Evaluation of Toxicity for Commercial Red Mud Pellets Using Pseudokirchneriella subcapitata and Daphnia magna

The toxicity of red mud (RM) pellets for water purification was evaluated using Pseudokirchneriella subcapitata and Daphnia magna in a lab-scale experiment. According to the algal growth inhibition test, both specific growth rates and relative growth rates of P. subcapitata decreased, and the growth inhibition rates increased (R 2 =0.97, p 1.6 g/L). Also, based on the acute toxicity evaluation test on D. magna, toxic unit (TU) values ranged between 0.00 and 2.83, and increased with an increase in the concentration of RM pellets in the aqueous solution. A correlation analysis indicated that the pH of RM pellets was statistically correlated with TU values (R 2 =0.77, p=0.02). The environmental implication from this study is that the concentration of RM pellets in an aqueous solution needs to be lower than 4.4 g/L to keep the maximum permissible TU value less than 1.0.