A system and method for island rainwater disinfection by ultraviolet ozone and micro-bubbles

Abstract

The present application belongs to the technical field of sewage treatment, and particularly relates to a system and method for island rainwater disinfection by using ultraviolet ozone and micro-bubbles. The present application improves the process technology by using ultraviolet and ozone combined disinfection technology, and introduces micro-bubble technology as an auxiliary aeration method. This is because the combination of ultraviolet and ozone generates a large amount of active oxygen species, and the presence of micro-bubbles not only improves the mass transfer efficiency of ozone itself, but also increases the yield of active free radicals to strengthen the sterilization effect. The method has a high removal effect on pathogenic bacteria in water. The addition of ozone avoids the incomplete disinfection of ultraviolet disinfection, and the addition of micro-bubbles increases the yield of active oxygen species in water, thereby improving the overall disinfection effect. In addition, the method of generating ozone by irradiating oxygen with ultraviolet light saves the cost and management effort of ozone generators and ozone eliminators and other equipment, which makes the required equipment small in size and suitable for island environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a system and method for island rainwater disinfection by using ultraviolet ozone and micro-bubbles. BACKGROUND

[0002] In the global sea area, there are a large number of islands, most of which are far away from the land, and mainly rely on natural precipitation and shipping to obtain fresh water, so the fresh water resources are very limited. Due to the special island environment and the relative scarcity of water resources, it is of great significance to develop an efficient and environmentally friendly rainwater disinfection process. Rainwater has the characteristics of convenient collection, low pollution load and simple treatment, and the collection and reuse of roof and surface runoff rainwater has become an effective solution to supplement fresh water resources and solve water shortage problems. Reused rainwater is generally used for municipal cleaning and landscaping, and can also be used to supplement drinking water supply after purification. Island rainwater disinfection is an important measure to ensure the safety of island residents' domestic water and prevent water-borne diseases. Since the application of reused rainwater is wide and it is directly taken by the human body when used as drinking water, strict disinfection must be carried out to ensure water safety. At present, there are mainly two kinds of existing island rainwater purification technologies: (1) filtration: removing suspended solids, particulate matter and part of organic matter in water through a filter. This method is simple to operate, but 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 to ensure water safety.

[0003] The main pollution in reused rainwater comes from organic pollutants and pathogenic microorganisms in surface runoff. Therefore, rainwater disinfection should not only ensure the effective killing of pathogenic microorganisms, but also prevent the generation of disinfection by-products as much as possible. However, traditional chlorine disinfection is easy to produce toxic disinfection by-products, ultraviolet disinfection can kill bacteria by destroying nucleic acids, but the effect of ultraviolet disinfection is affected by factors such as turbidity and transmittance of the incoming water, and ultraviolet light does not have sustained disinfection capacity and is prone to photoreactivation after disinfection. Although ozone does not have sustained disinfection capacity, it can directly destroy the cell wall, nucleic acid, protein and other structures or substances of pathogenic bacteria, inhibit bacterial metabolism and reproduction, and thus avoid the occurrence of photoreactivation, which can make up for the deficiency of ultraviolet disinfection to a certain extent. However, the operation and maintenance cost of ozone disinfection is relatively high in actual application, and combined with the geographical environment and economic conditions of islands, ozone disinfection technology is not the optimal solution for island rainwater reuse disinfection. It can be seen that although the traditional disinfection method has 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 complex. Therefore, it is of great practical significance to study a new type of rainwater disinfection process which is environmentally friendly and has remarkable effect. SUMMARY

[0004] To overcome the shortcomings of the existing technology, this invention proposes a disinfection process for rainwater in islands. The disinfection process using ultraviolet ozone in conjunction with microbubbles solves the problem of secondary pollution of water quality caused by traditional disinfection methods. It is also a more environmentally friendly and safer disinfection method. The required equipment is small in size and meets the special needs of rainwater disinfection in the geographical environment of islands that are small and far from the mainland.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a process for disinfecting rainwater from islands using ultraviolet ozone and microbubbles, comprising the following steps:

[0007] S1. Construction of the 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 placed 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 harvesting: Rainwater is collected into a storage device by connecting the local rainwater collection pond and rainwater pipe network through rainwater pipes;

[0009] S3. Trial Operation: The disinfection device itself is not equipped with an ozone generator; the ozone is generated by ultraviolet radiation of the air. Therefore, it needs to be run for a period of time to allow the ozone production to stabilize. Open the water inlet and turn on the water pump to pump the water from the storage device into the Venturi ejector. The water sample is accelerated and sprayed into the water inlet by the Venturi ejector. After the water sample fills the quartz tube, open the air inlet to introduce air into the water. Connect flow meters to the water inlet and air inlet valves to monitor the water and air flow rates. When the water flow rate reaches 1-4 L / min and the air flow rate reaches 1-3 L / min, turn on the ultraviolet lamp until the air outlet flow rate stabilizes, indicating that ozone can be stably generated in the device.

