System and method for disinfecting island rainwater through cooperation of ultraviolet rays, ozone and microbubbles

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a system and a method for disinfecting island rainwater by ultraviolet, ozone and microbubbles. Starting with an ultraviolet and ozone combined disinfection technology, the process technology is further improved, and a microbubble technology is introduced as an auxiliary aeration means. Due to the fact that a large number of active oxygen species are generated through combination of ultraviolet rays and ozone, due to the existence of microbubbles, the mass transfer efficiency of ozone can be improved, and the sterilization effect can be enhanced by increasing the yield of active free radicals. The method has a relatively high removal effect on pathogenic bacteria in water, the addition of ozone avoids the defect of incomplete ultraviolet disinfection, the addition of microbubbles can increase the yield of active oxygen species in water, and the overall disinfection effect is improved. In addition, the method for generating ozone by irradiating oxygen with ultraviolet rays saves the cost and management energy of equipment such as an ozone generator and an ozone eliminator, so that the equipment required by the technology is small in size and can be suitable for the island environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a system and method for using ultraviolet light and ozone in conjunction with microbubbles to disinfect island rainwater. Background Art

[0002] There are many islands in the world's oceans. Most of them are far away from the land and rely mainly on natural precipitation and shipping for fresh water. Fresh water resources are very limited. Due to the special environment of islands, water resources are relatively scarce. Therefore, it is of great significance to develop an efficient and environmentally friendly rainwater disinfection process. Rainwater has the characteristics of easy collection, low pollution load and simple treatment. Collecting and reusing rainwater from roofs and surface runoff has become an effective solution to supplement freshwater resources and solve the problem of water shortage. Recycled rainwater is generally used for municipal cleaning and landscaping, and can also be used to supplement drinking water supply after purification. Disinfection of island rainwater is an important measure to ensure the safety of domestic water for island residents and prevent water-borne diseases. Since recycled rainwater has a wide range of applications and is directly ingested by the human body when used as drinking water, it must be strictly disinfected to ensure water safety. At present, there are two main types of existing island rainwater purification technologies: (1) Filtration: Remove suspended matter, particulate matter and some organic matter in the water through filters. This method is simple to operate, but it cannot completely remove microorganisms and viruses. (2) Disinfection: Including chlorine disinfection, ozone disinfection and ultraviolet disinfection. These methods can effectively kill microorganisms and viruses in water and ensure water quality safety.

[0003] The main pollution in the reused rainwater comes from organic pollutants and pathogenic microorganisms in surface runoff. Therefore, rainwater disinfection should ensure effective disinfecting of pathogenic microorganisms while preventing the generation of disinfection by-products as much as possible. However, traditional chlorine disinfection is prone to produce toxic disinfection by-products. Although ultraviolet disinfection can kill bacteria by destroying nucleic acids, the effect of ultraviolet disinfection is affected by factors such as turbidity and transmittance of the influent water, and ultraviolet light does not have the ability to disinfect continuously, and photoreactivation is prone to occur after disinfection. Although ozone does not have the ability to disinfect continuously, it can directly destroy the cell wall, nucleic acid, protein and other structures or substances of pathogens, inhibit bacterial metabolism and reproduction, and thus avoid the occurrence of photoreactivation, which can make up for the shortcomings of ultraviolet disinfection to a certain extent. However, the operation and maintenance costs of ozone disinfection in actual applications are relatively high. Combined with the geographical environment and economic conditions of the island, ozone disinfection technology is not the optimal solution for the disinfection of rainwater reuse on the island. It can be seen that although the traditional disinfection method has a good disinfection effect, it has the problem of secondary pollution of water quality, and the equipment cost is high and the operation and maintenance are complicated. Therefore, it is of great practical significance to study a new environmentally friendly and effective rainwater disinfection process. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a disinfection process for island rainwater. The disinfection process using ultraviolet ozone and microbubbles solves the secondary pollution problem of water quality caused by traditional disinfection methods. It is a more environmentally friendly and safe disinfection method. The required equipment is small in size, which meets the special needs of rainwater disinfection in the small geographical environment of islands far away from the mainland.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides a process for disinfecting rainwater on an island using ultraviolet rays and ozone in collaboration with microbubbles, comprising the following steps:

[0007] S1. Construction of a disinfection device: The disinfection device includes a quartz tube, a water storage device, a water inlet, an air inlet, an ultraviolet lamp, a water pump, a venturi injector, a microbubble injector, a water outlet and an air outlet; the ultraviolet lamp is arranged on the inner top wall of the quartz tube, and the microbubble injector is placed on the inner bottom wall of the quartz tube to generate microbubbles;

[0008] S2. Rainwater collection: connect the local rainwater collection pool and rainwater pipe network through rainwater pipes to collect rainwater into water storage devices;

[0009] S3. Trial operation: The disinfection device itself is not equipped with an ozone generator. The ozone is generated by irradiating the air with ultraviolet rays. Therefore, it needs to be pre-operated for a period of time to stabilize the amount of ozone produced. Open the water inlet and the water pump, pump the water in the water storage device into the Venturi ejector, and the water sample is injected into the water inlet by the Venturi ejector at an increased speed. After the water sample fills the inside of the quartz tube, open the air inlet and let air into the water. Connect flow meters to the water inlet and air inlet valves to monitor the flow of water and air. After the water flow rate reaches 1-4L / min and the air flow rate reaches 1-3L / min, turn on the ultraviolet lamp until the flow rate at the air outlet is stable, indicating that ozone can be stably generated in the device.

[0010] S4. Formal operation: After the trial operation, turn on the microbubble ejector to eject water and air into the quartz tube together. Under the action of the microbubble ejector, the bubbles in the water become fine and dense, and the bubbles contain ozone, which slowly rises with the water flow in the device. Under the irradiation of ultraviolet rays, ozone and ultraviolet rays work together to play a synergistic sterilization role; ultraviolet rays act on the genetic material of pathogens, which can destroy DNA to disrupt the normal physiological activities of bacteria, and ozone has an oxidizing effect on various substances in bacterial cells, including cell membranes, proteins and other substances. The combination of the two can prevent the regeneration of pathogens;

[0011] S5. Water discharge and testing: Samples are taken at the water outlet to test whether the various indicators of the water discharge meet the standards. The water that meets the standards is connected to the water supply network for reuse. If it does not meet the standards, it needs to be re-entered into the return pipe and returned to the rainwater collection pool for further treatment.

[0012] In view of the different shortcomings of single disinfection measures, it is considered to use a combined process for disinfection. At the same time, due to the limitation of the island area, the size of the disinfection equipment should be small. In general, sewage disinfection will consider the use of ultraviolet + ozone disinfection devices, but the size of this device is large and not suitable for construction on small islands. In order to simplify the equipment, directly using ultraviolet lamps as ozone generators to form a combined ultraviolet + ozone sterilization device can greatly reduce the size of the equipment. At the same time, in order to make full use of the disinfection ability of ozone, microbubble technology is also introduced, which has the advantages of high specific surface area, high stability, long residence time and high gas solubility rate. The microbubble injector can make the generated ozone microbubbles evenly dispersed in the water, thereby improving the disinfection effect and promoting the degradation of organic matter. Therefore, the combined process of the present invention not only reduces the size of the equipment, fits the limited land area of ​​the island, but also avoids secondary pollution. The addition of microbubble technology has further improved the disinfection effect of the ultraviolet + ozone combined sterilization process.

[0013] The present invention provides a process for disinfecting rainwater on islands by combining ultraviolet light, ozone and microbubbles. This combination technology is not common in the prior art and is novel. At the same time, the three technologies of ultraviolet light, ozone and microbubbles are used in a coordinated manner. Unlike traditional chlorine disinfection or ozone disinfection, this combination innovates the method of rainwater disinfection and is creative. In addition, the present invention is particularly suitable for remote areas such as islands, which are usually faced with the challenges of water scarcity and high environmental protection requirements. The rainwater disinfection process equipment of the present invention has low cost and simple operation and maintenance, and can effectively ensure the safety of domestic water for island residents, meeting practical requirements.

[0014] Preferably, the air outlet and air inlet are arranged on the top of the quartz tube, the water inlet is arranged on the lower side wall of the quartz tube, and the water outlet is arranged on the upper side wall of the quartz tube, so that the water flow of the device is in a bottom-in and top-out manner, and the air flow is in a top-in and top-out manner.

[0015] Preferably, the air outlet is connected to the water inlet via a venturi ejector, the water storage device is connected to the water inlet via a water pump and a venturi ejector, and the water inlet is connected to the micro bubble ejector.

[0016] Preferably, the quartz tube is a transparent resin cylindrical cell body.

[0017] Preferably, the ultraviolet lamp can emit two types of ultraviolet light with wavelengths of 185nm and 254nm.

[0018] Preferably, the rainwater in the water storage device is filtered before disinfection to remove suspended matter and sediment visible to the naked eye in the rainwater, so that the incoming rainwater meets the disinfection requirements.

[0019] More preferably, the rainwater in the water storage device is filtered by a coarse grid and a fine grid in sequence, wherein the aperture of the coarse grid is 40-60 mm, and the aperture of the fine grid is 1-3 mm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Traditional disinfection technologies mainly include chlorine disinfection and ozone disinfection, but these methods have certain limitations in island environments. Among them, ultraviolet disinfection requires a long time and high energy consumption when used alone. For pathogenic bacteria such as Escherichia coli, photoreactivation will also occur, and it does not have the ability to continuously disinfect; ozone disinfection equipment is complex, and ozone has poor stability and is very easy to decompose. Its half-life is only 1 hour at most, and it is difficult to exist continuously in the reactor. It is very easy to convert into oxygen, thereby reducing the sterilization effect. If ultraviolet and ozone disinfection technologies are used in combination, in this technology, the addition of ozone can directly destroy Escherichia coli DNA and avoid photoreactivation after ultraviolet disinfection; the addition of ultraviolet rays can make ozone produce more active free radicals (such as hydroxyl radicals) in the water to participate in the disinfection process. Escherichia coli is simultaneously irradiated by ultraviolet light, directly oxidized by ozone, and oxidized by free radicals. The three effects work synergistically to enhance the sterilization effect. However, the entire equipment used in this technology requires a large volume, which is not suitable for the small island and the geographical environment far away from the mainland.

[0022] To this end, the present invention starts with the UV + ozone combined disinfection technology, further improves the process technology, and introduces microbubble technology as an auxiliary aeration method. This is because the combination of ultraviolet and ozone produces a large number of active oxygen species, and the presence of microbubbles can not only improve the mass transfer efficiency of ozone itself, but also increase the production of active free radicals to enhance the sterilization effect.

[0023] In general, the technical solution of the present invention has the following advantages:

[0024] (1) This method has a high removal effect on pathogens in water, and the addition of ozone avoids the disadvantage of incomplete ultraviolet disinfection.

[0025] (2) The addition of microbubbles can increase the production of reactive oxygen species in water and improve the overall disinfection effect.

[0026] (3) The method of using ultraviolet rays to irradiate oxygen to produce ozone saves the cost and management effort of equipment such as ozone generators and ozone eliminators, which makes the equipment required for this technology small in size and suitable for island environments.

[0027] (4) The required disinfection equipment mainly includes quartz tubes, water storage devices, ultraviolet lamps, water pumps, venturi injectors, and microbubble injectors. They can be set up and moved at any time and are suitable for rainwater disinfection needs in different locations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of an ozone-ultraviolet combined with microbubble disinfection device;

[0029] Figure 1 In the figure, 1-ultraviolet lamp, 2-quartz tube, 3-air inlet, 4-air outlet, 5-venturi ejector, 6-water inlet, 7-water outlet, 8-micro bubble ejector, 9-water pump, 10-water reservoir.

[0030] Figure 2 The sterilization rates of different disinfection methods (the combination in the figure is ultraviolet light + ozone; based on paired t-test, "*" indicates significant difference, and "**" indicates extremely significant difference). DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0033] The present invention discloses a process for disinfecting rainwater on an island using ultraviolet rays and ozone in collaboration with microbubbles. The main process flow includes the following steps:

[0034] (1) Rainwater collection: Connect to the local rainwater network through rainwater pipes, so that rainwater flows into the rainwater collection pool as the source of water flow.

