What is inorganic scale in relation to Reverse Osmosis Membranes
An increased amount in the concentration of dissolved inorganic salts at the membranes surface usually results in inorganic scale formation. Precipitation is liable to occur if the ionic product of a dissolved salt exceeds its solubility. This could then go on to fouling of the membrane surface. An average finding shows that precipitated salts are calcium carbonate, barium sulphate and calcium sulphate. Traditionally, to control deposition in brackish water and seawater operations, mineral acids and polyphosphate acids were used. This method proved that neither acid’s were entirely satisfactory in all possible situations.
Serious supply problems and safety hazards to plant operators are able to occur when mineral acids are used. Another problem that the use of acid presents is that acid needs to be accurately dosed to minimise corrosion and other large problems such as scale formation (sulphuric acid = sulphuric scale formation). SHMP is not thought to be the most affective route to fighting sulphate deposition. As it is a phosphate based addictive, it can become a source of nutrients for bacteria. This can lead to the membrane becoming fouled. As this product is actually distributed as a solid, it can be difficult to dissolve to the correct dosage.