Method for improving autotrophic denitrification contribution of a mixed culture type mainstream anammox granular sludge process

Abstract

The application discloses a method for improving autotrophic denitrification contribution of a mixed culture type mainstream anaerobic ammonia oxidation granular sludge process, and comprises the following steps: 1) performing carbon control pretreatment on municipal sewage, regulating and controlling the content of dissolved organic matter in the sewage and the proportion of the dissolved organic matter and total nitrogen, and improving the carbon source quality of the sewage; 2) performing limited oxygen aeration treatment on part of the sewage after the carbon control pretreatment, mixing the sewage with the sewage without aeration treatment to optimize the nitrogen composition of the sewage, and then pumping the sewage into an upflow anaerobic ammonia oxidation reactor; and 3) limiting the heterotrophic denitrifying bacteria mediated nitrite nitrogen reduction activity in the upflow anaerobic ammonia oxidation granular sludge reactor through directional sludge discharge based on microsieve screening. According to the method, the autotrophic denitrification contribution of the anaerobic ammonia oxidation granular sludge reactor can be improved to more than 75%, and the effluent meets the first level A discharge standard of urban sewage, and the method has the advantages of flexibility, high efficiency and wide applicability.

Description

(I) Technical Field

[0001] This invention relates to a method for improving the autotrophic nitrogen removal contribution of the mainstream anaerobic ammonium oxidation granular sludge process in a mixed-culture system. (II) Background Technology

[0002] Carbon neutrality has become a hot topic in the upgrading and retrofitting of wastewater treatment plants worldwide. Due to its significant advantages in energy saving, emission reduction, and efficiency improvement, anaerobic ammonia oxidation (ANAO) technology has been regarded as an alternative to traditional biological nitrogen removal. Currently, the ANAO process has been successfully applied to the treatment of sludge digestate in hundreds of wastewater treatment plants around the world, achieving substantial results in carbon emission reduction for wastewater treatment plants.

[0003] Soluble organic matter (SO4) in urban wastewater is one of the main obstacles to the stable operation of mainstream anaerobic ammonia oxidation (ANAO) processes. This is because heterotrophic denitrifying bacteria compete with ANAOs for substrate nitrite in the presence of SO4, leading to ammonia nitrogen accumulation in the effluent. Due to the high growth rate and yield of denitrifying bacteria, mainstream denitrification systems struggle to maintain an effective abundance of ANAOs when SO4 is abundant. Typically, the SO4 level needs to be controlled below 0.5% to balance the functions of ANAOs and denitrifying bacteria. However, this remains a significant challenge for current carbon-controlled pretreatment technologies (such as chemically enhanced primary treatment and high-velocity activated sludge processes).

[0004] Anaerobic ammonia oxidation granular sludge process has been proven effective in treating low-temperature mainstream wastewater (15℃, <70mg TN L). -1 It has a high volumetric nitrogen removal load (3-7.0 kg Nm³). -3 d -1 The process has great application potential. However, when the influent dissolved organic matter COD / N ratio is greater than 1.0, it significantly reduces the autotrophic nitrogen removal contribution of the process, leading to the accumulation of ammonia nitrogen in the effluent, which cannot directly meet the Class A discharge standard (NH4+) for urban wastewater in my country. + -N≤5mg L -1 and TN≤15mg L -1 ).

[0005] Therefore, how to deal with the interference of dissolved organic matter in the carbon control pretreatment effluent is a problem that restricts the engineering application of this mainstream anaerobic ammonia oxidation granular sludge process. (III) Summary of the Invention

[0006] The purpose of this invention is to provide a method to improve the autotrophic nitrogen removal contribution of the mainstream anaerobic ammonia oxidation granular sludge process in mixed-culture. The method proposed in this invention can increase the autotrophic nitrogen removal contribution of the mainstream anaerobic ammonia oxidation granular sludge process in urban sewage to more than 75%, and the effluent meets the Class A discharge standard for urban sewage. It has the advantages of flexibility, high efficiency and wide applicability.