[0035] (2) Filtration: Before the rainwater flows into the disinfection device, a coarse grid (aperture 50 mm) and a fine grid (aperture 1.5 mm) are sequentially arranged at the outlet of the rainwater collection pool along the direction of the water flow to filter out the leaves and other substances or visible particles and suspended matter contained in the rainwater. Filtration is beneficial to the subsequent disinfection treatment. On the one hand, because the penetration of ultraviolet disinfection in water is greatly affected by the turbidity of water, filtration can filter out the suspended matter on the surface of rainwater and in the water, and prevent the rough surface of solid matter from scattering a large amount of ultraviolet light, resulting in its inability to play a stable disinfection role; on the other hand, because the particles in the rainwater will cause a certain degree of wear on the wall of the device, filtration is beneficial to the maintenance of the device, extending the service life of the device and reducing the cost of device maintenance. Moreover, the solid waste generated after filtration is limited in volume and harmless, and can be directly landfilled.

[0036] (3) Pre-operation stage: The filtered rainwater flows into the device under the suction of the water pump. In order to make the water vapor fully contact inside the device and prolong its residence time, the water flow of the device adopts the method of inflow from the bottom and outflow from the top, and the air flow adopts the method of inflow from the top and outflow from the top. Since there is no ozone in the device initially, it is necessary to generate oxygen by irradiating ultraviolet light.

[0037] ①Open the water inlet first, and the water pump presses the rainwater into the Venturi ejector. The rainwater is accelerated by the Venturi ejector and then flows into the device through the water inlet.

[0038] ② After the rainwater fills the device and flows out from the water outlet at the top, open the air inlet to fill the water with air. After the air flows out from the air outlet, the air outlet is connected to the Venturi ejector through the air delivery pipe. At this time, the Venturi ejector can eject water and air at the same time. The air re-enters the device through the water inlet to make the water and air evenly mixed. Adjust the flowmeters of the water inlet and air inlet valves to make the water flow rate 2L / min and the air flow rate 1.2L / min.

[0039] ③ Turn on the ultraviolet light. Under the action of high-energy ultraviolet rays, the oxygen in the air is decomposed into active oxygen atoms, and then recombined into ozone. There is also a flow meter on the outlet valve. When the air flow rate at the outlet is observed to be stable, it means that ozone can be stably generated in the device.

[0040] ④ Previously, the water from the outlet could not strictly meet the standards and could not be discharged directly, so it needed to be returned to the rainwater collection pool through the return pipe for reprocessing. After the pre-operation phase, ozone can be stably produced in the device, and then the microbubble ejector can be turned on to start formally treating rainwater.

[0041] (4) Operation phase: Turn on the microbubble ejector at the bottom of the device, connect the ejector to the water inlet, and eject water and air together. Under the action of the microbubble ejector, the bubbles in the water become fine and dense, and the bubbles contain ozone, which slowly rises with the water flow in the device. Under ultraviolet irradiation, ozone and ultraviolet rays work together to exert a synergistic sterilization effect. Ultraviolet rays act on the genetic material of pathogens, which can destroy DNA and disrupt the normal physiological activities of bacteria. Ozone has an oxidizing effect on various substances in bacterial cells, including cell membranes, proteins and other substances. The combination of the two can prevent the regeneration of pathogens.

[0042] (5) Water discharge and testing: Sampling is performed at the outlet to test the content of pathogenic microorganisms, mainly Escherichia coli. The discharge standard is determined according to the local water quality conditions and the actual use of the recycled water. If it does not meet the standard, it needs to be re-entered into the return pipe and returned to the rainwater collection pool for re-treatment. If it has met the standard, it can be discharged normally and connected to the local water supply network for various purposes. Among them, the discharge standard complies with the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB18918-2002). For reused water, the Class A standard is implemented; considering the special geographical environment of the island, the water quality standard after discharge can also refer to the "Seawater Quality Standard" (GB3097-1997).

[0043] In order to further clearly present the present invention and verify the disinfection effect of the present invention, a detailed description is given below in the form of embodiments.

