Method and system for enhancing activated sludge treatment of low-temperature domestic sewage by using plant hormones

Abstract

The present application belongs to the technical field of urban domestic sewage treatment, and discloses a method and system for treating low-temperature domestic sewage by using plant hormones to strengthen activated sludge. The method optimizes the type and dosage of functional plant hormones for strengthening low-temperature sewage treatment, adds trace plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage, and monitors the concentrations of chemical oxygen demand COD, ammonia nitrogen, total nitrogen, total phosphorus in the effluent, and the residual amount of plant hormones. In the present application, trace plant hormones are added to the treatment of low-temperature domestic sewage in cold regions in winter. The plant hormones regulate the activity and functional gene expression of microorganisms, enhance the interaction between microbial communities, improve the resistance of functional microorganisms to low-temperature stress, and improve the sewage treatment effect. The present application realizes stable and standard discharge of low-temperature sewage in winter without external carbon source supplement, without increasing aeration, and without additional energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of urban domestic sewage treatment technology, and particularly relates to a method and system for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge. Background Technology

[0002] my country's cold-region area covers 4.174 million square kilometers, accounting for 43.5% of its land area. In winter, the temperature of domestic sewage in these cold regions is typically below 10°C. Under low-temperature stress, microbial activity decreases; for every 10°C drop in temperature, biological activity decreases by 50%, leading to a severe decline in sewage treatment efficiency. Common methods to ensure sewage treatment meets discharge standards include increasing sludge concentration, extending hydraulic retention time, supplementing carbon sources, increasing aeration, increasing chemical dosage, and adding cold-resistant bacterial agents. However, these methods sacrifice sewage treatment efficiency, resulting in a significant increase in chemical and energy consumption at sewage treatment plants, with winter sewage treatment costs increasing by more than 30%.

[0003] Microorganisms are key to biological wastewater treatment, communicating and regulating their collective behavior and function through small molecule chemicals (called "signaling molecules"). Previous studies have found that adding exogenous signaling molecules can enhance wastewater treatment efficiency. However, the high cost and limited large-scale production of these molecules significantly restrict their widespread application in wastewater treatment. Our research group previously detected plant hormones in activated sludge from wastewater treatment plants. These hormones possess similar regulatory functions to signaling molecules, precisely regulating the activity of functional microorganisms and their interactions within the community. Even minute amounts can achieve significant stress-resistance and synergistic effects. Furthermore, compared to signaling molecules, plant hormones are inexpensive, have mature large-scale production processes, and hold broad application prospects in low-temperature wastewater treatment. Summary of the Invention

[0004] To address the bottleneck problem in wastewater treatment at low temperatures during winter, this invention provides a method and system for treating low-temperature domestic wastewater using plant hormone-enhanced activated sludge, specifically involving a method for treating low-temperature urban domestic wastewater using plant hormone-enhanced activated sludge.

[0005] The technical solution is as follows: A method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge, the method comprising:

[0006] S1, screening functional plant hormones and optimizing dosage;

[0007] S2, adding trace amounts of plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage;

[0008] S3 detects the concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus in the water, as well as the residues of plant hormones.

[0009] Furthermore, in step S1, the plant hormone is one of benzoic acid, indoleacetic acid, indolebutyric acid, naphthaleneacetic acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, p-hydroxybenzoic acid, and brassinolide.

[0010] In step S2, the temperature of the low-temperature domestic sewage is 4~10℃.

[0011] In step S2, the concentration of the added plant hormone is 0.1~5 μmol / L.

[0012] In step S2, the microorganisms in the aerobic reaction stage are activated sludge in the aerobic tank, and the concentration of activated sludge is 2800~5000 mg / L.

[0013] In step S2, the aerobic treatment time is 5-11 hours.

[0014] In step S2, the concentrations of pollutants in the wastewater are: COD 70~200mg / L, ammonia nitrogen 30~55mg / L, and total nitrogen 36~55mg / L.

[0015] Furthermore, in step S3, the chemical oxygen demand (COD) in the effluent is <50 mg / L, ammonia nitrogen is <5 mg / L, total nitrogen (TN) is <15 mg / L, the removal rate of plant hormones is over 97%, and the residual concentration is <0.01 mg / L.

[0016] Another object of the present invention is to provide a system for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge, comprising:

[0017] A functional plant hormone screening system is used to screen functional plant hormones that enhance the treatment of low-temperature domestic sewage. The plant hormones include one of the following: benzoic acid, indoleacetic acid, indolebutyric acid, naphthaleneacetic acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, p-hydroxybenzoic acid, and brassinolide.

[0018] An enhanced low-temperature domestic sewage biological treatment system, connected to the aforementioned functional plant hormone screening system, is used to add trace amounts of plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage, dispersing them evenly throughout the sewage treatment system through aeration and circulation. The enhanced low-temperature domestic sewage biological treatment system is used to optimize the parameters of the functional plant hormone screening system, and the functional plant hormone screening system guides the enhanced low-temperature domestic sewage biological treatment system based on the optimized data.

[0019] The effluent water quality and plant hormone residue detection system is connected to the enhanced low-temperature domestic sewage biological treatment system. It is used to detect the concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus in the effluent, as well as the residue status of plant hormones, and to feed back the effluent water quality and plant hormone residue detection system to the enhanced low-temperature domestic sewage biological treatment system. The enhanced low-temperature domestic sewage biological treatment system can then adjust the effluent water quality and plant hormone residue detection system.

[0020] Combining all the above technical solutions, the beneficial effects of this invention are as follows: This invention adds trace amounts of plant hormones to low-temperature urban domestic sewage, which regulates the activity and functional gene expression of microorganisms, enhances the interaction between microbial communities, improves the resistance of functional microorganisms to low-temperature stress, and improves the sewage treatment effect. It achieves stable and compliant discharge of low-temperature sewage in winter without external carbon source supplementation, without increasing aeration, and without additional energy consumption. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0022] Figure 1 This is a flowchart of a method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge provided by the present invention.

[0023] Figure 2 This is a schematic diagram of a system for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge, as provided by the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] The innovation of this invention lies in enhancing the stress resistance of activated sludge to low-temperature stress through trace amounts of functional plant hormones, thereby improving the treatment efficiency of urban domestic sewage in winter.

[0026] like Figure 1 As shown, the method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge provided by the present invention includes:

[0027] S1, screening functional plant hormones and optimizing dosage;

[0028] S2, adding trace amounts of plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage;

[0029] S3 detects the concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus in the water, as well as the residues of plant hormones.

[0030] For example, in step S1, the plant hormone includes one of benzoic acid, indoleacetic acid, indolebutyric acid, naphthaleneacetic acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, p-hydroxybenzoic acid, and brassinolide.

[0031] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0032] For example, in step S2, the temperature of the low-temperature domestic sewage is 4~10℃; the domestic sewage can be sewage from a municipal sewage treatment plant.

[0033] For example, in step S2, the concentration of the added plant hormone is 0.1~5 μmol / L; preferably, the preferred concentration of the added plant hormone is 2 μmol / L.

[0034] For example, in step S2, the microorganisms in the aerobic reaction stage are activated sludge from the aerobic tank of a municipal wastewater treatment plant, and the concentration of activated sludge is 2800~5000 mg / L.

[0035] In another example, in this invention, the low-temperature urban domestic sewage is actual domestic sewage, and the biomass of activated sludge used to treat low-temperature urban domestic sewage is preferably 3200~4200 mg / L.

[0036] For example, in step S2, the aerobic treatment time is 5 to 11 hours, preferably 8 to 11 hours.

[0037] For example, in step S2, the concentrations of pollutants in the wastewater are: COD 70~200mg / L, ammonia nitrogen 30~55mg / L, and total nitrogen 36~55mg / L.

[0038] For example, in step S3, under the preferred conditions, the effluent meets the Class A discharge standard of the municipal wastewater treatment plant pollutant discharge standard (GB18918-2002): chemical oxygen demand (COD) < 50 mg / L, ammonia nitrogen < 5 mg / L, and total nitrogen (TN) < 15 mg / L. The plant hormone removal rate is above 97%, and under the preferred conditions, the residual amount of plant hormones in the effluent is less than 0.01 mg / L.

[0039] The effects of using trace amounts of plant hormones to enhance activated sludge treatment of low-temperature urban domestic sewage are as follows:

[0040] In this invention, compared with the control group (without added plant hormones), the treatment group with added plant hormones showed an increase of ~31.7% in the removal efficiency of organic pollutants, ~81.0% in the removal efficiency of ammonia nitrogen, ~42.2% in the removal efficiency of total nitrogen, and ~39.2% in the removal efficiency of total phosphorus in the effluent.

[0041] For example, such as Figure 2 As shown, the system for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge provided in this embodiment of the invention includes:

[0042] A functional plant hormone screening system is used to screen functional plant hormones that enhance the treatment of low-temperature domestic sewage. The plant hormones include one of the following: benzoic acid, indoleacetic acid, indolebutyric acid, naphthaleneacetic acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, p-hydroxybenzoic acid, and brassinolide.

[0043] An enhanced low-temperature domestic sewage biological treatment system, connected to the aforementioned functional plant hormone screening system, is used to add trace amounts of plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage, dispersing them evenly throughout the sewage treatment system through aeration and circulation. The enhanced low-temperature domestic sewage biological treatment system is used to optimize the parameters of the functional plant hormone screening system, and the functional plant hormone screening system guides the enhanced low-temperature domestic sewage biological treatment system based on the optimized data.

[0044] The effluent water quality and plant hormone residue detection system is connected to the enhanced low-temperature domestic sewage biological treatment system. It is used to detect the concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus in the effluent, as well as the residue status of plant hormones, and to feed back the effluent water quality and plant hormone residue detection system to the enhanced low-temperature domestic sewage biological treatment system. The enhanced low-temperature domestic sewage biological treatment system can then adjust the effluent water quality and plant hormone residue detection system.

[0045] Example

[0046] Low temperatures significantly impact biological nitrogen removal from wastewater, particularly the nitrification stage. Therefore, in our examples of screening plant hormone types and optimizing dosages, we focused on the removal efficiency of plant hormones for ammonia nitrogen.

[0047] Example 1 (Screening of functional plant hormones)

[0048] Activated sludge was collected from a municipal wastewater treatment plant, with a concentration ranging from 2800 to 5000 mg / L. Experimental conditions were set as follows: sludge concentration 3500 mg / L, wastewater COD 150 mg / L, ammonia nitrogen 30 mg / L, total nitrogen 45 mg / L, and total phosphorus 5 mg / L, at a water temperature of 6℃. Plant hormones were added for aerobic biological treatment for 5–11 hours. A control group was used without plant hormones. The experimental groups were treated with benzoic acid, indoleacetic acid, indolebutyric acid, naphthaleneacetic acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, p-hydroxybenzoic acid, and brassinolide, respectively, at a concentration of 2 μM. The addition of plant hormones enhanced the low-temperature wastewater treatment effect, increasing COD removal rate by 2.4%–23.1% and ammonia nitrogen removal rate by 31.4%–92.1% compared to the control group. Aerobic treatment mainly focuses on enhancing the removal of ammonia nitrogen with plant hormones. Based on the price of plant hormones, the top four functional plant hormones that enhance low-temperature nitrification are: indoleacetic acid > benzoic acid > naphthaleneacetic acid > indolebutyric acid.

[0049] Table 1. Screening of functional plant hormones for enhancing low-temperature wastewater treatment:

[0050]

[0051] Example 2 (Optimization of Plant Hormone Dosage)

[0052] Wastewater, activated sludge, water temperature, and wastewater treatment conditions were the same as in Example 1. Indoleacetic acid, benzoic acid, naphthaleneacetic acid, and indolebutyric acid were added at different dosages of 0.1, 0.5, 1, 2, and 5 μmol / L for each plant hormone. The enhancing effect of different dosages of plant hormones on ammonia nitrogen removal was compared. The optimal dosage of plant hormones was 1–2 μmol / L, with 2 μmol / L achieving the best ammonia nitrogen removal effect. From a cost-saving perspective, a dosage of 1 μmol / L could be considered based on the influent water quality. There were some differences between different batches of experiments; therefore, the above conclusions were drawn by comparing results from the same batch of experiments.

[0053] Table 2. Enhancement effect of different dosages of plant hormones on low-temperature domestic wastewater treatment:

[0054]

[0055] Example 3 (Plant hormone enhancement effects under different low temperature conditions)

[0056] Wastewater and activated sludge were the same as in Example 1. Water temperatures were 4℃ and 10℃, with 2 μmol / L indoleacetic acid added, serving as a control group without indoleacetic acid. A sequential batch reactor was used, with one cycle lasting 12 hours, including 5-11 hours of aerobic treatment followed by 1 hour of water exchange, for a total of 14 days. The stress-enhancing effects of plant hormones under different levels of low-temperature stress were compared. From a stress-resistance perspective, using ATP to represent microbial activity, it was found that after adding plant hormones, microbial activity increased by 2.7 times and 61.8% at 4℃ and 10℃, respectively. From a low-temperature wastewater treatment efficiency perspective, after adding plant hormones, COD removal rate increased by 38.0% and ammonia nitrogen removal rate increased by 85.8% at 4℃; at 10℃, COD removal rate increased by 9.5% and ammonia nitrogen removal efficiency increased by 20.6%. Comparing the wastewater treatment effects at 4℃ and 10℃, the stress-enhancing effect of plant hormones in strengthening low-temperature treatment was more significant at lower temperatures and with stronger stress.

