A device and method for realizing directional conversion of nitro nitrogen into nitrous oxide by using a denitrification biofilter

Abstract

This invention discloses a method for achieving NO reduction using a denitrification biological filter. 3 ‑ -N-directed conversion N 2 An apparatus and method for producing O. The apparatus includes a biofilm reactor and N. 2 O collection device; the biofilm reactor is a denitrifying biofilter, which is equipped with denitrifying biofilm packing material. The area of ​​the denitrifying biofilm packing material is the liquid-phase biological reaction producing N. 2 Zone O, the area between the denitrification biofilm packing and the top of the biofilm reactor, serves as the gaseous N2 phase. 2 O separation zone; the bottom of the denitrifying biological filter has an inlet for introducing water to be treated, and the top of the denitrifying biological filter has an outlet for discharging treated water; the top of the denitrifying biological filter is connected to an N... 2 O collection device, used to collect N produced in the denitrification biological filter. 2 O. This invention achieves nitrogen enrichment through microbial community enrichment, adjustment of operating parameters and influent water quality, such as setting filtration rate, reaction time, carbon source and carbon-to-nitrogen ratio, low pH value, and stripping. 2 The enrichment and recovery of O does not require setting an excessively low pH value, which reduces the dosage and lowers operating costs.

Description

An apparatus and method for the directional conversion of nitrate nitrogen to nitrous oxide using a denitrifying biological filter. Technical Field

[0001] This invention relates to a method for achieving NO3 reduction using a denitrification biological filter. - The apparatus and method for the directional conversion of -N to N2O belong to the field of environmental and resource recycling technology. Background Technology

[0002] Biological denitrification is an essential step in wastewater treatment, and it is also required by some water treatment plants that use groundwater as their source. Traditional biological denitrification uses the nitrification-denitrification principle to convert ammonia nitrogen into N2 and release it into the atmosphere. However, this process also releases the greenhouse gas N2O. In recent years, studies have found that N2O is also a potential renewable energy source. For example, when it replaces oxygen as a combustion improver, it can increase the calorific value of methane combustion by 37%. Therefore, the energy utilization of nitrogen in wastewater treatment processes is attracting increasing attention.

[0003] Although almost all nitrogen removal processes (e.g., nitrification, denitrification, cut-cut nitrification, cut-cut denitrification, anaerobic ammonium oxidation, etc.) release N2O, studies have shown that N2O is a byproduct and intermediate product of nitrogen removal processes, and cut-cut nitrification and denitrification are two important biological processes that release N2O. Therefore, achieving a high degree of N2O conversion during cut-cut denitrification is crucial for nitrogen-to-energy conversion in wastewater treatment. However, under traditional equipment and control conditions, the amount of N2O released during denitrification is very small, making it difficult to enrich and collect for utilization. Summary of the Invention

[0004] The purpose of this invention is to provide a method for achieving NO3 reduction using a denitrification biological filter. - The apparatus and method for the directional conversion of -N to N2O provide a basis for the energy utilization of nitrogen in wastewater treatment processes.

[0005] This invention combines a denitrification filter with a biofilm to construct an N2O recovery device for a denitrification biological filter. Through specific microbial community enrichment, process parameter regulation, and inhibition of N2O reductase activity, as well as the separation of N2O produced by incomplete denitrification, the N2O generated in the water treatment plant is ultimately recovered. - The purpose of -N directional conversion to N2O.

[0006] First, the present invention provides a method for achieving NO3 reduction using a denitrification biological filter. - A device for the directional conversion of -N to N2O, including a biofilm reactor and an N2O collection device;

[0007] The biofilm reactor is a denitrifying biofilter, and the denitrifying biofilter is equipped with denitrifying biofilm packing. The area of ​​the denitrifying biofilm packing is the liquid phase biological reaction N2O production zone, and the area between the denitrifying biofilm packing and the top of the biofilm reactor is the gas phase N2O separation zone.

[0008] The denitrifying biological filter is provided with an inlet at the bottom for introducing wastewater to be treated, and an outlet at the top for discharging treated water.

[0009] The top of the denitrifying biological filter is connected to an N2O collection device for collecting the N2O generated in the denitrifying biological filter.

[0010] The denitrifying biofilm packing material is a biological ceramic particle with an average particle size of 0.4–0.6 μm.

[0011] The N2O collection device is connected in sequence to the dryer, the vacuum pump, and the gas collection box.

[0012] Based on the aforementioned device, the present invention provides an implementation of NO3. - The method for directional conversion of -N to N2O includes the following steps:

[0013] S1. Inoculate the denitrifying biofilm packing material in the device with sludge mainly composed of Thaurea linaloolentis, and the biofilm attaches and grows on the surface of the denitrifying biofilm packing material.

[0014] S2. Wastewater to be treated is introduced into the denitrification biological filter through the inlet, and N2O is generated in the liquid phase biological reaction N2O production zone.

[0015] S3. Collect the N2O generated in the N2O production zone of the liquid-phase biological reaction using the N2O collection device;

[0016] That is, to achieve the separation and collection of N2O in the gas phase N2O separation zone;

[0017] The N2O production zone of the liquid-phase bioreactor and the N2O separation zone have the same material flow direction;

[0018] The organic matter added to the wastewater is glucose, and the organic matter reacts with NO3. - The ratio of -N is: COD / N is 1.5 to 2.5.

[0019] In the above method, in step S2, the pH value of the wastewater is adjusted to 6.0-6.5 by adding hydrochloric acid.

[0020] In the above method, in step S2, the speed at which the wastewater passes through the denitrifying biofilm packing is controlled to be 1.4 to 1.6 m / h, preferably 1.5 m / h;

[0021] Within the N2O production zone of the liquid-phase biological reaction, the denitrification biofilm packing material is in full contact with the influent, thereby controlling the amount of organic matter and NO3 in the influent. - The ratio of -N and the pH of the influent are used to utilize the matrix mass transfer due to the biofilm thickness and the insufficient carbon source supply to inhibit the activity of N2O reductase, thereby reducing NO3-. - -N reduction products are controlled to be N2O.

[0022] In the above method, in step S3, the negative pressure of the gas phase N2O separation zone is controlled to be 0.05 to 0.1 MPa.

[0023] The negative pressure in the N2O separation process allows for timely separation of liquid N2O, achieving an N2O conversion rate of over 80% in a stable denitrification biological filter. The N2O is then collected by the N2O collection device, achieving a high degree of enrichment and recovery of N2O.

[0024] In the above method, the process of generating N2O in step S2 lasts for 6 to 7 hours;

[0025] The process of separating and collecting N2O in step S3 lasts for 1 to 2 hours;

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] Incomplete denitrification is achieved by adding specific N2O-producing microbial communities, biological packing materials, and controlling parameters, while inhibiting the activity of N2O reductase, thereby controlling NO3. - The reduction product of -N is N2O;

[0028] The negative pressure during N2O separation separates the N2O generated in the biofilm reaction zone, further creating suitable growth conditions for N2O-producing denitrifying bacteria, ultimately achieving an N2O conversion rate of over 80%, which further improves the N2O conversion rate. Here, the N2O conversion efficiency refers to the proportion of N2O generated to the total nitrogen load of the influent.

[0029] This invention achieves N2O enrichment and recovery by enriching microbial communities and adjusting operating parameters and influent water quality, such as setting filtration rate, reaction time, carbon source and carbon-nitrogen ratio, low pH value and stripping. It eliminates the need to set excessively low pH values, reduces the dosage of chemicals and lowers operating costs. Attached Figure Description

[0030] Figure 1 shows the NO3 reduction process achieved by the denitrification biological filter of this invention. - A schematic diagram of the structure of a device for the directional conversion of -N to N2O;

[0031] Figure 2 shows the NO3 reaction using the device of the present invention. - - The conversion rate of N2O during the directional conversion of N-type N2O.

[0032] Figure 3 shows the N2O conversion rate when using different carbon sources.

[0033] The markings in the diagram are as follows:

[0034] 1. Inlet tank; 2. Peristaltic pump; 3. Denitrifying biological filter; 4. Inlet / outlet; 5. Packing material outlet; 6. Gravel; 7. Biological packing material; 8. N2O collection hood; 9. Dryer; 10. Vacuum pump; 11. Gas collection box; 12. Valve. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.

[0036] Figure 1 shows the NO3 reduction method for water treatment plants using a denitrification biological filter provided by this invention. - The apparatus for the directional conversion of -N to N2O includes an inlet tank 1, a peristaltic pump 2, a denitrifying biological filter 3, an inlet / outlet 4, a packing material outlet 5, gravel 6, biological packing material 7, an N2O collection hood 8, a dryer 9, a vacuum pump 10, a gas collection box 11, and valves 12. The denitrifying biological filter 3 has an inlet / outlet 4 and a packing material outlet 5 on its side wall. The biological packing material 7, with an average particle size of 4–6 μm, is arranged inside the denitrifying biological filter 3. Gravel 6 is placed at the bottom as a support layer to support the filter media, prevent filter media loss, and filter out some coarse impurities. The area of ​​the biological packing material 7 serves as the liquid-phase biological reaction zone for N2O production, and the upper space of the biological packing material 7 (i.e., the blank area shown in the figure) serves as the gas-phase N2O separation zone. The bottom of the denitrifying biological filter 3 is connected to the peristaltic pump 2 and the inlet tank 1. The top of the denitrification biological filter 3 is equipped with an N2O collection hood 8, which is used to collect the N2O separated in the gas phase N2O separation zone. The N2O collection hood 8 is connected in sequence to a dryer 9, a vacuum pump 10 and an N2O gas collection box 11. A valve 12 is provided on the N2O collection pipeline.

[0037] The device of this invention removes NO3 from wastewater - When N2O is directionally converted from N, the N2O production process is first carried out on the biological packing 7 (liquid phase biological reaction N2O production zone). Then, the N2O produced is separated in the gas phase N2O separation zone. The production and separation effect of N2O can be promoted by controlling the time of the two processes (e.g., 6-7 hours for the liquid phase biological reaction N2O production process and 1-2 hours for the gas phase N2O separation process).

[0038] In addition, the N2O production process via liquid-phase biological reaction requires controlling the addition of glucose as the carbon source, and limiting the amount of organic matter and NO3 in the influent. - The ratio of -N to COD / N is 1.5 to 2.5, with the aim of reducing NO3. - The partial reduction of -N provides a suitable electron donor to ensure the continuous production of N2O by microorganisms. The pH of the influent is controlled at 6.0-6.5 by adding 0.1 mol / L hydrochloric acid. The purpose is to create suitable growth conditions for N2O-reducing bacteria so that there is a sufficient amount of microorganisms in the liquid phase reaction process to ensure the reaction rate of incomplete denitrification to produce N2O.

[0039] The method of this invention inhibits the activity of N2O reductase by adjusting the pH, thereby reducing NO3-. - -N reduction products are controlled to N2O to prevent excessive reduction to nitrogen gas; the negative pressure in the gas phase zone is controlled to be 0.05-0.1 MPa by a vacuum pump, with the aim of separating the generated N2O from the denitrification biological filter 3.

[0040] Experiments have verified that by using methods such as microbial enrichment and parameter control to inhibit the activity of N2O reductase and simultaneously separate N2O in a timely manner, after 30 consecutive days of operation, the N2O conversion rate reaches more than 80%, achieving a high degree of N2O enrichment and recovery.

[0041] Specifically, the apparatus shown in Figure 1 is used to process NO3. - The conversion of -N to N2O was carried out in the denitrification biological filter 3. The average particle size of the biological packing material 7 arranged in the denitrification biological filter 3 was 4-6 μm. Short-cut denitrification sludge was inoculated into the biological packing material 7. The denitrification biological filter 3 was divided into a biological reaction N2O production zone and a gas phase N2O separation zone. The N2O production time in the biological reaction N2O production zone was 7 hours, and the N2O separation time in the gas phase N2O separation zone was 1 hour. The pH of the influent was controlled to be 6.0-6.5 by adding 0.1 mol / L hydrochloric acid. After successful biofilm formation, the negative pressure in the gas phase zone (i.e., the gas phase N2O separation zone) was controlled to be 0.05-0.1 MPa by a vacuum pump. The N2O conversion efficiency of the system was measured periodically during the process, and the results are shown in Figure 2.

