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

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a low-ammonia-nitrogen wastewater treatment method based on an iron-loaded particle 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 an anaerobic fluidized bed membrane bioreactor, adding iron-loaded granular active carbon, inoculating mixed sludge, introducing to-be-treated low-ammonia-nitrogen wastewater for denitrification treatment, forming feed liquid circulation by the low-ammonia-nitrogen wastewater under the action of a circulating pump in the denitrification process, and discharging the low-ammonia-nitrogen wastewater to the anaerobic fluidized bed membrane bioreactor. The iron-loaded granular active carbon and the mixed sludge in the reactor are in a fluidized state, and then carrying out membrane separation to obtain effluent; the mixed sludge at least comprises nitrosation-anaerobic ammonia oxidation sludge and iron anaerobic ammonia oxidation sludge. Aiming at low-ammonia-nitrogen wastewater treatment at normal temperature, the method provided by the invention enables the low-ammonia-nitrogen wastewater in a normal-temperature environment to realize a good denitrification treatment effect under the synergistic effect of the iron-loaded granular active carbon and the mixed sludge.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a low-ammonia nitrogen wastewater treatment method based on iron-loaded granular activated carbon coupled with an anaerobic fluidized bed membrane bioreactor, a reaction system and an application thereof. Background Art

[0002] Efficient denitrification of sewage is essential for the protection of ecological environment quality. Anaerobic ammonium oxidation (Anammox) is an emerging biological denitrification technology for sewage, which has received great attention in recent years. Anammox refers to the anaerobic ammonium oxidizing bacteria (AnAOB) that uses NO2 - As electron acceptor, NH4 + The autotrophic denitrification process of oxidation to N2 is shown in formula (1). Compared with the traditional full-process nitrification-denitrification sewage biological denitrification process, Anammox can reduce the aeration volume, does not require an external organic carbon source, has a small amount of residual sludge, and 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] 3H2O formula (1)

[0005] At present, Anammox technology is mainly applied in the field of high-ammonia nitrogen wastewater treatment, 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 urban sewage at room temperature is limited. The reason is that, on the one hand, AnAOB grows slowly and has strict requirements on temperature and other conditions. The process startup time is long at room temperature. In the treatment of low-ammonia nitrogen wastewater such as urban sewage, the inlet water temperature is often lower than the optimal growth range of AnAOB of 30-40°C. If the temperature is increased, the operating cost will increase significantly and it is difficult to achieve. On the other hand, NO2 in the wastewater - The deficiency of anaerobic ammonium oxidation often requires the combination of short-cut nitrification and other processes in practical applications. However, under low ammonia nitrogen concentration conditions, the NO2 - Often unstable and easily oxidized to NO3 -, making the Anammox process ineffective. Therefore, in order to realize the application of Anammox in low ammonia nitrogen wastewater treatment, it is necessary to solve the problem of NO2 - Insufficient sources lead to low efficiency of traditional anaerobic ammonium oxidation, in order to improve the denitrification effect and the start-up speed of the treatment process. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of NO2 - The lack of sources leads to the low efficiency and poor denitrification effect of traditional anaerobic ammonia oxidation. A low-ammonia nitrogen wastewater treatment method based on iron-loaded granular activated carbon coupled with an anaerobic fluidized bed membrane bioreactor and a reaction system and application are provided. In the case of low ammonia nitrogen influent and no external NO2 - Under the condition of high efficiency, it can achieve high nitrogen removal of sewage, improve the nitrogen removal rate and start-up speed quickly.

[0007] In a first aspect, the present invention provides a method for treating low-ammonia nitrogen wastewater, which comprises the following steps: in an anaerobic fluidized bed membrane bioreactor, iron-loaded granular activated carbon is added and mixed sludge is inoculated, and the low-ammonia nitrogen wastewater to be treated is introduced for denitrification treatment. During the denitrification process, the low-ammonia nitrogen wastewater forms a feed liquid circulation through the action of a circulating pump, and the iron-loaded granular activated carbon and the mixed sludge in the reactor are in a fluidized state, and then the effluent is obtained after membrane separation; the mixed sludge at least comprises nitrite-anaerobic ammonium oxidation sludge and iron anaerobic ammonium oxidation sludge; the nitrite-anaerobic ammonium oxidation sludge contains anaerobic ammonium oxidizing bacteria and nitrosating bacteria; the iron anaerobic ammonium oxidation sludge contains microorganisms that can remove ammonia nitrogen in the low-ammonia nitrogen wastewater through the iron anaerobic ammonium oxidation process.

