Most activated carbon is produced by "activating" charcoal from coconut shells or coal by roasting at 800 - 1000 °C in the presence of water vapour and CO₂. Acid washing removes much of the residual oxides and other soluble material. Activated carbon used in water treatment usually has pore sizes ranging from 500-1,000 nm and a surface area of about 1000 square meters per gramme. Carbon is used as granules or moulded and encapsulated cartridges which produce fewer fine particles.

Activated carbon reacts chemically with 2-4 times its weight of chlorine, producing chlorides. This reaction is very rapid and small carbon filters can effectively remove chlorine from water. The breakdown of chloramine by carbon is a relatively slow catalytic reaction producing ammonia, nitrogen and chloride; larger volumes of carbon are needed. Organic fouling can reduce the effectiveness of the carbon and is dependent on the local water supply. This should be considered when sizing its carbon units.

The second application of activated carbon is in the removal of organic compounds from potable water. Activated carbon takes up water contaminants by virtue of ionic, polar and Van der Waals forces, and by surface-active attraction. Activated carbon beds are prone to releasing fines and soluble components into the water stream and do not remove all dissolved organic contaminants, but their use can produce a significant reduction in TOC. A purer form of activated carbon made from polymer beads is sometimes used for this application.

The large surface area and high porosity of activated carbons along with material they trap, make them a breeding place for micro-organisms. Activated carbon beds need to be periodically sanitised or changed regularly to minimise bacterial build-up.

PICA: The specialist in activated carbon

PICA is a Veolia Water Solutions & Technologies subsidiary totally dedicated to the production of activated carbons and services connected to the product's implementation.

www.picacarbon.com/en/