[0057] Table 3. Enhancement of plant hormone resistance to different low temperatures:

[0058]

[0059] Example 4 (Effect of plant hormones in low-temperature wastewater treatment, long-term effect evaluation)

[0060] Wastewater and activated sludge were collected from a municipal wastewater treatment plant. The wastewater concentrations were: COD 70-200 mg / L, ammonia nitrogen 30-55 mg / L, total nitrogen 36-55 mg / L, and total phosphorus 3-5 mg / L. The sludge concentration was 3500 mg / L, the water temperature was 4℃, and 2 μmol / L indoleacetic acid (IAA) was added. A control group was used without IAA. The wastewater was treated using the AAO process and operated for 60 days. In the control group without plant hormones, the effluent COD was 50-54 mg / L (slightly exceeding the standard), ammonia nitrogen was 7-14 mg / L (severely exceeding the standard), and total nitrogen was 20-25 mg / L (severely exceeding the standard). In the treatment group with plant hormones, the effluent COD was 30-41 mg / L, ammonia nitrogen was 1-3 mg / L, and total nitrogen was 12-14 mg / L, consistently meeting the Class A discharge standard. After the addition of plant hormones, COD removal efficiency increased by 31.7%, ammonia nitrogen removal efficiency by 81.0%, total nitrogen removal efficiency by 42.2%, and total phosphorus removal efficiency by 39.2%. The effluent from the treatment group with added plant hormones had a slightly higher total phosphorus level, but this could be addressed by tertiary treatment following biological treatment to meet Class A standards. The plant hormones improved the total phosphorus removal rate, saving on subsequent phosphorus removal chemical consumption. Furthermore, the plant hormone removal rate was above 97% during the wastewater treatment process, and the residual indoleacetic acid in the effluent was less than 0.01 mg / L. Biotoxicity analysis showed no significant toxicity risks or environmental impacts. Therefore, plant hormone-enhanced low-temperature domestic wastewater treatment exhibits good stability.

[0061] Table 4. Long-term effects of plant hormone-enhanced low-temperature domestic wastewater treatment:

[0062]

[0063] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge, characterized in that, This method Includes the following steps: S1, screening functional plant hormones and optimizing dosage; S2, adding trace amounts of plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage; S3 detects the concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus in water, as well as the residues of plant hormones. In step S2, the concentration of plant hormone added is 2 μmol / L, and the water temperature of the low-temperature domestic sewage is 4℃; In step S1, the plant hormone is one of benzoic acid, indoleacetic acid, indolebutyric acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, and brassinolide. In step S2, the concentrations of pollutants in the wastewater are: COD 70~200mg / L, ammonia nitrogen 30~55mg / L, and total nitrogen 36~55mg / L.

2. The method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge according to claim 1, characterized in that, In step S2, the microorganisms in the aerobic reaction stage are activated sludge in the aerobic tank, and the concentration of activated sludge is 2800~5000 mg / L.

3. The method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge according to claim 1, characterized in that, In step S2, the aerobic treatment time is 5-11 hours.

4. The method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge according to claim 1, characterized in that, In step S3, the chemical oxygen demand (COD) in the effluent is <50 mg / L, ammonia nitrogen is <5 mg / L, total nitrogen (TN) is <15 mg / L, the removal rate of plant hormones is over 97%, and the residual concentration is <0.01 mg / L.

5. A system for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge, characterized in that, The method for treating low-temperature domestic sewage using plant hormone-enhanced activated sludge according to any one of claims 1-4, the system comprising: A functional plant hormone screening system is used to screen functional plant hormones that enhance the treatment of low-temperature domestic sewage. The plant hormone is one of the following: benzoic acid, indoleacetic acid, indolebutyric acid, salicylic acid, methyl jasmonate, 2,4-dichlorophenoxyacetic acid, gibberellin, and brassinolide. An enhanced low-temperature domestic sewage biological treatment system, connected to the functional plant hormone screening system, is used to add trace amounts of plant hormones to the aerobic biological treatment stage of low-temperature domestic sewage, and to evenly disperse them in the sewage treatment system through aeration and circulation; the enhanced low-temperature domestic sewage biological treatment system is used to optimize the parameters of the functional plant hormone screening system, and the functional plant hormone screening system guides the enhanced low-temperature domestic sewage biological treatment system based on the optimized data; The effluent water quality and plant hormone residue detection system is connected to the enhanced low-temperature domestic sewage biological treatment system. It is used to detect the concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus in the effluent, as well as the residue status of plant hormones, and to feed back the effluent water quality and plant hormone residue detection system to the enhanced low-temperature domestic sewage biological treatment system. The enhanced low-temperature domestic sewage biological treatment system can then adjust the effluent water quality and plant hormone residue detection system.

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