Determining Foulants & How to Clean Them - Part 2
Cleaning Biological, Or Organic, Fouling
The first step is to remove biological fouling, which includes bacteria and organics. In order to do this, they must be digested. This can be done with a high pH and high temperature cleaning with a minimum of 2 hours soaking. Overnight soaking is preferred here. pH should be 12-13 with as high a temperature as possible, at the manufacturer’s recommendation.
Biological fouling occurs in most cases of fouling, which is why this step should always be done first. It is also necessary to have these foulants removed before going on to the next step, as they can often interfere with inorganic salt removal.
Cleaning Inorganic Fouling
The second step is the removal or inorganic salts. This can be done with either low pH cleaner or Hydrochloric Acid. pH levels here should be 2. While this procedure will clean the membrane of most inorganic fouling, it should be noted that silica, another inorganic foulant, is more difficult to remove and will require special cleaning procedures.
Cleaning Particulate Fouling
Depending on the effective digestion of the bacteria and other organics, particulates can be freed up and then removed. Membranes fouled with suspended solids can be cleaned with disperants and sufactants. Removing particulates from a membrane requires a very aggressive procedure. Off-site cleaning is highly recommended when it comes to particulate fouling.