A method for deep synergistic denitrification of urban sewage based on improved denitrification filter

Abstract

A method for deep synergistic denitrification of urban sewage based on an improved denitrification filter, which relates to a method for deep synergistic denitrification of sewage. It aims to solve the technical problems that the existing deep denitrification of urban sewage requires an external carbon source, has high operating costs, produces secondary pollution, and has poor COD and total nitrogen removal effects. This method: 1. Equipped with an improved denitrification filter deep synergistic denitrification treatment system: 2. Startup: inoculate manganese oxidizing bacteria, denitrifying bacteria, hydrolytic acidifying bacteria and anaerobic ammonia oxidizing bacteria in the system; 3. Stable treatment stage. This method does not require an external carbon source and reduces the demand for carbon sources. The method of the present invention achieves removal rates of 72.40%, 90.59% and 93.38% for COD, ammonia nitrogen and total nitrogen in the secondary effluent of urban sewage treatment plants, respectively. It can be used in the field of deep denitrification treatment of urban sewage.

Description

Technical Field

[0001] The invention relates to a method for deep synergistic denitrification of urban sewage, and belongs to the field of urban sewage treatment. Background Art

[0002] Excessive nitrogen discharged into slow-flowing water bodies such as rivers or lakes will accelerate the eutrophication process of water bodies and generate substances that are harmful to aquatic plants and animals. In order to reduce the discharge of nitrogen and improve the quality of the water environment, my country has built many urban sewage treatment plants and formulated strict emission standards, such as the "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB 18918-2002); some key areas have promulgated more stringent local standards, such as the "Emission Limits of Major Water Pollutants from Urban Sewage Treatment Plants" (DB 5301 / T 43-2020). Therefore, the development of deep denitrification technology for urban sewage is of great significance to reducing the discharge of pollutants such as COD, ammonia nitrogen, and total nitrogen, reducing the degree of water pollution, and improving the quality of the ecological environment.

[0003] Biological denitrification is widely used in deep denitrification of urban sewage due to its high efficiency, low cost and low secondary pollution; however, the organic matter in the secondary effluent is usually difficult to degrade and cannot meet the carbon source requirements of denitrification, so an external carbon source is needed. Current research mainly focuses on the selection of carbon sources, process optimization, microbial flora structure, denitrification mechanism and other aspects. Commonly used carbon sources include: methanol, ethanol, acetic acid, sodium acetate, glucose, citric acid, plant tissues, and artificial biodegradable polymers such as polycaprolactone, polycaprolactone, polybutylene succinate, polyhydroxyalkanoate, polylactic acid, poly (3-hydroxybutyric acid-co-3-hydroxyvalerate), etc. However, the addition of an external carbon source will not only increase the operating cost, but also cause secondary pollution if improperly added. In addition, autotrophic denitrification can also be used for deep denitrification of urban sewage, with inorganic substances (reduced sulfur, hydrogen, Fe 2+ etc.) as electron donors to reduce nitrate nitrogen to nitrogen gas. However, the addition of inorganic substances will increase operating costs, and the pH will drop significantly due to the consumption of alkalinity by autotrophic denitrification; at the same time, reduced sulfur and Fe 2+ The oxidation products will enter the water and cause new pollution.

[0004] The Chinese patent "A method for deep treatment of urban sewage based on improved denitrification filter column" with publication number CN111196628A adopts a modified denitrification filter column. When starting, the quartz sand filler of the modified denitrification filter column is covered with a biofilm, which contains denitrifying bacteria, heterotrophic bacteria and manganese oxidizing bacteria, and contains biological manganese oxides; the filter column is used to deeply treat urban sewage, and the average removal rates of COD and total nitrogen after treatment are higher than 53.72% and 46.20%. Although this method does not add an external carbon source during the treatment process, the removal rates of COD and total nitrogen are low.

[0005] Therefore, there is an urgent need for a deep denitrification technology for urban sewage with low operating cost, no secondary pollution and good treatment effect. Summary of the invention

[0006] The present invention aims to solve the technical problems that the existing deep denitrification of urban sewage requires an external carbon source, has high operating costs, produces secondary pollution, and has poor COD and total nitrogen removal effects, and provides a method for deep synergistic denitrification of urban sewage based on an improved denitrification filter.

