Silicon is usually present in water as silica, one of its derivatives. Too much silica in water can be a nuisance, and reverse osmosis may be a great way to remove silica from your water.
Reverse Osmosis can remove 90-98% of silica from your water supply by passing it through a membrane with tiny pores that allows water to pass through but traps silica behind.
This article explains what silica is, how reverse osmosis removes silica from water, RO pretreatment options for silica, and how to know if your water contains silica.
Understanding Silica
Silica, also known as Silicon dioxide (SiO2), is a compound comprising the two most abundant elements on Earth: Silicon (Si) and Oxygen (O2).
In nature, silica takes on three primary forms: granular silica, colloidal silica, and reactive silica, distinguished by the size of their particles.
- Granular Silica: This form boasts larger, non-dissolving particles, making it relatively straightforward to eliminate from water.
- Colloidal Silica: Featuring smaller particles, colloidal silica partially dissolves in water. These fine particles remain suspended, forming a colloidal solution without settling.
- Reactive Silica: Also known as ionic silica, this form consists of minuscule, fully dissolved silica particles that blend seamlessly with water.
In the context of freshwater bodies in the United States, reactive and colloidal silica are the prevalent forms.
Granular silica, conversely, typically exists in nature within materials like sand, stone, soil, and various components constituting 95% of the earth’s crust.
Most homes in the USA have silica in their water, which is not surprising, considering the large amount of silica in nature. Most concerns related to silica in your water tend to revolve around aesthetic issues.
Silica has characteristics resembling water hardness, and elevated silica levels can result in deposits forming on surfaces, appliances, and utensils within your household. This can manifest as a haze, resulting in etching and scratching of glassware, as well as the stubborn accumulation of scale on various surfaces including granite countertops, ceramic surfaces, plumbing fixtures, and more.
Notably, silica deposits are more challenging to remove compared to deposits caused by hardness minerals like calcium and magnesium, which can be dissolved with acidic substances like scale removers or vinegar.
To distinguish between water hardness-related scale and silica-related scale, a simple test involves applying vinegar to the buildup. Vinegar effectively removes calcium and magnesium deposits but has no impact on silica.
Furthermore, these deposits can hamper the efficiency of household appliances such as boilers when they accumulate inside them.
When colloidal silica is present in your drinking water, it may render the water turbid or cloudy, potentially affecting its visual appeal.
Despite the aesthetic inconveniences associated with elevated silica levels, it’s important to note that silica does not pose health risks when consumed. While some concerns exist regarding silica intake in pregnant women and its potential impact on fetal growth, conclusive research in this regard is limited.
If you have reasons to remove silica from your water, one highly effective method is through the use of reverse osmosis.
How Reverse Osmosis Removes Silica
Reverse Osmosis (RO) is a highly effective water purification method that eliminates various impurities by driving water through a semi-permeable membrane with incredibly small pores, each measuring a mere 0.0001 microns in diameter.
These minuscule pores permit the passage of water molecules while effectively blocking the majority of water contaminants. Consequently, impurities are separated, and pure water is the end result.
Notably, reverse osmosis stands out as the most efficient means of eliminating all forms of silica from water, particularly in residential and domestic settings, achieving a silica removal rate of 90-98%.
However, it’s worth mentioning that elevated silica levels in water can lead to the accumulation of scale, potentially obstructing the RO membrane. A clogged RO membrane cannot filter as efficiently and needs to be replaced more frequently.
To maintain the membrane’s integrity and reduce the replacement frequency, it is advised that you pretreat the water. This pretreatment includes the removal of hardness minerals (like calcium and magnesium) and iron from the water before it feeds into the reverse osmosis system.
Pretreatment will help increase the lifespan of your RO membrane and save you money.
RO Pretreatment Options for Silica
There are several pretreatment options that can be used to remove hardness minerals and Silica before water enters the reverse osmosis (RO) system. These methods can help extend the life of the RO membrane and improve overall system efficiency. Its important to note that some RO systems come equipped with pre-filters designed to address hardness minerals and can also help reduce silica.
