module to obtain treated effluent.

[0005] Preferably, the A / O reaction unit includes an integrated reaction tank, which is divided into an A-section reaction unit and an O-section reaction unit. The A-section reaction unit is connected to the inlet water pipe to perform hydrolysis and acidification reaction on the wastewater. The bottom of the O-section reaction unit is equipped with a first aeration device to aerate the O-section reaction unit for nitrification reaction.

[0006] Preferably, both the A-section reaction unit and the O-section reaction unit are equipped with a liquid circulation system to input the ammonia-nitrogen-containing wastewater treated by the A-section reaction unit into the O-section reaction unit for nitrification, and to circulate the wastewater in the O-section reaction unit back to the A-section reaction unit.

[0007] Preferably, the mixing ratio of ammonia nitrogen-containing wastewater to nitrite nitrogen-containing wastewater is 1:3-5.

[0008] Preferably, the gas storage chamber is connected to a gas circulation system, which circulates the gas in the gas storage chamber into the membrane module for aeration and cleaning.

[0009] Preferably, the reactor is provided with a digester return pipeline in the middle, which returns part of the sludge and organic matter to section A of the A / O reaction unit.

[0010] Preferably, the membrane module is a hollow fiber membrane module, and a flow guide tube with four closed sides and top and bottom openings is arranged around the membrane module. A second aeration device is located at the bottom of the membrane module. The second aeration device forms a rapid upward flow inside the flow guide tube by aeration and lifting, which increases the flow velocity on the membrane surface and slows down the occurrence of membrane fouling.

[0011] Preferably, the second aeration device is connected to an annular distributor located at the bottom of the membrane module, and the gas circulation system is connected to the second aeration device so that the gas introduced by the gas circulation system and the wastewater are evenly distributed through the annular distributor and then introduced into the membrane module.

[0012] Preferably, the annular distributor includes several sets of layered annular distributors distributed along the direction of the membrane assembly. Each set of layered annular distributors consists of multiple concentric and nested distribution rings. In the layered annular distributor located in the upper layer, the vertical projection of the distribution ring is located between two adjacent distribution rings in the adjacent layered annular distributor.

[0013] Preferably, in the layered annular distribution components located in the same layer, the inner layer distribution ring is provided with several elastic inclined plates on the side facing its adjacent distribution ring. The inclined plates are fixed by torsion springs and are set towards the bottom of the reactor. The inclined plates on the outer layer distribution ring are placed above the inclined plates on the inner layer distribution ring, and the included angle between the two inclined plates is 150-175°.

[0014] High-nitrogen wastewater first enters the A-stage reaction unit of the A / O reaction unit for hydrolysis and acidification, converting large organic molecules into smaller organic molecules that are easier for microorganisms to utilize, while all organic nitrogen is converted into ammonia nitrogen. The ammonia nitrogen then undergoes partial nitrification in the O-stage reaction unit. By controlling dissolved oxygen and sludge age, the nitrification reaction is kept within the short-cut nitrification stage as much as possible.

[0015] After nitrification, the sludge mixture containing nitrite and nitrate nitrogen is mixed with the sludge mixture from the hydrolysis acidification tank, which is rich in low-molecular-weight organic matter and ammonia nitrogen, and then enters the bottom of the upflow anaerobic membrane treatment unit. The remaining sludge at the bottom of the upflow anaerobic membrane treatment unit degrades, releasing organic matter and ammonia nitrogen. The insufficient carbon source and ammonia nitrogen are supplemented by the effluent from the A-stage reaction unit.

[0016] In the upflow anaerobic membrane treatment unit, denitrifying bacteria at the bottom first utilize a carbon source to convert some nitrate nitrogen into nitrite nitrogen and then into nitrogen gas. After the carbon source is depleted, in the middle of the upflow anaerobic membrane treatment unit, the remaining nitrite nitrogen and ammonia nitrogen are converted into nitrogen gas and a small amount of nitrate nitrogen by anaerobic ammonia oxidation bacteria. Some of the nitrate nitrogen generated by the anaerobic ammonia oxidation reaction is then returned to the A-stage reaction unit to mix with the organic matter in the incoming water for denitrification.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention employs an A / O reaction unit combined with an upflow anaerobic membrane treatment unit to accelerate the start-up of anaerobic ammonia oxidation. The effluent from the A section, rich in ammonia nitrogen, and the effluent from the O section, rich in nitrate and nitrite nitrogen, are mixed as the influent to the anaerobic membrane treatment unit, thus enhancing the removal of total nitrogen during the start-up of the anaerobic ammonia oxidation process. The A / O reaction unit utilizes partial aeration, dissolved oxygen limitation, and sludge age control strategies to achieve nitrification.

