Method for realizing short-cut nitrification denitrification by using cefalexin inhibitor

Abstract

A method for realizing short-cut nitrification denitrification by using a cefalexin inhibitor belongs to the field of biological sewage treatment, is used for urban sewage treatment, and comprises the following steps: in a stably operated aerobic sequencing batch reactor, keeping the pH value at 7.4-8.0, the sludge concentration at 3200ml / L, the dissolved oxygen controlled at 1.5 mg / L-2. 7mg / L and the temperature at room temperature in the aerobic sequencing batch reactor; 5 mg / L-15 mg / L of cefalexin is added into the aerobic sequencing batch reactor every day, and short-cut nitrification can be achieved after the operation period is 8 days. According to the method, cefalexin can be added into the aerobic sequencing batch reactor, harsh environmental conditions are not needed, operation is simple, the requirement for the inlet water ammonia nitrogen concentration in the aerobic sequencing batch reactor is not too high, the efficiency of taking out the ammonia nitrogen in the urban domestic sewage is improved, and the economic benefit is increased. And short-cut nitrification in the aerobic sequencing batch reactor can be rapidly realized and stably maintained.

Description

Technical Field

[0001] The present application belongs to the field of biological sewage treatment, and more specifically, relates to a method for realizing short-range nitrification and denitrification using a cephalexin inhibitor. Background Art

[0002] Since the C / N (ratio of carbon content to nitrogen content) in urban domestic sewage is relatively low, the biological denitrification process is easily limited by insufficient carbon source. Therefore, a relatively efficient, inexpensive and sustainable biological denitrification method is needed, such as a short-range nitrification biological denitrification method.

[0003] Short-range nitrification biological denitrification is mainly carried out by ammonia oxidizing bacteria (AOB) to convert NH4 + -N is converted to NO2 - -N, and then denitrifying bacteria (nitrite-reducing bacteria) directly convert NO2 - -N is converted into N2. Its core is to achieve short-term nitrification and denitrification by inhibiting nitrite oxidizing bacteria (NOB). Compared with full-process nitrification, short-term nitrification and denitrification has the following advantages: ① The ammonia oxidation stage can reduce the oxygen supply by 25%; ② The denitrification stage can reduce the carbon source by 40%; ③ The reaction time is short and the reactor volume can be reduced by 30%~40%; ④ The sludge production can be reduced by about 55%. Short-term nitrification is achieved through the following principles: NH4 + -N+1.5 O2→NO2 - -N+H2O+2H + .

[0004] The implementation methods of short-term nitrification in the prior art include the following aspects: (1) Since temperature is an important factor affecting the growth rate and metabolic activity of nitrifying microorganisms, and AOB and NOB have different sensitivities to temperature, under higher temperatures (35°C~45°C), the growth rate of AOB is significantly improved, and its generation cycle can be shortened to half of that of NOB. When the temperature is reduced to 5°C~15°C, the growth rate of NOB is faster than that of AOB. Therefore, the regulation of short-term denitrification reaction can be achieved by adjusting the temperature. (2) During the short-term nitrification reaction, oxygen participates in the oxidation reaction of ammonia nitrogen and nitrite as an electron acceptor. In order to ensure that ammonia nitrogen is fully converted into nitrate, the dissolved oxygen (DO) in the reaction system is usually guaranteed to be above 2.5 mg / L. Since NOB has a much lower affinity for oxygen than AOB, when the DO of the reaction system is reduced to below 1 mg / L, NOB will not be able to obtain enough DO for the oxidation of nitrite. Therefore, by controlling DO to achieve partial nitrification, not only can the oxygen transfer efficiency be improved and aeration energy consumption be saved, but also a lower DO in the effluent can be achieved, which is beneficial to the denitrification or anaerobic ammonium oxidation process in the back end. (3) Since the addition of hydroxylamine and hydrazine can effectively inhibit the growth of NOB and promote the nitrite process, the long-term addition of hydroxylamine or hydrazine alone may cause NOB to gradually develop drug resistance, thereby destroying the short-range nitrification process.

[0005] In the short-term nitrification reaction, the inhibition of NOB activity can help to achieve the washing of NOB in the nitrifying bacteria and the screening of AOB dominant bacteria, so as to optimize the microbial population in the short-term nitrification biological denitrification method. However, how to achieve the inhibition of NOB activity and the screening of AOB dominant bacteria to solve the problem of rapid realization and stable maintenance of short-term nitrification of urban domestic sewage in aerobic sequencing batch reactors has become one of the technical problems that the industry needs to solve. Summary of the invention

[0006] The purpose of the present application is to provide a method for achieving short-term nitrification and denitrification by using a cephalexin inhibitor, which can be achieved by adding cephalexin in an aerobic sequencing batch reactor, does not require harsh environmental conditions and is simple to operate, and does not have excessive requirements on the influent ammonia nitrogen concentration in the aerobic sequencing batch reactor, thereby helping to improve the ammonia nitrogen removal efficiency in urban domestic sewage and maintain the rapid realization and stable maintenance of short-term nitrification in the aerobic sequencing batch reactor.

[0007] To achieve the above objectives, this application is implemented through the following technical solutions: The present application discloses a method for achieving short-range nitrification and denitrification using a cephalexin inhibitor, which comprises adding 5 mg / L to 15 mg / L of cephalexin per day to an aerobic sequencing batch reactor with an internal pH value of 7.4 to 8.0, a sludge concentration of 3200 ml / L, dissolved oxygen controlled at 1.5 mg / L to 2.7 mg / L, a temperature of room temperature and stable operation, and achieving short-range nitrification in an operation cycle of 8 days.

[0008] As one of the preferred technical solutions, in the present application, the amount of cephalexin added into the aerobic sequencing batch reactor every day is 10 mg / L to 15 mg / L.

[0009] As one of the preferred technical solutions, in the present application, the average ammonia nitrogen content in the effluent of the aerobic sequencing batch reactor is below 15 mg / L.

[0010] Compared with the prior art, the beneficial effects of this application are: The present application solves the bottleneck problem of slow start-up and instability of short-range nitrification in a sequencing batch reactor (SBR) by adding a certain concentration of cephalexin in the SBR, and has the advantages of high denitrification efficiency, fast reaction rate, saving operation cost and obtaining excellent effluent water quality, and maintains the rapid realization and stable maintenance of short-range nitrification in the sequencing batch reactor, which is helpful for the treatment of urban domestic sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a curve diagram of the relationship between the change of denitrification performance of the nitrification system with time at different concentrations of cephalexin in the present application.

[0012] Figure 2 This is a curve diagram of the change of nitrite accumulation rate of the nitrification system with time at different concentrations of cephalexin in the present application. DETAILED DESCRIPTION

[0013] The technical solution described in this application is further described below in conjunction with the accompanying drawings and embodiments.

[0014] As a β-lactam antibiotic, cephalexin mainly inhibits the cross-linking between linear peptide sugar polymer chains and the binding with penicillin binding protein through the β-lactam ring, thereby inhibiting the synthesis of cell walls, changing the permeability of cell membranes and inhibiting the synthesis of bacterial proteins, resulting in cell rupture and death. Appropriate antibiotic concentrations can improve the removal efficiency of bacteria for pollutants. Cephalexin has different inhibition levels for AOB and NOB, among which AOB has a stronger tolerance to cephalexin and can achieve the degradation of cephalexin in the presence of ammonia. In the present application, although cephalexin has an inhibitory effect on AOB and NOB in the nitrifying bacteria, the inhibition level for NOB is higher. With the continued addition of cephalexin in urban sewage, the denitrification performance of the nitrification system gradually decreases, but as the short-range nitrification reaction continues, the AOB activity in the nitrifying bacteria will gradually recover, and the activity of NOB will be completely inhibited, thereby achieving the elution of NOB in the nitrifying bacteria and the screening of the dominant genus of AOB, and optimizing the microbial species population.

[0015] Example 1

[0016] A method for realizing short-range nitrification and denitrification using a cephalexin inhibitor, wherein an aerobic sequencing batch reactor is marked as R1, the pH value in the aerobic sequencing batch reactor is consistent with or similar to the pH value of actually treated urban domestic sewage, both of which are controlled between 7.4 and 8.0, the concentration of sludge in the aerobic sequencing batch reactor is 3200 mg / L, the dissolved oxygen (DO) is controlled between 1.5 mg / L and 2.7 mg / L, and the temperature in the aerobic sequencing batch reactor is room temperature.

[0017] Under the above conditions, 5 mg / L of cephalexin was added into the aerobic sequencing batch reactor once a day, and the effluent trinitrogen of the aerobic sequencing batch reactor was monitored for a period of 35 days. The experimental results were recorded.