Here are some common RO pretreatment options:
1. Anti-Scalant Systems:
Whole house anti-scalant systems inhibit scale buildup prior to reaching your RO. They also stop scale buildup on hot water systems, boilers and other appliances. They typically contain polyphosphates, which reduces water hardness but is ineffective against reactive and colloidal silica. One advantage of antiscalants is that your RO doesn’t have to work as hard and the filters (and pump) can last longer – saving you money.
2. Reverse Osmosis Pre-Sediment Filter:
Some RO systems come with pre-filters that are specifically designed to address hardness minerals. These pre-filters may use a combination of materials, such as polyphosphate crystals, to sequester calcium and magnesium ions and prevent them from precipitating and forming scale. While these are not necessarily designed to target silica, they will still filter out granular silica.
3. Whole House Sediment Filter:
A whole house sediment filter captures larger particles and debris in the water, including granular silica, preventing them from reaching the RO system and the membrane. While it may not remove hardness minerals on its own, it can help protect the RO membrane from sediment damage.
4. Carbon Filter:
Carbon filters do not remove silica but can trap granular silica. Carbon filters are effective in removing chlorine and organic compounds from the water, which can also benefit the RO system. Some carbon filters are designed to reduce hardness minerals, but they may not be as effective as dedicated water softeners.
Silica Levels In Tap Water
The levels of silica in tap water can vary widely depending on the source of the water and the geological characteristics of the region. Silica, in the form of dissolved silica dioxide (SiO2), is a natural component of many groundwater sources. Here’s a general guideline:
Normal Levels of Silica:
Normal or typical levels of silica in tap water usually range from 5 to 20 milligrams per liter (mg/L), which is equivalent to parts per million (ppm). However, these levels can vary significantly from one location to another.
High Levels of Silica:
High levels of silica in tap water are typically considered to be above 20 mg/L or 20 ppm. In some areas with particularly silica-rich geological formations, tap water may contain even higher concentrations of silica.
When Silica becomes a Problem:
You’ll start to notice a haze on ceramic, or glass surfaces when silica levels in water are above 40 – 50 ppm.
EPA Regulations:
The U.S. Environmental Protection Agency (EPA) does not have a specific federal drinking water standard (Maximum Contaminant Level or MCL) for silica in tap water. Therefore, there is no legally enforceable limit set by the EPA for silica in drinking water. Silica is considered a secondary contaminant, and its presence is typically regulated under guidelines for aesthetic qualities rather than health concerns.
How Do I Know If My Water Has Silica?
Silica doesn’t have a taste or smell in water and may not be seen in water, especially if it is the reactive type. When silica is above 40 – 50 parts per million, you’ll probably find glass or ceramic surfaces in your hoe start to go hazy.
There are two ways you can detect silica in your water: 1) The Acid Test and 2) Certified Laboratory Testing. Certified laboratory testing is the most accurate and dependable method.
Silica is often difficult to detect in water because the scale it forms are usually thought to be caused by hard water.
1. Acid Test
The acid test can help differentiate between silica and regular water hardness. To perform this test, apply vinegar – an acid – to the scale deposits and try to clean them off. If vinegar removes the scale, then it is caused by water hardness (mainly calcium and magnesium). If the stains do not remove, it is most likely silica.
2. Certified Laboratory Testing
A more accurate test to check for silica in your water, even in the absence of scale formation, is Certified Laboratory Testing.
These tests will not only tell if there is silica in your water but the amount as well.
We highly recommend the My Tap Score Silica Water Test. When you order this test, you receive a kit that contains everything you need to properly collect a water sample.
Send your sample to the lab, and within five days, you will receive a full report letting you know how much silica is in your water.
The report will also contain recommendations on the next step you should take concerning the results.
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