[0044] The structure of the disinfection device used in this embodiment is as follows Figure 1 As shown, the disinfection device includes a quartz tube 2, a water reservoir 10, a water inlet 6, an air inlet 3, an ultraviolet lamp 1, a water pump 9, a venturi ejector 5, a micro bubble ejector 8, a water outlet 7 and an air outlet 4. The air outlet 4 and the air inlet 3 are arranged at the top of the quartz tube 2, the water inlet 6 is arranged at the lower side wall of the quartz tube 2, the water outlet 7 is arranged at the upper side wall of the quartz tube 2, and the ultraviolet lamp 1 is arranged at the inner top wall of the quartz tube 2; the air outlet 4 is connected to the water inlet 6 through the venturi ejector 5, the water reservoir 10 is connected to the water inlet 6 through the water pump 9 and the venturi ejector 5, and the water inlet 6 is connected to the micro bubble ejector 8; the quartz tube 2 is a transparent resin cylindrical pool body with a diameter of 56 mm, the water flow adopts a bottom-in-top-out method, and the air flow adopts a top-in-top-out method. The model of the ultraviolet lamp 1 is GPH0212T5L, Heraeus, which can emit two types of ultraviolet light with wavelengths of 185nm and 254nm. The microbubble injector 8 is placed on the inner bottom wall of the quartz tube 2 to generate microbubbles. The venturi injector 5 is a SN-Ⅲ gas-liquid mixer purchased from Ximen Electromechanical Technology Co., Ltd.; the microbubble injector 8 is a jet-type micro-nano bubble generator NANO-JET-01T purchased from Shanghai Xingheng Technology Co., Ltd.

[0045] The instruments and reagents required for this example include:

[0046] (1) Experimental instruments: electronic balance, portable pH meter, UVC ultraviolet light intensity tester, autoclave, shaker, centrifuge, ozone generator, constant temperature box, 0.45 μm filter membrane, culture dish.

[0047] (2) Experimental reagents: tryptone, yeast extract, sodium chloride, Escherichia coli, nitrogen, and eosin-methylene blue stain.

[0048] The main steps of this embodiment are as follows:

[0049] 1. Sampling: The water sample used in the water storage tank 10 comes from the surface runoff of an island in the South China Sea 30 minutes after the end of rainfall. It is stored in a bucket and transported back to the laboratory. After standing for 40 minutes, the upper clear liquid is gently scooped out for standby use, and the sediment and other substances obtained by precipitation are discarded.

[0050] 2. Sample pretreatment: In order to explore the sterilization effect, it is necessary to artificially add pathogens to simulate the high pathogen content of rainwater. Here, Escherichia coli is added.

[0051] 2.1. Escherichia coli DH5α, strain accession number: ATCC15597, was donated by the School of Life Sciences, Sun Yat-sen University.

[0052] 2.2. Use an electronic balance to weigh 10g of tryptone, 5g of yeast extract, and 10g of sodium chloride, add them to 1L of pure water to prepare LB liquid culture medium, and divide them into 5 250mL conical flasks, each containing 200mL of culture medium. After the 5 flasks are sealed with gauze strips, they are placed in a pressure cooker and sterilized at 121°C for 20min. After cooling to room temperature, 10mg of powdered Escherichia coli strains are weighed and inoculated in a sterile bench. Only one conical flask is inoculated, and the other four are used for subculture. The conical flasks are numbered 1, 2, 3, 4, and 5 according to the time sequence of cultivation. Among them, culture medium No. 1 is placed in a shaker at a temperature of 37°C and a relative humidity of 75% for 24h, and the other culture media are refrigerated.

[0053] 2.3. Subculture: Take out liquid culture medium No. 1 from the shaker, gently shake the conical flask to make the bacteria fall off the flask wall and fall into the culture medium, take 100mL of the mixed culture solution and place it in a centrifuge tube, then put it into a centrifuge and centrifuge it at 4000r / min for 10 minutes at room temperature to precipitate the cells. Then take the cells out of the centrifuge tube with a rubber-tipped pipette and discard the old culture medium on the upper layer. Resuspend the removed cells in culture medium No. 2 under a sterile environment, then continue to place them in the shaker and culture them at 37°C for 24 hours. This completes the first generation of subculture. Repeat the above operation 4 times, complete 4 subcultures, and obtain the fourth generation of Escherichia coli.

[0054] 2.4. After the fourth subculture, take 100 mL of the bacterial solution in the No. 5 conical flask into a centrifuge tube, centrifuge it at 4000 r / min for 10 min at room temperature, discard the supernatant, add the concentrated E. coli into 10 L of rainwater sample with a rubber-tipped pipette, stir evenly with a glass rod to obtain recycled rainwater with a high E. coli concentration, and store it in a water reservoir.

