Silica can be removed from ...

Silica can be removed from raw water easily with standard demineralization techniques. Normally silica is present in a weak acidic form. Ion exchange will remove this as long as the anion resin is the strong base type. Silica in deionized water can easily be reduced to 20-50 ppb. Reverse osmosis will also remove silica by 90-98%. Both of these techniques are non-specific for silica, meaning they also remove all other ionic components along with the silica. Normally these methods work well for most well or surface waters where silica is below 15-20 ppm. In some cases for very large flow rates you can remove silica with lime softening techniques. In lime softening the silica is co-precipitated along with magnesium present in the water (or added if necessary). High temperature softening greatly improves silica removal. For high silica waters as seen in Mexico, Hawaii or other sandy areas where levels are 50-60 ppm or higher, the ion exchange and RO options are more troublesome because you may exceed solubility limits for one, and also you are more likely to have significant levels or non-ionic colloidal silica. This will not ion exchange and may foul an RO membrane. Typically this must be removed with ultrafiltration.