Nitrogen-containing wastewater biological treatment method based on direct ammoxidation

Abstract

The invention discloses a nitrogenous wastewater treatment method based on direct ammoxidation. According to the method, ammonia nitrogen in nitrogenous wastewater is directly converted into nitrogen in an up-flow biological membrane bed reactor by utilizing direct ammoxidation microorganisms. According to the method, by controlling reaction conditions, growth of direct ammoxidation microorganisms is promoted, growth of infectious microbes is inhibited, and ammonia nitrogen is oxidized into nitrogen for direct denitrification.

Description

Technical Field

[0001] This invention belongs to the field of nitrogen-containing wastewater treatment and relates to a biological treatment method for nitrogen-containing wastewater based on direct ammonia oxidation. Background Technology

[0002] Microbial-driven conversion of ammonia nitrogen into nitrogen gas is a crucial pathway for wastewater denitrification. To date, there are two main biological denitrification pathways that convert ammonia into nitrogen gas. One pathway is the earliest and most widely used nitrification / denitrification biological process, which requires the cooperation of multiple bacterial strains. In this process, ammonia is oxidized to nitrate, and then the nitrate is reduced back to nitrogen gas. The other is the anaerobic ammonia oxidation pathway, which utilizes nitrite as an electron acceptor to anaerobicly convert ammonia into nitrogen gas.

[0003] Patent CN107585862A utilizes nitrification-denitrification for nitrogen removal. Ammonia must first be converted to nitrate / nitrite through heterotrophic nitrification, and then reduced to nitrogen gas through denitrification. This process requires the cooperation of multiple functional bacterial communities to complete the biological nitrogen removal process in wastewater. It involves a long reaction route and requires aeration or the addition of external carbon sources, making it uneconomical, energy-efficient, and a one-step solution for ammonia nitrogen removal.

[0004] Patent CN111547850B utilizes a short-cut nitrification-denitrification reactor connected in series with a short-cut nitrification-anaerobic ammonium oxidation reactor to control the NH4 in the effluent from the pre-short-cut nitrification-denitrification reactor. + -N:NO2 - The optimal ratio of -N is crucial for the removal of ammonia nitrogen from wastewater. This requires incorporating short-cut nitrification or similar processes upstream of the anammox process before combining it with anammox. This process involves a long flow path and requires sufficient NH4+. + -N:NO2 - -N is difficult to control. In addition, an excessively high carbon-to-nitrogen ratio entering the anaerobic ammonium oxidation system can also lead to the overgrowth of denitrifying bacteria, thereby inhibiting the anaerobic ammonium oxidation process.

[0005] Patent CN106268289 B utilizes NO-containing gas to contact anaerobic ammonia-oxidizing bacteria, which simultaneously remove NO and ammonia nitrogen. However, this method requires another substrate, NO, for ammonia nitrogen removal. The source of NO-containing gas is limited, or additional NO preparation is necessary, thus restricting the application scenarios of the process and increasing costs.

[0006] Patent CN114149086 B employs electrochemically assisted anaerobic ammonium oxidation for biological denitrification, eliminating the need for additional nitrite to complete the anaerobic ammonium oxidation reaction and directly removing NH4+. + It is oxidized to N2. However, as the reactor size increases, the maximum power density based on the total system volume decreases rapidly, the performance of electrochemically assisted denitrification will rapidly decline, the denitrification efficiency is difficult to maintain, and industrial scale-up is difficult.

[0007] Direct ammonia oxidation microorganisms mainly belong to the genus *Alcaligenes*, which have been discovered in soil, river sediments, and activated sludge from wastewater treatment plants in recent years. Direct ammonia oxidation (Dirammox), dominated by direct ammonia oxidation microorganisms, is a novel biological denitrification pathway. Under aerobic conditions, these microorganisms directly oxidize ammonia nitrogen to nitrogen gas via hydroxylamine.

[0008] NH3+0.75O2→0.5N2+1.5H2OΔG=-328.8kJ mol -1

[0009] The direct ammonia oxidation process requires only 0.75 mol of oxygen to oxidize 1 mol of ammonia, significantly reducing the aeration volume for biological denitrification and thus substantially lowering aeration requirements. The direct ammonia oxidation process utilizes ammonia as an electron donor, eliminating the need for additional carbon sources to obtain electrons for nitrogen conversion, thereby reducing energy consumption. Therefore, direct ammonia oxidation microorganisms show promising potential in the field of biological denitrification. However, the growth conditions of direct ammonia oxidation microorganisms are still unclear, and further research is needed to utilize them for wastewater denitrification. Summary of the Invention

[0010] The purpose of this invention is to provide a method for treating nitrogen-containing wastewater based on direct ammonia oxidation. This method uses an upflow biofilm reactor and, by controlling the reaction conditions, promotes the growth of direct ammonia-oxidizing microorganisms while inhibiting the growth of other bacteria, oxidizing ammonia nitrogen into nitrogen gas for direct denitrification, thus realizing a novel industrial method for treating nitrogen-containing wastewater.

[0011] To achieve one aspect of the above-mentioned objectives, the present invention adopts the following technical solution:

[0012] A method for treating nitrogen-containing wastewater based on direct ammonia oxidation is proposed. This method utilizes direct ammonia-oxidizing microorganisms in an upflow biofilm reactor to directly convert ammonia nitrogen in the wastewater into nitrogen gas.

[0013] The nitrogen-containing wastewater has an ammonia nitrogen concentration of 50–1200 mg / L, a COD concentration of 50–1600 mg / L, and a C / N ratio of (0.5–10.0):1; preferably, the ammonia nitrogen concentration is 80–1000 mg / L, the COD concentration is 100–1600 mg / L, and the C / N ratio is (0.5–6.0):1; more preferably, the ammonia nitrogen concentration is 200–800 mg / L, the COD concentration is 150–600 mg / L, and the C / N ratio is (0.75–2.5):1.

[0014] The internal temperature of the upflow biofilm bed reactor is 20℃~37℃;

[0015] The dissolved oxygen level inside the upflow biofilm bed reactor is 0.5–1.5 mg / L, preferably 0.6–1.2 mg / L, and more preferably 0.8–1.0 mg / L;

[0016] The pH inside the upflow biofilm bed reactor is 7.5–10.0.