[0010] S4. Formal Operation: After trial operation, turn on the microbubble jet injector to spray water and air into the quartz tube together. Under the action of the microbubble jet injector, the bubbles in the water become fine and contain ozone. They slowly rise with the water flow in the device. Under ultraviolet irradiation, ozone and ultraviolet light work together to exert a synergistic sterilization effect. Ultraviolet light targets the genetic material of pathogens and can damage DNA to disrupt the normal physiological activities of bacteria. Ozone has an oxidizing effect on various substances in bacterial cells, including cell membranes and proteins. The combination of the two can prevent the regeneration of pathogens.

[0011] S5, water outlet and detection: sampling at the water outlet to detect whether each index of the effluent meets the standard, and the effluent meeting the standard is connected to the water supply network for reuse.If it does not meet the standard, it needs to be returned to the rainwater collection tank for further treatment.

[0012] In view of the different deficiencies of single disinfection measures, a combined process is considered for disinfection, and meanwhile, limited by the island area, the volume of the disinfection equipment is small. Generally, ultraviolet + ozone disinfection device is considered for sewage disinfection, but the volume of the device is large, which is not suitable for small islands. In order to simplify the equipment, the ultraviolet lamp is directly used as an ozone generator to form an ultraviolet + ozone combined sterilization device, which can greatly reduce the equipment volume. At the same time, in order to fully utilize the disinfection capacity of ozone, the microbubble technology is introduced, which has the advantages of high specific surface area, high stability, long residence time and high gas solubility. The microbubble ejector can make the generated ozone microbubbles uniformly dispersed in the water, thereby improving the disinfection effect and promoting the degradation of organic matter. Therefore, the combined process of the present application not only reduces the equipment volume and fits the limited land area of the island, but also avoids secondary pollution. The addition of the microbubble technology further improves the disinfection effect of the ultraviolet + ozone combined sterilization process.

[0013] The present application provides a disinfection process of ultraviolet ozone combined with microbubbles for island rainwater. This combined technology is not common in the prior art and is novel. At the same time, the ultraviolet, ozone and microbubble technologies are applied in combination, which is different from traditional chlorine disinfection or ozone disinfection. This combination innovates the method of rainwater disinfection and is creative. In addition, the present application is particularly suitable for remote areas such as islands, which usually face the challenges of water resource shortage and high environmental protection requirements. The rainwater disinfection process equipment of the present application has low cost and simple operation and maintenance, can effectively guarantee the safety of domestic water for island residents, and meets the practicality requirements.

[0014] Preferably, the gas outlet and the gas inlet are arranged at the top of the quartz tube, the water inlet is arranged at the lower side wall of the quartz tube, and the water outlet is arranged at the upper side wall of the quartz tube, so that the water flow of the device is in a downward-inlet upward-outlet mode, and the gas flow is in an upward-inlet upward-outlet mode.

[0015] Preferably, the gas 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 microbubble ejector.

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

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

[0018] Preferably, rainwater in the water storage device is filtered before disinfection to remove visible suspended solids and precipitates in the rainwater, so that the incoming rainwater meets the requirements for disinfection.

