Advanced sewage denitrification method based on pyrite polyculture denitrification system

Abstract

The invention discloses an advanced sewage denitrification method based on a pyrite polyculture denitrification system, which comprises the following steps: (1) fully mixing to-be-treated sewage, sulfur autotrophic denitrification sludge and pyrite, filling a reactor with the mixture, and carrying out internal reflux culture for a preset time to gradually form a film on the surface of the pyrite so as to carry out primary denitrification on the sewage; and (2) mixing sewage to be treated with a predetermined amount of NaCl-containing liquid, feeding the mixture into the reactor in an upward continuous flow manner, and operating the reactor to further denitrify the sewage. According to the present invention, the NaCl-containing liquid is added during the sewage nitrogen removal treatment, such that the deep nitrogen removal efficiency of the pyrite polyculture denitrification system is successfully improved, and the scientific guidance reference can be provided for the promotion and the application of the pyrite-mediated denitrification system in the coastal urban sewage treatment plant.

Description

Technical Field

[0001] The invention relates to the field of urban sewage deep treatment, and in particular to a sewage deep denitrification method based on a pyrite polyculture denitrification system. Background Art

[0002] In recent years, with the rapid growth of urban population, urban water environment is facing increasing nitrogen pressure. In the context of carbon neutrality and sustainable development of urban ecology, countries have increasingly stringent nitrogen emission standards for municipal sewage treatment plants. Deep denitrification of biochemical tailwater from sewage treatment plants has become the most direct and effective way to face this severe challenge. Pyrite-mediated denitrification technology has attracted widespread attention due to its advantages of low cost, safety and phosphorus removal capabilities, and has certain application prospects in deep denitrification of municipal sewage treatment plants. However, due to the surface crystal structure of pyrite, it is difficult for it to continuously provide electron donors for stable and efficient nitrate nitrogen removal, which limits the promotion and application of pyrite-mediated denitrification technology.

[0003] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for deep denitrification of sewage based on a pyrite polyculture denitrification system, which can improve the denitrification efficiency of sewage.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A method for deep denitrification of sewage based on a pyrite polyculture denitrification system comprises the following steps:

[0007] (1) The sewage to be treated, the sulfur autotrophic denitrification sludge and the pyrite are fully mixed and filled into a reactor, and the reactor is refluxed and cultured for a predetermined time so that a film gradually forms on the surface of the pyrite to perform preliminary denitrification on the sewage;

[0008] (2) The sewage to be treated and a predetermined amount of liquid containing NaCl are mixed and then introduced into the reactor in an upward continuous flow manner and the reactor is operated to further denitrify the sewage.

[0009] Furthermore, in step (2), after the sewage to be treated is mixed with a predetermined amount of liquid containing NaCl, the salinity is in the range of 0.5 to 10 g / L, preferably, the salinity is in the range of 5 to 10 g / L.

[0010] Furthermore, in step (1), the initial mixed liquor suspended solids concentration of the sulfur autotrophic denitrification sludge in the reactor is in the range of 3750 to 4500 mg / L.

[0011] Furthermore, in step (1), the particle size of the pyrite is 2 to 3 mm.

[0012] Furthermore, the reactor is a pyrite upflow fixed bed reactor.

[0013] Furthermore, in step (2), the hydraulic retention time of the sewage is 8±0.5h.

[0014] Furthermore, in step (1), the sulfur autotrophic denitrification sludge is obtained by the following steps: adding 2.160-2.165 g / L KNO 3 , 0.260~0.265g / LKH 2 PO 4 , 0.910~0.915g / LNaHCO 3 and 4.515~4.520g / LNa 2 S 2 O 3 ·5H 2 O, acclimate and culture at room temperature, and when the nitrate nitrogen removal rate is stabilized at more than 70%, it is considered that the sulfur autotrophic denitrification sludge is successfully cultured.

[0015] Furthermore, the internal reflux culture time in step (1) is 3-5 days.

[0016] Furthermore, the liquid containing NaCl is seawater; and the sewage to be treated is biochemical tail water from a municipal sewage plant.

