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

Abstract

The invention relates to a low-carbon-nitrogen-ratio sewage and wastewater synchronous nitrification and denitrification-polyculture denitrification nitrogen and phosphorus removal method and a reactor. According to the method, iron shaving / elemental sulfur composite filler is arranged in each stage of reactor; the method comprises the following steps: S1, enabling sewage and wastewater with a low carbon-nitrogen ratio to enter a primary aerobic reactor, and carrying out a synchronous nitrification and denitrification process; the treated effluent is subjected to a polyculture denitrification process in a second-stage anoxic reactor; and finally, carrying out an aerobic denitrification process in a three-stage aerobic reactor. S2, enabling the water treated in the step S1 to enter a sedimentation tank, carrying out solid-liquid separation, then discharging, enabling part of settled sludge to flow back to the primary aerobic reactor, and enabling part of settled sludge to serve as residual sludge to be discharged. The nitrogen and phosphorus removal method and the reactor have the advantages of small demand on exogenous organic carbon, low sludge yield and low operation cost, and can realize efficient and stable removal of nitrogen, phosphorus and organic matters in the effluent.

Description

Technical Field

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

[0002] A variety of sewage and wastewater, such as municipal sewage, rural biological sewage, landfill leachate, and printing and dyeing wastewater, all have typical characteristics of a low carbon to nitrogen ratio (C / N). For traditional nitrification and denitrification processes (such as the AO process and the A 2 O process), to ensure the denitrification efficiency, a large amount of organic carbon sources (such as methanol, ethanol, and acetate salts, etc.) need to be added, and a high nitrification liquid reflux ratio needs to be set. The operating cost and energy consumption of the treatment process are relatively high. At the same time, due to the competition for external organic carbon between the biological phosphorus removal process and the denitrification process, it is difficult to ensure a high phosphorus removal efficiency. In actual engineering, it is usually necessary to additionally add iron salts to enhance the phosphorus removal effect through chemical phosphorus removal, further increasing the sewage and wastewater treatment cost.

[0003] To reduce the demand for external organic carbon during the treatment of C / N sewage and wastewater, in recent years, a variety of autotrophic and heterotrophic denitrification processes driven by zero-valent iron and elemental sulfur as inorganic electron donors have been developed to reduce the external carbon source of C / N sewage and wastewater. Zero-valent iron has multiple functions such as inducing and starting simultaneous nitrification and denitrification, serving as an electron donor for autotrophic denitrification, and chemical phosphorus removal. However, during long-term operation, iron oxide products are likely to cover the surface of zero-valent iron and microorganisms, affecting the uptake and utilization of iron by microorganisms and reducing their denitrification efficiency. In addition, the sulfur autotrophic denitrification process driven by elemental sulfur as an electron donor has been widely applied in many fields such as surface water, municipal secondary effluent, agricultural runoff, and drinking water, and effective removal of nitrate nitrogen in low C / N sewage and wastewater has been achieved. However, the sulfur oxidation process will consume a large amount of alkalinity, and usually a large amount of buffer substances such as lime need to be added to adjust the pH, resulting in a deterioration of the treated effluent quality of the sulfur autotrophic denitrification process. When zero-valent iron and elemental sulfur are co-dosed, the H 0 produced during the oxidation process of elemental sulfur S + helps to promote the biological utilization of zero-valent iron and alleviate the negative impact of iron oxide products on denitrifying microorganisms. At the same time, the consumption of H + by zero-valent iron can increase its pH, so there is no need to add a large amount of buffer substances externally, which is beneficial to improving the effluent quality. In addition, the electron donors of zero-valent iron Fe 0 and elemental sulfur S 0 are inexpensive. Coupling them to the sewage and wastewater treatment process can reduce the demand for external organic carbon and help reduce the operating cost. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and a reactor for simultaneous nitrification and denitrification - mixotrophic denitrification for nitrogen and phosphorus removal from wastewater with a low carbon - nitrogen ratio, so as to reduce the demand for exogenous organic carbon in the treatment process of low C / N wastewater, lower the operating cost, and achieve efficient and stable removal of nitrogen, phosphorus and organic matter in the wastewater.

