Precision filter and bag filter

Water treatment industry, and often meet with the bag filter, then what is the difference between them? These two filter which is high precision, precision filter can replace bag filter?

Precision filter if in front of the reverse osmosis, often called security filters, security filters, that is, into the membrane water security, general precision is chosen as 5 micron, if used in the back of the reverse osmosis or the back of the ultrafiltration membrane, precision filter, also known as microporous membrane filter, then usually in 1 micron filter precision, after mainly removed by intercepting the bacteria in the water impurities. Precision filter filter cable around the filter, folded filter and melt-blown filter, because of the price cheap, melt-blown cartridge so melt-blown filter used in water treatment the most ?