[0007] The method for deep synergistic denitrification of urban sewage based on improved denitrification filter of the present invention is carried out according to the following steps:

[0008] 1. Equipped with an improved denitrification filter deep synergistic denitrification treatment system: The improved denitrification filter deep synergistic denitrification treatment system includes an inlet water tank 1, a peristaltic pump 2, an inlet valve 3, an improved denitrification filter column 4, and a backwash valve 5;

[0009] A supporting layer 4-2 is arranged at the lower part of the shell 4-1 of the improved denitrification filter column 4, a packing layer 4-3 is arranged on the supporting layer 4-2, a water inlet 4-4 is arranged at the bottom of the shell 4-1, and a water outlet 4-5 is arranged at the upper part of the side wall of the shell 4-1; wherein the supporting layer 4-2 is composed of quartz sand; and the packing layer 4-3 is also composed of quartz sand;

[0010] The water inlet tank 1 is connected to the water inlet 4-4 of the improved denitrification filter column 4 through the peristaltic pump 2 and the water inlet valve 3; the backwash valve 5 is also connected to the water inlet 4-4 of the improved denitrification filter column 4; the water inlet mode of the system is upward flow;

[0011] 2. Start-up: Input the secondary effluent of the urban sewage treatment plant into the inlet water tank 1, and add manganese sulfate into the inlet water tank 1 to make the manganese sulfate concentration in the water 0.4-0.6 mg / L; the dissolved oxygen concentration in the inlet water is 0.5-0.7 mg / L; the water in the inlet water tank 1 is transported to the improved denitrification filter column 4 through the peristaltic pump 2 and the inlet valve 3, and manganese oxidizing bacteria and denitrifying bacteria are inoculated into the improved denitrification filter column 4 at the same time, once every 3 days, for a total of 5 times; manganese oxidizing bacteria, denitrifying bacteria After the inoculation of nitrifying bacteria is completed, hydrolytic acidifying bacteria and anaerobic ammonia oxidizing bacteria are inoculated; the hydrolytic acidifying bacteria are inoculated once every 4 days, for a total of 6 times; the anaerobic ammonia oxidizing bacteria are inoculated once every 5 days, for 2 times. When the ammonia nitrogen in the effluent is stable, the ammonia nitrogen concentration in the influent is gradually increased to 7 mg / L in a step-by-step manner by adding ammonium chloride to the influent tank 1. Under each ammonia nitrogen concentration condition, the anaerobic ammonia oxidizing bacteria are inoculated twice at a frequency of once every 5 days and run until the ammonia nitrogen in the effluent is stable, completing the startup;

[0012] 3. Stabilization treatment stage: The secondary effluent of the urban sewage treatment plant to be deeply treated is added to the inlet water tank 1. The water in the inlet water tank 1 is input into the improved denitrification filter column 4 through the peristaltic pump 2 and the inlet valve 3. The hydraulic retention time of the improved denitrification filter column 4 is 6 to 8 hours, and the effluent flows out from the outlet 4-5; backwashing is performed every 9 to 11 days of operation, the backwashing time is 3 to 5 minutes, and the backwashing intensity is 10 to 12 L / (s·m 2 ) to complete the deep synergistic denitrification treatment of urban sewage.

[0013] Furthermore, the quartz sand of the supporting layer 4 - 2 has a thickness of 9 to 12 cm and a particle size of 1 to 2 cm.

[0014] Furthermore, the quartz sand of the filler layer 4 - 3 has a thickness of 65 to 75 cm and a particle size of 2 to 4 mm.

[0015] Furthermore, when inoculating manganese oxidizing bacteria and denitrifying bacteria in step 2, 500 mL of the mixed bacterial solution is inoculated each time, and the concentration of manganese oxidizing bacteria in the mixed bacterial solution is 1 g / L to 3 g / L, and the concentration of denitrifying bacteria is 3 g / L to 5 g / L.

[0016] Furthermore, when the hydrolytic acidifying bacteria are inoculated in step 2, 400 mL of the hydrolytic acidifying bacteria solution is inoculated each time, and the concentration of the hydrolytic acidifying bacteria in the solution is 5 g / L to 8 g / L.

[0017] Furthermore, when inoculating anaerobic ammonium oxidizing bacteria in step 2, 300 mL of anaerobic ammonium oxidizing bacterial solution is inoculated each time, and the concentration of anaerobic ammonium oxidizing bacteria in the bacterial solution is 4 g / L to 6 g / L.

[0018] Furthermore, the method of gradually increasing the ammonia nitrogen concentration in the influent to 7 mg / L is to first increase the ammonia nitrogen concentration in the influent to 2 mg / L for inoculation and run until it is stable, and then increase it to 3 mg / L, 4 mg / L, 5 mg / L, and 7 mg / L in sequence for inoculation and run until the ammonia nitrogen in the effluent is stable.

[0019] Furthermore, the stability of ammonia nitrogen in the effluent described in step 2 means that the average ammonia nitrogen concentration in the water does not fluctuate by more than 10% within 10 to 12 consecutive days.

[0020] The organic matter in the secondary effluent of urban sewage treatment plants is difficult to degrade because these organic matter are not removed during the secondary biochemical treatment process of urban sewage treatment plants. The secondary effluent contains a certain amount of dissolved oxygen, which can oxidize the divalent manganese ions in the influent to biological manganese oxides. After the biological manganese oxides oxidize the difficult-to-degrade organic matter in the secondary effluent, they are reduced to divalent manganese ions, which can still be oxidized to biological manganese oxides by the dissolved oxygen in the influent, thereby achieving the continuous oxidation of difficult-to-degrade organic matter by biological manganese oxides. However, anaerobic ammonia-oxidizing bacteria need to use ammonia nitrogen as an electron donor to reduce nitrite nitrogen to nitrogen gas under strictly anaerobic conditions. Therefore, the difficulties of this technology are: 1) How to make manganese oxidizing bacteria that require dissolved oxygen and anaerobic ammonia oxidizing bacteria, denitrifying bacteria, and hydrolytic acidifying bacteria that do not require dissolved oxygen coexist in the denitrification filter and have high activity; 2) It is necessary to reasonably determine the dissolved oxygen concentration in the influent. When the dissolved oxygen concentration in the influent is high, it is beneficial to the oxidation of difficult-to-degrade organic matter by biological manganese oxides; however, it will inhibit the activity of anaerobic ammonia oxidizing bacteria, denitrifying bacteria, and hydrolytic acidifying bacteria. At the same time, heterotrophic bacteria (aerobic bacteria) will grow in the improved denitrification filter. The heterotrophic bacteria use the dissolved oxygen in the influent to oxidize the oxidation products of difficult-to-degrade organic matter into carbon dioxide and water, resulting in a reduction in the carbon source for denitrification, thereby affecting the deep synergistic denitrification effect. When the dissolved oxygen concentration of the influent is low, it is conducive to the improvement of the activity of anaerobic ammonia oxidizing bacteria, denitrifying bacteria, and hydrolytic acidifying bacteria, and is conducive to reducing the consumption of oxidation products of difficult-to-degrade organic matter by heterotrophic bacteria, but it is not conducive to the oxidation of divalent manganese ions to biological manganese oxides, resulting in a reduction in the amount of difficult-to-degrade organic matter oxidized by biological manganese oxides, that is, a reduction in the amount of easily degradable organic matter produced (a reduction in the amount of carbon source for denitrification), which ultimately affects the deep synergistic denitrification effect. This technology uses a specific inoculation, cultivation, and acclimation scheme to allow manganese oxidizing bacteria, anaerobic ammonia oxidizing bacteria, denitrifying bacteria, and hydrolytic acidifying bacteria to coexist in the improved denitrification filter and maintain a high activity. By setting a reasonable dissolved oxygen concentration in the influent, the oxidation products of difficult-to-degrade organic matter in the system provide sufficient carbon sources for deep synergistic denitrification, thereby solving the above two problems.

[0021] Compared with the existing urban sewage deep treatment method, the present invention has the following advantages:

[0022] 1) No need for an external carbon source, and low operating cost: The carbon source sources of the present invention include: a) refractory organic matter in the secondary effluent of a municipal sewage treatment plant. In the improved denitrification filter deep synergistic denitrification treatment system of the present invention, denitrifying bacteria are inoculated and domesticated for a long time to gradually domesticate denitrifying bacteria that can use the refractory organic matter in the secondary effluent as a carbon source. b) Hydrolysis products of refractory organic matter in the secondary effluent. In the improved denitrification filter deep synergistic denitrification treatment system, hydrolysis acidification bacteria are inoculated and domesticated to gradually domesticate hydrolysis acidification bacteria that can hydrolyze the refractory organic matter in the secondary effluent into small molecular organic matter. c) Oxidation products of refractory organic matter in the secondary effluent. In the improved denitrification filter deep synergistic denitrification treatment system, biological manganese oxides are generated in situ, and the oxidizing activity of the biological manganese oxides is used to oxidize the refractory organic matter in the secondary effluent into easily degradable organic matter. d) After the death of microorganisms, a carbon source can be provided for denitrification. Therefore, the present invention does not require an external carbon source and has a low operating cost.

[0023] 2) Reduced carbon source demand: In this improved denitrification filter deep synergistic denitrification treatment system, by gradually increasing the influent ammonia nitrogen concentration and continuously inoculating anaerobic ammonia oxidizing bacteria, partial denitrification-anaerobic ammonia oxidation and denitrification deep synergistic denitrification are achieved, which improves the deep denitrification effect and reduces the carbon source demand. Theoretically, 2.86 mg COD is required to reduce 1 mg of nitrate nitrogen to nitrogen gas, and 1.14 mg COD is required to reduce 1 mg of nitrate nitrogen to nitrite nitrogen; however, partial denitrification-anaerobic ammonia oxidation only requires about 0.74 mg COD to remove 1 mg of total nitrogen (nitrate nitrogen + ammonia nitrogen). The actual amount of COD consumed by the present invention to remove 1 mg of total nitrogen is 0.99 mg, which is much lower than the theoretical COD consumption.

[0024] 3) Good removal effect of COD, ammonia nitrogen and total nitrogen: Without adding an external carbon source, the method of the present invention can reduce the COD, ammonia nitrogen and total nitrogen of the secondary effluent of the urban sewage treatment plant from 28.39 to 30.17 mg / L, 6.98 to 7.13 mg / L and 22.07 to 22.34 mg / L respectively to COD of 7.41 to 8.75 mg / L, ammonia nitrogen of 0.60 to 0.71 mg / L and total nitrogen of 22.07 to 22.34 mg / L. 1.41~1.54mg / L, COD, ammonia nitrogen, total nitrogen removal rates were 69.65%~75.06%, 89.83%~91.46%, 93.07%~93.59% respectively; COD, ammonia nitrogen, total nitrogen average concentrations were 8.12mg / L, 0.66mg / L, 1.47mg / L, average removal rates reached 72.40%, 90.59%, 93.38% respectively. Outlet COD, ammonia nitrogen, total nitrogen all meet the Class IV standard in the Surface Water Environmental Quality Standard (GB 3838-2002).

[0025] 4) No secondary pollution: The present invention uses the refractory organic matter in the secondary effluent of the urban sewage treatment plant, the oxidation products and hydrolysis products of the refractory organic matter in the secondary effluent, and the dead microorganisms as carbon sources, and does not require an external carbon source, so no secondary pollution will be generated. At the same time, it can further degrade the toxic and harmful substances in the secondary effluent, reducing its potential environmental risks.

[0026] 5) No sludge is generated, thus reducing the cost of sludge treatment. The dead microorganisms in the improved denitrification filter are used as a carbon source for denitrification, so no sludge is generated.

[0027] The present invention effectively solves the problems of deep denitrification of urban sewage, which require an external carbon source, have high operating costs, generate secondary pollution, and have poor COD and total nitrogen removal effects, and achieves low-cost and high-efficiency removal of COD and total nitrogen. After the secondary effluent of a municipal sewage treatment plant is treated in an improved denitrification filter tank, it can be reduced from the Class I B standard in the Pollutant Discharge Standard for Municipal Sewage Treatment Plants (GB18918-2002) to the Class IV standard in the Environmental Quality Standard for Surface Water (GB 3838-2002), which is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the device of the improved denitrification filter deep collaborative denitrification treatment system of the present invention; in the figure, 1 is a water inlet tank, 2 is a peristaltic pump, 3 is a water inlet valve, 4 is an improved denitrification filter column, 4-1 is a shell, 4-2 is a supporting layer, 4-3 is a packing layer, 4-4 is a water inlet, 4-5 is a water outlet, and 5 is a backwash valve;

[0029] Figure 2 It is a COD removal effect diagram of the treatment in Example 1;

[0030] Figure 3 This is a diagram showing the effect of removing ammonia nitrogen during treatment in Example 1;

[0031] Figure 4 This is a diagram showing the removal effect of total nitrogen during treatment in Example 1. DETAILED DESCRIPTION

[0032] The beneficial effects of the present invention are verified by the following examples.

[0033] Example 1: The method for deep synergistic denitrification of urban sewage based on the improved denitrification filter of this example is carried out according to the following steps:

[0034] 1. Equipped with an improved denitrification filter deep synergistic denitrification treatment system: The improved denitrification filter deep synergistic denitrification treatment system includes an inlet water tank 1, a peristaltic pump 2, an inlet valve 3, an improved denitrification filter column 4, and a backwash valve 5;

[0035] A supporting layer 4-2 is arranged at the lower part of the shell 4-1 of the improved denitrification filter column 4, a packing layer 4-3 is arranged on the supporting layer 4-2, a water inlet 4-4 is arranged at the bottom of the shell 4-1, and a water outlet 4-5 is arranged at the upper part of the side wall of the shell 4-1; wherein the supporting layer 4-2 is composed of quartz sand, the thickness of the quartz sand of the supporting layer 4-2 is 10cm, and the particle size is 1-2cm; the packing layer 4-3 is also composed of quartz sand, the thickness of the quartz sand of the packing layer 4-3 is 70cm, and the particle size is 2-4mm; the shell 4-1 is cylindrical, with an inner diameter of 40cm and a height of 100cm;

[0036] The water inlet tank 1 is connected to the water inlet 4-4 of the improved denitrification filter column 4 through the peristaltic pump 2 and the water inlet valve 3; the backwash valve 5 is also connected to the water inlet 4-4 of the improved denitrification filter column 4; the water inlet mode of the system is upward flow;

[0037] 2. Start-up: Input the secondary effluent of the urban sewage treatment plant into the inlet tank 1, and add manganese sulfate into the inlet tank 1 to make the manganese sulfate concentration in the water 0.5 mg / L; the dissolved oxygen concentration of the water in the inlet tank 1 is 0.5-0.7 mg / L; input the water in the inlet tank 1 into the improved denitrification filter column 4 through the peristaltic pump 2 and the inlet valve 3, and inoculate manganese oxidizing bacteria and denitrifying bacteria into the improved denitrification filter column 4 every 3 days, and inoculate 50% of the mixed solution each time. 0mL, wherein the concentration of manganese oxidizing bacteria in the mixed solution is 2g / L, and the concentration of denitrifying bacteria is 4g / L, and a total of 5 inoculations are performed; after the inoculation of manganese oxidizing bacteria and denitrifying bacteria is completed, hydrolytic acidifying bacteria and anaerobic ammonia oxidizing bacteria are inoculated, wherein the hydrolytic acidifying bacteria are inoculated once every 4 days, and each time 400mL of hydrolytic acidifying bacteria solution is inoculated, and the concentration of hydrolytic acidifying bacteria in the bacterial solution is 6g / L, and a total of 6 inoculations are performed; each time 300mL of anaerobic ammonia oxidizing bacteria solution is inoculated, and the concentration of anaerobic ammonia oxidizing bacteria in the bacterial solution is 5g / L, inoculated once every 5 days, after 2 inoculations, when the average concentration of effluent ammonia nitrogen fluctuates by no more than 10% within 12 consecutive days, the system is considered to be stable; then, by adding ammonium chloride to the inlet water tank 1, the ammonia nitrogen concentration in the inlet water is increased to 2mg / L, and then 300mL of anaerobic ammonia oxidizing bacteria solution is inoculated, the concentration of anaerobic ammonia oxidizing bacteria in the bacteria solution is 5g / L, inoculated once every 5 days, after 2 inoculations, when the average concentration of effluent ammonia nitrogen fluctuates by no more than 10% within 12 consecutive days, it is considered to be stable; then the ammonia nitrogen concentration in the inlet water is increased to 3mg / L, 4mg / L, 5mg / L and 7mg / L in turn, under each ammonia nitrogen concentration condition, anaerobic ammonia oxidizing bacteria are inoculated according to the same inoculation method when the ammonia nitrogen concentration is 2mg / L and run until the ammonia nitrogen in the effluent is stable, and the startup is completed; after the startup is completed, manganese oxidizing bacteria, denitrifying bacteria, hydrolytic acidification bacteria, and anaerobic ammonia oxidizing bacteria coexist stably in the improved denitrification filter deep synergistic denitrification treatment system;