[0005] The present invention provides a method for simultaneous nitrification and denitrification - mixotrophic denitrification for nitrogen and phosphorus removal from wastewater with a low carbon - nitrogen ratio, comprising the following steps:

[0006] S1. Feed the wastewater with a low carbon - nitrogen ratio into a first - stage aerobic reactor filled with iron shavings (Fe 0 ) / elemental sulfur (S 0 ) composite packing. Through the simultaneous nitrification and denitrification process induced by the cooperation of Fe 0 and S 0 with the organic carbon source in the wastewater with a low carbon - nitrogen ratio, convert NH4 + - N into NO3 - - N, and then continue to be reduced to N2 by denitrifying microorganisms, thereby removing part of the total nitrogen and organic matter. At the same time, most of the total phosphorus is removed through the chemical phosphorus - removal effect of iron. After the treated effluent enters the second - stage anoxic reactor, through the mixotrophic denitrification process driven by the cooperation of Fe 0 , S 0 in the iron shavings / elemental sulfur composite packing and the remaining organic matter in the influent, further remove the total nitrogen and continue to remove phosphorus. Finally, in the third - stage aerobic reactor, using Fe 0 , S 0 in the iron shavings / elemental sulfur composite packing, the remaining organic matter and the endogenous carbon of microorganisms as electron donors, drive the aerobic denitrification process, deeply remove nitrogen and strengthen phosphorus removal, and achieve efficient and stable removal of nitrogen, phosphorus and organic matter;

[0007] S2. The water treated in step S1 enters a sedimentation tank, is discharged after solid - liquid separation, part of the sedimented sludge is refluxed to the first - stage aerobic reactor, and part is discharged as excess sludge.

[0008] Preferably, the composition weight ratio of the iron shavings / elemental sulfur composite packing in step S1 is iron shavings: elemental sulfur = 4 - 6:1, wrapped in a polyethylene mesh bag and loaded into each reactor, and the single - package weight is 10 - 15 kg.

[0009] Preferably, the packing density of the iron shavings / elemental sulfur composite packing in the first - stage aerobic reactor and the third - stage aerobic reactor is 70 - 80 kg / m 3 .

[0010] Preferably, the packing density of the iron shavings / elemental sulfur composite packing in the second - stage anoxic reactor is 100 - 110 kg / m 3 .

[0011] Preferably, in the step S1, the reaction residence time of the first aerobic reactor and the third aerobic reactor is 12 - 24 h, and the dissolved oxygen concentration is controlled at 2.0 - 4.0 mg / L.

[0012] Preferably, in the step S1, the reaction residence time of the second anoxic reactor is 6 - 12 h, and the dissolved oxygen concentration is controlled at 0.1 - 0.5 mg / L.

[0013] Preferably, in the step S1, when the C / N of the influent sewage and wastewater is 1 - 3, a small amount of sewage and wastewater with a low C / N ratio is directly introduced into the third aerobic reactor to provide a carbon source for the aerobic denitrification process; when the C / N of the influent sewage and wastewater is less than 1, methanol or sodium acetate is used as an external carbon source and added to the influent water of the first aerobic reactor and the third aerobic reactor to enhance the nitrogen removal effect.

[0014] Preferably, in the step S2, the sludge reflux ratio is controlled at 50% - 100%.

[0015] The present invention also provides a reactor for synchronous nitrification - denitrification and mixotrophic denitrification for nitrogen and phosphorus removal from sewage and wastewater with a low C / N ratio, comprising: a first aerobic reactor provided with a first iron filings / elemental sulfur composite filler, a second anoxic reactor provided with a second iron filings / elemental sulfur composite filler, a third aerobic reactor provided with a third iron filings / elemental sulfur composite filler, and a sedimentation tank; the inlet side of the first aerobic reactor is connected to a water inlet pipe provided with a first carbon source dosing pipe, the outlet side is provided with a first outlet pipe, and the bottom is provided with a first aeration pipe; the inlet side of the second anoxic reactor is connected to the first outlet pipe, the outlet side is provided with a second outlet pipe, and the bottom is provided with a sludge stirrer; the inlet side of the third aerobic reactor is connected to the second outlet pipe provided with a second carbon source dosing pipe, the outlet side is provided with a third outlet pipe, and the bottom is provided with a second aeration pipe; the inlet side of the sedimentation tank is connected to the third outlet pipe, the outlet side is provided with a fourth outlet pipe, and the bottom is provided with a sludge discharge pipe and a sludge reflux pipe, and the sludge reflux pipe is connected to the water inlet pipe.

[0016] Preferably, the inlet side of the first aerobic reactor is provided with a first water distribution channel, and the outlet side is provided with a first water collection channel; the inlet side of the second anoxic reactor is provided with a second water distribution channel, and the outlet side is provided with a second water collection channel; the inlet side of the third aerobic reactor is provided with a third water distribution channel, and the outlet side is provided with a third water collection channel.

[0017] The principle of the present invention is: using the inorganic electron donors Fe 0 and S 0 to cooperate with the organic carbon source in the sewage and wastewater with a low C / N ratio to achieve synchronous nitrification - denitrification and aerobic denitrification in the first aerobic reactor and the third aerobic reactor respectively, and mixotrophic denitrification in the second anoxic reactor. Fe 0 and S 0The addition can effectively promote the enrichment of denitrification-specific functional microorganisms, improve the denitrification utilization rate of organic carbon sources in the influent water, and provide more electron donors for autotrophic denitrifying microorganisms to promote denitrification. In addition, the addition of Fe 0 in each reactor can achieve chemical phosphorus removal, thereby enhancing the phosphorus removal effect of the reactor.

[0018] Beneficial effects

[0019] The scope of application of the present invention is low C / N municipal sewage or industrial wastewater, where nitrogen is mainly in the form of NH4 + -N and phosphorus is mainly in the form of PO4 3- -P. Compared with the traditional nitrification-denitrification process, the method and reactor for simultaneous nitrification-denitrification and mixotrophic denitrification for nitrogen and phosphorus removal of low C / N sewage and wastewater proposed by the present invention have a small demand for exogenous organic carbon, do not require nitrification liquid reflux, have a low sludge production rate, low operating costs, and can achieve efficient and stable removal of nitrogen, phosphorus, and organic matter in the effluent water. Therefore, it has great application prospects in the treatment of low C / N sewage and wastewater and the upgrading and transformation of sewage treatment plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of a reactor for simultaneous nitrification-denitrification and mixotrophic denitrification for nitrogen and phosphorus removal of low carbon-nitrogen ratio sewage and wastewater of the present invention.

[0021] Reference numerals: 1 - influent pipe; 2 - first carbon source dosing pipe; 3 - first water distribution channel; 4 - first iron filings / elemental sulfur composite filler; 5 - first aerobic reactor; 6 - first collection channel; 7 - first aeration pipe; 8 - first effluent pipe; 9 - second water distribution channel; 10 - second iron filings / elemental sulfur composite filler; 11 - second anoxic reactor; 12 - second collection channel; 13 - sludge agitator; 14 - second effluent pipe; 15 - second carbon source dosing pipe; 16 - third water distribution channel; 17 - third iron filings / elemental sulfur composite filler; 18 - third aerobic reactor; 19 - third collection channel; 20 - second aeration pipe; 21 - third effluent pipe; 22 - sedimentation tank; 23 - fourth effluent pipe; 24 - sludge discharge pipe; 25 - sludge return pipe. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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 not 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 also fall within the scope defined by the appended claims of this application.

[0023] Embodiment

[0024] This embodiment provides a method and a reactor for simultaneous nitrification and denitrification - mixotrophic denitrification for nitrogen and phosphorus removal from low C / N wastewater. The wastewater inlet in this embodiment is domestic sewage, and the main water quality indicators are: COD = 142 ± 5.0 mg / L, NH4 + -N = 43.6 ± 0.5 mg / L, TN = 45.9 ± 1.4 mg / L, PO4 3- -P = 5.0 ± 0.2 mg / L. The nitrogen in the wastewater mainly exists in the form of NH4 + -N. To solve the problems of nitrogen and phosphorus removal from low C / N sewage and the high demand for exogenous organic carbon, a method for simultaneous nitrification and denitrification - mixotrophic denitrification for nitrogen and phosphorus removal from low C / N wastewater is adopted, including the following steps:

