Views: 1319 Author: Kevin Chen Publish Time: 2020-07-01 Origin: Site
As is known to all, after your system has been in operation for a period of time, sometimes the processing capacity drops significantly (cannot reach the design flux). The reason for this situation happens is mainly due to the working environment of the system, the selection and the design, installation, operation management and performance of MBR, UF or RO membrane itself.
For the UF system, the anti-pollution and hydrophilicity of the membrane itself have a great influence on the flux. After the flux drops, the processing capacity of MBR or UF decreases. If you want extend the lifespan of your membrane, a stronger anti-pollution and a better cleaning-recovery reinforced PVDF can be selected. Combined with continuous air cleaning, the cleaning effect is very good.
For the MBR system, a permanently hydrophilic, non wire breakage reinforced PVDF MBR membrane should be selected to ensure the water production and water quality.
If the inlet water temperature is lower than the design temperature (commonly seen in seasonal changes), the membrane effluent performance will be decreased. The changes of different types of the pollutant, concentration and water viscosity in the source water will also cause the membrane permeability to be lower than expected. To solve these problems, it is necessary to consider the fluctuation range of the minimum water temperature and water quality throughout the year, and leave a certain safety margin when selecting the membrane area at the beginning of the design.
Due to insufficient design experience and excessive cost considerations, the safety margin of the selected membrane area is insufficient, and the flux of the membrane is estimated to be too high. Whether it is MBR, UF or RO membrane, it is necessary to ensure sufficient membrane area.
Insufficient pressure and uneven fluid distribution, resulting in water flow or gas flow bias, will also affect the membrane performance, especially for UF systems and RO systems. For RO system, if the membrane surface flow rate is too low, it will cause the deposition of pollutants, causing blockage. The solution is to improve the design of pumps, water and gas pipes, so that multiple groups of membranes can all share the processing load, avoiding some membranes overloading, and some membranes are not functioning. If the design of the cleaning and maintenance function is insufficient, especially no self-rinsing function with outlet water, it can be solved by improving the design of air washing, water washing and medicinal washing, and setting the appropriate washing frequency and water volume.
If there is no pre-filtration protection facility before entering the membrane, it will cause the membrane system blocked. The solution is: for MBR system, add 13 mm ultra-fine bar screen; for UF system, add 100μm grade coarse filter; for RO system, add 5μm grade precision filter.
During the manufacture and installation of the system, failure to clean up the debris in time will result in excessive impurities remaining, which will affect the water production performance. In particular, welding slag, sharp or filament object, etc., will cause damage to the fibers or the films. For MBR membranes, the impurities in the tank must be cleaned before entering the water; for UF and RO systems, the front pipeline system should be rinsed first, the pre-filter should be operated, and then comes the inlet water.
Add chemicals correctly, especially scale inhibitors is very important for RO systems. In addition, according to the working conditions, it should be rinsed in time or taken to restore the membrane performance.
Insufficient design experience leads to an excessively high recovery rate, or an artificial operation exceeding the design recovery rate will also result in a decrease in membrane processing capacity. For the UF system, cross-flow filtration can be used instead of dead-end filtration; for RO membranes, concentrated water discharge should be increased to reduce the recovery rate, reduce the number of membranes connected in one housing, or increase the return flow.