Wastewater denitrification system and wastewater denitrification process

Abstract

The present invention belongs to the field of sewage treatment and discloses a wastewater denitrification system, including a nitrification tank, a denitrification tank, a regulating tank and an NDFO-Feammox tank. The sewage treated in the nitrification tank and the denitrification tank can provide nitric nitrogen and ammonia nitrogen for NDFO-Feammox. The circulation of divalent iron and trivalent iron drives the NDFO-Feammox coupling system to achieve denitrification. Zero-valent iron absorbs oxygen and corrodes to form divalent iron, and divalent iron reacts with oxygen to form trivalent iron. These two reactions consume dissolved oxygen in the water, which is conducive to the formation of an anaerobic environment, thereby improving the denitrification performance of the system and further improving the impurity removal effect of sewage. In addition, the present invention also discloses a wastewater denitrification process.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, relates to the field of sewage biological treatment, and particularly relates to a wastewater denitrification system and a wastewater denitrification process. Background Art

[0002] The traditional biological denitrification process is centered around nitrification and denitrification. Nitrification is the oxidation of ammonia nitrogen to nitrite by ammonia oxidizing bacteria (AOB) under aerobic conditions, followed by the oxidation of nitrite to nitrate by nitrite oxidizing bacteria (NOB); denitrification is the reduction of nitrate or nitrite to nitrogen gas by denitrifying bacteria under anoxic conditions.

[0003] Based on the principle of nitrification and denitrification, traditional biological denitrification processes mainly include: sequencing batch activated sludge process (SBR), anoxic / aerobic (A / O) process, anaerobic / anoxic / aerobic (A / A / O) process, oxidation ditch process, UCT process, Bardenpho process, decarbonization / nitrification / denitrification (Barth) process, etc.

[0004] The above-mentioned traditional biological denitrification process suffers from unsatisfactory denitrification effects and low treatment efficiency when treating low-ammonia nitrogen and low-COD wastewater. Furthermore, with the implementation of new wastewater discharge standards, such as the "Synthetic Ammonia Industrial Water Pollutant Discharge Standard" and the "Municipal Wastewater Treatment Plant Pollutant Discharge Standard," the discharge requirements for TN in wastewater have become more stringent. Traditional biological denitrification processes are gradually failing to meet the requirements of these new standards. Therefore, improvements to denitrification processes are urgently needed. Summary of the Invention

[0005] In view of the above problems existing in the prior art, in a first aspect, the present invention provides a wastewater denitrification system; in a second aspect, the present invention provides a wastewater denitrification process.

[0006] In a first aspect, the present invention provides a wastewater denitrification system, comprising a nitrification tank, a denitrification tank, a regulating tank and an NDFO-Feammox tank, wherein the nitrification tank is provided with a nitrification water inlet, a nitrification water outlet 1 and a nitrification water outlet 2; the denitrification tank is provided with a denitrification water inlet 1, a denitrification water inlet 2 and a denitrification water outlet; low-ammonia nitrogen wastewater enters the nitrification tank through the nitrification water inlet and enters the denitrification tank through the denitrification water inlet 1; the nitrification water outlet 1 is connected to the denitrification water inlet 2, the nitrification water outlet 2 and the denitrification water outlet are both connected to the regulating tank, and the regulating tank is connected to the NDFO-Feammox tank.

[0007] Preferably, a suspended carrier is provided in the NDFO-Feammox pool.

[0008] Preferably, the suspension carrier filling rate in the NDFO-Feammox pool is 70-85%.

[0009] Preferably, a sludge biofilm formation structure is further provided in the NDFO-Feammox tank.

[0010] In a second aspect, the present invention provides a wastewater denitrification process comprising the following steps:

[0011] Step 1: low ammonia nitrogen wastewater flows into the nitrification tank for reaction to obtain nitrified effluent;

[0012] Step 2: a portion of the nitrification effluent flows into the regulating tank, and another portion of the nitrification effluent flows into the denitrification tank; at the same time, low-ammonia nitrogen wastewater is introduced into the denitrification tank, the low-ammonia nitrogen wastewater and the nitrification effluent are mixed, and a denitrification reaction is carried out in the denitrification tank to obtain denitrification effluent;

[0013] Step 3: The denitrification effluent enters the regulating tank and is mixed with the nitrification effluent to adjust the pH value in the regulating tank to obtain regulated effluent;

[0014] Step 4: Adjust the effluent to enter the NDFO-Feammox tank, add zero-valent iron into the NDFO-Feammox tank, and react;

[0015] Step 5: Test the effluent from the NDFO-Feammox pool. If the effluent does not meet the standards, mix the effluent from the NDFO-Feammox pool with low ammonia nitrogen wastewater and repeat steps 1 to 4.

