The Driller
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • CLASSIFIEDS
  • EQUIPMENT
  • SAFETY
  • VIDEOS
  • EDUCATION
  • SOURCEBOOK
  • EVENTS
  • SUBMIT
  • ABOUT
  • SIGN UP
cart
facebook twitter linkedin youtube
  • NEWS
  • Water
  • Geothermal
  • Construction
  • Environmental
  • Mining
  • All Industry News
  • EQUIPMENT
  • Rigs & Heavy Equipment
  • Consumables
  • Pumps
  • Featured Products
  • VIDEOS
  • Newscast
  • Drill Talks
  • Ask Brock
  • Emerging Drillers
  • EDUCATION
  • Drilling Business Insights
  • Reference Desk
  • Sponsored Insights
  • EVENTS
  • Conferences & Demo Days
  • Newscast LIVE
  • SUBMIT
  • Drillers @Work
  • ABOUT
  • Contact
  • Advertise
The Driller
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
The Driller
  • NEWS
    • Water
    • Geothermal
    • Construction
    • Environmental
    • Mining
    • All Industry News
  • CLASSIFIEDS
  • EQUIPMENT
    • Rigs & Heavy Equipment
    • Consumables
    • Pumps
    • Featured Products
  • SAFETY
  • VIDEOS
    • Newscast
    • Drill Talks
    • Ask Brock
    • Emerging Drillers
  • EDUCATION
    • Drilling Business Insights
    • Reference Desk
    • Sponsored Insights
  • SOURCEBOOK
  • EVENTS
    • Conferences & Demo Days
    • Newscast LIVE
  • SUBMIT
    • Drillers @Work
  • ABOUT
    • Contact
    • Advertise
  • SIGN UP
MarketsWater Wells

Silica Removal Processes

April 5, 2005
A look at the available water treatment methods.

A magnified look at silica.
In a water purification system, the treatment objective may include reducing silica concentration to permit increased cycles of concentration without scale. Although conventional coagulation and filtration is effective to remove most (if not all) colloidal silica, this usually is a small fraction of the total silica in natural water supplies. Conventional precipitation technologies are reasonably cost-efficient to achieve partial removal of silica. Drawbacks to precipitation are numerous. Precipitation of silica is a messy, time-consuming process and can be difficult to accomplish without upsets.

Where complete removal of silica is required, various combinations of reverse osmosis (RO) and/or ion exchange processes are used. The current state-of-the-art technology includes both multiple membrane and multiple ion exchange steps, and can produce reactive silica concentrations in the neighborhood of 0.1 ppb.

Chemical Precipitation

Silica almost never precipitates as SiO2. Silica scale almost always contains a divalent (or trivalent) cation. Although calcium silicate is quite insoluble, this compound does not form rapidly except at very high temperatures. Although aluminum salts can be used to precipitate silica, the consequences of leaving a substantial aluminum residual in the product water makes this process undesirable. The conventional method of precipitating silica has always been co-precipitation with magnesium.

Since silica becomes part of the magnesium precipitant, some means of adding already precipitated magnesium (magnesium oxide) or of precipitating magnesium in situ is used. In situ precipitation works much better than already precipitated magnesium, probably due to surface area of the precipitant and proximity to a silica molecule.

The addition of soluble magnesium salts (such as MgCl2) often is desirable due to an increase of total dissolved solids. Even though it is less effective, MgO is more often used. The advantage of MgO is that it adds little or no dissolved solid to the water.

Temperature and pH also have important effects on silica removal by precipitation. The precipitation mechanism occurs faster and more completely at high temperatures. The pH must be high enough to cause magnesium to precipitate but not so high as to make the precipitant resoluble.

Reverse Osmosis Systems

RO systems also can be used to reduce silica concentration. Although cellulose acetate and early thin-film composite materials only provided moderate silica rejection, newer materials reject silica quite well. The mechanism of removal probably is by hyper-filtration, but also is related to degree of ionization since silica is more completely removed at a high pH. Since silica is concentrated by the membrane in the reject stream, silica solubility can be an important consideration. RO systems currently are unable to achieve as complete removal of reactive silica as ion exchange, but are far better at removing various forms of non-reactive silica.

