A method for removing antibiotic resistance genes from wastewater based on a ferrate and sodium sulfite coupling system

Abstract

The present invention relates to a method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, and belongs to the technical field of sewage purification. The method of the present invention comprises adding ferrate and sodium sulfite to wastewater containing antibiotic resistance genes, immediately stirring rapidly, then stirring slowly, and separating the purified water body after static sedimentation. The Fe(VI), SO 4 ·‑ and HO · The combination of the oxidation of ferrate and the coagulation of iron oxides and hydroxides produced in situ by ferrate can effectively remove antibiotic resistance genes in wastewater, with a removal rate of 85.12%-95.04%. The method is simple to operate, requires a single type of reagent and a small amount, is easy to operate and manage, and can effectively remove antibiotic resistance genes in wastewater, providing a new and feasible technical method for solving the spread of resistance genes.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage purification and treatment, and in particular relates to a method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system. Background Art

[0002] Antibiotic resistance genes (ARGs) have been defined as a new environmental pollutant in recent years. Due to the widespread use of antibiotics in medicine, animal husbandry and agriculture, bacterial resistance to antibiotics has become an increasingly serious global health challenge. Once ARGs are transferred to human pathogens, the diseases caused by human pathogens that possess ARGs will become more difficult to cure. Antibiotic resistance in pathogens is associated with high morbidity and mortality and is considered a global public health issue, so the removal and reduction of antibiotic resistance genes is urgent.

[0003] Due to the high residual load of antibiotics in the influent of sewage treatment plants and the high bacterial density in activated sludge, sewage treatment plants have become an ideal environment for the production and proliferation of ARGs and are considered to be hotspots for the spread of ARGs. The results of a study on the pollution level of resistance genes in a sewage treatment plant showed that the high ARGs level (3.6×10 1 ~5.4×10 6 copies / mL) were found in wastewater treatment plant effluent samples (Chem, 2017, 172: 392-398). Moreover, ARGs entering the environment can be transferred horizontally and vertically, leading to their spread within and between species. Therefore, controlling the ARGs content in wastewater treatment plant effluent is of great significance to reducing the ecological risk of ARGs.

[0004] Research on ARGs removal technology is still in its infancy. The ARGs removal technologies reported so far mainly include biological, physical, and chemical treatment technologies, and have great limitations. Among them, ARGs are not destroyed after biological treatment, but still exist in large quantities in sludge, causing potential harm. Traditional disinfection methods (active chlorine disinfection, ozone disinfection, and ultraviolet disinfection) mainly inactivate pathogenic microorganisms by destroying cell structures through oxidation, and then the oxidants further penetrate into the bacteria to achieve the reduction of intracellular ARGs. However, the high energy and reagent costs involved are important limiting factors for their use. Therefore, conventional water treatment processes cannot guarantee safety in terms of antibiotic resistance, so it is very important to seek an efficient method to thoroughly control the safety risks of ARGs in the effluent of sewage treatment plants. Summary of the invention

[0005] In order to overcome the defects of the prior art, the present invention provides a method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system.

[0006] The technical solution adopted by the present invention is:

[0007] A method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system comprises the following steps: adding ferrate and sodium sulfite to wastewater containing antibiotic resistance genes, immediately stirring rapidly, then stirring slowly, and separating the supernatant after static sedimentation as the purified water.

[0008] Furthermore, in the above-mentioned method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, the ferrate is any one of potassium ferrate and sodium ferrate or a combination of both.

[0009] Furthermore, in the above-mentioned method for removing antibiotic resistance genes in wastewater based on a coupling system of ferrate and sodium sulfite, the dosage of ferrate in the wastewater is calculated as Fe, the dosage of sodium sulfite in the wastewater is calculated as S, and the molar ratio of Fe to S is 1:2 to 1:4.

[0010] Furthermore, in the above-mentioned method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, the rapid stirring speed is 600-800 rpm, and the rapid stirring time is 1-2 min.

[0011] Furthermore, in the above-mentioned method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, the slow stirring speed is 50-100 rpm, and the slow stirring time is 15-30 min.

[0012] Furthermore, in the above-mentioned method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, the static sedimentation time is 30 minutes.

[0013] Furthermore, in the above-mentioned method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, the antibiotic resistance genes include ciprofloxacin resistance genes and integron intI1.

[0014] The beneficial effects of the present invention are:

[0015] 1. Fe(VI) and SO4 in the coupling system of ferrate and sodium sulfite ·- and HO · It can damage DNA / RNA through its high oxidative property, thereby causing irreversible oxidative damage to the cell membrane, thereby destroying ARGs and reducing the pollution of resistance genes in the water environment.