[0019] More preferably, the rainwater in the water storage device is filtered in sequence with a coarse grid and a fine grid. The coarse grid has a pore size of 40-60 mm, and the fine grid has a pore size of 1-3 mm.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] Traditional disinfection techniques mainly include chlorine disinfection and ozone disinfection, but these methods have certain limitations in island environments. Specifically, when used alone, ultraviolet disinfection requires a long time and high energy consumption, and for pathogenic bacteria such as Escherichia coli, photoreactivation can also occur, which does not have sustained disinfection capability. Ozone disinfection equipment is complex, and ozone has poor stability and is easily decomposed, with a maximum half-life of only 1 h, making it difficult to persist in the reactor and easily converted to oxygen, thereby reducing the sterilization effect. If ultraviolet and ozone disinfection technologies are combined, ozone can directly damage the DNA of Escherichia coli, avoiding photoreactivation after ultraviolet disinfection. The addition of ultraviolet light can generate more active free radicals (such as hydroxyl radicals) in water to participate in the disinfection process, and Escherichia coli is subjected to ultraviolet irradiation, ozone direct oxidation, and free radical oxidation at the same time, with the three effects synergistically acting to enhance the sterilization effect. However, the entire equipment used in this technology requires a large volume, which is not suitable for the geographical environment of islands, which are small and far from the mainland.

[0022] Therefore, the present application improves the process technology by introducing microbubble technology as an auxiliary aeration means based on the ultraviolet + ozone combined disinfection technology. This is because the combination of ultraviolet and ozone generates a large amount of active oxygen species, and the presence of microbubbles not only improves the mass transfer efficiency of ozone itself, but also increases the production of active free radicals to enhance the sterilization effect.

[0023] Overall, the technical solution of the present application has the following advantages:

[0024] (1) The method has a high removal effect on pathogenic bacteria in water, and the addition of ozone avoids the incomplete disinfection of ultraviolet light.

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

[0026] (3) The method of generating ozone by ultraviolet irradiation of oxygen saves the cost and management effort of ozone generators and ozone eliminators, which makes the required equipment volume small and suitable for island environments.

[0027] (4) The required disinfection device mainly includes a quartz tube, a water storage device, an ultraviolet lamp, a water pump, a Venturi ejector and a micro-bubble ejector, and can be built and moved at any time, and is suitable for rainwater disinfection requirements in different places. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic diagram of an ozone ultraviolet combined micro-bubble disinfection device;

[0029] Figure 1 In the figure, 1 is an ultraviolet lamp, 2 is a quartz tube, 3 is an air inlet, 4 is an air outlet, 5 is a Venturi ejector, 6 is a water inlet, 7 is a water outlet, 8 is a micro-bubble ejector, 9 is a water pump, and 10 is a water storage device.

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

[0031] The specific embodiments of the present application will be further described below. It should be noted that the description of these embodiments is used to help understand the present application, but does not constitute a limitation on the present application. In addition, the technical features involved in each embodiment of the present application 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 all conventional methods unless otherwise specified, and the test materials used in the following examples are all commercially available unless otherwise specified.

[0033] The present application discloses a disinfection process of ultraviolet ozone combined with micro-bubbles for island rainwater, and the main process flow includes the following steps:

[0034] (1) Rainwater collection: connect to the local rainwater pipe network through the rainwater pipe to make the rainwater flow into the rainwater collection pool as the water flow source.

[0035] (2) Filtration: Before flowing into the disinfection device, a coarse grid (pore size 50 mm) and a fine grid (pore size 1.5 mm) are arranged in sequence along the water flow direction at the outlet of the rainwater collection pool to filter and remove leaves and other substances or visible particulate matter and suspended solids contained in the rainwater. Filtration treatment is beneficial to subsequent disinfection treatment. On the one hand, the penetration of ultraviolet light disinfection is greatly affected by water turbidity in water, and filtration can filter out suspended solids on the surface of rainwater and in water, preventing the rough surface of solid substances from causing a large amount of scattering of ultraviolet light, which prevents it from playing a stable disinfection role. On the other hand, particulate matter in rainwater can cause some wear to the device wall, and filtration treatment is beneficial to maintaining the device, prolonging the service life of the device, and reducing the cost of device maintenance. Moreover, the volume of solid waste generated after filtration is limited 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 and gas fully contact inside the device and prolong the residence time, the water flow adopts a downward inlet and upward outlet mode, and the gas flow adopts an upward inlet and upward outlet mode. Since there is no ozone in the device initially, it is necessary to generate ozone by ultraviolet light irradiation of oxygen.

[0037] ① First, open the water inlet, and the water pump will press the rainwater into the Venturi ejector, and the rainwater will be accelerated by the Venturi ejector, and then flow into the device through the water inlet.

[0038] ② After the rainwater fills the device and flows out from the upper outlet, open the air inlet to fill air into the water, and after the air flows out from the air outlet, connect the Venturi ejector through the air pipe at the air outlet. At this time, the Venturi ejector can spray water and gas at the same time, and the air reenters the device through the water inlet, making the water and gas uniformly mixed. Adjust the flow meters of the water inlet and air inlet valves so that the water flow rate is 2 L / min and the gas flow rate is 1.2 L / min.

