Silicon is among the more abundant elements in the Earth’s crust, and most rocks are comprised of silicate minerals with SiO₂ as a fundamental building block.
So it comes as no surprise that it is almost always present in source water, process water, and wastewater streams. For industrial units, efficient management of silica levels in process water is important to ensure optimal functioning and performance life of equipment.
But before we get into the how’s and the why’s of silica removal from water, let’s first understand the silica in your water. For practical water treatment, silica in water is often discussed as two main fractions: reactive (dissolved) silica and colloidal/polymeric (non‑reactive) silica:
- Reactive Silica – Reactive silica is mostly present as monomeric silicic acid in equilibrium with silicate/bisilicate ions and behaves overall as a weak acid; in this ionic form it can be removed on strong base anion exchange resins
- Colloidal Silica – Colloidal silica behaves as fine suspended solids and is not effectively removed by ion‑exchange processes, which are designed for ionic species; it is better addressed with membrane or coagulation/clarification steps
Why is Silica removal necessary?
Removal of Silica from the process water is done as a means of safeguarding the industrial equipment from getting damaged. Silica content can accumulate on surfaces as hard mineral deposits known as scale. These deposits, also commonly known as scaling, tend to reduce the overall efficiency of the industrial equipment and cause serious damage.
Silica can also cause membrane fouling & scaling in membrane systems. Membrane fouling occurs when silica particles lodge in the membrane’s pores, obstructing the normal flow of liquids through the membrane.
Common methods of Silica Removal from Water:
- Ion Exchange Resin – This ion-exchange method can be used to remove virtually all reactive silica, but not colloidal silica. Regeneration of the resins is required in intervals.
- Membrane Filtration(RO & UF) – Membrane treatment can remove virtually all colloidal silica. Both reverse osmosis and ultrafiltration are effective in this respect. Reverse osmosis typically provides high rejection of dissolved (reactive) silica, often in the range of 95% or higher under well‑designed conditions, in addition to removing colloidal silica.
- Lime-Soda softening – Lime–soda softening is a widely used precipitation process for hardness control; when operated at elevated pH with appropriate magnesium or coagulant addition, it can also significantly reduce both dissolved and colloidal silica through co‑precipitation and adsorption onto flocs.
These already existing solutions have their own merits in various aspects of tackling this problem. But each of them pose a new challenge to companies. Anion exchange resin is unable to remove large amounts of colloidal silica from water, membrane filtration is hindered due to scaling problems, and lime-soda softening forms huge amount of sludge which causes huge sludge disposal headaches for companies.
The world has been crying out for an all-in-one silica removal solution which tackles the silica issue without having the aforementioned challenges.
We at Pure Water provide the world’s best water treatment solutions. Get in touch with us at info@purewaterent.net, to know more about how we can assist you with your silica problems and help your facilities reach their maximum potential.