[0025] S1. Feed the low C / N wastewater into the first aerobic reactor equipped with iron shavings (Fe 0 ) / elemental sulfur (S 0 ) composite packing. Through the simultaneous nitrification and denitrification process induced by Fe 0 and S 0 in cooperation with the organic carbon source in the low C / N wastewater, convert NH4 + -N into NO3 - -N, and then continue to be reduced to N2 by denitrifying microorganisms, thereby removing part of the total nitrogen and organic matter. At the same time, most of the total phosphorus is removed through the chemical phosphorus removal effect of iron. After the treated water enters the second anoxic reactor, through the mixotrophic denitrification process driven by Fe 0 , S 0 in the iron shavings / elemental sulfur composite packing and the remaining organic matter in the influent water, further remove the total nitrogen and continue to remove phosphorus. Finally, in the third aerobic reactor, using Fe 0 , S 0 in the iron shavings / elemental sulfur composite packing, the remaining organic matter and the endogenous carbon of microorganisms as electron donors to drive the aerobic denitrification process, deeply remove nitrogen and strengthen phosphorus removal, and achieve efficient and stable removal of nitrogen, phosphorus and organic matter;

[0026] S2. The water treated in step S1 enters the sedimentation tank, is discharged after solid - liquid separation, part of the sedimented sludge is refluxed to the first aerobic reactor, and part is discharged as excess sludge.

[0027] Among them, in step S1, the composition weight ratio of the iron shavings / elemental sulfur composite packing is iron shavings: elemental sulfur = 5:1, which is wrapped in a polyethylene mesh bag and loaded into each reactor. The single - package weight is 10 - 15 kg, and the packing density of the iron shavings / elemental sulfur composite packing in the first aerobic reactor and the third aerobic reactor is 72 kg / m 3 , and the packing density of the iron shavings / elemental sulfur composite packing in the second anoxic reactor is 108 kg / m 3 .

[0028] Among them, in step S1, the reaction residence time of the first aerobic reactor and the third aerobic reactor is 12 - 24 h, and the dissolved oxygen concentration is controlled at 2.0 - 4.0 mg / L. The reaction residence time of the second anoxic reactor is 6 - 12 h, and the dissolved oxygen concentration is controlled at 0.1 - 0.5 mg / L.

[0029] Among them, in step S2, the sludge reflux ratio is controlled at 50% - 100%.

[0030] The above denitrification and phosphorus removal method adopts a Figure 1 synchronous nitrification and denitrification - mixotrophic denitrification denitrification and phosphorus removal reactor for low C / N sewage and wastewater as shown in

[0031] a first aerobic reactor 5 provided with a first iron filings / elemental sulfur composite filler 4, a second anoxic reactor 11 provided with a second iron filings / elemental sulfur composite filler 10, a third aerobic reactor 18 provided with a third iron filings / elemental sulfur composite filler 17, and a sedimentation tank 22; the water inlet side of the first aerobic reactor 5 is connected to a water inlet pipe 1 provided with a first carbon source dosing pipe 2, the water outlet side is provided with a first water outlet pipe 8, and the bottom is provided with a first aeration pipe 7; the water inlet side of the second anoxic 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 stirrer 13; the water inlet side of the third aerobic reactor 18 is connected to the second water outlet pipe 14 provided with a second carbon source dosing pipe 15, the water outlet side is provided with a third water outlet pipe 21, and the bottom is provided with a second aeration pipe 20; the water inlet side of the sedimentation tank 22 is connected to the third water outlet pipe 21, the water outlet side is provided with a fourth water outlet pipe 23, and the bottom is provided with a sludge discharge pipe 24 and a sludge reflux pipe 25, and the sludge reflux pipe 25 is connected to the water inlet pipe 1.

[0032] The water inlet side of the first aerobic 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 second anoxic reactor 11 is provided with a second water distribution channel 9, and the water outlet side is provided with a second water collection channel 12; the water inlet side of the third aerobic reactor 18 is provided with a third water distribution channel 16, and the water outlet side is provided with a third water collection channel 19.

[0033] After being treated by the above denitrification and phosphorus removal method and denitrification and phosphorus removal reactor, TN, TP and COD in the effluent can stably reach the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918 - 2002) (TN ≤ 15.0 mg / L, TP ≤ 0.5 mg / L and COD ≤ 10.0 mg / L).