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

[0040] ④ Previously, the water outlet cannot meet the standard and cannot be directly discharged, so it needs to be returned to the rainwater collection pool through the return pipe for reprocessing. After the pre-operation stage is completed, ozone can be stably generated in the device, and after that, the micro-bubble ejector can be turned on to start formal treatment of rainwater.

[0041] (4) Running stage: open the micro-bubble sprayer placed at the bottom of the device, the sprayer is connected to the water inlet to spray water and gas. Under the action of the micro-bubble sprayer, the bubbles in the water become fine, and the bubbles contain ozone, which slowly rises with the water flow in the device. Under the irradiation of ultraviolet light, ozone and ultraviolet light play a synergistic sterilization effect. Ultraviolet light acts on the genetic material of pathogenic bacteria, can destroy DNA to disturb 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 avoid the reproduction of pathogenic bacteria.

[0042] (5) Water outlet and detection: sample at the water outlet, detect the content of pathogenic microorganisms mainly including Escherichia coli, determine the discharge standard according to the local water quality conditions and the actual use of the reclaimed water. If it does not meet the standard, it needs to be reprocessed by entering the backflow pipe and flowing back to the rainwater collection tank. If it has met the standard, it can be normally discharged and connected to the local water supply network for various purposes. The discharge standard complies with the "Urban Sewage Treatment Plant Pollutant Discharge Standard" (GB18918-2002), and the first A standard is executed for reclaimed water. Considering the special geographical environment of the island, the water quality after discharge can also refer to the "Seawater Quality Standard" (GB3097-1997).

[0043] In order to further clearly present the present application and verify the disinfection effect of the present application, the following will be described in detail in the form of examples.

[0044] The structure of the disinfection device used in this embodiment is shown in Figure 1 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 sprayer 5, a micro-bubble sprayer 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 sprayer 5, the water reservoir 10 is connected to the water inlet 6 through the water pump 9 and the Venturi sprayer 5, and the water inlet 6 is connected to the micro-bubble sprayer 8. The quartz tube 2 is a transparent resin cylindrical pool body with a diameter of 56 mm. The water flow adopts a downward-in and upward-out mode, and the air flow adopts an upward-in and upward-out mode. The ultraviolet lamp 1 is a GPH0212T5L type Heraeus ultraviolet lamp that can emit two kinds of ultraviolet light with wavelengths of 185 nm and 254 nm. The micro-bubble sprayer 8 is placed at the inner bottom wall of the quartz tube 2 and is used to generate micro-bubbles. The Venturi sprayer 5 is an SN-III type gas-liquid mixer purchased from Ximen Electrical Technology Co., Ltd., and the micro-bubble sprayer 8 is a jet type micro-nano bubble generating device NANO-JET-01T purchased from Shanghai Xingheng Technology Co., Ltd.

[0045] The instruments and reagents required in this embodiment include:

[0046] (1) Experimental instruments: electronic balance, portable pH meter, UVC ultraviolet light intensity tester, high-pressure sterilization pot, shaking table, centrifuge, ozone generator, constant temperature box, 0.45 μm filter membrane, culture dish.

[0047] (2) Experimental reagents: tryptone, yeast extract, sodium chloride, Escherichia coli strain, nitrogen, 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 device 10 comes from the surface runoff 30 minutes after the rainfall ends on a certain island in the South China Sea, and is stored in a water bucket. After being transported back to the laboratory and standing for 40 minutes, the upper clear liquid is gently scooped out for use, and the sediment and other substances obtained by discarding the precipitate are discarded.

[0050] 2. Sample pretreatment: In order to explore the sterilization effect, it is necessary to artificially add pathogenic bacteria to simulate the high pathogenic bacteria content of rainwater. Here, Escherichia coli is selected for addition.

[0051] 2.1 Escherichia coli strain Escherichia coli DH5a, strain preservation number: ATCC15597, donated by the School of Life Sciences, Sun Yat-sen University.

