An anaerobic ammonia oxidation-based ammonia nitrogen wastewater treatment method and system

Abstract

The application discloses an ammonia-nitrogen wastewater treatment method and system based on anaerobic ammonia oxidation, and the treatment method comprises successively performing a dissimilatory iron reduction treatment, a nitrosation treatment on ammonia-nitrogen wastewater, and performing anaerobic ammonia oxidation treatment on the wastewater after the nitrosation treatment by introducing the wastewater from the top of an anaerobic ammonia oxidation reactor, and performing Fenton treatment, wherein the solid phase obtained after the Fenton treatment is returned to the dissimilatory iron reduction treatment. The system for realizing the treatment method comprises a dissimilatory iron reduction reaction tank, a nitrosation reaction tank, an inverted anaerobic ammonia oxidation reactor, a Fenton reaction tank and a biological aerated filter which are connected in sequence. The ammonia-nitrogen wastewater treatment method based on anaerobic ammonia oxidation has the advantages of simple process, convenient operation, short starting time, low treatment cost, high treatment efficiency, good treatment effect, wide water quality application range, good running stability, full-quantitative disposal and the like, can effectively purify various kinds of refractory high-ammonia-nitrogen wastewater, has high use value and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to a method and system for treating ammonia nitrogen wastewater, specifically a method and system for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation. Background Technology

[0002] High-ammonia nitrogen wastewater, such as late-stage landfill leachate, anaerobic treated livestock and poultry wastewater, and pharmaceutical wastewater, is difficult to treat to meet discharge standards for ammonia nitrogen and total nitrogen through conventional biological methods due to an imbalanced C / N ratio. Therefore, external carbon sources are usually required to adjust water quality and improve biological treatment efficiency, which increases treatment costs. To address these issues, anaerobic ammonia oxidation (ANAO) can effectively improve wastewater effluent quality to meet discharge standards without the need for external carbon sources. Therefore, the use of ANAO to treat high-ammonia nitrogen wastewater has become a research hotspot. However, existing high ammonia nitrogen wastewater treatment methods based on anaerobic ammonia oxidation still have the following defects: (1) Due to the complex composition of high ammonia nitrogen wastewater, large water quality changes, and the very high content of humic acid and SS, it is not conducive to the rapid growth of anaerobic ammonia oxidation bacteria, resulting in slow bacterial proliferation and difficulty in rapid reactor start-up. At the same time, large changes in water quality can also easily cause a decrease in the activity of anaerobic ammonia oxidation sludge, reducing wastewater treatment efficiency. Therefore, existing processes usually use water quality conditioning + air flotation / flocculation sedimentation + material membrane separation to reduce the humic acid and SS content in wastewater. The membrane material intercepts most of the non-degradable COD such as humic acid substances, improving the influent water quality. The further adverse effect is that the membrane material with SS and humic acid attached to its surface needs to be cleaned frequently, the amount of reagent used is large, it is easy to generate additional washing wastewater, and membrane fouling is still easy to occur. (2) During the denitrification process of granular sludge, the accumulation of N2 can easily cause voids inside the granules, leading to the anammox sludge floating due to decreased density. This affects sludge dispersibility and mass transfer efficiency, ultimately resulting in sludge accumulation, loss, deactivation, or even reactor collapse. Therefore, existing solutions for sludge floating mainly include: (a) collecting and crushing granular sludge and recirculating it through mechanical crushing, shearing, or reactor configuration modification to help release air bubbles inside and attached to the outside of the anammox granular sludge; (b) appropriately controlling nitrogen loads (NLRs) to reduce the generation of excessive N2 and EPSs in a short period by controlling the particle size of the anammox granular sludge; and (c) appropriately increasing the influent phosphorus content. To address sludge floating, the above solutions can be implemented by adjusting the calcium concentration or adding granular sludge cores to increase the density of the anaerobic ammonium oxidation granular sludge and alleviate floating. However, these solutions still have the following drawbacks: venting by crushing inevitably damages the granular sludge morphology, affecting reaction efficiency; reducing the influent load can easily sacrifice treatment efficiency, leading to prolonged hydraulic retention time and increased construction and operating costs; reducing floating by increasing sludge weight requires continuous addition of calcium salts and granular sludge mineral cores, otherwise the granular sludge will float again due to particle size growth, or the granular sludge cores will break and become ineffective, resulting in high treatment costs, unstable operation, and substandard effluent.

[0003] Therefore, how to effectively reduce the adverse effects of influent water quality on anammox activated sludge, and how to overcome the floating problem of anammox activated sludge in a low-cost and efficient manner, are the key to the efficient treatment of ammonia nitrogen wastewater using the anammox process, and are also the technical problems that urgently need to be overcome in this field at present. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a method and system for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation, which is simple in process, convenient in operation, short in start-up time, low in treatment cost, high in treatment efficiency, good in treatment effect, wide applicable water quality range, good in operation stability, and can achieve full-scale treatment.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation includes the following steps:

[0007] S1. Treat ammonia nitrogen wastewater with dissimilar iron reduction;

[0008] S2. Nitrification treatment is carried out on the wastewater that has been treated by reduction of dissimilar iron.