[0018] Meanwhile, the upflow anaerobic membrane treatment unit can significantly increase the sludge age in the reactor. Excess sludge is degraded and releases organic matter in the anaerobic membrane reactor, which can provide an additional carbon source for denitrification. This can reduce the discharge of excess sludge, improve the problem of insufficient total nitrogen removal capacity during the start-up of the anaerobic ammonia oxidation process, and supplement the carbon source for the removal of nitrate nitrogen generated in the anaerobic ammonia oxidation reaction during the stable operation phase of anaerobic ammonia oxidation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram (I) of the anaerobic ammonia oxidation denitrification device.

[0020] Figure 2 This is a schematic diagram (II) of the anaerobic ammonia oxidation denitrification device.

[0021] Figure 3 This is a top view of the annular distributor in this anaerobic ammonia oxidation denitrification unit.

[0022] In the attached diagram: 10-A / O reaction unit, 11-integrated reaction tank, 12-A-stage reaction unit, 13-O-stage reaction unit, 20-upflow anaerobic membrane treatment unit, 21-reactor, 22-sludge settling zone, 23-membrane module, 24-gas storage chamber, 3-inlet pipe, 4-first aeration device, 5-liquid circulation system, 6-gas circulation system, 7-digester liquid return pipe, 8-second aeration device, 9-ring distributor, 91-layered ring distributor, 911-distribution ring, 912-inclined plate. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0024] An anaerobic ammonia oxidation denitrification process using an anaerobic membrane reactor includes an A / O reaction unit 10 and an upflow anaerobic membrane treatment unit 20. The A / O reaction unit 10 treats wastewater to obtain ammonia-nitrogen-containing wastewater from stage A and nitrite-nitrogen-containing wastewater from stage O, with a mixing ratio of 1:3-5. This mixture is then used as the influent to the upflow anaerobic membrane treatment unit 20. The upflow anaerobic membrane treatment unit 20 includes a reactor 21, a sludge settling zone 22 at the bottom of the reactor 21, a membrane module 23 in the middle of the reactor 21, and a gas storage chamber 24 at the top of the reactor 21. The influent is filtered through the membrane module 23 to obtain treated effluent. Simultaneously, aeration can significantly increase the shear force locally within the reactor 21, providing favorable conditions for the formation of anaerobic ammonia oxidation particles.

[0025] The A / O reaction unit 10 includes an integrated reaction tank 11, which is divided into an A-section reaction unit 12 and an O-section reaction unit 13. The A-section reaction unit 12 is connected to an inlet pipe 3 for hydrolysis and acidification of wastewater. The bottom of the O-section reaction unit 13 is equipped with a first aeration device 4 for aeration and nitrification. A liquid circulation system 5 is provided in both the A-section reaction unit 12 and the O-section reaction unit 13 to input the ammonia-nitrogen-containing wastewater treated by the A-section reaction unit 12 into the O-section reaction unit 13 for nitrification, and to circulate the wastewater in the O-section reaction unit 13 back to the A-section reaction unit 12.

[0026] The gas storage chamber 24 is connected to a gas circulation system 6, which circulates the gas in the gas storage chamber 24 into the membrane module 23 for aeration and cleaning.

[0027] The reactor 21 is equipped with a digester return pipeline 7 in the middle, which returns part of the sludge and organic matter to section A of the A / O reaction unit 10.

[0028] The membrane module 23 is a hollow fiber membrane module. A flow guide tube with four closed sides and open top and bottom is arranged around the membrane module 23. A second aeration device 8 is located at the bottom of the membrane module 23. The second aeration device 8 forms a rapid upward flow inside the flow guide tube by aeration and lifting, which increases the flow velocity on the membrane surface and slows down the occurrence of membrane fouling.