[0038] 3. Stabilization treatment stage: add the secondary effluent of the urban sewage treatment plant to be deeply treated into the inlet water tank 1, and control the dissolved oxygen of the water in the inlet water tank 1 to be 0.5-0.7 mg / L; the water in the inlet water tank 1 is input into the improved denitrification filter column 4 through the peristaltic pump 2 and the inlet valve 3, and the hydraulic retention time of the improved denitrification filter column 4 is 7 hours, and the effluent flows out from the outlet 4-5, and the COD, ammonia nitrogen and total nitrogen in the effluent are detected; backwashing is performed every 10 days of operation, the backwashing time is 5 minutes, and the backwashing intensity is 10L / (s·m 2 ) to complete the deep synergistic denitrification treatment of urban sewage.

[0039] In this embodiment, the startup phase lasted for 148 days. After the startup was completed, the surface of the quartz sand of the packing layer 4-3 was loaded with manganese oxidizing bacteria, denitrifying bacteria, hydrolytic acidifying bacteria and anaerobic ammonia oxidizing bacteria. Multiple microorganisms synergistically removed COD, ammonia nitrogen and total nitrogen in the secondary effluent. In step 4, the COD, ammonia nitrogen and total nitrogen in the secondary effluent of the urban sewage treatment plant to be deeply treated were 28.39-30.17 mg / L, 6.98-7.13 mg / L and 22.07-22.34 mg / L, respectively. The COD concentration in the effluent treated by the improved denitrification filter deep collaborative denitrification treatment system is as follows: Figure 2 As shown, the ammonia nitrogen concentration is Figure 3 The total nitrogen concentration is shown in Figure 4 As shown, from Figure 2 , Figure 3 and Figure 4 It can be seen that the COD in the treated effluent is 7.41-8.75 mg / L, ammonia nitrogen is 0.60-0.71 mg / L, and total nitrogen is 1.41-1.54 mg / L. The removal rates of COD, ammonia nitrogen, and total nitrogen are 69.65%-75.06%, 89.83%-91.46%, and 93.07%-93.59%, respectively; the average concentrations of COD, ammonia nitrogen, and total nitrogen are 8.12 mg / L, 0.66 mg / L, and 1.47 mg / L, respectively, and the average removal rates are 72.40%, 90.59%, and 93.38%, respectively. The effluent COD, ammonia nitrogen, and total nitrogen all meet the Class IV standards in the Surface Water Environmental Quality Standard (GB 3838-2002).

[0040] Comparative Example 1: The difference between this comparative example and Example 1 is that the dissolved oxygen concentration of the water in the water inlet tank 1 in step 2 and step 3 is 0.3 mg / L; the other steps and parameters are the same as those in Example 1.

[0041] Under the conditions of Comparative Example 1, the TN removal rate was about 70% in the startup stage and the stable treatment stage. This is because the dissolved oxygen concentration is low, which is conducive to the improvement of the activity of anaerobic ammonia oxidizing bacteria, denitrifying bacteria, and hydrolytic acidifying bacteria, and is conducive to reducing the consumption of heterotrophic bacteria on the oxidation products of difficult-to-degrade organic matter, but is not conducive to the oxidation of divalent manganese ions to biological manganese oxides, resulting in a reduction in the amount of difficult-to-degrade organic matter oxidized by biological manganese oxides, that is, a reduction in the amount of easily degradable organic matter produced (a reduction in the amount of carbon source for denitrification), which ultimately affects the deep synergistic denitrification effect.

