Microfiltration Membrane Cleaning Methods—physical Cleaning

Physical cleaning removes contaminants from the membrane surface using mechanical methods. This method is characterized by not introducing new contaminants and having a simple cleaning process. However, it is only effective for membranes in the early stages of fouling, and the cleaning effect is not long-lasting. Physical cleaning includes various methods, such as forward flushing, reverse flushing, permeate backpressure flushing, vibration, degassing and water filling, air jetting, automatic sponge ball cleaning, hydraulic methods, gas-liquid pulse, and circulating washing.

1. Backwashing: This method removes contaminants from the membrane surface by blowing gas or liquid from the permeate side. It should be performed at a relatively low operating pressure (around 132 kPa) to avoid membrane rupture. Backwashing time is generally 20-30 minutes.

2. Static Immersion followed by Hydraulic Backwashing: For membrane modules that have experienced a decline in permeate flow and difficulty in regeneration due to long-term continuous operation, immersing them in pure water for at least 10 hours after shutdown, followed by hydraulic backwashing, is an effective method to improve flux.

3. Mechanical Scraping: For tubular components, soft foam balls or sponge balls (slightly larger in diameter than the inner diameter of the membrane tube) can be used to clean the inner pressure membrane. Inside the tube, water pressure forces the foam or sponge balls to repeatedly pass over the membrane surface, mechanically removing contaminants. This method can remove almost all soft scale, but it is not only difficult to remove hard scale but also easily damages the membrane surface. Therefore, this method is particularly suitable for cleaning membrane surfaces contaminated with organic colloids as the main component.