Secondary biochemical effluent ferrous iron synergistic mixed denitrification advanced nitrogen removal method

Abstract

The present application relates to a kind of secondary biochemical effluent ferrous iron synergistic mixed culture denitrification method, to the secondary biochemical effluent of urban sewage or industrial wastewater treatment plant, then enter the baffling denitrification reaction tank of iron shavings-pyrite composite filling and activated sludge floc, occur heterotrophic denitrification process, autotrophic denitrification process under the action of denitrifying bacteria;After treatment, effluent enters the center pipe of vertical flow sedimentation tank, is discharged after precipitation, and part of sludge is discharged as excess sludge.The present application utilizes the heterotrophic denitrification, Fe 0 And Fe 2+ Autotrophic denitrification and sulfur autotrophic denitrification maintain water acid-base balance, improve denitrifying bacteria abundance, promote sulfur, iron autotrophic denitrification bacteria and heterotrophic denitrification bacteria synergistic denitrification effect, so as to improve denitrification efficiency.The method of the present application is easy to operate and manage, and has low operating cost, which can effectively reduce sludge production.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for deep denitrification of sulfur and iron synergistic co-culture in secondary biological effluent. Background Technology

[0002] The anoxic-aerobic (AO) combined process is a commonly used method for biological nitrogen removal from wastewater. However, the aerobic nitrification effluent contains a certain amount of nitrate, resulting in a certain concentration of NO3 in the secondary biological treatment effluent. - Although the Class A standard of the "Discharge Standard of Pollutants for Urban Wastewater Treatment Plants" sets the TN concentration limit at 15 mg / L, the "Environmental Quality Standard for Surface Water" (Class V) sets the TN limit at only 2 mg / L. Therefore, the discharge of secondary biological effluent from wastewater treatment plants into surface water bodies still poses a risk of eutrophication. To improve surface water quality and eliminate the risk of eutrophication, deep denitrification of the secondary biological effluent is necessary to further reduce nitrogen entering the aquatic environment.

[0003] After biological treatment at the wastewater treatment plant, the secondary biological effluent has a low concentration of bioavailable carbon sources, classifying it as oligotrophic water. Traditional heterotrophic denitrification methods relying on the addition of organic carbon sources are costly to operate; excessive carbon source addition can increase the organic matter content in the final effluent, and heterotrophic denitrification produces a large amount of sludge. Compared to heterotrophic denitrification, autotrophic denitrification mediated by sulfur- and iron-autotrophic bacteria can utilize low-valence sulfur (S₂O₃). 0 S 2- S2O3 2- (etc.) and low-valence iron (Fe) 0 Fe 2+ Inorganic substances such as NO3- can act as electron donors to convert NO3- into electrons. - -N is reduced to N2, which eliminates the need for an external organic carbon source when used for denitrification of low C / N wastewater. It also has the advantages of low operating cost, high denitrification efficiency and low sludge production, and has become the mainstream research direction for efficient denitrification of low C / N wastewater.

[0004] Single-sulfur autotrophic denitrification has high nitrogen removal efficiency, based on S2O3. 2- Autotrophic denitrification not only enables the liquid addition of sulfur electron donors, but also avoids the inconvenience of using solid SO (hazardous materials) and S 2- The drawback is the easy generation of H2S, but the acid production during the reaction process easily leads to an acidic pH in the effluent. Based on Fe 0 / Fe 2+ Iron-autotrophic denitrification can also achieve high nitrogen removal efficiency, but it produces alkali during the treatment process and easily forms ferric iron compounds that adhere to and coat the sludge and Fe. 0 The surface reduces reaction efficiency.

[0005] Therefore, the skilled in the art comprehensively combines the characteristics of sulfur and iron autotrophic denitrification in research and development, so that the sulfur and iron combined autotrophic denitrification can avoid the shortcomings of single use, and realize the acid-base neutralization and mutual promotion in the reaction process. SUMMARY

[0006] The task of the present application is to provide a secondary biochemical effluent sulfur-iron synergistic mixed culture denitrification deep denitrification method, based on the principle of sulfur-iron synergistic autotrophic and mixed culture denitrification, a combined S2O3 2- , Fe 0 and pyrite (FeS2) secondary biochemical effluent mixed culture deep denitrification method for sewage treatment plant is proposed, a proper amount of organic carbon source and sulfur source is continuously added to the secondary biochemical effluent, mixed culture denitrification is carried out to maintain the acid-base balance in water, and the abundance of denitrifying bacteria is improved, so that the carbon source consumption and sludge yield in the denitrification process can be effectively reduced. 2- The single sulfur autotrophic denitrification based on S2O3 0 produces acid in the reaction process, which easily leads to acidic effluent pH, and the iron autotrophic denitrification based on Fe 2+ / Fe 0 produces base in the treatment process, which easily forms trivalent iron compounds and is attached and wrapped on the sludge and Fe

