A wastewater treatment process using ultraviolet light and sodium hypochlorite

Abstract

The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment process using ultraviolet light and sodium hypochlorite, which comprises the following steps: S1. treating the sewage with ultraviolet light, controlling the ultraviolet dose to be 15-25 mJ / cm 2 , the wavelength of the ultraviolet lamp is 254nm, and the irradiation time is 1-5min; S2. under the condition of not stopping the ultraviolet light illumination, modified sodium hypochlorite is added to the sewage after step S1 treatment to obtain the treated water body; S3. sodium thiosulfate is added to the water body obtained in step S2, excess chlorine element in the water body is removed, and the water sample after final treatment is obtained. The synergistic effect of ultraviolet light of the present invention and modified sodium hypochlorite reduces the dosage of sodium hypochlorite (only 1mg / L is required to meet the standard), while shortening the contact reaction time to 1min, and comprehensive energy consumption is reduced by 30%-40%. In addition, sodium thiosulfate accurately controls the amount and neutralizes residual chlorine to avoid excessive reagent residues, which meets the requirements of green chemical process.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment process using ultraviolet light and sodium hypochlorite in collaboration. Background Art

[0002] If the various pathogenic microorganisms surviving in sewage are not adequately removed through disinfection, these pathogens may enter receiving water bodies and cause a variety of waterborne diseases, posing risks to the ecology and human health. Currently, commonly used sewage disinfection technologies mainly include chemical disinfection methods (such as sodium hypochlorite, chlorine dioxide, and ozone) and physical disinfection methods (such as ultraviolet light). Sodium hypochlorite is the most commonly used disinfectant in sewage treatment plants, but it reacts with natural organic matter (NOM) present in sewage to produce large amounts of toxic halogenated disinfection byproducts (DBPs), which have potential adverse effects on the aquatic environment and human health. Compared with traditional chemical disinfection, ultraviolet disinfection produces almost no "carcinogenic, teratogenic, and mutagenic" disinfection byproducts, but its disinfection effect is unstable in actual application, and inactivated microorganisms may be photoreactivated. The existence of these problems has limited the application and development of these single disinfection methods in sewage disinfection, thus giving rise to combined disinfection processes.

[0003] At present, the disinfection processes commonly used in sewage treatment plants are chlorine disinfection and ultraviolet disinfection. However, the problems brought about by the accumulation of disinfection by-products, microbial photoreactivation and low disinfection efficiency during the disinfection process have limited the further application and development of disinfection processes. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a sewage treatment process that combines ultraviolet light with sodium hypochlorite.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A wastewater treatment process using ultraviolet light and sodium hypochlorite, comprising the following steps:

[0007] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 15-25mJ / cm 2 , the wavelength of the ultraviolet lamp is 254nm, and the irradiation time is 1-5min;

[0008] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite to obtain treated water;

[0009] S3. Sodium thiosulfate is added to the water obtained in step S2 to remove excess chlorine in the water to obtain the final treated water sample;

[0010] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0011] S21. Dissolve chitosan in a dilute acetic acid solution and stir until completely dissolved to form a chitosan solution;

[0012] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution, stirring while adding the solution to mix uniformly to form a chitosan-EDTA complex solution;

[0013] S23. 3-5 parts of chitosan-EDTA complex solution and 5-8 parts of modified light co-solvent were added to 20-30 parts of sodium hypochlorite solution to obtain a mixed solution;

[0014] S24. Sodium bicarbonate is added to the mixed solution to control the pH of the mixed solution to be 6.8-7.5. The addition process is carried out under stirring conditions at 25-30° C. to finally obtain modified sodium hypochlorite.

[0015] The preparation of the modified photo-assisted solvent comprises the following steps:

[0016] S231. 3-5 parts of nano-zinc oxide were added to 20-25 parts of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 20-30 min to obtain a nano-zinc oxide solution;

[0017] S232. 1-2 parts of cetyltrimethylammonium bromide were added to the nano-zinc oxide solution and stirred in a water bath at 60 ° C for 1-2 h to obtain a CTAB-nano-zinc oxide solution;

[0018] S233. Add 4-6 parts of potassium persulfate to the CTAB-nano zinc oxide solution and stir for 2-3 hours to finally obtain a modified photo-assisted solvent.

[0019] Preferably, the mass ratio of chitosan to EDTA in steps S21 and S22 is 3:1.

[0020] Preferably, the stirring speed during the preparation of the modified photo-assisted solvent is 300-350 r / min.

[0021] Preferably, the added amount of modified sodium hypochlorite is 1-3 mg / L.

