Method for synchronously removing organic micropollutants and resistance genes based on shortcut nitrification autotrophic nitrogen removal

Abstract

The invention relates to a biological sewage treatment technology, in particular to a method for synchronously removing organic micropollutants and resistance genes based on short-cut nitrification and denitrification. According to the scheme, based on a shortcut nitrification autotrophic nitrogen removal system, through free ammonia ectopic treatment and intermittent aeration dissolved oxygen control in the main reactor, stable and controllable nitrite accumulation can be established, and meanwhile, synchronous removal of organic micropollutants and antibiotic resistance genes can be achieved. By combining ectopic treatment and dissolved oxygen control, the common problems that a short-cut nitrification system is unstable, nitrite accumulation fails and the like can be effectively solved, and different nitrite accumulation rates can be achieved by adjusting the concentration of free ammonia used for ectopic treatment; the method has good applicability to different water qualities such as urban domestic sewage and high-concentration livestock and poultry wastewater, and can provide reference and support for biological denitrification of sewage and synchronous removal of organic micropollutants and resistance genes.

Description

Technical Field

[0001] This invention relates to wastewater biological treatment technology, specifically a method for simultaneously removing organic micropollutants and resistance genes based on short-cut nitrification and denitrification. Background Technology

[0002] In recent decades, biological nitrogen removal has become a crucial component of all biological wastewater treatment processes. Wastewater treatment plants commonly employ traditional biological nitrogen removal technologies, namely nitrification-denitrification, a method that utilizes nitrifying and denitrifying bacteria to gradually convert ammonia nitrogen in wastewater into nitrite, nitrate, and finally nitrogen gas. However, while traditional nitrification-denitrification technologies are mature and perform well, they face challenges due to high operating costs and carbon emissions. Therefore, developing novel biological nitrogen removal processes has become a major focus for the scientific community, government, and the public. Among numerous novel biological nitrogen removal processes, autotrophic nitrogen removal processes based on short-cut nitrification offer several advantages, including reduced aeration and carbon source requirements, reduced excess sludge production, shorter reaction times, and reduced reactor volume, making them one of the most feasible solutions for upgrading and retrofitting biological nitrogen removal processes in wastewater treatment plants.

[0003] One of the challenges in researching novel biological nitrogen removal technologies based on short-cut nitrification lies in achieving stable nitrite accumulation. This requires stopping nitrification at the nitrite oxidation stage, i.e., retaining the activity of ammonia-oxidizing bacteria (AOB) while selectively inhibiting nitrite-oxidizing bacteria (NOB). However, due to the long-term coexistence of AOB and NOB in the sludge system, and even physical contact forming a mixture, the nitrite generated by AOB is usually rapidly oxidized to nitrate by NOB. This makes it difficult to selectively inhibit / inactivate NOB and achieve stable short-cut nitrification, which is a major bottleneck for the further promotion and application of novel biological nitrogen removal processes based on short-cut nitrification.

[0004] Wastewater treatment plants are also significant sources and sinks of organic micropollutants and antibiotic resistance genes (ARGs). Conventional wastewater treatment processes have limited removal capacity for organic micropollutants, resulting in the long-term presence of large amounts of these pollutants within the wastewater treatment system. The stress from organic micropollutants, the abundance of carbon and nitrogen nutrients in wastewater, and the complex microbial networks provide an ideal environment for the spread of ARGs, further leading to their replication and proliferation in the environment. This has made antibiotic resistance one of the top ten environmental problems globally, and one of the greatest threats to global health, food security, and development.

[0005] Currently, traditional biological wastewater denitrification processes have limited effectiveness in removing organic micropollutants (ABMs) and ARGs, primarily relying on methods such as ultraviolet disinfection, liquid chlorine disinfection, and advanced oxidative degradation for enhanced removal. Previous studies have reported that short-cut nitrification denitrification functional microorganisms (AOBs) possess a certain co-metabolic degradation capacity for ABMs and are also important hosts for various ARGs. However, current wastewater biological treatment processes do not pay sufficient attention to the simultaneous co-metabolic degradation of ABMs and ARG reduction led by AOBs, and there is a lack of technological development for the simultaneous removal of ABMs and ARGs in short-cut nitrification denitrification systems. How to select appropriate operating strategies and process parameters to achieve simultaneous removal of ABMs and ARGs while ensuring stable short-cut nitrification denitrification remains a subject for further research and exploration. Summary of the Invention

[0006] To address the aforementioned technical problems and shortcomings, this invention provides a method for simultaneously removing organic micropollutants and ARGs based on short-cut nitrification. This method involves treating sludge in situ, returning it to the main reactor, and controlling the operating conditions to significantly reduce the concentration of organic micropollutants and the relative abundance of ARGs in the effluent microbial community while stabilizing nitrite accumulation.

[0007] To achieve the above objectives, the present invention specifically includes the following steps:

[0008] Step 1: Take activated sludge from the municipal wastewater treatment plant and inoculate it into the sequencing batch reactor.

[0009] Step 2: The main reactor operates according to the set operating cycle (influent, aerobic mixing, sedimentation, effluent discharge, and idle).

[0010] Step 3: After the aerobic mixing reaction is completed, the mud-water mixture in the main reactor is taken out in a fixed ratio for 24 hours of ex-situ free ammonia treatment, and then returned to the main reactor.

[0011] Preferably, the activated sludge inoculated in step 1 should be activated sludge from the aerobic tank of a conventional wastewater treatment plant, and the concentration should be between 3000-4000 mg / L.

[0012] Preferably, the operating cycle in the main reactor in step 2 is set as follows: 5 min for water inlet, 480 min for aerobic mixing, 110 min for sedimentation, 5 min for drainage, and 120 min for idle.

[0013] Preferably, during the operation of the main reactor in step 2, the temperature should be controlled at 21-25℃ and the pH should be controlled at 7.6-8.

[0014] Preferably, in the aerobic mixing stage of the main reactor in step 2, the dissolved oxygen is controlled within the range of 1.0-1.5 mg / L by intermittent aeration, and a stirrer is used to achieve the mud-water mixture with a stirring rate of 220 r / min.

[0015] Preferably, in step 2, during the drainage stage of the main reactor, the same amount of effluent is discharged according to the influent flow rate, and the hydraulic retention time is controlled to be 12 hours; during the idle stage, no sludge is discharged to maximize the enrichment of ammonia-oxidizing bacteria, and the sludge age is controlled to be approximately 28-30 days.

[0016] Preferably, in step 3, at the end of aerobic mixing, 1 / 4 of the mud-water mixture is taken for ex-situ treatment.

[0017] Preferably, the ex-situ treatment in step 3 is as follows: the extracted mud-water mixture is centrifuged and concentrated, then added to a separate flowmeter reactor, and ammonium chloride (concentration of 500 mg NH3-N / L) and sodium hydroxide (10 mol / L) are added to control the pH in the flowmeter reactor at 8.9 and the temperature at 21 ± 1 °C. Through the above operations, the free ammonia level in the flowmeter reactor is maintained at 130 mg NH3-N / L.

[0018] Preferably, during the flow reactor treatment, a stirrer is used to thoroughly mix the mud-water mixture at a controlled rate of 250 r / min. After mixing, the mud-water mixture is washed with deionized water, centrifuged, and then returned to the main reactor.

[0019] This invention proposes for the first time that, in a short-cut nitrification autotrophic denitrification system, by using ex-situ treatment of free ammonia and intermittent aeration dissolved oxygen control in the main reactor, stable and controllable nitrite accumulation can be established while simultaneously removing organic micropollutants (ARGs). The beneficial effects of this invention include:

[0020] (1) This invention achieves stable nitrite accumulation in the main reactor (accumulation rate can reach up to 90%) through free ammonia ex-situ treatment and dissolved oxygen control, thereby providing a stable nitrite supply for autotrophic denitrification;

[0021] (2) While achieving stable nitrite accumulation, the present invention can effectively remove organic micropollutants and resistance genes in the effluent. The removal rate of representative organic micropollutants exceeds 60%, and the total abundance of resistance genes (RPKM) is reduced from 63114 to 62385. Furthermore, eight of the top 10 ARGs in relative abundance show significant reduction.

[0022] (3) The combination of ex-situ treatment and dissolved oxygen control proposed in this invention can effectively overcome common problems such as instability of short-range nitrification systems and failure of nitrite accumulation. Different nitrite accumulation rates can be achieved by adjusting the free ammonia concentration used in ex-situ treatment. It has good applicability to different water qualities such as urban domestic sewage and high-concentration livestock and poultry wastewater. It can provide reference and support for biological denitrification of sewage and simultaneous removal of organic micropollutants and resistance genes. Attached Figure Description

[0023] Figure 1 Inorganic nitrogen concentration in the effluent during operation of a short-cut nitrification reactor;

[0024] Figure 2 Abundance of microbial genera and species in short-cut nitrification reactors;

[0025] Figure 3 Removal of organic micropollutants in a short-cut nitrification reactor;

[0026] Figure 4 Comparison of the abundance of major ARGs in short-path nitrification reactors;

[0027] Figure 5 Schematic diagram of a laboratory-scale reaction apparatus. Detailed Implementation

[0028] Example 1: Establishing a stable short-cut nitrification system through free ammonia ex-situ treatment and dissolved oxygen control.

[0029] This embodiment provides a method for acclimatizing seed mud through ex-situ treatment of free ammonia and control of dissolved oxygen, enriching ammonia-oxidizing bacteria while selectively inhibiting nitrite-oxidizing bacteria, thereby achieving stable and controllable nitrite accumulation. The specific method of this embodiment is as follows:

[0030] Step 1: Obtain seed activated sludge (concentration of approximately 3000-4000 mg / L MLSS) from a municipal wastewater treatment plant and inoculate it into the main reactor.

[0031] Step 2: The main reactor operates according to the set operating cycle (influent, aerobic mixing, sedimentation, drainage, and idle). During the influent stage, a peristaltic pump adds 1.5L of synthetic wastewater to the 4L main reactor within 5 minutes. During the aerobic mixing stage, an air pump and agitator thoroughly mix the sludge-water mixture, controlling the dissolved oxygen at 1.0 mg / L and the stirring rate at 200 rpm / min. After aerobic mixing, one-quarter of the sludge-water mixture (approximately 900 mL) is removed for ex-situ treatment. This is followed by a 110-minute sedimentation stage, a 5-minute drainage stage (1.5L drainage), and a 120-minute idle stage.

[0032] Step 3: The extracted sludge-water mixture undergoes ex-situ treatment: First, the mixture is centrifuged at 5000 rpm for 10 min, the supernatant is removed, and the solution is concentrated to 100 mL. Then, the concentrated sludge is added to a flow metering reactor with a pH of 8.9 and a concentration of 0.5 g NH3–N / L (equivalent to a FA concentration of 130 mg NH3–N / L) for 24 hours. After treatment, the sludge-water mixture in the flow metering reactor is centrifuged and repeatedly rinsed with deionized water until all NH3 is removed. Finally, the treated sludge is resuspended in 500 mL of deionized water and returned to the FA reactor.

[0033] Using the method described in this embodiment, 1.5L of synthetic wastewater was treated, and after stabilization, the ammonia nitrogen removal rate exceeded 97%, and the nitrite accumulation rate reached a maximum of 88.02±0.37%. Figure 1 Furthermore, by combining free ammonia treatment with dissolved oxygen control, the proliferation of nitrite-oxidizing bacteria was effectively inhibited, reducing their relative abundance by more than 90%, while the abundance of ammonia-oxidizing bacteria reached more than 15%. Figure 2 In subsequent operation, the inhibition of nitrite-oxidizing bacteria and the nitrite accumulation rate can be controlled by adjusting the concentration of free ammonia used, so as to meet the appropriate concentration for denitrification or anaerobic ammonia oxidation.

[0034] Example 2 establishes a method to simultaneously remove organic micropollutants and resistance genes while performing short-range nitrification.

[0035] This embodiment provides a method for simultaneously removing organic micropollutants and resistance genes while completing short-cut nitrification using enriched short-cut nitrifying sludge. In this embodiment, the removal capacity of the short-cut nitrifying sludge for organic micropollutants and resistance genes was evaluated. The wastewater used in this embodiment had an ammonia nitrogen concentration of 50 mg / L and contained 5 mg / L of the antibiotic sulfamethoxazole (SMX). The specific method includes the following steps:

[0036] Step 1: Inoculate the enriched short-cut nitrification sludge into the reactor at a concentration of approximately 1000 mg / L.

[0037] Step 2: The main reactor operates according to the set operating cycle (influent, aerobic mixing, sedimentation, drainage, and idle). During the influent stage, a peristaltic pump adds 0.5L of synthetic wastewater to the 2L working volume main reactor within 5 minutes. During the aerobic mixing stage, an air pump and agitator thoroughly mix the sludge-water mixture, controlling the dissolved oxygen at 1.0-1.5 mg / L, with a stirring rate of 200 rpm / min. This is followed by a 110-minute sedimentation stage, a 5-minute drainage stage (1.5L drainage), and a 120-minute idle stage.

[0038] Step 3: After aerobic mixing, samples of the mud-water mixture are collected to detect the concentration of organic micropollutants and the abundance of resistance genes.

[0039] Following the steps described above, the experimental results of this embodiment are as follows:

[0040] Table 1. Removal of organic micropollutants sulfamethoxazole (SMX) and bisphenol A (BPA) during a typical operating cycle.

[0041] 0h 2h 4h 6h 8h SMX (mg / L) 5.0 2.81±0.11 2.13±0.04 1.61±0.08 1.48±0.16 BPA (mg / L) 5.0 4.41±0.08 3.37±0.05 2.67±0.09 2.02±0.02

[0042] The results showed that the enriched short-cut nitrification sludge exhibited significant removal capabilities for representative organic micropollutants, the antibiotics sulfamethoxazole (SMX) and bisphenol A (BPA), with removal rates reaching 69% for sulfamethoxazole and 59% for BPA. Further analysis indicated that the enriched short-cut nitrification sludge primarily removed sulfamethoxazole through degradation, contributing over 70% of the total removal rate; while the removal of BPA involved a combination of adsorption and degradation.

[0043] The abundance of antibiotic resistance genes in short-cut nitrification sludge was further evaluated compared to fully nitrified sludge. (See attached image.) Figure 4 As shown, among the top ten ARGs in terms of relative abundance, only fabG and mlaF showed higher abundance in short-cut nitrification sludge, while the others were significantly reduced.

Claims

1. A method for simultaneous removal of organic micropollutants and resistance genes based on short-cut nitrification autotrophic denitrification, characterized in that, Comprising the following steps: (1) Take activated sludge from a municipal sewage treatment plant and inoculate it into a sequencing batch main reactor; (2) The main reactor is operated according to the set operating cycle (influent, aerobic mixing, sedimentation, effluent and idle); (3) After the end of the aerobic mixing reaction, take out the sludge-water mixture in the main reactor according to a fixed proportion for 24h of ex-situ free ammonia treatment, and then return it to the main reactor.

2. A method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, The activated sludge inoculated in step (1) should be the activated sludge of the aerobic tank of a conventional sewage treatment plant, and the concentration should be 3000-4000mg / L.

3. A method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, In step (2), the operating cycle of the main reactor is set to 5min of influent, 480min of aerobic mixing, 110min of sedimentation, 5min of effluent and 120min of idle.

4. The method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, In step (2), the temperature of the main reactor should be controlled at 21-25℃, and the pH should be controlled at 7.6-8.

5. The method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, In the aerobic mixing stage of the main reactor in step (2), the dissolved oxygen is controlled in the range of 1.0-1.5mg / L by intermittent aeration, and the sludge-water mixture is realized by using a stirrer at a stirring rate of 220r / min.

6. The method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, In the effluent stage of the main reactor in step (2), the same effluent quantity is discharged according to the influent quantity, and the hydraulic retention time is controlled at 12h; In the idle stage, no sludge is discharged to maximize the enrichment of ammonia-oxidizing bacteria, and the sludge age is controlled at about 28-30 days.

7. The method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, In step (3), 1 / 4 of the sludge-water mixture is taken out for ex-situ treatment at the end of the aerobic mixing.

8. The method for preparing a peracetic acid activator based on residual activated sludge liquid phase according to claim 1 and its application, characterized in that, In step (3), the ex-situ treatment method is as follows: The taken sludge-water mixture is concentrated by centrifugation, then added into a separate flow reactor, and ammonium chloride (concentration of 500mg NH3-N / L) is added, sodium hydroxide (10mol / L) is added to control the pH of the flow reactor to 8.9, and the temperature is controlled at 21±1℃. Through the above operation, the free ammonia level in the flow reactor is controlled at 130mg NH3-N / L.

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