Process for improving denitrification performance of activated sludge method at low temperature

Abstract

The application discloses a treatment method for improving denitrification performance of an activated sludge method at low temperature, and belongs to the technical field of sewage treatment. The treatment method comprises the following steps: adding N-butyryl-homoserine lactone into a to-be-treated system when water temperature of the to-be-treated system is less than or equal to 12 DEG C. When the to-be-treated system is at low temperature, the treatment method can effectively improve the denitrification performance of the activated sludge method at low temperature by adding a C4-HSL signal molecule to intervene in the quorum sensing phenomenon among microorganisms in the to-be-treated system. In the case of effectively improving the denitrification effect, the treatment method can also reduce sludge concentration and the amount of residual sludge, thereby reducing sludge treatment cost. The treatment method can be quickly started and take effect, and can meet the emergency treatment demand of sudden temperature drop. Moreover, the treatment method has low time cost, low equipment cost and low raw material cost, and is simple to operate, and has high practical application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a treatment method for improving the denitrification performance of activated sludge method at low temperature. BACKGROUND

[0002] The method of sewage treatment currently mainly has physical method, chemical method and biological method, wherein the biological method is widely applied in domestic sewage treatment process due to its low operation cost, high removal efficiency, convenient operation and the like.

[0003] The activated sludge method is the most widely used sewage biological treatment method. Among them, temperature is a key factor affecting the treatment effect of the activated sludge system. The winter operation results of many sewage treatment plants in cold regions show that with the decrease of water temperature, the activated sludge settling property becomes poor, the organic matter removal and nitrification / denitrification are greatly impacted, the removal rates of ammonia nitrogen and total nitrogen are reduced, and the effluent water quality is directly affected; in some cases, the denitrification efficiency at low temperature (about 10℃) is reduced by about 80% compared with that at suitable temperature (about 30℃).

[0004] In order to eliminate the influence of low temperature on the denitrification treatment efficiency of the activated sludge method, the measures such as heat preservation or temperature rise, modification of treatment equipment, and addition of low-temperature bacterial agent are generally taken to ensure that the nitrogen content of the effluent of sewage treatment meets the standard in winter. However, the construction and operation cost of these measures such as heat preservation or temperature rise and modification of treatment equipment is relatively high; the screening process of low-temperature functional bacteria is complex and difficult, the domestication time is long, the inoculated bacterial agent may compete with the indigenous bacteria in the reactor, and there is a problem of bacterial loss affecting the denitrification effect. In addition, the above measures need a long time from preparation to effect, and need to be prepared in advance, but there are sudden temperature drop in winter in some places, which easily leads to untimely response of the measures. Therefore, an economical and efficient emergency treatment method is needed to improve the problem of increased nitrogen content and decreased water quality of domestic sewage effluent in winter in cold regions. SUMMARY

[0005] Quorum sensing (QS) is a method of intercellular communication, which regulates bacterial gene expression and physiological behavior through signal molecule exchange. Many gram-negative bacteria can produce a QS signal molecule, i.e. N-acyl-homoserine lactone (full name N-acyl-homoserine Lactones, abbreviated as AHLs). In some studies, it is found that some long-chain exogenous AHLs [such as N-hexanoyl-L-homoserine lactone (molecular formula C 10 H 17 NO3, abbreviated as C6-HSL), N-octanoyl-L-homoserine lactone C8-HSL (molecular formula C 12 H 21N-Butyryl-L-homoserine lactone (molecular formula C8H13NO3, abbreviated as C8-HSL), N-Dodecanoyl-L-homoserine lactone (molecular formula C 16 H 29 NO3, abbreviated as C12-HSL) can increase the abundance of nitrifying bacteria at normal temperature, and can improve the denitrification performance of the activated sludge system at normal temperature; while short-chain exogenous AHLs [such as N-hexanoyl-L-homoserine lactone (molecular formula C8H 13 NO3, abbreviated as C4-HSL)] do not show the effect of increasing the abundance of nitrifying bacteria at normal temperature and improving the denitrification performance of the activated sludge system. Therefore, the long-chain AHLs are mainly studied at present. However, the current research is carried out at normal temperature, and the effect of exogenous AHLs on the denitrification efficiency of the activated sludge system at low temperature is still unclear.

[0006] The applicant notes that long-chain AHLs (such as C6-HSL, C8-HSL, C12-HSL) have high cost and need to be stored at a low temperature of about -20°C, thus limiting their application in engineering.

[0007] Moreover, it is found through research that the solubility of long-chain AHLs such as C6-HSL, C8-HSL, and C12-HSL at low temperature is poor, and a series of operations are needed to help dissolve before adding, which is complex and costly in early preparation operation. Therefore, long-chain AHLs are more difficult to implement in the engineering application of denitrification of the activated sludge system at low temperature.

[0008] C4-HSL, as a short-chain signal molecule, can be stored at normal temperature; compared with other long-chain AHLs, it is inexpensive, which provides important significance for the application of exogenous AHLs in practice.