[0008] In a preferred embodiment, the inoculation amount of the mixed sludge 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 nitrite-anaerobic ammonium oxidation sludge to the iron anaerobic ammonium oxidation sludge is (1.5-3):1.

[0011] In a preferred embodiment, the method for acclimating the iron anaerobic ammonium oxidation sludge comprises: mixing the iron-loaded granular activated carbon, conventional anaerobic ammonium oxidation sludge and nitrogen-containing wastewater and culturing them under an anaerobic environment, wherein the initial NH4 + -N concentration is 100~200mg / L, NH4 + -N and NO2 --N concentration ratio is 1:(1~1.5), and NO2 is reduced step by step at different stages of the acclimatization and cultivation process. - -N concentration, up to NH4 + -N and NO2 - -N concentration ratio is 1:0 and adjust NH4 + -N concentration is 30~60mg / L, at this time, NH4 + -N removal rate is above 50%, that is, iron anaerobic ammonium oxidation sludge is obtained; the conventional anaerobic ammonium oxidation sludge contains anaerobic ammonium oxidizing bacteria.

[0012] In a preferred embodiment, the usage 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 volume 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 low ammonia nitrogen wastewater has an ammonia nitrogen concentration of 30 to 60 mg / L, a temperature of 20 to 30° C., and a dissolved oxygen concentration of 0.1 to 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 flux of the membrane is 4 to 38 L / (m 2 h).

[0017] In a preferred embodiment, the preparation method of the iron-loaded granular activated carbon comprises the following steps: using a trivalent iron source and a divalent iron source to configure an iron solution, 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 usage ratio of the iron solution to the granular activated carbon is (4-6) mL:1 g.

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

[0021] In a preferred embodiment, the coprecipitation reaction conditions include: reaction temperature of 50-70° C., and 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, and the iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor comprises: an anaerobic reaction tank, iron-loaded granular activated carbon filled in the anaerobic reaction tank, and a membrane assembly arranged in the anaerobic reaction tank, the anaerobic reaction tank is provided with a reaction zone and a separation zone interconnected with each other, the reaction zone is filled with iron-loaded granular activated carbon and is provided with a membrane assembly, the anaerobic reaction tank is provided with a water inlet, a water outlet, a circulating water inlet and a circulating water outlet, the water inlet and the circulating water inlet are connected to the reaction zone, the circulating water outlet is connected to the separation zone, one end of the membrane assembly is closed and the other end is connected to the water outlet, the circulating water inlet and the circulating water outlet are connected by a pipeline and are provided with a circulating pump.

[0023] In a second aspect, the present invention also provides application of the above-mentioned low ammonia nitrogen wastewater treatment method in the field of sewage treatment.