[0009] S3. Wastewater treated by nitrification is introduced from the top of the anaerobic ammonia oxidation reactor for anaerobic ammonia oxidation treatment.

[0010] S4. The wastewater treated by anaerobic ammonia oxidation is subjected to Fenton treatment to separate the solid and liquid phases, and the solid phase is returned to step S1.

[0011] In a further improvement to the above-mentioned ammonia nitrogen wastewater treatment method based on anaerobic ammonia oxidation, in step S3, the wastewater treated by the anaerobic ammonia oxidation is discharged from the lower middle part of the anaerobic ammonia oxidation reactor.

[0012] The above-mentioned method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation is further improved by the following step S3: nitrogen micro-nano bubbles are introduced into the anaerobic ammonia oxidation reactor to circulate and aerate the sludge in the reactor; the particle size of the nitrogen micro-nano bubbles is 0.1 μm to 200 μm; during the anaerobic ammonia oxidation process, the rising rate of the nitrogen micro-nano bubbles in the system is controlled to be ≤3 mm / min; and the aeration rate of the nitrogen micro-nano bubbles in the circulating aeration process is controlled to be 0.2 L·m³. -3 ·min -1 ~4L·m -3 ·min -1 The nitrogen micro-nano bubbles are prepared from the nitrogen collected during the anaerobic ammonia oxidation process.

[0013] The above-mentioned method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation is further improved by the following step S3: nitrogen gas is introduced from the bottom of the anaerobic ammonia oxidation reactor to circulate and aerate the sludge in the reactor; the aeration rate of nitrogen gas is controlled at 0.2 L·m³. -3 ·min -1 ~4L·m -3 ·min -1 The nitrogen gas is collected from the anaerobic ammonia oxidation reactor.

[0014] In a further improvement to the above-mentioned ammonia nitrogen wastewater treatment method based on anaerobic ammonia oxidation, in step S3, the concentration of anaerobic ammonia oxidation sludge during the anaerobic ammonia oxidation process is 3 g / L to 5 g / L; the pH value of the system during the anaerobic ammonia oxidation process is controlled at 7 to 9, the dissolved oxygen concentration is ≤0.05 mg / L, and the mass ratio of nitrite nitrogen to ammonia nitrogen is 1.1 to 1.5:1; the retention time of the wastewater during the anaerobic ammonia oxidation process is 4 to 6 days.

[0015] The above-mentioned method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation is further improved in the following steps: In step S1, the concentration of the iron-reduced sludge during the iron-reduction treatment is 1 g / L to 2 g / L; during the iron-reduction treatment, the pH value of the system is controlled to be 7 to 9, and the oxidation-reduction potential is controlled to be -0.7V to -0.2V; the retention time of the wastewater during the iron-reduction treatment is 6 to 8 days; and before and after the iron-reduction treatment, the following treatment is also included: filtering the ammonia nitrogen wastewater using any one of the following methods: air flotation, microfiltration, or sedimentation, to remove suspended solids (SS) from the wastewater.

[0016] In a further improvement to the above-mentioned ammonia nitrogen wastewater treatment method based on anaerobic ammonia oxidation, in step S2, the concentration of nitrifying sludge during the nitrification process is 6 g / L to 8 g / L; during the nitrification process, the pH value of the system is controlled to be 7 to 9, and the dissolved oxygen concentration is 0.1 mg / L to 0.5 mg / L; and the retention time of the wastewater during the nitrification process is 4 to 6 days.

[0017] In a further improvement to the above-mentioned ammonia nitrogen wastewater treatment method based on anaerobic ammonia oxidation, in step S4, the amount of ferrous iron and H2O2 added during the Fenton treatment process is 0.02% to 0.05% of the wastewater mass; the molar ratio of ferrous iron to H2O2 is 0.5 to 0.6; and the retention time of the wastewater during the Fenton treatment process is 1.5 h to 2 h.

[0018] The above-mentioned method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation is further improved by the following post-treatment of the liquid phase: the liquid phase is treated by an aerated biological filter; the dosage of bacteria in the aerated biological filter is 6 g / L to 8 g / L; and the retention time of the wastewater in the aerated biological filter is 4 to 6 days.

[0019] In a further improvement to the above-mentioned ammonia nitrogen wastewater treatment method based on anaerobic ammonia oxidation, in step S1, the ammonia nitrogen wastewater is one of landfill leachate, livestock and poultry wastewater, and pharmaceutical wastewater, or a mixture thereof.

[0020] As a general technical concept, the present invention also provides an ammonia nitrogen wastewater treatment system based on anaerobic ammonia oxidation, comprising a dissimilar iron reduction reaction tank, a nitrification reaction tank, an inverted anaerobic ammonia oxidation reactor, a Fenton reaction tank, and an aerated biological filter connected in sequence.