[0009] It is found through further research that C4-HSL is easily soluble at low temperature; moreover, although C4-HSL has no effective effect on increasing the abundance of nitrifying bacteria and improving the denitrification performance of the activated sludge system at normal temperature, it unexpectedly can well increase the abundance of nitrifying bacteria and improve the denitrification performance of the activated sludge system at low temperature, and its low-temperature denitrification improvement effect can even reach or be higher than that of long-chain AHLs, which provides important significance for the application of exogenous AHLs in improving the denitrification performance of the activated sludge method at low temperature.

[0010] Based on the above research findings, the purpose of the present application is to provide a treatment method for improving the denitrification performance of the activated sludge method at low temperatures. When the system to be treated is at low temperature, the addition of C4-HSL signal molecules can effectively improve the denitrification performance of the activated sludge method at low temperatures by interfering with the quorum sensing phenomenon among microorganisms in the system to be treated. This method can effectively improve the denitrification effect, reduce the sludge concentration, reduce the amount of residual sludge, and thus reduce the sludge treatment cost. This method can quickly start and take effect, and can meet the emergency treatment needs of sudden temperature drop. Moreover, this method has low time cost, equipment cost and raw material cost, and is simple to operate, and has high practical application value.

[0011] The embodiments of the present application are implemented as follows:

[0012] The embodiments of the present application provide a treatment method for improving the denitrification performance of the activated sludge method at low temperatures, comprising: adding N-butyryl-homoserine lactone to the system to be treated when the water temperature in the system to be treated is ≤12℃.

[0013] The treatment method provided by the embodiments of the present application adds N-butyryl-homoserine lactone to the system to be treated when the system to be treated is at low temperature with water temperature ≤12℃, and at least has the following beneficial effects:

[0014] 1. By adding C4-HSL signal molecules to interfere with the quorum sensing phenomenon among microorganisms, the microbial community structure in the system is optimized, the quorum sensing phenomenon is stimulated, the interspecific cooperation of functional bacteria is enhanced, the efficient removal of pollutants is realized, and the abundance of nitrifying bacteria and the denitrification performance of the activated sludge system can be effectively improved.

[0015] 2. In addition to effectively improving the denitrification effect, the sludge concentration can also be reduced, the amount of residual sludge can be reduced, and thus the sludge treatment cost can be reduced.

[0016] 3. Compared with measures such as heat preservation or temperature rise, modification of treatment equipment, and addition of low-temperature bacterial agents, the addition of signal molecules can quickly start and take effect, and can meet the emergency treatment needs of sudden temperature drop. Moreover, the time and equipment cost are lower.

[0017] 4. Compared with common long-chain AHLs signal molecules, the C4-HSL signal molecules are more convenient to store, have lower raw material cost, are easier to dissolve and operate, and have higher practical application value.

[0018] In some embodiments, the water temperature in the system to be treated is ≤10℃.

[0019] In some embodiments, the water temperature in the system to be treated is 4℃ to 10℃.

[0020] In some embodiments, the system to be treated is subjected to denitrification treatment by using a sequencing batch activated sludge method.

[0021] In some embodiments, the N-butyryl-homoserine lactone is added to the system to be treated at an interval of one or two operation cycles according to the operation cycle of the sequencing batch activated sludge method.

[0022] In some embodiments, the N-butyryl-homoserine lactone is added to the system to be treated once every interval of one or two operation cycles.

[0023] In some embodiments, the concentration of the N-butyryl-homoserine lactone added to the system to be treated is 10 μg / L to 100 μg / L each time the N-butyryl-homoserine lactone is added.

[0024] In some embodiments, the concentration is 10 μg / L to 50 μg / L.

[0025] In some embodiments, the concentration is 10 μg / L to 38 μg / L.

[0026] In some embodiments, at least one of the following conditions (a1) to (a6) is satisfied;

[0027] (a1) the initial concentration of activated sludge in the system to be treated is 3000 mg / L to 7000 mg / L;

[0028] (a2) the length of the operation cycle is 12 h to 24 h;

[0029] (a3) the length of the anoxic agitation in each operation cycle is 2.5 h to 3 h;

[0030] (a4) the aeration time in each operation cycle is ≥ 8 h;

[0031] (a5) the drainage ratio in each operation cycle is 30% to 50%;

[0032] (a6) the pH of the system to be treated in each operation cycle is 7 to 8. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. Other related drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The total nitrogen removal rate of Example 1 and Comparative Example 1 of the present application is shown in the line graph.

[0035] Figure 2 The ion state ammonia nitrogen removal rate fold line chart of the embodiment 1 and the comparative example 1 of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below. The specific conditions are not specified in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0037] It should be noted that in the present application, "and / or", such as "feature 1 and / or feature 2", means that it can be "feature 1" alone, "feature 2" alone, or "feature 1" plus "feature 2".

[0038] In addition, in the description of the present application, unless otherwise specified, "multiple" in "one or more" means two or more; the range of "value a~value b" includes both end values "a" and "b", and "unit of measurement" in "value a~value b+unit of measurement" represents the "unit of measurement" of both "value a" and "value b".

[0039] The treatment method for improving the denitrification performance of the activated sludge method at low temperature in the embodiments of the present application will be described exemplarily below.

[0040] The embodiments of the present application provide a treatment method for improving the denitrification performance of the activated sludge method at low temperature, comprising: adding N-butyryl-homoserine lactone to the to-be-processed system when the water temperature in the to-be-processed system is ≤12℃.

[0041] In the embodiments of the present application, the activated sludge method can be carried out according to the conventional process standard, and the implementation form is not limited, and the sequencing batch activated sludge method or the continuous flow activated sludge method can be used. Among them, the to-be-processed system refers to the system in which the activated sludge and the to-be-processed target are located, for example, a sewage treatment system inoculated with activated sludge.

[0042] In some embodiments of the present application, the water temperature in the to-be-processed system is, for example but not limited to, any one of 2℃, 3℃, 4℃, 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, 11℃, 12℃ or a range value between any two of them.

[0043] It can be understood that the conventional positive and negative temperature deviation based on the specified temperature should be understood as within the protection scope of the embodiments of the present application. Taking 12℃ as an example, for example, 12±0.5℃, or 12±0.2℃, or 12±0.1℃.

[0044] The processing method provided by the embodiments of the present application has at least the following beneficial effects when the to-be-processed system is in a low-temperature condition of water temperature ≤12℃:

[0045] 1. By adding the C4-HSL signal molecule to intervene in the quorum sensing phenomenon among microorganisms, the community structure of microorganisms in the system is optimized, the quorum sensing phenomenon is stimulated, the interspecific cooperation of functional bacteria is enhanced, efficient removal of pollutants is achieved, and the abundance of nitrifying bacteria can be effectively improved and the denitrification performance of the activated sludge system can be improved.

[0046] In some experiments with water temperature ≤12℃, compared with no addition of signal molecules, the low-temperature denitrification effect in different experiments with the addition of C4-HSL can be improved by 36% to 80%, the low-temperature denitrification effect in different experiments with the addition of C6-HSL can be improved by 26% to 78%, the low-temperature denitrification effect in different experiments with the addition of C8-HSL can be improved by 40% to 78%, and the low-temperature denitrification effect in different experiments with the addition of C12-HSL can be improved by 25% to 57%, which confirms that the improvement effect of C4-HSL on low-temperature denitrification can reach or be higher than that of long-chain AHLs.

[0047] 2. In the case of effectively improving the denitrification effect, the sludge concentration can also be reduced, the amount of excess sludge can be reduced, and thus the sludge treatment cost can be reduced.

[0048] 3. Compared with measures such as heat preservation or temperature rise, modification of treatment equipment, and addition of low-temperature bacterial agents, the addition of signal molecules can quickly start and take effect, and can meet the emergency treatment needs of sudden temperature drop; moreover, the time and equipment cost input are lower.

[0049] 4. Compared with common long-chain AHLs signal molecules, C4-HSL is more convenient to store (C6-HSL, C8-HSL, and C12-HSL need to be stored at a low temperature of about -20℃, and C4-HSL can be stored at room temperature), has a lower raw material cost (the price of C6-HSL is about 20 times that of C4-HSL, the price of C8-HSL is about 34 times that of C4-HSL, and the price of C6-HSL is about 18 times that of C4-HSL), is easier to dissolve and operate (at a low temperature, the solubility of C6-HSL and C8-HSL is ≤30 mg / L, and C12-HSL is in a difficult-to-dissolve state, and a series of operations are needed to help dissolve before addition; C4-HSL is easily soluble), and has higher practical application value.

[0050] It is found in the research process that, in some embodiments of the present application, when the water temperature in the system to be treated is reduced to 10℃, 7℃, 4℃, etc., the abundance of nitrifying bacteria can be improved and the denitrification performance of the activated sludge system can be effectively improved after adding C4-HSL.

[0051] Based on the above research, in some embodiments, the water temperature in the system to be treated is ≤10℃.

[0052] Based on the above research, in some embodiments, the water temperature in the system to be treated is ≤10℃.

[0053] It is found in the research process that, based on the sequencing batch activated sludge method, the abundance of nitrifying bacteria can be improved and the denitrification performance of the activated sludge system can be improved after adding C4-HSL at low temperature.

[0054] Based on this, in some embodiments, the sequencing batch activated sludge method is used for denitrification treatment of the system to be treated.

[0055] It should be noted that, in the embodiments of the present application, the addition method of C4-HSL is not limited, and one-time addition or multiple-time addition can be selected.

[0056] In some embodiments, N-butyryl-homoserine lactone is added to the system to be treated at periodic intervals according to the operation cycle of the sequencing batch activated sludge method.