[0017] The present invention has the following beneficial effects:

[0018] (1) The present invention utilizes a liquid containing NaCl to successfully improve the deep denitrification efficiency of the pyrite co-culture denitrification system. The present invention does not control the dissolved oxygen concentration of the influent, that is, the denitrifying bacteria can be enhanced under normal influent dissolved oxygen conditions, thereby enhancing the pyrite-mediated denitrification effect and achieving a better denitrification effect in the reactor.

[0019] (2) In the preferred technical solution, after adding the NaCl-containing liquid, when the inlet salinity is 5 and 10 g / L, the average nitrate nitrogen removal rate is significantly improved compared with when no NaCl-containing liquid is added, which is increased by 35.8% and 60.3%, respectively. The average nitrate nitrogen removal rate is increased from 44.3% when no NaCl-containing liquid is added to 58.1% and 67.9%, respectively, and the average nitrate nitrogen removal rate is increased by 31.2% and 53.3%, respectively.

[0020] (3) In the preferred technical solution, the liquid containing NaCl is seawater, which is relatively easy to obtain in coastal cities. The salinity of seawater can be adjusted to a corresponding concentration range through dilution to varying degrees. Compared with other methods for enhancing the deep denitrification of pyrite polyculture and denitrification systems, the cost is lower and the time to achieve the promotion effect is shorter.

[0021] The present invention can provide more scientific guidance reference for the promotion and application of pyrite-mediated denitrification systems in sewage treatment plants in coastal cities. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the nitrate nitrogen removal rate under different salinity conditions in the embodiment of the present invention.

[0023] Figure 2 It is the nitrate nitrogen removal rate under different salinity conditions in the embodiment of the present invention.

[0024] Figure 3 It is the percentage improvement of nitrate nitrogen removal rate under different salinity conditions in the embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention. In the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0026] Herein, "room temperature" refers to a temperature in the range of 25°C to 35°C.

[0027] The specific embodiment of the present invention provides a method for deep denitrification of sewage based on a pyrite polyculture denitrification system, which comprises the following steps:

[0028] (1) The sewage to be treated, the sulfur autotrophic denitrification sludge and the pyrite are fully mixed and filled into a reactor, and the reactor is refluxed and cultured for a predetermined time so that a film gradually forms on the surface of the pyrite to perform preliminary denitrification on the sewage;

[0029] (2) The sewage to be treated is mixed with a predetermined amount of liquid containing NaCl and then continuously flowed upward. The wastewater enters the reactor and operates the reactor to further denitrify the wastewater.

[0030] The principle of deep denitrification of sewage of the present invention is as follows: a certain amount of NaCl-containing liquid is added to a stably operating reactor. The addition of the NaCl-containing liquid, on the one hand, promotes the interaction between microorganisms in the pyrite-mediated denitrification system, helps the microbial community to form a tighter cluster structure, reduces the formation of modular networks, ensures the stability of the microbial community structure in the pyrite-mediated denitrification system, and improves the denitrification efficiency; on the other hand, the addition of the NaCl-containing liquid accelerates the precipitation rate of sulfur ions and ferrous ions from pyrite to a certain extent, constructs a more extensive electron transfer channel between pyrite and denitrification functional bacteria, thereby improving the electron transfer efficiency of pyrite, and finally accelerating the removal rate of nitrate nitrogen.

[0031] In some embodiments, in step (2), after the sewage to be treated is mixed with a predetermined amount of liquid containing NaCl, the salinity (mass concentration of NaCl) is in the range of 0.5 to 10 g / L, and more preferably, the salinity is in the range of 5 to 10 g / L. The NaCl-containing liquid added in the present invention has an appropriate concentration range. When the salinity of the introduced NaCl-containing liquid is too high, it will have a certain toxic effect on microorganisms, and the action of chloride ions and oxygen may increase the risk of pyrite forming oxides, which also hinders the contact between microorganisms, pyrite and nitrate nitrogen in sewage to a certain extent, and ultimately affects the growth of microorganisms and the removal effect of nitrate nitrogen.

[0032] In some embodiments, in step (1), the initial mixed liquor suspended solids concentration (MLSS) of the sulfur autotrophic denitrification sludge in the reactor is in the range of 3750 to 4500 mg / L. Mixed liquor suspended solids concentration (MLSS) represents the suspended solids content in mg / L and refers specifically to the concentration of pure sludge.