[0017] Unlike biotechnologies such as biological pure-strain fermentation, which require the use of pure strains, actual biological wastewater treatment typically utilizes a mixed microbial community within the wastewater as the primary agent. This community absorbs and transforms various organic pollutants in the wastewater, removing them through diffusion, adsorption, coagulation, oxidative decomposition, and sedimentation. Therefore, the microorganisms involved in this method can be a mixed microbial community composed of multiple microorganisms, with direct ammonia-oxidizing microorganisms being the dominant microorganisms.

[0018] It should be understood that, in this application, the direct ammonia-oxidizing microorganism is a microorganism carrying the Dirammox functional strain gene cluster dnf (Dirammox Is Widely Distributed and Dependently Evolved in Alcaligenes and Is Important to Nitrogen Cycle. ORIGINAL RESEARCH, Ting-Ting Hou et al., 2022, doi:10.3389 / fmicb.2022.864053) and capable of direct ammonia oxidation. It can be a known or unknown microorganism, including natural and / or genetically modified microorganisms. Examples include, but are not limited to, *Alcaligenes sammonioxydans HO-1* (A novel oxidase from *Alcaligenes sp. HO-1* oxidizes hydroxylamine to N2, DOI:10.1101 / 2020.08.20.256677) and *Alcaligenes faecalisStrain JQ135* (The MocR family transcriptional regulator DnfR has multiple binding sites and regulates Dirammox gene transcription in *Alcaligenes faecalis JQ135*, DOI:10.1111 / 1462-2920.16318). These direct ammonia-oxidizing microorganisms can be obtained directly from environments such as soil, river sediments, or activated sludge from wastewater treatment plants.

[0019] In some embodiments, the packing material in the upflow biofilm reactor is Fe-Mn oxide packing material. The Fe-Mn oxide packing material is commercially available or can be synthesized using any known method, such as calcination.

[0020] In some embodiments, the packing material is filled to 30%-60% of the effective volume of the reactor, preferably 30%-50%, and more preferably 40%-50%.

[0021] In some embodiments, the ammonia nitrogen sludge load control used in this invention is 0.01–0.15 kg NH4. + -N / kgMLSS.d, preferably 0.01~0.08kgNH4 + -N / kgMLSS.d.

[0022] In some implementations, the average activated sludge concentration is controlled at 6000–12000 mg / L.

[0023] In some embodiments, the upflow biofilm bed reactor includes a water distribution device, a micro-aeration blower, a biofilm packing bed, a sludge baffle, a dissolved oxygen probe, a temperature sensor, and a pH meter, and the upflow biofilm bed reactor is also provided with an outlet at the top.

[0024] The water distribution device is located at the bottom of the upflow biofilm bed reactor. The nitrogen-containing wastewater enters the upflow biofilm bed reactor through the water distribution device. The water distribution device is a rotary water distribution pipe or a tangential water distribution disc.

[0025] The micro-aeration blower is installed at the bottom of the upflow biofilm bed reactor and below the water distribution device. The micro-aeration blower is a microporous aeration disc or a microporous aeration pipe.

[0026] The biofilm packing bed is located in the middle of the upflow biofilm bed reactor;

[0027] The sludge baffle is installed at the top of the upflow biofilm bed reactor, above the biofilm packing bed. The sludge baffle is one, two, or more layers of triangular plates, inclined tubes, or inclined plates.

[0028] The dissolved oxygen probe is positioned between the biofilm packing bed and the sludge baffle, and is close to the biofilm packing bed;

[0029] One or more temperature sensors are provided at the upper, middle and / or lower parts of the upflow biofilm bed reactor;

[0030] One or more pH meters are installed in the upper, middle and / or lower part of the upflow biofilm reactor.

[0031] In some embodiments, the upflow biofilm reactor further includes an overflow baffle disposed between the outlet and the sludge baffle.

[0032] In some embodiments, the biofilm packing bed includes a support frame and a fixing frame, the fixing frame fixing the support frame inside the reactor, and the support frame having a space for accommodating the packing material.

[0033] The support frame is a spherical perforated support frame or a cylindrical perforated support frame;

[0034] The fixing frame is a polygonal fixing frame or a columnar fixing frame.

[0035] In some embodiments, the direct ammonia-oxidizing microorganisms are enriched by attaching to a biofilm in the upflow biofilm reactor through the following steps:

[0036] (1) Microbial proliferation: Direct ammonia oxidizing microorganisms and proliferation liquid culture medium are aerated and proliferated in the proliferation liquid tank for 10 to 15 days, pH 7.0 to 9.0, dissolved oxygen 0.5 to 1.0 mg / L, and temperature 30℃ to 35℃. After the proliferation is completed, the mixture is allowed to stand for separation.

[0037] (2) Microbial biofilm enrichment: The packing material is placed in the biofilm packing bed, and then the activated sludge of direct ammonia oxidation microorganisms that has been settled at the bottom of the proliferating bacterial solution tank is added to the upflow biofilm bed reactor. Nitrogenous wastewater is introduced from the bottom of the upflow biofilm bed reactor, and the amount of nitrogenous wastewater is controlled at 30% to 40% of the effective volume of the upflow biofilm bed reactor, for example, 30% or 35%. The water inflow is stopped, and nutrient salts and trace element concentrates are added. The reaction is carried out with micro-aeration for 24 to 72 hours. The water inflow is continued until the wastewater volume reaches the target level. When the volume of the upflow biofilm reactor reaches 60% to 70% (e.g., 60% or 65%) of its effective volume, stop the influent, replenish the nutrient salts and the trace element concentrate, control the dissolved oxygen in the wastewater within the range of 0.5 to 1.2 mg / L, and perform micro-aeration reaction for 24 to 72 hours; then continue the influent until the wastewater volume reaches 85% to 95% (e.g., 85% or 90%) of the effective volume of the upflow biofilm reactor, stop the influent, replenish the nutrient salts and the trace element concentrate, and perform micro-aeration reaction for 24 to 72 hours.

[0038] In some embodiments, the microbial biofilm enrichment in step (2) is achieved by adding 4 to 10 g MLSS / L of the direct ammonia oxidation microbial activated sludge.