[0055] 3. Formal test:

[0056] 3.1. Explore the sterilization effect of the device under ultraviolet light irradiation only: turn on the water pump 9, pump the water in the water reservoir 10 into the venturi ejector 5, and the water sample is ejected into the water inlet 6 by the venturi ejector 5 at an increased speed. After the water sample fills the inside of the device (quartz tube 2), open the air inlet 3 to introduce nitrogen into the water, and adjust the valve to stabilize the water flow rate at 2L / min and the air flow rate at 1.2L / min. At this time, turn on the ultraviolet lamp 1, keep the microbubble ejector 8 in the closed state, and take 5mL of water sample from the water inlet 6 and detect the number of coliform bacteria. This value can be used as the original number of coliform bacteria in the water sample. Then let the device run continuously for 24h at room temperature. After 24h, take 5mL of water sample from the water outlet 7 and detect the number of coliform bacteria. Due to the limited water sample and the fast water flow rate, in order to make the ultraviolet rays in the device fully contact with Escherichia coli, the water output of the device needs to be connected to the water reservoir 10 through the water outlet pipe during this period of time for repeated reuse. Although the ultraviolet lamp 1 can emit ultraviolet light of two wavelengths, 185 nm and 254 nm, since the nitrogen introduced is an inert gas, the interior of the device is in an anaerobic and oxygen-deficient state, and thus almost no ozone is generated.

[0057] 3.2. Investigate the sterilization effect of the device under the conditions of ultraviolet light + microbubbles: After the experiment in part 3.1, replace the water sample in the water reservoir 10 with a new one. The subsequent experimental steps and operating conditions are the same as those in part 3.1. However, based on part 3.1, the microbubble injector 8 at the bottom of the device is turned on. At this time, both ends of the injector can evenly spray water containing fine bubbles. Finally, the number of coliform bacteria at the outlet is detected after 24 hours.

[0058] 3.3. Explore the sterilization effect of the device under ozone conditions only: After the experiment in part 3.2 is completed, the water in the water reservoir 10 is replaced. Turn on the water pump 9, pump the water in the water reservoir 10 into the venturi ejector 5, and the water sample is ejected into the water inlet 6 by the venturi ejector 5 at an increased speed. After the water sample fills the inside of the device, open the air inlet 3, and connect the ozone generator at the air inlet 3 to pass ozone into the water to maintain the ozone production at about 36.2 mg / h. By adjusting the valve, the water flow rate is stabilized at 2L / min and the air flow rate is stabilized at 1.2L / min. At this time, keep the ultraviolet lamp 1 and the microbubble ejector 8 in the closed state, and then let the device run continuously for 24 hours at room temperature. After 24 hours, take 5mL of water sample from the water outlet 7 and detect the number of coliform bacteria. Since the water sample is limited and the water flow rate is fast, in order to make the ozone in the device fully contact with the E. coli, the water outlet of the device needs to be connected back to the water storage tank 10 through the water outlet pipe for repeated reuse during this period of time.

[0059] 3.4. Explore the sterilization effect of the device under the condition of ozone + microbubbles: After the experiment in part 3.3, the water tank 10 is replaced with a new water sample. The subsequent experimental steps and operating conditions are the same as those in part 3.3, but on the basis of part 3.3, the microbubble injector 8 at the bottom of the device is in the open state, and the two ends of the injector can evenly spray water containing fine bubbles. Then, the number of coliform bacteria at the outlet is tested after 24 hours.

