Evaluation of Daphnia magna as an indicator of toxicity and treatment efficacy of textile wastewaters

The crustacean Daphnia magna was used as the sensor organism and LC50 as a criterion to measure the toxicity of textile wastewater, treated and non-treated. The LC50 was also determined for the following parameters: conductivity, pH, hardness, and for the anion ClO-. For the test of sensitivity to chemicals, Sodium Dodecyl Sulfate (SDS) was used. The daphnids showed sensitivity to SDS similar to earlier studies (16.2+/-6.1 vs. 14.5+/-4.5 mg/L). The LC50 varying the conductivity with NaCl was 9400+/-1260 mu s/cm, corresponding to 0.01 acute toxicity unit (ATU) and with KCI was 1210+/-132 mu S/cm, corresponding to 0.08 ATU. For hardness, the LC50 was 1520+/-173 mg/L as CaCO3, corresponding to 0.06 ATU. For pH, the results obtained were the following: A 48-h LC50 = 9.5+/-1.1 was found. The results for CIO- indicate an LC50 of 0.02+/-0.01 mg/L, corresponding to 3800 ATU. All of the five textile industries studied produced toxic non-treated water (2.1 to 25.4 ATU), and the treated water was also toxic (1.5 to 7.2 ATU), indicating that the five textile industries eliminate toxic water and their treatment plants are not totally efficient. (C) 1999 Elsevier Science Ltd.