Biological sewage treatment method for improving nitrification performance at low temperature

Abstract

The invention provides a biological sewage treatment method for improving nitrification performance at low temperature, and belongs to the technical field of sewage treatment. The biological sewage treatment method comprises the following steps: under the condition that the temperature is less than or equal to 12 DEG C, sequentially carrying out start-up stage treatment and maturation stage treatment; in the treatment at the starting stage, N-butyryl-L-homoserine lactone is added into a system to be treated once in each operation cycle; in the maturing stage treatment, when the concentration of NH4 < + >-N in influent water is smaller than or equal to 80 mg / L, N-butyryl-L-homoserine lactone is stopped from being continuously added, and when the concentration of NH4 < + >-N in influent water is larger than 80 mg / L, N-butyryl-L-homoserine lactone is added into the to-be-treated system once every 1-3 operation cycles. According to the method, N-butyryl-L-homoserine lactone signal molecules are added to improve the nitrification performance of a biological treatment system, different adding modes are adopted according to different concentrations of NH4 < + >-N in inflow, and the method has a good biological treatment effect and economical efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a sewage biological treatment method for improving nitrification performance at low temperature. Background Art

[0002] Biological sewage treatment technology has been widely used in urban and rural domestic sewage treatment due to its advantages of high removal efficiency, low operating cost and convenient operation and management. Temperature is one of the important factors affecting the activity of microorganisms and the treatment effect in the biological sewage treatment process. Low temperature will reduce the activity of microorganisms (especially nitrifying bacteria), resulting in insufficient nitrification capacity of the biological treatment system, and ultimately affecting the denitrification efficiency. The average temperature in northern cities in my country is 5-8℃. The NH 4 + -N removal efficiency is lower than the national level. In addition, according to the operation of 20 municipal sewage treatment plants in Northeast China from 2011 to 2018, NH 4 + -N frequently exceeds the discharge limit in winter, and the effluent total nitrogen increases with NH 4 + -N fluctuations, indicating that the nitrification process is sensitive to low temperature.

[0003] At present, the technical solutions for improving the nitrification performance of biological treatment systems under low temperatures mainly include the modification of treatment equipment and the inoculation of low-temperature-resistant functional bacteria for bio-enhancement. On the one hand, the cost of modifying the equipment of existing sewage treatment plants is high and the operation is inconvenient; on the other hand, the screening process of low-temperature-resistant functional bacteria is complicated and difficult, the acclimatization time is long, and the inoculated bacteria may compete with the local bacteria in the reactor. These shortcomings reduce its practical application value. Summary of the invention

[0004] The purpose of the present application is to provide a method for biological treatment of sewage to improve nitrification performance at low temperature, which utilizes exogenous N-butyryl-L-homoserine lactone (C4-HSL) signal molecules to improve the nitrification performance of the biological treatment system, which can reduce costs compared with the method of modifying sewage treatment plant equipment and can operate faster than the method of inoculating functional bacteria; moreover, C4-HSL signal molecules have lower costs than other N-acyl homoserine lactone (AHLs) signal molecules, and can be used for different influent NH 4 + -N concentration adopts different signal molecule addition methods, which has better biological treatment effect and economy.

[0005] The embodiment of the present application is implemented as follows:

[0006] The embodiment of the present application provides a wastewater biological treatment method for improving nitrification performance at low temperature, comprising: performing a start-up stage treatment and a mature stage treatment in sequence under a temperature condition of ≤12°C;

[0007] During the start-up phase of treatment, N-butyryl-L-homoserine lactone is added to the system to be treated once per operation cycle;

[0008] In the mature stage treatment, when the influent NH 4 + When the concentration of N-butyryl-L-homoserine lactone is ≤80 mg / L, stop adding N-butyryl-L-homoserine lactone. 4 + When the -N concentration is greater than 80 mg / L, N-butyryl-L-homoserine lactone is added to the system to be treated once every 1 to 3 operation cycles.

[0009] The sewage biological treatment method for improving nitrification performance at low temperature provided in the embodiment of the present application has at least the following beneficial effects:

[0010] 1. Using exogenous C4-HSL signal molecules to improve the nitrification performance of the biological treatment system can reduce costs compared to the method of modifying sewage treatment plant equipment and can operate faster than the method of inoculating functional bacteria.

[0011] 2. Currently, most long-chain mixed AHLs signal molecules are used to achieve rapid startup and treatment effects of bioreactors under low temperatures. However, this type of AHLs signal molecules has the disadvantages of poor water solubility, must be stored at -20°C, and are expensive. In contrast, the C4-HSL signal molecule used in this application is easier to store, has lower raw material costs, is easier to dissolve and operate, and has higher practical application value and economy.

[0012] 3. The current technical solution for adding signal molecules is continuous addition, which further increases the application cost. In the technical solution of this application, in the mature stage, according to the influent NH 4 + Different signal molecule addition methods are used for different -N concentrations. In some cases, the addition of signal molecules can be stopped or added at appropriate intervals, which is beneficial to further reduce the cost of signal molecules and has better economy.

[0013] 4. In the technical solution of the present application, signal molecules are continuously added in the startup phase to optimize the community structure of microorganisms in the biological treatment system, enhance the interspecies cooperation of functional bacteria, and improve the nitrification performance of the biological treatment system at low temperatures; moreover, this effect is long-term and 4 +When the -N concentration is lower than 80 mg / L, stopping the addition of signal molecules can still maintain good nitrification performance.

[0014] 5. In the technical solution of this application, in the mature stage, according to the influent NH 4 + Different signal molecule addition methods for different -N concentrations can better regulate the abundance of nitrifying bacteria, microbial functional enzyme activity, quorum sensing genes, and energy metabolism-related gene abundance in the biological treatment system, so that different influent NH 4 + -N concentration has good low-temperature nitrification performance.

[0015] In some embodiments, the temperature condition is ≤9°C; optionally, the temperature condition is 6±1°C.

[0016] In some embodiments, a fixed biofilm activated sludge process is used for wastewater treatment.

[0017] In some embodiments, each operation cycle satisfies one or more of the following conditions (a) to (d);

[0018] (a) The carrier filling rate of the reactor is 20 to 40%;

[0019] (b) Sludge concentration is 1500±500mg / L;

[0020] (c) duration is 8 ± 4 h;

[0021] (d) The drainage ratio is 50±5%.

[0022] In some embodiments, during the start-up phase of the treatment, the influent NH 4 + -N concentration ≤ 40 mg / L and / or the number of operating cycles is 40 to 80.

[0023] In some embodiments, the start-up phase treatment is completed until biofilm is visibly attached to the carrier.

[0024] In some embodiments, during the start-up phase of treatment, each time N-butyryl-L-homoserine lactone is added, the concentration of N-butyryl-L-homoserine lactone added to the system to be treated is 20-100 μg / L.

[0025] In some embodiments, during the mature stage treatment, when the influent NH 4 + When the -N concentration is greater than 80 mg / L, N-butyryl-L-homoserine lactone is added to the system to be treated once every 2 to 3 operation cycles.

[0026] In some embodiments, in the ripening stage treatment, each time N-butyryl-L-homoserine lactone is added, the concentration of N-butyryl-L-homoserine lactone added to the system to be treated is 20-40 μg / L.

[0027] In some embodiments, in the start-up stage treatment and the mature stage treatment, each time N-butyryl-L-homoserine lactone is added, the addition concentration of N-butyryl-L-homoserine lactone in the system to be treated is the same. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] It should be noted that “and / or” in this application, such as “Feature 1 and / or Feature 2”, refers to the three situations of “Feature 1” alone, “Feature 2” alone, or “Feature 1” plus “Feature 2”.