[0052] 2.2, weigh 10 g of tryptone, 5 g of yeast extract and 10 g of sodium chloride with an electronic balance, add them to 1 L of pure water to prepare LB liquid medium, and divide them into 5 250 mL conical flasks, each containing 200 mL of medium. After sealing the 5 flasks with gauze strips, they are placed in a high-pressure pot and sterilized at 121°C for 20 minutes. After cooling to room temperature, 10 mg of powdered Escherichia coli strain is weighed and inoculated in a sterile table. Only one conical flask is inoculated, and the remaining four are used for subculture. The conical flasks are numbered in the order of culture time as 1, 2, 3, 4 and 5. The medium in No. 1 is placed in a shaking table and cultured at 37°C and 75% relative humidity for 24 hours. The remaining media are stored in a refrigerator.

[0053] 2.3, subculture: take out the first liquid medium from the shaker, gently shake the conical flask to make the bacteria fall off from the bottle wall and drop into the medium, take 100 mL of mixed culture solution and put it into a centrifuge tube, then put it into the centrifuge at room temperature at a speed of 4000 r / min for 10 min to precipitate the cells. Then the cells are taken out of the centrifuge tube with a rubber bulb and the old culture medium is discarded. The removed cells are resuspended in the second medium in a sterile environment, and then continue to be placed in a shaker at 37°C for 24 h. Thus, one generation of subculture is completed. Repeat the above operation 4 times to complete 4 times of subculture, and obtain the fourth generation of E. coli.

[0054] 2.4, after the fourth subculture, take 100 mL of bacterial solution in the fifth conical flask into a centrifuge tube, centrifuge at room temperature at a speed of 4000 r / min for 10 min, then discard the supernatant, and use a rubber bulb to add the concentrated E. coli to 10 L of rainwater sample, stir uniformly with a glass rod, obtain rainwater with high E. coli concentration, and store it in a water storage device.

[0055] 3, formal test:

[0056] 3.1, explore the sterilization effect of the device under only ultraviolet light irradiation: open the water pump 9, pump the water in the water storage device 10 into the venturi injector 5, the water sample is injected into the water inlet 6 at high speed by the venturi injector 5, after the water sample fills the inside of the device (quartz tube 2), open the air inlet 3 to introduce nitrogen into the water, adjust the valve to stabilize the water flow rate at 2 L / min and the gas flow rate at 1.2 L / min, turn on the ultraviolet lamp 1 at this time, keep the micro-bubble injector 8 closed, and take 5 mL of water sample from the water inlet 6 and detect the number of coliform bacteria, which can be used as the original number of coliform bacteria in the water sample. After 24 h of continuous operation of the device at room temperature, take 5 mL of water sample from the water outlet 7 and detect the number of coliform bacteria. Due to the limited water sample and fast water flow rate, in order to make the ultraviolet light in the device fully contact with the E. coli, the water outlet of the device needs to be connected back to the water storage device 10 for repeated reuse during this time period. Although the ultraviolet lamp 1 can emit ultraviolet light of two wavelengths of 185 nm and 254 nm, but since the nitrogen gas introduced is an inert gas, the inside of the device is in an anaerobic and anoxic state, so almost no ozone is generated.

[0057] 3.2, explore the sterilization effect of the device under the condition of ultraviolet light + micro-bubble: after the experiment in section 3.1 is completed, replace the new water sample in the water storage device 10, the experimental steps and operating conditions are the same as in section 3.1, but on the basis of section 3.1, the micro-bubble injector 8 at the bottom of the device is in the open state, at this time the injector can uniformly spray water flow containing fine bubbles at both ends, and finally detect the number of coliform bacteria in the water outlet after 24 h.

[0058] 3.3, Explore the sterilization effect of the device under ozone conditions only: After the experiment in section 3.2, change the water in the water reservoir 10. Turn on the water pump 9 and pump the water in the water reservoir 10 into the venturi ejector 5. The water sample is accelerated by the venturi ejector 5 and injected into the water inlet 6. After the water sample fills the inside of the device, open the air inlet 3 and connect the ozone generator to the air inlet 3. Introduce ozone into the water, and maintain the ozone production at about 36.2 mg / h. Adjust the valve to stabilize the water flow rate at 2 L / min and the air flow rate at 1.2 L / min. At this time, keep the ultraviolet lamp 1 and the micro-bubble ejector 8 closed. Then, continuously operate the device at room temperature for 24 hours. After 24 hours, take 5 mL of water sample from the water outlet 7 and detect the number of coliform bacteria. Due to the limited water sample and fast water flow rate, the device outlet water needs to be connected back to the water reservoir 10 for repeated use during this time period to ensure that the ozone in the device fully contacts with the coliform bacteria.