[0022] Preferably, the amount of sodium thiosulfate added is 0.1-0.2 mg / L.

[0023] Preferably, in step S1, the ultraviolet lamp is a low-pressure mercury lamp with a power of 30W and a lamp tube spacing of 5 cm.

[0024] Preferably, the stirring speed during the preparation of the modified sodium hypochlorite is 250-300 r / min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention utilizes modified sodium hypochlorite, which can generate active oxygen and sulfate radicals under the action of ultraviolet light, and synergistically attack the microbial membrane structure with hypochlorous acid, oxidatively degrade complex organic matter, reduce the ineffective consumption of sodium hypochlorite and stabilize the effective chlorine concentration, further improving the degradation efficiency.

[0027] 2. The present invention adopts a treatment process of first ultraviolet and then ultraviolet with modified sodium hypochlorite to inactivate fecal coliform bacteria. The inactivation effect can be stably maintained at 1.8-lg, 1.4-lg and 2.0-lg or above, which is more stable than the simultaneous disinfection of ultraviolet and modified sodium hypochlorite.

[0028] 3. The synergistic effect of ultraviolet light and modified sodium hypochlorite in this invention reduces the dosage of sodium hypochlorite (only 1 mg / L is needed to meet the standard), shortens the contact reaction time to 1 minute, and reduces overall energy consumption by 30%-40%. In addition, the precise control of sodium thiosulfate neutralizes residual chlorine, avoiding excessive residual reagents, meeting the requirements of green chemical processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a process flow chart of the sewage treatment process using ultraviolet light and sodium hypochlorite in combination;

[0030] Figure 2 Schematic diagram of the sterilization effect of modified sodium hypochlorite added to water samples treated in Examples 1-6 of the present invention after reacting for 1 minute, wherein the abscissa represents the dosage of modified sodium hypochlorite (mg / L), corresponding to Examples 1-6 respectively;

[0031] Figure 3 Schematic diagram of the sterilization effect of modified sodium hypochlorite added to water samples treated in Examples 1-6 of the present invention after a 3-minute reaction, wherein the abscissa represents the dosage of modified sodium hypochlorite (mg / L), corresponding to Examples 1-6 respectively;

[0032] Figure 4 Schematic diagram of the sterilization effect of modified sodium hypochlorite added to water samples treated in Examples 1-6 of the present invention after reacting for 5 minutes, wherein the abscissa represents the dosage of modified sodium hypochlorite (mg / L), corresponding to Examples 1-6 respectively;

[0033] Figure 5 This is a comparison chart of the sterilization effects of modified sodium hypochlorite added to water samples treated in Examples 1-6 of the present invention after reacting for 1 minute, 3 minutes, and 5 minutes, wherein the abscissa represents the dosage of modified sodium hypochlorite (mg / L), corresponding to Examples 1-6 respectively;

[0034] Figure 6Schematic diagram of the sterilization effect of modified sodium hypochlorite after the water samples treated in Comparative Examples 1-6 of the present invention are added, wherein the abscissa is the dosage of modified sodium hypochlorite (mg / L), corresponding to Comparative Examples 1-6 respectively;

[0035] Figure 7 This is a three-dimensional fluorescence spectrum of raw water before treatment by the present invention;

[0036] Figure 8 This is a three-dimensional fluorescence spectrum of the water sample after treatment in Example 1 of the present invention;

[0037] Figure 9 This is a three-dimensional fluorescence spectrum of the water sample after being treated in Comparative Example 1 of the present invention;

[0038] Figure 10 This is a line graph showing the photoreactivation rate of fecal coliform bacteria in the water sample treated in Example 1 of the present invention;

[0039] Figure 11 This is a line graph of the photoreactivation rate of fecal coliform group in the water sample treated in Comparative Example 1 of the present invention;

[0040] Figure 12 NH4 in the water sample after treatment in Example 1 of the present invention + -N and TP removal effect line graph, where the horizontal axis is the dosage of modified sodium hypochlorite (mg / L);

[0041] Figure 13 NH4 in the water sample treated in Comparative Example 1 of the present invention + -N and TP removal effect line graph, where the horizontal axis is the dosage of modified sodium hypochlorite (mg / L);

[0042] Figure 14 This is a line graph showing the turbidity changes of the water sample after treatment in Example 1 of the present invention, wherein the abscissa represents the dosage of modified sodium hypochlorite (mg / L);

[0043] Figure 15 This is a line graph showing the turbidity changes of water samples after treatment in Comparative Example 1 of the present invention, wherein the abscissa represents the dosage of modified sodium hypochlorite (mg / L);

