A method for realizing short-cut nitrification and denitrification by a cephalexin inhibitor

Abstract

A method for realizing short-cut nitrification and denitrification by a cephalexin inhibitor, belonging to the field of sewage biological treatment and used for urban sewage treatment, which includes maintaining the pH value in a stable aerobic sequencing batch reactor at 7.4 - 8.0, the sludge concentration at 3200 ml / L, the dissolved oxygen controlled at 1.5 mg / L - 2.7 mg / L, and the temperature at room temperature; adding 5 mg / L - 15 mg / L of cephalexin into the aerobic sequencing batch reactor every day, and short-cut nitrification can be achieved in an 8-day operation cycle. This application can realize short-cut nitrification by adding cephalexin into the aerobic sequencing batch reactor, without harsh environmental conditions and with simple operation, and has no excessive requirements for the influent ammonia nitrogen concentration in the aerobic sequencing batch reactor, which helps to improve the ammonia nitrogen removal efficiency in urban domestic sewage and maintain the rapid realization and stable maintenance of short-cut nitrification in the aerobic sequencing batch reactor.

Description

Technical Field

[0001] This application belongs to the field of biological sewage treatment. Specifically, it particularly relates to a method for realizing short-cut nitrification and denitrification by a cephalexin inhibitor. Background Technique

[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 restricted by insufficient carbon sources. Therefore, a relatively efficient, inexpensive and sustainable biological denitrification method is required, such as the short-cut nitrification biological denitrification method.

[0003] The short-cut nitrification biological denitrification method mainly involves ammonia-oxidizing bacteria (AOB) converting NH4 + -N into NO2 - -N, and then denitrifying bacteria (nitrite-reducing bacteria) directly converting NO2 - -N into N2. Its core is mainly to realize the short-cut nitrification and denitrification method by inhibiting nitrite-oxidizing bacteria (NOB). Compared with complete nitrification, the short-cut nitrification and denitrification method has the following advantages: ① The oxygen supply in the ammonia oxidation stage can be reduced by 25%; ② The carbon source in the denitrification stage can be reduced 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%. The short-cut nitrification is achieved through the following principle: NH4 + -N + 1.5 O2 → NO2 - -N + H2O + 2H + .

[0004] The implementation methods of shortcut 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 the sensitivities of AOB and NOB to temperature are quite different, at relatively high temperatures (referring to 35°C to 45°C), the growth rate of AOB is significantly increased, and its generation cycle can be shortened to half of that of NOB. When the temperature drops to 5°C to 15°C, the growth rate of NOB is faster than that of AOB. Therefore, the adjustment of shortcut denitrification reaction can be achieved by regulating the temperature. (2) During the process of shortcut nitrification reaction, oxygen participates in the oxidation reactions of ammonia nitrogen and nitrite as an electron acceptor. To ensure the full conversion of ammonia nitrogen into nitrate, the dissolved oxygen (DO) in the reaction system is usually maintained above 2.5 mg / L. Since the affinity of NOB for oxygen is much lower than that of AOB, when the DO of the reaction system drops below 1 mg / L, NOB will not be able to obtain enough DO for the oxidation of nitrite. Therefore, realizing partial nitrification through the regulation of DO can not only improve the oxygen transfer efficiency and save aeration energy consumption, but also achieve a lower DO in the effluent, which is beneficial to the subsequent denitrification or anaerobic ammonium oxidation process. (3) Since the addition of hydroxylamine and hydrazine can effectively inhibit the growth of NOB and promote the nitritation process at the same time, but when hydroxylamine or hydrazine is added alone for a long time, NOB may gradually develop drug resistance, thus destroying the shortcut nitrification process.

[0005] In the shortcut nitrification reaction, the inhibition of NOB activity can help to achieve the elution of NOB in the nitrifying bacteria community and the screening of AOB dominant bacteria, so as to optimize the microbial population in the shortcut nitrification biological nitrogen removal method. However, how to inhibit the activity of NOB and screen AOB dominant bacteria to solve the rapid realization and stable maintenance of shortcut nitrification of urban domestic sewage in an aerobic sequencing batch reactor has become one of the technical problems that the industry needs to solve. Summary of the Invention

[0006] The purpose of this application is to provide a method for realizing shortcut nitrification and denitrification with a cephalexin inhibitor, which can add cephalexin in an aerobic sequencing batch reactor, without harsh environmental conditions and with simple operation, and has no excessive requirements for the influent ammonia nitrogen concentration in the aerobic sequencing batch reactor, which helps to improve the ammonia nitrogen removal efficiency in urban domestic sewage and maintain the rapid realization and stable maintenance of shortcut nitrification in the aerobic sequencing batch reactor.

[0007] To achieve the above purpose, this application is realized through the following technical solutions:

[0008] A method for realizing short - cut nitrification and denitrification by a cephalexin inhibitor described in this application. This method includes adding 5mg / L - 15mg / L of cephalexin per day in an aerobic sequencing batch reactor with an internal pH value of 7.4 - 8.0, a sludge concentration of 3200ml / L, a dissolved oxygen controlled at 1.5mg / L - 2.7mg / L, at room temperature and with stable operation. A short - cut nitrification can be achieved after an 8 - day operation cycle.

[0009] As one of the preferred technical solutions, in this application, the amount of cephalexin added per day in the aerobic sequencing batch reactor is 10mg / L - 15mg / L.

[0010] As one of the preferred technical solutions, in this application, the average value of ammonia nitrogen in the effluent of the aerobic sequencing batch reactor is below 15mg / L.

[0011] Compared with the prior art, the beneficial effects of this application are:

[0012] By adding a certain concentration of cephalexin in the sequencing batch reactor (SBR), this application solves the bottleneck problems of slow start - up speed and instability in short - cut nitrification of the sequencing batch process. It also has the advantages of high denitrification efficiency, fast reaction rate, cost savings in operation, and obtaining excellent effluent quality, maintaining the rapid realization and stable maintenance of short - cut nitrification in the sequencing batch reactor, which helps in the treatment of urban domestic sewage. Brief Description of the Drawings

[0013] Figure 1 It is a curve graph showing the change relationship of the denitrification performance of the nitrification system with time for different concentrations of cephalexin in this application.

[0014] Figure 2 It is a curve graph showing the change of the nitrite accumulation rate of the nitrification system with time for different concentrations of cephalexin in this application. Detailed Embodiments

[0015] The following further describes and explains the technical solutions described in this application in combination with the drawings and embodiments.

[0016] As a β-lactam antibiotic, cephalexin mainly inhibits the cross-linking between linear peptidoglycan polymer chains and binds to penicillin-binding proteins through the β-lactam ring, thereby inhibiting cell wall synthesis, changing cell membrane permeability, and inhibiting bacterial protein synthesis, resulting in cell rupture and death. An appropriate antibiotic concentration can improve the removal efficiency of bacteria on pollutants. Cephalexin has different inhibitory degrees on AOB and NOB. Among them, AOB has stronger tolerance to cephalexin and can degrade cephalexin in the presence of ammonia. In this application, although cephalexin has inhibitory effects on both AOB and NOB in the nitrifying bacteria, the inhibitory degree on NOB is higher. With the continuous addition of cephalexin in urban sewage, the nitrogen removal performance of the nitrification system gradually decreases. However, with the continuous progress of the shortcut nitrification reaction, the activity of AOB in the nitrifying bacteria will gradually recover, and the activity of NOB will be completely inhibited, thereby realizing the elutriation of NOB in the nitrifying bacteria and the screening of dominant AOB strains, optimizing the microbial species population.

[0017] Example 1

[0018] A method for realizing shortcut nitrification and denitrification with a cephalexin inhibitor. Mark the aerobic sequencing batch reactor as R1. The pH value in the aerobic sequencing batch reactor is the same as or close to the pH value of the actual urban domestic sewage to be treated, both controlled between 7.4 and 8.0. The sludge concentration 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 at room temperature.

[0019] Under the above conditions, add 5 mg / L of cephalexin to the aerobic sequencing batch reactor once a day, monitor the three-nitrogen in the effluent of the aerobic sequencing batch reactor, and the operation cycle is 35 days. And record the experimental results.

[0020] Example 2

[0021] A method for realizing shortcut nitrification and denitrification with a cephalexin inhibitor. Mark the aerobic sequencing batch reactor as R2. The pH value in the aerobic sequencing batch reactor is the same as or close to the pH value of the actual urban domestic sewage to be treated, both controlled between 7.4 and 8.0. The sludge concentration 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 at room temperature.

[0022] Under the above conditions, add 10 mg / L of cephalexin to the aerobic sequencing batch reactor once a day, monitor the three-nitrogen in the effluent of the aerobic sequencing batch reactor, and keep the same operation cycle as in Example 1. And record the experimental results.

[0023] Example 3

[0024] A method for realizing short - cut nitrification and denitrification by a cephalexin inhibitor. Mark the aerobic sequencing batch reactor as R3. The pH value in the aerobic sequencing batch reactor is the same as or close to the pH value of the actual domestic sewage to be treated, and both 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 at room temperature.

[0025] Under the above conditions, add 15 mg / L of cephalexin to the aerobic sequencing batch reactor once a day. Monitor the three - nitrogen in the effluent of the aerobic sequencing batch reactor, and maintain the same operation cycle as in Example 1. And record the experimental results.

[0026] Control Example

[0027] Mark the aerobic sequencing batch reactor as R4. The pH value in the aerobic sequencing batch reactor is the same as or close to the pH value of the actual domestic sewage to be treated, and both 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 at room temperature.

[0028] Under the above conditions, add 20 mg / L of cephalexin to the aerobic sequencing batch reactor once a day. Monitor the three - nitrogen in the effluent of the aerobic sequencing batch reactor, and maintain the same operation cycle as in Example 1 (because the aerobic sequencing batch reactor R4 will completely lose its denitrification performance on the 25th day due to the excessive concentration of cephalexin at this concentration, so the data statistics of the aerobic sequencing batch reactor R4 are up to the 25th day, and the data from the 26th day to the 30th day are the same as those on the 25th day). And record the experimental results.

[0029] From Figure 1 The recorded experimental results show that in the early stage of adding cephalexin to the aerobic sequencing batch reactors R1 to R4, different concentrations of cephalexin have a certain impact on the removal effect of ammonia nitrogen. However, as the operation cycle increases, the system with a lower concentration of cephalexin added gradually recovers its ammonia - nitrogen removal effect. From the data of stable operation after adding cephalexin, the average value of ammonia nitrogen in the effluent of the aerobic sequencing batch reactors R1, R2, and R3 is below 15 mg / L, while the aerobic sequencing batch reactor R4 completely loses its denitrification performance due to the large concentration of cephalexin.

[0030] From Figure 2As can be seen from the recorded content, as the concentration of cephalexin increases, the time to initiate short-cut nitrification becomes shorter. Especially in aerobic sequencing batch reactor R2 and aerobic sequencing batch reactor R3, the average nitrite accumulation rates in them reach over 90% on the 8th day and the 18th day respectively.

[0031] Finally, although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

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

2. A method for realizing short-cut nitrification and denitrification by a cephalexin inhibitor according to claim 1, characterized in that: The amount of cephalexin added per day in the aerobic sequencing batch reactor is 10 mg / L - 15 mg / L.

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

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