[0042] Comparative Example 2: This comparative example is different from Example 1 in that the dissolved oxygen concentration of the water in the water inlet tank 1 in step 2 and step 3 is 1.5 mg / L; the other steps and parameters are the same as those in Example 1.

[0043] Under the conditions of Comparative Example 2, the TN removal rate was about 65% in the startup stage and the stable treatment stage. This is because the high dissolved oxygen concentration is conducive to the oxidation of refractory organic matter by biological manganese oxides, but it will inhibit the activity of anaerobic ammonia oxidizing bacteria, denitrifying bacteria, and hydrolytic acidifying bacteria. At the same time, heterotrophic bacteria (aerobic bacteria) will grow in the improved denitrification filter, and the heterotrophic bacteria will use the dissolved oxygen in the influent to oxidize the oxidation products of refractory organic matter into carbon dioxide and water, resulting in a reduction in the carbon source for denitrification, and it is impossible to achieve a state where manganese oxidizing bacteria, denitrifying bacteria, hydrolytic acidifying bacteria and anaerobic ammonia oxidizing bacteria cannot coexist in a balanced manner, which affects the deep synergistic denitrification effect.

[0044] Comparative Example 3: This comparative example is different from Example 1 in that: in the startup stage of step 2, the inoculation procedure of anaerobic ammonia oxidizing bacteria is: 300 mL of anaerobic ammonia oxidizing bacteria are inoculated with bacterial solution each time, the concentration of anaerobic ammonia oxidizing bacteria in the bacterial solution is 5 g / L, and the bacteria are inoculated once every 5 days. After inoculation twice, when the average concentration of effluent ammonia nitrogen fluctuates by no more than 10% within 12 consecutive days, the system is considered to be stable; then, ammonium chloride is added to the inlet water tank 1 to directly increase the ammonia nitrogen concentration in the inlet water to 7 mg / L, and then 300 mL of bacterial solution is inoculated, the concentration of anaerobic ammonia oxidizing bacteria in the bacterial solution is 5 g / L, and the bacteria are inoculated once every 5 days. After inoculation twice, when the average concentration of effluent ammonia nitrogen fluctuates by no more than 10% within 12 consecutive days, the system is considered to be stable and the startup is completed; the other steps and parameters are the same as those in Example 1.

[0045] Under the conditions of Comparative Example 3, after the start-up phase was completed and during the stable treatment phase, the TN removal rate was about 60%. This was because the ammonia nitrogen concentration increased significantly and suddenly, and the high ammonia nitrogen concentration in the denitrification filter inhibited the activity of denitrifying bacteria and anaerobic ammonia oxidizing bacteria, which was not conducive to the growth and reproduction of anaerobic ammonia oxidizing bacteria in the denitrification filter, and the state in which manganese oxidizing bacteria, denitrifying bacteria, hydrolytic acidification bacteria and anaerobic ammonia oxidizing bacteria could not coexist in a balanced manner could not be achieved, which affected the removal of nitrogen.