[0030] In addition, in the description of the present application, unless otherwise specified, the meaning of "multiple" in "one or more" refers to two or more; the range of "value a ~ value b" includes the two end values ​​"a" and "b", and the "unit" in "value a ~ value b + unit of measurement" represents the "unit of measurement" of both "value a" and "value b".

[0031] The technical solutions of the embodiments of the present application are exemplarily described below.

[0032] The embodiment of the present application provides a wastewater biological treatment method for improving nitrification performance at low temperature, comprising: performing a start-up phase treatment and a mature phase treatment in sequence under a temperature condition of ≤12°C.

[0033] During the start-up phase of treatment, N-butyryl-L-homoserine lactone is added to the system to be treated once in each operation cycle.

[0034] In the mature stage treatment, when the influent NH 4 + When the concentration of N-butyryl-L-homoserine lactone is ≤80 mg / L, stop adding N-butyryl-L-homoserine lactone. 4 + When the -N concentration is greater than 80 mg / L, N-butyryl-L-homoserine lactone is added to the system to be treated once every 1 to 3 operation cycles.

[0035] It should be noted that in the embodiments of the present application, the method of biological treatment of sewage is not limited, for example, but not limited to one of the broad activated sludge method and the biofilm method. As an example, the fixed biofilm activated sludge process (IFAS) is used for sewage treatment. The IFAS technology is a mud-film composite system that has the advantages of both the activated sludge method and the biofilm method.

[0036] Specifically, the essence of IFAS technology is to add biological carriers to the activated sludge, thus forming a composite treatment system that includes both fixed biofilm and suspended activated sludge, giving full play to the advantages of the two microbial forms and ultimately achieving the goal of efficient removal of pollutants; among them, the introduction of biological carriers greatly increases the biomass in the system, and under the condition of unchanged influent load, the sludge load rate of the system decreases and the sludge age increases, which is conducive to the growth of nitrifying bacteria on the carrier and ensures good nitrification performance; in addition, the biological carrier can also firmly fix the filamentous bacteria on its surface, which can not only avoid system damage caused by sludge swelling and improve the system's operating stability, but also give full play to the powerful purification ability of filamentous bacteria to pollutants and enhance the system's treatment efficiency.

[0037] In general, the IFAS process takes a long time to start up, especially in a low temperature environment. The biofilm formed at low temperatures is not stable and easy to fall off, resulting in a higher content of suspended solids in the effluent. Studies have found that the sudden increase in the amount of biofilm during the startup of the IFAS process is caused by the quorum sensing (QS) of microorganisms. Therefore, regulating the QS between bacterial communities may accelerate the attachment rate of bacteria on the carrier surface. QS is a cell-to-cell information transmission mechanism that releases signal molecules to the outside world, activates downstream target genes, and then regulates bacterial physiological behavior. In the implementation scheme of the present application, C4-HSL signal molecules are used to intervene in the quorum sensing phenomenon between microorganisms, optimize the community structure of microorganisms in the system, stimulate the quorum sensing phenomenon, and combine the IFAS process to better provide an economical and efficient biological treatment technology for low-temperature domestic sewage.

[0038] In the embodiments of the present application, the temperature condition is, for example but not limited to, any one of 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, and 12°C, or a range of any two thereof. Studies have shown that when biological treatment of sewage is carried out under the above temperature conditions, good nitrification performance is achieved.

[0039] As an example, the temperature condition is ≤9°C, optionally, 4°C≤temperature condition≤9°C, further optionally, the temperature condition is 6±1°C, which is close to the average water temperature in winter and can better achieve application conversion.

[0040] It can be understood that, in the embodiments of the present application, an operation cycle refers to a circulating treatment unit during biological treatment of sewage, which includes operations such as but not limited to water intake, aeration, settling, drainage, etc.

[0041] In some embodiments, each operation cycle satisfies one or more of the following conditions (a) to (d); (a) the carrier filling rate of the reactor is 20-40%; (b) the sludge concentration is 1500±500 mg / L; (c) the duration is 8±4 h; (d) the drainage ratio is 50±5%.

