Acute Toxicity of Pulp-Paper Mill Effluent to Zebrafish

摘要

Toxicity assessment is an important aspect in wastewater quality monitoring, as it provides compete response of test organism to all component of wastewater. Toxicity of the effluent from 5 pulp-paper mill (Pp1-Pp5) was evaluated in an acute toxicity study using zebrafish (Danio rerio) bioassay. Toxicity test results revealed 48 hr LC_(50) values >100 for Pp1 and Pp5. For Pp3 and Pp4 it was 70.71%. Pulp-paper mill effluent (Pp2) showed varying acute toxicity (LC_(50)), namely 70.71, >100 and 35.35% for 1st, 2nd and 3rd round of sampling. The linear regression analysis reflected statistical significance between exposure concentration and mortality of fish (≥ 0.89 to 0.99) for pulp-paper mill effluents (Pp2, Pp3, Pp4). The linear correlation (R2) was high (≥ 0.99) except for the effluent sample (Ppiand Pp5) having no toxicity. General criteria of toxicity classification revealed that out of 5 paper mill effluents tested 3 were minor acutely toxic having 48 hr LC_(50) in between >35.35-70.71% and 2 was not acutely toxic (>100%). The toxicity classification based on toxic unit (TU) also showed similar result. Of the 15 effluent samples tested 7 were toxic and 8 were non-toxic. Thus 46.6% samples were toxic and 53.4% as non-toxic. Result of this study also suggested that zebrafish bioassay is a sensitive method for evaluating the aquatic toxicity of pulp-paper mill effluents.