[0057] The above-mentioned periodic interval feeding method refers to adding N-butyryl-homoserine lactone to the system to be treated in multiple times at intervals, and the time interval between two feedings is based on the operation cycle of the sequencing batch activated sludge method, which can be, for example, 1, 2, 3, 4 or more operation cycles.

[0058] In the above-mentioned technical solution, C4-HSL is added at periodic intervals according to the operation cycle of the sequencing batch activated sludge method, which ensures that C4-HSL can play a long-term and continuous role, and is conducive to better improving the abundance of nitrifying bacteria and improving the denitrification performance of the activated sludge system.

[0059] It should be noted that, in the embodiments of the present application, after the low-temperature denitrifying bacteria are cultured by adding C4-HSL, the addition of C4-HSL can be stopped.

[0060] It is found in the research that, when C4-HSL is added in the culture of the low-temperature denitrifying bacteria, the interval between the addition of C4-HSL should not be too long when the low-temperature denitrifying bacteria have not been cultured. If the interval is too long, the effect of C4-HSL in the later stage is small, which will eventually affect the improvement of the denitrification performance of the activated sludge system.

[0061] Therefore, as an example, N-butyryl-homoserine lactone is added to the system to be treated once every 1 or 2 operation cycles.

[0062] It is found in the research that, when C4-HSL is added at a concentration of 10 μg / L at low temperature, the abundance of nitrifying bacteria is significantly improved, and the denitrification performance of the activated sludge system is improved. Within a certain range, the effect of C4-HSL is more obvious as the concentration of C4-HSL increases. When the concentration of C4-HSL increases to a certain extent, the effect of C4-HSL is no longer obviously improved as the concentration of C4-HSL continues to increase.

[0063] Based on the above research, in some embodiments, the concentration of N-butyryl-homoserine lactone in the system to be treated is 10 μg / L to 100 μg / L when N-butyryl-homoserine lactone is added each time.

[0064] The concentration of N-butyryl-homoserine lactone mentioned above refers to the ratio of the mass of N-butyryl-homoserine lactone to the volume of the system to be treated after N-butyryl-homoserine lactone is added to the system to be treated.

[0065] In some embodiments of the present application, the concentration of N-butyryl-homoserine lactone added each time is, for example but not limited to, any one of 10 μg / L, 20 μg / L, 30 μg / L, 40 μg / L, 50 μg / L, 60 μg / L, 70 μg / L, 80 μg / L, 90 μg / L, and 100 μg / L, or a range value between any two of them.

[0066] In some embodiments, the concentration is optionally 10 μg / L to 50 μg / L.

[0067] In some embodiments, the concentration is optionally 10 μg / L to 38 μg / L.

[0068] In the above technical solution, the concentration of C4-HSL is controlled within an appropriate range, which can significantly improve the abundance of nitrifying bacteria and the denitrification performance of the activated sludge system, and make the added C4-HSL fully play a role, thereby achieving a high cost performance.

[0069] In the embodiments of the present application, the process parameters of the sequencing batch activated sludge method can be controlled according to conventional requirements. Based on the embodiments of using the sequencing batch activated sludge method to perform denitrification treatment on the system to be treated, in order to better perform denitrification treatment at low temperature in combination with C4-HSL, in some exemplary embodiments, at least one of the following conditions (a1) to (a6) is met.

[0070] (a1) The initial concentration of activated sludge in the system to be treated is 3000 mg / L to 7000 mg / L; as an example, the initial concentration of activated sludge is, for example but not limited to, any one of 3000 mg / L, 4000 mg / L, 5000 mg / L, 6000 mg / L, 7000 mg / L, or a range value between any two of them.

[0071] (a2) The length of the operation cycle is 12 h to 24 h; as an example, the operation cycle is, for example but not limited to, any one of 12 h, 15 h, 18 h, 21 h, 24 h, or a range value between any two of them.

[0072] (a3) In each operation cycle, the length of anoxic stirring is 2.5 h to 3 h; as an example, the length of anoxic stirring is, for example but not limited to, any one of 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, 3 h, or a range value between any two of them.

[0073] (a4) In each operation cycle, the aeration time is ≥8 h; as an example, the aeration time is, for example but not limited to, any one of 8 h, 12 h, 18 h, 24 h, etc., or a range value between any two of them.

[0074] (a5) In each operation cycle, the drainage ratio is 30% to 50%; as an example, the drainage ratio is, for example but not limited to, any one of 30%, 35%, 40%, 45%, 50%, or a range value between any two of them.

[0075] (a6) In each operation cycle, the pH of the system to be treated is 7 to 8; as an example, the operation cycle is, for example but not limited to, any one of 12 h, 15 h, 18 h, 21 h, 24 h, or a range value between any two of them.

[0076] The features and performances of the present application are further described in detail below in combination with embodiments.

