A low ammonia-nitrogen wastewater treatment method based on iron-loaded particle activated carbon coupled with an anaerobic fluidized bed membrane bioreactor, a reaction system and application

Abstract

The application belongs to the technical field of sewage treatment, and particularly relates to a low-ammonia-nitrogen wastewater treatment method based on an iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor, a reaction system and application. The low-ammonia-nitrogen wastewater treatment method comprises the following steps: in the anaerobic fluidized bed membrane bioreactor, iron-loaded granular activated carbon is added and mixed sludge is inoculated, low-ammonia-nitrogen wastewater to be treated is introduced for denitrification treatment, the low-ammonia-nitrogen wastewater forms a liquid circulation through the action of a circulating pump in the denitrification process, the iron-loaded granular activated carbon and the mixed sludge in the reactor are in a fluidized state, and then effluent is obtained through membrane separation; the mixed sludge at least comprises nitrosation-anaerobic ammonia oxidation sludge and iron anaerobic ammonia oxidation sludge. For low-ammonia-nitrogen wastewater treatment at normal temperature, the method provided by the application enables the low-ammonia-nitrogen wastewater at normal temperature to realize good denitrification treatment effect under the synergistic action of the iron-loaded granular activated carbon and the mixed sludge.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method, reaction system, and application for treating low ammonia nitrogen wastewater based on an anaerobic fluidized bed membrane bioreactor coupled with iron-loaded granular activated carbon. Background Technology

[0002] Efficient nitrogen removal from wastewater is essential for ensuring the quality of the ecological environment. Anaerobic ammonium oxidation (Anammox) is an emerging biological nitrogen removal technology for wastewater that has received considerable attention in recent years. Anammox refers to the process by which anaerobic ammonium oxidizing bacteria (AnAOB) denitrify NO2. - As an electron acceptor, NH4 + The autotrophic denitrification process of oxidation to N2 is shown in equation (1). Compared with the traditional biological denitrification process of nitrification-denitrification wastewater, Anammox can reduce the aeration volume, does not require an external organic carbon source, and produces less residual sludge, which can significantly reduce operating costs.

[0003] NH4 + +1.32NO2 - +0.66HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.66CH2O 0.15 N 1.5 +2.0

[0004] Formula 3H2O (1)

[0005] Currently, Anammox technology is mainly applied in the engineering treatment of high-ammonia nitrogen wastewater such as landfill leachate and sludge digestion liquid, and the technology is relatively mature. However, the application of Anammox technology in treating low-ammonia nitrogen wastewater such as municipal sewage at ambient temperatures is limited. This is because, firstly, AnAOB grows slowly and has stringent requirements for temperature and other conditions, resulting in long start-up times at ambient temperatures. In the treatment of low-ammonia nitrogen wastewater such as municipal sewage, the influent temperature is often below the optimal growth range of 30-40℃ for AnAOB. ​​Increasing the temperature would significantly increase operating costs and is difficult to achieve. Secondly, the NO2 in the wastewater... - The limitations of anaerobic ammonium oxidation (ANAO) mean that it often needs to be combined with processes such as short-cut nitrification in practical applications. However, under low ammonia nitrogen concentration conditions, the NO2 produced by processes such as short-cut nitrification... - They are often unstable and easily oxidized to NO3. -This prevents the Anammox process from proceeding effectively. Therefore, to achieve the application of Anammox in the treatment of low ammonia nitrogen wastewater, it is necessary to address the issue of NO2 concentration under low ammonia nitrogen conditions. - The insufficient supply of nitrogen leads to the low efficiency of traditional anaerobic ammonia oxidation, which is a problem that needs to be addressed to improve the denitrification effect and the start-up speed of the treatment process. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing anaerobic ammonia oxidation technology in treating low ammonia nitrogen wastewater at room temperature due to NO2. - Insufficient ammonia sources lead to low efficiency and poor nitrogen removal in traditional anaerobic ammonia oxidation. This paper presents a method, reaction system, and application for treating low-ammonia-nitrogen wastewater based on iron-loaded granular activated carbon coupled with an anaerobic fluidized bed membrane bioreactor. This method is suitable for low-ammonia-nitrogen influent and when no external NO2 is added. - Under certain conditions, it can achieve efficient nitrogen removal from wastewater, improve the nitrogen removal rate, and has a fast start-up speed.

[0007] In a first aspect, the present invention provides a method for treating low ammonia nitrogen wastewater, the method comprising the following steps: adding iron-loaded granular activated carbon and inoculating mixed sludge in an anaerobic fluidized bed membrane bioreactor, introducing low ammonia nitrogen wastewater to be treated for denitrification treatment, wherein the low ammonia nitrogen wastewater forms a feed-liquid circulation through the action of a circulation pump during the denitrification process, and the iron-loaded granular activated carbon and mixed sludge in the reactor are in a fluidized state, and then obtaining effluent after membrane separation; wherein the mixed sludge comprises at least nitrification-anaerobic ammonia oxidation sludge and iron anaerobic ammonia oxidation sludge; wherein the nitrification-anaerobic ammonia oxidation sludge contains anaerobic ammonia oxidizing bacteria and nitrifying bacteria; wherein the iron anaerobic ammonia oxidation sludge contains microorganisms capable of removing ammonia nitrogen from the low ammonia nitrogen wastewater through the iron anaerobic ammonia oxidation process.

[0008] In a preferred embodiment, the amount of the mixed sludge inoculated is 25-35% of the effective volume of the reactor.

[0009] In a preferred embodiment, the sludge concentration of the mixed sludge is 20–30 mg / L.

[0010] In a preferred embodiment, the volume ratio of the nitrification-anammox sludge to the iron anammox sludge is (1.5-3):1.

[0011] In a preferred embodiment, the acclimation method for the iron-loaded anammox sludge includes: mixing iron-loaded granular activated carbon, conventional anammox sludge, and nitrogen-containing wastewater, and then acclimating and cultivating them in an anaerobic environment, wherein the initial NH4 content of the nitrogen-containing wastewater is... + -N concentration is 100-200 mg / L, NH4 + -N and NO2 -The NO2 concentration ratio was 1:(1–1.5), and NO2 was reduced in a stepwise manner at different stages of the acclimatization process. - The concentration of -N, up to NH4 + -N and NO2 - The concentration ratio of -N was set to 1:0, and the concentration of NH4 was adjusted. + When the -N concentration is 30–60 mg / L, the NH4+ in the wastewater... + The iron anammox sludge is obtained when the -N removal rate is above 50%; the conventional anammox sludge contains anammox bacteria.

[0012] In a preferred embodiment, the ratio of the iron-loaded granular activated carbon, conventional anaerobic ammonia oxidation sludge, and nitrogen-containing wastewater is (0.05-0.2) g: (0.5-1.5) mL: 2 mL.

[0013] In a preferred embodiment, the volumetric filling rate of the iron-loaded granular activated carbon in the anaerobic fluidized bed membrane bioreactor is 10-30%.

[0014] In a preferred embodiment, the ammonia nitrogen concentration of the low ammonia nitrogen wastewater is 30-60 mg / L, the temperature is 20-30°C, and the dissolved oxygen concentration is 0.1-0.4 mg / L.

[0015] In a preferred embodiment, the hydraulic retention time of the denitrification treatment is 2.5 to 24 hours.

[0016] In a preferred embodiment, the membrane flux is 4–38 L / (m²). 2 ·h).

[0017] In a preferred embodiment, the preparation method of the iron-loaded granular activated carbon includes the following steps: preparing an iron solution using a trivalent iron source and a divalent iron source, then adding granular activated carbon and an alkaline solution to obtain a mixed solution and performing a co-precipitation reaction, and obtaining the iron-loaded granular activated carbon after separation and washing.

[0018] In a preferred embodiment, the iron solution contains Fe 3+ with Fe 2+ The molar ratio is (0.5~2):1.

[0019] In a preferred embodiment, the ratio of the iron solution to the granular activated carbon is (4-6) mL:1 g.

[0020] In a preferred embodiment, the amount of alkaline solution used is such that the pH value of the mixed solution is 8 to 10.

[0021] In a preferred embodiment, the conditions for the coprecipitation reaction include: a reaction temperature of 50–70°C and a reaction time of 0.5–2 h.

[0022] In a preferred embodiment, the low ammonia nitrogen wastewater treatment method is carried out in an iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor. The iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor includes: an anaerobic reactor, iron-loaded granular activated carbon filled in the anaerobic reactor, and a membrane module disposed in the anaerobic reactor. The anaerobic reactor has a reaction zone and a separation zone that are interconnected. The reaction zone is filled with iron-loaded granular activated carbon and has a membrane module disposed therein. The anaerobic reactor has an inlet, an outlet, a circulating water inlet, and a circulating water outlet. The inlet and the circulating water inlet are connected to the reaction zone, and the circulating water outlet is connected to the separation zone. One end of the membrane module is closed and the other end is connected to the outlet. The circulating water inlet and the circulating water outlet are connected by a pipeline and a circulation pump is provided.

[0023] Secondly, the present invention also provides the application of the above-mentioned low ammonia nitrogen wastewater treatment method in the field of wastewater treatment.

[0024] This invention presents a wastewater treatment method and corresponding reaction system for low-ammonia nitrogen wastewater at room temperature, based on iron-loaded granular activated carbon coupled with an anaerobic fluidized bed membrane bioreactor (AFMBR). The low-ammonia nitrogen wastewater enters the AFMBR and is circulated through a pump. The key lies in introducing iron-loaded granular activated carbon and inoculating it with a mixed sludge comprising at least nitrification-anammox sludge and iron-containing anammox sludge. This allows for highly efficient denitrification of the low-ammonia nitrogen wastewater through the synergistic effect of the iron-loaded granular activated carbon and the mixed sludge, achieving a high denitrification rate. After denitrification, effluent is obtained through membrane separation. The reason for this is speculated to be that, under the action of the iron-containing anammox sludge, Fe(III) in the iron-loaded granular activated carbon can replace NO2. - As an electron acceptor, it participates in the anaerobic ammonia oxidation process, i.e., the iron ammonia oxidation process (Feammox, as shown in equations (2) to (4)), so that even in the absence of NO2 and low ammonia nitrogen, it can participate in the anaerobic ammonia oxidation process. - Even with suitable influent conditions, the denitrification process can be initiated quickly, and the presence of Fe(III) can inhibit the activity of nitrifying bacteria and reduce NO2. - Oxidized to NO3 - Meanwhile, NO2 produced by the oxidation of iron and ammonium - It participates in the anaerobic ammonium oxidation process (Anammox, as shown in formula (1)) to achieve partial denitrification; in addition, Fe(II) and NO3 in the system -A nitrate-dependent ferrous oxidation process (NDFO, as shown in equation (5)) can occur, driving the Fe(III) / Fe(II) cycle, reducing Fe(III) consumption, and promoting NO3- oxidation. - Further reduction to nitrogen gas achieves nitrogen removal; iron-loaded granular activated carbon can also act as a conductive material to promote electron transfer between microorganisms, and Fe can promote the growth and metabolism of anaerobic ammonia oxidizing bacteria, thereby enhancing the biological denitrification process at room temperature; under low oxygen conditions in the influent, the nitrifying bacteria in the nitrification-anaerobic ammonia oxidizing sludge in the mixed sludge can utilize oxygen to reduce NH4+. + Oxidized to NO2 - (As shown in equation (6)), providing NO2 for the anaerobic ammonia oxidation process. - This process further improves the overall denitrification effect and rate, and the consumption of oxygen in the water also provides a more favorable reaction environment for the anaerobic ammonia oxidation and ferroammonia oxidation processes. Furthermore, the microorganisms in the mixed sludge are better adapted to low-ammonia-nitrogen wastewater environments at room temperature, which helps to achieve a stable denitrification state more quickly.

[0025] 3Fe(OH)3 + 5H + +NH4 + →3Fe 2+ +9H2O+0.5N2 Equation (2)

[0026] 6Fe(OH)3 + 10H + +NH4 + →6Fe 2+ +16H2O+NO2 - Equation (3)

[0027] 8Fe(OH)3 + 14H + +NH4 + →8Fe 2+ +21H2O+NO3 - Equation (4)

[0028] 10Fe 2+ +2NO3 - +12H + →10Fe 3+ +6H2O+N2 Equation (5)

[0029] NH4 + +1.5O2→NO2 - +2H + +H2O formula (6) Attached Figure Description

[0030] Figure 1This is a schematic diagram of the process flow of an iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor in one embodiment of the present invention.

[0031] Attached reference numerals: 1. Inlet tank; 2. Inlet pump; 3. Anaerobic reactor; 31. Reaction zone; 32. Separation zone; 33. Inlet; 34. Outlet; 35. Circulating water inlet; 36. Circulating water outlet; 4. Membrane module; 5. Iron-loaded granular activated carbon; 6. Circulation pump; 7. Outlet pump. Detailed Implementation

[0032] The low-ammonia nitrogen wastewater treatment method provided by this invention includes the following steps: In an anaerobic fluidized bed membrane bioreactor, iron-loaded granular activated carbon is added and mixed sludge is inoculated. Low-ammonia nitrogen wastewater to be treated is introduced for denitrification. During the denitrification process, the low-ammonia nitrogen wastewater forms a feed-liquid circulation through a circulating pump, and the iron-loaded granular activated carbon and mixed sludge in the reactor are in a fluidized state. The wastewater is then separated by a membrane to obtain effluent. The mixed sludge includes at least nitrification-anaerobic ammonium oxidation sludge and iron anaerobic ammonium oxidation sludge. The nitrification-anaerobic ammonium oxidation sludge contains anaerobic ammonium oxidizing bacteria and nitrifying bacteria. The iron anaerobic ammonium oxidation sludge contains microorganisms capable of removing ammonia nitrogen from the low-ammonia nitrogen wastewater through the iron anaerobic ammonium oxidation process. The iron anaerobic ammonium oxidation sludge is obtained through a step-by-step intermittent cultivation method, allowing the microorganisms in the sludge to gradually adapt to the presence of Fe and the absence of NO2. - The environment is designed to smoothly drive the Feammox process.

[0033] In this invention, the inoculum amount of the mixed sludge is preferably 25-35% of the effective volume of the reactor, such as 25%, 28%, 30%, 32%, 35%, or any value between them. The sludge concentration of the mixed sludge is preferably 20-30 mg / L. The volume ratio of the nitrification-anammox sludge to the iron anammox sludge is preferably (1.5-3):1, such as 1.5:1, 1.8:1, 2.0:1, 2.2:1, 2.5:1, 2.8:1, 3:1, or any value between them. Controlling the volume ratio of anammox sludge to iron anammox sludge within the above-mentioned preferred range is more conducive to the coupled synergistic effect of nitrification, Anammox, Feammox, and NDFO within the reactor.

[0034] In this invention, the iron-loaded anammox sludge is obtained by acclimation using the following method: iron-loaded granular activated carbon, conventional anammox sludge, and nitrogen-containing wastewater are mixed and acclimated under an anaerobic environment. The nitrogen-containing wastewater contains NH4+. + The -N concentration is preferably 100–200 mg / L, such as 100 mg / L, 120 mg / L, 150 mg / L, 180 mg / L, 200 mg / L, or any value between them, NH4 + -N and NO2- The preferred NO2-N concentration ratio is 1:(1–1.5), such as 1:1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, or any value between them. During the acclimatization process, NO2 is gradually reduced. - The concentration of -N, up to NH4 + -N and NO2 - The concentration ratio of -N was set to 1:0, and the concentration of NH4 was adjusted. + When the -N concentration is 30–60 mg / L, such as 30 mg / L, 35 mg / L, 40 mg / L, 45 mg / L, 50 mg / L, 55 mg / L, 60 mg / L, or any value between them, the NH4+ in the wastewater... + -N removal rate of over 50% yields iron-based anammox sludge. When this iron-based anammox sludge, acclimated using the above method, is used for treating low-ammonia-nitrogen wastewater, it helps to reduce NO2 under low-ammonia-nitrogen conditions. - Unstable nitrogen sources, coupled with enhanced denitrification advantages. Specifically, it reduces NO2 in a stepwise manner. - The gradient for reducing the concentration of -N can be determined based on the actual situation. In addition, after each reduction in concentration, a period of cultivation is required. The next concentration reduction can be carried out after the removal effect of ammonia nitrogen and total nitrogen in the water has stabilized.

[0035] In the above-mentioned acclimation method for iron-loaded anammox sludge, the preferred volume ratio of the iron-loaded granular activated carbon to nitrogen-containing wastewater is (0.05–0.2) g:2 mL, such as 0.05 g:2 mL, 0.1 g:2 mL, 0.12 g:2 mL, 0.15 g:2 mL, 0.18 g:2 mL, 0.2 g:2 mL, or any value between them. The preferred volume ratio of the anammox sludge to nitrogen-containing wastewater is (0.5–1.5) mL:2 mL, such as 0.5 mL:2 mL, 0.8 mL:2 mL, 1 mL:2 mL, 1.2 mL:2 mL, 1.5 mL:2 mL, or any value between them. The preferred sludge concentration of the anammox sludge is 30–50 mg / L, such as 30 mg / L, 35 mg / L, 40 mg / L, 45 mg / L, 50 mg / L, or any value between them.

