Water Filtration by Zeolite

This article describes the use of the mineral that is a microporous aluminosilicate and commonly called Zeolite and that can be used to replace the sand in a conventional swimming pool filtration system.

This filter medium is much finer than the sand that it replaces and provides swimming pool water that really does look sparkling.

There are many brands of Zeolite on the international swimming pool market. It is an advanced filtration material that is much more effective than traditional pool filtration mediums such as sand or Diatomaceous Earth (DE)

What is Zeolite?

Zeolitic material was formed as a result of volcanic activity. There are dozens of different minerals that can form Zeolite. Minerals from the northern hemisphere are often very different to those from the southern hemisphere. One of the best swimming pool filter materials comes from New South Wales in Australia. The key mineral ingredient in this Zeolite  is the mineral clinoptilolite that has some properties that are especially useful for swimming pool filtration.

Many different types of Zeolite

One of its properties is that it has an infinitely extending "cage" like structure resulting in large internal pore spaces and a very high surface area, in the range of 20 to 30 m2 per gram. This is best appreciated as a teaspoon of this Zeolite having enough surface area to cover a football field. Imagine the effective surface area in a Zeolite filter!

Ion Exchange Capacity

Clinoptilolite is also chemically active. Within its structure it has calcium, magnesium and sodium ions which it can exchange for pollutants such as ammonium which will be present in the pool water. This process is called "ion-exchange" and is an important mechanism in Zeolite that provides a chemical treatment action in tandem with physically trapping pollutants in the filtration process.

Pollutant adsorption capacity of Zeolite

In addition to Zeolite's ion-exchange capacity, it also has the ability to adsorb a range of pollutant organic-molecules present in swimming pool water. This ability results from its unique surface structure and the surface electrical charge on the surface of the crystalline structure. It also has a secondary pore structure existing between individual crystals which can trap larger organic molecules.

"Double whammy" treatment of pool water!

With all the unique properties of minerals like clinoptilolite the pool water not only gets a superior "physical" treatment but an additional "chemical" treatment, resulting in cleaner pool water. No other filtration medium on the market (such as sand and DE) can produce this "double whammy" treatment of pool water!

The difference in "physical" performance can be explained by the fact that the surface of sand is quite smooth and non-porous. Contaminants can only be trapped between the sand grains. Zeolite not only traps contaminants between grains, but additionally traps contaminants onto its vast pitted surface area and within its porous structure. Thus its ability to attract, capture and hold dirt and other contaminants is far greater than conventional filtration materials. It also traps finer particles such as colloids and can filter to diatomaceous earth standards or better. This translates to exceptional pool-water clarity and sparkle.

Most contaminants in pool water are of organic origin

From the "chemical" perspective, it is important to understand that most contaminants in pool water are of organic origin produced by bathers (human detritus from skin cells to urea). These complex organic substances contain nitrogen that eventually break down into ammonia/ammonium. Chlorine, used for disinfection, combines both with the ammonia and with these organic pollutants, to form irritating and dangerous compounds called Chloramines.

Chloramines are the compounds generally responsible for the acrid odors and burning eyes in pools. By removing ammonium by ion-exchange, Zeolite significantly reduces the propensity to form these compounds. 

In order to “backwash” and restore the "chemical" capacity of Zeolite, the ion-exchange process is effectively reversed. This is achieved by making sodium ions displace the captured ions such as ammonium. In practice, this is simply carried out by fully soaking the filter with a salt solution overnight.

Anyone with a pool who is using sand as a filtration material should benefit from moving to a Zeolite type of filtration material.