[0021] The aforementioned ammonia nitrogen wastewater treatment system based on anaerobic ammonia oxidation is further improved by comprising an inverted anaerobic ammonia oxidation reactor including a reaction tower. The top of the reaction tower has an inlet, and the lower middle part of the reaction tower has an outlet. At least one micro / nano bubble aeration port is provided between the inlet and the outlet. The top of the reaction tower also has a nitrogen outlet, and the bottom of the reaction tower has a nitrogen aeration port. The nitrogen outlet and the nitrogen aeration port are connected by a pipe to form an external nitrogen circulation path. The nitrogen aeration port is located below the outlet. A water distribution device is also provided inside the reaction tower, located below the inlet.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) To address the shortcomings of existing wastewater pretreatment schemes, such as complex processes, difficult operation, large reagent consumption, easy generation of new cleaning wastewater, frequent cleaning of membrane materials, and easy membrane fouling, this invention employs a dissimilar iron reduction coupled with nitrification process to enhance the treatment of ammonia nitrogen wastewater. Dissimilar iron reducing bacteria can be used to achieve the biochemical degradation of humic acid substances in the wastewater. This not only effectively removes humic acid substances from the wastewater but also avoids the generation of new wastewater and membrane fouling. More importantly, the wastewater treated by dissimilar iron reduction not only meets the influent water quality requirements for subsequent nitrification treatment but also, as a biochemical pretreatment process, reduces the impact of water quality fluctuations on the treatment process. The subsequent impact of nitrification and anammox sludge promotes nitrification and facilitates rapid start-up of anammox treatment. In particular, the synergistic effect of microbial treatment composed of dissimilar iron-reducing bacteria and nitrifying sludge enhances the treatment of recalcitrant organic matter and some suspended solids (SS) in wastewater. It also reduces iron-based sludge in subsequent processes and converts ammonia nitrogen in wastewater into nitrite nitrogen. Therefore, by coupling dissimilar iron reduction with nitrification, wastewater can meet the influent water quality requirements of anammox treatment with only one nitrification step. This not only mitigates the adverse effects of influent water quality fluctuations on the activity of anammox sludge but also simplifies the process and improves the overall treatment efficiency. In this invention, dissimilar iron reduction coupled with nitrification is used for enhanced pretreatment, promoting the sludge community and functional evolution in the anammox stage, strengthening the community's advantages, achieving rapid start-up proliferation and activity enhancement. Simultaneously, rapid start-up can be achieved under low-concentration sludge conditions, reducing start-up time by one-third, simplifying the process, and making control easier.

[0024] (2) In view of the problems of easy loss of anaerobic ammonia oxidation bacteria and low granulation efficiency in the existing process, the anaerobic ammonia oxidation treatment of the present invention adopts the operation mode of top water distribution and middle and lower water discharge. On the one hand, when the anaerobic ammonia oxidation reactor is started in this mode, the particle size and reactivity of the granular sludge in the reactor can be distributed from top to bottom, forming an inverted fluidized reaction zone. Correspondingly, the reaction zone with higher reactivity in the reactor is mainly distributed in the middle and upper part. On the other hand, when the wastewater flows from the top of the reactor from top to bottom, the pollutant concentration in the reactor is distributed from top to bottom, and the particle size and reactivity of the granular sludge in the reactor are also distributed in a decreasing manner. Therefore, by optimizing the influent and effluent operation mode, the highest concentration of wastewater can be treated by the most active granular sludge in the reactor, which greatly improves the overall treatment efficiency, significantly shortens the residence time, significantly improves the granulation efficiency, and can also significantly accelerate the enrichment and proliferation rate of anaerobic ammonia oxidation bacteria and the growth rate of granular sludge. While promoting the proliferation of bacteria, it can also effectively avoid the loss of bacteria. Compared to conventional influent methods (bottom or mid-section influent or intermittent influent), the top-distribution method in this invention offers the following advantages: top-distribution promotes the removal of air bubbles, preventing bacterial aggregation and inactivation; highly active granular sludge is always in contact with the highest concentration of wastewater, significantly improving overall efficiency; the granular sludge is distributed in an inverted order according to density, preventing bacterial loss; and it meets the mass transfer requirements of granular sludge and pollutants. Furthermore, this invention employs a combined process of dissimilar iron reduction coupled with nitrification and externally circulating anaerobic ammonium oxidation. Each process stage has clearly defined target pollutants, achieving functional sludge zoning. This zoning process is more efficient, reducing the hydraulic retention time to 2-3 days and increasing removal efficiency.

[0025] (3) To address the problems of easily damaged granular sludge morphology, high treatment costs, low treatment efficiency, and insufficient improvement effect in existing sludge flotation improvement schemes, this invention introduces nitrogen micro-nano bubbles into the anaerobic ammonia oxidation reactor to aerate the sludge. During aeration, due to the slow upward flow rate and long suspension time of the nitrogen micro-nano bubbles, they can form a low-density water-containing layer with the floating granular sludge layer, thereby slowing down the rising rate of the granular sludge. Simultaneously, the bubble disturbance significantly promotes the aggregation and release of bubbles inside the granular sludge, not only without damaging the original morphology of the granular sludge but also further slowing down surface aggregation. The N2 micro-nano bubble-promoted pore N2 exhaust process used in this invention effectively improves sludge flotation while maintaining good sludge particle morphology. It not only accelerates reactor start-up and reduces the loss of effective sludge but also accelerates microbial proliferation and increases denitrification load. More importantly, compared with conventional methods, the N2 micro-nano bubble-promoted pore N2 degassing process used in this invention requires no stirring, no chemical addition, and no outer or inner shell for increasing the weight of granular sludge. Therefore, the process is simpler, easier to operate, lower in cost, more efficient, has better degassing, and is more applicable. Ultimately, this results in a higher influent nitrogen load for granular sludge growth in the anammox reactor and a wider range of applicable water qualities. Furthermore, aerating the granular sludge in the anammox reactor using nitrogen micro-nano bubbles not only facilitates the formation of an inverted fluidized bed but also accelerates the mass transfer rate between bacteria and pollutants during anammox treatment, while protecting the morphology of the bacteria particles. Ultimately, this significantly improves the denitrification efficiency and effect of the ammonia oxidation treatment.

