Method for inactivating pathogenic microorganisms in sewage

Abstract

The application discloses a method for inactivating pathogenic microorganisms in sewage, which comprises the following steps: injecting sewage containing pathogenic microorganisms into a reaction chamber containing a negative / positive electrode system, adding an electrolyte into the reaction chamber to make the concentration of the electrolyte 0.02-0.1 mol / L, adjusting the pH to 5-7, adding peracetic acid and high ferric salt to make the concentration of the peracetic acid 10-50 μmol / L and the concentration of the high ferric salt 5-25 μmol / L, opening a direct current stabilized power supply to perform electric field treatment, and controlling the current density to be 10-50 mA / cm 2 , so as to complete the inactivation of the pathogenic microorganisms. The method adopts the coupling of electricity / peracetic acid / high ferric salt, improves the activation efficiency of the peracetic acid, and reasonably utilizes each component of the peracetic acid medicament, thereby generating various strong oxidizing species such as hydroxyl radicals and acetyl peroxide radicals. The method can realize the efficient inactivation of the pathogenic microorganisms under the conditions of low electric energy input and low peracetic acid and high ferric salt concentrations, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a method for inactivating pathogenic microorganisms in wastewater. Background Technology

[0002] Waterborne pathogens can endanger public health and ecosystems, making the disinfection of urban sewage crucial to minimize the release of pathogens into receiving water bodies. Currently used disinfection methods have various drawbacks: chlorine disinfection can lead to the generation of disinfection byproducts that pose safety risks to humans; ultraviolet disinfection is affected by water turbidity, resulting in unstable disinfection effects; and ozone has selective oxidation properties and requires additional generation equipment.

[0003] Peracetic acid (PAA), as a green and eco-friendly bactericide, has advantages such as strong bactericidal ability, no production of toxic disinfection byproducts, and low dependence on pH value, making it highly valuable for application. However, the O-O bond breaking efficiency of PAA is low, and using PAA alone cannot achieve optimal utilization. Therefore, activation is needed to accelerate bond breaking and improve the disinfection efficiency of PAA. However, current methods for activating PAA using ultraviolet (UV), metal ions, or carbon materials suffer from problems such as high energy consumption, easy secondary pollution, and cumbersome procedures.

[0004] CN111661911B discloses a method for removing organic pollutants from water, comprising the following steps: first, adding peracetic acid to water containing organic pollutants, then adding ferrate, and stirring the reaction to remove organic matter from the wastewater. The main mechanism of this method is that ferrate reacts with ionic peracetic acid to produce reactive species such as Fe(V), Fe(IV), and acetylperoxy radicals (CH3COOO·).

[0005] Fe VI O4 2- +CH3C(O)OO - →Fe V O4 3- +CH3C(O)OO·

[0006] Fe VI O4 2- +CH3C(O)OO - →Fe IV O3 2- +CH3COO - +O2

[0007] Under these conditions, the oxidizing capacity mainly comes from the direct electron transfer between Fe(V), Fe(IV) and pollutants, forming the final product mainly composed of Fe(OH)3. The utilization rate of peracetic acid is low, and the ability to remove pollutants is limited. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for inactivating pathogenic microorganisms in sewage, and to solve the problem that the existing sewage treatment technology has low utilization rate of peracetic acid and insufficient oxidation capacity, resulting in low disinfection efficiency.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A method for inactivating pathogenic microorganisms in wastewater involves injecting wastewater containing pathogenic microorganisms into a reaction chamber containing a cathode / anode system, adding electrolytes to the reaction chamber, adjusting the pH to 5-7, adding peracetic acid and ferrate, and then turning on a DC regulated power supply for electric field treatment, thereby completing the inactivation of pathogenic microorganisms. Preferably, peracetic acid is added in the form of an aqueous peracetic acid solution.

[0011] Furthermore, in the electrode system, the electrolyte concentration is 0.02–0.1 mol / L, the peracetic acid concentration is 10–50 μmol / L, and the ferrate concentration is 5–25 μmol / L.

