A method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater

Abstract

The present invention belongs to the technical field of urban sewage treatment and specifically discloses a method for promoting short-cut nitrification in urban sewage. The method involves operating a sequencing batch sludge reactor (SBR) at different carbon-nitrogen ratio gradients, with an initial ammonia-nitrogen concentration of 25 mg / L. Utilizing the principle that ammonia-oxidizing bacteria are more adaptable than nitrite-oxidizing bacteria, the carbon-nitrogen metabolic pathways of denitrifying bacteria and the competitive relationships between them are regulated under different carbon-nitrogen ratio conditions, thereby inhibiting the biological activity of nitrite-oxidizing bacteria and achieving short-cut nitrification in a relatively high carbon-nitrogen ratio system. Furthermore, this method inhibits nitrite-oxidizing bacteria through community structure, and the resulting inhibitory effect is more stable than that achieved through operational parameter manipulation, providing a new regulatory strategy for treating low-carbon-nitrogen ratio urban sewage.

Description

Technical Field

[0001] The invention belongs to the technical field of urban sewage treatment, and particularly relates to a method for promoting the short-range nitrification of low-concentration ammonia nitrogen wastewater. Background Art

[0002] With the improvement of residents' living standards and the acceleration of urbanization, the discharge volume and treatment pressure of domestic sewage have also increased, and the discharge standards of urban sewage treatment have also been improved. Biological denitrification of sewage is generally completed by two processes: nitrification and denitrification. The nitrification process is divided into ammonia oxidation stage and nitrite oxidation stage. These two stages are independently catalyzed by ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). The first stage is to convert ammonia nitrogen (NH4 + -N) is oxidized to nitrite nitrogen (NO2 - -N); and the second stage is to convert NO2 - -N is oxidized to nitrate nitrogen (NO3 - -N). Since the nitrification reaction is a different reaction catalyzed by two types of bacteria with completely different physiological characteristics, the nitrification reaction can be controlled to NO2 by properly controlling the conditions. - -N stage, blocking NO2 - -N is further oxidized, and a large amount of NO2 - -N accumulates to form short-term nitrification, followed by direct denitrification or anaerobic ammonium oxidation. - -N is an intermediate product in the process of nitrification and denitrification, which converts NH4 + -N is oxidized to NO2 - Direct denitrification after the denitrification reaction can save 50% of the aeration volume in the nitrification stage and 40% of the carbon source in the denitrification stage. In addition, the short-cut nitrification coupled with anaerobic ammonium oxidation denitrification process can save 50% of the aeration energy consumption and 100% of the carbon source. The application of short-cut nitrification further reduces sludge production and alleviates the pressure on sludge treatment, effectively promoting pollution reduction and carbon reduction in wastewater treatment.

[0003] Short-range nitrification technology is currently widely used in high-ammonia nitrogen wastewater such as sludge digestate and landfill leachate, but it has not yet been promoted and applied in low C / N (C / N<4) urban sewage treatment systems with larger water treatment volumes.

[0004] Currently, attempts are underway to achieve short-term nitrification in low-C / N wastewater. These approaches can be summarized into two approaches: one is to simultaneously elute or inactivate AOB and NOB from activated sludge, then exploit their growth advantage over NOB to specifically enrich AOB; the other is to exploit the differences in oxygen half-saturation constants between the two aerobic bacteria, specifically inhibiting NOB by maintaining a low dissolved oxygen environment (around 0.5 mg / L). While these two approaches manifest differently, both utilize the differential activity of AOB and NOB to lead to nitrite accumulation, ultimately resulting in short-term nitrification. Summary of the Invention

[0005] The purpose of the present invention is to propose a method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater. By utilizing the different ecological niches and functional roles of AON and NOB in the community, the interaction relationship between denitrifying bacteria is regulated by a high carbon-nitrogen ratio, thereby reducing the importance of NOB in the nitrogen conversion pathway, thereby inhibiting the biological activity of NOB and promoting the formation of short-range nitrification.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for promoting the short-cut nitrification of low-concentration ammonia nitrogen wastewater comprises the following steps:

[0008] The sludge containing nitrifying bacteria is inoculated into the SBR reactor, and then low-concentration sewage is introduced to control the C / N ratio of the sewage entering the reactor to 3.5-4.5, and aeration is operated.

[0009] As a better technical solution of the invention: the sludge is obtained from the aeration tank treatment unit of the sewage plant and then cultured with sewage, and the sludge concentration MLSS in the SBR reactor is 4000-4500 mg / L.

[0010] As a better technical solution of the invention: the ammonia nitrogen concentration of the imported sewage is set to 25 mg / L.

[0011] As a better technical solution of the invention: the aeration volume is 750 mL / min.

[0012] As a better technical solution of the invention: the pH fluctuation range during the operation cycle is 7.3-8.7.

