Method for removing ARB and args from water using UV irradiation coupling in-situ chlorine production technology

Abstract

A method for removing ARB and ARGs from water using a UV irradiation coupling in-situ chlorine production technology, comprising: placing an electrode group comprising at least one pair of anode electrode and cathode electrode in water to be treated, wherein the anode electrode and the cathode electrode are respectively connected to a power supply, and said water contains chloride ions, ARB and / or ARGs; placing said water in the irradiation range of a UV lamp; connecting to the power supply to form an electric field between the anode electrode and the cathode electrode, so that the chloride ions in said water lose electrons on the surface of the anode electrode to generate Cl2, Cl2 continues to react with water or / and ammonia to generate HClO, ClO– or / and chloramine, and further, free chlorine is decomposed under UV irradiation to generate •OH and RCS (such as Cl•, Cl2 -• and ClO•), to rapidly and efficiently inactivate resistant bacteria and resistance genes in water.

Description

A method for removing ARB and ARGs from water by coupling UV irradiation with in-situ chlorination technology Technical Field

[0001] The invention belongs to the technical field of water treatment, and particularly relates to a method for removing resistant bacteria and resistance genes in water by using UV irradiation coupled with in-situ chlorine production technology. Background Art

[0002] With the widespread use of antibiotics, antibiotic resistance has emerged in microorganisms, posing a potential threat to environmental safety and human health and becoming a global concern. Antibiotic-resistant bacteria (ARBs) and resistance genes (ARGs) have been detected in various environmental media, particularly in wastewater treatment plants. ARBs and ARGs in wastewater can be transmitted to drinking water sources, including groundwater and surface water systems, through discharge and runoff.

[0003] In actual water treatment, UV irradiation and hypochlorous acid disinfection are two commonly used disinfection technologies. Under UV irradiation, nucleic acids in microbial cells can form pyrimidine dimers, leading to gene mutations and structural damage, thereby inactivating bacteria. However, under visible light, pyrimidine dimers can be repaired by photolyases produced in the cells, causing the genes to return to normal, thereby reviving the bacteria from a sublethal state. During chlorine disinfection, ARGs with different base sequences have different sensitivities to chlorine. In order to effectively remove all ARGs, a high dose of chlorine (>80 mg Cl2 min L –1 High doses of chlorine react with natural organic matter in water, easily producing high concentrations of disinfection byproducts, causing secondary pollution. Therefore, to protect human health and environmental safety, it is necessary to develop a technical method to effectively remove ARBs and ARGs from water bodies.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a method for removing ARB and ARGs in water by UV irradiation coupled with in-situ chlorination technology (UV / E-Cl2). By applying current to electrodes in the water, chloride ions lose electrons on the electrode surface to produce Cl2, which then reacts with water and / or ammonia to produce HClO, ClO – or / and chloramine, and further photolyzed under UV irradiation to produce ·OH and RCS (such as Cl·, Cl2 - · and ClO·), thereby efficiently removing ARBs and ARGs from water bodies.

[0006] The present invention is achieved through the following technical solutions:

[0007] The method of removing ARB and ARGs from water by UV irradiation coupled with in-situ chlorine generation technology (UV / E-Cl2) is as follows:

[0008] Placing an electrode group comprising at least one pair of anode electrodes and cathode electrodes in a body of water to be treated, and connecting the anode electrodes and the cathode electrodes to a power source respectively;

[0009] Place the water to be treated within the irradiation range of the UV lamp;

[0010] Connect the power supply so that an electric field is formed between the anode electrode and the cathode electrode, causing the chloride ions in the water to be treated to lose electrons on the surface of the anode electrode to generate Cl2, which then reacts with water and / or ammonia to generate HClO and ClO. – Or / and chloramine; under the irradiation of the UV lamp, HClO, ClO – or / and chloramine photolysis to generate active species including ·OH and RCS, which inactivate ARB and ARGs in the water to be treated;

[0011] The water to be treated contains chloride ions, ARBs and / or ARGs.

[0012] Furthermore, the anode electrode is a titanium-plated ruthenium-iridium electrode, a titanium dioxide electrode, a titanium dioxide nanotube electrode or a boron-doped diamond electrode.

[0013] Furthermore, the cathode electrode is a platinum electrode, a stainless steel electrode or a titanium electrode.

[0014] Furthermore, the current I of the anode electrode and the cathode electrode is selected to be 10≤I≤1000mA.

[0015] Furthermore, the UV lamp is a mercury lamp or a UV-LED lamp.

[0016] Furthermore, the ARGs include intracellular ARGs (i-ARGs) and extracellular ARGs (e-ARGs).

[0017] Furthermore, the ARB is a bacterium containing ARGs on a plasmid.

[0018] Furthermore, the water body to be treated is processed in batches or in a continuous flow manner.