[0016] 2. The iron-containing oxides and hydroxides produced in situ by ferrate can act as coagulants to further remove antibiotic resistance genes and integron intI1.

[0017] 3. The method of the present invention has the advantages of easy operation, simplicity and low economic cost. It does not produce any other polluting substances during the wastewater treatment process. It is healthier, more environmentally friendly and pollution-free. It is a green and environmentally friendly treatment method.

[0018] 4. The method for removing antibiotic resistance genes in wastewater based on the ferrate and sodium sulfite coupling system provided by the present invention has a removal rate of resistance genes as high as 85.12%-95.04%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a comparison chart of the removal of total genomic DNA content by K2FeO4 and K2FeO4 / Na2SO3 coupling systems in Example 1.

[0020] Figure 2 This is a comparison chart of the removal of target genes by K2FeO4 and K2FeO4 / Na2SO3 coupling systems in Example 1.

[0021] Figure 3 This is the free radical identification of the K2FeO4 / Na2SO3 coupling system in Example 1. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments.

[0023] Example 1

[0024] This embodiment 1 uses the effluent from a sequencing batch reactor (SBR) operated in a laboratory to simulate the wastewater in an actual sewage treatment plant, and specifically includes the following steps:

[0025] 1) Cultivation phase of antibiotic resistance genes in laboratory-run SBR:

[0026] Ciprofloxacin antibiotics were added to the SBR to cultivate ARGs in the SBR effluent. The SBR influent formula is shown in Table 1. The activated sludge was taken from the aeration tank of a sewage treatment plant in Shenyang.

[0027] Table 1 SBR influent formula

[0028]

[0029] 2) Start-up phase of antibiotic resistance genes in laboratory-run SBR:

[0030] 1.5L activated sludge and 2.5L prepared water were mixed and added to SBR. The SBR cycle was set to 6h, including 0.05h of water inlet, 3.6h of aerobic, 1.8h of anoxic, 0.5h of sedimentation, and 0.05h of drainage. Four cycles were run per day. The ARGs concentration in the mixed liquor was monitored regularly.

[0031] 3) Reaction stage:

[0032] The experimental device is a series of 1L beakers, each containing 100mL of supernatant taken from a sequencing batch activated sludge reactor after precipitation, and then K2FeO4 at 10mg Fe / L and Na2SO3 at 11.4mg S / L are added to the beakers, and then immediately stirred vigorously at 600rpm for 2 minutes, and then slowly stirred at 100rpm for 20 minutes, and the beakers were left stationary to settle for 30 minutes in a state of natural sedimentation. At the same time, no K2FeO4 and Na2SO3 were added, and only 10mg Fe / L of K2FeO4 was added as a comparison.

[0033] Take the water sample treated in the above steps, and use a 0.22μm water filter membrane to collect the supernatant after the drug treatment, in order to intercept bacteria and DNA in the supernatant; at the same time, use a 0.22μm water filter membrane to collect the precipitate after the drug treatment, in order to intercept bacteria and DNA in the precipitate. The filter membrane after filtration is used for DNA extraction, and the reaction samples are triplicate.

[0034] The extracted DNA was used to detect the abundance of target genes using quantitative PCR. The detected ARGs and primers used for quantitative PCR are shown in Table 2.

[0035] Table 2 ARGs classification and quantitative PCR primers

[0036]

[0037] The removal of total genomic DNA content under different treatment conditions (K2FeO4, K2FeO4 / Na2SO3 coupling system) is shown in Figure 2. Figure 1 Compared with the blank control, under the stress of 10 mg Fe / L, the removal rate of total genomic DNA content was 59.48%, and under the stress of the coupling system of 10 mg Fe / L and 11.4 mg S / L, the total genomic DNA content was 94.08%, indicating that both K2FeO4 alone and K2FeO4 / Na2SO3 coupling system can effectively remove intracellular and extracellular ARGs in wastewater, but the treatment effect of K2FeO4 / Na2SO3 coupling system is better.

[0038] The reaction equation of the coupling system of ferrate and sodium sulfite is as follows:

[0039] Fe(VI)+ SO32- →Fe(V)+SO3 ·- (1)

[0040] SO3 ·- +O2→SO5 ·- (2)

[0041] SO5 ·- + SO3 ·- →SO4 ·- +SO4 2- (3)

[0042] SO4 ·- +H2O→SO4 2- + HO · +H + (4)

[0043] Fe(VI)+H2O→Fe(OH)3 (5)

[0044] Generally speaking, the ferrate and sodium sulfite coupling system not only utilizes the oxidation of Fe(VI) to remove ARGs, but also generates sulfate (SO4 ·- ) and hydroxyl (HO · ) The active substances can penetrate deeply into bacterial cells, oxidatively destroy the DNA inside the cells, and achieve the purpose of removing ARGs.

