The design and operation control of the reverse osmosis system is a complex and critical process, in which the cleaning of the reverse osmosis system is an important part of ensuring the normal operation of the system and prolonging the life of the membrane. When formulating the system cleaning plan, special attention needs to be paid to minimizing the impact of the cleaning waste liquid on the environment, maximizing the contaminants removed during the cleaning process, and reducing the damage to the membrane during cleaning. When making the actual cleaning plan, it is necessary to reduce the cleaning cost as much as possible on the premise of ensuring the cleaning effect.
There are many reasons for reverse osmosis membrane pollution, including the pretreatment device equipped with a suitable pretreatment system is not suitable for the water quality and flow rate of the raw water, or the system is not equipped with the necessary process equipment and process links, and the pretreatment device is not working properly;The system selected an incorrect device or the device material was selected incorrectlyFailure of the chemical injection device in the system;Unreasonable operation and operation of equipment by operation management personnel;As well as the accumulation of insoluble sediment in the membrane system for a long time and a considerable degree of microbial pollution, the composition of the raw water changes greatly or the characteristics of the water source have changed fundamentally.
In order to prevent the chemical decomposition of the reverse osmosis membrane, it is necessary to strictly control the pH value of the water supply of reverse osmosis pretreatment, which is generally controlled between 5 and 7. At the same time, in order to avoid malfunction, the addition amount and point of NAOH and H2S04 must be strictly controlled. In addition, in order to effectively inhibit and prevent the occurrence of membrane biodegradation, it is necessary to cut off all factors that may cause biological contamination. In terms of design, the bend of the pipeline should be avoided as much as possible, the dead angle should be reduced, and accessories with cracks, dead ends and unsterilized storage tanks should not be used. In terms of operation, it is necessary to strengthen monitoring, prohibit the use of pretreatment drugs contaminated with microorganisms, and strictly control the dose.
In addition, physical factors can also lead to the decomposition and performance of reverse osmosis membranes. For example, vibrations and the ultrasound waves they generate can cause deterioration of membranes. Therefore, setting up a suitable vibration absorber and reasonable pipe layout can effectively eliminate the influence of mechanical vibration and ultrasonic waves on the membrane and prevent the physical decomposition of the membrane.
Before cleaning the reverse osmosis membrane, it is necessary to select the appropriate cleaning agent according to the nature of the fouling. Dirt will deteriorate if the cleaning agent is incorrectly selected, so the type of dirt can be clarified from the following points before cleaning: First, it is necessary to carefully analyze the recent equipment operation records that have been recorded in the past and reflect the operation of the equipment, as well as the inspection results of previous cleaningsSecondly, the reverse osmosis device is combined with the configuration of the system, and the chemical composition of the raw water is analyzedThirdly, the fouling on the filter membrane was analyzed by SDI assayFourth, check the inner surface of the water supply pipeline, open the end of the pressure vessel, and check the dirt appearance of the water supply end of the membrane element.
In summary, the cleaning of the reverse osmosis system is an important part of ensuring the normal operation of the system and prolonging the life of the membrane. When formulating the system cleaning plan, special attention needs to be paid to minimizing the impact of the cleaning waste liquid on the environment, maximizing the contaminants removed during the cleaning process, and reducing the damage to the membrane during cleaning. At the same time, it is necessary to strictly control the pH value of the water supply and the amount of chemicals added to the reverse osmosis pretreatment, strengthen monitoring and management, and effectively inhibit and prevent the occurrence of membrane biodegradation. Before cleaning, it is necessary to select the appropriate cleaning agent according to the nature of the dirt, and carefully analyze the operation of the equipment and the historical cleaning results to determine the type of dirt.