[0019] Furthermore, the time used for each liter of water to be treated is 5 seconds to 10 minutes.

[0020] The method of the present invention synergizes the effects of electrochemical oxidation and UV to efficiently and quickly inactivate ARBs and ARGs; the treatment method is simple and easy to implement, and the effluent disinfection effect can be flexibly controlled by adjusting the current; there is no need to store and consume a large amount of oxidants, and it is green and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1a shows the removal effect of ARB by different technologies, and Figure 1b shows the photoreactivation of ARB after UV irradiation.

[0022] Figure 2 shows the removal effects of different technologies on i-ARGs (a) and e-ARGs (b).

[0023] Figure 3 shows the morphology of ARGs-containing plasmids in ARB after treatment with different techniques, as observed by atomic force microscopy. Figure 3a shows the morphology of the plasmid before treatment, Figure 3b shows the morphology of the plasmid after electrolysis, Figure 3c shows the morphology of the plasmid after chlorine oxidation, Figure 3d shows the morphology of the plasmid after UV irradiation, and Figure 3e shows the morphology of the plasmid after UV / E-Cl2 treatment.

[0024] Figure 4 shows the removal of i-ARGs by UV / E-Cl2 technology under different currents (a) and different chloride ion concentrations (b).

[0025] Implementation Method

[0026] The specific implementation and working process of the present invention will be further described below with reference to the accompanying drawings.

[0027] An electrode group including at least one pair of anode and cathode is fixed vertically and parallelly in a reaction device and immersed in the water to be treated. The anode and cathode are respectively connected to the positive electrode and negative electrode of the power supply.

[0028] The anode electrode can be a titanium-plated ruthenium-iridium electrode, a titanium dioxide electrode, a titanium dioxide nanotube electrode, a boron-doped diamond electrode, etc. The cathode electrode can be a platinum electrode, a stainless steel electrode or a titanium electrode, etc.

[0029] The UV lamp can be selected from various types of mercury lamps or UV-LED lamps. In one embodiment, the UV lamp is inserted into the water to be treated; in another embodiment, the UV lamp is placed above the water to be treated.

[0030] Wastewater containing chloride ions, ARBs and / or ARGs is injected into the reaction device.

[0031] Turn on the power supply so that the current I of the anode electrode and the cathode electrode is 10≤I≤1000mA. At this time, the chloride ions in the water lose electrons on the surface of the anode electrode to produce Cl2, which reacts with water and / or ammonia to produce HClO and ClO. – or / and chloramines, and further decomposed under UV irradiation to produce ·OH and RCS (such as Cl·, Cl2 - · and ClO·), thereby effectively inactivating ARBs and ARGs in water bodies.

[0032] The reaction device can be a batch device or a continuous flow device, and the residence time per liter of water to be treated is 5s to 10min.

[0033] The following examples further illustrate the effects of the method of the present invention.

[0034] The water samples to be treated in the embodiment are all the same groundwater with a pH value of 7.5. The initial ARB (E. coli TOP10) concentration of the water sample is ~10 7 CFU / mL, and the initial concentration of each i-ARG (tetA, sul1, sul2, ermB) was ∼10 8 copies / μL DNA, the chloride ion concentration was 55-300 mg / L, and the chloride ion concentration was adjusted by adding different amounts of sodium chloride, potassium chloride, etc.

[0035] In the following examples, the ARB concentration was determined by the dilution plate method, and the ARGs concentration was determined by the q-PCR method.

[0036] Example 1

[0037] The initial chloride ion concentration in the water sample to be treated was 150 mg / L. 0.7 L of the water sample was added to a batch reactor. A titanium-plated ruthenium-iridium anode and a stainless steel cathode were vertically and parallelly inserted into the reactor, submerged in the water. The electrodes were connected to a DC power supply and a UV lamp was inserted for irradiation. The distance between the two electrodes was 1 cm, and the distance between the UV lamp and the anode was 1 cm. The reactor was placed on a magnetic stirrer to ensure uniform mixing of the treated water sample.

[0038] In the UV / E-Cl2 treatment, the anode was a titanium-plated ruthenium-iridium electrode, measuring 4 cm x 12 cm; the cathode was a stainless steel electrode, measuring 4 cm x 12 cm. Under a DC power supply, the current across the anode and cathode was 200 mA. The UV lamp was a 10W low-pressure mercury lamp, emitting light at a wavelength of 254 nm.

[0039] In the single UV irradiation treatment, it is only necessary to turn on the above-mentioned UV lamp, without inserting the cathode and anode, and without turning on the DC power supply connecting the electrodes.

[0040] In the single electrolysis treatment, the anode and cathode settings and the current magnitude at both ends are the same as the above-mentioned UV / E-Cl2 treatment conditions, except that the UV lamp does not need to be inserted for irradiation.