[0007] The technical solution of the present application is as follows:

[0008] A secondary biochemical effluent sulfur-iron synergistic mixed culture denitrification deep denitrification method, comprising the following steps:

[0009] Step 1: A proper amount of organic carbon source and sulfur source is continuously added to the secondary biochemical effluent of municipal sewage or industrial wastewater treatment plant, and then enters a baffled denitrification reaction tank filled with iron shaving-pyrite composite filler and activated sludge flocs, and under the action of denitrifying bacteria, heterotrophic denitrification process (CH3COO - +1.18NO3 - +2.18H + →0.12C5H7O2N+1.4CO2+2.5H2O+0.53N2), autotrophic denitrification process (S2O3 2- autotrophic denitrification: S2O3 2- +1.24NO3 - +0.45HCO3 - +0.09NH4 + +0.11H2O→0.09C5H7O2N+0.4H + +0.62N2+2SO4 2- ; Fe 0 autotrophic denitrification: Fe 0 +0.4NO3- +1.2H2O→Fe 2+ +0.2N2+2.4OH - ;Fe 2+ Autotrophic denitrification: Fe 2+ +0.2NO3 - +2.4H2O→Fe(OH)3+0.1N2+1.8H + );

[0010] Step 2: The effluent after step 1 treatment enters the central pipe of the vertical flow sedimentation tank, and is discharged after sedimentation, and part of the sedimentation sludge is discharged as residual sludge.

[0011] In the step 1, the m (Fe 0 ): m (FeS2) = 4~5:1 in the iron shavings-pyrite composite filler, and the packing density is 30~40 kg / m 3 .

[0012] The iron shavings and pyrite are wrapped by polyethylene mesh bags, and each bag weighs 5~8 kg; wherein the iron shavings provide Fe 0 iron source and electron donor, and the pyrite provides part of the iron source and sulfur source electron donor.

[0013] In the step 1, sodium acetate or methanol is used as an additional organic carbon source, the influent COD / TN is controlled to be 1.9~2.1, and sodium thiosulfate is used as an additional sulfur source, and the influent S / N molar ratio is controlled to be 1.4~1.6.

[0014] In the step 1, the dissolved oxygen in the denitrification reaction tank is controlled to be below 0.5 mg / L, and the hydraulic retention time is controlled to be 8.0~12.0 h.

[0015] According to the method for deep denitrification of secondary biochemical effluent by sulfur-iron synergistic mixed culture denitrification, a proper amount of organic carbon source and sulfur source are continuously added to the secondary biochemical effluent of municipal sewage or industrial wastewater treatment plant, and in the sulfur-iron synergistic mixed culture denitrification enhanced secondary biochemical effluent deep denitrification reactor, the heterotrophic denitrification, Fe 0 and Fe 2+ autotrophic denitrification and sulfur autotrophic denitrification in the system maintain the acid-base balance in water, improve the abundance of denitrifying bacteria, promote the synergistic denitrification of sulfur and iron autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria, and thus improve the denitrification efficiency.

[0016] Compared with the traditional denitrification deep bed denitrification filter, the sulfur-iron synergistic mixed culture denitrification enhanced secondary biochemical effluent deep denitrification reactor manufactured according to the method does not have the problems of filter bed blockage and backwashing, is easy to operate and manage, and has a lower operation cost, and can effectively reduce the sludge yield while improving the mixed culture denitrification denitrification efficiency.

[0017] The application provides a secondary biochemical effluent sulfur-iron synergistic mixed culture denitrification deep denitrification method. - The application also provides a sulfur-iron synergistic mixed culture denitrification enhanced secondary biochemical effluent deep denitrification reactor manufactured by the method. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a structural schematic diagram of a sulfur-iron synergistic mixed culture denitrification enhanced secondary biochemical effluent deep denitrification reactor manufactured by the method.

[0019] Figure 2 Figure 1 FIG. 2 is a structural schematic diagram of an iron shavings-pyrite composite filler frame in the denitrification reactor.

[0020] REFERENCE SIGNS

[0021] 1 is a water inlet pipe, 2 is a water distribution channel, 3 is a stainless steel filler frame, 4 is a baffling denitrification reaction tank, 5 is an activated sludge floc, 6 is a reaction tank water collection channel, 7 is a water outlet pipe, 8 is a vertical flow sedimentation tank, 9 is a sedimentation tank water collection channel, 10 is a wastewater outlet pipe, 11 is a central pipe, 12 is a sludge discharge pipe, 13 is a hydraulic agitator, 14 is a carbon source adding pipe, 15 is a sulfur source adding pipe, 16 is a stainless steel partition plate of the filler frame, and 17 is an iron shavings-pyrite composite filler. DETAILED DESCRIPTION

[0022] In order to make the application more apparent and easy to understand, the preferred embodiments are described in detail below with reference to the accompanying drawings.