[0013] As a more optimal technical solution of the invention: during the operation cycle, the stirrer stirs throughout the reaction cycle, and the stirring speed is 200 rpm.

[0014] As a more optimal technical solution of the present invention: the C / N ratio is adjusted by adding sodium acetate into the imported sewage.

[0015] As a more optimal technical solution of the present invention: 150 mg / L sodium bicarbonate is added to provide an inorganic carbon source and maintain the pH stability of the system.

[0016] As a more optimal technical solution of the present invention: after all ammonia nitrogen is converted, 120 mg / L of COD is added and anaerobically stirred for 4 hours until the COD is completely consumed.

[0017] The beneficial effects are as follows:

[0018] The promotion method provided by the present invention is simple, and NOB inhibition is achieved only by regulating the interspecies relationship through C / N ratio. The organic carbon source regulates the microorganisms, and short-term nitrification can be achieved without real-time monitoring of dissolved oxygen and adjustment of reaction parameters. Secondly, sodium acetate is selected as the organic carbon source, which is cheap, easily available, and widely used for carbon source addition in the denitrification stage. The present invention adds it to the nitrification stage, which can reduce the overall carbon source dosage by 20%. Finally, the short-term nitrification formed by the method will not easily disappear with the adjustment of operating parameters, and increasing the carbon-nitrogen ratio of the influent can accelerate the formation of short-term nitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a graph showing the single-cycle operation data results after the formation of short-range nitrification in Example 4.

[0020] Figure 2 This is a graph showing the single-cycle operation data results after the formation of short-range nitrification in Example 7.

[0021] Figure 3 The single cycle operation data result diagram of Example 8.

[0022] Figure 4 These are community structure network diagrams of three carbon-nitrogen ratio gradients, where (a), (b), and (c) represent carbon-nitrogen ratios of 3.5, 1, and 0, respectively. DETAILED DESCRIPTION

[0023] The following examples are provided to further understand the present invention, but are not intended to limit the present invention to the best mode of implementation, nor to limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0024] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0025] The following examples used a sequencing batch activated sludge reactor with an effective reaction volume of 10 L and a sludge concentration of 4200 mg / L. A stirring device was installed above the reactor at a speed of 200 rpm to ensure uniform mixing of the sludge and water. An aeration device was installed at the bottom of the reactor at a rate of 750 mL / min to ensure aerobic conditions in the system. The experiments used synthetic wastewater at an operating temperature of 25°C and a pH range of 7.3-8.7.

[0026] In the following example, eight 10L SBR reactors were inoculated with fully nitrified sludge, ensuring that the aeration rate, stirring speed, operating mode and other inlet conditions were the same. The inlet carbon-nitrogen ratio was set to 5, 4.5, 4, 3.5, 3, 2, 1 and 0, respectively. The carbon-nitrogen metabolic pathway of the denitrifying bacteria was regulated by the inlet carbon-nitrogen ratio, the electron transport system of NOB was weakened, and the species abundance and biological activity of NOB were suppressed through long-term acclimation, thereby achieving short-term nitrification formation in a relatively high carbon-nitrogen ratio system.

[0027] Example 1

[0028] The ammonia nitrogen concentration of the SBR influent was 25 mg / L, the COD was 125 mg / L, and the carbon-nitrogen ratio was 5. After 3 hours of aeration and stirring, all the ammonia nitrogen was converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration was about 11.3 mg / L. The calculated nitrite accumulation rate (NAR) was 53.2%.

[0029] Example 2

[0030] The ammonia nitrogen concentration of the SBR influent was 25 mg / L, the COD was 112.5 mg / L, and the carbon-nitrogen ratio was 4.5. After 2.5 h of aeration and stirring, all the ammonia nitrogen was converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration was about 11.7 mg / L, and the calculated NAR was 66.5%.

[0031] Example 3

[0032] The ammonia nitrogen concentration of the SBR influent was 25 mg / L, the COD was 100 mg / L, and the carbon-nitrogen ratio was 4. After 2.5 h of aeration and stirring, all the ammonia nitrogen was converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration was about 12.2 mg / L, and the calculated NAR was 67.1%.

[0033] Example 4

[0034] The ammonia nitrogen concentration of the SBR influent is 25 mg / L, COD is 87.5 mg / L, and the carbon-nitrogen ratio is 3.5. After 2 hours of aeration and stirring, all the ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration is about 12.9 mg / L. The calculated NAR is 68.7%. Figure 1 shown.

[0035] Example 5

[0036] The ammonia nitrogen concentration of the SBR influent was 25 mg / L, COD was 75 mg / L, and the carbon-nitrogen ratio was 3. After 2 hours of aeration and stirring, all the ammonia nitrogen was converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration was about 11.4 mg / L, and the calculated NAR was 53.4%.