[0007] The technical solution adopted in this invention is:

[0008] This invention provides a method for improving the autotrophic nitrogen removal contribution of a mixed-culture mainstream anaerobic ammonia oxidation granular sludge process. The method includes the following steps: 1) Pre-treating urban wastewater with carbon control to regulate the content of dissolved organic matter and its ratio to total nitrogen, thereby improving the quality of the wastewater carbon source; 2) Performing oxygen-limited aeration treatment on a portion of the pre-treated wastewater and mixing it with untreated wastewater to optimize the nitrogen composition before pumping it into an upflow anaerobic ammonia oxidation reactor; 3) Limiting the nitrite reduction activity mediated by heterotrophic denitrifying bacteria in the upflow anaerobic ammonia oxidation granular sludge reactor through directional sludge discharge based on micro-screening.

[0009] Furthermore, in step 1), when the proportion of dissolved organic matter in urban sewage to total COD is <30%, 30-50%, or >50%, respectively, chemically enhanced primary treatment, high-load activated sludge contact-stabilization treatment, and precision screening and filtration treatment are adopted to increase the proportion of dissolved organic matter in sewage to more than 80% of total organic matter, and the ratio of dissolved organic matter to total nitrogen is controlled within the range of 1.0 to 2.5:1.

[0010] Furthermore, in step 2), 50-70% of the volume of wastewater after carbon control pretreatment in step 1) is subjected to oxygen-limited aeration treatment (dissolved oxygen <0.5 mg / L). -1 This process oxidizes over 90% of ammonia nitrogen into nitrite and nitrate. If the ammonia nitrogen concentration in the effluent from the upflow anaerobic ammonia oxidation reactor is higher than 5 mg / L... -1 Furthermore, the sum of the concentrations of nitrite and nitrate is less than 2 mg / L. -1 The proportion of wastewater treated by oxygen-limited aeration is increased within the range of 50% to 70%. When the ratio of carbohydrate and volatile acid concentrations to ammonia nitrogen concentration after pretreatment in step 1) is higher than 1.5 (g-COD / gN), for every 0.1 increase, the ratio of nitrate nitrogen to nitrite nitrogen concentration is increased by 0.03 by extending the oxygen-limited aeration time.

[0011] Further, in step 2), the upflow anaerobic sludge blanket reactor is inoculated with high-load anaerobic ammonia oxidation granular sludge, and the total nitrogen is treated to <70 mg / L at 10–20°C. -1 Urban wastewater with a total COD / N ratio of 1.0 to 4.0 and a nitrogen removal load per unit volume > 1.0 kg N / m³ -3 d -1 .

[0012] Furthermore, in step 3), when the ratio of carbohydrate and volatile acid concentrations to ammonia nitrogen concentration in the influent of the upflow anaerobic ammonia oxidation granular sludge reactor is >0.5 (g-COD / gN), a certain mass of flocculent sludge is discharged daily, so that the heterotrophic nitrite reduction activity of the sludge in the reactor is less than 1 / 3 of the autotrophic nitrite reduction activity.

[0013] Furthermore, the daily discharge of a certain mass of flocculent sludge involves passing the reactor sludge through a 0.2mm micro-sieve; sludge with a particle size below 0.2mm is discharged, while sludge with a particle size above 0.2mm is returned to the reactor. The mass of discharged flocculent sludge (gVSS) is calculated as: Q*(CODc*0.54+CODv*0.41) / 1.42, where Q is the influent flow rate (L / d) of the upflow anaerobic ammonia oxidation reactor. -1 CODc is the concentration of soluble carbohydrates (g COD L). - 1) CODv is the concentration of soluble volatile acids (g COD L). -1 ).

[0014] The calculation method for the autotrophic denitrification contribution (%) is 2.06*(NH4) + -N 进 -NH4 + -N 出 ) / (TN 进 -TN 出 )*100.

[0015] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following: the method of the present invention can increase the autotrophic denitrification contribution of the anammox granular sludge reactor to more than 75% and the effluent meets the Class A discharge standard for urban sewage, and has the advantages of flexibility, high efficiency and wide applicability. (iv) Description of the attached drawings

[0016] Figure 1 The contribution of mainstream mixed-culture anammox sludge to carbon-nitrogen conversion and autotrophic denitrification; a represents the contribution of anammox sludge taken from the reactor during non-sludge discharge operation to carbon-nitrogen conversion and autotrophic denitrification; b represents the contribution of anammox sludge taken from the reactor to carbon-nitrogen conversion and autotrophic denitrification after discharging 0.47g VSS flocculent sludge per day.