[0012] Furthermore, the current density of the electric field treatment is 10–50 mA / cm². 2 .

[0013] Furthermore, the electric field treatment time is 1 to 5 minutes.

[0014] Furthermore, the ferrate is one or more of potassium ferrate or sodium ferrate.

[0015] Furthermore, the electrolyte is one or more of hydrochloride or sulfate.

[0016] Furthermore, the sulfate is at least one of sodium sulfate or potassium sulfate; the hydrochloride is at least one of sodium chloride and potassium chloride.

[0017] Furthermore, the anode and cathode of the electrode system are respectively a graphite electrode, a metal electrode, or a metal composite electrode. Specifically, the graphite electrode is a graphite rod electrode, graphite filament electrode, graphite felt electrode, graphite plate electrode, graphite sponge electrode, graphite granule electrode, or porous graphite electrode; the metal composite electrode is a composite electrode modified with one or more of the following: metal, metal oxide, or metal hydroxide, and the metal is a metal element from periods 4 to 6 of the periodic table, such as a titanium-plated platinum electrode or a nickel-plated platinum electrode.

[0018] Working principle: First, under the action of an electric field, peracetic acid gains electrons at the cathode, thereby generating active species such as hydroxyl radicals (·OH), acetoxy radicals (CH3COO·), and acetylperoxy radicals (CH3COOO·);

[0019] CH3C(O)OOH + e- → CH3COO· + OH-

[0020] CH3C(O)OOH + e- → CH3COO- + OH-

[0021] CH3C(O)OOH+CH3C(O)O·→CH3C(O)OO·+CH3C(O)OH

[0022] Meanwhile, peracetic acid, as an organic acid, ionizes to release a hydrogen ion, forming ionic peracetic acid. Ionic peracetic acid reacts with ferrates to produce acetylperoxy radicals (CH3COOO·) and highly oxidizing high-valent iron (Fe(V)) and Fe(IV). A portion of the high-valent iron is reduced to produce Fe... 3+ It can activate peracetic acid to produce hydroxyl radicals (·OH), acetoxy radicals (CH3COO·), and acetylperoxy radicals (CH3COOO·), among which:

[0023] CH3C(O)OOH+Fe 3+ +H₂O→CH₃C(O)OO·+Fe 2+ +H3O +

[0024] Furthermore, under the influence of an electric field, iron ions undergo a cycle between high and low valence states, maintaining the high activation efficiency of peracetic acid and maximizing the oxidation capacity of the reaction system to efficiently inactivate pathogenic microorganisms in wastewater. The formation of Fe(OH)3, another high-valence iron reduction product, gives the system a certain coagulation capacity. This process is conducive to the aggregation of pathogenic microorganisms, making the inactivation process even more efficient.

[0025] In addition, Fe 3+ Fe 2+ It can undergo a Fenton reaction with hydrogen peroxide present in peracetic acid solution, further increasing the content of active oxide species in the system and improving the inactivation efficiency of pathogenic microorganisms in sewage.

