Method for detoxification of perfluorooctanoic acid stress in biological treatment of sewage using quaternary ammonium salt

Abstract

The application provides a method for detoxifying perfluorooctanoic acid stress in sewage biological treatment by using a quaternary ammonium salt; the method comprises the following steps: adding liquid alkali to an activated sludge reaction tank impacted by perfluorooctanoic acid, adjusting the pH value of sewage to 7.4-8.2, then putting a detoxifying agent into the activated sludge reaction tank for detoxification treatment, recovering the activated sludge after the detoxification treatment, and performing cleaning treatment on the recovered activated sludge at least once, and then evaluating the detoxification effect based on nitrification performance activity and oxidation stress indexes. The application provides a method for detoxifying perfluorooctanoic acid stress in sewage biological treatment by using a quaternary ammonium salt; the detoxification method uses the quaternary ammonium salt as the main component of a nitrifying sludge detoxifying agent, and can effectively alleviate the toxicity of perfluorooctanoic acid to nitrifying sludge by being directly added into sewage or by adding a detoxification regeneration tank.

Description

Technical Field

[0001] The present invention relates to the technical field of biological treatment of urban sewage, and in particular to a detoxification method for perfluorooctanoic acid stress in biological sewage treatment using quaternary ammonium salts. The method is suitable for alleviating the toxicity of perfluorooctanoic acid on nitrification performance in sewage treatment plants under short-term impact or long-term exposure to perfluorooctanoic acid. Background Art

[0002] Perfluoroalkyl compounds (PFAs) are a class of persistent organic pollutants (POPs) composed of hydrophobic perfluoroalkyl chains and hydrophilic functional groups. PFOA is one of the most widely detected POAs in the environment. Due to its excellent surface activity and stability, it is widely used in a variety of agricultural, domestic, and industrial applications, including pesticides, textiles, personal care products, non-stick coatings, and firefighting foams. The high-energy carbon-fluorine bond also imparts PFOA with high chemical and thermal stability, making it extremely difficult to degrade naturally in the environment, earning it the nickname "forever chemical." PFOA has been widely detected in water, soil, and the human body, and its adverse effects on organisms range from neurotoxicity to reproductive toxicity to immunotoxicity. The environmental accumulation and bio-health issues caused by PFOA are currently attracting attention from the global environmental protection community. Wastewater treatment plants are one of the most serious sites of PFOA contamination, and their biological treatment performance is directly affected by PFOA. PFOA exposure significantly increases the levels of reactive oxygen species (ROS) in activated sludge bacteria, causing severe oxidative damage to cell membranes and DNA, leading to cell inactivation or death. It's worth noting that wastewater discharged from some fluorine chemical plants and fire stations contains levels of PFOA exceeding 5 mg / L. High concentrations of PFOA can be fatal to wastewater treatment plants' biochemical treatment units, causing sludge bulking and even reactor collapse. Furthermore, PFOA, as an end-product of the biodegradation of many long-chain perfluorinated compounds, exacerbates its toxic effects.

[0003] Existing research methods for addressing PFOA-stressed wastewater during biological treatment mostly employ modified activated carbon adsorbents or bioaugmentation agents. Bioaugmentation agents primarily include degrading bacteria and functional resistance bacteria. Zhou Lulu et al. domesticated and enriched soil bacteria contaminated with perfluorinated compounds using an inorganic salt culture medium with PFOA as the sole carbon source, and isolated two PFOA-degrading fungi, initially identified as Trichoderma asperellum and Mucor circinelloides. Chinese patent application number CN201910574811.5 discloses a multifunctional Lactobacillus fermentum CCFM1051, which mitigates the toxic effects of PFOA, as well as fermented foods and applications. This technology demonstrates that Lactobacillus fermentum CCFM1051 can be used to enhance organisms' resistance to PFOA. However, bioaugmentation agents currently suffer from low degradation efficiency, difficulty in genetic breeding, and demanding environmental requirements. Activated carbon raw materials are widely available, low-cost, and non-toxic. However, the modification process is complex, and practical applications require the construction of activated carbon tanks or adsorption towers for recycling and regeneration. This presents challenges such as high technical requirements and high economic costs. Therefore, there is an urgent need to find a safe, non-toxic, and easy-to-use method that can effectively and promptly address the impact of PFOA, protect the nitrification activity of activated sludge, and effectively address the impact of PFOA.

[0004] For this reason, the invention provides a detoxification method utilizing quaternary ammonium salt to perfluorooctanoic acid (PFOA) stress in sewage biological treatment, and this detoxification method utilizes quaternary ammonium salt as the main component of nitrification sludge detoxifier, by directly being added in sewage or adding detoxification regeneration pool, can effectively alleviate the poisoning of PFOA to nitrification sludge.Wherein, quaternary ammonium salt is a kind of cationic surfactant, often used as preservative and / or antibacterial agent and is applied to the field of personal care products.According to statistics, the addition of quaternary ammonium salt is about 20g / L in laundry detergent, and quaternary ammonium salt content is about 1g / L in skin and mucous membrane wound disinfectant, and the usage amount of quaternary ammonium salt in the present invention is far less than the usage amount of these commodities, therefore, the invention provides a kind of relatively safe and reliable detoxifier.In addition, Yuan Chen found when studying the usefulness and mechanism of PFOA in groundwater adsorption by quaternary ammonium salt modified activated carbon, by modifying activated carbon coupling quaternary ammonium salt to increase surface positive charge quantity, can be used to improve the adsorption capacity of activated carbon to perfluorooctanoic acid in aqueous solution. However, the present invention utilizes electrostatic adsorption between quaternary ammonium salts and bacteria in nitrifying sludge by adjusting conditions and optimizing dosing methods, thereby isolating the bacteria from PFOA. This fundamentally differs from Yuan Chen's previous research in principle. The detoxification method provided by the present invention can be applied to municipal wastewater treatment plants subjected to firefighting foam impacts, or to wastewater leaks in photolithography, textile, papermaking, coatings, and other industries, where high concentrations of PFOA are constantly being treated. It can mitigate PFOA toxicity and protect sludge nitrification performance, providing a new approach and strategy for ensuring the sustained and stable operation of wastewater treatment systems. Summary of the Invention