[0077] I. Experimental conditions of the embodiments and comparative examples are as follows:

[0078] Example 1

[0079] The sequencing batch activated sludge method is used to perform denitrification treatment on the system to be treated, and the experimental conditions are as follows:

[0080] The temperature of the water in the system to be treated was suddenly reduced from 25°C to 10°C, and the experimental site was an activated sludge SBR reactor with an effective volume of 1 L and an activated sludge concentration of 4000 mg / L.

[0081] The influent water quality was chemical oxygen demand (COD): 250 mg / L, ionic ammonia nitrogen (NH4 + -N): 30 mg / L, total phosphorus (TP): 1.5 mg / L, and pH was maintained at 7-8. One operating cycle was operated in a 12 h sequencing batch activated sludge process, with 2.5 h of anoxic phase, 8 h of aeration phase, and 1.5 h of resting phase; the dissolved oxygen (DO) was maintained below 0.5 mg / L in the anoxic phase and above 2.5 mg / L in the aeration phase.

[0082] A N-butyryl-homoserine lactone stock solution with a concentration of 10 mg / L was prepared, and N-butyryl-homoserine lactone with a concentration of 10 μg / L was added every 2 operating cycles following the influent (i.e., the water temperature and exogenous addition conditions were: water temperature was reduced to 10°C, and the C4-HSL addition concentration was 10 μg / L).

[0083] Example 2

[0084] The system to be treated was subjected to denitrification treatment by using a sequencing batch activated sludge process, and the experimental conditions were different from those of Example 1 in that:

[0085] N-butyryl-homoserine lactone with a concentration of 100 μg / L was added every 2 operating cycles following the influent (i.e., the water temperature and exogenous addition conditions were: water temperature was reduced to 10°C, and the C4-HSL addition concentration was 100 μg / L).

[0086] Example 3

[0087] The system to be treated was subjected to denitrification treatment by using a sequencing batch activated sludge process, and the experimental conditions were different from those of Example 1 in that:

[0088] N-butyryl-homoserine lactone with a concentration of 50 μg / L was added every 2 operating cycles following the influent (i.e., the water temperature and exogenous addition conditions were: water temperature was reduced to 10°C, and the C4-HSL addition concentration was 50 μg / L).

[0089] Example 4

[0090] The system to be treated was subjected to denitrification treatment by using a sequencing batch activated sludge process, and the experimental conditions were different from those of Example 1 in that:

[0091] The water temperature in the system to be treated was suddenly reduced from 25℃ to 7℃; after stable operation, the water temperature was further reduced to 4℃ (i.e. the water temperature and exogenous addition conditions were: the water temperature was reduced to 7℃ and then to 4℃ after stable operation, and the C4-HSL addition concentration was 10 μg / L).

[0092] Example 5

[0093] The system to be treated was subjected to denitrification treatment by using the sequencing batch activated sludge method, and the difference between the experimental conditions and those of Example 4 was that:

[0094] C4-HSL with an addition concentration of 100 μg / L was added once every 2 operation cycles following the influent (i.e. the water temperature and exogenous addition conditions were: the water temperature was reduced to 7℃ and then to 4℃ after stable operation, and the C4-HSL addition concentration was 100 μg / L).

[0095] Comparative Example 1

[0096] The system to be treated was subjected to denitrification treatment by using the sequencing batch activated sludge method, and the difference between the experimental conditions and those of Example 1 was that:

[0097] No N-butyryl-homoserine lactone was added (i.e. the water temperature and exogenous addition conditions were: the water temperature was reduced to 10℃, and no C4-HSL was added).

[0098] Comparative Example 2

[0099] The system to be treated was subjected to denitrification treatment by using the sequencing batch activated sludge method, and the difference between the experimental conditions and those of Example 4 was that:

[0100] No N-butyryl-homoserine lactone was added (i.e. the water temperature and exogenous addition conditions were: the water temperature was reduced to 7℃ and then to 4℃ after stable operation, and no C4-HSL was added).

[0101] Comparative Example 3

[0102] The system to be treated was subjected to denitrification treatment by using the sequencing batch activated sludge method, and the difference between the experimental conditions and those of Comparative Example 1 was that:

[0103] Denitrification treatment was performed at normal temperature, and the system to be treated was not subjected to temperature reduction (i.e. the water temperature and exogenous addition conditions were: the water temperature was normal temperature, and no C4-HSL was added).

[0104] Comparative Example 4

[0105] The system to be treated was subjected to denitrification treatment by using the sequencing batch activated sludge method, and the difference between the experimental conditions and those of Example 1 was that:

[0106] Denitrification treatment was performed at normal temperature, and the system to be treated was not subjected to temperature reduction (i.e. the water temperature and exogenous addition conditions were: the water temperature was normal temperature, and the C4-HSL addition concentration was 10 μg / L).