[0026] (4) To address the problems of high reagent dosage, large amount of chemical sludge, and high cost in the Fenton treatment process, this invention reuses the sludge generated during the Fenton treatment process as an iron source in the upstream dissimilar iron reduction process. On the one hand, the reuse of sludge solves the problem of sludge disposal and the source of iron in the dissimilar iron reduction process, which not only avoids the generation of new solid waste but also significantly reduces treatment costs. On the other hand, the ferrous iron generated in the dissimilar iron reduction process can not only reduce the alkalinity of carbonate / bicarbonate in the raw water and form siderite-like compound precipitates, which is beneficial for regulating the downstream nitrification water quality, but also serve as an iron source for anaerobic ammonia oxidizing bacteria, promoting bacterial growth. Thus, the intermediate product (sludge) is recycled and utilized, effectively avoiding potential subsequent treatment or secondary pollution caused by the intermediate product. In this invention, by reusing the sludge generated during the Fenton treatment process, not only can the sludge be used for upstream water quality conditioning, saving costs, but it can also significantly improve the stability of the entire process and achieve better overall treatment results.

[0027] Therefore, this invention treats ammonia nitrogen wastewater using a "dissimilar iron reduction coupled with nitrification + externally generated gas-circulating anaerobic ammonium oxidation + advanced iron oxide source circulation" approach. At the front end, dissimilar iron reduction coupled with nitrification regulates water quality and performs pretreatment. The externally generated gas-circulating anaerobic ammonium oxidation is functionally coupled to achieve highly efficient denitrification while protecting sludge morphology and controlling sludge floating, significantly improving reactor activity and sludge growth rate. Furthermore, the pre-processed dissimilar iron reduction coupled with nitrification eliminates the activity inhibition caused by water quality fluctuations in the anaerobic ammonium oxidation process, significantly enhancing the synergistic denitrification effect between nitrification and anaerobic ammonium oxidation sludge particles. This invention employs a combination of external N2 circulating aeration and top water distribution to accelerate sludge granulation technology, effectively improving sludge particle morphology and accelerating sludge enrichment and proliferation. A high-grade iron oxide source is recycled back to the front end for dissimilar iron reduction coupled with nitrification and anaerobic ammonia oxidation. The process generates no terminal concentrate. Simultaneously, the low-COD wastewater remaining after Fenton treatment undergoes simple treatment in a BAF biological filter to further improve denitrification, ensuring that the effluent meets discharge standards. This allows for the comprehensive treatment of high-ammonia nitrogen wastewater, such as late-stage landfill leachate, anaerobic treated livestock and poultry wastewater, and pharmaceutical wastewater. This invention, based on anaerobic ammonia oxidation for ammonia nitrogen wastewater treatment, boasts advantages such as simple process, convenient operation, short start-up time, low treatment cost, high treatment efficiency, good treatment effect, wide applicability to various water qualities, good operational stability, and the ability to achieve comprehensive treatment. It can effectively purify various recalcitrant high-ammonia nitrogen wastewater, demonstrating high practical value and promising application prospects. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the ammonia nitrogen wastewater treatment process based on anaerobic ammonia oxidation in Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the inverted anaerobic ammonia oxidation reactor in Embodiment 1 of the present invention.

[0031] Legend:

[0032] 1. Reaction tower; 2. Inlet; 3. Outlet; 4. Micro-nano bubble aeration port; 5. Nitrogen outlet; 6. Nitrogen aeration port; 7. Water distribution device; 8. Observation window; 9. Sampling port; a. Granular sludge. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0034] The materials and instruments used in the following examples are all commercially available.

[0035] Example 1:

[0036] A method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation specifically employs a combined process of "dissimilatory iron reduction coupled with nitrification + inverted fluidized bed anaerobic ammonia oxidation + advanced oxidation to remove CODH / iron source reuse + BAF effluent protection" to treat aging leachate from a landfill. The process flow diagram is shown below. Figure 1 As shown, it includes the following steps:

[0037] (1) Take the leachate from an old landfill in Changsha. The water quality of the leachate is as follows: COD 1500~2400mg / L, ammonia nitrogen 1500~2150mg / L, nitrite nitrogen <5mg / L, nitrate nitrogen <3mg / L, B / C 0.13~0.17.

[0038] (2) The leachate is introduced into the equalization tank and filtered using any one of the following methods, but not limited to air flotation, microfiltration, and sedimentation, to remove suspended solids (SS) from the wastewater. Specifically, air flotation followed by microfiltration is used for filtration.