[0044] Figure 16 COD and UV in the water sample after treatment in Example 1 of the present invention 254 The horizontal axis is the dosage of modified sodium hypochlorite (mg / L);

[0045] Figure 17 COD and UV in the water sample after treatment in comparative example 1 of the present invention 254 The horizontal axis is the dosage of modified sodium hypochlorite (mg / L). DETAILED DESCRIPTION

[0046] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] See also Figure 1-17 , the present invention provides a technical solution:

[0048] The sewage in the following examples and comparative examples is all secondary effluent from a sewage treatment plant in Changchun City. A total of 28 L of water was randomly taken and divided into 14 portions for use in Examples 1-6 and Comparative Examples 1-8.

[0049] Example 1

[0050] A wastewater treatment process using ultraviolet light and sodium hypochlorite:

[0051] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 15mJ / cm 2 The wavelength of the UV lamp is 254nm, the irradiation time is 1min, the UV lamp used is a low-pressure mercury lamp, the power is 30W, and the distance between the lamp tubes is 5cm;

[0052] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite in an amount of 0.5 mg / L to obtain treated water;

[0053] S3. Sodium thiosulfate was added to the water obtained in step S2 in an amount of 0.1 mg / L to remove excess chlorine from the water to obtain the final treated water sample;

[0054] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0055] S21. Dissolve chitosan in a dilute acetic acid solution and stir at 250 r / min until completely dissolved to form a chitosan solution. The mass ratio of chitosan to ethylenediaminetetraacetic acid in step S22 is 3:1.

[0056] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution. The solution was stirred at 250 r / min to mix the solution uniformly to form a chitosan-EDTA complex solution.

[0057] S23. 30 g of chitosan-EDTA complex solution and 50 g of modified light cosolvent were added to 200 g of sodium hypochlorite solution to obtain a mixed solution;

[0058] S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 6.8. The addition process was carried out at 25°C and a stirring speed of 250 r / min to obtain modified sodium hypochlorite.

[0059] The preparation of the modified photo-assisted solvent comprises the following steps:

[0060] S231. 30 g of nano zinc oxide was added to 200 g of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 20 min to obtain a nano zinc oxide solution;

[0061] S232. 10 g of cetyltrimethylammonium bromide was added to the nano-zinc oxide solution and stirred at 300 r / min in a water bath at 60 ° C for 1 h to obtain a CTAB-nano-zinc oxide solution;

[0062] S233. Add 40 g of potassium persulfate to the CTAB-nano zinc oxide solution and stir at a speed of 300 r / min for 2 h to finally obtain a modified photo-assisted solvent.

[0063] Example 2

[0064] A wastewater treatment process using ultraviolet light and sodium hypochlorite:

[0065] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 25mJ / cm 2 The wavelength of the UV lamp is 254nm, the irradiation time is 5min, the UV lamp used is a low-pressure mercury lamp, the power is 30W, and the lamp spacing is 5cm;

[0066] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite in an amount of 1 mg / L to obtain treated water;

[0067] S3. Sodium thiosulfate was added to the water obtained in step S2 in an amount of 0.2 mg / L to remove excess chlorine from the water to obtain the final treated water sample;

[0068] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0069] S21. Dissolve chitosan in a dilute acetic acid solution and stir at 300 r / min until completely dissolved to form a chitosan solution. The mass ratio of chitosan to ethylenediaminetetraacetic acid in step S22 is 3:1.

[0070] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution. The solution was stirred at 300 r / min to mix the solution uniformly to form a chitosan-EDTA complex solution.

[0071] S23. 50 g of chitosan-EDTA complex solution and 80 g of modified light cosolvent were added to 300 g of sodium hypochlorite solution to obtain a mixed solution;

[0072] S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 7.5. The addition process was carried out at 30°C and a stirring speed of 300 r / min to obtain modified sodium hypochlorite.

[0073] The preparation of the modified photo-assisted solvent comprises the following steps:

[0074] S231. 50 g of nano zinc oxide was added to 250 g of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 30 min to obtain a nano zinc oxide solution;

[0075] S232. 20 g of cetyltrimethylammonium bromide was added to the nano-zinc oxide solution and stirred at 350 r / min in a water bath at 60 ° C for 2 h to obtain a CTAB-nano-zinc oxide solution;

[0076] S233. Add 60 g of potassium persulfate to the CTAB-nano zinc oxide solution and stir at a speed of 350 r / min for 3 h to finally obtain a modified photo-assisted solvent.