[0042] Exemplarily, the carrier filling rate of the reactor is 30%.

[0043] Exemplarily, the sludge concentration is 1500 mg / L.

[0044] As an example, based on the fixed biofilm activated sludge process, each operation cycle includes water intake, aeration, static sedimentation and drainage in sequence, and the water intake of the next operation cycle is carried out after the drainage of the previous operation cycle is completed. Among them, the operation of adding C4-HSL signal molecules is carried out following the water intake during the water intake stage.

[0045] Exemplarily, the duration of the water intake phase is 5 minutes, the duration of the aeration phase is 6 hours, the duration of the settling phase is 1.5 hours, and the duration of the drainage phase is 25 minutes.

[0046] Exemplarily, the drainage ratio is 50%.

[0047] It should be noted that, in the present application, regarding the addition of signal molecules, continuous addition means that the addition is carried out following the water inlet stage in each operating cycle, and does not mean that the addition action is continuous at all times. Correspondingly, intermittent addition means that there is an operating cycle without addition between two addition operations.

[0048] Regarding the start-up phase treatment, C4-HSL signal molecules are added to the system to be treated once in each operation cycle, that is, C4-HSL signal molecules are continuously added during the start-up phase treatment.

[0049] Regarding the treatment of the mature stage, when the influent NH 4 + -When the N concentration is greater than 80 mg / L, C4-HSL signal molecules can be added to the system to be treated once per operation cycle, that is, the continuous addition of C4-HSL signal molecules is maintained; C4-HSL signal molecules can also be added to the system to be treated once per 2 or 3 operation cycles, that is, the intermittent addition of C4-HSL signal molecules is adjusted.

[0050] It should be noted that in the embodiments of the present application, the start-up phase treatment is terminated by the maturity of the system operation, and then the maturity phase treatment is performed. The maturity of the system operation is, for example, but not limited to, the stable pollutant removal effect, strong shock load resistance, and obvious biofilm attached to the carrier as indicators.

[0051] In some embodiments, during the startup phase processing, the number of operating cycles is 40-80, and the number of cycles is, for example but not limited to, any one of 40, 45, 50, 55, 60, 65, 70, 75, 80 or a range between any two of them.

[0052] Taking the fixed biofilm activated sludge process as an example, in the start-up phase, the carrier in the reactor was not biofilmed at the beginning; after 40 operation cycles, the biofilm was obviously attached to the carrier, and the removal rate of pollutants also tended to be stable; in the 41st to 80th operation cycles, the influent COD and NH 4 + -N concentration was used to test the reactor's ability to resist shock loads. It was found that the reactor with a certain concentration of C4-HSL had strong resistance to shock loads, fast biofilm attachment speed and good nitrification performance.

[0053] In some embodiments, during the start-up phase of the treatment, the influent NH 4 + -N concentration ≤ 40 mg / L, for example but not limited to any one of 20 mg / L, 25 mg / L, 30 mg / L, 35 mg / L, 40 mg / L or a range between any two of them.

[0054] As an example, based on the fixed biofilm activated sludge process, the start-up phase is treated until the biofilm is obviously attached to the carrier.

[0055] Regarding the start-up phase treatment, optionally, each time N-butyryl-L-homoserine lactone is added, the concentration of N-butyryl-L-homoserine lactone in the system to be treated is 20-100 μg / L, for example but not limited to any one of 20 μg / L, 30 μg / L, 40 μg / L, 50 μg / L, 60 μg / L, 70 μg / L, 80 μg / L, 90 μg / L, 100 μg / L or a range between any two of them, which is conducive to the rapid attachment of the biofilm and can better improve the nitrification performance of the system.

[0056] Regarding the mature stage treatment, for example, when the influent NH 4 +When the -N concentration is greater than 80 mg / L, N-butyryl-L-homoserine lactone is added to the system to be treated once every 2 to 3 operating cycles. The intermittent addition of C4-HSL signal molecules is beneficial to further reduce the cost of signal molecules and has better economy.