[0005] Based on this, it is necessary to provide a detoxification method for perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts to address the above technical problems. This detoxification method can alleviate the toxicity of perfluorooctanoic acid on nitrification performance in urban sewage treatment plants under short-term shock or long-term exposure conditions.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts comprises the following steps:

[0008] Liquid alkali is added to the activated sludge reaction tank impacted by perfluorooctanoic acid, and the pH value of the sewage is adjusted to 7.4-8.2. Then, an antidote is added to the activated sludge reaction tank for detoxification treatment, and the activated sludge after detoxification treatment is recovered. The recovered activated sludge is cleaned at least once, and the detoxification effect is evaluated based on nitrification performance activity and oxidative stress indicators; wherein the antidote is composed of a quaternary ammonium salt and sodium carbonate in a molar ratio of 1:1. When the antidote is added, the concentration of the quaternary ammonium salt is 1.5-3 times the concentration of perfluorooctanoic acid, and the liquid alkali is a 9% mass fraction sodium carbonate solution.

[0009] In some embodiments, the quaternary ammonium salt is dodecyl dimethylbenzyl ammonium chloride (DDBAC).

[0010] In some embodiments, the duration of the detoxification treatment is ≥ 48 h.

[0011] In some embodiments, the concentration of perfluorooctanoic acid in the activated sludge reaction tank subjected to perfluorooctanoic acid shock is ≤2.2 mg perfluorooctanoic acid / g MLSS.

[0012] In some embodiments, the activated sludge reaction tank comprises a sequencing batch system or a continuous flow system.

[0013] In some embodiments, the sequencing batch system is a sequencing batch reactor, and the detoxification process for the sequencing batch reactor includes:

[0014] Step 10: Heat the heating tube of the sequencing batch reactor and maintain it at 20-25°C;

[0015] Step 11: After continuously injecting perfluorooctanoic acid into the sequencing batch reactor for perfluorooctanoic acid shock, the sequencing batch reactor is aerated using an aeration device to raise the dissolved oxygen concentration in the aeration stage to 2-7 mg / L;

[0016] Step 12: Adding liquid caustic soda to the sequencing batch reactor subjected to the perfluorooctanoic acid shock to adjust the wastewater pH to 7.4-8.2, and then adding an antidote to the influent according to the reaction cycle, and adding the antidote three times at equal time intervals within the reaction cycle for detoxification treatment;

[0017] Step 13: Recover the activated sludge after detoxification treatment according to the preset detection time, clean the recovered activated sludge at least once, perform SV30 detection, and then evaluate the detoxification effect based on nitrification performance activity and oxidative stress indicators.

[0018] In some embodiments, in step 12, the detoxification treatment is performed by adding an antidote to the influent water three times at equal time intervals during the reaction period, specifically including:

[0019] When the concentration of perfluorooctanoic acid in a sequencing batch reactor subjected to perfluorooctanoic acid shock is ≤1.5mg perfluorooctanoic acid / gMLSS, within 0-30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be twice the current perfluorooctanoic acid concentration; 30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 1.5-2 times the current perfluorooctanoic acid concentration, until the shock ends;

[0020] When the concentration of perfluorooctanoic acid in a sequencing batch reactor subjected to perfluorooctanoic acid shock is 1.5-2.2 mg perfluorooctanoic acid / g MLSS, within 0-30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid; 30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 2.5-3 times the current concentration of perfluorooctanoic acid, until the shock ends.

[0021] In some embodiments, in step 13, the preset detection time is 2 days.

[0022] In some embodiments, the continuous flow system includes a sewage storage tank, an anaerobic tank, an aeration tank and a sedimentation tank connected to each other. The input end of the sewage storage tank is also connected to a sodium carbonate solution storage tank through a connecting pipe. A sodium carbonate solution dosing pump is provided on the connecting pipe between the sodium carbonate solution storage tank and the sewage storage tank. The continuous flow system also includes an antidote storage tank. The antidote storage tank has three output ends, each of which is connected to the input end of the anaerobic tank, the end input end of the aeration tank and the aeration tank through a connecting pipe. The middle input end is connected, a first antidote dosing pump is provided on the connecting pipe between the antidote reserve water tank and the anaerobic tank, a second antidote dosing pump is provided on the connecting pipe between the antidote reserve water tank and the end input end of the aeration tank, and a third antidote dosing pump is provided on the connecting pipe between the antidote reserve water tank and the middle input end of the aeration tank. The output end of the sedimentation tank is also connected to the input end of the anaerobic tank through a connecting pipe. The anaerobic tank is also provided with a stirring device. The bottom of the aeration tank is connected to an aeration device through a connecting pipe.

[0023] The detoxification process for continuous flow systems includes:

[0024] Step 20: Add liquid caustic soda to the wastewater storage tank impacted by PFOA to adjust the pH value of the wastewater to 7.4-8.2;

[0025] Step 21: The antidote stored in the antidote reserve tank is continuously and evenly added to the anaerobic tank and the aeration tank through the connecting pipes. Within 48 hours after the sewage reserve tank is subjected to the shock of perfluorooctanoic acid, when the antidote is added to the influent of the anaerobic tank and the aeration tank, the concentration of the quaternary ammonium salt is ensured to be 1-3 times the current concentration of perfluorooctanoic acid in the anaerobic tank or the aeration tank; 48 hours after the sewage reserve tank is subjected to the shock of perfluorooctanoic acid, when the antidote is added to the influent of the anaerobic tank and the aeration tank, the concentration of the quaternary ammonium salt is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid in the anaerobic tank or the aeration tank, until the shock is completed;

[0026] Step 22: Recover the activated sludge in the aeration tank every two days, conduct an SV30 test, and adjust the sedimentation time of the sedimentation tank based on the test results;

[0027] Step 23: Recover the activated sludge in the aeration tank, clean the recovered activated sludge at least once, and then evaluate the detoxification effect based on nitrification activity and oxidative stress indicators.