[0037] Example 6

[0038] The ammonia nitrogen concentration of the SBR influent was 25 mg / L, COD was 50 mg / L, and the carbon-nitrogen ratio was 2. After 2 hours of aeration and stirring, all the ammonia nitrogen was converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration was about 9.7 mg / L, and the calculated NAR was about 40.6%.

[0039] Example 7

[0040] The ammonia nitrogen concentration of the SBR influent is 25 mg / L, COD is 25 mg / L, and the carbon-nitrogen ratio is 1. After 2 hours of aeration and stirring, all the ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen, of which the nitrite nitrogen concentration is about 8.5 mg / L. The calculated NAR is 37.6%. Figure 2 shown.

[0041] Example 8

[0042] The ammonia nitrogen concentration of the SBR influent is 25 mg / L, COD is 0 mg / L, and the carbon-nitrogen ratio is 0. After 2 hours of aeration and stirring, all the ammonia nitrogen is converted into nitrate nitrogen, and there is no nitrite nitrogen accumulation. Figure 3 shown.

[0043] In the above examples, the regulation of short-range nitrification by different C / N ratios was verified. Figure 4 As shown in the figure, the red lines and green lines represent the positive correlation and negative correlation between the bacterial communities, respectively. The number of lines represents the degree of correlation of the species in the community. Nitrosomonas and Nitrospira are typical representatives of AOB and NOB, respectively. The degree of correlation of Nitrospira in different carbon-nitrogen ratio systems: carbon-nitrogen ratio 3.5 system < carbon-nitrogen ratio 1 system < carbon-nitrogen ratio 0 system. It can be seen that the importance of NOB in the community in the high carbon-nitrogen ratio system is reduced, which successfully reduces the functional role of nitrite oxidizing bacteria, inhibits the biological activity of NOB, and realizes short-term nitrification. The present invention utilizes the different adaptability of AOB and NOB to the microbial community, regulates the community structure by controlling C / N, drives the competitive relationship between bacteria to inhibit NOB activity and promote AOB activity. Compared with the existing technology, it is simpler and does not need to change the aeration volume in real time to control the dissolved oxygen concentration. In addition, the short-term nitrification formed by the patented method has good stability.

[0044] The activated sludge short-cut nitrification resulted in a nitrite nitrogen accumulation rate exceeding 50%. This indicates that Examples 1-5 promote the short-cut nitrification of activated sludge. The reaction time in Example 1 was longer, and the nitrite accumulation rate in Example 5 was lower. Therefore, Examples 2, 3, and 4 represent the optimal C / N ranges, but the reaction times in Examples 2 and 3 are longer than in Example 4.

[0045] The promotion method provided by the present invention inhibits the biological activity of NOB in the community structure, and the short-term nitrification effect formed is more stable than the control of parameters such as physical and chemical indicators. AOB that performs ammonia oxidation function and NOB that performs nitrite oxidation function are both regulated by the symbiotic flora in the denitrification community, and NOB is more affected by the symbiotic flora than AOB. By adjusting the carbon-nitrogen ratio in the influent, and then regulating the carbon and nitrogen metabolic pathways of the denitrification community, the interaction relationship between the flora is changed to inhibit the biological activity of nitrite oxidizing bacteria, and ultimately increasing the difference between ammonia oxidation activity and nitrite oxidation activity to form short-term nitrification.

[0046] The influent ammonia nitrogen concentration of the present invention is only 25 mg / L, which is comparable to the ammonia nitrogen concentration in urban sewage, and is mainly used to treat low-concentration ammonia nitrogen wastewater. The use of nitrifying granular sludge for wastewater treatment requires advanced cultivation. The present invention uses activated sludge, which can be directly obtained from a sewage treatment plant.

[0047] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for promoting the short-cut nitrification of low-concentration ammonia nitrogen wastewater, characterized in that: The steps include: Sludge containing nitrifying bacteria is inoculated into an SBR reactor, and then low-concentration sewage is introduced. The C / N ratio of the sewage entering the reactor is controlled at 3.5, and aeration is performed. The sludge is obtained from the aeration tank treatment unit of the sewage plant and then cultured with sewage. The sludge concentration (MLSS) in the SBR reactor is 4000-4500 mg / L. The ammonia nitrogen concentration in the introduced sewage is set to 25 mg / L. The C / N ratio is adjusted by adding sodium acetate to the introduced sewage. The aeration rate is 750 mL / min. The pH fluctuation range during the operation cycle is 7.3-8.

7.

2. The method for promoting the short-cut nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, wherein: During the operation cycle, the stirrer stirs throughout the reaction cycle at a stirring speed of 200 rpm.

3. The method for promoting the short-cut nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, wherein: 150 mg / L sodium bicarbonate was added to provide an inorganic carbon source and maintain a stable pH value in the system.

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