Claims

1. A method for deep and collaborative nitrogen removal from urban sewage based on an improved denitrification filter, characterized in that the method is carried out according to the following steps: I. Equip an improved denitrification filter for deep and collaborative nitrogen removal treatment system: The improved denitrification filter for deep and collaborative nitrogen removal treatment system includes an inlet water tank (1), a peristaltic pump (2), an inlet valve (3), an improved denitrification filter column (4), and a backwashing valve (5); A supporting layer (4-2) is arranged at the lower part inside the housing (4-1) of the improved denitrification filter column (4), a packing layer (4-3) is arranged above the supporting layer (4-2), an inlet (4-4) is arranged at the bottom of the housing (4-1), and an outlet (4-5) is arranged at the upper part of the side wall of the housing (4-1); wherein the supporting layer (4-2) is composed of quartz sand; the packing layer (4-3) is also composed of quartz sand; The inlet water tank (1) is connected to the inlet (4-4) of the improved denitrification filter column (4) through the peristaltic pump (2) and the inlet valve (3); the backwashing valve (5) is also connected to the inlet (4-4) of the improved denitrification filter column (4); the water inlet mode of this system is upward flow; II. Start-up: Input the secondary effluent of the urban sewage treatment plant into the inlet water tank (1), and at the same time add manganese sulfate to the inlet water tank (1) so that the concentration of manganese sulfate in the water is 0.4 - 0.6 mg / L; the dissolved oxygen concentration in the influent water is 0.5 - 0.7 mg / L; the water in the inlet water tank (1) is transported into the improved denitrification filter column (4) through the peristaltic pump (2) and the inlet valve (3), and at the same time inoculate manganese-oxidizing bacteria and denitrifying bacteria into the improved denitrification filter column (4), inoculate once every 3 days, for a total of 5 times, each time inoculating 500 mL of the mixed bacterial solution, the bacterial concentration of manganese-oxidizing bacteria in the mixed bacterial solution is 1 g / L - 3 g / L, and the bacterial concentration of denitrifying bacteria is 3 g / L - 5 g / L; after the inoculation of manganese-oxidizing bacteria and denitrifying bacteria is completed, then inoculate hydrolytic acidifying bacteria and anaerobic ammonium-oxidizing bacteria; wherein the hydrolytic acidifying bacteria are inoculated once every 4 days, for a total of 6 times, each time inoculating 400 mL of the hydrolytic acidifying bacteria solution, and the concentration of hydrolytic acidifying bacteria in the bacterial solution is 5 g / L - 8 g / L; the anaerobic ammonium-oxidizing bacteria are inoculated once every 5 days, inoculated 2 times, each time inoculating 300 mL of the anaerobic ammonium-oxidizing bacteria solution, and the concentration of anaerobic ammonium-oxidizing bacteria in the bacterial solution is 4 g / L - 6 g / L; when the ammonia nitrogen in the effluent is stable, gradually increase the ammonia nitrogen concentration in the influent water to 7 mg / L in a step-by-step manner by adding ammonium chloride to the inlet water tank (1), and under each ammonia nitrogen concentration condition, inoculate 2 times at a frequency of inoculating anaerobic ammonium-oxidizing bacteria once every 5 days and operate until the ammonia nitrogen in the effluent is stable to complete the start-up; 3. Stabilization treatment stage: the secondary effluent of the urban sewage treatment plant to be deeply treated is added to the inlet water tank (1), and the water in the inlet water tank (1) is input into the improved denitrification filter column (4) through the peristaltic pump (2) and the inlet valve (3). The hydraulic retention time of the improved denitrification filter column (4) is 6 to 8 hours, and the effluent flows out from the outlet (4-5); backwashing is performed every 9 to 11 days of operation, the backwashing time is 3 to 5 minutes, and the backwashing intensity is 10 to 12 L / (s·m 2 ) to complete the deep synergistic denitrification treatment of urban sewage.

2. A method for deep and collaborative nitrogen removal from urban sewage based on an improved denitrification filter according to claim 1, characterized in that the thickness of the quartz sand in the supporting layer (4-2) is 9 - 12 cm and the particle size is 1 - 2 cm.

3. A method for deep and collaborative nitrogen removal from urban sewage based on an improved denitrification filter according to claim 1 or 2, characterized in that the thickness of the quartz sand in the packing layer (4-3) is 65 - 75 cm and the particle size is 2 - 4 mm.

4. A method for deep synergistic denitrification of urban sewage based on an improved denitrification filter according to claim 1 or 2, It is characterized in that The specific method of gradually increasing the ammonia nitrogen concentration in the influent to 7 mg / L in step 2 is: first increase the ammonia nitrogen concentration in the influent to 3 mg / L for inoculation and run until it is stable, then increase it to 4 mg / L, 5 mg / L, and 7 mg / L in sequence for inoculation and run until the ammonia nitrogen in the effluent is stable.

5. A method for deep synergistic denitrification of urban sewage based on an improved denitrification filter according to claim 1 or 2, It is characterized in that The effluent ammonia nitrogen stability described in step 2 refers to the fact that the average ammonia nitrogen concentration in the water fluctuates by no more than 10% within 10 to 12 consecutive days.

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