[0077] Example 3

[0078] A wastewater treatment process using ultraviolet light and sodium hypochlorite:

[0079] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 20mJ / cm 2 The wavelength of the UV lamp is 254nm, the irradiation time is 2min, the UV lamp used is a low-pressure mercury lamp, the power is 30W, and the lamp tube spacing is 5cm;

[0080] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite in an amount of 2 mg / L to obtain treated water;

[0081] S3. Sodium thiosulfate was added to the water obtained in step S2 in an amount of 0.12 mg / L to remove excess chlorine from the water to obtain the final treated water sample;

[0082] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0083] S21. Dissolve chitosan in a dilute acetic acid solution and stir at 260 r / min until completely dissolved to form a chitosan solution. The mass ratio of chitosan to ethylenediaminetetraacetic acid in step S22 is 3:1.

[0084] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution. The solution was stirred at 260 r / min to mix the solution uniformly to form a chitosan-EDTA complex solution.

[0085] S23. 40 g of chitosan-EDTA complex solution and 40 g of modified light co-solvent were added to 220 g of sodium hypochlorite solution to obtain a mixed solution;

[0086] S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 7. The addition process was carried out at 26°C and 260 r / min with stirring to obtain modified sodium hypochlorite.

[0087] The preparation of the modified photo-assisted solvent comprises the following steps:

[0088] S231. 40 g of nano zinc oxide was added to 210 g of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 22 min to obtain a nano zinc oxide solution;

[0089] S232. 15 g of cetyltrimethylammonium bromide was added to the nano-zinc oxide solution and stirred at 310 r / min in a water bath at 60 ° C for 1.5 h to obtain a CTAB-nano-zinc oxide solution;

[0090] S233. Add 50 g of potassium persulfate to the CTAB-nano zinc oxide solution and stir at a speed of 310 r / min for 2.5 h to finally obtain a modified photo-assisted solvent.

[0091] Example 4

[0092] A wastewater treatment process using ultraviolet light and sodium hypochlorite:

[0093] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 17mJ / cm 2 The wavelength of the UV lamp is 254nm, the irradiation time is 3min, the UV lamp used is a low-pressure mercury lamp, the power is 30W, and the lamp tube spacing is 5cm;

[0094] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite in an amount of 3mg / L to obtain treated water;

[0095] S3. Sodium thiosulfate was added to the water obtained in step S2 in an amount of 0.14 mg / L to remove excess chlorine from the water to obtain the final treated water sample;

[0096] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0097] S21. Dissolve chitosan in a dilute acetic acid solution and stir at 270 r / min until completely dissolved to form a chitosan solution. The mass ratio of chitosan to ethylenediaminetetraacetic acid in step S22 is 3:1.

[0098] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution. The solution was stirred at 270 r / min to mix the solution uniformly to form a chitosan-EDTA complex solution.

[0099] S23. 45 g of chitosan-EDTA complex solution and 60 g of modified light co-solvent were added to 240 g of sodium hypochlorite solution to obtain a mixed solution;

[0100] S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 7.1. The addition process was carried out at 27°C and 270 r / min with stirring to obtain modified sodium hypochlorite.

[0101] The preparation of the modified photo-assisted solvent comprises the following steps:

[0102] S231. 45 g of nano zinc oxide was added to 220 g of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 24 min to obtain a nano zinc oxide solution;

[0103] S232. 15 g of cetyltrimethylammonium bromide was added to the nano-zinc oxide solution and stirred at 320 r / min in a water bath at 60 ° C for 1.5 h to obtain a CTAB-nano-zinc oxide solution;

[0104] S233. Add 45 g of potassium persulfate to the CTAB-nano zinc oxide solution and stir at a speed of 320 r / min for 2.5 h to finally obtain a modified photo-assisted solvent.

[0105] Example 5

[0106] A wastewater treatment process using ultraviolet light and sodium hypochlorite:

[0107] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 21mJ / cm 2 The wavelength of the UV lamp is 254nm, the irradiation time is 4min, the UV lamp used is a low-pressure mercury lamp, the power is 30W, and the lamp tube spacing is 5cm;

[0108] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added modified sodium hypochlorite, added in an amount of 4mg / L to obtain treated water;

[0109] S3. Sodium thiosulfate was added to the water obtained in step S2 in an amount of 0.17 mg / L to remove excess chlorine from the water to obtain the final treated water sample;

[0110] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0111] S21. Dissolve chitosan in a dilute acetic acid solution and stir at 280 r / min until completely dissolved to form a chitosan solution. The mass ratio of chitosan to ethylenediaminetetraacetic acid in step S22 is 3:1.