[0016] Preferably, in step 3, the pH value of the effluent is adjusted to 6.8-7.2.

[0017] Preferably, in step 1, the pH value of the reaction system in the nitrification tank is 7.0-7.5, the temperature is 20-30° C., and the reaction time is 4.5-5.5 h.

[0018] Preferably, in step 2, the pH value of the reaction system in the denitrification tank is 6.5-8.5, the temperature is 20-30° C., and the reaction time is 1.5-2.5 h.

[0019] Preferably, in step 4, the temperature of the reaction system in the NDFO-Feammox pool is 20-30° C., and the reaction time is 20-24 h.

[0020] Preferably, in the denitrification tank, the volume ratio of low ammonia nitrogen wastewater to nitrification effluent is 2.0-3.0:1.

[0021] Preferably, in the regulating tank, the volume ratio of denitrification effluent to nitrification effluent is 5.0-7.5:1.

[0022] Preferably, the dissolved oxygen in the NAFO-Feammx tank is 0-0.5 mg / L.

[0023] Compared with the prior art, the present invention has the following obvious beneficial technical effects:

[0024] (1) This system helps to improve the contribution of heterotrophic denitrification to denitrification, and achieves lower aeration requirements on the basis of avoiding the addition of external carbon sources. Part of the low-ammonia nitrogen wastewater flows to the nitrification tank, and ammonia nitrogen oxidation is achieved under low aeration volume. Part of the effluent from the nitrification tank enters the denitrification tank, and the remaining effluent enters the regulating tank. The wastewater that needs to be treated in the denitrification tank includes the effluent from the nitrification tank and the low-ammonia nitrogen wastewater. The mixture of the two helps to improve the utilization rate of the organic carbon source in the low-ammonia nitrogen wastewater and improve the nitrate nitrogen reduction effect in the denitrification tank, thereby reducing unnecessary organic carbon loss during the aeration process. The regulating tank contains residual ammonia nitrogen, nitrate nitrogen and a small amount of COD from the effluent of the nitrification tank and the effluent of the denitrification tank. After treatment in the regulating tank, it flows to the NDFO-Feammox tank for deep treatment.

[0025] In the NDFO-Feammox coupled system, zero-valent iron balls slowly release ferrous iron to remove nitrate from wastewater through the NDFO process, while also providing the ferric iron required for the Feammox process to oxidize ammonia nitrogen. Since ferrous iron is a product of the Feammox process, the NDFO-Feammox coupled system can be driven by the iron cycle to achieve simultaneous removal of ammonia nitrogen and nitrate nitrogen. In this process, dissolved oxygen in the water and the effluent from the nitrification tank are sufficient to drive the Feammox process through ferrous oxidation, effectively resolving the problem of insufficient electron acceptors required by Feammox in low-nitrate wastewater environments. Furthermore, the chemical oxidation of ferrous iron helps maintain an anaerobic microenvironment, further enhancing wastewater denitrification.

[0026] (2) The sewage treated in the nitrification tank enters the denitrification tank and undergoes denitrification reaction together with the low ammonia nitrogen sewage. The sewage treated in the nitrification tank provides nitric nitrogen and the remaining unconsumed organic carbon source (COD) for the denitrification tank, and the low ammonia nitrogen wastewater provides the organic carbon source (COD) for the nitrification tank. The organic carbon sources in the low ammonia nitrogen wastewater and the sewage in the nitrification tank are fully utilized, thereby reducing the cost of organic carbon sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic flow chart of the wastewater denitrification process provided by the present invention. DETAILED DESCRIPTION

[0028] The present invention provides the following specific technical solutions.