[0039] In some embodiments, the nutrient salt comprises: 0.5 g / L KH₂PO₄; 1.25 g / L NaH₂PO₄·12H₂O; 0.2 g / L MgSO₄·7H₂O; 6.00 g / L NaCl;

[0040] The components of the trace element concentrate include: 0.39 g / L ZnSO4·7H2O; 5.7 g / L LEDTA·2Na; 0.7 g / L CaCl2·2H2O; 1.0 g / L MnCl2·4H2O; 0.50 g / L FeSO4·7H2O; 0.22 g / L NaMoO4·2H2O; and 0.16 g / L CoCl2·6H2O;

[0041] Add 2.0 mL of the trace element concentrate to each liter of the nutrient salts.

[0042] Another aspect of the present invention provides a nitrogen-containing wastewater treatment system, the system comprising a raw water tank, an inlet pump, an upflow biofilm bed reactor, an oxygen supply device, an outlet tank, and a pH adjustment device, wherein the upflow biofilm bed reactor is as described above;

[0043] The raw water tank is connected to the bottom of the upflow biofilm reactor, and the inlet pump is installed on the connecting pipe between the raw water tank and the upflow biofilm reactor to supply nitrogen-containing wastewater to be treated into the upflow biofilm reactor.

[0044] The oxygen supply device provides oxygen to the upflow biofilm reactor; the oxygen supply device includes an aeration fan and a controller, the aeration fan is connected to the micro aeration fan of the upflow biofilm reactor, the controller is communicatively connected to the dissolved oxygen probe of the upflow biofilm reactor and the aeration fan, and the controller adjusts the amount of oxygen delivered by the aeration fan to the micro aeration fan according to the dissolved oxygen level detected by the dissolved oxygen probe;

[0045] The pH adjustment device is installed on the connecting pipe between the raw water tank and the upflow biofilm reactor to adjust the acidity and alkalinity of the nitrogen-containing wastewater to be treated.

[0046] The outlet at the top of the upflow biofilm bed reactor is connected to the effluent tank to collect the treated nitrogen-containing wastewater.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] This invention utilizes direct ammonia oxidizing microorganisms in an upflow biofilm reactor to directly convert ammonia nitrogen in nitrogen-containing wastewater into nitrogen gas under low dissolved oxygen conditions. Direct ammonia oxidizing microorganisms are inherently difficult to accumulate, and their growth requires a certain concentration of oxygen. This means that the denitrification system using direct ammonia oxidizing microorganisms is typically a semi-open system, prone to the presence of other contaminating microorganisms. Consequently, in industrial applications of direct ammonia oxidizing microorganisms for nitrogen-containing wastewater treatment, there are problems with the difficulty in accumulating these microorganisms and the easy proliferation of other microorganisms. This method, by controlling the treatment conditions of nitrogen-containing wastewater, promotes the growth of direct ammonia oxidizing microorganisms as the dominant microorganisms and inhibits the growth of other microorganisms, achieving a better ammonia nitrogen removal effect. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0050] In the diagram: 1-raw water tank; 2-inlet pump; 3-upflow biofilm bed reactor; 4-oxygen supply device; 5-outlet tank; 6-pH adjustment device; 31-water distribution device; 32-micro aeration blower; 33-biofilm packing bed; 34-sludge baffle; 35-dissolved oxygen probe; 36-temperature sensor; 37-pH meter; 38-overflow baffle; 41-aeration blower; 42-controller. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0052] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values, such as values ​​±10% of the endpoint values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Without conflict, the embodiments and features described in this application can be combined with each other.

[0053] like Figure 1As shown, the upflow biofilm bed reactor 3 includes a water distribution device 31, a micro-aeration blower 32, a biofilm packing bed 33, a sludge baffle 34, a dissolved oxygen probe 35, a temperature sensor 36, and a pH meter 37. The upflow biofilm bed reactor is also equipped with an outlet.

[0054] The water distribution device 31 is located at the bottom of the upflow biofilm reactor 3, through which nitrogenous wastewater enters the reactor. The water distribution device 31 has multiple evenly distributed water outlets at various points at the bottom of the upflow biofilm reactor 3, ensuring that the nitrogenous wastewater enters the reactor 3 evenly and gently. The water distribution device 31 can be a rotating water distribution pipe or a tangential flow water distribution disc.

[0055] The micro-aeration blower 32 is installed at the bottom of the upflow biofilm reactor 3 and below the water distribution device 31. To ensure that oxygen dissolves as evenly as possible in the solution within the upflow biofilm reactor 3, the micro-aeration blower 32 has multiple aeration holes evenly distributed at the bottom of the upflow biofilm reactor 3. The micro-aeration blower 32 can be a microporous aeration disc or a microporous aeration pipe.

[0056] The biofilm packing bed 33 is located in the middle of the upflow biofilm bed reactor 3. The biofilm packing bed 33 includes a support frame and a fixing frame ( Figure 1 (Not shown), the fixing frame secures the support frame inside the reactor, and the support frame has a space inside to accommodate the packing material. The support frame is a spherical pore support frame or a cylindrical pore support frame. The fixing frame is a polygonal fixing frame or a cylindrical fixing frame.

[0057] The sludge baffle 34 is installed at the top of the upflow biofilm bed reactor 3, above the biofilm packing bed. The sludge baffle 34 can be one, two, or more layers of triangular plates, inclined tubes, or inclined plates. The included angle between the triangular plates can range from 45° to 70°. By setting the sludge baffle 34, a large amount of microbial sludge can be effectively blocked in the area below the sludge baffle, preventing the microbial sludge from flowing away from the outlet with the solution.

[0058] The dissolved oxygen probe 35 is positioned between the biofilm packing bed 33 and the sludge baffle 34, and is close to the biofilm packing bed 33.

[0059] One or more temperature sensors 36 are installed at the top, middle and bottom of the upflow biofilm reactor 3.

[0060] One or more pH meters 37 are installed at the top, middle and bottom of the upflow biofilm reactor 3.