[0057] Optionally, in the mature stage treatment, each time N-butyryl-L-homoserine lactone is added, the concentration of N-butyryl-L-homoserine lactone in the system to be treated is 20-40 μg / L, for example but not limited to any one of 20 μg / L, 30 μg / L, 40 μg / L or any range between the two. 4 + When the -N concentration is greater than 80 mg / L, adding C4-HSL signal molecules according to the above standards can better maintain the nitrification performance of the system.

[0058] Exemplarily, in the start-up phase treatment and the mature phase treatment, each time N-butyryl-L-homoserine lactone is added, the concentration of N-butyryl-L-homoserine lactone in the system to be treated is the same, for example, 20 μg / L. Based on this technical solution, the same C4-HSL stock solution can be prepared and used in the entire process, and only the addition interval of C4-HSL needs to be adjusted, which makes the operation simpler.

[0059] The features and performance of the present application are further described in detail below in conjunction with specific experimental examples.

[0060] 1. Experimental Preparation

[0061] Biological treatment system: The IFAS process is adopted. The effective volume of the IFAS reactor is 2L, the carrier filling rate of the reactor is 30%, and the sludge concentration is 1500mg / L.

[0062] Influent composition: C 6 H 12 O 6 0.2812g / L (COD 300mg / L), NH 4 Cl0.1527~0.3817g / L (NH 4 + -N40~100mg / L, adjusted according to the experimental conditions), KH 2 PO 4 0.0132 g / L (TP3 mg / L), NaHCO 3 0.2~0.9g / L (adjusted according to pH value), pH value maintained at 7~8, trace element stock solution 2mL / L.

[0063] Trace element stock solution: EDTA 0.38 mg / L, MgSO 4 7H 2 O0.4mg / L,CaCl 2 3.6mg / L,FeSO 4 7H 2 O0.56mg / L,MnCl 2 ·4H 2 O1.25mg / L,ZnSO 4 7H 2 O0.55mg / L,CoCl 2 ·H 2 O0.016mg / L,H 3 BO 3 0.006mg / L,CuSO 4 ·5H 2 O0.4mg / L,Na 2 MoO 4 ·2H 2 O0.5mg / L.

[0064] C4-HSL stock solution: C4-HSL 10 mg / L.

[0065] 2. Experimental Operation

[0066] The reactor was placed in a constant temperature box at 6±1°C and cultured according to each operation cycle of 8h (5min of water inlet, 6h of aeration, 1.5h of static sedimentation, 25min of drainage) and a drainage ratio of 50%. The culture process was as follows, wherein the addition of C4-HSL followed the water inlet.

[0067] Start-up phase: In each operation cycle, each experimental group added C4-HSL according to different concentration standards until 80 operation cycles were cultivated.

[0068] Mature stage: Each experimental group added C4-HSL according to different addition frequency standards and different addition concentration standards.

[0069] C4-HSL dosing conditions and influent NH in each experimental group at the start-up and mature stages 4 + -N concentration conditions are shown in Table 1.

[0070] Table 1. C4-HSL dosing conditions and NH 4 + -N concentration conditions

[0071]

[0072] It should be noted that in each experimental group, different experiments started with the same startup phase, and the influent NH4 + -N concentration is 35mg / L; different maturity stages are based on the influent NH 4 + -N concentration from low to high. Specifically, after completing the startup phase, first follow the influent NH 4 + -N concentration was 40 mg / L and the operation was continued for 62 cycles (taking experimental group 1 as an example, this corresponds to experimental group 1-1), and then the influent NH 4 + -N concentration was increased to 60 mg / L and run for 60 cycles (taking experimental group 1 as an example, this corresponds to experimental group 1-2), and then the influent NH 4 + -N concentration was increased to 80 mg / L and run for 120 cycles (taking experimental group 1 as an example, this corresponds to experimental groups 1-3), and then the influent NH 4 + The -N concentration was increased to 100 mg / L and the operation was continued (taking experimental group 1 as an example, this corresponds to experimental groups 1-4).