[0039] (3) The leachate is subjected to iron reduction treatment. Specifically, the iron-reduced sludge is mixed with the leachate at a concentration of 1.5 g / L to carry out the iron reduction reaction. During the iron reduction treatment, the pH value of the system is controlled at 8, the oxidation-reduction potential at -0.4 V, and the residence time is 7 days. In this step, the metabolic activity of iron-reducing bacteria is used to degrade humic acid substances in the wastewater and to reduce high-valent iron in the wastewater.

[0040] In step (3), the wastewater quality after the reduction treatment with dissimilar iron is as follows: COD 450~600mg / L, ammonia nitrogen 1700-2000mg / L, nitrite nitrogen <2mg / L, nitrate nitrogen <5mg / L, B / C 0.16~0.20.

[0041] (4) The wastewater treated by iron reduction is subjected to nitrification treatment. Specifically, the nitrification sludge is mixed with the wastewater at a concentration of 7 g / L to carry out the nitrification reaction. During the nitrification treatment, the pH value of the system is controlled at 8, the dissolved oxygen concentration is controlled at 0.3 mg / L, and the retention time is 5 days until the NH4+ in the wastewater is reduced. + -N (ammonia nitrogen): NO2 -When the mass ratio of -N (nitrite nitrogen) (based on N) gradually decreases to approximately 1:1.32, the treatment is complete. In this step, the combined action of sub-digestive bacteria and dissimilar iron-reducing bacteria is utilized to enhance the treatment of recalcitrant organic matter and some suspended solids (SS) in the wastewater, as well as to reduce the iron-based sludge from subsequent processes. Simultaneously, ammonia nitrogen in the wastewater is converted into nitrite nitrogen, enabling the wastewater quality to quickly stabilize and meet the influent requirements for anaerobic ammonia oxidation.

[0042] In step (4), the wastewater quality after nitrification treatment is as follows: COD 170~220mg / L, ammonia nitrogen 760~880mg / L, nitrite nitrogen 980~1120mg / L, nitrate nitrogen <5mg / L, B / C 0.15~0.17.

[0043] (5) The wastewater treated by nitrification is introduced from the top of the anaerobic ammonia oxidation reactor (inverted anaerobic ammonia oxidation reactor) for anaerobic ammonia oxidation treatment. Specifically, the wastewater is introduced from the top of the anaerobic ammonia oxidation reactor into the anaerobic ammonia oxidation sludge with a concentration of 4 g / L. During the anaerobic ammonia oxidation treatment, the pH value of the system is controlled at 8, the dissolved oxygen concentration is ≤0.05 mg / L, the mass ratio of nitrite nitrogen to ammonia nitrogen is 1.2:1, the retention time is 5 days, and the treated wastewater is discharged from the outlet located in the lower part of the anaerobic ammonia oxidation reactor. This step also includes collecting nitrogen generated during the anaerobic ammonia oxidation process. A portion of this nitrogen is introduced into the granular sludge within the anaerobic ammonia oxidation reactor through micro-nano bubble aeration ports located in the middle and upper parts of the reactor's outlet. During this process, nitrogen micro-nano bubbles (with a particle size of 0.1 μm to 200 μm) are formed, and the granular sludge is then circulated and aerated. During the anaerobic ammonia oxidation process, the rising rate of the nitrogen micro-nano bubbles in the system is controlled to be ≤3 mm / min. Utilizing nitrogen micro-nano bubbles for aeration slows down the floating of granular sludge, enhances the mass transfer rate between bacteria and pollutants, protects the morphology of bacteria particles, and significantly improves denitrification efficiency and effect. Simultaneously, during the circulating aeration of nitrogen micro-nano bubbles, the aeration rate is controlled to be 1 L·m³. -3 ·min -1 Another portion of the nitrogen gas is introduced into the anaerobic ammonia oxidation reactor through a nitrogen aeration port located at the bottom of the reactor for circulating aeration. During the circulating aeration process, the nitrogen aeration rate is controlled at 2 L·m³. -3 ·min -1 It is used for the contact degradation of pollutants in the middle and lower parts and the bacterial strain, as well as to eliminate the mass transfer blind zone at the bottom and help promote the granulation of the bacterial strain.

[0044] In step (5), the wastewater quality after anaerobic ammonia oxidation treatment is: COD 110~170mg / L, total nitrogen <20mg / L.

[0045] (6) Fenton treatment is performed on the wastewater after anaerobic ammonia oxidation. Specifically, ferrous iron (e.g., ferrous chloride) and hydrogen peroxide are added to the wastewater at a concentration of 0.03% of the wastewater mass, with a molar ratio of ferrous iron to H2O2 of 0.55. The Fenton reaction is carried out for a residence time of 1.5 hours, followed by solid-liquid separation to obtain a solid phase and a liquid phase. This step further reduces the COD in the wastewater through advanced oxidation.

[0046] In step (6), the obtained solid phase is a sludge containing a large amount of ferric iron, which can be returned to step (3) as an iron source; the water quality of the liquid phase is: COD 30-50 mg / L, total nitrogen <20 mg / L.

[0047] (7) The liquid phase was treated using a biological aerated filter (BAF), with a bacterial inoculum dosage of 7 g / L and a retention time of 5 days. In this step, the small amount of NO3 generated during biochemical denitrification was further removed through BAF degradation. - -N (nitrate nitrogen) and a small amount of C source, thereby ensuring that the effluent can meet the discharge standards.