[0017] Figure 2 Nitrogen concentration in effluent from mainstream co-culture anaerobic ammonia oxidation reactors (a) and their contribution to autotrophic denitrification (b). (V) Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0019] Example 1: A method to improve the autotrophic nitrogen removal contribution of the mainstream anaerobic ammonium oxidation granular sludge process in a mixed-culture system.

[0020] 1) For simulated urban wastewater, where dissolved organic matter accounts for 40% and total nitrogen (TN) is approximately 70 mg / L. -1First, a high-load activated sludge process is used for carbon control, resulting in effluent ammonia nitrogen levels of 60–70 mg / L. -1 Dissolved organic matter 140-160 mg CODL -1 Dissolved organic matter accounts for 85% of the total organic matter, with carbohydrates and volatile acids in a 1:1 ratio.

[0021] 2) After carbon control treatment, 60% of the wastewater volume will be subjected to oxygen-limited aeration treatment (dissolved oxygen <0.5 mg / L). -1 This process oxidizes over 90% of ammonia nitrogen into nitrite and nitrate, which are then mixed with the remaining 40% and pumped into an upflow anaerobic sludge blanket reactor (effective volume 0.5L). The inoculum sludge is taken from mature anaerobic ammonia oxidation granular sludge that has been cultured for a long time, with an initial sludge concentration of 7.0 g VSS L. -1 It operates at 10–20℃. At this temperature, the influent ammonia nitrogen level in the anaerobic ammonia oxidation reactor is 27–33 mg / L. -1 Nitrite 37-43 mg / L -1 Dissolved organic matter 60-70 mg COD L -1 The ratio of total COD from carbohydrates and volatile acids to ammonia nitrogen was between 1.0 and 1.5.

[0022] 3) The contribution of anaerobic ammonium oxidation sludge taken from the reactor to carbon and nitrogen conversion and autotrophic denitrification during non-sludge discharge operation is as follows: Figure 1 As shown in (a), the maximum autotrophic contribution rate is 60%, and the effluent ammonia nitrogen is >10 mg / L. -1 The reactor sludge is passed through a 0.2mm micro-sieve daily. Sludge particles smaller than 0.2mm are discharged, while those larger than 0.2mm are returned to the reactor. After discharging 0.47g of VSS flocculent sludge daily, the contribution of the anaerobic ammonia oxidation sludge taken from the reactor to carbon-nitrogen conversion and autotrophic denitrification is as follows: Figure 1 As shown in (b), the maximum autotrophic contribution rate can reach 79.5%, and the effluent ammonia nitrogen is <2.5 mg / L. -1 .

[0023] The mass of discharged flocculent sludge (gVSS) is calculated as follows: Q*(CODc*0.54+CODv*0.41) / 1.42, where Q is the influent flow rate (L / d) of the upflow anaerobic ammonia oxidation reactor. -1 CODc is the concentration of soluble carbohydrates (gCODL). -1 CODv is the concentration of soluble volatile acids (g COD L). -1 ).

[0024] Example 2: A method to improve the autotrophic nitrogen removal contribution of the mainstream anaerobic ammonium oxidation granular sludge process in a mixed-culture system.

[0025] 1) For simulated urban wastewater, where dissolved organic matter accounts for 60% and total nitrogen (TN) is approximately 70 mg / L. -1 First, based on the organic matter composition of the influent urban sewage, a precision screening and filtration process is used for carbon control pretreatment, resulting in an effluent ammonia nitrogen level of 60–70 mg / L. -1 Dissolved organic matter 70-80 mg COD L -1 Dissolved organic matter accounts for more than 80% of the total organic matter in wastewater, with carbohydrates and volatile acids in a 1:1 ratio.