[0073] 3. Experimental Results

[0074] 1. In the mature stage, the effluent from the reactor is collected to test the pollutant removal effect.

[0075] It was found that in the mature stage, all experimental groups did not need an adaptation period, and the COD concentration of the reactor effluent could be reduced to below 50 mg / L, and the removal rate was always maintained at around 90%.

[0076] The nitrification performance of each experimental group was statistically analyzed, and the results are shown in Table 2.

[0077] Table 2. Nitrification performance

[0078]

[0079]

[0080]

[0081] It should be noted that the average effluent concentration or average removal rate in the test results refers to: 4 + After the removal effect of -N is stable, the average value of the test results of all cycles; NH 4 + For example, the experimental group in which the -N concentration was stabilized at 8 mg / L was 4 + -N The effluent concentration is stable below 8 mg / L and is the average value of the test results for all cycles.

[0082] In addition, NH 4 Cl was used as nitrogen source to simulate domestic sewage, NH 4 The amount of Cl is based on the NH 4 + -N concentration calculation, but there is a weighing error in the preparation process. 4 + -N removal rate results are based on the actual measured NH 4 + -N concentration is calculated based on the inlet concentration and outlet concentration. Since there is a slight deviation between the actual inlet concentration and the theoretical value, the NH 4 + Compared with the NH-N removal rate calculated based on the measured influent concentration in Table 2, 4 + There may be slight deviations in -N removal rates.

[0083] 2. In the mature stage, after the treatment effect is stabilized, high-throughput sequencing is performed on the sludge and biofilm, and the test results are shown in Tables 3 to 5.

[0084] Table 3. Microbial communities

[0085]

[0086]

[0087] Table 4. Microbial functional enzyme activities

[0088]

[0089]

[0090]

[0091]

[0092] Table 5. Metagenomic analysis

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] The analysis based on Tables 1 to 5 is as follows:

[0101] Comparing experimental group 1 with experimental group 3, it can be seen that in experimental group 1, C4-HSL was added in each operation cycle during the startup phase, and C4-HSL was stopped during the mature phase. 4 + When -N concentration was ≤80mg / L, the abundance of typical nitrifying bacteria such as Ellin6067, Nitrosomonas and CandidatusNitrotoga in the reactor increased, the activities of AMO, HAO, NXR enzymes involved in nitrification and ATPase characterizing microbial activity were enhanced, and the abundance of sucAB and sucCD genes involved in TCA cycle and autoinducer_producer, autoinducer, autoinducer_receptor, effector, activator and other genes related to quorum sensing were also increased. 4 + -N effluent concentration can be quickly stabilized below 8 mg / L, with good nitrification performance; when the influent NH 4 + When the -N concentration is greater than 80 mg / L, the AMO enzyme activity of both the mud membrane phases of the system is inhibited, thus affecting its NH 4 + -N removal effect, NH 4 + -N removal rate will gradually decrease. By re-dosing C4-HSL at a higher frequency, the abundance of functional bacteria and functional genes in the mud film two phases is increased, the activity of functional enzymes is improved, and the nitrification performance of the reactor is better restored.

[0102] Comparing experimental group 2 with experimental group 3, it can be seen that in experimental group 2, C4-HSL was added for cultivation in each operation cycle during the startup stage, and C4-HSL was continued to be added every 2 operation cycles during the mature stage. The abundance of typical nitrifying bacteria such as Ellin6067, Nitrosomonas and CandidatusNitrotoga in the reactor increased, and the activities of AMO, HAO, NXR enzymes involved in nitrification and ATPase characterizing microbial activity were enhanced. The abundance of CS, acnAB, idh123, sucAB, sucCD, sdhABCD and fumABC genes involved in TCA cycle and autoinducer_producer, autoinducer, autoinducer_receptor, effector, activator, regulator, transporter, decompose and other genes related to quorum sensing were also increased. 4 + -N concentration, NH 4 + -N effluent concentration can be quickly stabilized below 8 mg / L. 4 + When the -N concentration is >80mg / L, NH 4 + -N effluent concentration is stable below 8 mg / L, with good nitrification performance.