[0029] The second aeration device 8 is connected to the annular distributor 9 located at the bottom of the membrane module 23. The gas circulation system 6 is connected to the second aeration device 8 so that the gas introduced by the gas circulation system 6 and the wastewater are evenly distributed through the annular distributor 9 and then introduced into the membrane module 23. The annular distributor 9 includes several sets of layered annular distribution members 91 distributed along the direction of the membrane module 23. Each set of layered annular distribution members 91 consists of multiple concentric and nested distribution rings 911. The vertical projection of the distribution rings 911 in the upper layer of the layered annular distribution members 91 is located between two adjacent distribution rings 911 in the adjacent layered annular distribution members 911. In the layered annular distribution members 91 in the same layer, the inner layer distribution rings 911 are provided with several elastic inclined plates 912 on the side facing their adjacent distribution rings 911. The inclined plates 912 are fixed by torsion springs and are set towards the bottom of the reactor 21. The inclined plates 912 on the outer layer distribution rings 911 are placed above the inclined plates 912 on the inner layer distribution rings 911 (e.g., Figure 3 As shown, the black distribution ring 911 is the outer layer distribution ring 911, and the gray distribution ring 911 is the inner layer distribution ring 911, and the included angle between the two inclined plates 912 is 150-175°.

[0030] Example 1 Artificially prepared water was used as the influent, and denitrified sludge was used as the inoculum sludge, with an initial sludge concentration of 6830 mg / L. The influent flow was continuous. The operating temperature of the A / O reaction unit 10 was ambient temperature (19–30°C), and the operating temperature of the upflow anaerobic system was 35°C. The residence times in the A and O sections of the A / O reaction unit 10 were both 4 hours, and the residence time in the anaerobic treatment unit was 24 hours.

[0031] During the start-up phase, the influent ammonia nitrogen concentration is adjusted to 50 mg / L, the COD concentration is 0, and the dissolved oxygen in the O section of A / O reaction unit 10 is controlled above 2 mg / L. After treatment, all ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen. The 100% O section effluent is used as the influent for upflow anaerobic membrane treatment unit 20. The upflow anaerobic membrane treatment unit 20 has no COD influent. As heterotrophic microorganisms degrade the effluent, some COD and ammonia nitrogen are released and returned to the A / O reaction unit 10. At this point, due to the degradation by sludge microorganisms, the effluent contains some COD and ammonia nitrogen, at 50.2% and 38.8%, respectively. The effluent nitrite and nitrate nitrogen concentrations are 0.0 mg / L and 2.35 mg / L, respectively.

[0032] One week after startup, as heterotrophic bacteria were eliminated, the sludge concentration in the anaerobic membrane reactor dropped to 5186 mg / L, completing the initial sludge screening.

[0033] Example 2 After sludge screening, the influent quality was adjusted to COD 100 mg / L and ammonia nitrogen 200 mg / L. Dissolved oxygen in the O section of A / O reaction unit 10 was controlled at 0.5–1 mg / L. The influent, after being mixed with the anaerobic membrane recirculation, was treated by A / O reaction unit 10 to obtain ammonia nitrogen-containing wastewater in section A and nitrite and nitrate nitrogen-containing wastewater from section O. The two wastewaters were mixed at a 1:5 ratio and used as the influent for upflow anaerobic membrane treatment unit 20. After mixing, the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen were 10 mg / L, 116 mg / L, and 64 mg / L, respectively. The retention time during the start-up phase of the upflow anaerobic membrane treatment unit 20 was set at 24 hours. Since anaerobic ammonia-oxidizing bacteria had not yet been enriched in the anaerobic membrane reactor, the ammonia nitrogen concentration in the effluent of the anaerobic membrane treatment unit increased to 15 mg / L. As the ammonia nitrogen removal rate increased, it indicated that anaerobic ammonia-oxidizing bacteria began to accumulate and gradually increased the proportion of ammonia nitrogen-containing wastewater in section A.

[0034] Example 3 After three months of operation, the system reached a stable state, maintaining influent water quality at COD 100 mg / L and ammonia nitrogen 200 mg / L. Dissolved oxygen in the O section of A / O reaction unit 10 was controlled at 0.5–1 mg / L. After mixing the influent with the anaerobic membrane recirculation, the wastewater was treated by A / O reaction unit 10 to obtain ammonia nitrogen-containing wastewater in section A and nitrite and nitrate nitrogen-containing wastewater from section O. The two wastewaters were mixed at a ratio of 1:3 as the influent for upflow anaerobic membrane treatment unit 20. After mixing, the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen were 87 mg / L, 106 mg / L, and 19 mg / L, respectively. The upflow anaerobic membrane treatment unit 20 has a retention time of 24 hours, resulting in effluent ammonia nitrogen concentrations of less than 5 mg / L and nitrate nitrogen concentrations of less than 10 mg / L. The total nitrogen removal rate reaches over 90%.