[0061] The upflow biofilm reactor 3 also includes an overflow baffle 38, which is disposed above the sludge baffle 34 and close to the outlet. The overflow baffle 38 can reduce the loss of suspended direct ammonia oxidizing microorganisms in the solution.

[0062] In one aspect, the present invention provides a nitrogen-containing wastewater treatment system, comprising a raw water tank 1, an influent pump 2, an upflow biofilm reactor 3, an oxygen supply device 4, an effluent tank 5, and a pH adjustment device 6. The upflow biofilm reactor 3 is as described above. The raw water tank 1 is connected to the bottom of the upflow biofilm reactor 3. The influent pump 2 is located between the raw water tank and the upflow biofilm reactor, supplying the nitrogen-containing wastewater to be treated from the raw water tank 1 to the upflow biofilm reactor. The pH adjustment device 6 is located on the connecting pipe between the raw water tank and the upflow biofilm reactor, and adjusts the pH of the nitrogen-containing wastewater to be treated according to a pH meter 37 installed inside the upflow biofilm reactor 3.

[0063] The oxygen supply device 4 provides oxygen to the upflow biofilm reactor. The oxygen supply device 4 includes an aeration blower 41 and a controller 42. The aeration blower 41 is connected to the micro-aeration blower 32. The controller 42 is communicatively connected to the dissolved oxygen probe 35 and the aeration blower 41. The controller 42 adjusts the amount of oxygen delivered by the aeration blower 41 to the micro-aeration blower 32 according to the dissolved oxygen level detected by the dissolved oxygen probe 35.

[0064] The outlet at the top of the upflow biofilm bed reactor is connected to the effluent tank 5 to collect the treated nitrogen-containing wastewater.

[0065] In this system, nitrogen-containing wastewater is mixed in the raw water tank 1 and then pumped into the upflow biofilm reactor 3 by the inlet pump 2. The wastewater enters the upflow biofilm reactor evenly under the action of the water distribution device 31. The oxygen supply device 4 provides a stable dissolved oxygen environment for the upflow biofilm reactor, and the pH adjustment device 6 adjusts the pH environment to a suitable level. The nitrogen-containing wastewater comes into contact with the direct ammonia-oxidizing microorganisms (activated sludge) enriched on the biofilm packing bed 33. Under suitable dissolved oxygen, pH, temperature, and nutrient conditions, the direct ammonia-oxidizing microorganisms (activated sludge) directly oxidize the ammonia in the wastewater, converting the ammonia nitrogen in the wastewater into nitrogen gas for removal. In the upflow biofilm reactor 3, the direct ammonia-oxidizing microorganisms (activated sludge) washed out of the packing bed are separated from the treated nitrogen-containing wastewater by the sludge baffle 34 and returned to the reactor. The treated nitrogen-containing wastewater is discharged from the outlet at the top of the upflow biofilm reactor 3 and collected by the effluent tank 5.

[0066] In some embodiments, the ammonia nitrogen sludge load control used in this invention is 0.01–0.15 kg NH4. + -N / kgMLSS.d, preferably 0.01~0.08kgNH4 + -N / kgMLSS.d. Ammonia nitrogen sludge loading (Ns) refers to the amount of ammonia nitrogen pollutants that a unit mass of activated sludge must treat per unit time. During operation, the ammonia nitrogen sludge loading is typically controlled within a range, taking into account factors such as the C / N ratio, ammonia nitrogen concentration, temperature, and pH in the wastewater. Appropriate sludge loading is maintained to ensure system stability. Generally, the ammonia nitrogen sludge loading can be adjusted within a certain range. For example, a lower ammonia nitrogen sludge loading is used when the C / N ratio is high, a slightly higher loading is used when the ammonia nitrogen concentration is high, and the loading can be appropriately increased when pH and temperature are suitable.

[0067] Ammonia nitrogen sludge load can be calculated using the following formula:

[0068] Ns = Q × S / (V × X),

[0069] Where Ns is the ammonia nitrogen sludge load; Q is the influent flow rate; S is the ammonia nitrogen concentration; V is the effective reactor volume; and X is the activated sludge concentration. Therefore, for a reactor of a specific volume, when the influent ammonia nitrogen concentration and activated sludge concentration are limited, the ammonia nitrogen load can be controlled within a certain range by adjusting the influent flow rate.

[0070] Here, activated sludge concentration X refers to the overall average activated sludge concentration of the reactor, including free activated sludge (direct ammonia oxidizing microorganisms) and activated sludge biofilm enriched on the biofilm packing material. There are no particular limitations on the measurement method for activated sludge concentration X; it can be measured using conventional techniques, such as the gravimetric method.

[0071] In some embodiments, the average activated sludge concentration of the free activated sludge in the reactor and the activated sludge biofilm enriched on the packing material can be controlled at 6000–12000 mg / L.

[0072] The present invention will be further illustrated below with reference to embodiments / comparative examples.

[0073] Before the upflow biofilm reactor is stably operated, direct ammonia-oxidizing microorganisms are enriched by attaching to the biofilm in the upflow biofilm reactor in the following manner:

[0074] (1) Microbial proliferation: Direct ammonia oxidizing microorganisms and proliferation liquid culture medium are aerated and proliferated in the proliferation liquid tank for 10 to 15 days, pH 7.0 to 9.0, dissolved oxygen 0.5 to 1.0 mg / L, and temperature 30℃ to 35℃. After the proliferation is completed, the mixture is allowed to stand for separation.