[0048] In step (7), the effluent quality is: COD 10.5 mg / L, ammonia nitrogen 2.8 mg / L, and total nitrogen < 8 mg / L.

[0049] In addition, the results of other indicators before and after leachate treatment are shown in Table 1. As can be seen from Table 1, after treatment by the method of the present invention, the effluent quality also meets the relevant standards, realizing the full-scale treatment of leachate.

[0050] Table 1. Other parameters of the treated effluent (unit: mg / L)

[0051]

[0052]

[0053] In this embodiment, the combined process of "dissimilatory iron reduction coupled with nitrification + inverted fluidized bed anammox + advanced oxidation for CODH removal / iron source reuse + BAF effluent guarantee" is employed. This process features highly efficient biochemical denitrification that accelerates reactor start-up. After 33-45 days of continuous flow operation, the anammox sludge concentration increases to 6-8 g / L, enabling rapid sludge enrichment and proliferation. Furthermore, the denitrification load of the anammox reactor exceeds 0.6 kgN / m³. 3 *d, the reactor start-up time is shortened by about 1 / 3 compared with the existing technology, the residence time of the denitrification process is shortened to 2-3 days, the treatment capacity is greatly improved, the sludge particle morphology is good, the denitrification load efficiency is higher, the effluent is stable and meets the standards, and no terminal concentrate is generated.

[0054] In Embodiment 1 of this invention, the following system can also be used to effectively treat ammonia nitrogen wastewater. The system includes, in sequence, an equalization tank, a dissimilar iron reduction reaction tank, a nitrification reaction tank, an inverted anaerobic ammonia oxidation reactor, a Fenton reaction tank, and an aerated biological filter. The inverted anaerobic ammonia oxidation reactor used is, for example... Figure 2 As shown, the reaction tower includes a reaction tower 1, with an inlet 2 at the top and an outlet 3 at the lower middle part. At least one micro-nano bubble aeration port 4 is provided between the inlet 2 and the outlet 3. The top of the reaction tower 1 is also provided with a nitrogen outlet 5, and the bottom of the reaction tower 1 is also provided with a nitrogen aeration port 6. The nitrogen outlet 5 and the nitrogen aeration port 6 are connected by a pipe to form an external nitrogen circulation path. The nitrogen aeration port 6 is located below the outlet 3. The reaction tower 1 is also provided with a water distribution device 7, which is located below the inlet 2.

[0055] In this embodiment, when treating ammonia nitrogen wastewater using the above-mentioned system, the ammonia nitrogen wastewater is first fed into an equalization tank for filtration to remove suspended solids (SS). Then, the effluent from the equalization tank is fed into a dissimilar iron reduction reaction tank. Under the action of dissimilar iron reducing bacteria, the recalcitrant substances in the wastewater are reduced by dissimilar iron, removing humic acid substances. Subsequently, the effluent from the dissimilar iron reduction reaction tank is fed into a nitrite reaction tank. Under the action of nitrite-oxidizing bacteria, the ammonia nitrogen in the wastewater is converted into nitrite nitrogen, further reducing the COD of the wastewater to meet the influent requirements of the inverted anaerobic ammonia oxidation reactor. Furthermore, the effluent from the nitrite reaction tank is fed into the inverted anaerobic ammonia oxidation reactor. Under the action of anaerobic ammonia oxidizing bacteria, the nitrite nitrogen is converted into nitrate nitrogen and further reduced into nitrogen gas. Finally, the wastewater undergoes deep treatment in a Fenton reactor and an aerated biological filter to further reduce the COD and nitrogen content, ensuring that the effluent can stably meet the discharge standards.

[0056] In this embodiment, when using an inverted anammox reactor to treat wastewater, the wastewater enters the reactor 1 through the inlet 2 located at the top of the reactor 1. The wastewater is then fully contacted with the granular sludge inside the reactor via the water distribution device 7, flowing from top to bottom. After treatment by anammox bacteria, the wastewater is discharged into the Fenton reactor through the outlet 3 located in the middle of the reactor 1. Simultaneously, during the wastewater treatment process in the inverted anammox reactor, nitrogen generated in the reactor is collected through the nitrogen outlet 5. This nitrogen is then aerated through the micro-nano bubble aeration port 4 and the nitrogen aeration port 6, respectively. Aeration slows down the sludge's floating rate and enhances mass transfer between the sludge and pollutants, thereby improving denitrification efficiency and effectiveness. Furthermore, the inverted anammox reactor of this invention employs a top water distribution system combined with upper-level stepped micro-nano aeration, which is more conducive to controlling the sludge's floating rate and enhancing the removal effect. In this embodiment, the reaction tower 1 is also provided with several observation windows 8, which facilitates the operator to observe the changes in the material inside the reaction tower 1 in a timely manner. A sampling port 9 is also provided at the bottom of the reaction tower 1 in this embodiment.

[0057] Example 2:

[0058] A method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation is basically the same as that in Example 1, except that the ammonia nitrogen wastewater in Example 2 is livestock and poultry wastewater that has undergone anaerobic treatment.