E Cells

E Cells are electrodialysis stacks where the water-flow channels are filled with ion exchange resin. The mechanism of removal probably is that the resin first exchanges for various ions (including silica), slowing them down, and then allowing them to be pulled through the membranes. Since silica is weakly ionized, a higher current density is needed for a high percentage of silica removal. The E Cell process currently is more expensive than RO for bulk removal of ions and suffers the same inability as ion exchange to remove non-reactive silica. However, it is competitive with RO and ion exchange technology for polishing and offers a perceived advantage over ion exchange, in that its use does not involve handling of strong mineral acids and bases. Still, the lowest silica residuals currently achievable are produced by ion exchange resins.

Ion Exchange Technology

All strongly basic ion exchange resins have the ability to split salts. This means that they can remove weakly ionized species such as carbon dioxide and silica. Although hydroxides form strong base anion resins, preference for silica is much lower than for sulfates and chlorides; it is significantly greater than for hydroxide. There is pretty good evidence that only when in the hydroxide form, does strong base anion resin exhibit any preference for silica. When in the hydroxide form, preference for silica and for alkalinity are similar (at least we know that silica break generally occurs at about the same percentage exhaustion as alkalinity break). In the chloride form, or any other salt form, strong base anion resin has zero preference for silica (probably because silica is nonionized at typical raw water pH), although it still can be used for alkalinity removal.

This suggests that silica is not exchanged in the same way as other anions.

Desilicizers

An anion desilicizer is a “poor man's” demineralizer, consisting of a strong cation exchanger in the sodium form (a water softener), followed by a strong base anion exchanger in the hydroxide form. Thank goodness there are not too many of these critters around anymore. They have most of the disadvantages of a demineralizer and few of the advantages. However, they do remove silica along with the other anions.

Over the years, more than one engineer has wondered if it might be possible to operate a desilicizer at a real small caustic dose (or perhaps brine plus caustic) and use the anion resin as a dealkalizer while still removing some silica. This would avoid the excess causticity created by the complete anion exchange for hydroxides. This was tried and the results were quite interesting. As long as the resin had enough hydroxide exchange sites to remove all the anions, silica was well removed. As soon as the hydroxide sites were depleted, the resin dumped the silica. By the time the hydroxide concentration was substantially reduced in the product water, all the silica had dumped. There was no net removal.
ND

KEYWORDS: water treatment

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

Recommended Content

JOIN TODAY
to unlock your recommendations.

Already have an account? Sign In

  • geotechnical drilling rig

    6 Onsite Phrases Environmental Drillers Hate

    Here are six phrases that highlight common frustrations...
    The Underground Network
    By: Jeff Garby
  • Wayne Nash

    Pipe Stuck? Common Causes and Solutions for Drillers

    If you have drilled for any length of time, sooner or...
    World According to Wayne
    By: Wayne Nash
  • submersible pumps, water well pumps

    Selecting and Sizing Submersible Pump Cable

    This article helps pump installers and servicers decide...
    Opinions
    By: Bob Pelikan
You must login or register in order to post a comment.

Silica and Calcium removal

Phil Parker
August 15, 2012
Our raw water contains on average 125 ppm of silica and 1200 ppm of calcium. We use a evaporator to circulate the water at 213 degrees while extracting the distillate and concentration the brine. Unfortunately the calcium and silica levels are plating out and contaminating the system. What could we add to bind these two elements together?

Executive Director, ERI

Md. abdur Rahim
December 28, 2013
This article is good but more emphasis is needed to allow the readers to know about the Soluble Silica Removal by Dolomite Treatment or Lime MgO and Soda Ash Treatment anf coagulation, fucculation, follwed by Sand/ Anthracite and Ultra Filtration.

Report Abusive Comment

Subscribe For Free!
  • eNewsletters
  • Online Registration
  • Subscription Customer Service
  • Manage My Preferences

The Driller Newscast: Coiled Tubing Drilling and the Future of Geothermal

The Driller Newscast: Coiled Tubing Drilling and the Future of Geothermal

The Driller Newscast: New York Geo Talks 2025 Conference with Hands-on Driller Education

The Driller Newscast: New York Geo Talks 2025 Conference with Hands-on Driller Education

The Driller Newscast, Episode 147: Global Geothermal Collaboration at NY-GEO 2025

The Driller Newscast, Episode 147: Global Geothermal Collaboration at NY-GEO 2025

