Activated Carbon, Res-Kem and The Marketplace

Particle Size:
Carbon typically comes in 12 x 40 mesh (size of granule). 12 mesh is a particle size of 1.7 mm or 0.066 inches. 40 mesh is a particle size of 0.425 mm or .0016 inches. 98% of Res-Kem sales are 12 x 40.
Carbon must be acid washed to remove contaminants on the carbon. The contaminants removed are primarily metals like Iron which are soluble in acidic streams,

Types of carbon:
Coconut shell (80% of market place)
Bituminous coal (20% of market place)
The trend has changed to coconut because the manufacturing process is more efficient than coal because it does not contain as many contaminants. Depending upon the quality of the coal and where it is from, coal can naturally contains metals and heavy metals. If these contaminants are not removed at the factory, they can leach out into your water.

Carbon Quality:
The Iodine Number a test used to quantify the adsorption qualities of activated carbon. Generally, the higher the iodine number, the better the removal quality of activated carbon to remove contaminants in water.

Coconut = 1,000 and more Iodine number.
Coal = Anywhere between 800-1100 Iodine number.

Brands:
The three major brands of activated carbon are:
Calgon with their Centaur brand activated carbon
Jacobi
Norit

Res-Kem offers through Calgon a carbon return program. After filling out a carbon acceptance form and approval, Calgon will take back carbon for reactivation or incineration.

Markets:
Activated carbon is used in the industrial, municipal, commercial and residential markets. Carbon is used to remove chlorine, chloramine, taste, odor, and color from water.

Activated Carbon: Mesh Size

We are often questioned about the differences between 1240 (12 by 40) mesh activated carbon and 830 (8 by 30) mesh activated carbon. The 1240 mesh activated carbon is smaller than the 830 activated carbon.

The screens or the mesh sizes are different. The 12 mesh screen has 12 openings per square inch 12 across and 12 down. The 40 mesh screen has 40 openings per square inch, 40 across and 40 down. Obviously the "holes" of the 12 mesh screen are larger than the "holes" of the 40 mesh screen. It follows that the holes on an 8 mesh screen are larger than 12 and 30 mesh holes are larger than 40 mesh holes.

If you would like a laminated card with this guide, contact Res-Kem.

As part of the manufacturing process the activated carbon companies pass the carbon through various screens to meet the specification.


So if you look at 1240 mesh activated carbon, it shouldn't have particles larger than 12 mesh or smaller than 40 mesh. The 830 mesh activated carbon shouldn't have particles larger than 8 mesh or smaller than 30 mesh.

What difference does this make to the user of the activated carbon? The most commonly used activated carbons for residential POE (point of entry) systems, commercial and industrial systems are 830 and 1240 mesh. We use 1240 mesh activated carbon because it has greater surface area and provides excellent chlorine and organics removal. Because the activated carbon filter acts as a mechanical filter in addition to removing chlorine and adsorbing organics, it will accumulate particles of dirt or crud at the top of the bed. An activated carbon filter is backwashed on a regular basis to remove this and prevent pressure loss across the bed.

In instances where the water contains more turbidity or crud, an 830 mesh activated carbon may be used. Having larger particle size than the 1240 activated carbon, the filter containing 830 mesh activated carbon won't need to be backwashed as often. However, as the particle size increases from a 1240 mesh activated carbon to an 830 mesh carbon, thereby decreasing the backwash flow rate, adsorption capacity will generally decrease.

When we specify an activated carbon it's important to know the water source. If it's city water or well water from a potable source, we can assume there is little if any turbidity and use of a 1240 mesh activated carbon will work well. If an industrial plant is taking water directly from a river or lake there may be disruptions to the clarification system that may cause excess crud or turbidity. In these cases we see the use of 830 mesh activated carbon.

Here is a full glossary of activated carbon definitions.