TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: A series of dilutions of the whole effluent sample is prepared. Each dilution of the whole effluent sample is individually combined with the culture of particle-feeding flagellate to determine a dose response curve. The method includes filtering a second aliquot of the whole effluent sample through a filter having a defined pore size to produce a filtered whole effluent sample from which particulate materials greater in size than the defined pore size have been removed; combining the filtered whole effluent sample with a second culture of particle-feeding flagellate; determining the growth of the second particle-feeding flagellate culture in the presence of the filter whole effluent sample; and comparing the growth of the second particle-feeding flagellate culture in the presence of the filtered whole effluent sample to the growth in the presence of the unfiltered whole effluent sample, where the difference in the growth is indicative of the presence of particulate toxic substances in the whole effluent sample. A series of dilutions of the filtered whole effluent sample is prepared. Each dilution of the filtered whole effluent sample is individually combined with the culture of particle-feeding flagellate to determine the dose response curve. The method further comprises recovering a particulate fraction from an aliquot of the whole effluent sample; combining the particulate fraction with a third culture of particle-feeding flagellate; determining the growth of the particle-feeding flagellate culture in the presence of the particulate fraction; and comparing the growth of the particle-feeding flagellate culture in the presence of the particulate fraction to the growth in the presence of the unfiltered whole effluent sample. A series of dilutions of the particulate fraction is prepared. Each dilution of the particulate fraction is individually combined with the culture of particle-feeding flagellate to determine the dose response curve. The method may further comprise monitoring the growth of the second culture of particle-feeding flagellate in the presence of the whole effluent; and comparing the growth of the first and second cultures, where the mean size of the flagellates in the first and second cultures is different.    TECHNOLOGY FOCUS - BIOLOGY - Preferred Component: The particle-feeding flagellate is Tetramitus rostratus in flagellate form; or Chilodenella uncinata, Bodo caudataus, Cercomonas longicauda, Diplonema ambulatory, Scytomonas pusilia, or Bodo designis.