[0107] Comparative Example 5

[0108] The nitrogen removal treatment was carried out on the system to be treated by using the sequencing batch activated sludge method, and the difference between the experimental conditions and Example 2 was that:

[0109] The nitrogen removal treatment was carried out at room temperature without cooling the system to be treated (i.e. the water temperature and exogenous addition conditions were: water temperature was room temperature, and C4-HSL addition concentration was 100 μg / L).

[0110] II. Some detection index results during and at the end of the experiments of each example and comparative example are as follows:

[0111] Example 1

[0112] The nitrogen removal effect detection results: the effluent of the reactor was collected every 12 hours as a cycle to detect the pollutant removal effect. After a short adaptation, the COD concentration of the effluent of the reactor was reduced to below 50 mg / L, and the removal rate was always maintained at about 90%; after the addition of N-butyryl-homoserine lactone, the nitrogen removal effect gradually became prominent, and in the 23rd cycle, the NH4 + -N removal rate reached more than 99%, the effluent concentration was reduced to 0.06 mg / L, and the reactor has maintained a high NH4 + -N removal rate since the 23rd cycle, with an average removal rate of 99.69%; the total nitrogen (TN) removal rate reached a stable state after the 27th cycle, with an average removal rate of 64.97%, and the average effluent concentration was 11.40 mg / L, which was lower than 15 mg / L.

[0113] Microbial and metagenomic detection results: after the treatment effect was stable, high-throughput sequencing was performed on the activated sludge to analyze the microbial community composition. The abundance of ammonia-oxidizing bacteria MND1 was 0.007%, the abundance of complete nitrifying bacteria Nitrospira was 0.100%, and the abundances of denitrifying bacteria Denitratisoma and Dechloromonas were 0.189% and 0.246%, respectively. The metagenomic results showed that the complete nitrification process of the activated sludge system with the addition of 10 μg / L N-butyryl-homoserine lactone accounted for 12.53% in the nitrogen metabolism process; the abundances of CS, sdh and fum genes participating in the tricarboxylic acid (TCA) cycle were 0.017%, 0.030% and 0.018%, respectively; and the abundances of the regulation, transport and decomposition genes related to quorum sensing were 2.40%, 7.75% and 1.92%, respectively. When the N-butyryl-homoserine lactone addition concentration was 10 μg / L, the functional bacteria and functional gene abundances in the activated sludge SBR reactor increased, thereby improving the nitrogen removal effect of the reactor.

[0114] Sludge concentration detection results: After stable operation, the sludge concentration in the reactor was reduced by about 2% compared with the control group (without adding C4-HSL), indicating that the sludge production was less, reducing the cost of sludge treatment and disposal, and having strong practical significance.

[0115] Comparative Example 1

[0116] Denitrification effect detection results: The reactor effluent was collected every 12 hours as a cycle to detect the pollutant removal effect. After a short adaptation, the COD concentration in the reactor effluent was reduced to below 50 mg / L, and the removal rate was always maintained above 90%; the reactor effluent NH4 + -N reached stability from the 15th cycle, with an average removal rate of 72.87% and an average effluent concentration of 8.77 mg / L (not meeting the maximum allowable discharge concentration of NH4 + -N in most municipal wastewater treatment plants when the water temperature is lower than 12℃); the TN removal rate reached stability after 27 cycles, with an average removal rate of 52.38% and an average effluent concentration of 15.49 mg / L (not meeting the maximum allowable discharge concentration of TN in most municipal wastewater treatment plants when the water temperature is lower than 12℃).

[0117] Microbial and metagenomic detection results: After the treatment effect was stable, high-throughput sequencing was performed on the activated sludge to analyze the microbial community composition. The abundance of ammonia-oxidizing bacteria MND1 was 0.003%, and the abundance of complete nitrifying bacteria Nitrospira was 0.089%; the abundances of denitrifying bacteria Denitratisoma and Dechloromonas were 0.180% and 0.213%, respectively. The metagenomic results showed that the complete nitrification process accounted for 12.46% in the activated sludge system with the addition of 0 μg / L N-butyryl-homoserine lactone during the nitrogen metabolism process; the abundances of CS, sdh and fum genes participating in the TCA cycle were 0.016%, 0.029% and 0.017%, respectively; the abundances of regulation, transport and decomposition genes related to quorum sensing were 2.08%, 6.61% and 1.70%, respectively. When the N-butyryl-homoserine lactone addition concentration was 0 μg / L, the functional bacteria and functional gene abundances in the activated sludge SBR reactor were low, and the denitrification effect was poor, which made the wastewater unable to meet the discharge standard under low temperature conditions.

[0118] Comparison of Example 1 and Comparative Example 1

[0119] The denitrification effect detection results of Example 1 and Comparative Example 1 are shown in the line graph of Figure 1 and Figure 2 . Among them, Figure 1 is the total nitrogen removal rate, and 2 is the ion ammonia nitrogen removal rate; 10 μg / L corresponds to Comparative Example 1, and Control corresponds to Comparative Example 1.

