Reverse osmosis (RO) membranes have been applied for the separation of water from its dissolved constituents. The presence of silica and other dissolved solids in water and industrial water systems is prevalent. Consequently, silica fouling causes adverse effects on RO process, which includes flux decline, shorter membrane lifetime and also an increase in energy consumption. Dynamics tests using Osmonics Sepa CF flat sheet RO unit have been conducted to investigate the effect of silica fouling of reverse osmosis membranes in the presence of minute amounts of various inorganic cations such as iron, manganese, nickel and barium that are present in industrial and mineral processing wastewaters. Experimental results showed that the presence of iron greatly affected the scale structure on membrane surface compared to manganese, nickel and barium.