[0024] The present invention constructs a wastewater treatment method based on iron-loaded granular activated carbon coupled with an anaerobic fluidized membrane bioreactor (AFMBR) and a corresponding reaction system for treating low-ammonia nitrogen wastewater at room temperature. The low-ammonia nitrogen wastewater enters the anaerobic fluidized membrane bioreactor and forms a feed liquid circulation through the action of a circulation pump. The key is to introduce iron-loaded granular activated carbon and inoculate a mixed sludge including at least nitrite-anaerobic ammonium oxidation sludge and iron anaerobic ammonium oxidation sludge, so that the low-ammonia nitrogen wastewater can achieve efficient denitrification treatment under the synergistic action of the iron-loaded granular activated carbon and the mixed sludge, with a high denitrification rate. After the denitrification is completed, the effluent is obtained through membrane separation. It is speculated that the reason may be that under the action of the iron anaerobic ammonium oxidation sludge, Fe(III) in the iron-loaded granular activated carbon can replace NO2 - As an electron acceptor, it participates in the anaerobic ammonium oxidation process, that is, the iron ammonia oxidation process (Feammox, as shown in formulas (2) to (4)), so that even in low ammonia nitrogen and NO2 - In the case of influent, the denitrification process can be started quickly, and the presence of Fe(Ⅲ) can inhibit the action of nitrifying bacteria and reduce NO2 - Oxidized to NO3 - ; At the same time, NO2 produced by iron ammonia oxidation - Participate in the anaerobic ammonium oxidation process (Anammox, as shown in formula (1)) to achieve partial denitrification; in addition, Fe(Ⅱ) in the system reacts with NO3 -Nitrate-dependent Fe(Ⅱ) oxidizing (NDFO, as shown in formula (5)) can occur, driving the Fe(Ⅲ) / Fe(Ⅱ) cycle, reducing the consumption of Fe(Ⅲ) and promoting NO3 - Further reduction to nitrogen gas to achieve 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 ammonium-oxidizing bacteria, thereby strengthening the biological denitrification process at room temperature; in the case of low oxygen in the influent, the nitrite-anaerobic ammonium-oxidizing sludge in the mixed sludge can use oxygen to convert NH4 + Oxidized to NO2 - (As shown in formula (6)), providing NO2 for the anaerobic ammonium oxidation process - The source of nitrogen can be further improved, and the overall denitrification effect and rate can be further improved. The consumption of oxygen in the water can also provide a more favorable reaction environment for anaerobic ammonia oxidation and ferric ammonia oxidation processes. In addition, the microorganisms in the mixed sludge are more adaptable to the low ammonia nitrogen wastewater environment at room temperature, which is conducive to achieving a stable denitrification state more quickly.

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

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

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

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

[0029] NH4 + +1.5O2→NO2 - +2H + +H2O formula (6) BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] Figure numerals: 1. water inlet tank; 2. water inlet pump; 3. anaerobic reaction tank; 31. reaction zone; 32. separation zone; 33. water inlet; 34. water outlet; 35. circulating water inlet; 36. circulating water outlet; 4. membrane assembly; 5. iron-loaded granular activated carbon; 6. circulation pump; 7. water outlet pump. DETAILED DESCRIPTION

[0032] The method for treating low-ammonia nitrogen wastewater provided by the present invention comprises the following steps: in an anaerobic fluidized bed membrane bioreactor, iron-loaded granular activated carbon is added and mixed sludge is inoculated, and the low-ammonia nitrogen wastewater to be treated is introduced for denitrification treatment. During the denitrification process, the low-ammonia nitrogen wastewater forms a feed liquid circulation through the action of a circulating pump, and the iron-loaded granular activated carbon and the mixed sludge in the reactor are in a fluidized state, and then the effluent is obtained after membrane separation; the mixed sludge at least includes nitrite-anaerobic ammonium oxidation sludge and iron anaerobic ammonium oxidation sludge; the nitrite-anaerobic ammonium oxidation sludge contains anaerobic ammonium oxidizing bacteria and nitrosating bacteria; the iron anaerobic ammonium oxidation sludge contains microorganisms that can remove ammonia nitrogen in low-ammonia nitrogen wastewater through the iron anaerobic ammonium oxidation process. Wherein, the iron anaerobic ammonium oxidation sludge is obtained by domestication by a step-by-step intermittent culture method, so that the microorganisms in the sludge gradually adapt to the presence of Fe and the absence of NO2 - environment to smoothly drive the Feammox process to occur.

[0033] In the present invention, the inoculation 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 therebetween. The sludge concentration of the mixed sludge is preferably 20-30 mg / L. The volume ratio of the nitrite-anaerobic ammonium oxidation sludge to the iron anaerobic ammonium oxidation 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 therebetween. Controlling the volume ratio of anaerobic ammonium oxidation sludge to iron anaerobic ammonium oxidation sludge within the above-mentioned preferred range is more conducive to the coupled synergistic effect of nitrite, Anammox, Feammox and NDFO in the reactor.

