Low-carbon-nitrogen-ratio sewage and wastewater synchronous nitrification and denitrification-polyculture denitrification nitrogen removal method and reactor

Abstract

The invention relates to a low-carbon-nitrogen-ratio sewage and wastewater synchronous nitrification and denitrification-polyculture denitrification nitrogen removal method and a reactor, and the method comprises the following steps: (1) enabling low-carbon-nitrogen-ratio sewage and wastewater to enter a primary synchronous nitrification and denitrification reactor loaded with elemental sulfur filler, and carrying out a synchronous nitrification and denitrification process; the treated effluent enters a secondary polyculture denitrification reactor loaded with elemental sulfur filler, and a polyculture denitrification process is carried out; and (2) enabling the treated water to enter a sedimentation tank, carrying out solid-liquid separation, then discharging, enabling part of precipitated sludge to flow back to the primary synchronous nitrification and denitrification reactor, and enabling part of precipitated sludge to be discharged as residual sludge. The method and the reactor provided by the invention have the advantages of small demand on exogenous organic carbon and pH buffer substances, no need of nitrification liquid backflow, low sludge yield and low denitrification operation cost, and are suitable for treatment of low-carbon-nitrogen-ratio sewage and wastewater and upgrading and reconstruction of sewage treatment plants.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage and wastewater denitrification, and particularly relates to a method and a reactor for denitrification of sewage and wastewater with a low carbon-nitrogen ratio by simultaneous nitrification and denitrification-mixed culture denitrification. Background Art

[0002] The use of traditional nitrification-denitrification processes to treat low carbon-nitrogen ratio (C / N) wastewater (such as municipal sewage, landfill leachate, aquaculture wastewater and coking wastewater, etc.) has the typical problems of insufficient denitrification organic carbon source and low denitrification efficiency. Therefore, in actual projects, exogenous organic carbon (such as methanol, ethanol and acetate, etc.) needs to be added to improve the treatment efficiency, and the operating cost and carbon emissions of wastewater treatment also increase accordingly.

[0003] In recent years, the research and application of simultaneous nitrification and denitrification and autotrophic denitrification have been carried out to solve the problem of large carbon source demand for biological denitrification and denitrification of low C / N wastewater. Simultaneous nitrification and denitrification can achieve ammonia nitrogen (NH4 + -N) to nitrate nitrogen (NO2 - -N、NO3 - -N) and nitrogen (N2), which has the advantages of low sludge production, no need for nitrification liquid reflux and small footprint of reaction facilities. However, its startup and operation process requires strict control of C / N and aeration conditions, and the denitrification process is highly dependent on exogenous organic carbon.

[0004] Elemental sulfur (S 0 ) is cheap and easy to obtain. 0 As an inorganic electron donor, sulfur autotrophic denitrification has the characteristics of low sludge production and low carbon emissions. It has been widely used in biological denitrification processes in many fields such as municipal tailwater, surface water, groundwater, drinking water and agricultural runoff. However, due to the slow growth rate of autotrophic denitrification microorganisms, the process startup time is relatively long. At the same time, S 0 The low solubility of S limits the bioavailability of autotrophic denitrifying microorganisms, so in practical applications, S 0 The carrier packed bed or fluidized bed is used to increase the dosage, which significantly increases the construction cost of the reaction system. In addition, the sulfur autotrophic denitrification process consumes a lot of alkalinity, and limestone needs to be added to adjust the pH value, which increases the operating cost and increases the sulfate content in the effluent. The simultaneous nitrification and denitrification technology is coupled with the sulfur autotrophic denitrification technology. On the one hand, the organic matter in the low C / N wastewater can increase the S 0 The bioavailability of NH4+ can provide more electron donors for the simultaneous nitrification and denitrification process and the sulfur autotrophic denitrification process, and effectively reduce the demand for exogenous organic carbon in the denitrification process. -It can replenish the alkalinity consumed in the sulfur autotrophic denitrification process, so there is no need to add external pH buffer substances. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method and reactor for simultaneous nitrification and denitrification of low carbon-nitrogen ratio sewage and wastewater and polyculture denitrification denitrification, so as to reduce the demand for exogenous organic carbon in the denitrification process and reduce the operating cost under the premise of ensuring the denitrification efficiency.