[0075] (2) Microbial biofilm enrichment: The packing material is placed in the biofilm packing bed of the upflow biofilm reactor. Then, the activated sludge of direct ammonia oxidation microorganisms that has been settled at the bottom of the proliferating bacterial solution tank is added to the upflow biofilm reactor. Nitrogenous wastewater is introduced from the bottom of the upflow biofilm reactor. The amount of nitrogenous wastewater is controlled at 30% of the effective volume of the upflow biofilm reactor. The water inflow is stopped, and nutrient salts and trace element concentrates are added. The reaction is carried out with micro-aeration for 24-72 hours. The water inflow is continued until the wastewater volume is 60% of the effective volume of the upflow biofilm reactor. The water inflow is stopped, and nutrient salts and trace element concentrates are added. The reaction is carried out with micro-aeration for 24-72 hours. The water inflow is continued until the wastewater volume is 85% of the effective volume of the upflow biofilm reactor. The water inflow is stopped, and nutrient salts and trace element concentrates are added. The dissolved oxygen in the wastewater is controlled within the range of 0.5-1.2 mg / L. The reaction is carried out with micro-aeration for 24-72 hours. Observe the biofilm formation and enrichment of microorganisms. The process of microbial biofilm formation on the packing material is the process of microbial growth and reproduction until the surface of the packing material is covered with a biofilm. There is no particular limitation on the concentration and proportion of microorganisms or activated sludge in the biofilm packing bed. For example, when the thickness of the biofilm reaches about 1-3 mm, it can be considered that the biofilm formation and enrichment is successful. Measure the ammonia nitrogen removal rate of the system wastewater and perform bioinformatics analysis on the enriched microorganisms.

[0076] The proliferation liquid culture medium comprises elements required for microbial growth, such as carbon, nitrogen, and phosphorus, and can be prepared according to conventional microbial culture media. Preferably, the COD:N:P ratio in the proliferation liquid culture medium is (100-300):5:1.

[0077] The composition of the nutrient salt includes (g / L): KH2PO4, 0.5; NaH2PO4·12H2O, 1.25; MgSO4·7H2O, 0.2; NaCl, 6.00;

[0078] The components of the trace element concentrate include (g / L): ZnSO4·7H2O, 0.39; EDTA·2Na, 5.7; CaCl2·2H2O, 0.7; MnCl2·4H2O, 1.0; FeSO4·7H2O, 0.50; NaMoO4·2H2O, 0.22; and CoCl2·6H2O, 0.16.

[0079] Use at a ratio of 1L of nutrient salt to 2.0mL of trace element concentrate.

[0080] In such Figure 1The nitrogen-containing wastewater treatment system shown utilizes direct ammonia oxidation microorganisms to treat nitrogen-containing wastewater. Unless otherwise specified, all aspects of the system described above are referenced. The system includes a raw water tank 1, an influent pump 2, an upflow biofilm reactor 3, an oxygen supply device 4, an effluent tank 5, and a pH adjustment device 6. The raw water tank 1 is connected to the bottom of the upflow biofilm reactor 3. The influent pump 2 is located between the raw water tank 1 and the upflow biofilm reactor 3, and is used to continuously pump the nitrogen-containing wastewater to be treated from the raw water tank 1 into the upflow biofilm reactor 3. The nitrogen-containing wastewater enters the upflow biofilm reactor 3 through a water distribution device 31 located at the bottom of the reactor. In the upflow biofilm reactor 3, a dissolved oxygen probe 35 detects the dissolved oxygen content in the nitrogen-containing wastewater. The oxygen supply device 4 includes an aeration blower 41 and a controller 42. The aeration blower 41 is connected to a micro-aeration blower 32 installed at the bottom of the upflow biofilm reactor 3. The micro-aeration blower 32 ensures that oxygen is evenly dissolved in the nitrogen-containing wastewater. The controller 42 receives dissolved oxygen content data detected by the dissolved oxygen probe 35 and controls the amount of oxygen / air or other gases introduced into the upflow biofilm reactor 3 by the aeration blower 41. A temperature sensor 36 monitors the internal temperature of the upflow biofilm reactor 3; a pH meter 37 monitors the pH of the nitrogen-containing wastewater in the upflow biofilm reactor 3, and a pH adjustment device adjusts the pH of the nitrogen-containing wastewater to be treated according to the detected pH value. In the upflow biofilm bed reactor 3, nitrogen-containing wastewater comes into contact with direct ammonia-oxidizing microorganisms attached to the biofilm packing bed 33 and suspended in the reactor solution, and undergoes a direct ammonia oxidation process to treat the wastewater. The treated nitrogen-containing wastewater passes through the sludge baffle 34 and flows out from the outlet of the upflow biofilm bed reactor 3 through the overflow baffle 38, and enters the effluent tank 5 for storage and collection.

[0081] Source of materials:

[0082] Riverbed sludge: Taken from the bottom sludge of the Yongding River (Shougang Park section) and the bottom sludge of the Yongding River diversion canal (Jingouhe Road section) in Beijing.

[0083] Validation of direct ammonia oxidation microorganisms: Sludge from the Yongding River (Shougang Park section) and the bottom of the Beijing Yongding River diversion canal (Jingouhe Road section) were collected and cultured with proliferating liquid culture medium in a low-oxygen aeration tank for 10 days. After static separation, sediments were obtained. Bioinformatics analysis of the sediments showed that both the sludge from the Yongding River (Shougang Park section) and the bottom of the Beijing Yongding River diversion canal (Jingouhe Road section) contained the functional gene clusters dnf of *A. ammonioxydansHO-1* and *A. faecalis Strain JQ135*, indicating that the sludge contained microorganisms with direct ammonia oxidation (Dirammox) function.

[0084] Fe-Mn oxide filler is a porous Fe-Mn oxide filler prepared by calcination.

[0085] Bioinformatics analysis: Supported by the Institute of Science, China University of Geosciences (Beijing).

[0086] Wastewater testing: All testing methods involved refer to the "Methods for Monitoring and Analyzing Water and Wastewater (Fourth Edition)" compiled by the State Environmental Protection Administration and relevant environmental standards.

[0087] Ammonia nitrogen removal rate 100% = (influent ammonia nitrogen concentration - effluent ammonia nitrogen concentration) / influent ammonia nitrogen concentration * 100%.

[0088] Example 1

[0089] Sludge from the bottom of the Yongding River diversion canal (Jingouhe section) in Beijing, containing the functional bacterial strain gene cluster dnf, was proliferated in a low-oxygen aeration tank for 10 days, followed by static separation to obtain sediment. This sediment was then fed into an upflow biofilm reactor (UPR) equipped with Fe-Mn oxide packing material. The UPR was used to directly oxidize nitrogenous wastewater under continuous aeration and low-oxygen conditions. The UPR operated stably. As shown in Table 1, the reaction conditions in the UPR were controlled, and the COD and NH4 concentrations of the nitrogenous wastewater were adjusted. + -N concentration is 300 mg / L and C / N ratio is 300 mg / L.