[0029] In a first aspect, the present invention provides a wastewater denitrification system, comprising a nitrification tank, a denitrification tank, a regulating tank and an NDFO-Feammox tank, wherein the nitrification tank is provided with a nitrification water inlet, a nitrification water outlet 1 and a nitrification water outlet 2; the denitrification tank is provided with a denitrification water inlet 1, a denitrification water inlet 2 and a denitrification water outlet; low-ammonia nitrogen wastewater enters the nitrification tank through the nitrification water inlet and enters the denitrification tank through the denitrification water inlet 1; the nitrification water outlet 1 is connected to the denitrification water inlet 2, the nitrification water outlet 2 and the denitrification water outlet are both connected to the regulating tank, and the regulating tank is connected to the NDFO-Feammox tank.

[0030] NDFO-Feammox is the process of nitrate-based anaerobic ferrous oxidation and iron-ammonia oxidation. NAFO (nitrate-based anaerobic iron oxidation) refers to the process in which microorganisms use nitrate or nitrite as electron acceptors to oxidize low-valent iron (ferrous iron or zero-valent iron) to high-valent iron (ferric iron) under anaerobic conditions. Feammox refers to the process of iron reduction combined with ammonia oxidation driven by microorganisms under anaerobic conditions. In this process, NH4 + and ferric iron act as electron donors and electron acceptors respectively. The ferric iron is reduced to ferrous iron, while NH4 + It is converted into nitrite (NO2 - ), nitrate (NO3 - ) and nitrogen (N2) in different forms.

[0031] When using the above wastewater denitrification system, wastewater with low ammonia nitrogen and low COD enters the nitrification tank and denitrification tank respectively for reaction. Part of the nitrification effluent from the nitrification tank enters the denitrification tank and mixes with the wastewater with low ammonia nitrogen and low COD. Part of the nitrification effluent enters the regulating tank. The wastewater from the denitrification tank is treated and then enters the regulating tank. It is mixed with the nitrification effluent in the regulating tank and, after treatment in the regulating tank, enters the NDFO-Feammox tank. The inventors have found that the above wastewater denitrification system has a good denitrification effect on wastewater with low ammonia nitrogen and low COD, which is beneficial to environmental protection.

[0032] Preferably, a suspended carrier is provided in each of the NDFO-Feammox pools.

[0033] The inventors have found that providing a landing point for the bacterial colony in the NDFO-Feammox suspension carrier pool facilitates bacterial growth. In practical applications, parameters such as the specific surface area, filling rate, and density of the suspension carrier can be adjusted according to actual conditions.

[0034] Further preferably, the suspended carrier in the NDFO-Feammox pool is spherical.

[0035] Preferably, the filling rate of the suspended carrier in the NDFO-Feammox pool is 70-85%, and the suspended carrier in the NDFO-Feammox pool is filled with iron balls.

[0036] The inventors discovered through research that the gaps between the zero-valent iron (iron balls) help iron-ammonia oxidizing bacteria enter the suspended balls to carry out the Feammox reaction, shortening the distance between the iron source and the microorganisms and accelerating their electron transfer rate.

[0037] Preferably, a sludge biofilm formation structure is further provided in the NDFO-Feammox tank.

[0038] Setting up a sludge biofilm structure is beneficial to the growth of functional bacteria.

[0039] In a second aspect, the present invention provides a wastewater denitrification process comprising the following steps:

[0040] Step 1: low ammonia nitrogen wastewater flows into the nitrification tank for reaction to obtain nitrified effluent;

[0041] Step 2: a portion of the nitrification effluent flows into a regulating tank, and another portion of the nitrification effluent flows into a denitrification tank, low-ammonia nitrogen wastewater is introduced into the denitrification tank, the low-ammonia nitrogen wastewater and the nitrification effluent are mixed, and a denitrification reaction is carried out in the denitrification tank to obtain denitrification effluent;

[0042] Step 3: The denitrification effluent enters the regulating tank and is mixed with the nitrification effluent to adjust the pH value in the regulating tank to obtain regulated effluent;

[0043] Step 4: Adjust the effluent to enter the NDFO-Feammox tank, add zero-valent iron into the NDFO-Feammox tank, and react;

[0044] Step 5: Test the effluent from the NDFO-Feammox pool. If the effluent does not meet the standards, mix the effluent from the NDFO-Feammox pool with low ammonia nitrogen wastewater and repeat steps 1 to 4.

[0045] The inventors have found through research that the sewage treated in the nitrification tank enters the denitrification tank and undergoes denitrification reaction together with the low-ammonia nitrogen sewage. The sewage treated in the nitrification tank provides nitric nitrogen and the remaining unconsumed organic carbon source for the denitrification tank, and the low-ammonia nitrogen wastewater provides the organic carbon source for the nitrification tank. The organic carbon sources in the low-ammonia nitrogen wastewater and the nitrification tank sewage are fully utilized, thereby reducing the cost of the organic carbon source.

[0046] The inventors further discovered that the NDFO (iron oxidation reaction) and Feammox (ammonium NH4 + With iron ion Fe 3+The coupled redox reactions further regulate ammonia and nitrate in the effluent. Wastewater treated in the nitrification and denitrification tanks provides nitrate and ammonia nitrogen for the NDFO-Feammox reaction. In the NDFO-Feammox coupled system, the zero-valent iron pellets first slowly release ferrous iron to remove nitrates in the NDFO process and then provide the ferric iron required for the Feammox process to oxidize ammonia nitrogen. Since ferrous iron is a product of the Feammox process, the iron cycle drives the NDFO-Feammox coupled system to simultaneously remove ammonia and nitrate nitrogen. In this process, aerated effluent from low-ammonia wastewater and the nitrification tank can also drive the Feammox process through ferrous iron oxidation, effectively resolving the problem of insufficient electron acceptors required for Feammox in low-nitrate wastewater environments. Furthermore, the oxidation of ferrous iron helps maintain an anaerobic microenvironment, further enhancing wastewater denitrification.

[0047] Preferably, the pH value of the reaction system in the nitrification tank is 7.0-7.5.

[0048] Preferably, the pH value of the reaction system in the denitrification tank is 6.5-8.5.

[0049] Preferably, in step 3, the pH value of the effluent is adjusted to 6.8-7.2.

[0050] In practical applications, the pH values ​​of the reaction systems in the nitrification tank, the denitrification tank, and the effluent can be adjusted based on actual needs. The pH of the environment influences the activity of functional bacteria. Excessively high or low pH can alter the charge of the cell membranes of these bacteria, affecting their ability to absorb nutrients and the activity of enzymes involved in metabolism. Adjusting the pH also modulates the toxicity of harmful substances in the effluent, facilitating their absorption and decomposition of ammonia nitrogen. Therefore, adjusting the pH based on the characteristics of the functional bacteria in the nitrification and denitrification tanks ensures a stable environment for these bacteria and ensures effective denitrification.

[0051] Preferably, in the denitrification tank, the volume ratio of low ammonia nitrogen wastewater to nitrification effluent is 2.0-3.0:1.

[0052] In practical applications, the amount of low-ammonia nitrogen wastewater and nitrification effluent entering the denitrification tank can be adjusted according to actual conditions. The majority of the low-ammonia nitrogen wastewater flows into the denitrification tank primarily to provide an organic carbon source for the denitrification process. If all low-ammonia nitrogen wastewater flows directly from the nitrification tank into the denitrification tank, the nitrification tank will consume some of the organic carbon source, resulting in a waste of organic carbon source. By adjusting the ratio of low-ammonia nitrogen wastewater to digestion effluent in the denitrification tank, the organic carbon source in the wastewater can be maximized to participate in the denitrification reaction rather than being consumed by the aeration process in the nitrification tank. If the organic carbon content of the wastewater entering the denitrification tank meets the denitrification tank's requirements, the ratio of low-ammonia nitrogen wastewater entering the nitrification tank can be appropriately increased. If the organic carbon content cannot meet the denitrification tank's requirements, the ratio of low-ammonia nitrogen wastewater entering the nitrification tank can be appropriately reduced. If not, the amount of low-ammonia nitrogen wastewater entering the nitrification tank can be reduced. In the denitrification tank, the volume ratio of low-ammonia nitrogen wastewater to nitrification effluent of 2.0 to 3.0:1 is only a preferred range given by the inventors.

[0053] Preferably, in the regulating tank, the volume ratio of denitrification effluent to nitrification effluent is 5.0-7.5:1.

[0054] Preferably, the temperature of the reaction system in the nitrification tank is 20-30°C.

[0055] Preferably, the temperature of the reaction system in the denitrification tank is 20-30°C.

[0056] Preferably, the temperature of the reaction system in the NDFO-Feammox pool is 20-35°C.

[0057] In actual application, the temperature of the reaction system in the nitrification tank, denitrification tank, and NDFO-Feammox tank can be adjusted according to the characteristics of the functional bacteria used. In a specific embodiment of the present invention, the temperature of the reaction system in the nitrification tank is 20-30°C, the temperature of the reaction system in the denitrification tank is 20-30°C, and the temperature of the reaction system in the NDFO-Feammox tank is 20-35°C. These are the preferred ranges proposed by the inventors based on the characteristics of the functional bacteria used.

[0058] Preferably, the dissolved oxygen in the NAFO-Feammx tank is 0-0.5 mg / L.

[0059] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention clearer, they will be described in detail below with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0060] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0061] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0062] Example 1:

[0063] A wastewater denitrification process comprises the following steps:

[0064] Step 1, the preparation phase, involves installing suspended carriers in the nitrification tank, denitrification tank, and NDFO-Feammox tank. The suspended carriers in the NDFO-Feammox tank are filled with ductile iron (ductile iron) at a fill rate of 75%, and a sludge biofilm formation structure is configured in the NDFO-Feammox tank.

[0065] Step 2: Detect the COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the low-ammonia nitrogen wastewater.

[0066] Step 3: 4 L of low-ammonia nitrogen wastewater with a C / N ratio of 1 is flowed into the nitrification tank for nitrification reaction. The pH value of the reaction system is 7.3, and the reaction is carried out at 25° C. for 4 hours to obtain nitrified effluent;

[0067] Step 4: 1.6 L of nitrification effluent flows into the regulating tank, 2.4 L of nitrification effluent flows into the denitrification tank, and 6 L of low-ammonia nitrogen wastewater is introduced into the denitrification tank. The low-ammonia nitrogen wastewater and nitrification effluent are mixed. The pH value of the reaction system is 7.5. After reacting at 25°C for 2 hours, denitrification effluent is obtained.

[0068] Step 5: 8.4 L of denitrification effluent enters the regulating tank and is mixed with the nitrification effluent. The pH value in the regulating tank is adjusted to 7.0 to obtain regulated effluent.

[0069] Step 6: The effluent is regulated to enter the NDFO-Feammox tank, reacted at 30°C for 22 hours, and the wastewater treatment is completed and discharged;

[0070] Step 7: Detect the effluent COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the NDFO-Feammox pool.

[0071] Example 2:

[0072] A wastewater denitrification process comprises the following steps:

[0073] Step 1, the preparation phase, involves installing suspended carriers in the nitrification tank, denitrification tank, and NDFO-Feammox tank. The suspended carriers in the NDFO-Feammox tank are filled with ductile iron (ductile iron) at a fill rate of 75%, and a sludge biofilm formation structure is configured in the NDFO-Feammox tank.

[0074] Step 2: Detect the COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the low-ammonia nitrogen wastewater.

[0075] Step 3: 4 L of low-ammonia nitrogen wastewater with a C / N ratio of 1 is flowed into the nitrification tank for nitrification reaction. The pH value of the reaction system is 7.3, and the reaction is carried out at 25° C. for 5 hours to obtain nitrified effluent.

[0076] Step 4: 1.2 L of nitrification effluent flows into the regulating tank, 2.8 L of nitrification effluent flows into the denitrification tank, and 6 L of low-ammonia nitrogen wastewater is introduced into the denitrification tank. The low-ammonia nitrogen wastewater and nitrification effluent are mixed. The pH value of the reaction system is 7.5. After reacting at 25°C for 2 hours, denitrification effluent is obtained.

[0077] Step 5: 8.8 L of denitrification effluent enters the regulating tank and is mixed with the nitrification effluent. The pH value in the regulating tank is adjusted to 7.0 to obtain regulated effluent.

[0078] Step 6: The effluent is regulated to enter the NDFO-Feammox tank, reacted at 30°C for 22 hours, and the wastewater treatment is completed and discharged;

[0079] Step 7: Detect the effluent COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the NDFO-Feammox pool.

[0080] Example 3:

[0081] A wastewater denitrification process comprises the following steps:

[0082] Step 1, the preparation phase, involves installing suspended carriers in the nitrification tank, denitrification tank, and NDFO-Feammox tank. The suspended carriers in the NDFO-Feammox tank are filled with ductile iron (ductile iron) at a fill rate of 75%, and a sludge biofilm formation structure is configured in the NDFO-Feammox tank.

[0083] Step 2: Detect the COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the low-ammonia nitrogen wastewater.

[0084] Step 3: 4 L of low-ammonia nitrogen wastewater with a C / N ratio of 1.2 is flowed into the nitrification tank for nitrification reaction. The pH value of the reaction system is 7.5, and the reaction is carried out at 25° C. for 5 hours to obtain nitrified effluent.

[0085] Step 4: 1.2 L of nitrification effluent flows into the regulating tank, 2.8 L of nitrification effluent flows into the denitrification tank, and 6 L of low-ammonia nitrogen wastewater is introduced into the denitrification tank. The low-ammonia nitrogen wastewater and nitrification effluent are mixed. The pH value of the reaction system is 7.5. After reacting at 25°C for 5 hours, denitrification effluent is obtained.

[0086] Step 5: 8.8 L of denitrification effluent enters the regulating tank and is mixed with the nitrification effluent. The pH value in the regulating tank is adjusted to 7.0 to obtain regulated effluent.

[0087] Step 6: The effluent is regulated to enter the NDFO-Feammox tank, reacted at 25°C for 22 hours, and the wastewater treatment is completed and discharged;

[0088] Step 7: Detect the effluent COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the NDFO-Feammox pool.

[0089] Comparative Example 1:

[0090] Step 1, the preparation phase, involves installing suspended carriers in the nitrification tank, denitrification tank, and NDFO-Feammox tank. The suspended carriers in the NDFO-Feammox tank are filled with ductile iron (ductile iron) at a fill rate of 75%, and a sludge biofilm formation structure is configured in the NDFO-Feammox tank.

[0091] Step 2: Detect the COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the low-ammonia nitrogen wastewater.

[0092] Step 3: 10 L of low-ammonia nitrogen wastewater with a C / N ratio of 1 is flowed into the nitrification tank for nitrification reaction. The pH value of the reaction system is 7.3, and the reaction is carried out at 25° C. for 4 hours to obtain nitrified effluent.

[0093] In step 4, all nitrification effluents flow directly into the denitrification tank, the pH value of the reaction system is 7.5, and the reaction is carried out at 25°C for 2 hours.

[0094] Step 5: All denitrification effluent enters the regulating pool, and the pH value in the regulating pool is adjusted to 7.0 to obtain the regulating pool effluent.

[0095] Step 6: Detect the COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the effluent from the equalization tank.

[0096] Comparative Example 2:

[0097] The difference from Comparative Example 1 is that an organic carbon source of 150 mg / L sodium acetate is added in step 4.

[0098] The COD concentration, TN (total nitrogen) concentration, ammonia-nitrogen concentration, and C / N value of the low-ammonia nitrogen wastewater used in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0099] Detection data of low ammonia nitrogen wastewater used in Examples 1 to 3 and Comparative Example 1

[0100]

[0101] The COD concentration, TN (total nitrogen) concentration, and ammonia-nitrogen concentration of the effluent from the NDFO-Feammox tank in Examples 1 to 3 and the effluent from the regulating tank in Comparative Examples 1 to 2 are shown in Table 2.

[0102] Table 2 - Test data of the effluent from the NDFO-Feammox pool in Examples 1 to 3 and the effluent from the regulating pool in Comparative Examples 1 to 2

[0103]

[0104] The direct emission limits under the "Water Pollutant Discharge Standard for Synthetic Ammonia Industry" (GB13458-2013) are: ammonia-nitrogen concentration ≤ 15 mg / L; COD ≤ 50 mg / L; and TN ≤ 25 mg / L. The primary emission standards for wastewater under the "Pollutant Discharge Standard for Municipal Wastewater Treatment Plants" (GB 18918-2002) are: COD ≤ 50 mg / L; ammonia-nitrogen concentration ≤ 5 mg / L; and TN ≤ 15 mg / L. As shown in Table 1, the wastewater treated by the wastewater denitrification process provided by the present invention meets the requirements of both the "Water Pollutant Discharge Standard for Synthetic Ammonia Industry" and the "Pollutant Discharge Standard for Municipal Wastewater Treatment Plants." A comparison of the TN (total nitrogen) concentrations in the denitrified water treated in Examples 1-3 and Comparative Example 1 demonstrates that the denitrification process provided by the present invention is more effective for denitrifying wastewater with low ammonia nitrogen and low COD levels.

