Application of Ultraviolet Lamp in Water Treatment

Author: Hongjie Water

The ultraviolet sterilization lamp is mainly used in water treatment for its bactericidal efficacy and toxicity. From the method of using ultraviolet sterilization lamps, there are methods that directly immerse the lamp in water, called immersion; The ultraviolet lamp is placed in a sleeve for use, which is called an overcurrent type. For example, the working principle of an overcurrent device is as follows: a certain flow rate of water generated by the water pump pressure flows through the periphery of a quartz sleeve that can transmit ultraviolet light. The 254nm ultraviolet light generated by the ultraviolet lamp sterilizes and disinfects the water. Its characteristic is that the water flow rate is fast, and the time it flows through the quartz sleeve generally does not exceed 1 second. Therefore, the ultraviolet intensity of the sterilization lamp is required to be high, and the surface intensity is generally required to exceed 30000uw/cm2, To generate such high ultraviolet intensity, it is necessary to choose a high intensity and high-power ultraviolet sterilization lamp. If you still want to improve the disinfection effect by extending the time, you usually choose longer lamps, make longer equipment, or treat the stainless steel outer wall into a vortex rotating structure to extend the time of water flow. Overflow devices also have requirements for the environment and treatment objects, such as the temperature and transparency of water, which have a significant impact on the disinfection effect. The surface temperature of the UV sterilization lamp during operation is 40C, and high or low temperatures can affect the UV output effect; The lower the transparency of water, the easier it is for ultraviolet rays to be absorbed, and the lower the utilization rate. Compared with the overcurrent type, the submerged type has a simple structure. The ultraviolet sterilization lamp should be placed directly in water, and this method should be noted that the lamp tube may rupture due to unexpected circumstances; After long-term treatment, the surface of the lamp tube will be covered by pollutants such as algae in the water, which will seriously affect the transmission of ultraviolet radiation.

It is necessary to use high-strength ultraviolet lamps in water treatment, especially in wastewater treatment. Because if a large number of ultraviolet lamps are used, there will be more ballasts, more complex circuits, and more complex control parts. Often, if a lamp breaks, it will need to be shut down for replacement and maintenance. The more lamps and ballasts are used, the greater the probability of one being broken. In traditional ultraviolet lamps, the power can generally only reach several tens of watts, such as traditional specifications of 40 watts and 30 watts. If high flow water treatment is used, the total power needs to be several thousand watts, and the number of ultraviolet lamps needs to be tens to hundreds. The equipment is huge, and the control circuit is also very complex. When using high-power ultraviolet lamps, such as 300 watts, the number of lamps and ballasts will be greatly reduced, which can simplify the equipment. Improve equipment safety and reliability to reduce equipment failure rates. High intensity ultraviolet lamps can be used in water treatment, with or without ozone, respectively. The so-called ozone lamp refers to a lamp that can transmit 185nm spectral lines (characteristic spectral lines of mercury), which can ionize air to produce ozone in the air. According to experimental research abroad, 185nm ultraviolet light can generate photochemical reactions in water, that is, ionizing H20 to produce - OH (hydroxyl) - OH with strong oxidizing properties, which can mineralize and decompose organic matter in water, reducing TOC. However, ordinary low-pressure mercury lamps have low power, and 185nm ultraviolet light only accounts for 20% of the electrical energy consumed by the lamp tube. Its effect is not significant, and only high-power ultraviolet lamps can show certain effects.

In addition to using ultraviolet lamps for disinfection and sterilization in water treatment, other principles of action of ultraviolet lamps can also be used. This is a photocatalytic reaction. This principle has now been successfully applied to air purification. The photocatalytic air purifiers we see on the market use this principle. On the market, we can see two wavelengths of ultraviolet lamps, one is 254nm, and the other is 365nm. Both lamps have been successfully used in photocatalytic reactions. The 254nm ultraviolet lamp, also known as the commonly used sterilization lamp, is a spectral line emitted by mercury atoms. A lamp with a 365nm spectral line usually uses black UV transparent glass; Another method is to use quartz glass coated with 365nm purple light powder, which has a higher transmittance but correspondingly higher cost. When used in water treatment, a 254nm ultraviolet lamp is usually used for photocatalytic reaction, which actually involves a dual effect of 254nm, namely direct sterilization and photocatalytic generation of hydroxyl mineralization degradation and sterilization.