Denitrification reactor

Abstract

The invention relates to the technical field of sewage treatment, in particular to a denitrification reactor. A plurality of denitrification units which are connected in series are adopted, the number of denitrification nitrogen elements can be reasonably started according to the total nitrogen amount, and meanwhile the situation that water distribution is affected at the high linear speed is overcome. Each denitrification unit is filled with a denitrification filler; the denitrification filler comprises the following raw materials in percentage by mass: 20-30% of powdered activated carbon, 10-20% of slaked lime powder, 2% of magnesium sulfate, 5% of a sodium silicate solution, 0.5% of ferric oxide powder, 50% of clay and the balance of water. The denitrification filler disclosed by the invention is biofilm-formed and then is filled into a denitrification unit, relatively high denitrification efficiency can still be achieved at a relatively low carbon-nitrogen ratio, on one hand, the filler disclosed by the invention can adsorb COD to form a local high-concentration COD state, and on the other hand, the filler is also beneficial to adhesion of denitrifying bacteria, so that the denitrification efficiency is improved, and the denitrification efficiency is improved. Wide popularization and application prospects are realized.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically to a denitrification reactor. Background Technology

[0002] Most wastewater treatment plants receive wastewater with low carbon and nitrogen ratios (generally COD / TN < 5), lacking carbon sources. Carbon sources can affect the denitrification process, thus affecting the compliance of wastewater discharge with standards. In engineering practice, in addition to supplementing carbon sources, it is also necessary to find ways to improve the utilization rate of carbon sources.

[0003] Carbon sources in wastewater serve approximately three functions: aiding in scale release, assisting in nitrogen removal, and generating biomass such as flocs. Traditional denitrification involves a clump of sludge. In the anaerobic zone, polyphosphate-accumulating bacteria absorb BOD (carbon source) and release phosphate. In the anoxic zone, three reactions occur simultaneously: 1) Polyphosphate-accumulating bacteria, relying on internally recirculated dissolved oxygen, begin to excessively absorb phosphate while consuming BOD; 2) Denitrifying bacteria begin to denitrify nitrate into nitrite nitrogen, ultimately nitrogen gas, while consuming at least four times the amount of BOD; 3) Aerobic and facultative anaerobic bacteria, represented by flocs, utilize the limited oxygen in the water to oxidize BOD into carbon dioxide and water, while simultaneously synthesizing their own biomass. Once this sludge clump reaches the aerobic zone, the nitrifying bacteria on the flocs begin to work, oxidizing ammonia nitrogen and causing rapid biomass growth.

[0004] BOD is always scarce, and adding it is too economical. Therefore, this invention proposes a denitrification reactor. By developing a packing material that adsorbs BOD, BOD is rapidly adsorbed onto the packing material, forming a localized high BOD concentration environment. The denitrifying bacteria attached to the packing material are in close contact with the high-concentration BOD environment. Due to the absence or minimal participation of other bacteria, the denitrifying bacteria have an absolute advantage in competing for BOD, resulting in a very fast reaction rate. The limited BOD is quickly adsorbed onto the packing material rich in denitrifying bacteria, and the two react to produce carbon dioxide and water, thus achieving a highly efficient denitrification process with low BOD concentration. Summary of the Invention

[0005] The purpose of this invention is to provide a denitrification reactor to solve the problems of low carbon-to-nitrogen ratio and low denitrification efficiency in existing wastewater, which necessitates the addition of additional carbon sources and increases treatment costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a denitrification reactor, comprising multiple closed denitrification units connected in series, each denitrification unit being filled with denitrification packing material;

[0007] The denitrification packing material, by mass percentage, comprises 20-30% powdered activated carbon, 10-20% quicklime powder, 2% magnesium sulfate, 5% sodium silicate solution, 0.5% iron oxide powder, 50% clay, and the balance being water.

[0008] Furthermore, an inlet is provided below the denitrification packing in the denitrification unit, and an outlet is provided above the denitrification packing. The outlet of the previous denitrification unit is connected to the inlet of the next denitrification unit through a connecting pipe.

[0009] Furthermore, it also includes a main water inlet pipe, which is connected to multiple branch water inlet pipes. Each branch water inlet pipe is connected to the inlet of the corresponding denitrification unit. A control valve is installed on each branch water inlet pipe, and a control valve is installed on the connecting pipes on both sides of the connection between each branch water inlet pipe and the corresponding connecting pipe.

[0010] Furthermore, each of the denitrification units has a sedimentation zone at its bottom, and each sedimentation zone is connected to a corresponding sewage branch pipe, which is connected to the main sewage pipe; each sewage branch pipe is equipped with a control valve.

[0011] Furthermore, each of the denitrification units is equipped with a top cover, and each top cover is connected to a corresponding extraction branch pipe. The extraction branch pipe is connected to the main extraction pipe, and a control valve is installed on each extraction branch pipe.

[0012] Furthermore, a drain pipe is installed between the main exhaust pipe and the main sewage pipe, and a control valve is installed on the drain pipe.

[0013] Furthermore, in the raw materials for the denitrification filler, the powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder, and clay all pass through a 200-400 mesh sieve; the mass fraction of the sodium silicate solution is 30-50%.

[0014] The preparation of denitrification packing material includes the following steps:

[0015] S1. Mix powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder and clay evenly, add sodium silicate solution and water, mix evenly and then granulate to obtain filler particles.

[0016] S2. First, air dry the S1 packing particles in a cool, dry place, and then air dry them in an outdoor dry place to obtain the denitrification packing of the present invention.

[0017] Furthermore, the filler particles have a particle size of 6-8 mm. The filler particles are first air-dried in a cool, dry place for 1 week, and then air-dried in an outdoor dry place for 2 weeks.

[0018] Furthermore, the denitrification packing is soaked in the effluent tank of the secondary sedimentation tank, and after biofilm formation, it is filled into the denitrification unit; the denitrification unit has a diameter of 250 mm and a height of 1300 mm; the filling height of the denitrification packing is 1000 mm, and the porosity is 30-35%; the flow rate in the denitrification unit is 600-650 mL / min.

[0019] The beneficial effects of this invention are:

[0020] This invention develops a COD-adsorbing packing material. In the treatment of low C / N ratio wastewater, the packing material adsorbs COD, creating a locally high-COD environment, which facilitates denitrification and promotes the attachment of denitrifying bacteria, further improving denitrification efficiency. It achieves highly efficient removal of nitrate nitrogen from low C / N ratio wastewater. Experiments show that the denitrification reactor reduces the commonly held belief that a C / N ratio of 4-5:1 is necessary for biological denitrification to only 3-4:1. By using a high influent velocity and controlling negative pressure venting, the accumulation of air bubbles in the packing layer is effectively avoided, ensuring timely discharge of reaction products and the stability of the packing layer. This invention is of great significance for the research and treatment of low C / N ratio wastewater. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the denitrification reactor layout of the present invention.

[0022] The names corresponding to each mark in the diagram:

[0023] 1. Denitrification unit; 11. Sedimentation zone; 12. Top cover; 13. Packing material; 2. Main inlet pipe; 21. Branch inlet pipe; 3. Main exhaust pipe; 31. Branch exhaust pipe; 4. Main drain pipe; 41. Branch drain pipe; 5. Drainage pipe. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0025] like Figure 1 As shown, the denitrification reactor of the present invention includes multiple denitrification units connected in series. Each denitrification unit is filled with packing material, a sedimentation zone is provided at the bottom of each denitrification unit, and a top cover is provided at the top of each denitrification unit.

[0026] An inlet is provided below the packing material in the denitrification unit, and an outlet is provided above the packing material. The outlet of the previous denitrification unit is connected to the inlet of the next denitrification unit through a connecting pipe. A main inlet pipe is provided, which is connected to each branch inlet pipe. Each branch inlet pipe is connected to the inlet of the corresponding denitrification unit. A control valve is provided on each branch inlet pipe, and control valves are provided on the connecting pipes on both sides of the connection between the branch inlet pipe and the connecting pipe.

[0027] The top cover of each denitrification unit is connected to the corresponding extraction branch pipe. Each extraction branch pipe is equipped with a control valve and is connected to the main extraction pipe.