[0059] In Example 2, the water quality indicators for each process stage are as follows:

[0060] Influent water quality: COD 650~950mg / L, ammonia nitrogen 1800~2200mg / L, nitrite nitrogen 15~20mg / L, nitrate nitrogen 20~55mg / L, B / C 0.22~0.30.

[0061] After treatment with dissimilar iron reduction, the wastewater (nitrite influent) has the following water quality: COD 250-300 mg / L, ammonia nitrogen 1700-2100 mg / L, nitrite nitrogen 16-22 mg / L, nitrate nitrogen 15-20 mg / L, and B / C 0.16-0.20.

[0062] Nitrification effluent (anaerobic ammonia oxidation influent) water quality: COD 170~210mg / L, ammonia nitrogen 700~860mg / L, nitrite nitrogen 880~1100mg / L, nitrate nitrogen 25~30mg / L, B / C 0.15~0.17.

[0063] The effluent quality of anaerobic ammonia oxidation (Fenton influent) is as follows: COD 100-160 mg / L, total nitrogen 35-50 mg / L.

[0064] Fenton effluent water quality: COD 25~50mg / L, total nitrogen <30mg / L.

[0065] With the addition of a small amount of carbon source, the effluent quality of BAF is: COD 20-40 mg / L, total nitrogen <8 mg / L.

[0066] Table 2. Other parameters of the treated BAF effluent (unit: mg / L)

[0067] Discharge limit value After treatment Discharge limit value After treatment COD 400 30 BOD 150 12 SS 200 ＜10 Odor concentration (dimensionless) 70 ＜10 Ammonia nitrogen 80 2～4 Roundworm eggs (pieces / L) 2 Not detected Total P 8 0.4 Fecal coliform count 10000 200～600

[0068] As shown in Table 2, after treatment using the above methods, the pollutant indicators are all significantly lower than those meeting the "Emission Standard for Pollutants from Livestock and Poultry Breeding Industry" GB18596-2001.

[0069] The results above show that, compared with conventional ammonia nitrogen wastewater treatment methods, this invention has the following advantages: (1) The heterogeneous iron reduction coupled with nitrification + external gas generation and circulation anaerobic ammonia oxidation process is adopted. The target pollutants of each process section are clearly defined, and the sludge functional zoning is realized. The hydraulic retention time can be shortened to 2-3 days, and the removal efficiency is higher. (2) The top water distribution and inlet mode forms an inverted fluidized bed. The sludge in the reactor is automatically arranged from top to bottom according to the particle size from large to small. The high denitrification load of the top material promotes the growth of sludge particles. (3) The N2 micro-nano bubble promotes the pore N2 exhaust process and maintains a good sludge particle morphology. It accelerates reactor start-up, reduces effective sludge loss, accelerates bacterial proliferation, and increases denitrification load. (3) The heterogeneous iron reduction coupled with nitrification enhances the pretreatment, promotes the sludge community and functional evolution of the anaerobic ammonia oxidation section, strengthens the community advantage, realizes rapid start-up and proliferation, and improves activity. The start-up time under low concentration sludge conditions is shortened by 1 / 3, the process is simplified, and the control is convenient. (4) Reuse of advanced oxidation sludge at the back end achieves water quality conditioning at the front end, saving costs, stabilizing the process, and improving treatment efficiency. (5) Effective venting can be achieved without relying on the shell or core to increase the weight of granular sludge, resulting in higher nitrogen load in the influent for granular sludge growth and a wider range of water quality applications. Therefore, this invention treats ammonia nitrogen wastewater using a "dissimilar iron reduction coupled with nitrification + external gas-generating circulating anaerobic ammonia oxidation + advanced iron oxide source circulation" method. At the front end, dissimilar iron reduction coupled with nitrification is used to regulate water quality and perform pretreatment. Through functional coupling of external gas-generating circulating anaerobic ammonia oxidation, efficient denitrification is achieved while protecting the sludge morphology and controlling sludge floating, greatly improving reactor activity and sludge growth rate. With the help of the pre-process dissimilar iron reduction coupled with nitrification, the activity inhibition of the anaerobic ammonia oxidation process due to water quality fluctuations is relieved, significantly enhancing the synergistic denitrification effect between nitrification and anaerobic ammonia oxidation sludge particles. The combination of external N2 circulating aeration and top water distribution accelerates sludge granulation technology, effectively improving sludge particle morphology and accelerating sludge enrichment. This process integrates aeration and recycling of high-grade iron oxide source to the front end for dissimilar iron reduction coupled with nitrification and anaerobic ammonia oxidation. No terminal concentrate is generated. Simultaneously, the low-COD wastewater remaining after Fenton treatment undergoes simple treatment in a BAF biological filter to further improve denitrification, ensuring the effluent meets discharge standards. This enables the comprehensive treatment of high-ammonia nitrogen wastewater, such as late-stage landfill leachate, anaerobic livestock and poultry wastewater, and pharmaceutical wastewater. It boasts advantages such as simple process, convenient operation, short start-up time, low treatment cost, high treatment efficiency, good treatment effect, wide applicability to various water qualities, good operational stability, and the ability to achieve comprehensive treatment. It can effectively purify various recalcitrant high-ammonia nitrogen wastewater, demonstrating high value and promising application prospects.

[0070] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation, characterized in that, Includes the following steps: S1. Treat ammonia nitrogen wastewater with dissimilar iron reduction; S2. Nitrification treatment is carried out on the wastewater that has been treated by reduction of dissimilar iron. S3. Wastewater treated by nitrification is introduced from the top of the anaerobic ammonia oxidation reactor for anaerobic ammonia oxidation treatment, and the wastewater after anaerobic ammonia oxidation treatment is discharged from the middle and lower part of the anaerobic ammonia oxidation reactor; the anaerobic ammonia oxidation treatment process also includes the following treatment: nitrogen micro-nano bubbles are introduced into the anaerobic ammonia oxidation reactor to circulate and aerate the sludge in the anaerobic ammonia oxidation reactor; the anaerobic ammonia oxidation treatment process also includes the following treatment: nitrogen gas is introduced from the bottom of the anaerobic ammonia oxidation reactor to circulate and aerate the sludge in the anaerobic ammonia oxidation reactor. S4. The wastewater treated by anaerobic ammonia oxidation is subjected to Fenton treatment to separate the solid and liquid phases, and the solid phase is returned to step S1.

2. The method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation according to claim 1, characterized in that, In step S3, the particle size of the nitrogen micro-nano bubbles is 0.1 μm to 200 μm; during the anaerobic ammonia oxidation treatment, the rising rate of the nitrogen micro-nano bubbles in the system is controlled to be ≤3 mm / min; in the circulating aeration treatment, the aeration rate of the nitrogen micro-nano bubbles is controlled to be 0.2 L·m -3 ·min -1 ~4 L·m -3 ·min -1 The nitrogen micro-nano bubbles are prepared from the nitrogen collected during the anaerobic ammonia oxidation process.

3. The method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation according to claim 2, characterized in that, In step S3, the nitrogen aeration rate is controlled at 0.2 L·m³. -3 ·min -1 ~4 L·m -3 ·min -1 The nitrogen gas is collected from the anaerobic ammonia oxidation reactor.

4. The method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation according to claim 3, characterized in that, In step S3, the concentration of anaerobic ammonia oxidation sludge during the anaerobic ammonia oxidation treatment is 3 g / L to 5 g / L; the pH value of the system during the anaerobic ammonia oxidation treatment is controlled at 7 to 9, the dissolved oxygen concentration is ≤0.05 mg / L, and the mass ratio of nitrite nitrogen to ammonia nitrogen is 1.1 to 1.5:1; the retention time of wastewater during the anaerobic ammonia oxidation treatment is 4 to 6 days.

5. The method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation according to any one of claims 1 to 4, characterized in that, In step S1, the concentration of the iron-reduced sludge during the iron reduction treatment is 1 g / L to 2 g / L; the pH value of the system is controlled to be 7 to 9 and the oxidation-reduction potential is -0.7 V to -0.2 V during the iron reduction treatment; the retention time of the wastewater during the iron reduction treatment is 6 to 8 days; the iron reduction treatment also includes the following treatments before and after the iron reduction treatment: filtering the ammonia nitrogen wastewater using any one of the following methods: air flotation, microfiltration, or sedimentation, to remove suspended solids (SS) from the wastewater; In step S2, the concentration of nitrifying sludge during the nitrification process is 6 g / L to 8 g / L; the pH value of the system is controlled to be 7 to 9, and the dissolved oxygen concentration is controlled to be 0.1 mg / L to 0.5 mg / L; the retention time of wastewater during the nitrification process is 4 to 6 days. In step S4, the amount of ferrous iron and H2O2 added during the Fenton treatment is 0.02% to 0.05% of the wastewater mass; the molar ratio of ferrous iron to H2O2 is 0.5 to 0.6; and the retention time of the wastewater during the Fenton treatment is 1.5 h to 2 h.

6. The method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation according to claim 5, characterized in that, In step S4, the subsequent treatment of the liquid phase is as follows: the liquid phase is treated using an aerated biological filter; the dosage of bacteria in the aerated biological filter is 6 g / L to 8 g / L; and the retention time of the wastewater in the aerated biological filter is 4 to 6 days.

7. The method for treating ammonia nitrogen wastewater based on anaerobic ammonia oxidation according to any one of claims 1 to 4, characterized in that, In step S1, the ammonia nitrogen wastewater is one of landfill leachate, livestock and poultry wastewater, and pharmaceutical wastewater, or a mixture thereof.

8. An ammonia nitrogen wastewater treatment system based on anaerobic ammonia oxidation, characterized in that, The system comprises, in sequence, a dissimilar iron reduction reaction tank, a nitrification reaction tank, an inverted anaerobic ammonia oxidation reactor, a Fenton reaction tank, and an aerated biological filter. The inverted anaerobic ammonia oxidation reactor includes a reaction tower with an inlet at the top and an outlet at the lower middle. At least one micro-nano bubble aeration port is located between the inlet and the outlet. The top of the reaction tower also has a nitrogen outlet, and the bottom of the reaction tower has a nitrogen aeration port. The nitrogen outlet and the nitrogen aeration port are connected by a pipe to form an external nitrogen circulation path. The nitrogen aeration port is located below the outlet. The reaction tower also includes a water distribution device located below the inlet.

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