[0060] 3.5. Explore the sterilization effect of the device under ultraviolet + ozone conditions: After the experiment in part 3.4 is completed, the water in the water reservoir 10 is replaced. Turn on the water pump 9, pump the water in the water reservoir 10 into the venturi ejector 5, and the water sample is ejected into the water inlet 6 by the venturi ejector 5 at an increased speed. After the water sample fills the inside of the device, open the air inlet 3 to introduce air into the water, and adjust the valve to stabilize the water flow rate at 2L / min and the air flow rate at 1.2L / min. At this time, turn on the ultraviolet lamp 1, keep the microbubble ejector 8 in the closed state, and then let the device run continuously for 24 hours at room temperature. After 24 hours, take 5mL of water sample from the water outlet 7 and detect the number of coliform bacteria. Due to the limited water sample and the fast water flow rate, in order to make the ultraviolet rays in the device fully contact with Escherichia coli, the water outlet of the device needs to be connected to the water reservoir 10 through the outlet pipe for repeated reuse during this period of time. The ultraviolet lamp 1 can emit ultraviolet light of two wavelengths, 185nm and 254nm, and has high energy, and can decompose oxygen in the air and reorganize it into ozone (the amount produced is about 38.52mg / h).

[0061] 3.6. Explore the sterilization effect of the device under the conditions of ultraviolet light + ozone + microbubbles: After the experiment in part 3.5, the water reservoir 10 was replaced with a new water sample. The subsequent experimental steps and operating conditions were the same as those in part 3.5, but based on part 3.5, the microbubble injector 8 at the bottom of the device was in an open state, and the two ends of the injector could evenly spray water containing fine bubbles. Then, the number of coliform bacteria at the outlet 7 was tested 24 hours later.

[0062] 4. Detection: The number of coliform bacteria is determined by the membrane filter method. The main steps of the membrane filter method are as follows:

[0063] 4.1. Water sample pretreatment: Before or after each experiment, use a 10mL measuring cylinder to take 5mL of water from the water inlet or outlet, then dilute the water sample 1000 times with sterile high-purity water, and take 100mL of the diluted water sample from the 5L dilution solution and place it in a 250mL beaker.

[0064] 4.2. Filtration: Prepare a filter membrane with a pore size of 0.45μm in advance in the filtration funnel, drain with a glass rod, slowly pour the water sample in the beaker into the filtration funnel, turn on the filter switch, and wait for the water to be drained. A layer of bacterial film covered with Escherichia coli will adhere to the filter membrane. The membrane is recorded as the inlet group and the outlet group according to the inlet and outlet water.

[0065] 4.3. Staining culture: After filtration, turn the filter membrane with E. coli adhered to it upside down and place it in an agar culture dish containing 5 mL of eosin-methylene blue dye, and then place it in a 37°C incubator for continuous culture for 24 hours. After 24 hours, read the number of colonies on the two filter membranes. One colony is one dot, which appears black or purple-black, with a pink halo around it.

[0066] 4.4. The negative logarithm of the ratio of the number of colonies on the filter membrane of the effluent group to that on the filter membrane of the inlet group, that is, the negative logarithm of the ratio of the number of colonies before and after sterilization (unit: CFU / 100mL) indicates the sterilization effect.

[0067] 5. Experimental results:

[0068] Figure 2 This is a sterilization rate bar graph obtained by the negative logarithm of the ratio of the number of E. coli colonies before and after sterilization in each group. From left to right, the bar graph is the 6 groups of data arranged in the experimental order in Part 3. Based on this graph, the following conclusions can be drawn:

[0069] (1) Comparing Experiment 3.1 with Experiment 3.2, the sterilization rate of Experiment 3.1 was 2.65, and the result of Experiment 3.2 was 4.35. After t-test calculation, it was found that there was a significant difference in the data, indicating that the sterilization rate was significantly improved after the addition of microbubbles. The sterilization effect was: UV+microbubbles>UV.

[0070] (2) Comparing Experiment 3.3 with Experiment 3.4, the sterilization rate of Experiment 3.3 was 2.46, and the result of Experiment 3.4 was 0.80. After t-test calculation, it was found that there was a significant difference in the data, indicating that after the addition of microbubbles, the sterilization rate was significantly inhibited. The sterilization effect was: ozone>ozone+microbubbles.

[0071] (3) Comparing Experiment 3.5 with Experiment 3.6, the sterilization rate of Experiment 3.5 was 4.20, and the result of Experiment 3.6 was 6.43. After t-test calculation, it was found that there was a significant difference in the data, indicating that after the addition of microbubbles, the sterilization rate was significantly inhibited. The sterilization effect was: UV + ozone + microbubbles > UV + ozone.

[0072] (4) Comparing Experiment 3.1, Experiment 3.3 and Experiment 3.5, it was found that the sterilization effect was: UV+ozone>UV>ozone.