[0120] According toFigure 1 and Figure 2 It can be seen that, compared with the case without adding C4-HSL in Comparative Example 1, the total nitrogen removal rate and the ion ammonia nitrogen removal rate are both significantly improved in Example 1 by adding C4-HSL at low temperature.

[0121] Example 2

[0122] Denitrification effect detection result: The effluent of the reactor was collected every 12 hours as a cycle to detect the pollutant removal effect. After a short adaptation, the COD concentration of the effluent of the reactor was reduced to below 50 mg / L, and the removal rate was always maintained at about 90%; after adding C4-HSL, the nitrification effect gradually became prominent, and the effluent NH4 + -N removal rate reached more than 99%, the effluent concentration was reduced to 0.17 mg / L, and the reactor has maintained a high NH4 + -N removal rate since the 15th cycle, the average removal rate was 99.85%; the TN removal rate reached a stable state after 27 cycles, the average removal rate was 60.46%, the average effluent concentration was 12.86 mg / L, which was lower than 15 mg / L.

[0123] Microbial and metagenomic detection results: After the treatment effect is stable, high-throughput sequencing is performed on the activated sludge to analyze the microbial community composition. The abundance of ammonia-oxidizing bacteria Ellin6067 and MND1 is 0.393% and 0.005% respectively, and the abundance of complete nitrifying bacteria Nitrospira is 0.222%; the abundance of 11 kinds of denitrifying bacteria (Rhodoferax, Dokdonella, Terrimonas, Sphaerotilus, Rhodobacter, unclassified_f_Comamonadaceae, norank_f_Gemmatimonadaceae, Ferrμginibacter, Tessaracoccus, Nakamurella and norank_f_Saprospiraceae) is 16.53%; the abundance of heterotrophic nitrification-aerobic denitrifying bacteria (Microbacterium) is 0.463%. The metagenomic results show that the complete nitrification process of the activated sludge system with the addition of 100 μg / L C4-HSL accounts for 13.82% in the nitrogen metabolism process, and the abundance of nitrification gene nxr is 0.027%, and the abundance of denitrification gene nirK is 0.015%; the abundance of CS, sdh, fum and mdh genes involved in TCA cycle is 0.021%, 0.040%, 0.021% and 0.011% respectively; the abundance of regulation, transport and decomposition genes related to quorum sensing is 2.98%, 9.22% and 2.50% respectively. It can be seen that when the C4-HSL addition concentration is 100 μg / L, the abundance of functional bacteria and functional genes in the activated sludge SBR reactor increases, thereby improving the denitrification effect of the reactor.

[0124] Sludge concentration detection results: After stable operation, the sludge concentration of the reactor is reduced by about 12% compared with the control group (without adding C4-HSL), indicating that the sludge production is less, reducing the cost of sludge treatment and disposal, and having strong practical significance.

[0125] Example 3

[0126] Denitrification effect detection results: The effluent of the reactor is collected every 12 hours as a cycle to detect the pollutant removal effect. After a short adaptation, the COD concentration of the reactor effluent is reduced to below 50 mg / L, and the removal rate is always maintained at about 90%; after the addition of N-butyryl-homoserine lactone, the denitrification effect gradually highlights, and in the 19th cycle, the NH4 + -N removal rate reaches more than 99%, and the effluent concentration is reduced to 0.05 mg / L, and the reactor has maintained a high NH4 +The average removal rate of N is 99.69%, and the removal rate of TN reaches a stable value after 27 cycles, with an average removal rate of 64.97% and an average effluent concentration of 12.40 mg / L, which is lower than 15 mg / L.

[0127] Sludge concentration detection result: After stable operation, the sludge concentration of the reactor is about 6% lower than that of the control group (without adding C4-HSL), indicating that the sludge production is less, the cost of sludge treatment and disposal is reduced, and it has strong practical significance.

[0128] Comparison of Examples 1-3

[0129] According to the test results of Examples 1-3, when the C4-HSL addition concentration is 10 μg / L, 50 μg / L and 100 μg / L, the average ammonia nitrogen removal rates are 99.69%, 99.69% and 99.85%, respectively, the average total nitrogen removal rates are 64.97%, 64.97% and 60.46%, respectively, and the sludge concentrations are 2%, 6% and 12% lower than those of the control group (Comparative Example 1), respectively. In terms of improving denitrification performance, when the C4-HSL addition concentration is 10 μg / L-50 μg / L, the denitrification performance can be significantly improved, and further increasing the C4-HSL addition concentration can further reduce the sludge concentration.

[0130] Examples 4, 5 and Comparative Example 2

[0131] Denitrification effect detection result: When the water temperature is reduced to 7℃, the average ammonia nitrogen removal rates of SBRs with 0 μg / L, 10 μg / L and 100 μg / L C4-HSL are 55.6%, 96.9% and 96.3%, respectively; when the temperature is further reduced to 4℃, the average ammonia nitrogen removal rates of SBRs with 0 μg / L, 10 μg / L and 100 μg / L C4-HSL are 45.1%, 99.3% and 98.8%, respectively.