[0033] In some embodiments, in step (1), the particle size of the pyrite is 2 to 3 mm.

[0034] In some embodiments, the reactor is a pyrite upflow fixed bed reactor.

[0035] In some embodiments, in step (2), the hydraulic retention time is determined according to the degradation of the pollutants, and preferably the hydraulic retention time of the sewage is 8±0.5h.

[0036] In some embodiments, in step (1), the sulfur autotrophic denitrification sludge is obtained by the following steps: adding 2.160-2.165 g / L KNO 3 , 0.260~0.265g / L KH 2 PO 4 , 0.910~0.915g / L NaHCO3 and 4.515~4.520g / LNa 2 S 2 O 3 ·5H 2 O, acclimate and culture at room temperature, and when the nitrate nitrogen removal rate is stabilized at more than 70%, it is considered that the sulfur autotrophic denitrification sludge is successfully cultured.

[0037] In some embodiments, the internal reflux culture time in step (1) is 3-5 days.

[0038] In some embodiments, the NaCl-containing liquid is seawater; and the sewage to be treated is biochemical tail water from a municipal sewage plant.

[0039] The specific embodiments of the present invention are further described below.

[0040] Example

[0041] The reactor used in this embodiment is a pyrite upflow fixed bed reactor with an effective volume of 1 L. The sulfur autotrophic denitrification sludge used in this embodiment can be obtained from the oxidation ditch in long-term stable operation and is obtained by culturing and domesticating in the laboratory SBR model. The culturing and domestication conditions are as follows: the oxidation ditch sludge is placed in a reactor with a stirring function, and the following substances are added: KNO 3 (2.160~2.165g / L), KH 2 PO 4 (0.260~0.265g / L), NaHCO 3 (0.910~0.915g / L) and Na 2 S 2 O 3 ·5H 2 O (4.515 ~ 4.520g / L), control the inlet sulfur-nitrogen ratio of 3.89: 1, carry out acclimatization and cultivation at room temperature, and when the nitrate nitrogen removal rate of the reactor is stable at more than 70%, it is considered that the sulfur autotrophic denitrification sludge is successfully cultivated. The method for deep denitrification of sewage (biological tail water of municipal sewage plant) based on pyrite mixed culture denitrification system includes the following steps:

[0042] (1) The sewage to be treated, sulfur autotrophic denitrification sludge and pyrite with a particle size of 2 to 3 mm were fully mixed to make the initial sludge concentration (MLSS) in the reactor about 4000 mg / L. The microorganisms were formed on the surface of the pyrite by reflux cultivation in a peristaltic pump for 3 days to perform preliminary denitrification of the sewage.

[0043] (2) From the 4th day, the sewage to be treated is mixed with a predetermined amount of seawater and then enters the reactor in an upward continuous flow mode, and the reactor is operated in a continuous flow mode at room temperature, and the flow rate is adjusted so that the hydraulic retention time is 8 hours, so as to further denitrify the sewage. The water quality after the sewage to be treated is mixed with a predetermined amount of seawater and then enters the reactor in an upward continuous flow mode is: nitrate nitrogen concentration is 18-22 mg N / L, phosphate concentration is 1.8-2.2 mg P / L, COD concentration is 38-42 mg / L (corresponding to C / N=2), and on the 10th day of the operation of the reactor, the COD concentration is adjusted to 58-62 mg / L (corresponding to C / N=3), and the operation is for a total of 21 days.

[0044] This embodiment is divided into five groups of seawater ratios. The salinities of the sewage to be treated and the seawater after mixing in step (2) are 0, 500, 1000, 5000, and 10000 mg / L, respectively, so as to compare the denitrification effects of sewage with five influent salinities (with seawater added in different proportions).

[0045] The reactor efficiency is calculated as follows:

[0046] Starting from the addition of seawater, inlet and outlet water samples were taken every day and NO was measured by UV spectrophotometry. 3 - -N concentration, the nitrate nitrogen removal rate and removal rate are calculated using the following formula:

[0047] Nitrate nitrogen removal rate (%) = (influent nitrate nitrogen concentration - effluent nitrate nitrogen concentration) / influent nitrate nitrogen concentration * 100.

