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Selecting the right antiscalant and cleaning chemicals will optimize operating efficiency and help to prevent plant failure.
Membrane scaling is the accumulation of mineral deposits, such as calcium carbonate, calcium sulfate, or silica, on the surface of a membrane used in reverse osmosis (RO) systems. These deposits form due to the concentration of minerals during reverse osmosis.
Over time, buildup of scale can reduce the efficiency of the membrane by obstructing the flow of water through it, thereby decreasing the system’s performance and potentially leading to the failure of the RO plant. To prevent membrane scaling, it’s crucial to select the appropriate antiscalant, and tailor the dose rate according to the specific ionic composition of the feed water.
Before cleaning, we always recommend a membrane autopsy to ensure deposits are correctly identified.
Learn about some of the most common types of scales that we have identified on RO membranes during autopsy procedures and the appropriate chemicals to use.
Calcium Carbonate is the most common scale found in membranes. Appears as an off white powder. Easily cleaned with a strong acid product.
Silica is a complex foulant. It can be present on lead membrane elements in a colloidal form, or as a glass-like scale on tail-end elements. Both forms can be difficult to remove. Recommended cleaning procedures depend on whether the deposit is colloidal or precipitated scale in nature.
Calcium sulphate is a crystalline structure with very sharp blade-like features, which cut the membrane surface. Common occurrence in areas where there is a natural sulphate content in the underlying geology. This makes it very difficult to clean – ask us for advice on cleaning protocol design.
Calcium phosphate appears in many forms. Commonly found in RO membrane systems fed with waste water or agricultural leachate, due to the high phosphate loading.
Magnesium hydroxide precipitates at high pH, typically above 9.5. It is usually found in the second pass where sodium hydroxide is dosed to aid boron rejection.
Barium sulphate appears as white crystals, which can take on-blade like formations. Very difficult to clean effectively – ask us for advice on cleaning protocol design.
Strontium sulphate appears as crystals or as needles, which can damage the membrane surface. Very difficult to remove – ask us for advice on cleaning protocol design
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We specialize in producing specialty chemicals and offering membrane testing services that allow reverse osmosis (RO) plants to operate efficiently in areas where feed waters are challenging.
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