[0028] In some embodiments, the continuous flow system includes a sewage storage water tank, an anaerobic tank, an aeration tank and a sedimentation tank that are interconnected. The input end of the sewage storage water tank is also connected to a sodium carbonate solution storage water tank through a connecting pipe. A sodium carbonate solution dosing pump is provided on the connecting pipe between the sodium carbonate solution storage water tank and the sewage storage water tank. The continuous flow system also includes an antidote storage water tank and a detoxification regeneration tank. The output end of the antidote storage water tank is connected to the input end of the detoxification regeneration tank through a connecting pipe. A fourth antidote dosing pump is provided on the connecting pipe between the antidote storage water tank and the detoxification regeneration tank. The output end of the sedimentation tank is also connected to the input end of the anaerobic tank through a connecting pipe. A return sludge replacement pipe connected to the detoxification regeneration tank is also provided on the connecting pipe between the sedimentation tank and the anaerobic tank. The output end of the sedimentation tank is also connected to the input end of the detoxification regeneration tank through a residual sludge transfer channel. The detoxification regeneration tank and the anaerobic tank are also provided with a stirring device. The bottom of the aeration tank is connected to an aeration device through a connecting pipe.

[0029] The detoxification process for continuous flow systems includes:

[0030] Step 30: Add liquid caustic soda to the wastewater storage tank impacted by PFOA to adjust the pH value of the wastewater to 7.4-8.2;

[0031] Step 31: Recover the activated sludge in the aeration tank every two days to conduct an SV30 test, and adjust the sedimentation time of the sedimentation tank according to the test results;

[0032] Step 32: The activated sludge in the sedimentation tank is transferred to the detoxification and regeneration tank through the excess sludge transfer channel, and then the detoxifier stored in the detoxifier reserve tank is continuously and evenly added to the detoxification and regeneration tank through the connecting pipe. When adding the detoxifier to the detoxification and regeneration tank, the concentration of the quaternary ammonium salt is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid in the detoxification and regeneration tank, and the detoxifier is continuously stirred and operated for 48 hours at 20-25°C.

[0033] Step 33: After the activated sludge in the detoxification and regeneration tank has been detoxified for 48 hours, it is replaced with an equal amount of activated sludge in the sedimentation tank through the return sludge replacement pipeline and transported to the anaerobic tank. At the same time, the activated sludge in the sedimentation tank that enters the detoxification and regeneration tank through the return sludge replacement pipeline continues to be detoxified according to step 32;

[0034] Step 34: Repeat step 33 until the continuous flow system adapts to the shock or the shock ends;

[0035] Step 35: Recover the activated sludge in the aeration tank, clean the recovered activated sludge at least once, and then evaluate the detoxification effect based on nitrification activity and oxidative stress indicators.

[0036] In some embodiments, the present invention relates to a method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts, and the principle of detoxification is as follows:

[0037] The detoxifier is composed of a quaternary ammonium salt and sodium carbonate in a molar ratio of 1:1. The positively charged quaternary ammonium salt contained in the detoxifier can play a dominant adsorption driving force between the quaternary ammonium salt and the activated sludge due to its strong electrostatic force. At the same time, it has the advantages of stronger adsorption force and larger adsorption capacity. The adsorption force between the activated sludge and the negatively charged perfluorooctanoic acid is mainly through hydrophobic interaction, which has the problem of weak adsorption force. Therefore, the quaternary ammonium salt in the detoxifier can more quickly combine with the activated sludge through the quaternary ammonium group. At the same time, the hydrophobic group on the other end can also preferentially occupy a large number of hydrophobic sites on the surface of the activated sludge cells, resulting in a significant reduction in the sites that perfluorooctanoic acid can occupy on the surface of the activated sludge cells. The perfluorooctanoic acid that is not adsorbed on the surface of the activated sludge cells can be discharged with the effluent, thereby reducing its toxic effects. In addition, the sublethal concentration of quaternary ammonium salt in the sewage environment has very limited damage to the activated sludge cell membrane, which is relatively safe and reliable.

[0038] Furthermore, the detoxification method of the present invention can reduce the oxidative stress damage caused by perfluorooctanoic acid, including the reduction of reactive oxygen species (ROS), malondialdehyde (MDA), and lactate dehydrogenase (LDH) in sludge.

[0039] Furthermore, the detoxification method of the present invention can alleviate the toxicity of perfluorooctanoic acid by adding quaternary ammonium salts, thereby restoring the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in activated sludge.

[0040] Furthermore, before adding the antidote, the sewage hardness needs to be adjusted to no more than 120 mg / L.

[0041] The advantages and beneficial effects of the present invention are:

[0042] The present invention provides a detoxification method for perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts. The detoxification method comprises adding an antidote composed of a quaternary ammonium salt and sodium carbonate in a molar ratio of 1:1. The quaternary ammonium salt in the antidote can more quickly combine with activated sludge through the quaternary ammonium group and preferentially occupy hydrophobic sites on the surface of activated sludge cells, resulting in a significant reduction in the sites that perfluorooctanoic acid can occupy on the surface of activated sludge cells, thereby achieving a detoxification effect. At the same time, the present invention is applicable to sequencing batch systems and continuous flow systems, can effectively alleviate the impact of perfluorooctanoic acid at a concentration not exceeding 2.2 mg perfluorooctanoic acid / g MLSS, has excellent stability and high efficiency, and can achieve a sustained mitigation effect using a low dose of the antidote, thereby being relatively safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A structural diagram of a continuous flow system.