The Driller Newscast: 21st Century Drillers | Part 1 DEMAND

The Driller Newscast: 21st Century Drillers | Part 1 DEMAND

More Videos

Sponsored Content

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the The Driller audience. All Sponsored Content is supplied by the advertising company and any opinions expressed in this article are those of the author and not necessarily reflect the views of The Driller or its parent company, BNP Media. Interested in participating in our Sponsored Content section? Contact your local rep!

close
  • demo of a DM450 drilling rig during a customer factory visit
    Sponsored byGeoprobe

    Built for You: Smarter Drill Rigs, Stronger Support, Bigger Opportunities

Popular Stories

MainPhotoTwoBrothers.jpg

Two Brothers' Journey Through the Drilling Industry

demo of a DM450 drilling rig during a customer factory visit

Built for You: Smarter Drill Rigs, Stronger Support, Bigger Opportunities

AI and Drought Concerns

AI’s Growing Thirst for Water and Power

The Driller Classifieds

COMPRESSORS

EAST WEST MACHINERY & DRILLING IS BUYING AND SELLING AIR COMPRESSORS, AIR BOOSTERS, AIR ENDS & PARTS
Company: East West Machinery

DRILL RIGS

LOOKING FOR LATE MODEL TOPHEADS & DRILLTECH D25'S
Company: Spikes’s Rig Sales

DRILL RIG PARTS

MEETING DRILLERS NEEDS AROUND THE WORLD
Company: East West Machinery

ELEVATORS

SEMCO INC. PIPE ELEVATORS
Company: Semco Inc.

GROUTERS

GROUTING EQUIPMENT - GROUT PUMPS & GROUT HOSE REELS
Company: Geo-Loop Inc.

PUMP HOISTS

SEMCO INC. - BASIC PUMP HOISTS
Company: Semco Inc.

WELL PACKERS

LANSAS PRODUCTS - INFLATABLE WELL PACKERS
Company: Vanderlans Lansas Products

WELL SCREENS

WELL SCREENS & SLOTTED PIPE
Company: Alloy Screen Works

Products

Water Quality Engineering: Physical / Chemical Treatment Processes

Water Quality Engineering: Physical / Chemical Treatment Processes

By carefully explaining both the underlying theory and the underlying mathematics, this text enables readers to fully grasp the fundamentals of physical and chemical treatment processes for water and wastewater.

See More Products

Subscribe to The Driller Newscast

Related Articles

  • Arsenic Removal Processes

    See More
  • Silica Removal

    See More
  • WRT

    California Water District Considers WRT Chromium Removal

    See More

Related Products

See More Products
  • M:\General Shared\__AEC Store Katie Z\AEC Store\Images\ND\new site\water-quality-eng.gif

    Water Quality Engineering: Physical / Chemical Treatment Processes

  • nat-engineered-solutions-dr.gif

    Natural and Engineered Solutions for Drinking Water Supplies

  • M:\General Shared\__AEC Store Katie Z\AEC Store\Images\ND\new site\principles-of-water-treat.gif

    Principles of Water Treatment

See More Products
×

Dig deeper into the drilling and water supply industry!

Build your knowledge with The Driller, covering the people, equipment and technologies across drilling markets.

SIGN UP NOW
  • RESOURCES
    • Advertise
    • Contact Us
    • Directories
    • Store
    • Want More
    • Classifieds
  • SIGN UP TODAY
    • Create Account
    • eNewsletters
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey/Respondent Access
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • YouTube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing

The Driller
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
The Driller
  • NEWS
    • Water
    • Geothermal
    • Construction
    • Environmental
    • Mining
    • All Industry News
  • CLASSIFIEDS
  • EQUIPMENT
    • Rigs & Heavy Equipment
    • Consumables
    • Pumps
    • Featured Products
  • SAFETY
  • VIDEOS
    • Newscast
    • Drill Talks
    • Ask Brock
    • Emerging Drillers
  • EDUCATION
    • Drilling Business Insights
    • Reference Desk
    • Sponsored Insights
  • SOURCEBOOK
  • EVENTS
    • Conferences & Demo Days
    • Newscast LIVE
  • SUBMIT
    • Drillers @Work
  • ABOUT
    • Contact
    • Advertise
  • SIGN UP