Claims

1. A method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal, comprising the following steps: S1. The low carbon-nitrogen ratio wastewater enters the primary aerobic reactor equipped with iron shavings / elemental sulfur composite filler to carry out a simultaneous nitrification and denitrification process to remove part of the total nitrogen, organic matter and total phosphorus; the treated water enters the secondary anoxic reactor equipped with iron shavings / elemental sulfur composite filler to carry out a mixed culture denitrification process to further remove total nitrogen and continue to remove phosphorus; finally, in the tertiary aerobic reactor equipped with iron shavings / elemental sulfur composite filler, an aerobic denitrification process is carried out to deeply remove nitrogen and enhance phosphorus removal; S2. The water treated in step S1 enters the sedimentation tank and is discharged after solid-liquid separation. Part of the precipitated sludge flows back to the primary aerobic reactor, and part is discharged as residual sludge.

2. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 1, characterized in that: In the step S1, the iron shavings / elemental sulfur composite filler has a composition weight ratio of iron shavings:elemental sulfur=4-6:1, and is packed in polyethylene mesh bags and loaded into reactors of various levels.

3. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 2, characterized in that: The packing density of the iron shavings / elemental sulfur composite filler in the first-stage aerobic reactor and the third-stage aerobic reactor is 70-80 kg / m 3 .

4. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 2, characterized in that: The packing density of the iron shavings / elemental sulfur composite filler in the secondary anoxic reactor is 100-110 kg / m 3 .

5. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 1, characterized in that: The reaction residence time of the primary aerobic reactor and the tertiary aerobic reactor in step S1 is 12 to 24 hours, and the dissolved oxygen concentration is controlled at 2.0 to 4.0 mg / L.

6. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 1, characterized in that: The reaction residence time of the secondary anoxic reactor in step S1 is 6 to 12 hours, and the dissolved oxygen concentration is controlled at 0.1 to 0.5 mg / L.

7. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 1, characterized in that: In step S1, when the C / N ratio of the influent sewage is 1 to 3, a small amount of low carbon-nitrogen ratio sewage directly enters the tertiary aerobic reactor to provide a carbon source for the aerobic denitrification process; when the C / N ratio of the influent sewage is less than 1, methanol or sodium acetate is added as an external carbon source to the influent of the primary aerobic reactor and the tertiary aerobic reactor to enhance the denitrification effect.

8. The method for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and polyculture denitrification and denitrification and phosphorus removal according to claim 1, characterized in that: In step S2, the sludge return ratio is controlled at 50% to 100%.

9. A reactor for simultaneous nitrification and denitrification of low carbon-nitrogen ratio wastewater and mixed culture and denitrification and denitrification and phosphorus removal, characterized in that: The denitrification and dephosphorization reactor comprises: a primary aerobic reactor (5) provided with a first iron shavings / elemental sulfur composite filler (4), a secondary anoxic reactor (11) provided with a second iron shavings / elemental sulfur composite filler (10), a tertiary aerobic reactor (18) provided with a third iron shavings / elemental sulfur composite filler (17), and a sedimentation tank (22); the water inlet side of the primary aerobic reactor (5) is connected to a water inlet pipe (1) provided with a first carbon source addition pipe (2), the water outlet side is provided with a first water outlet pipe (8), and the bottom is provided with a first aeration pipe (7); the water inlet side of the secondary anoxic reactor (1 ... and the water outlet side of the primary aerobic reactor (5) is connected to a water inlet pipe (1) provided with a first carbon source addition pipe (2). The third-stage aerobic reactor (18) is connected to the first outlet pipe (8), the outlet side is provided with a second outlet pipe (14), and the bottom is provided with a sludge mixer (13); the water inlet side of the third-stage aerobic reactor (18) is connected to the second outlet pipe (14) provided with a second carbon source addition pipe (15), the outlet side is provided with a third outlet pipe (21), and the bottom is provided with a second aeration pipe (20); the water inlet side of the sedimentation tank (22) is connected to the third outlet pipe (21), the outlet side is provided with a fourth outlet pipe (23), and the bottom is provided with a sludge discharge pipe (24) and a sludge return pipe (25), and the sludge return pipe (25) is connected to the water inlet pipe (1).

10. The low carbon-nitrogen ratio wastewater synchronous nitrification and denitrification-mixed culture denitrification and phosphorus removal reactor according to claim 9, characterized in that: The first-stage aerobic 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-stage anoxic 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; the third-stage aerobic reactor (18) is provided with a third water distribution channel (16) on the water inlet side, and a third water collection channel (19) on the water outlet side.

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