[0026] 2) After carbon control treatment, 50% of the wastewater volume will be subjected to oxygen-limited aeration treatment (dissolved oxygen <0.5 mg / L). -1 This process oxidizes over 90% of ammonia nitrogen into nitrite and nitrate nitrogen, which are then mixed with the remaining 50% and pumped into an upflow anaerobic sludge blanket reactor (effective volume 0.5L) R2. The inoculated sludge is taken from mature anaerobic ammonia oxidation granular sludge that has been cultured for a long time, with an initial sludge concentration of 7.0 g VSS L. -1 It operates at 10–20℃. At this temperature, the influent ammonia nitrogen level in the anaerobic ammonia oxidation granular sludge reactor is 40–50 mg / L. -1 Nitrite 28-34 mg / L -1 Dissolved organic matter 20-25 mg COD L -1 The ratio of total COD (carbohydrates and volatile acids) to ammonia nitrogen in the influent was 0.5. After a period of operation, the contribution of the anaerobic ammonia oxidation sludge removed from the reactor to carbon-nitrogen conversion and autotrophic denitrification was as follows: Figure 2 As shown in R2, the ratio of total COD of carbohydrates and volatile acids to ammonia nitrogen in the influent of the upflow anaerobic ammonia oxidation reactor R1 is 0.

[0027] The anaerobic ammonia oxidation sludge extracted from reactor R2 has an autotrophic contribution rate of up to 86%, and the effluent ammonia nitrogen is <4 mg / L. -1 .

Claims

1. A method for improving the autotrophic denitrification contribution of a polyculture type mainstream anammox granular sludge process, characterized in that, The method includes the following steps: 1) Pre-treating urban wastewater with carbon control to regulate the content of dissolved organic matter and its ratio to total nitrogen, thereby improving the quality of the wastewater carbon source; the carbon control pre-treatment method is as follows: when the proportion of dissolved organic matter in urban wastewater to total COD is <30%, 30~ When the concentration of dissolved organic matter in the wastewater is 50% or greater than 50%, chemically enhanced primary treatment, high-load activated sludge contact-stabilization treatment, and precision screening and filtration treatment are adopted respectively to increase the proportion of dissolved organic matter in the wastewater to more than 80% of the total organic matter, and the ratio of dissolved organic matter to total nitrogen is controlled within the range of 1.0~2.5:1; 2) Part of the wastewater after carbon control pretreatment is subjected to oxygen-limited aeration treatment, and after being mixed with the un-aerated wastewater to optimize the nitrogen composition of the wastewater, it is then pumped into the upflow anaerobic ammonia oxidation reactor; 3) The directional sludge discharge based on micro-screening is used to limit the nitrite reduction activity mediated by heterotrophic denitrifying bacteria in the upflow anaerobic ammonia oxidation granular sludge reactor: when the ratio of carbohydrate and volatile acid concentrations to ammonia nitrogen concentration in the influent of the upflow anaerobic ammonia oxidation granular sludge reactor is >0.

5. When g-COD / gN is constant, a certain mass of flocculent sludge is discharged daily to reduce the heterotrophic nitrite reduction activity of the sludge in the reactor to less than 1 / 3 of the autotrophic nitrite reduction activity. The daily discharge of a certain mass of flocculent sludge involves passing the reactor sludge through a 0.2 mm microsieve; sludge with a particle size below 0.2 mm is discharged, while sludge with a particle size above 0.2 mm is returned to the reactor. The mass of the discharged flocculent sludge is calculated as: Q*(CODc*0.54+CODv*0.41) / 1.42, where Q is the influent flow rate (L / d) of the upflow anaerobic ammonia oxidation reactor. -1 CODc is the concentration of soluble carbohydrates (gCOD L). -1 CODv is the concentration of soluble volatile acids in g COD L. -1 .

2. The method of claim 1, wherein, In step 2), 50-70% of the wastewater after the carbon control pretreatment in step 1) is subjected to limited oxygen aeration treatment so that more than 90% of the ammonia nitrogen is oxidized into nitrate nitrogen and nitrite nitrogen.

3. The method of claim 2, wherein, If the concentration of ammonia nitrogen in the effluent of the upflow anaerobic ammonia oxidation reactor is higher than 5 mg L -1 and the sum of the concentrations of nitrite nitrogen and nitrate nitrogen is lower than 2 mg L -1 , the proportion of wastewater subjected to limited oxygen aeration treatment is up-regulated in the range of 50-70%.

4. The method of claim 1, wherein, When the ratio of the concentration of carbohydrates and volatile acids to the concentration of ammonia nitrogen after the pretreatment in step 1) is higher than 1.5 g-COD / g-N, by 0.1, the ratio of the concentrations of nitrate nitrogen and nitrite nitrogen is increased by 0.03 by extending the limited oxygen aeration time.

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