[0112] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution. The solution was stirred at 280 r / min to mix the solution uniformly to form a chitosan-EDTA complex solution.

[0113] S23. 45 g of chitosan-EDTA complex solution and 70 g of modified light-assisted solvent were added to 270 g of sodium hypochlorite solution to obtain a mixed solution;

[0114] S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 7.2. The addition process was carried out at 28°C and 280 r / min with stirring to obtain modified sodium hypochlorite.

[0115] The preparation of the modified photo-assisted solvent comprises the following steps:

[0116] S231. 40 g of nano zinc oxide was added to 230 g of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 27 min to obtain a nano zinc oxide solution;

[0117] S232. 16 g of cetyltrimethylammonium bromide was added to the nano-zinc oxide solution and stirred at 330 r / min in a water bath at 60 ° C for 1.5 h to obtain a CTAB-nano-zinc oxide solution;

[0118] S233. Add 50 g of potassium persulfate to the CTAB-nano zinc oxide solution and stir at a speed of 330 r / min for 2.5 h to finally obtain a modified photo-assisted solvent.

[0119] Example 6

[0120] A wastewater treatment process using ultraviolet light and sodium hypochlorite:

[0121] S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 24mJ / cm 2 The wavelength of the UV lamp is 254nm, the irradiation time is 5min, the UV lamp used is a low-pressure mercury lamp, the power is 30W, and the lamp spacing is 5cm;

[0122] S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite in an amount of 5 mg / L to obtain treated water;

[0123] S3. Sodium thiosulfate was added to the water obtained in step S2 in an amount of 0.18 mg / L to remove excess chlorine from the water to obtain the final treated water sample;

[0124] Wherein, the preparation of modified sodium hypochlorite comprises the following steps:

[0125] S21. Dissolve chitosan in a dilute acetic acid solution and stir at 290 r / min until completely dissolved to form a chitosan solution. The mass ratio of chitosan to ethylenediaminetetraacetic acid in step S22 is 3:1.

[0126] S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution. The solution was stirred at 290 r / min to mix the solution uniformly to form a chitosan-EDTA complex solution.

[0127] S23. 45g of chitosan-EDTA complex solution and 75g of modified light co-solvent were added to 280g of sodium hypochlorite solution to obtain a mixed solution;

[0128] S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 7.4. The addition process was carried out at 28°C and a stirring speed of 290 r / min to obtain modified sodium hypochlorite.

[0129] The preparation of the modified photo-assisted solvent comprises the following steps:

[0130] S231. 45 g of nano zinc oxide was added to 240 g of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 28 min to obtain a nano zinc oxide solution;

[0131] S232. 18 g of cetyltrimethylammonium bromide was added to the nano-zinc oxide solution and stirred at 340 r / min in a water bath at 60 ° C for 1.8 h to obtain a CTAB-nano-zinc oxide solution;

[0132] S233. Add 55 g of potassium persulfate to the CTAB-nano zinc oxide solution and stir at a speed of 340 r / min for 2.8 h to finally obtain a modified photo-assisted solvent.

[0133] Comparative Example 1

[0134] Comparative Example 1 differs from Example 1 in that the ultraviolet irradiation treatment in step S1 is omitted in this comparative example, and modified sodium hypochlorite is directly added during the irradiation.

[0135] Comparative Example 2

[0136] Comparative Example 2 differs from Comparative Example 1 in that the amount of modified sodium hypochlorite added in this comparative example is 1 mg / L.

[0137] Comparative Example 3

[0138] Comparative Example 3 differs from Comparative Example 1 in that the amount of modified sodium hypochlorite added in this comparative example is 2 mg / L.

[0139] Comparative Example 4

[0140] Comparative Example 4 differs from Comparative Example 1 in that the amount of modified sodium hypochlorite added in this comparative example is 3 mg / L.

[0141] Comparative Example 5

[0142] Comparative Example 5 differs from Comparative Example 1 in that the amount of modified sodium hypochlorite added in this comparative example is 4 mg / L.

[0143] Comparative Example 6

[0144] Comparative Example 6 differs from Comparative Example 1 in that the amount of modified sodium hypochlorite added in this comparative example is 5 mg / L.

[0145] Comparative Example 7

[0146] Comparative Example 7 is different from Example 1 in that no modified photo-assisted solvent is added in this comparative example.

[0147] Comparative Example 8

[0148] Comparative Example 8 is different from Example 1 in that unmodified sodium hypochlorite solution is added in this comparative example.

[0149] Performance testing:

[0150] 1. Test on the inactivation effect of fecal coliform bacteria

[0151] The treated water samples obtained in Examples 1-6 and Comparative Examples 1-6 were tested according to the Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB18918-2002). The sterilization effect of Example 1-6 after adding modified sodium hypochlorite and reacting for 1 minute is shown in the attached figure. Figure 2 The sterilization effect after adding modified sodium hypochlorite and reacting for 3 minutes is shown in the attached Figure 3The sterilization effect after adding modified sodium hypochlorite and reacting for 5 minutes is shown in the attached Figure 4 , attached Figure 5 The following is a comparison chart of the sterilization effects of three reaction times. Figure 2-4 It can be seen that when the UV-first and UV-second combined with modified sodium hypochlorite disinfection method is used, only 1 mg / L of modified sodium hypochlorite needs to be added and the contact reaction lasts for 1 minute, and the number of fecal coliform bacteria in the effluent can be reduced to 480 CFU / L, reaching the Class A emission standard of the Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB18918-2002). Figure 6 As shown in the figure, when ultraviolet and modified sodium hypochlorite are used for simultaneous disinfection, the dosage of modified sodium hypochlorite needs to be increased to 3 mg / L, so that the fecal coliform count after disinfection can meet the requirements of the above standards.

[0152] The experimental results show that if the ideal disinfection effect is to be achieved, the method of disinfection with UV first and then UV and modified sodium hypochlorite can significantly reduce the dosage of modified sodium hypochlorite, and at the same time show a stronger microbial inactivation ability than the simultaneous disinfection method of UV and modified sodium hypochlorite. This is because in the process of disinfection with UV first and then UV and modified sodium hypochlorite, the ultraviolet light causes a certain degree of damage to the fecal coliform cells, which increases the possibility of modified sodium hypochlorite penetrating the cell wall and oxidizing the protein or phosphate dehydrogenase inside the cell, thereby improving the disinfection efficiency. When ultraviolet light and modified sodium hypochlorite are present in the water at the same time, the hydrolysis product of modified sodium hypochlorite (HClO / ClO-) will produce active oxidative free radicals (HO · ), chlorine atom (Cl·), Cl2 ·- and O ·- These can be used to degrade pollutants in water, a process considered an emerging advanced oxidation process (AOP). The strong oxidizing free radicals produced by these AOPs are rapidly consumed by organic matter in the secondary effluent, depriving them of the opportunity to oxidize with microorganisms, resulting in a reduced bactericidal effect. Therefore, to achieve optimal disinfection results, the dosage of sodium hypochlorite must be increased.

[0153] 2. Three-dimensional fluorescence spectroscopy analysis

[0154] The changes of organic matter components in water samples before and after combined disinfection were determined by three-dimensional fluorescence spectroscopy. The results are shown in the attached figure. Figure 7-9 As shown, with Figure 7 The three-dimensional fluorescence spectrum of the raw water before treatment is shown in the figure below. Figure 8 The three-dimensional fluorescence spectrum of the water sample after treatment in Example 1 is shown in the attached figure. Figure 9This is a three-dimensional fluorescence spectrum of the water sample treated in Comparative Example 1. The peaks in the three-dimensional fluorescence spectrum at excitation wavelengths of 250-280 nm and emission wavelengths <380 nm are associated with soluble microbial metabolites (Region IV). Peaks at excitation wavelengths >280 nm and emission wavelengths >380 nm are associated with humic acids (Region V). The fluorescence intensity values in this graph can be used to infer the content of these substances in the water sample, thereby exploring the changes in each organic component before and after disinfection.

[0155] Figure 5 The experimental results show that in the combined disinfection method, when ultraviolet light and modified sodium hypochlorite are used for simultaneous disinfection, the fluorescence intensity in regions IV and V is significantly reduced compared to the raw water. This indicates that the dissolved microbial metabolites and humic acid substances in the water sample are oxidized and decomposed, losing their fluorescence, resulting in a significant reduction in these two organic components. Under the conditions of UV followed by UV and modified sodium hypochlorite disinfection, the reduction in dissolved microbial metabolites and humic acid substances is significantly weaker than when UV and modified sodium hypochlorite are used simultaneously. This allows more oxidants to participate in the disinfection process, improving disinfection efficiency.