[0006] The present invention provides a method for simultaneous nitrification and denitrification-mixed denitrification of sewage and wastewater with a low carbon-nitrogen ratio (C / N), comprising the following steps:

[0007] (1) The low carbon nitrogen ratio wastewater enters a chamber loaded with elemental sulfur (S 0 ) filler in a first-stage simultaneous nitrification and denitrification reactor, 0 The synergistic induction of organic carbon sources in low C / N wastewater initiates the simultaneous nitrification and denitrification process, converting NH4 + -N is converted to NO3 - -N, it is further reduced to N2 by denitrifying microorganisms, thereby removing part of the total nitrogen and organic matter; then the treated water enters the secondary polyculture denitrification reactor loaded with elemental sulfur filler to carry out the polyculture denitrification process, further reducing the total nitrogen concentration in the wastewater, and achieving the simultaneous and efficient removal of nitrogen and organic matter in the wastewater with a low carbon-nitrogen ratio;

[0008] (2) The treated water enters the sedimentation tank and is discharged after solid-liquid separation. Part of the precipitated sludge is returned to the primary simultaneous nitrification and denitrification reactor, and part is discharged as residual sludge.

[0009] Preferably, the elemental sulfur in step (1) is elemental sulfur powder sieved through a 40-mesh sieve, wrapped with corrosion-resistant non-woven fabric and loaded into each level of reactor, and the weight of a single pack of fillers is 2 to 4 kg.

[0010] Preferably, the packing density of the elemental sulfur filler in the primary synchronous nitrification and denitrification reactor is 15-30 kg / m 3 .

[0011] Preferably, the packing density of the elemental sulfur filler in the secondary polyculture denitrification reactor is 30-60 kg / m 3 .

[0012] Preferably, the reaction residence time of the primary simultaneous nitrification and denitrification reactor in step (1) is 8 to 12 hours, and the dissolved oxygen concentration is 2 to 4 mg / L.

[0013] Preferably, the reaction residence time of the secondary polyculture denitrification reactor in step (1) is 6 to 12 hours, and the dissolved oxygen concentration is 0.1 to 0.5 mg / L.

[0014] Preferably, the C / N ratio of the sewage and wastewater in step (1) is 1 to 3.

[0015] More preferably, when the C / N ratio of the sewage inlet is lower than 1, a small amount of exogenous organic carbon can be added to the sewage inlet through the carbon source addition pipe to enhance the denitrification effect.

[0016] Preferably, in step (2), the sludge return ratio is 50% to 100%.

[0017] The present invention also provides a low carbon-nitrogen ratio sewage and wastewater synchronous nitrification and denitrification-mixed culture denitrification reactor, comprising a primary synchronous nitrification and denitrification reactor provided with a first elemental sulfur filler, a secondary mixed culture denitrification reactor provided with a second elemental sulfur filler, and a sedimentation tank; the water inlet side of the primary synchronous nitrification and denitrification reactor is a water inlet pipe connected to a carbon source addition pipe, the water outlet side is provided with a first water outlet pipe, and an aeration pipe is provided at the bottom; the water inlet side of the secondary mixed culture denitrification reactor is connected to the first water outlet pipe, the water outlet side is provided with a second water outlet pipe, and a sludge mixer is provided at the bottom; the water inlet side of the sedimentation tank is connected to the second water outlet pipe, the water outlet side is provided with a third water outlet pipe, a sludge discharge pipe and a sludge return pipe are provided at the bottom, and the sludge return pipe is connected to the water inlet pipe.

[0018] Preferably, the water inlet side of the primary synchronous nitrification and denitrification reactor is provided with a first water distribution channel, and the water outlet side is provided with a first water collection channel; the water inlet side of the secondary polyculture and denitrification reactor is provided with a second water distribution channel, and the water outlet side is provided with a second water collection channel.

[0019] The principle of the present invention is: 0 The organic carbon source in the low C / N wastewater influent is used as an electron donor to achieve simultaneous nitrification and denitrification and mixed denitrification in aerobic and anoxic reactors. 0 The synergistic induction of organic carbon sources in low C / N wastewater can promote the enrichment of denitrification dominant functional bacteria and start the simultaneous nitrification and denitrification process, thereby improving the denitrification efficiency of the influent and reducing the demand for exogenous organic carbon. 0 The synergistic effect of the residual organic carbon source in the effluent of the primary simultaneous nitrification and denitrification reactor can enhance the S 0 The bioavailability of the product can provide sufficient inorganic electron donors for the denitrification dominant bacteria, thereby achieving the simultaneous and efficient removal of nitrogen and organic matter and reducing operating costs.

[0020] Beneficial Effects

[0021] The invention is applicable to low C / N urban sewage or industrial wastewater, in which nitrogen is in the form of NH4 +-N. Compared with the traditional nitrification and denitrification process, the low C / N wastewater synchronous nitrification and denitrification-mixed culture and denitrification method and reactor proposed in the present invention can start the synchronous nitrification and denitrification process under low C / N conditions, with small demand for exogenous organic carbon and pH buffer substances, no need for nitrification liquid reflux, low sludge yield, and low denitrification operation cost, which is suitable for the treatment of low C / N wastewater and the upgrading and transformation of sewage treatment plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the synchronous nitrification and denitrification-mixed denitrification reactor for low carbon-nitrogen ratio wastewater of the present invention.

[0023] Figure numerals: 1-water inlet pipe; 2-carbon source addition pipe; 3-first water distribution channel; 4-first elemental sulfur filler; 5-first-level simultaneous nitrification and denitrification reactor; 6-first water collection channel; 7-aeration pipe; 8-first water outlet pipe; 9-second water distribution channel; 10-second elemental sulfur filler; 11-secondary polyculture and denitrification reactor; 12-second water collection channel; 13-submersible mixer; 14-second water outlet pipe; 15-sedimentation tank; 16-third water outlet pipe; 17-sludge discharge pipe; 18-sludge return pipe. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0025] Example

[0026] This embodiment provides a method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater-polyculture denitrification. The low carbon-nitrogen ratio wastewater in this embodiment is domestic sewage, and the main water quality indicators are: COD = 139.0 ± 4.0 mg / L, NH4 + -N=48.8±1.7mg / L,TN=64.1±1.7mg / L,the nitrogen in low C / N wastewater is mainly NH4 + -N form. In order to solve the problem of denitrification of low C / N wastewater, a method of simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater-mixed denitrification is adopted, which includes the following steps:

[0027] (1) The low carbon nitrogen ratio wastewater enters the S 0 In the first-stage simultaneous nitrification and denitrification reactor with S 0The synergistic induction of organic carbon sources in low C / N wastewater initiates the simultaneous nitrification and denitrification process. The reaction residence time is 8 to 12 hours, and the dissolved oxygen concentration is controlled at 2.0 to 4.0 mg / L. + -N is converted to NO3 - -N, and then it is further reduced to N2 by denitrifying microorganisms, thereby removing part of the total nitrogen and organic matter; the treated water enters the S 0 The secondary polyculture denitrification reactor with S 0 The residual organic carbon source in the influent is used as an electron donor to induce the mixed culture denitrification process. The reaction residence time is 6 to 12 hours, and the dissolved oxygen concentration is controlled at 0.1 to 0.5 mg / L, which further reduces the total nitrogen concentration in the wastewater and realizes the simultaneous and efficient removal of nitrogen and organic matter in low C / N wastewater.

[0028] (2) The water treated in step (1) enters a sedimentation tank and is discharged after solid-liquid separation. Part of the precipitated sludge is returned to the primary synchronous nitrification and denitrification reactor, and part is discharged as residual sludge. The sludge return ratio is controlled at 50% to 100%.

[0029] Among them, S in step (1) 0 The elemental sulfur powder is sieved through a 40-mesh sieve and is wrapped with corrosion-resistant non-woven fabric and loaded into each level of the reactor. The weight of a single pack of filler is 2-4 kg. The sulfur in the first-level synchronous nitrification and denitrification reactor is 0 The packing density of the filler is 15~30kg / m 3 In the secondary polyculture denitrification reactor, S 0 The packing density of the filler is 30~60kg / m 3 In step (1), the reaction residence time of the primary synchronous nitrification and denitrification reactor is 8 to 12 hours, and the dissolved oxygen concentration is 2 to 4 mg / L; the reaction residence time of the secondary polyculture and denitrification reactor is 6 to 12 hours, and the dissolved oxygen concentration is 0.1 to 0.5 mg / L.

[0030] The above denitrification method adopts Figure 1The low carbon-nitrogen ratio sewage and wastewater synchronous nitrification and denitrification-mixed culture denitrification reactor shown in the figure comprises a primary synchronous nitrification and denitrification reactor 5 provided with a first elemental sulfur filler 4, a secondary mixed culture denitrification reactor 11 provided with a second elemental sulfur filler 10, and a sedimentation tank 15; the water inlet side of the primary synchronous nitrification and denitrification reactor 5 is a water inlet pipe 1 connected to a carbon source addition pipe 2, the water outlet side is provided with a first water outlet pipe 8, and an aeration pipe 7 is provided at the bottom; the water inlet side of the secondary mixed culture denitrification reactor 11 is connected to the first water outlet pipe 8, and the outlet A second outlet pipe 14 is provided on the water side, and a sludge mixer 13 is provided at the bottom; the water inlet side of the sedimentation tank 15 is connected to the second outlet pipe 14, the water outlet side is provided with a third outlet pipe 16, a sludge discharge pipe 17 and a sludge return pipe 18 are provided at the bottom, and the sludge return pipe 18 is connected to the water inlet pipe 1; the water inlet side of the primary synchronous nitrification and denitrification reactor 5 is provided with a first water distribution channel 3, and the water outlet side is provided with a first water collection channel 6; the water inlet side of the secondary polyculture denitrification 11 is provided with a second water distribution channel 9, and the water outlet side is provided with a second water collection channel 12.

[0031] The TN and COD in the effluent treated by the above denitrification method can stably reach the A standard (TN≤15.0mg / L and COD≤10.0mg / L) of the first level standard of the "Emission Standard of Pollutants from Urban Wastewater Treatment Plants" (GB18918-2002).

Claims

1. A method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater-mixed denitrification, comprising the following steps: (1) low carbon-nitrogen ratio wastewater is fed into a primary simultaneous nitrification and denitrification reactor loaded with elemental sulfur filler to carry out a simultaneous nitrification and denitrification process to remove part of the total nitrogen and organic matter; The treated water then enters a secondary polyculture denitrification reactor loaded with elemental sulfur filler to undergo a polyculture denitrification process to further reduce the total nitrogen concentration in the wastewater. (2) The treated water enters the sedimentation tank and is discharged after solid-liquid separation. Part of the precipitated sludge is returned to the primary simultaneous nitrification and denitrification reactor, and part is discharged as residual sludge.

2. The denitrification method according to claim 1, characterized in that: In the step (1), the elemental sulfur is elemental sulfur powder sieved through a 40-mesh sieve, wrapped with corrosion-resistant non-woven fabric and loaded into each level of reactor.

3. The denitrification method according to claim 2, characterized in that: The packing density of the elemental sulfur filler in the first-stage synchronous nitrification and denitrification reactor is 15-30 kg / m 3 .

4. The denitrification method according to claim 2, characterized in that: The packing density of the elemental sulfur filler in the secondary polyculture denitrification reactor is 30-60 kg / m 3 .

5. The denitrification method according to claim 1, characterized in that: The reaction residence time of the primary synchronous nitrification and denitrification reactor in step (1) is 8 to 12 hours, and the dissolved oxygen concentration is 2 to 4 mg / L.

6. The denitrification method according to claim 1, characterized in that: The reaction residence time of the secondary polyculture denitrification reactor in step (1) is 6 to 12 hours, and the dissolved oxygen concentration is 0.1 to 0.5 mg / L.

7. The denitrification method according to claim 1, characterized in that: In the step (1), the carbon-nitrogen ratio of the sewage inlet water is 1 to 3.

8. The denitrification method according to claim 1, characterized in that: In the step (2), the sludge return ratio is 50% to 100%.

9. A low carbon-nitrogen ratio wastewater synchronous nitrification and denitrification-mixed culture denitrification reactor, characterized in that: The denitrification reactor comprises a primary synchronous nitrification and denitrification reactor (5) provided with a first elemental sulfur filler (4), a secondary polyculture and denitrification reactor (11) provided with a second elemental sulfur filler (10), and a sedimentation tank (15); the water inlet side of the primary synchronous nitrification and denitrification reactor (5) is a water inlet pipe (1) connected to a carbon source dosing pipe (2), the water outlet side is provided with a first water outlet pipe (8), and the bottom is provided with an aeration pipe (7); the water inlet side of the secondary polyculture and denitrification reactor (11) is connected to the first water outlet pipe (8), the water outlet side is provided with a second water outlet pipe (14), and the bottom is provided with a sludge mixer (13); the water inlet side of the sedimentation tank (15) is connected to the second water outlet pipe (14), the water outlet side is provided with a third water outlet pipe (16), the bottom is provided with a sludge discharge pipe (17) and a sludge return pipe (18), and the sludge return pipe (18) is connected to the water inlet pipe (1).

10. The denitrification reactor according to claim 9, characterized in that: The first-level synchronous nitrification and denitrification reactor (5) is provided with a first water distribution channel (3) on the water inlet side and a first water collection channel (6) on the water outlet side; the second-level polyculture and denitrification reactor (11) is provided with a second water distribution channel (9) on the water inlet side and a second water collection channel (12) on the water outlet side.

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