Claims

1. An anaerobic ammonia oxidation denitrification process using an anaerobic membrane reactor, characterized in that, It includes an A / O reaction unit (10) and an upflow anaerobic membrane treatment unit (20). The A / O reaction unit (10) treats the wastewater to obtain ammonia nitrogen-containing wastewater output from section A and nitrite nitrogen-containing wastewater output from section O, and mixes the two wastewaters as the influent of the upflow anaerobic membrane treatment unit (20). The upflow anaerobic membrane treatment unit (20) includes a reactor (21), a sludge settling zone (22) at the bottom of the reactor (21), a membrane module (23) in the middle of the reactor (21), and a gas storage chamber (24) at the top of the reactor (21). The influent is filtered by the membrane module (23) to obtain the treated effluent. The A / O reaction unit (10) includes an integrated reaction tank (11), which is divided into an A-section reaction unit (12) and an O-section reaction unit (13). The A-section reaction unit (12) is connected to the inlet pipe (3) to perform hydrolysis acidification reaction on the wastewater. The bottom of the O-section reaction unit (13) is provided with a first aeration device (4) to aerate the O-section reaction unit (13) for nitrification reaction. The A-section reaction unit (12) and the O-section reaction unit (13) are equipped with a liquid circulation system (5) to input the ammonia nitrogen-containing wastewater treated by the A-section reaction unit (12) into the O-section reaction unit (13) for nitrification reaction, and to circulate the wastewater in the O-section reaction unit (13) back to the A-section reaction unit (12). The mixing ratio of ammonia nitrogen-containing wastewater to nitrite nitrogen-containing wastewater is 1:3-5; The denitrifying bacteria at the bottom of the upflow anaerobic membrane treatment unit (20) first use carbon source to convert some nitrate nitrogen into nitrite nitrogen and nitrite nitrogen into nitrogen gas. After the carbon source is consumed, in the middle of the upflow anaerobic membrane treatment unit (20), the remaining nitrite nitrogen and ammonia nitrogen are converted into nitrogen gas and a small amount of nitrate nitrogen by anaerobic ammonia oxidation bacteria. Some of the nitrate nitrogen generated by the anaerobic ammonia oxidation reaction is then returned to the A-section reaction unit (12) and mixed with organic matter in the incoming water for denitrification.

2. The anaerobic ammonia oxidation denitrification process of an anaerobic membrane reactor according to claim 1, characterized in that, The gas storage chamber (24) is connected to a gas circulation system (6), which circulates the gas in the gas storage chamber (24) into the membrane module (23) for aeration and cleaning.

3. The anaerobic ammonia oxidation denitrification process of an anaerobic membrane reactor according to claim 1, characterized in that, The reactor (21) is provided with a digester return pipeline (7) in the middle, which returns part of the sludge and organic matter to section A of the A / O reaction unit (10).

4. The anaerobic ammonia oxidation denitrification process of an anaerobic membrane reactor according to claim 2, characterized in that, The membrane module (23) is a hollow fiber membrane module. A flow guide tube with four closed sides and open top and bottom is arranged around the membrane module (23). There is a second aeration device (8) at the bottom of the membrane module (23). The second aeration device (8) forms a rapid upward flow inside the flow guide tube by aeration and lifting, which increases the flow velocity on the membrane surface and slows down the occurrence of membrane fouling.

5. The anaerobic ammonia oxidation denitrification process of an anaerobic membrane reactor according to claim 4, characterized in that, The second aeration device (8) is connected to the annular distributor (9) located at the bottom of the membrane module (23), and the gas circulation system (6) is connected to the second aeration device (8) so that the gas introduced by the gas circulation system (6) and the wastewater are evenly distributed through the annular distributor (9) and then introduced into the membrane module (23).

6. The anaerobic ammonia oxidation denitrification process of an anaerobic membrane reactor according to claim 5, characterized in that, The annular distributor (9) includes several sets of layered annular distributors (91) distributed along the direction of the membrane assembly (23). Each set of layered annular distributors (91) consists of multiple concentric and nested distribution rings (911). The vertical projection of the distribution ring (911) in the layered annular distributor (91) located in the upper layer is between two adjacent distribution rings (911) in the adjacent layered annular distributor (91).

7. The anaerobic ammonia oxidation denitrification process of an anaerobic membrane reactor according to claim 5, characterized in that, In the layered annular distribution member (91) located in the same layer, the inner layer distribution ring (911) is provided with several elastic inclined plates (912) on the side facing its adjacent distribution ring (911). The inclined plates (912) are fixed by torsion springs and are set towards the bottom of the reactor (21). The inclined plates (912) on the outer layer distribution ring (911) are placed above the inclined plates (912) on the inner layer distribution ring (911), and the included angle between the two inclined plates (912) is 150-175°.

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