Abstract
Pseudokirchneriella subcapitata growth inhibition test of wastewater, which was diluted in five stages by mixing of 5%–80% wastewater with 20%–95% OECD medium, was proposed as a wastewater management tool by a research project of the Ministry of the Environment. In this study, the growth inhibition test was conducted in wastewater samples from five factories. Mixtures of 80% wastewater with 20% OECD medium, mixtures of 80% wastewater with 1/50 seawater salts and 20% OECD medium, and 100% wastewater samples after adding a concentrated OECD medium for it to become 100% OECD medium composition were tested. Four types of compounds were tested in this manner. As a result, the inhibition varies greatly in the wastewater from four factories depending on the coexistent inorganic salts. Furthermore, the 20% OECD medium samples show higher inhibition than the 100% OECD medium samples for zinc and copper, but equal or lower inhibition than those for DBS and aniline. Because the concentration and composition of inorganic salts change in the proposed dilution test, the relationship between the dilution rate and inhibition is unclear. Therefore, for wastewater management purposes, the test should be performed in undiluted wastewater by adding a small amount of concentrated OECD medium so it to be 100% OECD medium composition.