[0059] 3.4, Explore the sterilization effect of the device under ozone + micro-bubble conditions: After the experiment in section 3.3, change the water sample in the water reservoir 10. The experimental steps and operating conditions after this are the same as those in section 3.3, but on the basis of section 3.3, the micro-bubble ejector 8 at the bottom of the device is in the open state, and the ejector can uniformly spray water containing fine bubbles from both ends. Then, detect the number of coliform bacteria in the outlet water after 24 hours.

[0060] 3.5, Explore the sterilization effect of the device under ultraviolet + ozone conditions: After the experiment in section 3.4, change the water in the water reservoir 10. Turn on the water pump 9 and pump the water in the water reservoir 10 into the venturi ejector 5. The water sample is accelerated by the venturi ejector 5 and injected into the water inlet 6. After the water sample fills the inside of the device, open the air inlet 3 to introduce air into the water. Adjust the valve to stabilize the water flow rate at 2 L / min and the air flow rate at 1.2 L / min. At this time, turn on the ultraviolet lamp 1 and keep the micro-bubble ejector 8 closed. Then, continuously operate the device at room temperature for 24 hours. After 24 hours, take 5 mL of water sample from the water outlet 7 and detect the number of coliform bacteria. Due to the limited water sample and fast water flow rate, the device outlet water needs to be connected back to the water reservoir 10 for repeated use during this time period to ensure that the ultraviolet light in the device fully contacts with the coliform bacteria. The ultraviolet lamp 1 can emit ultraviolet light of two wavelengths, 185 nm and 254 nm, with high energy, which can decompose and recombine oxygen in the air into ozone (production amount about 38.52 mg / h).

[0061] 3.6, Explore the sterilization effect of the device under the condition of ultraviolet + ozone + microbubble: After the experiment in section 3.5 is completed, the water sample in the water storage device 10 is replaced with new water, and the subsequent experimental steps and operating conditions are the same as in section 3.5. However, on the basis of section 3.5, the microbubble sprayer 8 at the bottom of the device is in the open state, and the sprayer can uniformly spray water containing fine bubbles from both ends. Then detect the number of coliform bacteria at the water outlet 7 after 24 hours.

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

[0063] 4.1, Water sample pretreatment: Before or after each experiment, 5mL of inlet water or outlet water at the inlet is taken with a 10mL graduated cylinder, and then the water sample is diluted 1000 times with sterile high-purity water. From the 5L diluent, 100mL of diluted water sample is taken and placed in a 250mL beaker.

[0064] 4.2, Filtration: The filter membrane with a pore size of 0.45μm is pre-padded in the filtration funnel, and the water sample in the beaker is slowly poured into the filtration funnel with a glass rod. Turn on the filtration switch, and when the water is filtered, a layer of bacterial film covered by coliform bacteria will be attached to the filter membrane. The membrane is labeled as inlet group and outlet group according to the inlet and outlet water.

[0065] 4.3, Staining culture: After filtration, the filter membrane with coliform bacteria adhered is inverted and placed in an agar culture dish containing 5mL of eosin-methylene blue stain, and then placed in a 37℃ constant temperature box for continuous culture for 24h. After 24h, the number of colonies on the two filter membranes is read, one colony is one point, and it 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 outlet group filter membrane to the inlet group filter membrane, i.e. the negative logarithm of the ratio of the number of colonies before and after sterilization (unit: CFU / 100mL), represents the sterilization effect.

[0067] 5, Experimental results:

[0068] Figure 2 is the sterilization rate column chart obtained by taking the negative logarithm of the ratio of the number of coliform bacteria colonies before and after sterilization in each group. The column chart from left to right is the data of the six groups in section 3 in the order of the experiment, and the following conclusions can be drawn based on this chart:

[0069] (1) Comparing experiment 3.1 and experiment 3.2, the sterilization rate of experiment 3.1 is 2.65, and the result of experiment 3.2 is 4.35. Through t-test calculation, it is found that there is a significant difference between the data, which shows that after the addition of microbubbles, the sterilization rate is significantly improved, and the sterilization effect is: ultraviolet + microbubble > ultraviolet.