[0026] In summary, the electro / peracetic acid / ferrate coupling system of this invention combines the advantages of electrolysis, peracetic acid, and ferrate, increasing the types and quantities of active oxides in four ways: First, it increases the activation channels for peracetic acid through the electrode system, thereby increasing the types and quantities of active oxides; second, it enhances the oxidation capacity of the reaction system by generating active free radicals and high-valent iron through the reaction of ferrate and ionic peracetic acid; third, it reduces Fe by a portion of the high-valent iron. 3+It can react with peracetic acid, further increasing the number of active oxides, while the electrode system can promote the cycling of high and low valence species of iron ions, keeping the activation efficiency of peracetic acid consistently high; fourthly, through Fe... 3+ Fe 2+ The peracetic acid reacts with hydrogen peroxide in the peracetic acid solution via a Fenton reaction, further increasing the content of active oxides in the system. The combined effect of these four aspects increases the variety and quantity of active oxides, maximizing the activation efficiency of peracetic acid and its utilization. This also gives the reaction system strong oxidizing power. Furthermore, the formation of Fe(OH)3 imparts a certain coagulation capacity to the system. The combined effect of oxidation and coagulation allows the reaction system to remove both resistant genes and recalcitrant organic matter. Therefore, the electrode system of this invention exhibits a synergistic effect with peracetic acid and ferrate. The inactivation efficiency of this coupled oxidation system against pathogenic microorganisms is far higher than that of the electroactivated peracetic acid oxidation method and the ferrate (VI)-peracetic acid oxidation system; it is not a simple superposition of several oxidation methods.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The method for inactivating pathogenic microorganisms in wastewater according to the present invention employs electro- / peracetic acid / ferrate coupled oxidation, wherein the electrode system and the Fe produced by ferrate reduction... 3+ It can react with peracetic acid to produce reactive oxide species such as hydroxyl radicals (·OH), acetoxy radicals (CH3COO·), and acetylperoxy radicals (CH3COOO·). Furthermore, the reaction between ferrate and peracetic acid also generates additional high-valence iron species (Fe(V) and Fe(IV)), enabling the coupling and combined use of multiple processes. This increases the variety and quantity of reactive oxide species, thus making the inactivation of pathogenic microorganisms more efficient. In addition, the electrode system can promote the cycling of high and low valence iron ions, maintaining the high activation efficiency of peracetic acid and maximizing its utilization, further promoting the inactivation of pathogenic microorganisms.

[0029] 2. Fe present in the reaction system of this invention 3+ Fe 2+ It can undergo a Fenton reaction with hydrogen peroxide coexisting in peracetic acid, further increasing the content of active oxide species in the system and improving the inactivation efficiency of pathogenic microorganisms in wastewater.

[0030] 3. The method for inactivating pathogenic microorganisms in wastewater according to the present invention is simple in process, uses green and economical agents, and will not cause secondary pollution to the environment. It can inactivate pathogenic microorganisms with only a small energy input, reducing the amount of electrical energy input and consumption of peracetic acid and ferrate. It is suitable for large-scale engineering projects and has good application prospects. Attached Figure Description

[0031] Figure 1 This is a logarithmic time-bacterial removal rate curve of bacteria in wastewater in Example 1.

[0032] Figure 2 This is a logarithmic curve of time versus bacterial removal rate in wastewater from Example 2.

[0033] Figure 3 This is the time-bacterial removal rate logarithmic curve of bacteria in wastewater in Example 3.

[0034] Figure 4 This is the time-bacterial removal rate logarithmic curve of bacteria in wastewater in Example 4.

[0035] Figure 5 This is a logarithmic time-bacterial removal rate curve of bacteria in wastewater in Example 5.

[0036] Figure 6 This is the time-bacterial removal rate logarithmic curve of bacteria in wastewater in Example 6.

[0037] Figure 7 This is a logarithmic curve of time versus bacterial removal rate in wastewater for Comparative Example 1.

[0038] Figure 8 This is a logarithmic curve of time versus bacterial removal rate in wastewater compared to Example 2.

[0039] Figure 9 This is a logarithmic curve of time versus bacterial removal rate in wastewater for Comparative Example 3.

[0040] In the figure, N represents the bacterial content in the wastewater at a certain moment after wastewater treatment, and N0 represents the bacterial content in the initial state of the wastewater. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the embodiments.

[0042] Escherichia coli is widely found in the intestines of humans and animals, and is therefore commonly used as an indicator bacterium for fecal contamination of water sources. In the embodiments and comparative examples of this invention, Escherichia coli was selected as the target bacterium.

[0043] Example 1

[0044] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0045] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode: titanium-plated platinum electrode; cathode: titanium-plated platinum electrode). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, peracetic acid aqueous solution was added to a peracetic acid concentration of 20 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 10 μmol / L. The DC power supply was then started, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0046] Record the changes in the number of bacteria in the wastewater to be treated in this embodiment, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 1 As shown. By Figure 1 It can be seen that in this embodiment, the bacterial removal rate was 4.9 log after 5 minutes.

[0047] Example 2

[0048] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0049] The wastewater to be treated (bacterial concentration of 10) 6 ~10 7 A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode: titanium-plated platinum electrode; cathode: titanium-plated platinum electrode). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, peracetic acid aqueous solution was added to a peracetic acid concentration of 20 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 10 μmol / L. The DC power supply was then started, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0050] Record the changes in the number of bacteria in the wastewater to be treated in this embodiment, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 2 As shown. By Figure 2 As can be seen, in this embodiment, bacteria were completely removed within 3 minutes, with a removal rate of 6.9 log.

[0051] Example 3

[0052] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0053] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode: titanium-plated platinum electrode; cathode: titanium-plated platinum electrode). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, peracetic acid aqueous solution was added to a peracetic acid concentration of 20 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 10 μmol / L. The DC power supply was then started, maintaining a current intensity of 20 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0054] Record the changes in the number of bacteria in the wastewater to be treated in this embodiment, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 3 As shown. By Figure 3 It can be seen that in this embodiment, the bacterial removal rate was 5.4 log after 5 minutes.

[0055] Example 4

[0056] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0057] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8 A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode: titanium-plated platinum electrode; cathode: titanium-plated platinum electrode). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 7, peracetic acid aqueous solution was added to a peracetic acid concentration of 20 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 10 μmol / L. The DC power supply was then started, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0058] Record the changes in the number of bacteria in the wastewater to be treated in this embodiment, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 4 As shown. By Figure 4 It can be seen that in this embodiment, the bacterial removal rate is 4.4 log after 5 minutes.

[0059] Example 5

[0060] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0061] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode and cathode were both titanium-plated platinum electrodes). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, peracetic acid aqueous solution was added to a peracetic acid concentration of 20 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 15 μmol / L. The DC power supply was then started, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0062] Record the changes in the number of bacteria in the wastewater to be treated in this embodiment, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 5 As shown. By Figure 5 It can be seen that in this embodiment, the bacterial removal rate is 5.5 log after 5 minutes.

[0063] Example 6

[0064] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0065] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8 A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode and cathode were both titanium-plated platinum electrodes). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, peracetic acid aqueous solution was added to a peracetic acid concentration of 30 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 10 μmol / L. The DC power supply was then started, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0066] Record the changes in the number of bacteria in the wastewater to be treated in this embodiment, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 6 As shown. By Figure 6 It can be seen that in this embodiment, the bacterial removal rate was 5.8 log after 5 minutes.

[0067] Comparative Example 1

[0068] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0069] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode and cathode were both titanium-plated platinum electrodes). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, and potassium ferrate was added to a concentration of 10 μmol / L. The DC power supply was then turned on, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0070] Record the changes in the number of bacteria in the wastewater to be treated in this comparative example, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 7 As shown. By Figure 7 It can be seen that in this embodiment, the bacterial removal rate is 1.3 log after 5 minutes.

[0071] Comparative Example 2

[0072] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0073] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8 A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (anode and cathode were both titanium-plated platinum electrodes). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, and an aqueous solution of peracetic acid was added to a peracetic acid concentration of 20 μmol / L. The DC power supply was then started, maintaining a current intensity of 10 mA / cm². 2 After 5 minutes of treatment, the treated wastewater is discharged from the outlet.

[0074] Record the changes in the number of bacteria in the wastewater to be treated in this comparative example, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 8 As shown. By Figure 8 It can be seen that in this embodiment, the bacterial removal rate is 2.6 log after 5 minutes.

[0075] Comparative Example 3

[0076] A method for inactivating pathogenic microorganisms in wastewater, specifically including the following steps:

[0077] The wastewater to be treated (bacterial concentration of 10) 7 ~10 8A CFU / mL solution was injected into the reaction chamber of the cathode / cathode electrode system (the anode was a titanium-plated platinum electrode, and the cathode was a titanium-plated platinum electrode). Sodium sulfate was then added to the reaction chamber to a concentration of 0.05 mol / L, the pH was adjusted to 5, peracetic acid aqueous solution was added to a peracetic acid concentration of 20 μmol / L, and potassium ferrate was added to a potassium ferrate concentration of 10 μmol / L. After treatment for 5 minutes, the treated wastewater was discharged from the outlet.