[0048] Nitrate nitrogen removal rate (mg N / (L·h) -1 =(influent nitrate nitrogen concentration - effluent nitrate nitrogen concentration) / hydraulic retention time.

[0049] The unit of nitrate nitrogen concentration is mg / L and the unit of operation time is h.

[0050] Calculate the improvement of nitrate nitrogen removal rate of the experimental group and the blank group (without seawater):

[0051] Improvement in nitrate nitrogen removal rate (%) = (nitrate nitrogen removal rate of the experimental group - nitrate nitrogen removal rate of the blank group) / nitrate nitrogen removal rate of the blank group * 100.

[0052] like Figure 1 , 2As shown in Figure 3, compared with the case without adding seawater (blank group), the average nitrate nitrogen removal rates of the reactors with salinities of 500, 1000, 5000, and 10000 mg / L increased by 11.7%, 9.5%, 35.8%, and 60.3%, respectively, and the average nitrate nitrogen removal rates increased by 7.0%, 3.9%, 31.2%, and 53.3%, respectively. It can be seen that the addition of seawater successfully improved the denitrification efficiency of the pyrite mixed culture denitrification system. 00mg / L, the salinity of 5000 and 10000mg / L has a better improvement effect (when the inlet salinity is 5 and 10g / L, the average nitrate nitrogen removal rate is significantly improved compared with the case without adding seawater, which is increased by 35.8% and 60.3% respectively, and the average nitrate nitrogen removal rate is increased from 44.3% when no seawater is added to 58.1% and 67.9% respectively, and the average nitrate nitrogen removal rate is increased by 31.2% and 53.3% respectively) and lower operating costs.

[0053] The above contents are further detailed descriptions of the present invention in combination with specific / preferred implementations, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the field, Without departing from the concept of the present invention, it is also possible to Some of the described embodiments are replaced or modified, and these replacements or modifications should be considered to belong to the protection scope of the present invention. In the description of this specification, the description of reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for deep denitrification of sewage based on pyrite polyculture and denitrification system, characterized in that: The steps include: (1) The sewage to be treated, the sulfur autotrophic denitrification sludge and the pyrite are fully mixed and filled into a reactor, and the reactor is refluxed and cultured for a predetermined time so that a film gradually forms on the surface of the pyrite to perform preliminary denitrification on the sewage; (2) The sewage to be treated and a predetermined amount of liquid containing NaCl are mixed and then introduced into the reactor in an upward continuous flow manner and the reactor is operated to further denitrify the sewage.

2. The method according to claim 1, characterized in that: In step (2), after the sewage to be treated is mixed with a predetermined amount of liquid containing NaCl, the salinity is in the range of 0.5 to 10 g / L, preferably, the salinity is in the range of 5 to 10 g / L.

3. The method according to claim 1, characterized in that: In step (1), the initial mixed liquor suspended solids concentration of the sulfur autotrophic denitrification sludge in the reactor is in the range of 3750 to 4500 mg / L.

4. The method according to claim 1, characterized in that: In step (1), the particle size of the pyrite is 2 to 3 mm.

5. The method according to claim 1, characterized in that: The reactor is a pyrite upflow fixed bed reactor.

6. The method according to claim 1, characterized in that: In step (2), the hydraulic retention time of the sewage is 8±0.5h.

7. The method according to claim 1, characterized in that: In step (1), the sulfur autotrophic denitrification sludge is obtained by culturing the following steps: adding 2.160-2.165 g / L KNO3, 0.260-0.265 g / L KH2PO4, 0.910-0.915 g / L NaHCO3 and 4.515-4.520 g / L Na2S2O3·5H2O to the sludge from the oxidation ditch, acclimatizing and culturing at room temperature, and when the nitrate nitrogen removal rate is stabilized at more than 70%, the sulfur autotrophic denitrification sludge is considered to be successfully cultivated.

8. The method according to claim 1, characterized in that: The internal reflux culture time in step (1) is 3-5 days.

9. The method according to claim 1, characterized in that: The liquid containing NaCl is seawater; the sewage to be treated is the biochemical tail water of a municipal sewage plant.

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