[0028] The sedimentation zone at the bottom of each denitrification unit is connected to the corresponding sewage branch pipe. Each sewage branch pipe is equipped with a control valve and is connected to the main sewage pipe. The main exhaust pipe is connected to the main sewage pipe through a drain pipe, which is equipped with a control valve.

[0029] The principle of this invention is as follows:

[0030] Preparation of the packing material in the denitrification unit of this invention:

[0031] The filler of this invention comprises the following components by weight percentage: 20-30% powdered activated carbon, 10-20% quicklime powder, 2% magnesium sulfate, 5% sodium silicate solution, 0.5% iron oxide powder, 50% clay, and the balance being water.

[0032] Among them, powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder, and clay all pass through a 200-400 mesh sieve; the mass fraction of sodium silicate solution is 30-50%.

[0033] Mix powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder and clay evenly, then add sodium silicate solution and replenish the remaining water, mix evenly and form small balls of 6-8 mm; air dry in a cool place for 1 week, and then air dry outdoors for 2 weeks to obtain the filler of the present invention.

[0034] The packing material of this invention is soaked in the effluent tank of the secondary sedimentation tank for one week to form a biofilm, and then it can be filled into the denitrification unit of this invention. The packing material of this invention has the function of adsorbing COD in wastewater and is also suitable for denitrification.

[0035] Wastewater containing COD and nitrate nitrogen is fed into the main inlet pipe. The wastewater has a low carbon-to-nitrogen ratio and flows through each denitrification unit in sequence. During the treatment process, the COD in the wastewater is adsorbed at the packing material, forming a local high-concentration COD environment. At this time, the denitrifying bacteria on the packing material use the COD in the wastewater as a carbon source to achieve the denitrification process.

[0036] During operation, if the gas produced by denitrification cannot be discharged in time, it will cause the gas to not form a large gas bubble in the packing, resulting in water flow turbulence and a decrease in reaction rate; in severe cases, the gas bubble will burst out and overflow, affecting the normal operation of the reactor. Therefore, the gas is pumped to the odor treatment system through each gas extraction branch pipe and the gas extraction main pipe. At the same time, the flow line is designed with a high flow rate to avoid the accumulation of gas bubbles.

[0037] During operation, impurities in the wastewater, such as detached packing particles, settle and collect in the sedimentation zone. They are periodically emptied through the branch and main sewage pipes. Water entrained in the gas in the extraction main pipe is separated by the gas-water separator and discharged through the main sewage pipe. In addition, the intake water can be controlled by adjusting the valves on each inlet branch pipe, thereby enabling maintenance of the denitrification unit.

[0038] Example 1

[0039] The denitrification unit in the denitrification reactor of this embodiment is prepared. In this embodiment, all denitrification units have the same specifications. The diameter of the denitrification unit is 250 mm, the height is 1300 mm, the height of the packing layer is 1000 mm, the packing volume is about 50 L, and the packing porosity is 32%.

[0040] In this embodiment, five denitrification units are connected in series.

[0041] Take powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder and clay, and pass them through a 400-mesh sieve to obtain their respective powders for later use.

[0042] Take 25% powdered activated carbon, 15% quicklime powder, 2% magnesium sulfate, 0.5% iron oxide powder, and 50% clay by mass percentage; after mixing evenly, add 5% 40% sodium silicate solution, and make up the remainder with water. After mixing evenly, use a disc granulator to form small balls with a particle size of 6-8 mm; air-dry the prepared small balls in a cool place for 1 week, and then place them outdoors to air-dry for 2 weeks to obtain the packing material of this embodiment; soak the packing material of this embodiment in the effluent tank of the secondary sedimentation tank for 1 week to form a biofilm, and then fill it into the denitrification unit.

[0043] Water was introduced into the reactor at a flow rate of 630 mL / min, with a vacuum degree of 1.5–2 kPa. No air bubbles accumulated in the packing layer during operation. The operating data over a period of time is shown in the table below:

[0044] Table 1. Operating data of a single denitrification reactor in this experiment.

[0045]

[0046] It can be seen that the denitrification reactor and packing material used in this embodiment have a significant denitrification effect at low carbon-nitrogen ratios, and can denitrify wastewater with even lower carbon-nitrogen ratios, with little change in nitrite nitrogen. As the carbon-nitrogen ratio increases, the denitrification efficiency tends to increase, and at a carbon-nitrogen ratio of around 4.5, the nitrate nitrogen removal rate can reach more than 85%, with the actual carbon-nitrogen ratio consumed being only between 3 and 4. This has positive significance for the study of denitrification under low carbon-nitrogen ratios.

[0047] Comparative Example 1

[0048] In this comparative example, the denitrification unit of Example 1 was used, and the operating conditions were the same as in Example 1. Different packing materials were added to explore and compare the advantages of the packing material of the present invention. In the process, commercially available volcanic rock packing material and bio-ceramic granule packing material were compared with the packing material prepared in Example 1 of the present invention. The particle size of each packing material was 6-8 mm. The results are shown in the table below.

[0049] Table 2 Comparison of Operating Data for Different Packing Materials

[0050]

[0051] It can be seen that the packing material used in Example 1 of the present invention can effectively promote the utilization of COD by denitrifying bacteria in the packing material, promote the denitrification process, improve the denitrification efficiency, and has broad application prospects.

[0052] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A denitrification reactor, characterized in that: It includes multiple closed denitrification units connected in series, each of which is filled with denitrification packing material; The denitrification packing material, by mass percentage, comprises 20-30% powdered activated carbon, 10-20% quicklime powder, 2% magnesium sulfate, 5% sodium silicate solution, 0.5% iron oxide powder, 50% clay, and the balance being water.

2. The denitrification reactor according to claim 1, characterized in that: The denitrification unit has an inlet below the denitrification packing and an outlet above the denitrification packing. The outlet of the previous denitrification unit is connected to the inlet of the next denitrification unit through a connecting pipe.

3. The denitrification reactor according to claim 2, characterized in that: It also includes a main water inlet pipe, which is connected to multiple branch water inlet pipes. Each branch water inlet pipe is connected to the inlet of the corresponding denitrification unit. Each branch water inlet pipe is equipped with a control valve, and control valves are also installed on the connecting pipes on both sides of the connection between each branch water inlet pipe and the corresponding connecting pipe.

4. The denitrification reactor according to claim 2, characterized in that: Each of the denitrification units has a sedimentation zone at its bottom, and each sedimentation zone is connected to a corresponding sewage branch pipe, which is connected to the main sewage pipe; each sewage branch pipe is equipped with a control valve.

5. The denitrification reactor according to claim 4, characterized in that: Each of the denitrification units is equipped with a top cover, and each top cover is connected to a corresponding extraction branch pipe. The extraction branch pipe is connected to the main extraction pipe, and a control valve is installed on each extraction branch pipe.

6. The denitrification reactor according to claim 5, characterized in that: A drain pipe is installed between the main exhaust pipe and the main sewage pipe, and a control valve is installed on the drain pipe.

7. The denitrification reactor according to claim 1, characterized in that: In the aforementioned denitrification filler raw materials, powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder, and clay all pass through a 200-400 mesh sieve; the mass fraction of sodium silicate solution is 30-50%.

8. The denitrification reactor according to claim 7, characterized in that, The preparation of the denitrification packing includes the following steps: S1. Mix powdered activated carbon, quicklime powder, magnesium sulfate, iron oxide powder and clay evenly, add sodium silicate solution and water, mix evenly and then granulate to obtain filler particles. S2. First, air dry the S1 packing particles in a cool, dry place, and then air dry them in an outdoor dry place to obtain the denitrification packing of the present invention.

9. The denitrification reactor according to claim 8, characterized in that: The filler particles have a particle size of 6-8 mm. The filler particles are first air-dried in a cool, dry place for 1 week, and then air-dried in an outdoor dry place for 2 weeks.

10. The denitrification reactor according to claim 8, characterized in that: The denitrification packing material is soaked in the effluent tank of the secondary sedimentation tank, and after biofilm formation, it is filled into the denitrification unit. The denitrification unit has a diameter of 250 mm and a height of 1300 mm. The filling height of the denitrification packing material is 1000 mm, and the porosity is 30-35%. The flow rate in the denitrification unit is 600-650 mL / min, and the vacuum degree is 1.5-2 kPa.

Images