[0034] In the present invention, the iron anaerobic ammonium oxidation sludge is domesticated by the following method: iron-loaded granular activated carbon, conventional anaerobic ammonium oxidation sludge and nitrogen-containing wastewater are mixed and then domesticated and cultured under an anaerobic environment, and the NH4 + -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 therebetween, NH4 + -N and NO2- The concentration ratio of -N is preferably 1:(1-1.5), such as 1:1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or any value therebetween, and the NO2 is reduced stepwise during the acclimation and cultivation process. - -N concentration, up to NH4 + -N and NO2 - -N concentration ratio is 1:0 and adjust NH4 + -N concentration is 30-60mg / L, such as 30mg / L, 35mg / L, 40mg / L, 45mg / L, 50mg / L, 55mg / L, 60mg / L or any value therebetween. At this time, the NH4 + -N removal rate is above 50%, that is, iron anaerobic ammonium oxidation sludge is obtained. When the iron anaerobic ammonium oxidation sludge obtained by the above method is used for low ammonia nitrogen wastewater treatment, it has the effect of improving NO2 - The source is unstable, coupled with enhanced denitrification advantages. Among them, the step-by-step reduction of NO2 - The gradient of the reduction in -N concentration can be determined according to the actual situation. At the same time, each time the concentration is reduced, it is necessary to cultivate for a period of time. The next concentration reduction can be carried out after the removal effect of ammonia nitrogen and total nitrogen in the water is stable.

[0035] In the above-mentioned iron anaerobic ammonium oxidation sludge acclimation method, the volume ratio of the iron-loaded granular activated carbon to the nitrogen-containing wastewater is preferably (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 therebetween. The volume ratio of the anaerobic ammonium oxidation sludge to the nitrogen-containing wastewater is preferably (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 therebetween. The sludge concentration of the anaerobic ammonium oxidation sludge is preferably 30-50 mg / L, such as 30 mg / L, 35 mg / L, 40 mg / L, 45 mg / L, 50 mg / L or any value therebetween.

[0036] In the present invention, the volume filling rate of the iron-loaded granular activated carbon in the anaerobic fluidized bed membrane bioreactor is preferably 10 to 30%, such as 10%, 15%, 20%, 25%, 30% or any value therebetween. Within the above preferred range, it is more conducive to the full contact between the iron-loaded granular activated carbon in the fluidized state and the microorganisms in the mixed sludge and the wastewater, accelerating the 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 pollution, such as TMP (Trans-Membrane Pressure) can be controlled at a low pollution level of 1.2 to 2.9 kPa, and the membrane assembly does not need additional cleaning, which is conducive to ensuring the stable operation of the wastewater treatment process.

[0037] In the present 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 therebetween; the temperature is preferably 20-30°C, such as 20°C, 22°C, 25°C, 28°C, 30°C or any value therebetween; 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 therebetween.

[0038] In the present invention, the hydraulic retention time of the denitrification treatment is preferably 2.5 to 24 hours, such as 2.5 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 24 hours or any value therebetween. The flux of the membrane is preferably 4 to 38 L / (m 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 in between.

[0039] In the present invention, the preparation method of the iron-loaded granular activated carbon preferably includes the following steps: using a trivalent iron source and a divalent iron source to configure an iron solution, 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.

