Pesticide removal for drinking water production

Pesticides can be removed from water by adsorption on Granular or Powdered Activated Carbon (GAC) or (PAC). Three major problems occur in this process: performance in scale-up adsorbers, random displacement of preadsorbed pesticides, and on-line monitoring of pesticide concentrations. This paper first reviews current knowledge in the area and then focuses on the measurement of static and dynamic adsorption capacity by adsorption isothermes and the Rapid Small-Scale Column Test (RSSCT). The experiments were performed using water with or without Natural Organic Matter (NOM) and at pesticide concentrations ranging from 0.1 to 10 mug/l; The results show that the adsorption kinetics are rapid and reversible; it seems that the Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is initially adsorbed into the NOM complex before the adsorption process takes place in the GAG. The adsorption behaviour of NOM-Atrazine may also be affected by attached bacteria on the activated carbon. It is not possible to model "one" molecule of-pesticide "alone" in this system, so it is necessary to understand the global activated carbon-NOM Atrazine system particulary in surface waters with NOM concentrations 1000 times higher than the pesticide concentrations. Finally we study these competitive interactions in a batch reaction system.