[0042] As shown in Figure 2, the initial N2O conversion rate was low at only 0.9%. With the inhibition of N2O reductase activity and the separation of N2O from the reactor, the growth conditions of N2O-producing bacteria in the liquid phase were enhanced, and the N2O conversion rate gradually increased. By day 16, it had increased to 39.5%. By day 30, the N2O conversion rate reached 80.1% and gradually stabilized, indicating that nitrate was highly reduced to N2O.

[0043] The sludge inoculated into the long-term operating denitrifying biological filter of this invention was thauera linaloolentis, with the main microbial community being Thaurera linaloolentis. The specific experimental procedure was as follows:

[0044] The experimental setup consisted of serum bottles sealed with butyl rubber stoppers and aluminum caps, and a constant-temperature water bath shaker. Denitrification media were prepared using ethanol, sodium acetate, glucose, and sodium citrate as the sole carbon source (TOC = 900 mg / L), and KNO3 and NH4Cl at the same concentration (150 mg / L, N) as nitrogen sources. PBS buffer was used as a phosphorus source, and the pH was maintained at approximately 7.0. Multiple replicates were set up for each experimental group.

[0045] 200 mL of denitrification medium was measured and placed into serum bottles. Since denitrification requires anaerobic conditions, the serum bottles were sealed with butyl rubber stoppers, headspace air was evacuated using a syringe, and then an equal volume of nitrogen gas was added to the serum bottles. The results are shown in Figure 3. It is clearly observed that glucose, as the carbon source, produced the highest concentration of N2O. This invention selects glucose as the carbon source because its N2O production performance is superior to other conventional carbon sources (sodium acetate, methanol, etc.).

Claims

1. A method for achieving NO3 reduction using a denitrification biological filter. - The method for the directional conversion of -N to N2O is characterized by: The method utilizes a biofilm reactor and an N2O collection device. The biofilm reactor is a denitrifying biofilter, which contains denitrifying biofilm packing material. The area of ​​the denitrifying biofilm packing material is the liquid-phase biological reaction N2O production zone, and the area between the denitrifying biofilm packing material and the top of the biofilm reactor serves as the gas-phase N2O separation zone. The bottom of the denitrifying biofilter has an inlet for introducing water to be treated, and the top of the denitrifying biofilter has an outlet for discharging treated water. An N2O collection device is connected to the top of the denitrifying biofilter to collect the N2O generated within the denitrifying biofilter. The method includes the following steps: S1, inoculating the denitrifying biofilm packing material in the device with Thaurae. The process involves: S1) Sludge primarily composed of *Linaloolentis*; S2) Introducing treated water into the denitrification biological filter through the inlet, generating N2O in the liquid-phase biological reaction N2O production zone; In step S2, adjusting the pH of the treated water to 6.0-6.5 by adding hydrochloric acid; controlling the flow rate of the treated water through the denitrification biofilm packing material to 1.4-1.6 m / h; S3) Collecting the N2O generated in the liquid-phase biological reaction N2O production zone using the N2O collection device; In step S3, controlling the negative pressure in the gas-phase N2O separation zone to 0.05-0.1 MPa; controlling the added carbon source to be glucose, and controlling the organic matter and NO3 in the water... - The ratio of -N is: COD / N is 1.5~2.5; the process of generating N2O in step S2 lasts for 6~7 hours; the process of separating and collecting N2O in step S3 lasts for 1~2 hours.

2. The method according to claim 1, characterized in that: The denitrification biofilm packing material is bio-ceramic granules with an average particle size of 0.4–0.6 μm.

3. The method according to claim 1 or 2, characterized in that: The N2O collection device is connected in sequence to the dryer, the vacuum pump, and the gas collection box.

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