Abstract
A Ceriodaphnia dubia chronic toxicity test of wastewater with five dilutions has been proposed for wastewater management by the National Institute for Environment Studies. In contrast, a convenient and economical daphnia magna acute toxicity test has also been proposed for wastewater management. In this study, the Daphnia magna acute toxicity test was conducted using wastewater samples from five factories, with and without the addition of inorganic salts and pH adjusted to 5.8 or 8.6. Furthermore, the toxicity of five pure chemicals dissolved in dechlorinated tap water and a solution of inorganic salts was tested. It was demonstrated that in many cases, the inhibition decreased with the addition of salts and was lower in the basic region than in the neutral and acidic regions. From these results, the effect of discharging wastewater after dilution in the water environment with various inorganic salt components could not be evaluated by the proposed dilution test. Thus, a method for managing wastewater discharge was proposed based on the acute toxicity of the undiluted wastewater to Daphnia magna.