[0044] Figure 2 Another structural diagram of a continuous flow system;

[0045] Figure 3 Schematic diagram of the activity of AOB in activated sludge after different treatments in five continuous flow systems in Example 1 of the present invention;

[0046] Figure 4 Schematic diagram of NOB activity in activated sludge after different treatments in five continuous flow systems in Example 1 of the present invention;

[0047] Figure 5 Schematic diagram of the ratio of MDA concentration in activated sludge after different treatments in five groups of continuous flow systems in Example 1 of the present invention to the MDA concentration in activated sludge in the control group;

[0048] Figure 6 Schematic diagram of the ratio of ROS concentration in activated sludge after different treatments of five continuous flow systems in Example 1 of the present invention to the ROS concentration in activated sludge of the control group;

[0049] Figure 7 Schematic diagram of the ratio of LDH concentration in activated sludge after different treatments of five groups of continuous flow systems in Example 1 of the present invention to the LDH concentration in activated sludge of the control group;

[0050] Figure 8 The control group in Example 2 of the present invention has NH4 in and out of the water for 84 consecutive days. + -N, NO2 - -N and NO3 - -N change graph;

[0051] Figure 9 The R1 in Example 2 of the present invention continuously fed and discharged NH4 for 84 days. + -N, NO2 - -N and NO3 - -N change graph;

[0052] Figure 10 The R2 in Example 2 of the present invention continuously fed and discharged NH4 for 84 days. + -N, NO2 - -N and NO3 - -N change graph;

[0053] Figure 11 Schematic diagram of the absolute contents of functional genes of AOB, Complete ammonia oxidizers (Comammox), Nitrobacter, and Nitrospira in activated sludge after 84 days of continuous treatment in the control group, R1, and R2 in Example 2 of the present invention;

[0054] Figure 12 This is the zeta potential diagram of the sludge adsorption on the control group, R1 and R2 in Example 2 of the present invention.

[0055] Figure numerals: sewage reserve water tank 1, anaerobic tank 2, aeration tank 3, sedimentation tank 4, sodium carbonate solution reserve water tank 5, antidote reserve water tank 6, detoxification regeneration tank 7, sodium carbonate solution dosing pump 51, antidote first dosing pump 61, antidote second dosing pump 62, antidote third dosing pump 63, antidote fourth dosing pump 64, return sludge replacement pipeline 71, residual sludge transfer channel 72. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0057] A method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts comprises the following steps:

[0058] Liquid alkali is added to the activated sludge reaction tank impacted by perfluorooctanoic acid, and the pH value of the sewage is adjusted to 7.4-8.2. Then, an antidote is added to the activated sludge reaction tank for detoxification treatment, and the activated sludge after detoxification treatment is recovered. The recovered activated sludge is cleaned at least once, and the detoxification effect is evaluated based on nitrification performance activity and oxidative stress indicators; wherein the antidote is composed of a quaternary ammonium salt and sodium carbonate in a molar ratio of 1:1. When the antidote is added, the concentration of the quaternary ammonium salt is 1.5-3 times the concentration of perfluorooctanoic acid, and the liquid alkali is a 9% mass fraction sodium carbonate solution.

[0059] In this embodiment, when subjected to long-term perfluorooctanoic acid impact, the concentration of the quaternary ammonium salt is twice the concentration of perfluorooctanoic acid.

[0060] In this embodiment, the detoxification method of the present invention is applicable to short-term impact or long-term exposure conditions of perfluorooctanoic acid.

[0061] In this embodiment, the quaternary ammonium salt is DDBAC.

[0062] In this embodiment, the duration of the detoxification treatment is ≥48h.

[0063] In this embodiment, the concentration of perfluorooctanoic acid in the activated sludge reaction tank subjected to perfluorooctanoic acid shock is ≤2.2 mg perfluorooctanoic acid / g MLSS.

[0064] In this embodiment, the activated sludge reaction tank includes a sequencing batch system or a continuous flow system.

[0065] In this embodiment, the sequencing batch system is a sequencing batch reactor, and the detoxification process of the sequencing batch reactor includes:

[0066] Step 10: Heat the heating tube of the sequencing batch reactor and maintain it at 20-25°C;

[0067] Step 11: After continuously injecting perfluorooctanoic acid into the sequencing batch reactor for perfluorooctanoic acid shock, the sequencing batch reactor is aerated using an aeration device to raise the dissolved oxygen concentration in the aeration stage to 2-7 mg / L;

[0068] Step 12: Adding liquid caustic soda to the sequencing batch reactor subjected to the perfluorooctanoic acid shock to adjust the wastewater pH to 7.4-8.2, and then adding an antidote to the influent according to the reaction cycle, and adding the antidote three times at equal time intervals within the reaction cycle for detoxification treatment;

[0069] Step 13: Recover the activated sludge after detoxification treatment according to the preset detection time, clean the recovered activated sludge at least once, perform SV30 detection, and then evaluate the detoxification effect based on nitrification performance activity and oxidative stress indicators.

[0070] In this embodiment, in step 12, an antidote is added to the influent water according to the reaction cycle, and the detoxification treatment is performed three times at equal time intervals within the reaction cycle, specifically including:

[0071] When the concentration of perfluorooctanoic acid in a sequencing batch reactor subjected to perfluorooctanoic acid shock is ≤1.5mg perfluorooctanoic acid / gMLSS, within 0-30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be twice the current perfluorooctanoic acid concentration; 30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 1.5-2 times the current perfluorooctanoic acid concentration, until the shock ends;

[0072] When the concentration of perfluorooctanoic acid in a sequencing batch reactor subjected to perfluorooctanoic acid shock is 1.5-2.2 mg perfluorooctanoic acid / g MLSS, within 0-30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid; 30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 2.5-3 times the current concentration of perfluorooctanoic acid, until the shock ends.

[0073] In this embodiment, in step 13, the preset detection time is 2 days.