[0090] Table 1. Reaction conditions and COD and NH4 concentrations of nitrogen-containing wastewater in the upflow biofilm reactor. + -N concentration

[0091]

[0092]

[0093] The reactor is continuously fed water via an influent pump, with the pump flow rate controlled to achieve continuous influent and effluent discharge. The influent ammonia nitrogen sludge load is 0.15 kg NH4. + -N / kgMLSS.d, after continuous reaction, the COD concentration and NH4+ concentration of the effluent from the upflow biofilm reactor were measured. + -N concentration, ammonia nitrogen removal rate, and the growth of miscellaneous bacteria. Because nitrite-oxidizing bacteria (nitrosomonas) and nitrobacter can remove NH4+ in an environment containing a certain amount of dissolved oxygen and organic matter. +-N is converted into nitrite and nitrate. Therefore, when nitrite and nitrate accumulate to a certain extent in the reactor, it indicates that miscellaneous bacteria are the dominant bacteria; when there is almost no accumulation of nitrite and nitrate in the reactor, it indicates that miscellaneous bacteria are not growing. The degree of nitrite and nitrate accumulation can be determined by measuring the concentration of nitrite and nitrate, thereby judging the growth status of miscellaneous bacteria. The measurement results of the effluent after nitrogen-containing wastewater treatment are shown in Table 2 below.

[0094] Table 2. Measurement results of effluent after nitrogen-containing wastewater treatment

[0095]

[0096] Example 2

[0097] Sludge from the bottom of the Yongding River (Shougang Park section) in Beijing, containing the functional bacterial strain gene cluster dnf, was proliferated in a low-oxygen aeration tank for 10 days, followed by static separation to obtain sediment. This sediment was then fed into an upflow biofilm reactor (UPR) equipped with Fe-Mn oxide packing material. Under continuous aeration and low-oxygen conditions, nitrogen-containing wastewater underwent direct ammonia oxidation treatment. The UPR operated stably. As shown in Table 3, the reaction conditions in the UPR and the concentrations of COD and NH4+ in the nitrogen-containing wastewater were controlled. + Different dissolved oxygen levels can be adjusted by adjusting N concentration, C / N ratio, temperature, and pH.

[0098] Table 3. Reaction conditions and COD and NH4 concentrations of nitrogen-containing wastewater in the upflow biofilm reactor. + -N concentration

[0099]

[0100] The reactor is continuously fed water via an influent pump, with the pump flow rate controlled to achieve continuous influent and effluent. The influent ammonia nitrogen sludge load is 0.05 kg NH4. + -N / kgMLSS.d, after continuous reaction, the COD concentration and NH4+ concentration of the effluent from the upflow biofilm reactor were measured. + -N concentration, ammonia nitrogen removal rate, and the growth of miscellaneous bacteria were measured. The results are shown in Table 4.

[0101] Table 4. Measurement results of effluent after nitrogen-containing wastewater treatment

[0102]

[0103] The B1-B2 upflow biofilm reactors showed low ammonia nitrogen removal rates in the effluent. The B1-B5 upflow biofilm reactors showed no significant accumulation of nitrite and nitrate nitrogen in the effluent. The B6-B7 upflow biofilm reactors gradually showed accumulation of nitrite and nitrate. It was found that controlling dissolved oxygen (0.6-1.2 mg / L) maintained the enrichment of direct ammonia-oxidizing microorganisms and inhibited other bacteria; excessively low dissolved oxygen (<0.6 mg / L) inhibited direct ammonia-oxidizing microorganisms, resulting in low ammonia nitrogen removal rates; excessively high dissolved oxygen (>1.2 mg / L) led to other bacterial species gradually becoming the dominant species.

[0104] Example 3

[0105] Sludge from the bottom of the Yongding River diversion canal (Jingouhe section) in Beijing, containing the functional bacterial strain gene cluster dnf, was proliferated in a low-oxygen aeration tank for 10 days, followed by static separation to obtain sediment. This sediment was then fed into an upflow biofilm reactor (UPR) equipped with Fe-Mn oxide packing material. Under continuous aeration and low-oxygen conditions, nitrogen-containing wastewater underwent direct ammonia oxidation treatment. The UPR operated stably. As shown in Table 5, the reaction conditions in the UPR reactor, as well as the COD and NH4+ concentrations of the nitrogen-containing wastewater, were controlled. + The packing ratio is adjusted by factors such as -N concentration, C / N ratio, temperature, dissolved oxygen, and pH.

[0106] Table 5. Reaction conditions and COD and NH4 concentrations of nitrogen-containing wastewater in the upflow biofilm reactor. + -N concentration

[0107]

[0108] The reactor is continuously fed water via an influent pump, with the pump flow rate controlled to achieve continuous influent and effluent. The influent ammonia nitrogen sludge load is 0.05 kg NH4. + -N / kgMLSS.d, after continuous reaction, the COD concentration and NH4+ concentration of the effluent from the upflow biofilm reactor were measured. + -N concentration, ammonia nitrogen removal rate, and the growth of miscellaneous bacteria were measured. The results are shown in Table 6.

[0109] Table 6. Measurement results of effluent after nitrogen-containing wastewater treatment

[0110]

[0111] In upflow biofilm reactor systems, the ammonia nitrogen removal rate is low without packing material, which is not conducive to the enrichment of microorganisms that directly oxidize ammonia; the ammonia nitrogen removal rate is higher when the packing material filling rate is 40% to 50%.

[0112] Example 4

[0113] Sludge from the bottom of the Yongding River diversion canal (Jingouhe section) in Beijing, containing the functional bacterial strain gene cluster dnf, was proliferated in a low-oxygen aeration tank for 10 days, followed by static separation to obtain sediment. This sediment was then fed into an upflow biofilm reactor (UPR) equipped with Fe-Mn oxide packing material. Under continuous aeration and low-oxygen conditions, nitrogen-containing wastewater underwent direct ammonia oxidation treatment. The UPR operated stably. Table 7 shows the control of reaction conditions in the UPR and the control of NH4+ in the nitrogen-containing wastewater. + -N concentration, temperature, packing material filling rate, dissolved oxygen and pH, etc., are used to adjust the COD concentration and C / N ratio of wastewater.

[0114] Table 7. Reaction conditions and COD and NH4 concentrations of nitrogen-containing wastewater in the upflow biofilm reactor. + -N concentration

[0115]

[0116]

[0117] The reactor is continuously fed water via an influent pump, with the pump flow rate controlled to achieve continuous influent and effluent discharge. The influent ammonia nitrogen sludge load is 0.01 kg NH4. + -N / kgMLSS.d, after continuous reaction, the COD concentration and NH4+ concentration of the effluent from the upflow biofilm reactor were measured. + -N concentration, ammonia nitrogen removal rate, and the growth of miscellaneous bacteria were measured. The results are shown in Table 8.

[0118] Table 8. Measurement results of effluent after nitrogen-containing wastewater treatment

[0119]

[0120] With increasing COD concentration, ammonia nitrogen removal initially increases and then decreases. When COD exceeds 600 mg / L, the ammonia nitrogen removal rate shows a significant decreasing trend. Ammonia nitrogen removal rates are higher when the C / N ratio is less than 3:1.

[0121] Example 5

[0122] Sludge from the bottom of the Yongding River (Shougang Park section) in Beijing, containing the functional bacterial strain gene cluster dnf, was proliferated in a low-oxygen aeration tank for 10 days, followed by static separation to obtain sediment. This sediment was then fed into an upflow biofilm reactor (UPR) equipped with Fe-Mn oxide packing material. Under continuous aeration and low-oxygen conditions, nitrogen-containing wastewater underwent direct ammonia oxidation treatment. The UPR operated stably. As shown in Table 9, the reaction conditions in the UPR were controlled, including the COD concentration, temperature, packing material filling rate, dissolved oxygen, and pH of the nitrogen-containing wastewater. The NH4+ in the wastewater was also adjusted. + -N concentration and C / N ratio.

[0123] Table 9. Reaction conditions and COD and NH4 concentrations of nitrogen-containing wastewater in the upflow biofilm reactor. + -N concentration

[0124]

[0125] The reactor is continuously fed water via an influent pump, with the pump flow rate controlled to achieve continuous influent and effluent discharge. The influent ammonia nitrogen and sludge load is 0.08 kg NH4. + -N / kgMLSS.d, after continuous reaction, the COD concentration and NH4+ concentration of the effluent from the upflow biofilm reactor were measured. + -N concentration, ammonia nitrogen removal rate, and the growth of miscellaneous bacteria were measured. The results are shown in Table 10.

[0126] Table 10. Measurement results of effluent after nitrogen-containing wastewater treatment

[0127]

[0128]

[0129] With NH4 + With increasing -N concentration, ammonia nitrogen removal initially stabilizes and then decreases, indicating that direct ammonia-oxidizing microorganisms have a high tolerance for ammonia nitrogen. NH4 + When -N exceeds 1000 mg / L, the ammonia nitrogen removal rate shows a significant decreasing trend.

[0130] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0131] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for treating nitrogen-containing wastewater based on direct ammonia oxidation, characterized in that, The method utilizes direct ammonia-oxidizing microorganisms in an upflow biofilm reactor to directly convert ammonia nitrogen in nitrogen-containing wastewater into nitrogen gas. The nitrogen-containing wastewater has an ammonia nitrogen concentration of 50–1200 mg / L, a COD concentration of 50–1600 mg / L, and a C / N ratio of (0.5–10.0):1; preferably, the ammonia nitrogen concentration is 80–1000 mg / L, the COD concentration is 100–1600 mg / L, and the C / N ratio is (0.5–6.0):1; more preferably, the ammonia nitrogen concentration is 200–800 mg / L, the COD concentration is 150–600 mg / L, and the C / N ratio is (0.75–2.5):

1. The internal temperature of the upflow biofilm bed reactor is 20℃~37℃; The dissolved oxygen level inside the upflow biofilm bed reactor is 0.5–1.5 mg / L, preferably 0.6–1.2 mg / L, and more preferably 0.8–1.0 mg / L; The pH inside the upflow biofilm bed reactor is 7.5–10.

0.

2. The method according to claim 1, characterized in that, The direct ammonia oxidizing microorganism is a microorganism carrying the Dirammox functional strain gene cluster dnf and capable of direct ammonia oxidation; preferably Alcaligenes ammonioxydansHO-1 and / or Alcaligenes faecalis Strain JQ135; preferably, the direct ammonia oxidizing microorganism comes from soil, river sediments or activated sludge from a sewage treatment plant.

3. The method according to claim 1, characterized in that, The packing material in the upflow biofilm reactor is Fe-Mn oxide packing material.

4. The method according to claim 3, characterized in that, The packing material is filled at a rate of 30%-60% of the effective volume of the reactor, preferably 30%-50%, and more preferably 40%-50%.

5. The method according to any one of claims 1 to 4, characterized in that, The upflow biofilm bed reactor includes a water distribution device, a micro-aeration blower, a biofilm packing bed, a sludge baffle, a dissolved oxygen probe, a temperature sensor, and a pH meter. The upflow biofilm bed reactor is also equipped with an outlet at the top. The water distribution device is located at the bottom of the upflow biofilm bed reactor. The nitrogen-containing wastewater enters the upflow biofilm bed reactor through the water distribution device. The water distribution device is a rotary water distribution pipe or a tangential water distribution disc. The micro-aeration blower is installed at the bottom of the upflow biofilm bed reactor and below the water distribution device. The micro-aeration blower is a microporous aeration disc or a microporous aeration pipe. The biofilm packing bed is located in the middle of the upflow biofilm bed reactor; The sludge baffle is installed at the top of the upflow biofilm bed reactor, above the biofilm packing bed. The sludge baffle is one, two, or more layers of triangular plates, inclined tubes, or inclined plates. The dissolved oxygen probe is positioned between the biofilm packing bed and the sludge baffle, and is close to the biofilm packing bed; One or more temperature sensors are provided at the upper, middle and / or lower parts of the upflow biofilm bed reactor; One or more pH meters are installed in the upper, middle and / or lower part of the upflow biofilm reactor.

