Toxicity assessment of Tehran water treatment sludges using bioassay tests

The 48-, 72- and 96-h acute toxicity and 14-d chronic toxicity of the sludge of treatment plant No. 1, 3 and 5 were examined based on the survival percentage and fertility changes of Daphnia magna and Eisenia fetida. The highest percentage of D. magna death in the acute toxicity test appeared in treatment plant No. 1 sludge sample. The 48-h and 72-h LC₅₀ of treatment plant No. 1 sludge on D. magna were calculated to be 86.81 and 44.307% volume of the sludge, respectively. The release of untreated sludge into the environment could adversely affect the life of organisms.