Before going any further, it is important to clarify that silicon, with its symbol Si, is not present in its pure form in its natural state. Most often, it is found in its mineral forms: silica & silicates. In the water treatment environment, it is generally silica that is problematic.
Silica is composed of the two most common elements on earth, silicon and oxygen. On earth, SiO2 (silica) is found in many forms. The three most common forms of silica are quartz, tridymite and cristobalite.
Silica and Water
Because of its abundance in the environment, silicon is found in virtually all waters on earth. In its most common form in water, silica (SiO2), concentrations generally vary greatly, from 20 mg/L to over 1000 mg/L, depending on the source of the water. Brackish waters generally have high concentrations of silicon or its derivatives.
When silicon derivatives are added to water, it is usually as a conditioner, detergent or corrosion inhibitor. Whether added for a specific use or naturally occurring in water, silica can cause problems for some industrial equipment.
Indeed, when in the presence of water at high temperature or under high pressure, silica can cause deposits. This is why in applications such as industrial kettle water, the presence of silica can be risky for the safety and efficiency of the equipment. To avoid the formation of silica deposits, which is characterized by a glassy appearance, silica levels must be below 0.005mg/L.