How it works

Chemical oxidation by the addition of air

Activated carbon is frequently used to remove recalcitrant, non-biodegradable compounds from wastewater. The adsorption capacity of activated carbon with respect to certain molecules like phenol increases when the water to be treated contains high oxygen concentrations. This is mainly due to chemical oxidation of the adsorbed molecules as a result of the presence of dissolved oxygen with activated carbon acting as a catalyst.

Biological purification by means of bacteria

The addition of oxygen stimulates the growth of bacteria in the water. Bacteria reduce wastewater contamination. Normally biologically recalcitrant molecules are first adsorbed on carbon. This slows down the biodegradation process. The PACT process, addition of powdered activated carbon to a traditional biological water treatment plant, is a similar application.

Activated carbon is an excellent support material for bacterial growth. The bacteria form a biofilm layer on the activated carbon. This may have negative effects: the filter may clog up as a result of excessive bacterial growth. The presence of anaerobic bacteria from sulphides may cause undesired odours and colours. However, if the existing contamination and the COD parameters are taken into account, the bacterial growth can be directed so as to produce positive results.