- A new approach for the evaluation of activated carbon adsorption capacity in the treatment of wastewater or water contaminated by toxic organic compounds is presented. It is based on direct determination of the toxicity in the treated water, as opposed to actual chemical analysis of its constituents. A toxicity bioassay, based upon measurement of bacterial bioluminescence, was utilized for this purpose. The suitability of this approach was judged by applying values of residual toxicities, obtained during batch adsorption experiments with mixtures of pure chemicals and industrial wastes, to traditional mathematical models. The Freundlich model equation could be applied successfully using toxicity values, to yield toxicity-based isotherms and adsorption constants. This approach allows a fast, convenient assessment of selective toxicants adsorption, with a simultaneous evaluation of the effect of the treated water on biota in receiving streams. It may alleviate the need for costly and impractical analytical methods, when complex wastes of unknown or variable composition are to be tested.