Reverse Osmosis Membrane Cleaners - The use of high quality membrane cleaners is an important part of any Reverse Osmosis plant maintenance programme.
There are advantages in cleaning membranes at an early stage of fouling, as irreversible damage can occur when cleaning excessively fouled membranes. Although cleaning techniques acceptable to the membrane manufacturer or OEM should not harm the membrane, the operator should always refer to the manufacturer's instructions before starting any cleaning programme.
Even though the membrane foulant is often unknown, effective cleaning usually requires some knowledge of the type of foulant and the cleaning options available.
Sometimes the causes of fouling can be identified from plant operation. For example, a pressure build up at the membrane inlet may indicate suspended solids, such as iron or colloidal particles in the feed water; in this case there may be an apparent increase in the Silt Density Index (SDI). An increase in pressure at the brine discharge usually indicates some mineral scaling, and the brine analysis can be examined for clues as to its possible nature.
The rate of membrane fouling is often dependant on the efficiency of the pretreatment system and the performance of the antiscalant programme being used.
Cleaning of reverse osmosis membranes should take place when one or more of the main (normalised) operating parameters, flux, conductivity or pressure differential, changes by 10 -15%.
It is important to clean the membrane at an early stage of fouling. If performance deteriorates by 30-40% (or more), it may be impossible to recover plant performance by routine cleaning procedures. In a badly fouled membrane the flow pattern of the cleaning solution fails to penetrate the fouling medium.