[0070] (2) Comparing experiment 3.3 and experiment 3.4, the sterilization rate result of experiment 3.3 is 2.46, and the result of experiment 3.4 is 0.80, and through t-test calculation, it is found that there is a significant difference in the data, which shows that after the micro-bubbles are added, the sterilization rate is significantly inhibited, and the sterilization effect is: ozone > ozone + micro-bubbles.

[0071] (3) Comparing experiment 3.5 and experiment 3.6, the sterilization rate result of experiment 3.5 is 4.20, and the result of experiment 3.6 is 6.43, and through t-test calculation, it is found that there is a significant difference in the data, which shows that after the micro-bubbles are added, the sterilization rate is significantly inhibited, and the sterilization effect is: ultraviolet rays + ozone + micro-bubbles > ultraviolet rays + ozone.

[0072] (4) Comparing experiment 3.1, experiment 3.3 and experiment 3.5, it is found that the sterilization effect is: ultraviolet rays + ozone > ultraviolet rays > ozone.

[0073] (5) Comparing experiment 3.2, experiment 3.4 and experiment 3.6, it is found that the sterilization effect is: ultraviolet rays + ozone + micro-bubbles > ultraviolet rays + micro-bubbles > ozone + micro-bubbles.

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

[0075] In summary, on the one hand, the present application uses micro-bubble technology, and experiments prove that micro-bubbles can play a promoting role in ultraviolet rays and ozone combined disinfection. On the other hand, the ozone used in the present application is not generated by an ozone generator as in traditional ozone disinfection technology, but is generated by ultraviolet rays irradiating air. This makes the whole technical process save the purchase and energy consumption of the ozone generator, which meets the special needs of rainwater disinfection in the geographical environment of islands which are small and far away from the mainland.

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

Claims

1. A process for the disinfection of rainwater on islands using ultraviolet ozone in synergy with microbubbles, characterized by, The method comprises the following steps: S1, setting up the disinfection device: the disinfection device comprises a quartz tube, a water storage device, a water inlet, an air inlet, an ultraviolet lamp, a water pump, a Venturi ejector, a micro-bubble ejector, a water outlet and an air outlet; The quartz tube is a transparent resin cylindrical pool body. The ultraviolet lamp is arranged on the inner top wall of the quartz tube, and the micro-bubble ejector is arranged on the inner bottom wall of the quartz tube and used for generating micro-bubbles. The air outlet and the 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 downward-inlet upward-outlet mode, and the air flow is in an upward-inlet upward-outlet mode. The air outlet is connected with the water inlet through the Venturi ejector, the water storage device is connected with the water inlet through the water pump and the Venturi ejector, and the water inlet is connected with the micro-bubble ejector. S2, collecting rainwater: connecting a local rainwater collection pool and a rainwater pipe network through a rainwater pipeline to collect rainwater into the water storage device; S3, trial operation: opening the water inlet and the water pump, pumping the water in the water storage device into the Venturi ejector, and then spraying the water sample into the water inlet at a high speed by the Venturi ejector, opening the air inlet to introduce air into the water when the quartz tube is filled with the water sample, and then opening the ultraviolet lamp to irradiate until the flow of the air outlet is stable, which indicates that ozone can be stably generated in the device; S4, formal operation: after the trial operation, the micro-bubble ejector is opened to spray the water and air into the quartz tube, and under the action of the micro-bubble ejector, the bubbles in the water become fine and contain ozone, which slowly rises with the water flow in the device and plays a synergistic sterilization effect with the ultraviolet light under the irradiation of the ultraviolet light; S5, water outlet and detection: sampling and detecting whether the indicators of the water outlet meet the standards, and connecting the water outlet to the water supply pipe network for reuse when the indicators meet the standards.

2. The process for disinfection of rainwater on islands using ultraviolet ozone in synergy with microbubbles according to claim 1, characterized by the fact that, The ultraviolet lamp can emit two kinds of ultraviolet light with wavelengths of 185 nm and 254 nm.

3. The process for disinfection of rainwater on islands using ultraviolet ozone in combination with microbubbles according to claim 1, characterized in that, The rainwater in the water storage device is filtered before disinfection to remove visible suspended matter and sediment in the rainwater, so that the inlet rainwater meets the disinfection requirements.

4. The process for disinfection of rainwater on islands using ultraviolet ozone in synergy with microbubbles according to claim 3, characterized by the fact that, The rainwater in the water storage device is filtered with a coarse grid and a fine grid in sequence.

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