[0156] 3. Photoreactivation test of fecal coliform bacteria

[0157] The effects of different resurrection light intensities on the photoreactivation of fecal coliforms are shown in the attached figure. Figure 10-11 As shown, among which, Figure 10 The following is a line graph showing the photoreactivation rate of fecal coliform bacteria in the water sample treated in Example 1. Figure 11 The following is a line graph showing the photoreactivation rate of fecal coliform bacteria in the water sample treated in Comparative Example 1. Figure 10-11 It can be seen that the resurrection rate of fecal coliform group in water samples after combined disinfection treatment increases with the increase of resurrection light intensity or the extension of illumination time. 2 , 30μm / cm 2 and 45 μm / cm 2 Under the conditions of UV first and then UV and modified sodium hypochlorite synergistic disinfection, the resurrection rates of fecal coliform group were 16.88%, 21.09% and 26.96% respectively. This shows that the stronger the resurrection light intensity, the more energy is provided to the damaged bacteria for photoresurrection, and the corresponding photoresurrection ability is also stronger. In the simultaneous disinfection method of UV and modified sodium hypochlorite, when the resurrection light intensity is 15μm / cm 2 and 30 μm / cm 2 When the resurrection rate of fecal coliform group was less than 25.8% and 24.64%, respectively, the resurrection rate increased with the resurrection light intensity to 45μm / cm 2 , the resurrection rate increases to 30.81%.

[0158] The comparative results show that the resurrection rate of fecal coliform bacteria when disinfected simultaneously with ultraviolet light and modified sodium hypochlorite is higher than that when disinfected with ultraviolet light first and then with the synergistic effect of ultraviolet light and modified sodium hypochlorite. This may be because the damage to fecal coliform bacteria when disinfected first with ultraviolet light and then with the synergistic effect of ultraviolet light and modified sodium hypochlorite is greater, causing most microorganisms to lose the ability to repair DNA dimers, thereby effectively inhibiting the occurrence of microbial photoresurrection and ensuring the safety and stability of effluent microbial indicators.

[0159] 4. NH4 in secondary effluent water quality indicators + - Changes in N and TP

[0160] Combined disinfection method for NH4 + -N and TP removal effects are shown in Figure 12-13 After the combined disinfection treatment, the TP content in the water sample was between 0.06-0.09 mg / L, which was at a relatively low level and did not change significantly, while the NH4 + -N content has been reduced. Among them, UV first and UV second and modified sodium hypochlorite synergistic disinfection, NH4 + -N removal rate is 30.3%; UV and modified sodium hypochlorite disinfection, NH4 + The -N removal rate was 48.5%.

[0161] Experimental data show that simultaneous disinfection with UV and modified sodium hypochlorite shows stronger NH4 + -N removal capacity. This is because during the simultaneous disinfection process of ultraviolet and modified sodium hypochlorite, on the one hand, modified sodium hypochlorite replaces NH4 + -N is converted into chloramine, and ultraviolet light can effectively cleave the N-Cl bond of chloramine. The reaction formula is: NH2Cl+hv→NH2·+·Cl. On the other hand, the hydrolysis product of modified sodium hypochlorite (HClO / ClO - ) will generate hydroxyl radicals (·OH) and ·Cl and other reactive chlorine species (RCS) under ultraviolet irradiation, which is an emerging advanced oxidation process. In this process, the generated ·OH and ·Cl can react with NH4 + -N reacts to convert NH4 + -N is removed from the water. The reaction formula is: OH+NH3→NH2+H2O, Cl+NH3→NH2+H + +Cl - .

[0162] 5. Changes in turbidity in secondary effluent water quality indicators

[0163] Attachment Figure 14-15The figure shows the change in turbidity of the secondary effluent from a sewage treatment plant after combined disinfection treatment. The experimental results indicate that disinfection with UV followed by a synergistic application of UV and modified sodium hypochlorite has virtually no effect on the turbidity of the water sample. However, when UV and modified sodium hypochlorite are used simultaneously for disinfection, turbidity increases slightly with increasing dosage of modified sodium hypochlorite. This increase in turbidity may be due to the strong oxidizing free radicals produced by the advanced oxidation process, which destroy pollutants in the water, breaking down larger particles into smaller ones, thus removing slime. Furthermore, factors influencing turbidity, such as the shape, size, and refractive index of particulate matter in the water, change after disinfection, leading to increased turbidity in the effluent.

[0164] 6. COD and UV in secondary effluent water quality indicators 254 Changes

[0165] Combined disinfection method for COD and UV 254 The removal effect is shown in the attached Figure 16-17 The experimental results show that COD in water samples showed a downward trend after combined disinfection treatment, but UV 254 The removal effect was not obvious. Among them, when the UV-first and UV-second disinfection method was used in conjunction with modified sodium hypochlorite, COD was reduced from 35.42 mg / L to 25.30 mg / L, with a removal rate of 28.6%. 254 From 0.175cm -1 Reduced to 0.172cm -1 , the removal rate is only 1.7%. When UV and modified sodium hypochlorite are disinfected at the same time, the COD removal rate can reach 42.2%. 254 The removal rate increased to 4%.