[0074] In this embodiment, refer to the attached Figure 1The continuous flow system includes a sewage storage water tank 1, an anaerobic tank 2, an aeration tank 3 and a sedimentation tank 4 that are interconnected. The input end of the sewage storage water tank 1 is also connected to a sodium carbonate solution storage water tank 5 through a connecting pipe. A sodium carbonate solution dosing pump 51 is provided on the connecting pipe between the sodium carbonate solution storage water tank 5 and the sewage storage water tank 1. The continuous flow system also includes an antidote storage water tank 6. The antidote storage water tank 6 is provided with three output ends, each of which is connected to the input end of the anaerobic tank 2, the end input end of the aeration tank 3 and the middle output end of the aeration tank 3 through a connecting pipe. The inlet end is connected, a first antidote dosing pump 61 is provided on the connecting pipe between the antidote reserve water tank 6 and the anaerobic tank 2, a second antidote dosing pump 62 is provided on the connecting pipe between the antidote reserve water tank 6 and the end input end of the aeration tank 3, and a third antidote dosing pump 63 is provided on the connecting pipe between the antidote reserve water tank 6 and the middle input end of the aeration tank 3. The output end of the sedimentation tank 4 is also connected to the input end of the anaerobic tank 2 through a connecting pipe. The anaerobic tank 2 is also provided with a stirring device. The bottom of the aeration tank 3 is connected to an aeration device through a connecting pipe;

[0075] The detoxification process for continuous flow systems includes:

[0076] Step 20: adding liquid alkali to the sewage storage tank 1 impacted by perfluorooctanoic acid to adjust the pH value of the sewage to 7.4-8.2;

[0077] Step 21: The antidote stored in the antidote storage tank 6 is continuously and evenly added to the anaerobic tank 2 and the aeration tank 3 through the connecting pipes. Within 48 hours after the sewage storage tank 1 is subjected to the shock of perfluorooctanoic acid, when the antidote is added to the influent of the anaerobic tank 2 and the aeration tank 3, the concentration of the quaternary ammonium salt is ensured to be 1-3 times the current concentration of perfluorooctanoic acid in the anaerobic tank 2 or the aeration tank 3; 48 hours after the sewage storage tank 1 is subjected to the shock of perfluorooctanoic acid, when the antidote is added to the influent of the anaerobic tank 2 and the aeration tank 3, the concentration of the quaternary ammonium salt is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid in the anaerobic tank 2 or the aeration tank 3, until the shock ends;

[0078] Step 22: Recover the activated sludge in the aeration tank 3 every two days, conduct an SV30 test, and adjust the sedimentation time of the sedimentation tank 4 according to the test results;

[0079] Step 23: Recover the activated sludge in the aeration tank 3, perform at least one cleaning treatment on the recovered activated sludge, and then evaluate the detoxification effect based on the nitrification activity and oxidative stress indicators.

[0080] Furthermore, when the activated sludge in the aeration tank 3 recovered in step 22 was tested for SV30, it was found that within 48 hours after the stress occurred, the return sludge volume in the sedimentation tank 4 increased by 10%-20%; after 48 hours, the return sludge volume could be gradually restored to normal within no less than 72 hours, so that the sludge concentration in the continuous flow system returned to normal.

[0081] In this embodiment, refer to the attached Figure 2 The continuous flow system includes a sewage storage tank 1, an anaerobic tank 2, an aeration tank 3 and a sedimentation tank 4. The input end of the sewage storage tank 1 is also connected to a sodium carbonate solution storage tank 5 through a connecting pipe. A sodium carbonate solution dosing pump 51 is provided on the connecting pipe between the sodium carbonate solution storage tank 5 and the sewage storage tank 1. The continuous flow system also includes an antidote storage tank 6 and a detoxification regeneration tank 7. The output end of the antidote storage tank 6 is connected to the input end of the detoxification regeneration tank 7 through a connecting pipe. 6 and the detoxification and regeneration tank 7 is provided with a fourth detoxifier dosing pump 64, the output end of the sedimentation tank 4 is also connected to the input end of the anaerobic tank 2 through a connecting pipe, and a return sludge replacement pipe 71 connected to the detoxification and regeneration tank 7 is also provided on the connecting pipe between the sedimentation tank 4 and the anaerobic tank 2. The output end of the sedimentation tank 4 is also connected to the input end of the detoxification and regeneration tank 7 through a residual sludge transfer channel 72. The detoxification and regeneration tank 7 and the anaerobic tank 2 are also provided with a stirring device. The bottom of the aeration tank 3 is connected to an aeration device through a connecting pipe;

[0082] The detoxification process for continuous flow systems includes:

[0083] Step 30: adding liquid alkali to the sewage storage tank 1 impacted by perfluorooctanoic acid to adjust the pH value of the sewage to 7.4-8.2;

[0084] Step 31: Recover the activated sludge in the aeration tank 3 every two days to conduct an SV30 test, and adjust the sedimentation time of the sedimentation tank 4 according to the test results;

[0085] Step 32: The activated sludge in the sedimentation tank 4 is transported to the detoxification and regeneration tank 7 through the excess sludge transfer channel 72, and then the antidote stored in the antidote reserve water tank 6 is continuously and evenly added to the detoxification and regeneration tank 7 through the connecting pipe. When adding the antidote to the detoxification and regeneration tank 7, the concentration of the quaternary ammonium salt is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid in the detoxification and regeneration tank 7, and the stirring operation is continued for 48 hours at 20-25°C.

[0086] Step 33: After the activated sludge in the detoxification and regeneration tank 7 has been detoxified for 48 hours, it replaces an equal amount of activated sludge in the sedimentation tank 4 through the return sludge replacement pipe 71 and is transported to the anaerobic tank 2. At the same time, the activated sludge in the sedimentation tank 4 that enters the detoxification and regeneration tank 7 through the return sludge replacement pipe 71 continues to be detoxified according to step 32;

[0087] Step 34: Repeat step 33 until the continuous flow system adapts to the shock or the shock ends;

[0088] Step 35: Recover the activated sludge in the aeration tank 3, perform at least one cleaning treatment on the recovered activated sludge, and then evaluate the detoxification effect based on the nitrification activity and oxidative stress indicators.

[0089] The following will specifically describe the detoxification method for perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts provided by the present invention in conjunction with specific embodiments.

