Characterisation of adsorption behaviours of pesticides on activated carbon in drinking water treatment

The insertion of activated carbon in the drinking water treatment allows to deliver water according to the European standards concerning pesticides concentrations (Directive 97/57 - O.J. 27/09/97). To be able to control the use of activated carbon in the global drinking water process, it is necessary to get the adsorption performances of pesticides that could overlap the legal standards. These results can be achieved with the characterisation of the adsorption behaviours of pesticides on activated carbon in different experimental conditions. This characterisation is composed of two complementary parts : on one hand, the static study of adsorption, particularly adapted to the use of powdered activated carbon. It's based on the carrying out of adsorption isotherms whose results are analysed with. the Freundlich equation. on the other hand, the dynamic study, conceived for the use of granular activated carbon. It is founded on the carrying out of experiments on mini-columns and give as results, the breakthrough curve of the herbicide in defined conditions. The interpretation of the relevant parameters values in these two parts allows to characterize the pesticide adsorption behaviour on activated carbon, according to its chemical characteristics and according to the influence of adsorption competitors, mainly the dissolved natural organic matter (N.O.M.). The reported results are relating to four molecules, choosen according to their overlapping potentiality of the legal standards in Belgian superficial water. There are diuron, bentazone, chloridazon and lenacil. The results of the static study allow to compare the adsorption capacities of the activated carbon Filtrasorb 400 toward the four molecules in ultra-pure water, and to determine the N.O.M. influence by collation of adsorption capacities of each pesticide, carried out in superficial water and in ultra-pure water. The results of the dynamic study allow to compare the breakthrough curve profiles of the four pesticides in ultra-pure water and to point out the N.O.M. influence on the evolution of the breakthrough curve profile for each pesticide, carried out in superficial water.