[0018] Example 2

[0019] A method for realizing short-range nitrification and denitrification using a cephalexin inhibitor, wherein an aerobic sequencing batch reactor is marked as R2, the pH value in the aerobic sequencing batch reactor is consistent with or similar to the pH value of actually treated urban domestic sewage, both of which are controlled between 7.4 and 8.0, the concentration of sludge in the aerobic sequencing batch reactor is 3200 mg / L, the dissolved oxygen (DO) is controlled between 1.5 mg / L and 2.7 mg / L, and the temperature in the aerobic sequencing batch reactor is room temperature.

[0020] Under the above conditions, 10 mg / L of cephalexin was added into the aerobic sequencing batch reactor once a day, and the effluent trinitrogen of the aerobic sequencing batch reactor was monitored, maintaining the same operation cycle as in Example 1, and recording the experimental results.

[0021] Example 3

[0022] A method for realizing short-range nitrification and denitrification using a cephalexin inhibitor, wherein an aerobic sequencing batch reactor is marked as R3, the pH value in the aerobic sequencing batch reactor is consistent with or similar to the pH value of actually treated urban domestic sewage, both of which are controlled between 7.4 and 8.0, the concentration of sludge in the aerobic sequencing batch reactor is 3200 mg / L, the dissolved oxygen (DO) is controlled between 1.5 mg / L and 2.7 mg / L, and the temperature in the aerobic sequencing batch reactor is room temperature.

[0023] Under the above conditions, 15 mg / L of cephalexin was added into the aerobic sequencing batch reactor once a day, and the effluent trinitrogen of the aerobic sequencing batch reactor was monitored, maintaining the same operation cycle as Example 1, and recording the experimental results.

[0024] Comparison Example The aerobic sequencing batch reactor is marked as R4. The pH value in the aerobic sequencing batch reactor is consistent with or close to the pH value of the actually treated urban domestic sewage, both of which are controlled between 7.4 and 8.0. The concentration of sludge in the aerobic sequencing batch reactor is 3200 mg / L, the dissolved oxygen (DO) is controlled between 1.5 mg / L and 2.7 mg / L, and the temperature in the aerobic sequencing batch reactor is room temperature.

[0025] Under the above conditions, 20 mg / L of cephalexin was added to the aerobic sequencing batch reactor once a day, and the effluent trinitrogen of the aerobic sequencing batch reactor was monitored, and the same operation cycle as Example 1 was maintained (because the aerobic sequencing batch reactor R4 would completely lose its denitrification performance on the 25th day due to the excessive concentration of cephalexin at this concentration of cephalexin, therefore, the data of the aerobic sequencing batch reactor R4 were counted up to the 25th day, and the data from the 26th to the 30th day were the same as the 25th day). And the experimental results were recorded.

[0026] Depend on Figure 1 From the recorded experimental results, it can be seen that in the early stage of adding cephalexin to aerobic sequencing batch reactors R1 to aerobic sequencing batch reactors R4, different concentrations of cephalexin have a certain effect on the removal effect of ammonia nitrogen, but with the increase of the operation cycle, the system with lower concentration of cephalexin added gradually recovers the removal effect of ammonia nitrogen. From the data of stable operation after adding cephalexin, the average ammonia nitrogen in the effluent of aerobic sequencing batch reactors R1, aerobic sequencing batch reactors R2 and aerobic sequencing batch reactors R3 are all below 15 mg / L, while the denitrification performance of aerobic sequencing batch reactor R4 is completely lost due to the high concentration of cephalexin.

[0027] Depend on Figure 2It can be seen from the recorded content that as the concentration of cephalexin increases, the time to start short-range nitrification becomes shorter, especially in aerobic sequencing batch reactor R2 and aerobic sequencing batch reactor R3, where the average accumulation rate of nitrite reaches more than 90% on the 8th day and the 18th day, respectively.

[0028] Finally, although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for realizing short-range nitrification and denitrification using a cephalexin inhibitor, characterized in that: The method includes adding 5mg / L~15mg / L of cephalexin every day into an aerobic sequencing batch reactor with an internal pH value of 7.4~8.0, a sludge concentration of 3200ml / L, dissolved oxygen controlled at 1.5mg / L~2.7mg / L, and a temperature of room temperature and stable operation, and short-range nitrification can be achieved after an operation cycle of 8 days.

2. The method for realizing short-range nitrification and denitrification using a cephalexin inhibitor according to claim 1, characterized in that: The amount of cephalexin added daily into the aerobic sequencing batch reactor is 10 mg / L~15 mg / L.

3. The method for realizing short-range nitrification and denitrification using a cephalexin inhibitor according to claim 2, characterized in that: The average ammonia nitrogen content of the effluent from the aerobic sequencing batch reactor is below 15 mg / L.

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