[0040] In the above-mentioned method for preparing iron-loaded granular activated carbon, the iron solution contains Fe 3+ with Fe 2+ The molar ratio of is preferably (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 therebetween. The dosage ratio of the iron solution to the granular activated carbon is preferably (4-6) mL:1 g, such as 4 mL:1 g, 4.5 mL:1 g, 5 mL:1 g, 5.5 mL:1 g, 6 mL:1 g or any value therebetween. The dosage of the alkaline solution is preferably such that the pH value of the mixed solution is 8-10. The conditions of the coprecipitation reaction may include: the reaction temperature is preferably 50-70°C, such as 50°C, 55°C, 60°C, 65°C, 70°C or any value therebetween; the reaction time is preferably 0.5-2 h, such as 0.5 h, 1 h, 1.5 h, 2 h or any value therebetween. The granular activated carbon can be selected from coal-based activated carbon and / or coconut shell activated carbon, and the particle size is preferably 8 to 30 mesh, such as 8 mesh, 10 mesh, 15 mesh, 20 mesh, 25 mesh, 30 mesh or any value therebetween. The ferric iron source and the ferrous iron source can be selected from conventional iron salts, such as FeCl3, FeCl2, FeSO4, Fe2(SO4)3, etc. The alkaline solution can be prepared by configuring an alkaline substance with an aqueous solution, and the concentration of the alkaline solution is preferably 4 to 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 therebetween; the alkaline substance is preferably selected from 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, using a trivalent iron source and a divalent iron source to prepare an iron solution, adding the washed and dried granular activated carbon material to the iron solution and stirring and mixing it thoroughly, slowly adding a certain amount of alkaline solution during the mixing process to adjust the pH value of the mixed solution to 8-10, reacting at 50-70°C for 0.5-2h, standing for 6-24h 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 the present 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, and the iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor preferably includes: an anaerobic reaction tank 3, iron-loaded granular activated carbon 5 filled in the anaerobic reaction tank 3, and a membrane assembly 4 arranged in the anaerobic reaction tank, the anaerobic reaction tank 3 is provided with a reaction zone 31 and a separation zone 32 interconnected with each other, the reaction zone 31 is filled with iron-loaded granular activated carbon 5 and is provided with a membrane assembly 4, the anaerobic reaction tank 3 is provided with a water inlet 33, a water outlet 34, a circulating water inlet 35 and a circulating water outlet 36, the water inlet 33 and the circulating water inlet 35 are connected to the reaction zone 34, the circulating water outlet 36 is connected to the separation zone 32, one end of the membrane assembly 4 is closed and the other end is connected to the water 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 reaction tank 3 from the water inlet 33. Part of the low-ammonia nitrogen wastewater in the anaerobic reaction tank 3 forms a liquid circulation through the circulating water outlet 36, the circulating pump 6, and the circulating water inlet 35, driving the iron-loaded granular activated carbon 5 and the mixed sludge in the reaction zone 31 in the anaerobic reaction tank 3 to be in a fluidized state. The denitrified water is separated from the iron-loaded granular activated carbon 5 and the mixed sludge by the action of the membrane assembly 4 and discharged through the water outlet 34. In addition, the iron-loaded granular activated carbon coupled anaerobic fluidized bed membrane bioreactor can also be provided with an inlet tank 1, an inlet pump 2, and an outlet pump 7. The inlet tank 1 is connected to the water inlet 33 through a pipeline and is provided with an inlet pump 2. The pipeline connecting the water outlet 34 to the outside is provided with an outlet pump 7, which is used to discharge the outlet water in the reactor in time.

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

[0044] Preparation Example 1 Preparation of Iron-Carrying Granular Activated Carbon

[0045] The granular activated carbon with a particle size of 20-30 mesh was washed with deionized water and dried, and 500 mL of iron solution was prepared by using FeCl3 and FeCl2, wherein the total concentration of Fe was 0.6 mol / L and the concentration of Fe 3+ with Fe 2+ The molar ratio is 0.5:1, 100g of the washed and dried granular activated carbon material is fully stirred and mixed, 5mol / L NaOH solution is slowly added during the mixing process to adjust the pH value of the mixed solution to 9, and the reaction is carried out at 60°C for 1h. After the reaction is completed, it 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 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 cultured under normal temperature anaerobic environment. + -N concentration is 145mg / L, NH4 + -N and NO2 - -N concentration ratio is 1:1.25, and NH4 + -N and NO2 - -N concentration is reduced in a step-by-step manner, and the specific process is as follows: a. NH4 + -N and NO2 - -N concentration ratio is 1:1.25, maintained for 28 days; b. NH4 + -N and NO2 - -N concentration ratio was 1:0.5 and maintained for 14 days; c. NH4 + -N and NO2 - The concentration ratio of NH4-N was 1:0 and maintained for 14 days. On the 8th day of this stage, + -N concentration is reduced to 45 mg / L to adapt to the low ammonia nitrogen environment. When the average ammonia nitrogen removal rate reaches about 50%, iron anaerobic ammonia oxidation sludge is obtained.