[0036] In this invention, the volumetric filling rate of the iron-loaded granular activated carbon in the anaerobic fluidized bed membrane bioreactor is preferably 10-30%, such as 10%, 15%, 20%, 25%, 30%, or any value between them. Within the above preferred range, it is more conducive to sufficient contact between the iron-loaded granular activated carbon in the fluidized state and the microorganisms in the mixed sludge and the wastewater, accelerating mass transfer efficiency and improving the denitrification effect of treating low ammonia nitrogen wastewater at room temperature. In addition, during continuous operation, the iron-loaded granular activated carbon in the fluidized state can flush the membrane surface to effectively control the development of membrane surface fouling. For example, the TMP (Trans-Membrane Pressure) can be controlled at a low fouling level of 1.2-2.9 kPa, and the membrane module does not require additional cleaning, which helps to ensure the stable operation of the wastewater treatment process.

[0037] In this invention, the ammonia nitrogen concentration of the low ammonia nitrogen wastewater is preferably 30–60 mg / L, such as 30 mg / L, 35 mg / L, 40 mg / L, 45 mg / L, 50 mg / L, 55 mg / L, 60 mg / L, or any value between them; the temperature is preferably 20–30℃, such as 20℃, 22℃, 25℃, 28℃, 30℃, or any value between them; the dissolved oxygen concentration is preferably 0.1–0.4 mg / L, such as 0.1 mg / L, 0.15 mg / L, 0.2 mg / L, 0.25 mg / L, 0.3 mg / L, 0.35 mg / L, 0.4 mg / L, or any value between them.

[0038] In this invention, the hydraulic retention time for the denitrification treatment is preferably 2.5–24 h, such as 2.5 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 24 h, or any value between them. The membrane flux is preferably 4–38 L / (m²). 2 ·h), such as 4L / (m 2 ·h), 8L / (m 2 ·h), 10L / (m 2 ·h), 15L / (m 2 ·h), 20L / (m 2 ·h), 25L / (m 2 ·h), 30L / (m 2 ·h), 35L / (m 2 ·h), 38L / (m 2 ·h) or any value between them.

[0039] In this invention, the preferred method for preparing the iron-loaded granular activated carbon includes the following steps: preparing an iron solution using a trivalent iron source and a divalent iron source, then adding granular activated carbon and an alkaline solution to obtain a mixed solution and performing a co-precipitation reaction, followed by separation and washing to obtain the iron-loaded granular activated carbon.

[0040] In the above method for preparing iron-loaded granular activated carbon, the Fe in the iron solution... 3+ with Fe 2+ The preferred molar ratio is (0.5–2):1, such as 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, or any value between them. The preferred ratio of the iron solution to granular activated carbon is (4–6) mL:1g, such as 4 mL:1g, 4.5 mL:1g, 5 mL:1g, 5.5 mL:1g, 6 mL:1g, or any value between them. The amount of alkaline solution used is preferably such that the pH of the mixed solution is 8–10. The conditions for the coprecipitation reaction may include: the preferred reaction temperature is 50–70℃, such as 50℃, 55℃, 60℃, 65℃, 70℃, or any value between them; the preferred reaction time is 0.5–2h, such as 0.5h, 1h, 1.5h, 2h, or any value between them. The granular activated carbon can be selected from coal-based activated carbon and / or coconut shell activated carbon, with a preferred particle size of 8-30 mesh, such as 8 mesh, 10 mesh, 15 mesh, 20 mesh, 25 mesh, 30 mesh, or any value between them. The ferric and ferrous iron sources can be selected from conventional iron salts, such as FeCl3, FeCl2, FeSO4, Fe2(SO4)3, etc. The alkaline solution can be prepared by mixing an alkaline substance with an aqueous solution, and the concentration of the alkaline solution is preferably 4-6 mol / L, such as 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, or any value between them; the alkaline substance is preferably sodium hydroxide and / or potassium hydroxide.

[0041] In a preferred embodiment, the preparation method of the iron-loaded granular activated carbon may specifically include the following steps: washing the granular activated carbon with deionized water and drying it; preparing an iron solution using a trivalent iron source and a divalent iron source; adding the washed and dried granular activated carbon material to the iron solution and stirring thoroughly; slowly adding a certain amount of alkaline solution during the mixing process to adjust the pH of the mixed solution to 8-10; reacting at 50-70°C for 0.5-2 hours; allowing the mixture to stand for 6-24 hours after the reaction is completed; removing the supernatant; rinsing the material with deionized water and drying it to obtain the iron-loaded granular activated carbon.

[0042] In this invention, the low ammonia nitrogen wastewater treatment method can be carried out in an iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor. The iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor preferably includes: an anaerobic reactor 3, iron-loaded granular activated carbon 5 filled in the anaerobic reactor 3, and a membrane module 4 disposed within the anaerobic reactor 3. The anaerobic reactor 3 has a reaction zone 31 and a separation zone 32 that are interconnected. The reaction zone 31 is filled with iron-loaded granular activated carbon 5 and has the membrane module 4 disposed therein. The anaerobic reactor 3 has an inlet 33, an outlet 34, a circulating water inlet 35, and a circulating water outlet 36. The inlet 33 and the circulating water inlet 35 are connected to the reaction zone 34, and the circulating water outlet 36 is connected to the separation zone 32. One end of the membrane module 4 is closed, and the other end is connected to the outlet 34. The circulating water inlet 35 and the circulating water outlet 36 are connected by a pipeline and a circulating pump 6 is provided. Low-ammonia nitrogen wastewater and mixed sludge enter the anaerobic reactor 3 through inlet 33. A portion of the low-ammonia nitrogen wastewater in the anaerobic reactor 3 circulates through the circulating water outlet 36, circulating pump 6, and circulating water inlet 35, causing the iron-loaded granular activated carbon 5 and mixed sludge in the reaction zone 31 of the anaerobic reactor 3 to be in a fluidized state. The denitrified water is separated from the iron-loaded granular activated carbon 5 and mixed sludge by the membrane module 4 and discharged through outlet 34. Furthermore, the iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor may also be equipped with an inlet tank 1, an inlet pump 2, and an outlet pump 7. The inlet tank 1 is connected to the inlet 33 via a pipeline and is equipped with the inlet pump 2. The outlet 34 is connected to the outside via a pipeline equipped with the outlet pump 7, which is used to promptly discharge the effluent from the reactor.

[0043] The present invention will be described in detail below through specific embodiments.

[0044] Preparation Example 1: Preparation of Iron-Loaded Particle Activated Carbon

[0045] Activated carbon particles with a particle size of 20-30 mesh were washed with deionized water and dried. A 500 mL iron solution was prepared using FeCl3 and FeCl2, wherein the total Fe concentration was 0.6 mol / L. 3+ with Fe 2+ The molar ratio is 0.5:1. 100g of the cleaned and dried granular activated carbon material is thoroughly stirred and mixed. During the mixing process, 5mol / L NaOH solution is slowly added to adjust the pH of the mixed solution to 9. The reaction is carried out at 60℃ for 1h. After the reaction is completed, the mixture is allowed to stand for 12h, the supernatant is removed, the material is rinsed with deionized water and dried to obtain iron-loaded granular activated carbon.

[0046] Preparation Example 2: Acclimation of Iron-Based Anaerobic Ammonium Oxidation Sludge

[0047] 20g of iron-loaded granular activated carbon, 150mL of conventional anaerobic ammonia oxidation sludge, and 350mL of nitrogen-containing wastewater were mixed and acclimated under an anaerobic environment at room temperature. The NH4+ in the nitrogen-containing wastewater was then... + -N concentration is 145 mg / L, NH4 + -N and NO2 - The concentration ratio of -N was 1:1.25, and during the acclimatization process, NH4+... + -N and NO2 - The concentration of -N decreases in a stepwise manner, specifically as follows: a. NH4 + -N and NO2 - The concentration ratio of -N was 1:1.25, maintained for 28 days; b.NH4 + -N and NO2 - The concentration ratio of -N was 1:0.5, maintained for 14 days; c.NH4 + -N and NO2 - The concentration ratio of -N was 1:0, maintained for 14 days. On the 8th day of this phase, NH4... + The ammonia nitrogen concentration was reduced to 45 mg / L to adapt to the low ammonia nitrogen environment. When the average ammonia nitrogen removal rate reached about 50%, iron anammox sludge was obtained.

[0048] Example 1

[0049] (1) Iron-loaded particle activated carbon coupled with anaerobic fluidized bed membrane bioreactor, such as Figure 1 As shown, it includes: an inlet tank 1, an inlet pump 2, an anaerobic reactor 3, iron-loaded granular activated carbon 5 filled in the anaerobic reactor 3, a membrane module 4 installed in the anaerobic reactor 3, a circulation pump 6, and an outlet pump 7. The inlet tank 1 is connected to the inlet 33 by a pipeline and is equipped with the inlet pump 2. The anaerobic reactor 3 has an interconnected reaction zone 31 and a separation zone 32. The reaction zone 31 is filled with iron-loaded granular activated carbon 5 and is equipped with the membrane module 4. The anaerobic reactor 3 has an inlet 33, an outlet 34, a circulating water inlet 35, and a circulating water outlet 36. The inlet 33 and the circulating water inlet 35 are connected to the reaction zone 34, and the circulating water outlet 36 is connected to the separation zone 32. One end of the membrane module 4 is closed and the other end is connected to the outlet 34. The outlet 34 is connected to the outside by a pipeline and is equipped with the outlet pump 7. The circulating water inlet 35 and the circulating water outlet 36 are connected by a pipeline and are equipped with the circulation pump 6.

[0050] (2) Low ammonia nitrogen wastewater treatment method: The iron-loaded granular activated carbon obtained in Preparation Example 1 was added to the anaerobic reactor 3 (effective volume of 2.4L) at a volume filling rate of 20%. Mixed sludge with a sludge concentration of 25 mg / L was inoculated into the anaerobic reactor 3 at an inoculation amount of 1 / 3 of the reactor's effective volume. The volume ratio of nitrification-anaerobic ammonia oxidation sludge (containing anaerobic ammonia oxidizing bacteria and nitrifying bacteria) from the PN / A process to the iron-containing anaerobic ammonia oxidation sludge obtained in Preparation Example 2 was 2.5:1. Low ammonia nitrogen wastewater (DO 0.1~0.4 mg / L, temperature 28±1℃) with an ammonia nitrogen concentration of 49.2±0.8 mg / L and a total nitrogen concentration of 60.7±1.6 mg / L was artificially prepared and introduced into the anaerobic reactor 3 at a flow rate of approximately 4.8 L / d. The hydraulic retention time was 12 h, the circulation pump flow rate was 2 L / min, and the membrane flux was 8 L / (m²). 2 The pumping frequency was 8 min / 10 min (8 min pumping every 10 min, followed by a 2 min pause). Under these conditions, the system continued to operate, and the concentrations of ammonia nitrogen and total nitrogen in the influent and effluent were measured daily. Stable nitrogen removal was achieved on the 9th day. During stable operation, the effluent ammonia nitrogen concentration was 21.0 ± 2.2 mg / L, and the total nitrogen concentration was 39.5 ± 3.7 mg / L, with an average ammonia nitrogen removal rate of 56.5 g / (m³). 3 •d), the average total nitrogen removal rate reached 42.3 g / (m³). 3 ·d). Among them, the average ammonia nitrogen removal rate = (influent ammonia nitrogen concentration - effluent ammonia nitrogen concentration) * daily influent flow rate / effective reactor volume, and the average total nitrogen removal rate = (influent ammonia nitrogen concentration - effluent ammonia nitrogen concentration) * daily influent flow rate / effective reactor volume.

[0051] Comparative Example 1

[0052] (1) The iron-loaded particle activated carbon coupled anaerobic fluidized bed membrane bioreactor is the same as in Example 1.

[0053] (2) Low ammonia nitrogen wastewater treatment method: The method is the same as in Example 1(2), except that ordinary activated carbon particles (average particle size of 20-30 mesh) are used instead of the iron-loaded activated carbon particles obtained in Example 1. All other conditions are the same as in Example 1(2). Under these operating conditions, the reactors in Comparative Example 1 and Example 1 were operated in parallel, and the ammonia nitrogen and total nitrogen concentrations of the influent and effluent were tested daily. During stable operation, the ammonia nitrogen concentration of the effluent was 25.2±3.3 mg / L, the total nitrogen concentration was 48.0±3.7 mg / L, and the average ammonia nitrogen removal rate reached 48.0 g / (m³). 3 •d), the average total nitrogen removal rate reached 25.3 g / (m³). 3 ·d).

[0054] As can be seen from the results of the examples and comparative examples, the low ammonia nitrogen wastewater treatment method provided by the present invention has a high denitrification rate and good denitrification effect when applied.

[0055] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for treating low ammonia nitrogen wastewater, characterized in that, The method for treating low-ammonia nitrogen wastewater includes the following steps: In an anaerobic fluidized bed membrane bioreactor, iron-loaded granular activated carbon is added and mixed sludge is inoculated. The low-ammonia nitrogen wastewater to be treated is then introduced for denitrification. During the denitrification process, the low-ammonia nitrogen wastewater circulates through a circulating pump, and the iron-loaded granular activated carbon and mixed sludge in the reactor are in a fluidized state. The wastewater is then separated by a membrane to obtain the effluent. The ammonia nitrogen concentration of the low-ammonia nitrogen wastewater to be treated is 30-60 mg / L, the temperature is 20-30℃, and the dissolved oxygen concentration is 0.1-60 mg / L. 0.4 mg / L; the mixed sludge includes at least nitrification-anammox sludge and iron anammox sludge; the nitrification-anammox sludge contains anammox bacteria and nitrifying bacteria; the iron anammox sludge contains microorganisms capable of removing ammonia nitrogen from low-ammonia nitrogen wastewater through the iron anammox process; the iron anammox sludge is obtained by the following method of acclimation: iron-loaded granular activated carbon, conventional anammox sludge, and nitrogen-containing wastewater are mixed and acclimated in an anaerobic environment, and the initial NH4 of the nitrogen-containing wastewater is... + -N concentration is 100~200 mg / L, NH4 + -N and NO2 - The NO2 concentration ratio was 1:(1~1.5), and NO2 was reduced in a stepwise manner at different stages of the acclimatization process. - The concentration of -N, up to NH4 + -N and NO2 - The concentration ratio of -N was set to 1:0, and the concentration of NH4 was adjusted. + When the -N concentration is 30~60 mg / L, the NH4+ in the wastewater... + The iron anammox sludge is obtained when the -N removal rate is above 50%; the conventional anammox sludge contains anammox bacteria.

2. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The inoculation amount of the mixed sludge is 25-35% of the effective volume of the reactor.

3. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The sludge concentration of the mixed sludge is 20~30 mg / L.

4. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The volume ratio of the nitrification-anammox sludge to the iron anammox sludge is (1.5~3):

1.

5. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, In the iron-loaded anammox sludge acclimation method, the ratio of iron-loaded granular activated carbon, conventional anammox sludge, and nitrogen-containing wastewater is (0.05~0.2)g:(0.5~1.5)mL:2mL.

6. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The volumetric filling rate of the iron-loaded granular activated carbon in the anaerobic fluidized bed membrane bioreactor is 10-30%.

7. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The hydraulic retention time for the denitrification treatment is 2.5 to 24 hours.

8. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The flow rate of the circulating pump is 1.5~3L / min.

9. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The flux of the membrane is 4~38 L / (m²). 2 ·h).

10. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The preparation method of the iron-loaded granular activated carbon includes the following steps: an iron solution is prepared by using a trivalent iron source and a divalent iron source, then granular activated carbon and an alkaline solution are added to obtain a mixed solution, and the mixed solution is subjected to a co-precipitation reaction. After separation and washing, the iron-loaded granular activated carbon is obtained.

11. The method for treating low ammonia nitrogen wastewater according to claim 10, characterized in that, Fe in iron solution 3+ with Fe 2+ The molar ratio is (0.5~2):

1.

12. The method for treating low ammonia nitrogen wastewater according to claim 10, characterized in that, The ratio of the iron solution to the granular activated carbon is (4~6) mL:1 g.

13. The method for treating low ammonia nitrogen wastewater according to claim 10, characterized in that, The amount of alkaline solution used is such that the pH of the mixed solution is 8-10.

14. The method for treating low ammonia nitrogen wastewater according to claim 10, characterized in that, The conditions for the coprecipitation reaction include: a reaction temperature of 50~70℃ and a reaction time of 0.5~2h.

15. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that, The low ammonia nitrogen wastewater treatment method is carried out in an iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor. The iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor includes: an anaerobic reactor, iron-loaded granular activated carbon filled in the anaerobic reactor, and a membrane module disposed in the anaerobic reactor. The anaerobic reactor has an interconnected reaction zone and a separation zone. The reaction zone is filled with iron-loaded granular activated carbon and has a membrane module. The anaerobic reactor has an inlet, an outlet, a circulating water inlet, and a circulating water outlet. The inlet and the circulating water inlet are connected to the reaction zone, and the circulating water outlet is connected to the separation zone. One end of the membrane module is closed and the other end is connected to the outlet. The circulating water inlet and the circulating water outlet are connected by a pipeline and a circulation pump is provided.

16. The application of the low ammonia nitrogen wastewater treatment method according to any one of claims 1 to 15 in the field of wastewater treatment.

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