[0103] In experimental group 3, without adding C4-HSL, the abundance of functional bacteria and functional genes in the IFAS reactor was low, and the activity of functional enzymes was weak. 4 + When the -N concentration is 40 mg / L, the sewage cannot meet the discharge standard under low temperature conditions; as the operation time increases, the reactor without C4-HSL is gradually adapting to the low temperature environment. 4 + When the -N concentration increases to 60-100 mg / L, a longer adaptation period is required to convert NH 4 + The -N effluent concentration is stable below 8 mg / L, and the nitrification performance is poor.

[0104] Comparing experimental group 4 with experimental group 2, it can be seen that in experimental group 4, C4-HSL was added at a lower frequency and longer dosing intervals during the mature stage. 4 + When the -N concentration is higher than 40 mg / L, the intermittent addition of C4-HSL will affect the quorum sensing effect, inhibit the activity of functional bacteria and functional enzymes, and reduce the abundance of functional genes, resulting in poor nitrification performance.

[0105] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A method for biological treatment of sewage for improving nitrification performance at low temperature, characterized in that: include: At a temperature of ≤12°C, the start-up stage treatment and the mature stage treatment were carried out in sequence; In the start-up phase treatment, N-butyryl-L-homoserine lactone is added to the system to be treated once in each operation cycle; In the mature stage treatment, when the influent NH4 + -N concentration ≤ 80mg / L, stop adding the N-butyryl-L-homoserine lactone, when the influent NH4 + When the -N concentration is greater than 80 mg / L, the N-butyryl-L-homoserine lactone is added to the system to be treated once every 1 to 3 operation cycles.

2. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 1, characterized in that: The temperature condition is ≤9°C; optionally, the temperature condition is 6±1°C.

3. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 1, characterized in that: The fixed biofilm activated sludge process is used for wastewater treatment.

4. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 3, characterized in that: Each of the operating cycles satisfies one or more of the following conditions (a) to (d); (a) The carrier filling rate of the reactor is 20 to 40%; (b) Sludge concentration is 1500±500mg / L; (c) duration is 8 ± 4 h; (d) The drainage ratio is 50±5%.

5. The method for biological treatment of sewage for improving nitrification performance at low temperature according to any one of claims 1 to 4, characterized in that: During the startup phase, the influent NH4 + -N concentration ≤ 40 mg / L and / or the number of cycles of the operation cycle is 40 to 80.

6. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 5, characterized in that: The start-up phase treatment ends when biofilm is visibly attached to the carrier.

7. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 5, characterized in that: In the treatment at the start-up stage, each time the N-butyryl-L-homoserine lactone is added, the concentration of the N-butyryl-L-homoserine lactone added to the system to be treated is 20-100 μg / L.

8. The method for biological treatment of sewage for improving nitrification performance at low temperature according to any one of claims 1 to 4, characterized in that: In the mature stage treatment, when the influent NH4 + When the -N concentration is greater than 80 mg / L, the N-butyryl-L-homoserine lactone is added to the system to be treated once every 2 to 3 operation cycles.

9. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 8, characterized in that: In the mature stage treatment, each time the N-butyryl-L-homoserine lactone is added, the concentration of the N-butyryl-L-homoserine lactone added to the system to be treated is 20-40 μg / L.

10. The method for biological treatment of sewage for improving nitrification performance at low temperature according to claim 9, characterized in that: In the start-up stage treatment and the mature stage treatment, each time the N-butyryl-L-homoserine lactone is added, the addition concentration of the N-butyryl-L-homoserine lactone in the system to be treated is the same.

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