Regular chemical cleaning of RO membranes will ensure that they continue to perform and extend their useful life. The key thing with cleaning is to do it before the situation gets too bad because if you leave it too long the membrane may become irretrievably fouled. Cleaning should be undertaken whenever the normalised permeate flux reduces by 10 – 15% or, either the normalised differential pressure or permeate conductivity increase by 10-15%. In many instances it is best to adopt a programme of regular preventive cleaning.
The cleaning system is an important part of a RO Water Treatment Plant. Membranes can become contaminated after they have been used for some time, with pollutants such as colloids, bio films and biological matter. These contaminants can absorb to the membrane surface and the pipes of the membrane system and consequentially, the performance of the system will decrease. The system may even be seriously damaged. That is why a system needs cleaning periodically.
Depending on the characteristics of the water supply membrane fouling may be inorganic, organic, colloidal or microbiological in nature and often a combination. Each type of fouling requires a different cleaning strategy.
The cleaning procedure of a Reverse Osmosis system consists of the following process steps: