Since 2009, Ministry of the Environment, Japan has discussed the issues in using "Whole Effluent Toxicity (WET) test" from both technical and legal standpoints. One of the issues is the current expensive cost of the WET test. Therefore, it is necessary to develop a simpler and cheaper toxicity test. In this study, we developed a small-scale algal growth inhibition test (small-scale method) to test for toxicity. Among several test vessel sizes and test medium volumes examined for the small-scale method, the growth rate using a 50 mL glass Erlenmeyer flask with 20 mL of test medium was found to be the most comparable to that of the existing draft protocol of the algal growth inhibition test (the existing method). The developed small-scale method was first evaluated by testing of potassium dichromate and 3, 5-dichlorophenol. In the testing of potassium dichromate, it was shown that the IC₂₅ and control coefficient of variation (CV) of the growth rate were at acceptable levels compared with findings from the Japanese laboratory. Furthermore, the no observed effect concentration (NOEC), IC₂₅, and IC₅₀ of the wastewater samples by the small-scale method were almost the same as those by the existing method, although the detection power of the small-scale method was somewhat lower. We investigated 25 effluent samples by the developed small-scale method. Algal growth inhibition was confirmed with 8 wastewater samples in the lowest concentration group (20% concentration group). Our results suggest that the developed small scale method is effective for identifying the tendency of algae growth inhibition.
In addition, the developed small-scale method was able to test multiple samples simultaneously. Therefore, it is possible that Toxicity Identification Evaluations (TIEs) can be performed efficiently by our new developed small-scale method.