[0090] Example 1

[0091] Among the many biological denitrification processes, continuous flow reactors are currently more commonly used. This embodiment aims to achieve detoxification of municipal sewage treatment plants when subjected to short-term perfluorooctanoic acid shock. The seed sludge was taken from a flocculent sludge with nitrification activity in a municipal sewage treatment plant in Beijing. The water quality index of the synthetic sewage was NH4 + -N≈70mg / L, NO2 - -N≈28mg / L, PO4 3- -P≈5mg / L, COD≈250mg / L, Ca 2+ ≈40mg / L, Mg 2+ ≈4 mg / L. The antidote is prepared by mixing DDBAC and sodium carbonate in a molar ratio of 1:1.

[0092] Reference Attachment Figure 1The continuous flow system includes a connected sewage storage tank 1, an anaerobic tank 2, an aeration tank 3, and a sedimentation tank 4. The effective volumes of the anaerobic tank 2, the aeration tank 3, and the sedimentation tank 4 are 3L, 4L, and 4L, respectively, and the MLSS is 3500mg / L. In this embodiment, five identical continuous flow systems are set up, namely the control group, the inhibition group, Experiment No. 1, Experiment No. 2, and Experiment No. 3. The recovered activated sludge is cleaned three times to eliminate the interference of some impurities in the continuous flow system. The continuous flow system is continuously fed with water by a peristaltic pump; the internal reflow ratio is 250%; and the sludge reflow ratio is 80%. The inhibition group, Experiment No. 1, Experiment No. 2 and Experiment No. 3 were all subjected to continuous perfluorooctanoic acid shock, so that the perfluorooctanoic acid concentration in the continuous flow system was 2.5 mg / L; among them, Experiment No. 1, Experiment No. 2 and Experiment No. 3 were respectively added with antidote, so that the DDBAC concentration in the continuous flow system was 2.5 mg / L, 5 mg / L and 10 mg / L, respectively, and the anaerobic tank 2 was added at the water inlet, and the aeration tank 3 was added at the end inlet and the middle inlet, respectively; the control group was not subjected to perfluorooctanoic acid shock stress; the anaerobic tank 2 was uniformly stirred by a stirring device to ensure that the activated sludge and the antidote were fully mixed and contacted; the aeration tank 3 used an aeration device (such as an aeration pump) to provide dissolved oxygen and assist in stirring. After 48 hours of continuous perfluorooctanoic acid shock, 300 mL of sludge was taken from the aeration tank 3 of the five continuous flow systems. The activated sludge was washed three times with clean water to remove the residual antidote. The sludge was then aerated for 150 minutes (DO2-7 mg / L) to conduct nitrification performance activity test and oxidative stress index test.

[0093] The nitrification activity test method is as follows: AOB activity is determined according to the national standard HG / T 5748-2020. For the NOB bacterial activity test, 138 mg / L of NaNO2 is added to the test medium based on the national standard HG / T 5748-2020. A graph is plotted with the sampling time t (h) as the horizontal axis and the mass concentration of residual ammonia nitrogen and nitrite in the test solution and p (mg / L) (N) as the vertical axis. All other procedures are consistent with the standard, and NOB activity is calculated. Oxidative stress index testing methods are as follows: ROS is measured using the fluorescent probe DCFH-DA method; MDA is measured using the thiobarbituric acid colorimetric method; and LDH is measured using the lipoamide dehydrogenase catalytic colorimetric method.

[0094] Reference Attachment Figure 3-4 The results show that after 48 hours of exposure to 2.5 mg / L PFOA, the AOB and NOB activities in the activated sludge in the inhibition group were inhibited by 13.95% and 8.92%, respectively, compared to the control group. Furthermore, AOB and NOB activities in Experiments 1 and 2 increased compared to the inhibition group, while Experiment 3 exhibited a more severe inhibition effect.

[0095] Reference Attachment Figure 5-7As shown, after adding the antidote in Experiments 1 and 2, ROS, MDA, and LDH levels in the activated sludge exposed to PFOA were significantly reduced, but ROS levels slightly increased in Experiment 3. Therefore, controlling the antidote concentration to twice the PFOA concentration achieves optimal detoxification, while excessively high dosages can inhibit nitrification activity.

[0096] Example 2

[0097] This example aims to test the detoxification of municipal sewage treatment plants subjected to long-term exposure to PFOA.

[0098] This example uses synthetic sewage as influent, including milk powder, sucrose, starch, peptone, yeast extract, sodium acetate, NH4Cl, NaHCO3, KH2PO4, K2HPO4 and trace elements. The seed sludge is fully nitrified sludge. The water quality index of synthetic sewage is NH4 + -N is 65-80 mg / L, COD is 200-300 mg / L. The seed sludge was inoculated into an 8L sequencing batch reactor with a seed sludge concentration of 4000±200 mg / L. Three identical sequencing batch reactors were set up and named control group, R1 and R2. The activated sludge was recovered and washed three times before use to eliminate the interference of some impurities in the reactor. The sequencing batch reactor runs 4 reaction cycles per day with a drainage ratio of 50%. Each reaction cycle includes five stages: water inlet for 5 minutes, aeration for 150 minutes, sedimentation for 30 minutes, drainage for 5 minutes and idle for 170 minutes. Aeration was carried out using an aerator, the DO concentration was 2-7 mg / L, and the temperature was 20-25°C. Sodium carbonate solution was used to adjust the pH to 7.2-8.2. The three reactors of the control group, R1 and R2 were all set up with 3 stages, and each stage ran for 28 days. The control group was only added with antidote, and the concentration of DDBAC in the antidote was 0.2 mg / L, 4.0 mg / L and 10.0 mg / L at each stage; R1 was only added with PFOA, and the concentration at each stage was 0.1 mg / L, 2.0 mg / L and 5.0 mg / L; R2 was added with PFOA and antidote, and the concentrations of PFOA and DDBAC in the antidote were 0.1 mg / L and 0.2 mg / L, 2.0 mg / L and 4.0 mg / L, and 5.0 mg / L and 10.0 mg / L at each stage.