[0166] Experimental data show that the simultaneous disinfection of UV and modified sodium hypochlorite has a significant effect on COD and UV 254 The removal effect is more significant than disinfection using UV first and then the synergistic effect of UV and modified sodium hypochlorite. Whether it is the oxidation and degradation of organic matter by modified sodium hypochlorite, or the decomposition of some small-molecule organic matter by ultraviolet energy, both only change the structure of the organic matter and cannot completely remove the organic matter from the water by mineralizing it into CO2. However, when UV and modified sodium hypochlorite are disinfected simultaneously, the highly active free radicals generated by the advanced oxidation process can gradually decompose the complex structure of large-molecule organic matter into small-molecule acids, and finally convert them into CO2 and discharge them into the water, significantly achieving the degradation of organic matter.

[0167] The experiments in Comparative Examples 7-8 in which no modified photosolvent was added and unmodified sodium hypochlorite was added proved that the modified sodium hypochlorite and the modified photosolvent in the present application can generate active oxygen and sulfate radicals under the action of ultraviolet light, which synergistically attack the microbial membrane structure with hypochlorous acid, oxidize and degrade complex organic matter, reduce the ineffective consumption of sodium hypochlorite and stabilize the effective chlorine concentration, thereby further improving the degradation efficiency.

[0168] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A wastewater treatment process using ultraviolet light and sodium hypochlorite, characterized in that: The following steps are involved: S1. Use ultraviolet lamp to treat the sewage, and control the ultraviolet dose to 15-25mJ / cm 2 , the wavelength of the ultraviolet lamp is 254nm, and the irradiation time is 1-5min; S2 without stopping the ultraviolet light conditions, the wastewater treated in step S1 was added with modified sodium hypochlorite to obtain treated water; S3. Sodium thiosulfate is added to the water obtained in step S2 to remove excess chlorine in the water to obtain the final treated water sample; Wherein, the preparation of the modified sodium hypochlorite comprises the following steps: S21. Dissolve chitosan in a dilute acetic acid solution and stir until completely dissolved to form a chitosan solution; S22. Ethylenediaminetetraacetic acid was dissolved in deionized water to obtain an EDTA solution which was slowly added to the chitosan solution, stirring while adding the solution to mix uniformly to form a chitosan-EDTA complex solution; S23. 3-5 parts of chitosan-EDTA complex solution and 5-8 parts of modified light co-solvent were added to 20-30 parts of sodium hypochlorite solution to obtain a mixed solution; S24. Sodium bicarbonate was added to the mixed solution to control the pH of the mixed solution at 6.8-7.

5. The addition process was stirred at 25-30 ° C to obtain modified sodium hypochlorite; The preparation of the modified photo-assisted solvent comprises the following steps: S231. 3-5 parts of nano-zinc oxide were added to 20-25 parts of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz for 20-30 min to obtain a nano-zinc oxide solution; S232. 1-2 parts of cetyltrimethylammonium bromide were added to the nano-zinc oxide solution and stirred in a water bath at 60 ° C for 1-2 h to obtain a CTAB-nano-zinc oxide solution; S233. Add 4-6 parts of potassium persulfate to the CTAB-nano zinc oxide solution and stir for 2-3 hours to finally obtain a modified photo-assisted solvent.

2. The process for treating sewage by combining ultraviolet light and sodium hypochlorite according to claim 1, wherein: The mass ratio of chitosan to EDTA in steps S21 and S22 is 3:

1.

3. The process for treating sewage by combining ultraviolet light and sodium hypochlorite according to claim 1, wherein: During the preparation of the modified photo-assisted solvent, the stirring speed is 300-350 r / min.

4. The process for treating sewage by combining ultraviolet light and sodium hypochlorite according to claim 1, wherein: The added amount of the modified sodium hypochlorite is 0.5-5 mg / L.

5. The process for treating sewage by combining ultraviolet light and sodium hypochlorite according to claim 1, wherein: The addition amount of the sodium thiosulfate is 0.1-0.2 mg / L.

6. The process for treating sewage by combining ultraviolet light and sodium hypochlorite according to claim 1, wherein: In step S1 , the ultraviolet lamp is a low-pressure mercury lamp with a power of 30 W and a lamp tube spacing of 5 cm.

7. The process for treating sewage by combining ultraviolet light and sodium hypochlorite according to claim 1, wherein: During the preparation of modified sodium hypochlorite, the stirring speed is 250-300 r / min.

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