[0023] The application provides a secondary biochemical effluent sulfur-iron synergistic mixed culture denitrification deep denitrification method, which adopts the following steps.

[0024] A proper amount of organic carbon source and sulfur source are continuously added into secondary biochemical effluent of a municipal sewage or industrial wastewater treatment plant, and then enter a baffling denitrification reaction tank provided with iron shavings-pyrite composite fillers and activated sludge flocs, and under the action of denitrifying bacteria, heterotrophic denitrification process (CH3COO - +1.18NO3 - +2.18H + →0.12C5H7O2N+1.4CO2+2.5H2O+0.53N2), autotrophic denitrification process (S2O3 2- Autotrophic denitrification: S2O3 2- +1.24NO3 - +0.45HCO3 - ​+0.09 NH4 + +0.11 H2O→0.09 C5H7O2N+0.4 H + +0.62 N2+2 SO4 2- ; Fe 0 Autotrophic denitrification: Fe 0 +0.4 NO3 - +1.2 H2O→Fe 2+ +0.2 N2+2.4 OH - ; Fe 2+ Autotrophic denitrification: Fe 2+ +0.2 NO3 - +2.4 H2O→Fe(OH)3+0.1 N2+1.8 H + ).

[0025] The treated effluent enters the central pipe of the vertical flow sedimentation tank, is discharged after sedimentation, and part of the sedimentation sludge is discharged as residual sludge.

[0026] The m (Fe 0 ): m (FeS2) of the iron shavings-pyrite composite filler installed in the baffling type denitrification reaction tank is 4~5:1, and the packing density is 30~40kg / m 3 . The iron shavings and pyrite are wrapped by polyethylene mesh bags, and each bag weighs 5~8kg; the iron shavings provide Fe 0 iron source and electron donor, and the pyrite provides part of iron source and sulfur source electron donor.

[0027] Sodium acetate or methanol is used as an additional organic carbon source, and the influent COD / TN is controlled to be 1.9~2.1. Sodium thiosulfate is used as an additional sulfur source, and the influent S / N molar ratio is controlled to be 1.4~1.6.

[0028] The dissolved oxygen of the baffling type denitrification reaction tank is controlled to be below 0.5mg / L, and the hydraulic retention time is controlled to be 8.0~12.0h.

[0029] In a preferred embodiment of the method for deep denitrification of secondary biochemical effluent by sulfur-iron synergistic mixed culture denitrification, the raw wastewater is taken from the secondary biochemical effluent of a simulated A / O process, and the concentrations of total nitrogen (TN), nitrate nitrogen (NO3 - -N), nitrite nitrogen (NO2 - -N), and ammonia nitrogen (NH4 + -N) are 21.3~34.3mg / L, 17.5~31.9mg / L, 0.00~2.67mg / L, and 0~10.2mg / L, respectively, and the nitrogen form in the wastewater is mainly NO3 - -N.

[0030] Secondary biochemical effluent enters the baffled denitrification reactor tank with iron shavings-pyrite composite filler and activated sludge floc, and with sodium acetate or methanol as external organic carbon source to control the influent COD / TN ratio of 1.9-2.1, with sodium thiosulfate as external sulfur source to control the influent S / N molar ratio of 1.4-1.6, under the action of denitrifying bacteria, heterotrophic denitrification, Fe 0 and Fe 2+ autotrophic denitrification and sulfur autotrophic denitrification processes occur simultaneously, achieving efficient denitrification of NO3 - -N into N2; after the reaction is completed, the sludge-water mixture enters the center pipe of the vertical flow sedimentation tank, and after sedimentation, the wastewater is discharged, and part of the sludge is discharged as excess sludge. After treatment, the COD of the wastewater is less than 50.0 mg / L, and the TN is less than 5.0 mg / L.

[0031] Referring to Figure 1 and Figure 2 , the specific structure of the sulfur-iron synergistic co-culture denitrification enhanced secondary biochemical effluent advanced denitrification reactor manufactured according to the method of the present application is as follows:

[0032] The denitrification reactor is provided with a baffled denitrification reactor tank 4, a plurality of groups of stainless steel filler frames 3 are installed in the baffled denitrification reactor tank 4, each group of filler frames 3 is installed with a plurality of horizontally arranged stainless steel partitions 16, and each stainless steel partition 16 is stacked with iron shavings-pyrite composite filler 17 and activated sludge floc 5 wrapped by a polyethylene mesh bag.

