Recommendation on Target Level of Tetramethylammonium Hydroxide (TMAH) in Wastewater Management toward Protection of Aquatic Organisms

Abstract

Tetramethylammonium hydroxide (TMAH) , which is mainly used in the manufacturing process of semiconductors and liquid-crystal panels, is not subject to effluent regulation under the Water Pollution Control Law. Therefore, the possibility is not excluded that some portion of TMAH used is released into the environment, and the effects of TMAH on aquatic organisms are of concern. In this study, we conducted reproduction tests with Ceriodaphnia dubia and short-term toxicity tests on embryonic and sac-fry stages of zebrafish to set a management target value of TMAH concentration in wastewater. As a result, the concentrations yielding no observed effect on Ceriodaphnia dubia and zebrafish were 0.0158 and 500 mg L-1 , respectively, indicating a high sensitivity of Ceriodaphnia dubia to TMAH. Therefore, given that the dilution ratio of wastewater in public water bodies is 10 times, the TMAH concentration in wastewater discharged directly from a factory site to public waters should be managed to be below 0.158 mg L-1 in consideration of the protection of aquatic organisms.