[0048] Example 1

[0049] (1) Iron-loaded granular activated carbon coupled with anaerobic fluidized bed membrane bioreactor Figure 1 As shown, it includes: an inlet box 1, an inlet pump 2, an anaerobic reaction tank 3, iron-loaded granular activated carbon 5 filled in the anaerobic reaction tank 3, a membrane assembly 4 arranged in the anaerobic reaction tank, a circulation pump 6, and an outlet pump 7. The inlet box 1 is connected to the water inlet 33 through a pipeline and is provided with an inlet pump 2. The anaerobic reaction tank 3 is provided with 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 is provided with a membrane assembly 4. The anaerobic reaction tank 3 is provided with a water inlet 33, a water outlet 34, a circulating water inlet 35 and a circulating water outlet 36. The water 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 assembly 4 is closed and the other end is connected to the water outlet 34. The pipeline connecting the water outlet 34 to the outside is provided with an outlet pump 7. The circulating water inlet 35 and the circulating water outlet 36 are connected through a pipeline and are provided with a 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 reaction tank 3 (effective volume of 2.4 L) at a volume filling rate of 20%, and the mixed sludge with a sludge concentration of 25 mg / L was inoculated into the anaerobic reaction tank 3, and the inoculation amount was 1 / 3 of the effective volume of the reactor. The volume ratio of the nitrite-anaerobic ammonium oxidation sludge (containing anaerobic ammonium oxidizing bacteria and nitrite-oxidizing bacteria) taken from the PN / A process and the iron anaerobic ammonium oxidation sludge obtained in Preparation Example 2 was 2.5:1. Artificially prepared low-ammonia-nitrogen wastewater with an ammonia nitrogen concentration of 49.2±0.8 mg / L and a total nitrogen concentration of 60.7±1.6 mg / L (DO of 0.1-0.4 mg / L and a temperature of 28±1°C) was introduced into the anaerobic reaction tank 3 at a flow rate of about 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 / (m 2 ·h), the suction frequency was 8min / 10min (8min suction every 10min, stop for 2min). Continuous operation under this operating condition, and testing the concentration of ammonia nitrogen and total nitrogen in the inlet and outlet water every day, the time to achieve stable denitrification effect is the 9th day. During the stable operation period, the concentration of ammonia nitrogen in the outlet water is 21.0±2.2mg / L, the concentration of total nitrogen is 39.5±3.7mg / L, and the average ammonia nitrogen removal rate is 56.5g / (m 3 ·d), the average total nitrogen removal rate reached 42.3g / (m 3 ·d). Among them, the average ammonia nitrogen removal rate = (influent ammonia nitrogen concentration - effluent ammonia nitrogen concentration) * daily influent volume / reactor effective volume, the average total nitrogen removal rate = (influent ammonia nitrogen concentration - effluent ammonia nitrogen concentration) * daily influent volume / reactor effective volume.

[0051] Comparative Example 1

[0052] (1) The iron-loaded granular activated carbon coupled to the 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 that in Example 1 (2), except that ordinary activated carbon particles (average particle size of 20-30 mesh) are used instead of the iron-loaded granular activated carbon obtained in Preparation Example 1. The other conditions are the same as those in Example 1 (2). Under this operating condition, the reactors in Comparative Example 1 and Example 1 are operated in parallel, and the ammonia nitrogen and total nitrogen concentrations of the inlet and outlet water are tested every day. During the stable operation period, the ammonia nitrogen concentration of the outlet water is 25.2±3.3 mg / L, the total nitrogen concentration is 48.0±3.7 mg / L, and the average ammonia nitrogen removal rate is 48.0 g / (m 3 ·d), the average total nitrogen removal rate reached 25.3g / (m 3 ·d).

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

[0055] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent 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 comprises the following steps: adding iron-loaded granular activated carbon and inoculating mixed sludge into an anaerobic fluidized bed membrane bioreactor, introducing the low-ammonia nitrogen wastewater to be treated for denitrification treatment, wherein during the denitrification process, the low-ammonia nitrogen wastewater forms a feed liquid circulation through the action of a circulation pump, and the iron-loaded granular activated carbon and the mixed sludge in the reactor are in a fluidized state, and then the effluent is obtained after membrane separation; the mixed sludge at least comprises nitrite-anaerobic ammonium oxidation sludge and iron anaerobic ammonium oxidation sludge; the nitrite-anaerobic ammonium oxidation sludge contains anaerobic ammonium oxidizing bacteria and nitrosating bacteria; the iron anaerobic ammonium oxidation sludge contains microorganisms that can remove ammonia nitrogen in the low-ammonia nitrogen wastewater through the iron anaerobic ammonium oxidation process.

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; Preferably, the sludge concentration of the mixed sludge is 20-30 mg / L; Preferably, the volume ratio of the nitrite-anaerobic ammonium oxidation sludge to the iron anaerobic ammonium oxidation sludge is (1.5-3):

1.

3. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that: The iron anaerobic ammonium oxidation sludge is obtained by the following method: iron-loaded granular activated carbon, conventional anaerobic ammonium oxidation sludge and nitrogen-containing wastewater are mixed and then cultured in an anaerobic environment, and the initial NH4 + -N concentration is 100~200mg / L, NH4 + -N and NO2 - -N concentration ratio is 1:(1~1.5), and NO2 is reduced step by step at different stages of the acclimatization and cultivation process. - -N concentration, up to NH4 + -N and NO2 - -N concentration ratio is 1:0 and adjust NH4 + -N concentration is 30~60mg / L, at this time, NH4 + -N removal rate is above 50%, that is, iron anaerobic ammonium oxidation sludge is obtained; The conventional anaerobic ammonium oxidation sludge contains anaerobic ammonium oxidizing bacteria.

4. The method for treating low ammonia nitrogen wastewater according to claim 3, characterized in that: The dosage 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.

5. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that: The volume filling rate of the iron-loaded granular activated carbon in the anaerobic fluidized bed membrane bioreactor is 10 to 30%; Preferably, the low-ammonia-nitrogen wastewater to be treated has an ammonia-nitrogen concentration of 30 to 60 mg / L, a temperature of 20 to 30° C., and a dissolved oxygen concentration of 0.1 to 0.4 mg / L.

6. The method for treating low ammonia nitrogen wastewater according to claim 1, characterized in that: The hydraulic retention time of the denitrification treatment is 2.5 to 24 hours; preferably, the flow rate of the circulation pump is 1.5 to 3 L / min; preferably, the flux of the membrane is 4 to 38 L / (m 2 h).

7. 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 comprises the following steps: using a trivalent iron source and a divalent iron source to configure an iron solution, adding granular activated carbon and an alkaline solution to obtain a mixed solution, subjecting the mixed solution to a coprecipitation reaction, and obtaining the iron-loaded granular activated carbon after separation and washing.

8. The method for treating low ammonia nitrogen wastewater according to claim 7, characterized in that: The iron solution contains Fe 3+ with Fe 2+ The molar ratio is (0.5-2):1; Preferably, the ratio of the iron solution to the granular activated carbon is (4-6) mL:1 g; Preferably, the amount of the alkaline solution is such that the pH value of the mixed solution is 8 to 10; Preferably, the coprecipitation reaction conditions include: reaction temperature of 50-70° C., and reaction time of 0.5-2 h.

9. 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 comprising: an anaerobic reaction tank, iron-loaded granular activated carbon filled in the anaerobic reaction tank, and a membrane assembly arranged in the anaerobic reaction tank, the anaerobic reaction tank is provided with a reaction zone and a separation zone interconnected with each other, the reaction zone is filled with iron-loaded granular activated carbon and is provided with a membrane assembly, the anaerobic reaction tank is provided with a water inlet, a water outlet, a circulating water inlet and a circulating water outlet, the water inlet and the circulating water inlet are connected to the reaction zone, the circulating water outlet is connected to the separation zone, one end of the membrane assembly is closed and the other end is connected to the water outlet, the circulating water inlet and the circulating water outlet are connected through a pipeline and are provided with a circulating pump.

10. Application of the low ammonia nitrogen wastewater treatment method according to any one of claims 1 to 9 in the field of sewage treatment.

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