[0073] (5) Comparing Experiment 3.2, Experiment 3.4 and Experiment 3.6, it was found that the sterilization effect was: UV + ozone + microbubbles > UV + microbubbles > ozone + microbubbles.

[0074] The above results show that the combined disinfection method of ultraviolet light + ozone + microbubbles can effectively kill Escherichia coli and achieve the best disinfection effect.

[0075] In summary, the present invention, on the one hand, uses microbubble technology, and uses experiments to prove that microbubbles can promote the combined disinfection of ultraviolet and ozone. On the other hand, the ozone used in the present invention is not generated by an ozone generator like traditional ozone disinfection technology, but is generated by ultraviolet radiation of the air. This saves the purchase and energy consumption of the ozone generator in the entire technical process, which meets the special needs of rainwater disinfection in the small geographical environment of the island and far away from the mainland.

[0076] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A process for disinfecting rainwater on islands using ultraviolet rays and ozone in combination with microbubbles, characterized in that: The following steps are involved: S1. Construction of a disinfection device: The disinfection device includes a quartz tube, a water storage device, a water inlet, an air inlet, an ultraviolet lamp, a water pump, a venturi injector, a microbubble injector, a water outlet and an air outlet; the ultraviolet lamp is arranged on the inner top wall of the quartz tube, and the microbubble injector is placed on the inner bottom wall of the quartz tube to generate microbubbles; S2. Rainwater collection: connect the local rainwater collection pool and rainwater pipe network through rainwater pipes to collect rainwater into water storage devices; S3, test run: open the water inlet and the water pump, pump the water in the water storage device into the venturi ejector, the water sample is ejected into the water inlet by the venturi ejector at an increased speed, after the water sample fills the inside of the quartz tube, open the air inlet to let air into the water, after the water flow rate reaches 1-4L / min, the air flow rate reaches 1-3L / min, turn on the ultraviolet lamp to irradiate until the flow rate at the air outlet is stable, indicating that ozone can be stably generated in the device; S4. Formal operation: After the trial operation, turn on the microbubble ejector to eject water and air into the quartz tube. Under the action of the microbubble ejector, the bubbles in the water become fine and dense, and the bubbles contain ozone, which slowly rises with the water flow in the device. Under the irradiation of ultraviolet rays, ozone and ultraviolet rays work together to exert a synergistic sterilization effect; S5. Water outlet and testing: Samples are taken at the water outlet to test whether the various indicators of the water outlet meet the standards. The water outlet that meets the standards is connected to the water supply network for reuse.

2. The process for disinfecting rainwater on islands using ultraviolet-ozone synergistic microbubbles according to claim 1 is characterized in that: The air outlet and air inlet are arranged on the top of the quartz tube, the water inlet is arranged on the lower side wall of the quartz tube, and the water outlet is arranged on the upper side wall of the quartz tube, so that the water flow of the device is in the bottom-in and top-out mode, and the air flow is in the top-in and top-out mode.

3. The process for disinfecting rainwater on islands using ultraviolet-ozone synergistic microbubbles according to claim 1 is characterized in that: The air outlet is connected to the water inlet through a venturi ejector, the water storage device is connected to the water inlet through a water pump and a venturi ejector, and the water inlet is connected to the micro bubble ejector.

4. The process for disinfecting rainwater on islands using ultraviolet-ozone synergistic microbubbles according to claim 1 is characterized in that: The quartz tube is a transparent resin cylindrical pool body.

5. The process for disinfecting rainwater on islands using ultraviolet-ozone synergistic microbubbles according to claim 1 is characterized in that: The ultraviolet lamp can emit two types of ultraviolet light with wavelengths of 185nm and 254nm.

6. The process for disinfecting rainwater on islands using ultraviolet-ozone synergistic microbubbles according to claim 1 is characterized in that: The rainwater in the water storage device is filtered before disinfection to remove suspended matter and sediment visible to the naked eye in the rainwater, so that the incoming rainwater meets the disinfection requirements.

7. The process for disinfecting rainwater on islands using ultraviolet light and ozone in collaboration with microbubbles according to claim 6 is characterized in that: The rainwater in the water storage device is filtered using a coarse screen and a fine screen in turn.

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