Author: Site Editor Publish Time: 2023-02-03 Origin: Site
If the system uses scale inhibitor, when the water temperature is between 20 and 38°C, about 4 hours; below 20°C, about 8 hours; if the system does not use scale inhibitor, about 1 day.
The membrane system is designed for continuous operation, but in practice, there is always a certain frequency of start-up and shutdown.
When the membrane system is shut down, it must be flushed with its produced water or pre-treated water for low pressure, replacing the high concentration of concentrated water containing scale inhibitor from the membrane element.
Measures should also be taken to prevent the introduction of air from leaking water into the system, as loss of water from the element may result in irreversible loss of produced water flux.
If the shutdown is less than 24 hours, no measures to prevent the growth of microorganisms are required. However, if the downtime exceeds the above, a protective fluid should be used to preserve the system or to flush the membrane system at regular intervals.
The brine seal on the membrane element is required to be installed at the inlet end of the element, while the opening faces the inlet direction, when feeding the pressure vessel, the opening (lip) will be further opened to completely seal the inlet water from the membrane element and the pressure vessel wall between the side flow.
Silica exists in water in two forms, active silica (monomeric silica) and colloidal silica (polysilicon): colloidal silica is not characterised by ions but is relatively large in scale. process (CDI), are very limited in their effectiveness in removing colloidal silica.
The size of active silica is much smaller than colloidal silica, so most physical filtration techniques such as coagulation clarification, filtration and air floatation are unable to remove active silica, and the processes that are effective are reverse osmosis, ion exchange and continuous electrodeionisation.
The pH range for reverse osmosis membrane products is generally 2 to 11. The effect of pH on the membrane performance itself is very small, which is one of the distinctive features that distinguish it from other membrane products, but the characteristics of many ions in the water itself are greatly affected by pH, for example, when weak acids such as citric acid are mainly in the non-ionic state at low pH, while at high pH they appear to be dissociated and in the ionic state. As the same ion, high degree of charge, membrane removal rate is high, low degree of charge or no charge, the membrane removal rate is low, so pH has a huge impact on the removal rate of certain impurities.
