Pasteurization of the purified water system mainly involves heating the purified water in the storage and distribution system to 80℃, and then circulating at this temperature for 1~2h to complete the disinfection of the storage and distribution system of the purified water.The heating object of pasteurization is purified water with no access of external media and high safety.The amount of purified water has a great influence on heating time, steam consumption and system operation safety, so the amount of water in the storage tank needs to be controlled before heating.If there is too much water, heating time and steam consumption will increase, increasing operating costs.If too little, when the purified water is heated, it is easy to cause cavitation of the circulation pump and damage the circulation pump seal.The heating methods of pasteurization are tank jacket heating and heat exchanger heating. Due to the long time and poor temperature uniformity of tank heating, heat exchanger heating is mostly adopted in the newly built system.Pasteurization mainly controls the temperature of heated and purified water, which is convenient for detection, high accuracy, simple control process and stable disinfection effect.Therefore, pasteurization is the most widely used disinfection method in the storage and distribution system of purified water.Since the purified water is heated with industrial steam during the pasteurization process, its use is restricted in some workshops without industrial steam.The process requires heating and cooling, which takes a long time (about 4h).
Ozone disinfection has just started in recent years.Ozone (O3) is a colorless broad-spectrum fungicide, which has a strong inactivation effect on bacteria, bacterial spores, viruses, fungi, etc., and a relatively large solubility in water, so it has a better disinfection effect in purified water system.Ozone, as a strong oxidant, will damage the non-metal in the system to some extent. If leakage occurs, it will damage the atmosphere and human body.The half-life of ozone is relatively short and easy to decompose, so it puts forward high requirements for the detection of ozone concentration in ozone generator and system.Ozone generator (water electrolysis) and detection instrument prices are high, and the need to add the uv lamp digestion of ozone in the system, the increase in the vent ozone smog breaker, even at the use of the workshop to install automatic valve (with the ozone interlock, to prevent water containing ozone into use, cause harm to the environment and human body), so the investment system will have larger ascension.At present, the main methods of generating ozone in China are discharge method and hydropower method. Among them, the ozone generated by discharge method has a relatively low purity (brought into the air), which will have a certain impact on the system. It is mainly used in some domestic small enterprises.At present, hydropower is a relatively recognized ozone production method used for disinfection of purified water system at home and abroad. Purified water is used as raw material to produce ozone. There is no pollution from outside the system, but the equipment price is relatively high.The penetration rate is not high.
Ultraviolet radiation has a bactericidal effect.However, the use of purified water system will be affected by wavelength, pipeline water velocity, water quality change, lamp power change, water temperature and other factors, which cannot completely replace the periodic disinfection of the system.As a supplement to other disinfection methods, it can prolong the disinfection period of the system and reduce the operating cost of the system.At present, some domestic systems add filters after ultraviolet lamps to ensure that the bacteria killed will not flow into the downstream system, but this way will increase the risk of bacteria breeding and accumulation in the filter, resulting in the deterioration of water quality in the system.Therefore, it is not suitable to install filters in purified water system.
Disinfection of pure steam
Pure steam sterilization is mainly used to inactivate microorganisms in the system by high temperature (121℃).The sterilizing effect is good and the cycle is short.However, as it is sterilized under high temperature and pressure (about 1.9bar), all the equipment and instruments in the system are required to withstand temperature and pressure. At all the low points of the system, traps and temperature detection devices are needed to keep the system warm, which increases the investment of system equipment.In China's early systems, some systems will directly into the pure steam, and then in the end of the system for direct drainage (pure steam discharge port does not install steam trap), steam through the end of the system to form the so-called circulating steam.This scheme has no detection and control device at the end and low point of the system, which is unstable in process, poor in safety, and does not meet the requirements of the specification. Therefore, it is not recommended to use in the new system.
Chemical disinfection mainly refers to the disinfection and cleaning of system pipelines by adding purified water with chemical agents.In the new system, chemical agents will be added during chemical disinfection, and the cleaning process after disinfection is complex, expensive, and the residue detection is troublesome. Therefore, it will not be used as the routine disinfection method for purified water system.Chemical cleaning is used as a means of disinfection of the system only after the system has been discontinued for a long time or microbial membranes have formed.
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