Our plant use membrane fine diffuser. Recently we want to clean these diffuser because the aeration efficency decline.I want to know which methods should we take. I know air bumping can be used for membrane diffuser clean. But I do not know whether acid injection is appropraite for membrane diffuser or not. Are there anyone has some experience to it?

Best regards
Chen

The material of membrane diffuser is EPDM.

Cjcj,

Cleaning may or may not be necessary. You may wish to follow a process of elimination first to determine why the aeration efficiency has dropped.

1) Retrieve some membranes by lifting out a grid, or lower the water level in the tank if the grids are fixed to the floor.

2) You may see something while the water is draining such as leaks from joints, missing or torn membranes, support stand anchors that have failed, or lack of even air distribution between diffusers in the grid.

3) As you get closer to the diffusers themselves you may be able to see if the air is evenly distributed across the surface area of each individual diffuser, assuming air is still evenly distributed between diffusers in the grid.

4) Take a close look at the diffuser membrane from the air and water side after removing it from the holder.   Is there a slime on the surface? Are there stalacmites forming at each slit location?  Is the membrane stretched and domed?  Are the slits still tight and crisp, or stretched?

Depending on your answers to the above, you will have a better idea of whether your aeration system has aged as a result of fouling, or as a result of membrane ageing, or as a result of something else.

If you are lucky it is just calcium fouling which you can clean with acid, either (using proper protection) with a spray, or in-situ through the drop pipe with the tank in full operation.    HCL is commonly used and it is sold as a liquid in cylinders but it turns to a gas when it leaves the cylinder.    

If you have a slime you can wipe it off with a towel, or by hosing (low or high pressure, depending on the product).

If you have creep (stretching) or shrinkage of the membrane, cleaning will likely not help the situation.

I'd be glad to help you along if you post or send some photos.

-Tom  

I would also check out the blower for worn belts etc.