[0132] Sludge concentration detection result: When the temperature is 7℃, the sludge concentrations of SBRs with 10 μg / L and 100 μg / L C4-HSL are 22% and 19% lower than that of the control group (without adding C4-HSL); when the temperature is 4℃, the sludge concentrations of SBRs with 10 μg / L and 100 μg / L C4-HSL are 40% and 38% lower than that of the control group (without adding C4-HSL).

[0133] Microbial and metagenomic detection results: Exogenous C4-HSL has a significant impact on the microbial community of the biofilm during the cooling process. When the temperature is 7℃, after the system stabilizes, exogenous C4-HSL increases the relative abundance of TM7a in the Ossunkia door, Nakamurella and Tessaracoccus in the Actinobacteriota door, and Ferrμginibacter in the Bacteroidota door. When the temperature is 4℃, after the system stabilizes, exogenous C4-HSL promotes the growth of Arthrobacter, Nakamurella, Micrococcaceae and typical nitrifying bacteria Nitrosomonas in the Actinobacteriota door. It can be seen that under different temperature conditions, exogenous C4-HSL increases the abundance of different dominant core bacterial genera, thereby maintaining high level of ammonia nitrogen treatment efficiency.

[0134] Comparative Example 3-Comparative Example 5

[0135] Denitrification effect detection results: At room temperature, adding different concentrations (0, 10, 100 μg / L) of signal molecule C4-HSL, after 74 cycles of operation, the removal rate of COD is more than 90%; the effluent ammonia nitrogen is more than 0.1 mg / L, and the removal rate is more than 99%; the total nitrogen in the effluent is less than 15 mg / L. It can be seen that at room temperature, whether adding signal molecule C4-HSL or not has little effect on the denitrification treatment effect.

[0136] Microbial and metagenomic detection results: At the level of door, after adding exogenous C4-HSL, the growth of Proteobacteria (Bacteroidota) and Bacteroidota (Bacteroidota) is inhibited, and the higher the concentration, the stronger the inhibition; it can promote the growth and reproduction of Patescibacteria, and the promotion effect increases with the increase of concentration; while for Actinobacteriota (Actinobacteriota) and Gemmatimonadota (Gemmatimonadota), it shows low concentration inhibition and high concentration promotion. At the genus level, after adding low concentration C4-HSL, the relative content of Nakamurella (nitrifying bacteria) decreases slightly from 17.46% to 16.66%, and after adding high concentration C4-HSL, the relative content increases to 20.79%. It is found that adding C4-HSL has a low concentration promotion and high concentration inhibition effect on the growth of microorganisms.

[0137] The above-described embodiments are part of the embodiments of the present application, not all embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

Claims

1. A treatment method for improving the denitrification performance of activated sludge process at low temperatures, characterized in that, include: When the water temperature in the system to be treated is ≤12℃, N-butyryl-homoserine lactone is added to the system to be treated; The nitrogen removal process of the system to be treated was carried out using the sequencing batch activated sludge process. According to the operating cycle of the sequencing batch activated sludge process, the N-butyryl-homoserine lactone is added to the system to be treated at intervals in different cycles. Each time the N-butyryl-homoserine lactone is added, the concentration of the N-butyryl-homoserine lactone in the system to be treated is 10 μg / L to 100 μg / L.

2. The treatment method for improving the denitrification performance of activated sludge process at low temperature according to claim 1, characterized in that, The water temperature in the system to be treated is ≤10℃.

3. The treatment method for improving the denitrification performance of activated sludge process at low temperature according to claim 2, characterized in that, 4℃≤water temperature in the system to be treated≤10℃.

4. The treatment method for improving the denitrification performance of activated sludge process at low temperature according to claim 1, characterized in that, The N-butyryl-homoserine lactone is added to the system to be treated once every one or two operating cycles.

5. The treatment method for improving the denitrification performance of activated sludge process at low temperature according to claim 1, characterized in that, The concentration of the additive is 10 μg / L to 50 μg / L.

6. The treatment method for improving the denitrification performance of activated sludge process at low temperature according to claim 5, characterized in that, The concentration of the additive is 10 μg / L to 38 μg / L.

7. The treatment method for improving the denitrification performance of activated sludge process at low temperature according to any one of claims 1, 4 to 6, characterized in that, It satisfies at least one of the following conditions (a1) to (a6); (a1) In the system to be treated, the initial concentration of activated sludge is 3000 mg / L to 7000 mg / L; (a2) The duration of the operating cycle is 12h~24h; (a3) The duration of anoxic stirring in each of the aforementioned operating cycles is 2.5h to 3h; (a4) In each of the aforementioned operating cycles, the aeration time is ≥8h; (a5) In each of the aforementioned operating cycles, the drainage ratio is 30%~50%; (a6) In each of the said operating cycles, the pH of the system to be treated is 7 to 8.

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