Removing the cover layer from the membrane surface
During backpulsing, cover layers on the membrane surface are flushed back into the flow of the filtration medium from the permeate side, thus cleaning the membrane pores. Since ceramic membranes consist of a porous body that is pressure-resistant on both sides and on which multiple ceramic layers are firmly sintered, atech membranes can be subjected to high pressure both from the feed side during filtration and from the permeate side during the backflush pulse. With polymer membranes, this is usually not possible and cleaning with chemicals is therefore necessary.
Recovery of the filtration properties
It is necessary to clean filtration membranes on which a filter cake or deposits have formed to restore their filtration properties, i.e. the flow rate, also called flux (measured in litres/(square metre x hour)) and the exact retention, which can be changed by the deposits. Filter cake increases the resistance during the flow through the membrane layers and thus has a very negative influence on the filtration properties. Deposited top layers reduce the permeability of the membranes and change their separation characteristics, sometimes to such an extent that a microfiltration membrane acts like an ultrafiltration membrane and retains substances that should actually remain in the permeate. In the end, this phenomenon also known as fouling can reduce the operating time of the entire system due to the need for frequent cleaning.
Gentle process without damage to the membrane surface
Backpulsing removes the existing deposits gently and in a purely physical way, maintains the filtration properties of the membranes and does not damage their surfaces. atech membranes can be backpulsed. If a cover layer has formed on the membrane surface it can be removed using a backflushing device consisting of a piston or a small pressurised vessel. The backflush pulse forces the liquid, i.e. the filtrate, through the membrane onto the side with the medium to be filtered and removes the deposits from the surface. Cross-flow filtration continues during the backpulsing process which is carried out at a higher pressure than the filtration pressure. The cover layer is merely lifted and removed.
This way, the filtration properties of the membrane are restored.