where SEM is the standard error of the mean, s is the sample standard deviation, and n is the number of replications. Data were statistically analyzed using one-way ANOVA with a random series effect. Fisher's multiple post hoc test (α = 0.05) was used to compare treatments. Before tests, inoculum was diluted with pure medium until its absorbance of monochromatic light (688 nm) was in the range of 0.05-0.08 at 10 cm path. To obtain the desired range of concentrations, 19 cm 3 portions of diluted inoculum were mixed with 1 cm 3 of the prepared toxicant solution in OECD medium. For control, 1 cm 3 of pure OECD medium was added. In the range finding tests, the selected IL and DSIL systems were tested in triplicates at a series of geometrically decreasing concentrations: 100, 10, 1, and 0.1 mg dm -3 . The absorbance at 688 nm was tested for each sample using 10 cm-long glass cuvettes, and the measurements were conducted at the start of the experiment and after 72 hours. The contents of all test vessels were mixed and illuminated continuously during the test, and their position was randomized to achieve similar levels of illumination for each sample throughout the experiment. The tests were conducted at 22-23 °C. The rate of inhibition of algae growth was calculated according to the eq. 7: