G. NewcombeAustralian Water Quality Centre, a partner in the Cooperative Research Centre for WaterQuality and Treatment, PMB 3, Salisbury, South Australia, Australia1. INTRODUCTIONThe activated carbon adsorption process is of major importance to the international waterindustry, and its cost effective application is dependent on an understanding of the adsorbentand the processes influencing its use. This chapter gives an overview of the structure ofactivated carbon and the interfacial processes influencing the removal of naturally-occurringcontaminants from drinking water. The chapter describes the application of activated carbonin drinking water treatment, and gives examples of removal of some important contaminants,natural organic material, taste and odour compounds and algal toxins, from drinking water.

2. WHAT IS ACTIVATED CARBON?

2.1. Production of activated carbonActivated carbon can be created from a wide range of natural and synthetic organic rawmaterials. Some of the more common starting materials and activation methods are shown inTable

1. The production process involves carbonisation - heating in the absence of air totemperatures of about 800~ - then activation in the presence of an activating agent, usuallysteam, at temperatures between 850 and 1000 ~ C [1]. Wood-based carbons are oftencarbonised and activated in the same step in the presence of a dehydrating chemical such asphosphoric acid, usually at lower temperatures than steam activation [ 1 ]. Carbons produced inthis way are called chemically activated carbons. The carbonisation process removes most ofthe volatile components in the form of gaseous oxygen and hydrogen compounds. Theremaining carbon atoms form graphite-like structures consisting of sheets of condensedaromatic ring systems. The sheets are held together by dispersion forces and may be flat ordistorted into a more convoluted pore structure. The surfaces of these sheets form the basalplanes of the carbon. The activation step further enhances the pore and graphite-platestructure, burning out any decomposition products remaining from the carbonisation process,and opening the pores. If the activation continues, walls between pores can be destroyed,leading to larger pores and decreased volume of very small pores [2]. There are a number ofrepresentations of the structure of activated carbon in the literature [ 1