Samples were taken from the inlet to, and the outlet from an effluent treatment plant of a papermill in north east Scotland. The concentration of a range of inorganic and organic pollutants was determined. The principal contaminants were found to be cadmium and pentachlorophenol. A respirometric and a luminescence based assay were carried out to assess the bioavailability of pollutants. The luminescence based assay using genetically modified (luminescence-marked) terrestrial bacteria was found to have greater sensitivity and reproducibility than the respirometric analysis, although both techniques were sensitive to the presence of pollutants.