How Do Water Purifiers And Filters Work?

Most of us depend entirely on tap water as the source of water for our ponds. We also bath, drink and cook using this tap water, and the water companies say it is the safest and highest quality and yet the sales of bottled water has increased over the years. This reveals something shocking...

Tap water is not pure at all... It is far from this and is harmful in the long run!

Is there a difference between absorption and adsorption?

A sponge readily absorbs water into its porous structure. Ion exchange resins used for purifying water are not porous and so we describe the action by which they attract and retain ions on to their surface as adsorption. Click here for pure water article

There are many new generation adsorptive media that aim to replace or enhance the purifying performance of activated carbon. Some of these absorptive media are natural media, while others only use patented technology that enables them to adsorb most heavy metals and dissolved gases. Lead In Drinking Water

How Do the water purifiers and filters handle the dissolved ions.

When these initial two media have worked on the tap water, there will now only be a small amount of inorganic compounds remaining as ions which can be removed effectively using ion exchange technology.

What is ion exchange?

Ion exchange can be defined as a reversible chemical process in which the specific ions (for example sodium, Na+) are released from the insoluble solid medium (which is the ion exchange resin) and exchanged for none-desirable or target cations such as heavy metals.

There are two distinct forms of ion exchange that can take place within a water purifier -The ion exchange that removes target cations and another which removes target anions.

Ion exchange was invented in 1845 by an English scientist called Thompson who passed an ammonia-rich solution of manure through some ordinary garden soil. He found that the ammonia content of the liquid manure was lowered. He later realized that the soil contained fine particles of a natural material called Zeolite which would even later be shown to have ion exchange properties.

Zeolite is still being used today to remove undesirable ammonia from pond water. The water industry has not looked back since the advent of Zeolite, and has only developed more improved and efficient media to do the job of water purification.

How cation exchange works.

Cation exchange resins and are normally made from an inert compound called polystyrene-divinylbenzene which is heated in its manufacturing process with concentrated sulphuric acid, causing a sulphonic group (SO3-) to be permanently fixed on to the structural chemistry of the resin beads. These sulphonic groups have a negative charge and this causes them to be charged with positively charged ions (cations) typically sodium (Na+), potassium (K+) or even hydrogen (H+).

When tap water which has dissolved cations (such as heavy metals) go through the resin, then these are exchanged for, and trade positions with the loosely held sodium ions on the resin. Eventually the fully reacted resin becomes 'exhausted', and then needs to be replaced.

The better a resin is protected by pre-filtration from fouling contaminants such as iron and chlorine (which can actually cause the resin polymer beads to disintegrate), the longer it's active life will be.

Cation exchange resins will get rid of most metallic, positively charged ions such as barium, manganese, zinc, calcium, cadmium, copper, iron, and magnesium.

If the flow rate has been slow and there has been active areas for cation exchange on the resin, then the levels of contaminant cations would have been lowered, and kept within the resin. The negatively charged contaminants or anions remain and must then be removed before the water can be used to fill the pond.

How do anion exchange works.?

Anion exchange units make use of a different resin that does not work like the cation exchange resin. This resin is charged with either chloride (Cl-) or hydroxyl (OH-) ions, which will then be released into the pond water in exchange for the less desirable contaminant anions. Anion exchange gets rid of nitrates, sulphates and other negatively charged ions.

Mixed bed ion exchange.

These ion exchange media contain both cationic and anionic exchange media, combined in one cartridge. To make sure that there is efficient purification, mixed bed ion exchange resins are usually used in a series of multiple cartridges, preceded as ever, by at least a carbon filter and at best an additional fine micron mechanical pre-filter.

You can read a wide range of water usage articles. They discuss the use of water in the house and home ... topics covered include filters, heaters, softeners and water in the garden.