[0105] By comparing Examples 1 to 3 and Comparative Examples 1 to 2, it can be seen that if the wastewater in the regulating tank has not been treated in the NDFO-Feammox tank, an external organic carbon source is required to improve the denitrification effect.

[0106] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A wastewater denitrification system, characterized in that: The invention comprises a nitrification tank, a denitrification tank, a regulating tank and an NDFO-Feammox tank. The nitrification tank is provided with a nitrification water inlet, a nitrification water outlet 1 and a nitrification water outlet 2; the denitrification tank is provided with a denitrification water inlet 1, a denitrification water inlet 2 and a denitrification water outlet; low-ammonia nitrogen wastewater enters the nitrification tank through the nitrification water inlet and enters the denitrification tank through the denitrification water inlet 1; the nitrification water outlet 1 is connected to the denitrification water inlet 2, the nitrification water outlet 2 and the denitrification water outlet are both connected to the regulating tank, and the regulating tank is connected to the NDFO-Feammox tank.

2. The wastewater denitrification system according to claim 1, characterized in that: The NDFO-Feammox pools are all provided with suspended carriers.

3. The wastewater denitrification system according to claim 2, characterized in that: The filling rate of the suspended carrier in the NDFO-Feammox pool is 70-85%.

4. The wastewater denitrification system according to claim 1 or 2, characterized in that: The NDFO-Feammox pool is also provided with a sludge film forming structure.

5. A wastewater denitrification process, characterized in that: The steps include: Step 1: low ammonia nitrogen wastewater flows into the nitrification tank for reaction to obtain nitrified effluent; Step 2: a portion of the nitrification effluent flows into the regulating tank, and another portion of the nitrification effluent flows into the denitrification tank; at the same time, low-ammonia nitrogen wastewater is introduced into the denitrification tank, the low-ammonia nitrogen wastewater and the nitrification effluent are mixed, and a denitrification reaction is carried out in the denitrification tank to obtain denitrification effluent; Step 3: The denitrification effluent enters the regulating tank and is mixed with the nitrification effluent to adjust the pH value in the regulating tank to obtain regulated effluent; Step 4, adjusting the effluent to enter the NDFO-Feammox pool, adding zero-valent iron to the NDFO-Feammox pool, reacting, and detecting the effluent of the NDFO-Feammox pool; Step 5: If the effluent from the NDFO-Feammox pool does not meet the standards, mix the effluent from the NDFO-Feammox pool with low ammonia nitrogen wastewater and repeat steps 1 to 4 until the effluent from the NDFO-Feammox pool meets the standards.

6. The wastewater denitrification process according to claim 5, characterized in that: In step 3, the pH value of the effluent is adjusted to 6.8-7.

2.

7. The wastewater denitrification process according to claim 5, characterized in that: In step 1, the pH value of the reaction system in the nitrification tank is 7.0-7.5, the temperature is 20-30° C., and the reaction time is 4.5-5.5 h.

8. The wastewater denitrification process according to claim 5 or 7, wherein: In step 2, the pH value of the reaction system in the denitrification tank is 6.5-8.5, the temperature is 20-30° C., and the reaction time is 1.5-2.5 h.

9. The wastewater denitrification process according to claim 5 or 7, wherein: In step 4, the temperature of the reaction system in the NDFO-Feammox pool is 20-30° C., and the reaction time is 20-24 h.

10. The wastewater denitrification process according to claim 5 or 6, characterized in that: In the denitrification tank, the volume ratio of low ammonia nitrogen wastewater to nitrification effluent is 2.0-3.0:1; in the regulating tank, the volume ratio of denitrification effluent to nitrification effluent is 5.0-7.5:1.

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