[0033] The baffled denitrification reactor tank 4 is externally connected with an influent pipe 1 and an effluent pipe 7, and the influent pipe 1 and the effluent pipe 7 are arranged on both sides of the reactor tank. The influent pipe 1 is respectively connected with a carbon source adding pipe 14 and a sulfur source adding pipe 15. The effluent pipe 7 is connected with a vertical flow sedimentation tank 8. The influent pipe 1 of the baffled denitrification reactor tank 4 is provided with a water distribution channel 2 on one side. The effluent pipe 7 of the baffled denitrification reactor tank 4 is provided with a reactor tank water collection channel 6 on one side. A hydraulic stirrer 13 is installed at the bottom of the baffled denitrification reactor tank 4.

[0034] A vertical center pipe 11 is arranged in the middle of the vertical flow sedimentation tank 8, and the center pipe 11 is connected with the effluent pipe 7 of the reactor tank. The bottom of the vertical flow sedimentation tank 8 is conical in shape and is provided with a sludge discharge pipe 12, which is beneficial to the discharge of sludge from the sludge discharge pipe 12. A wastewater effluent pipe 10 is arranged on the outside of the vertical flow sedimentation tank 8, and a sedimentation tank water collection channel 9 is arranged on one side of the wastewater effluent pipe 10.

[0035] In summary, the secondary biochemical effluent sulfur iron synergistic mixotrophic denitrification advanced nitrogen removal method and the nitrogen removal reactor of the application, a proper amount of organic carbon source and sulfur source are continuously added into the secondary biochemical effluent of the urban sewage or industrial wastewater treatment plant, and then enter the baffled denitrification reaction tank filled with iron shavings-malachite composite filler and activated sludge floc, under the action of denitrifying bacteria, heterotrophic denitrification, S2O3 2- autotrophic denitrification, Fe 0 -Fe 2+ autotrophic denitrification denitrification process, each process is carried out synchronously, and the water is continuously fed and discharged; the effluent after treatment enters the central pipe of the vertical flow sedimentation tank, is discharged after sedimentation, and part of the sedimentation sludge is discharged as residual sludge.

[0036] Compared with the traditional denitrification deep bed nitrogen removal filter, the application has low carbon source consumption, no filter bed blockage and backwashing problem, convenient operation and management, low operation cost, and can realize acid-base complementation, improve the efficiency of mixotrophic denitrification denitrification, and effectively reduce the sludge production.

[0037] Of course, those skilled in the art should realize that the above embodiments are only used to illustrate the application, and are not used as a limitation on the application, as long as the changes, modifications, etc. of the above embodiments are within the scope of the application.

Claims

1. A method for deep denitrification of secondary biochemical effluent by sulfur-iron synergistic cultivation and denitrification, characterized in that, The method comprises the following steps: Step 1: A proper amount of organic carbon source and sulfur source is continuously added into the secondary effluent of municipal sewage or industrial wastewater treatment plant, and then enters the baffled denitrification reaction tank filled with iron shavings-malachite composite filler and activated sludge floc, where the heterotrophic denitrification process CH3COO - +1.18NO 3- +2.18H + →0.12C5H7O2N+1.4CO2+2.5H2O+0.53N2, autotrophic denitrification process S2O3 2- autotrophic denitrification: S2O3 2- +1.24NO 3- +0.45HCO 3- +0.09NH 4+ +0.11H2O→0.09C5H7O2N+0.4H + +0.62N2+2SO4 2- ; Fe 0 autotrophic denitrification: Fe 0 +0.4NO 3- +1.2H2O→Fe 2+ +0.2N2+2.4OH - ; Fe 2+ autotrophic denitrification: Fe 2+ +0.2NO 3- +2.4H2O→Fe(OH)3+0.1N2+1.8H + ; The effluent after step 1 treatment enters the central pipe of the vertical flow sedimentation tank, is discharged after sedimentation, and part of the sedimentation sludge is discharged as residual sludge; in the step 1, m (Fe 0 ): m (FeS2) = 4~5:1, the packing density is 30~40kg / m 3 ; in the step 1, sodium acetate or methanol is used as an additional organic carbon source, the influent COD / TN is controlled to be 1.9~2.1, sodium thiosulfate is used as an additional sulfur source, and the influent S / N molar ratio is controlled to be 1.4~1.

6.

2. The secondary biochemical effluent ferrous iron synergistic deep denitrification method according to claim 1, characterized in that: The iron filings and the pyrite are wrapped by polyethylene mesh bags, each bag weighing 5-8 kg; wherein the iron filings provide Fe 0 Iron source and electron donor, pyrite provides part of the iron source and sulfur source electron donor.

3. The secondary biochemical effluent ferrous iron synergistic deep denitrification method according to claim 1, characterized in that: The dissolved oxygen in the denitrification reaction tank in step 1 is controlled below 0.5 mg / L, and the hydraulic retention time is controlled to be 8.0-12.0 h.

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