[0099] Reference Attachment Figure 8 It can be seen that in the control group, when only the antidote was added, the ammonia nitrogen removal rate in the sequencing batch reactor was almost unaffected, and the removal efficiency was always maintained at more than 95%, indicating that the antidote itself has a certain safety for the nitrification system.

[0100] Reference Attachment Figure 9-10It can be seen that in the first stage, due to the low concentration of perfluorooctanoic acid, the nitrification performance of R1 and R2 was not inhibited; but in the second stage, from the 36th day, R1 could not completely remove the ammonia nitrogen in the sequencing batch reactor, and its nitrification performance further deteriorated until the 42nd day. At this time, the ammonia nitrogen removal rate in the sequencing batch reactor reached a minimum of 50.9%. After R1 removed perfluorooctanoic acid, the ammonia nitrogen removal rate in the sequencing batch reactor recovered. It was not until the 50th day that the ammonia nitrogen removal rate in the sequencing batch reactor recovered to more than 90%; from the 51st day, the normal shock concentration of R1 was also restored. During the same period, R2 in the second stage did not show any inhibition in nitrification performance under exposure to the same concentration of PFOA due to the addition of antidote, and always maintained a good ammonia nitrogen removal effect; in the third stage, under high concentration of PFOA conditions, the ammonia nitrogen removal rates of R1 and R2 dropped sharply almost at the same time; but R2's ammonia nitrogen removal rate recovered to more than 95% after only 3 days, while R1 took 12 days to recover.

[0101] Reference Attachment Figure 11 It can be seen that after 84 days of operation, the three groups of reactors in this example showed that the R2 of AOB, full-process nitrifying bacteria, Nitrobacter and Nitrospira functional genes in the activated sludge was higher than R1. Therefore, it shows that the detoxifier can play a certain protective role on the nitrification functional genes in terms of genes.

[0102] In this example, by adding a specific concentration of antidote, the sequencing batch system was able to mitigate the inhibitory effects on nitrification performance across a wide range of PFOA concentrations, maintaining stable operation for 81 days. Therefore, this invention provides a method and approach for achieving sustained and stable operation of wastewater treatment systems subjected to long-term PFOA stress.

[0103] In addition, in order to clarify the difference in the adsorption of perfluorooctanoic acid and DDBAC by sludge, the present invention extracted EPS from the seed sludge in Example 2 and the activated sludge samples retained at the end of the third stage, and studied them using a zeta potential meter. Figure 12 As shown, the adsorption of the detoxifier (control group) caused the sludge potential to change by +15.71mv compared to the seed sludge (-3.55mv). The adsorption of PFOA (R1) caused the R1 reactor to change by -6.64mv, while the detoxification sludge (R2) reactor changed by +12.06mv. Obviously, the potential change of R2 was greater than the sum of the potential changes of the control group and R1 reactors. This indicates that in a multi-solute adsorption system, BAC, which has a competitive adsorption advantage, can reduce the adsorption of PFOA after neutralizing the potential reduction caused by PFOA on the sludge surface, thereby further improving the potential.

[0104] The above content is a further detailed description of the present invention in conjunction with specific embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts, characterized in that: The following steps are involved: Liquid caustic soda is added to an activated sludge reaction tank subjected to perfluorooctanoic acid shock to adjust the pH value of the sewage to 7.4-8.2, and then an antidote is added to the activated sludge reaction tank for detoxification treatment, the activated sludge after detoxification treatment is recovered, and the recovered activated sludge is cleaned at least once, and the detoxification effect is evaluated based on nitrification activity and oxidative stress indicators; wherein the antidote is composed of a quaternary ammonium salt and sodium carbonate in a molar ratio of 1:1, and when the antidote is added, the concentration of the quaternary ammonium salt is 1.5-3 times the concentration of perfluorooctanoic acid, and the liquid caustic soda is a 9% by mass sodium carbonate solution; The activated sludge reaction tank includes a sequencing batch system or a continuous flow system; The sequencing batch system is a sequencing batch reactor, and the detoxification process of the sequencing batch reactor includes: Step 10: Heat the heating tube of the sequencing batch reactor and maintain it at 20-25°C; Step 11: After continuously injecting perfluorooctanoic acid into the sequencing batch reactor for perfluorooctanoic acid shock, the sequencing batch reactor is aerated using an aeration device to raise the dissolved oxygen concentration in the aeration stage to 2-7 mg / L; Step 12: Adding liquid caustic soda to the sequencing batch reactor subjected to the perfluorooctanoic acid shock to adjust the wastewater pH to 7.4-8.2, and then adding an antidote to the influent according to the reaction cycle, and adding the antidote three times at equal time intervals within the reaction cycle for detoxification treatment; Step 13: Recover the activated sludge after detoxification treatment according to the preset detection time, clean the recovered activated sludge at least once, perform SV30 detection, and then evaluate the detoxification effect based on nitrification performance activity and oxidative stress indicators.

2. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: The quaternary ammonium salt is dodecyldimethylbenzyl ammonium chloride.

3. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: The duration of the detoxification treatment is ≥48h.

4. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: The concentration of perfluorooctanoic acid in the activated sludge reaction tank subjected to perfluorooctanoic acid shock is ≤2.2 mg perfluorooctanoic acid / g MLSS.

5. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: In step 12, an antidote is added to the influent water according to the reaction cycle, and the detoxification treatment is performed three times at equal time intervals within the reaction cycle, specifically including: When the concentration of perfluorooctanoic acid in a sequencing batch reactor subjected to perfluorooctanoic acid shock is ≤1.5 mg perfluorooctanoic acid / g MLSS, within 0-30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, add an antidote to the influent of the sequencing batch reactor, and ensure that the concentration of quaternary ammonium salt in the sequencing batch reactor is twice the current perfluorooctanoic acid concentration; 30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, add an antidote to the influent of the sequencing batch reactor, and ensure that the concentration of quaternary ammonium salt in the sequencing batch reactor is 1.5-2 times the current perfluorooctanoic acid concentration, until the shock ends; When the concentration of perfluorooctanoic acid in a sequencing batch reactor subjected to perfluorooctanoic acid shock is 1.5-2.2 mg perfluorooctanoic acid / gMLSS, within 0-30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid; 30 days after the sequencing batch reactor is subjected to perfluorooctanoic acid shock, an antidote is added to the influent of the sequencing batch reactor, and the concentration of quaternary ammonium salt added to the sequencing batch reactor is ensured to be 2.5-3 times the current concentration of perfluorooctanoic acid, until the shock ends.

6. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: In step 13, the preset detection time is 2 days.

7. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: The continuous flow system includes a sewage storage water tank, an anaerobic tank, an aeration tank and a sedimentation tank that are interconnected. The input end of the sewage storage water tank is also connected to a sodium carbonate solution storage water tank through a connecting pipe. A sodium carbonate solution dosing pump is provided on the connecting pipe between the sodium carbonate solution storage water tank and the sewage storage water tank. The continuous flow system also includes an antidote storage water tank. The antidote storage water tank is provided with three output ends, each of which is connected to the input end of the anaerobic tank, the end input end of the aeration tank and the middle output end of the aeration tank through a connecting pipe. The inlet end is connected, a first antidote dosing pump is provided on the connecting pipe between the antidote reserve water tank and the anaerobic tank, a second antidote dosing pump is provided on the connecting pipe between the antidote reserve water tank and the end input end of the aeration tank, and a third antidote dosing pump is provided on the connecting pipe between the antidote reserve water tank and the middle input end of the aeration tank. The output end of the sedimentation tank is also connected to the input end of the anaerobic tank through a connecting pipe. The anaerobic tank is also provided with a stirring device. The bottom of the aeration tank is connected to an aeration device through a connecting pipe; The detoxification process for continuous flow systems includes: Step 20: Add liquid caustic soda to the wastewater storage tank impacted by PFOA to adjust the pH value of the wastewater to 7.4-8.2; Step 21: The antidote stored in the antidote reserve tank is continuously and evenly added to the anaerobic tank and the aeration tank through the connecting pipes. Within 48 hours after the sewage reserve tank is subjected to the shock of perfluorooctanoic acid, when the antidote is added to the influent of the anaerobic tank and the aeration tank, the concentration of the quaternary ammonium salt is ensured to be 1-3 times the current concentration of perfluorooctanoic acid in the anaerobic tank or the aeration tank; 48 hours after the sewage reserve tank is subjected to the shock of perfluorooctanoic acid, when the antidote is added to the influent of the anaerobic tank and the aeration tank, the concentration of the quaternary ammonium salt is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid in the anaerobic tank or the aeration tank, until the shock is completed; Step 22: Recover the activated sludge in the aeration tank every two days, conduct an SV30 test, and adjust the sedimentation time of the sedimentation tank based on the test results; Step 23: Recover the activated sludge in the aeration tank, clean the recovered activated sludge at least once, and then evaluate the detoxification effect based on nitrification activity and oxidative stress indicators.

8. The method for detoxifying perfluorooctanoic acid stress in sewage biological treatment using quaternary ammonium salts according to claim 1, characterized in that: The continuous flow system includes a sewage storage water tank, an anaerobic tank, an aeration tank and a sedimentation tank that are interconnected. The input end of the sewage storage water tank is also connected to a sodium carbonate solution storage water tank through a connecting pipe. A sodium carbonate solution dosing pump is provided on the connecting pipe between the sodium carbonate solution storage water tank and the sewage storage water tank. The continuous flow system also includes an antidote storage water tank and a detoxification and regeneration tank. The output end of the antidote storage water tank is connected to the input end of the detoxification and regeneration tank through a connecting pipe. A fourth antidote dosing pump is provided on the connecting pipe between the antidote storage water tank and the detoxification and regeneration tank. The output end of the sedimentation tank is also connected to the input end of the anaerobic tank through a connecting pipe. A return sludge replacement pipe connected to the detoxification and regeneration tank is also provided on the connecting pipe between the sedimentation tank and the anaerobic tank. The output end of the sedimentation tank is also connected to the input end of the detoxification and regeneration tank through a residual sludge transfer channel. The detoxification and regeneration tank and the anaerobic tank are also provided with a stirring device. The bottom of the aeration tank is connected to an aeration device through a connecting pipe. The detoxification process for continuous flow systems includes: Step 30: Add liquid caustic soda to the wastewater storage tank impacted by PFOA to adjust the pH value of the wastewater to 7.4-8.2; Step 31: Recover the activated sludge in the aeration tank every two days to conduct an SV30 test, and adjust the sedimentation time of the sedimentation tank according to the test results; Step 32: The activated sludge in the sedimentation tank is transferred to the detoxification and regeneration tank through the excess sludge transfer channel, and then the detoxifier stored in the detoxifier reserve tank is continuously and evenly added to the detoxification and regeneration tank through the connecting pipe. When adding the detoxifier to the detoxification and regeneration tank, the concentration of the quaternary ammonium salt is ensured to be 1.5-2 times the current concentration of perfluorooctanoic acid in the detoxification and regeneration tank, and the detoxifier is continuously stirred and operated for 48 hours at 20-25°C. Step 33: After the activated sludge in the detoxification and regeneration tank has been detoxified for 48 hours, it is replaced with an equal amount of activated sludge in the sedimentation tank through the return sludge replacement pipeline and transported to the anaerobic tank. At the same time, the activated sludge in the sedimentation tank that enters the detoxification and regeneration tank through the return sludge replacement pipeline continues to be detoxified according to step 32; Step 34: Repeat step 33 until the continuous flow system adapts to the shock or the shock ends; Step 35: Recover the activated sludge in the aeration tank, clean the recovered activated sludge at least once, and then evaluate the detoxification effect based on nitrification activity and oxidative stress indicators.

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