UF membranes have multiple functions such as cleaning and sterilization, removal of impurities, and water purification. Additionally, these membranes remove sediment and suspended solids in water, as well as various large organic molecules and microbial cells. This highlights the importance of UF membranes. However, various problems may arise during the filtration process. So, what are the precautions to take while using UF membranes in the filtration system?
The filtration system must be regularly sterilized
While UF membranes may filter bacteria, they cannot kill them. Even an ideal membrane cannot guarantee that the clean area will be bacteria-free for an extended period. The presence of bacteria can lead to massive reproduction, which can directly affect the water quality output. For example, some mineral water products have half-transparent, thread-like, white mold lumps, mainly caused by mold contamination of the system. When surface water is used as the supply source, the sterilization cycle is shorter.
The number of components used in the filtration system is determined based on the total design water permeability
The hourly water production capacity specified for each component refers to the pure water permeation rate. This rate is attained by using pure water as the testing medium, where no solute causes clogging issues for the UF membrane. The testing temperature is 25℃, and the testing pressure is 0.1MPa. As the filtration system runs, the water permeation rate gradually decreases, although it typically recovers to a relatively stable value after cleaning. The stable value is generally only about 60% of the initial water permeation rate. In addition, the water permeation capacity of UF membranes is affected by temperature, pressure, material concentration, and feed water turbidity. Therefore, during design, these factors must be considered.
Before use, each UF component is filled with protective liquid
The protective liquid must be thoroughly flushed out of the component, using low pressure (0.1MPa) water for 1 hour, followed by high pressure (0.2MPa) water for 1 hour. During low or high-pressure flushing, the water production discharge valve of the system should be fully open. When using the product water, ensure that no sterilizing agents are present.
Each UF membrane component must be handled with care and protection because they are precision equipment
During use and installation, they must be handled with care and not dropped. If the membrane component is not in use, flush it clean with water, and then disinfect and sterilize using a 0.5% formaldehyde solution, then seal it. In winter, the components additionally require antifreeze treatment; otherwise, they may become unusable.