Method for promoting short-cut nitrification of low-concentration ammonia-nitrogen wastewater

Abstract

The invention belongs to the technical field of urban sewage treatment, and particularly discloses a method for promoting short-cut nitrification formation of urban sewage, which is characterized in that a sequencing batch activated sludge reactor (SBR) with different carbon nitrogen ratio gradients is operated, and the initial ammonia nitrogen concentration is 25 mg / L. Based on the principle that the adaptability of ammonia-oxidizing bacteria is stronger than that of nitrite-oxidizing bacteria, the carbon-nitrogen metabolic pathway of denitrifying flora and the mutual competition relationship among the flora are adjusted through different carbon-nitrogen ratio conditions, the biological activity of the nitrite-oxidizing bacteria is inhibited, and the purpose of forming short-cut nitrification by a system with a relatively high carbon-nitrogen ratio is achieved. And the method inhibits nitrite oxidizing bacteria on the community structure, the formed inhibition effect is more stable compared with operation parameter regulation, and a new regulation strategy is provided for low-carbon-nitrogen-ratio urban sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of urban sewage treatment, and in particular relates to a method for promoting 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, accompanied by the improvement of urban sewage treatment discharge standards. 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 within the range of 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, converting NH4 + -N is oxidized to NO2 - -N and then directly undergo denitrification reaction, which 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-range nitrification coupled with anaerobic ammonia oxidation denitrification process can save 50% of the aeration energy consumption and 100% of the carbon source. The application of short-range nitrification further reduces the sludge production, alleviates the pressure of sludge treatment, and effectively promotes the reduction of pollution and carbon in sewage treatment.

[0003] Short-range nitrification technology is currently widely used in high-ammonia nitrogen wastewaters 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] At present, attempts have been made in the field of short-range nitrification technology in low C / N wastewater. In summary, there are two forms: one is to wash or inactivate AOB and NOB in activated sludge at the same time, and then use the growth advantage of AOB over NOB to specifically enrich AOB; the other is to specifically inhibit NOB by controlling the low dissolved oxygen environment (about 0.5 mg / L) based on the different oxygen half-saturation constants of the two aerobic bacteria AOB and NOB. The two forms have different manifestations, but both form short-range nitrification by forming the activity difference between AOB and NOB, leading to nitrite accumulation. 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, utilizing the different ecological niches and functional roles of AON and NOB in the community, regulating the interaction relationship between denitrifying bacteria through a high carbon-nitrogen ratio, 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: A method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater, comprising the following steps: The sludge containing nitrifying bacteria is inoculated into the SBR reactor, and then low-concentration sewage is introduced. The C / N ratio of the sewage entering the reactor is controlled to be 3.5-4.5, and aeration is performed.

[0007] As a more optimal technical solution of the invention: the sludge is obtained from the aeration tank treatment unit of the sewage plant and then cultured through sewage, and the sludge concentration MLSS in the SBR reactor is 4000-4500 mg / L.

[0008] As a better technical solution of the invention: the ammonia nitrogen concentration of the introduced sewage is set to 25 mg / L.

[0009] As a better technical solution of the invention: the aeration volume is 750 mL / min.

[0010] As a better technical solution of the invention: the pH fluctuation range during the operation cycle is 7.3-8.7.

[0011] As a more optimal technical solution of the invention: during the operation cycle, the agitator stirs throughout the reaction cycle, and the stirring speed is 200 rpm.

[0012] As a more optimal technical solution of the present invention: the C / N is adjusted by adding sodium acetate into the imported sewage.

[0013] 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.

[0014] As a more optimal technical solution of the present invention: after all the ammonia nitrogen is converted, 120 mg / L of COD is added and anaerobically stirred for 4 hours until the COD is completely consumed.

[0015] The beneficial effects are as follows: The promotion method provided by the present invention is simple, and only the interspecies relationship is regulated by C / N to inhibit NOB. The organic carbon source regulates the microorganisms, and short-range nitrification can be achieved without real-time monitoring of dissolved oxygen and adjustment of reaction parameters. Secondly, the organic carbon source is selected as sodium acetate, which is cheap, easy to obtain and widely used in the carbon source addition in the denitrification stage. The present invention adds it to the nitrification stage, which can reduce the carbon source addition amount by 20% overall. Finally, the short-range nitrification formed by the method will not disappear easily with the adjustment of the operating parameters, and increasing the carbon-nitrogen ratio of the influent can accelerate the formation of short-range nitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a single cycle operation data result diagram after the short-range nitrification is formed in Example 4.

[0017] Figure 2 This is a single cycle operation data result diagram after the short-range nitrification is formed in Example 7.