[0041] In single-use chlorine oxidation, sodium hypochlorite solution is simply added to the water sample to be treated in the batch reactor to an initial chlorine concentration of 2.35 mg Cl2 / L. No cathode or UV lamp is required.

[0042] When UV irradiation alone and UV / E-Cl2 treatment were performed for approximately 5 seconds, ARB was inactivated by more than 5-log (Figure 1a). However, after 48 hours of exposure to visible light, the concentration of ARB in the effluent from UV irradiation alone increased significantly (Figure 1b), indicating that ARB was significantly photoreactivated after UV irradiation alone, but not after UV / E-Cl2 treatment.

[0043] After 5 min of UV / E-Cl2 treatment, the four i-ARGs were inactivated by more than ∼5-log ( Figure 2 a), and the concentration of e-ARGs did not increase but was almost completely removed ( Figure 2 b).

[0044] As shown in Figure 3, before treatment, the plasmid in ARB is a complete long chain or ring; after electrolysis, chlorine oxidation and UV irradiation treatment alone, the plasmid containing ARGs is interrupted, but some fragments are still long and may carry more resistance gene information; after UV / E-Cl2 treatment, the plasmid containing ARGs is almost completely broken into small fragments, which can effectively prevent the horizontal transfer of resistance genes.

[0045] Example 2

[0046] In this embodiment, the anode and cathode currents in embodiment 1 are replaced with 100 mA.

[0047] The treatment time was 5 min, and the removal effects of the four i-ARGs sul2, sul1, tetA and ermB were 4.8-log, 5.7-log, 5.4-log and 5.7-log, respectively.

[0048] Example 3

[0049] In this embodiment, the anode and cathode currents in Example 1 are replaced with 400 mA.

[0050] The treatment time was 5 min, and the removal effects of the four i-ARGs sul2, sul1, tetA and ermB were 5.3-log, 6.5-log, 6.3-log and 6.7-log, respectively.

[0051] Example 4

[0052] In this example, the chloride ion concentration in Example 2 is replaced with 55 mg / L.

[0053] The treatment time was 5 min, and the removal effects of the four i-ARGs sul2, sul1, tetA and ermB were 4.5-log, 5.1-log, 5.1-log and 5.3-log, respectively.

[0054] Example 5

[0055] In this example, the chloride ion concentration in Example 2 is replaced with 300 mg / L.

[0056] The treatment time was 5 min, and the removal effects of the four i-ARGs sul2, sul1, tetA and ermB were 4.9-log, 5.9-log, 6.5-log and 6.5-log, respectively.

[0057] As demonstrated in the examples above, the UV / E-Cl2 method coupled with in-situ chlorine generation (UV / E-Cl2) has a significant effect on the removal of ARBs and ARGs. Figures 1 to 3 compare the treatment effects of several methods, demonstrating that the UV / E-Cl2 method is significantly superior to electrolysis, chlorine oxidation, or UV irradiation alone.

[0058] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for removing ARB and ARGs from water by UV irradiation coupled with in-situ chlorination technology, characterized in that: Placing an electrode group including at least one pair of anode electrodes and cathode electrodes in a water body to be treated, wherein the anode electrodes and the cathode electrodes are respectively connected to a power source, and the water body to be treated contains chloride ions, ARBs and / or ARGs; Place the water to be treated within the irradiation range of the UV lamp; The power source is connected to form an electric field between the anode electrode and the cathode electrode, so that the chloride ions in the water to be treated lose electrons on the surface of the anode electrode to generate Cl2, and Cl2 continues to react with water and / or ammonia to generate HClO, ClO – Or / and chloramine; Under the irradiation of the UV lamp, HClO, ClO – Or / and chloramine photolysis to generate active species including OH and RCS, which inactivate ARB and ARGs in the water to be treated.

2. The method according to claim 1, characterized in that: The anode electrode is a titanium-plated ruthenium-iridium electrode, a titanium dioxide electrode, a titanium dioxide nanotube electrode or a boron-doped diamond electrode.

3. The method according to claim 1, characterized in that: The cathode electrode is a platinum electrode, a stainless steel electrode or a titanium electrode.

4. The method according to claim 1, characterized in that The current I of the anode electrode and the cathode electrode is selected to be 10≤I≤1000mA.

5. The method according to claim 1, characterized in that The UV lamp is a mercury lamp or a UV-LED lamp.

6. The method according to claim 1, characterized in that The ARGs include intracellular ARGs and extracellular ARGs.

7. The method according to claim 1, characterized in that The ARB is a bacterium containing ARGs on a plasmid.

8. The method according to claim 1, characterized in that The water body to be treated is treated in batches or in a continuous flow.

9. The method according to claim 8, characterized in that The time used for each liter of water to be treated is 5s to 10min.

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