[0045] The generation of active substances in the K2FeO4 / Na2SO3 coupling system requires the participation of Na2SO3, so the increase in the molar number of Na2SO3 is conducive to the generation of active substances, thereby promoting DNA damage. In order to obtain a better treatment effect, it is important to control the ratio of ferrate and sodium sulfite. In the present invention, the molar ratio of ferrate to sodium sulfite is Fe:S=1:2.

[0046] Figure 2 The removal of target genes in wastewater under the coupling system of ferrate and sodium sulfite. After the wastewater was treated with a mixture of ferrate and sodium sulfite, the abundance of ARGs was significantly reduced. In this embodiment, at the dosage of 10 mg Fe / L and 11.4 mg S / L, the removal rate of the resistance gene gyrA was the highest among the four target genes, at 95.04%, and the removal rate of the resistance gene qnrS was the lowest, at 88.87%. The abundance of the intI1 gene also decreased significantly, with a removal rate of 85.12%.

[0047] The reduction in the abundance of various target ARGs in the ferrate and sodium sulfite coupling system shows that the removal of ARGs in wastewater is not just physical removal. The ferrate and sodium sulfite coupling system can destroy the ARGs themselves, thereby reducing the risk of their treated by-products to the environment.

[0048] Figure 3 Identification of free radicals in the K2FeO4 / Na2SO3 coupled system.

[0049] The active free radicals in the ferrate and sodium sulfite coupling system mainly react with the target pollutants ARGs in the system, and the added EtOH and TBA mainly compete with the ARGs in the system to consume the active free radicals in the system. Figure 3 As shown in the figure, the addition of EtOH and TBA inhibited the removal of ARGs in the K2FeO4 / Na2SO3 coupling system to varying degrees. After adding 15mmol / L EtOH, the removal rate of ARGs in the system decreased from 85.91% to 16.45%. After adding the same concentration of TBA, the removal rate of ARGs in the system decreased to 60.97%. This result shows that in the K2FeO4 / Na2SO3 coupling system, SO4 plays a major role in the removal of target pollutants ARGs. ·- , after calculation, it was found that SO4 ·- The contribution of HO is about 51.99%. · The contribution of is about 28.95%. The rest of the contribution should be due to the intermediate valence iron [Fe(Ⅳ) / Fe(Ⅴ)] and the adsorption removal of iron hydroxide flocs, accounting for 19.06%.

[0050] The above phenomena all show that the ferrate and sodium sulfite coupling system can significantly remove ARGs in the secondary effluent of sewage treatment plants. When the ferrate and sodium sulfite dosage is Fe:S=1:2 in molar ratio, the removal rate of ciprofloxacin antibiotic-related resistance genes and intI1 can reach 85.12%-95.04%. In addition to generating multiple reactive free radicals (i.e., SO4 ·- and HO · In addition to the destruction of the ARGs structure by ferrous iron and / or high-valent iron and its intermediates (i.e., Fe(VI), Fe(IV) and Fe(V)), the flocculation effect caused by the Fe(VI) reduction product (Fe(OH)3) can jointly achieve the purpose of ARGs removal, effectively reducing the risk of horizontal gene transfer.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system, characterized in that: The method comprises the following steps: adding ferrate and sodium sulfite to wastewater containing antibiotic resistance genes, immediately stirring rapidly at a speed of 600-800 rpm for 1-2 minutes, then stirring slowly at a speed of 50-100 rpm for 15-30 minutes, and separating the supernatant after static sedimentation as the purified water; The dosage of ferrate in the wastewater is calculated as Fe, the dosage of sodium sulfite in the wastewater is calculated as S, and the molar ratio of Fe to S is 1:2-1:4; In the ferrate and sodium sulfite coupling system, SO4 plays a major role in the removal of target pollutants ARGs. •- and HO • .

2. A method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system according to claim 1, characterized in that: The ferrate is any one of potassium ferrate and sodium ferrate or a combination of both.

3. The method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system according to claim 1, characterized in that: The static sedimentation time is 30 min.

4. The method for removing antibiotic resistance genes in wastewater based on a ferrate and sodium sulfite coupling system according to claim 1, characterized in that: The antibiotic resistance genes include ciprofloxacin resistance genes and integron intI1.

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