6. The method according to claim 5, characterized in that, The upflow biofilm bed reactor also includes an overflow baffle, which is disposed between the effluent outlet and the sludge baffle; And / or, the biofilm packing bed includes a support frame and a fixing frame, the fixing frame fixing the support frame inside the upflow biofilm bed reactor, and the support frame having a space for accommodating the packing material; The support frame is a spherical pore support frame or a cylindrical pore support frame; The fixing frame is a polygonal fixing frame or a columnar fixing frame.

7. The method according to claim 5, characterized in that, The direct ammonia-oxidizing microorganisms are enriched by attaching to a biofilm in the upflow biofilm reactor through the following steps: (1) Microbial proliferation: Direct ammonia oxidizing microorganisms and proliferation liquid culture medium are aerated and proliferated in the proliferation liquid tank for 10 to 15 days, pH 7.0 to 9.0, dissolved oxygen 0.5 to 1.0 mg / L, temperature 30 to 35℃. After the proliferation is completed, the mixture is allowed to stand for separation. (2) Microbial biofilm enrichment: The packing material is placed in the biofilm packing bed, and then the statically settled direct ammonia oxidation microbial activated sludge from the bottom of the proliferating bacterial liquid tank is added to the upflow biofilm bed reactor. Nitrogenous wastewater is introduced from the bottom of the upflow biofilm bed reactor, and the amount of nitrogenous wastewater is controlled at 30% to 40% of the effective volume of the upflow biofilm bed reactor. The water inflow is stopped, and nutrient salts and trace element concentrates are added. The reaction is carried out with micro-aeration for 24 to 72 hours. The water inflow continues until the wastewater volume reaches 60% to 70% of the effective volume of the upflow biofilm bed reactor. The water inflow is stopped, and the nutrient salts and trace element concentrates are added. The dissolved oxygen in the wastewater is controlled within the range of 0.5 to 1.2 mg / L. The reaction is carried out with micro-aeration for 24 to 72 hours. The water inflow continues until the wastewater volume reaches 85% to 95% of the effective volume of the upflow biofilm bed reactor. The water inflow is stopped, and the nutrient salts and trace element concentrates are added. The reaction is carried out with micro-aeration for 24 to 72 hours. And / or, in step (2), the dosage of the direct ammonia oxidation microbial activated sludge is 4-10 g MLSS / L.

8. The method according to claim 7, characterized in that, The nutrient salt composition includes: 0.5 g / L KH2PO4; 1.25 g / L NaH2PO4·12H2O; 0.2 g / L MgSO4·7H2O; 6.00 g / L NaCl; The components of the trace element concentrate include: 0.39 g / L ZnSO4·7H2O; 5.7 g / L LEDTA·2Na; 0.7 g / L CaCl2·2H2O; 1.0 g / L MnCl2·4H2O; 0.50 g / L FeSO4·7H2O; 0.22 g / L NaMoO4·2H2O; and 0.16 g / L CoCl2·6H2O; Add 2.0 mL of the trace element concentrate to each liter of the nutrient salts.

9. The method according to claim 5, characterized in that, In the upflow biofilm bed reactor, the average activated sludge concentration is controlled at 6000–12000 mg / L; And / or, the ammonia nitrogen sludge load is controlled at 0.01–0.15 kg NH4. + -N / kgMLSS.d, preferably 0.01~0.08kgNH4 + -N / kgMLSS.d.

10. A nitrogen-containing wastewater treatment system, characterized in that, The system includes a raw water tank, an inlet pump, an upflow biofilm reactor, an oxygen supply device, an outlet tank, and a pH adjustment device. The upflow biofilm bed reactor includes a water distribution device, a micro-aeration blower, a biofilm packing bed, a sludge baffle, a dissolved oxygen probe, a temperature sensor, and a pH meter. The upflow biofilm bed reactor is also equipped with an outlet at the top. The water distribution device is located at the bottom of the upflow biofilm bed reactor. The nitrogen-containing wastewater enters the upflow biofilm bed reactor through the water distribution device. The water distribution device is a rotary water distribution pipe or a tangential water distribution disc. The micro-aeration blower is installed at the bottom of the upflow biofilm bed reactor and below the water distribution device. The micro-aeration blower is a microporous aeration disc or a microporous aeration pipe. The biofilm packing bed is located in the middle of the upflow biofilm bed reactor; The sludge baffle is installed at the top of the upflow biofilm bed reactor, above the biofilm packing bed. The sludge baffle is one, two, or more layers of triangular plates, inclined tubes, or inclined plates. The dissolved oxygen probe is positioned between the biofilm packing bed and the sludge baffle, and is close to the biofilm packing bed; One or more temperature sensors are provided at the upper, middle and / or lower parts of the upflow biofilm bed reactor; One or more pH meters are installed in the upper, middle and / or lower part of the upflow biofilm bed reactor; The raw water tank is connected to the bottom of the upflow biofilm reactor, and the inlet pump is installed on the connecting pipe between the raw water tank and the upflow biofilm reactor to supply nitrogen-containing wastewater to be treated into the upflow biofilm reactor. The oxygen supply device provides oxygen to the upflow biofilm bed reactor; the oxygen supply device includes an aeration blower and a controller, the aeration blower is connected to the micro aeration blower, the controller is communicatively connected to the dissolved oxygen probe and the aeration blower, and the controller adjusts the amount of oxygen delivered by the aeration blower to the micro aeration blower according to the dissolved oxygen amount detected by the dissolved oxygen probe. The pH adjustment device is installed on the connecting pipe between the raw water tank and the upflow biofilm reactor to adjust the acidity and alkalinity of the nitrogen-containing wastewater to be treated. The outlet at the top of the upflow biofilm bed reactor is connected to the effluent tank to collect the treated nitrogen-containing wastewater. Preferably, the upflow biofilm reactor further includes an overflow baffle, which is disposed between the effluent outlet and the sludge baffle; And / or, the biofilm packing bed includes a support frame and a fixing frame, the fixing frame fixing the support frame inside the reactor, and the support frame having a space for accommodating the packing material; The support frame is a spherical pore support frame or a cylindrical pore support frame; The fixing frame is a polygonal fixing frame or a columnar fixing frame.

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