[0018] Figure 3 This is a single cycle operation data result diagram of Example 8. Figure 4 These are community structure network diagrams of three carbon-nitrogen ratio gradients. (a), (b), and (c) represent carbon-nitrogen ratios of 3.5, 1, and 0, respectively. DETAILED DESCRIPTION

[0019] The following examples are provided for further understanding of the present invention, but are not limited to the best mode of implementation, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0020] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0021] The reactor used in the following examples is a sequencing batch activated sludge reactor with an effective reaction volume of 10L and a sludge concentration of 4200mg / L. A stirring device is installed above the reactor with a rotation speed of 200rpm to ensure uniform mixing of mud and water; an aeration device is installed at the bottom with an aeration volume of 750mL / min to ensure aerobic conditions in the system. Artificial synthetic wastewater is used as experimental water, the operating temperature is 25°C, and the pH fluctuation range is between 7.3-8.7.

[0022] In the following example, full-process nitrification sludge was inoculated in 8 10L SBR reactors to ensure that the aeration volume, stirring speed, operation mode and other inlet conditions were the same, and 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 transfer system of NOB was weakened, the species abundance and biological activity of NOB were suppressed by long-term domestication, and the short-range nitrification formation of a relatively high carbon-nitrogen ratio system was achieved.

[0023] Example 1 The ammonia nitrogen concentration of SBR influent was 25 mg / L, 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. The nitrite nitrogen concentration was about 11.3 mg / L, and the calculated nitrite accumulation rate (NAR) was 53.2%.

[0024] Example 2 The ammonia nitrogen concentration of SBR influent was 25 mg / L, COD was 112.5 mg / L, and the carbon-nitrogen ratio was 4.5. After 2.5 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 11.7 mg / L, and the calculated NAR was 66.5%.

[0025] Example 3 The ammonia nitrogen concentration of SBR influent was 25 mg / L, COD was 100 mg / L, and the carbon-nitrogen ratio was 4. After 2.5 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 12.2 mg / L, and the calculated NAR was 67.1%.

[0026] Example 4 The ammonia nitrogen concentration of the SBR influent was 25 mg / L, COD was 87.5 mg / L, and the carbon-nitrogen ratio was 3.5. 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 12.9 mg / L. The calculated NAR was 68.7%. Figure 1 shown.

[0027] Example 5 The ammonia nitrogen concentration of 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%.

[0028] Example 6 The ammonia nitrogen concentration of 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%.

[0029] Example 7 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, the ammonia nitrogen is completely 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.

[0030] Example 8 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.

[0031] 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, and the functional role of nitrite oxidizing bacteria is successfully reduced, the biological activity of NOB is inhibited, and short-range nitrification is achieved. The present invention utilizes the different adaptability of AOB and NOB to the microbial community, controls the community structure by controlling C / N, drives the competitive relationship between bacteria to inhibit NOB activity and promote AOB activity. Compared with the prior art, 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-range nitrification formed by the patented method has good stability.

[0032] The activated sludge short-range nitrification forms a nitrite nitrogen accumulation rate of more than 50%. It shows that Examples 1-5 can promote the activated sludge short-range nitrification formation. Among them, the reaction time of Example 1 is longer, and the nitrite accumulation rate in Example 5 is lower, so Examples 2, 3 and 4 are better C / N ranges, but the reaction time of Examples 2 and 3 is longer than that of Example 4.

[0033] The promotion method provided by the present invention inhibits the biological activity of NOB in the community structure, and the short-range nitrification effect formed is more stable than the regulation 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 finally the difference between ammonia oxidation activity and nitrite oxidation activity is increased to form short-range nitrification.

[0034] The influent ammonia nitrogen concentration of the present invention is only 25 mg / L, which is compared with the ammonia nitrogen concentration of 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.

[0035] The implementation methods of the present invention are not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater, characterized in that: The steps include: The sludge containing nitrifying bacteria is inoculated into the SBR reactor, and then low-concentration sewage is introduced. The C / N ratio of the sewage entering the reactor is controlled to be 3.5-4.5, and aeration is performed.

2. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: The sludge is obtained from the aeration tank treatment unit of the sewage plant and then cultured through sewage. The sludge concentration MLSS in the SBR reactor is 4000-4500 mg / L.

3. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: The ammonia nitrogen concentration in the introduced sewage is set to 25 mg / L.

4. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: The aeration rate is 750 mL / min.

5. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: The pH fluctuation range during the operation cycle is 7.3-8.

7.

6. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: During the operation cycle, the stirrer stirs throughout the reaction cycle, and the stirring speed is 200 rpm.

7. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: The C / N ratio is adjusted by adding sodium acetate to the introduced sewage.

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

9. The method for promoting short-range nitrification of low-concentration ammonia nitrogen wastewater according to claim 1, characterized in that: After all the ammonia nitrogen was converted, 120 mg / L of COD was added and stirred anaerobically for 4 hours until the COD was completely consumed.

Images