[0078] Record the changes in the number of bacteria in the wastewater to be treated in this comparative example, calculate the bacterial removal rate, and plot a logarithmic time-bacterial removal rate curve, as shown below. Figure 9 As shown. By Figure 9 It can be seen that in this embodiment, the bacterial removal rate is 3.2 log after 5 minutes.

[0079] Table 1 shows a comparison of the reaction conditions of Examples 1-6 and Comparative Examples 1-3.

[0080] Table 1

[0081]

[0082] As can be seen from Examples 1-6, the present invention can treat bacterial concentrations as high as 10 7 ~10 8 When treating wastewater with CFU / mL, the bacterial removal rate reached 5.8 log after 5 minutes, while when treating bacterial concentrations of 10... 6 ~10 7 When treating wastewater with a concentration of CFU / mL, bacteria can be rapidly and almost completely removed within 3 minutes. Therefore, the inactivation method for pathogenic microorganisms in wastewater of this invention has the advantages of excellent inactivation efficiency and applicability to wastewater treatment with different bacterial concentrations, and has broad application prospects.

[0083] Comparing Example 1 and Comparative Examples 1-3, it can be seen that, under the same conditions, compared with the electrochemical-ferrate system for inactivating pathogenic microorganisms, the removal rate of *E. coli* by this invention is 3.6 log; compared with the electrochemically activated peracetic acid system for inactivating pathogenic microorganisms, the removal rate of *E. coli* by this invention is 2.3 log; and compared with the ferrate-peracetic acid system for inactivating pathogenic microorganisms, the removal rate of *E. coli* by this invention is 1.7 log. It is evident that the effect of this invention in inactivating pathogenic microorganisms in wastewater is significantly superior to other treatment methods. This is because this invention fully utilizes the coupling effect between electrochemical, peracetic acid, and ferrate, greatly enhancing the interaction and utilization rate of each agent, increasing the generation efficiency of active oxide species, and thus enhancing the efficiency of inactivating pathogenic microorganisms in wastewater.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for inactivating pathogenic microorganisms in wastewater, characterized in that, Wastewater containing pathogenic microorganisms is injected into a reaction chamber containing an electrode system with a cathode and an anode. Electrolytes are then added to the reaction chamber, the pH is adjusted to 5-7, peracetic acid and ferrate are added, and a DC regulated power supply is turned on to perform electric field treatment, thus completing the inactivation of pathogenic microorganisms.

2. The method for inactivating pathogenic microorganisms in wastewater according to claim 1, characterized in that, In the electrode system, the electrolyte concentration is 0.02~0.1 mol / L, the peracetic acid concentration is 10~50 μmol / L, and the ferrate concentration is 5~25 μmol / L.

3. The method for inactivating pathogenic microorganisms in wastewater according to claim 2, characterized in that, The current density of the electric field treatment is 10~50 mA / cm². 2 .

4. The method for inactivating pathogenic microorganisms in wastewater according to claim 3, characterized in that, The electric field treatment time is 1 to 5 minutes.

5. The method for inactivating pathogenic microorganisms in wastewater according to claim 1, characterized in that, The ferrate is one or more of potassium ferrate or sodium ferrate.

6. The method for inactivating pathogenic microorganisms in wastewater according to claim 1, characterized in that, The electrolyte is one or more of hydrochloride or sulfate.

7. The method for inactivating pathogenic microorganisms in wastewater according to claim 6, characterized in that, The sulfate is at least one of sodium sulfate or potassium sulfate; the hydrochloride is at least one of sodium chloride and potassium chloride.

8. The method for inactivating pathogenic microorganisms in wastewater according to claim 1, characterized in that, The anode of the electrode system is a graphite electrode, a metal electrode, or a metal composite electrode; the cathode is a graphite electrode, a metal electrode, or a metal composite electrode.

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