Ecotoxicity comparison of organic contaminants and heavy metals using Vibrio-qinghaiensis sp.-Q67

By using the Vibrio-qinghaiensis sp.-Q67 test, the concentration-inhibition relationships were established for comparing the ecotoxicity of selected organic compounds and heavy metals. The toxicity indices for the four organic compounds were 11–628 mg/L in terms of EC50,TOC (EC: effective concentration, TOC: total organic carbon), with the toxicity in an order of linear alkylbenzene sulfonate > ciprofloxacin > phenol > acetaminophene, while that for the six heavy metals were 0.40–2.74 mg/L in terms of EC50,metal with the toxicity in an order of Cd > Hg > Zn > Pb > Cr > Cu. Through extracting organic matter from the raw sewage and secondary effluent of a wastewater treatment plant (WWTP), their EC50,TOC was measured as 94.5 and 125.2 mg/L, respectively, indicating that WWTP reduced not only the organic concentration but also the ecotoxicity of the wastewater. By analyzing the organic and heavy metal contents and the ecotoxicity of five typical industrial wastewaters, it was identified that the coking wastewater had the highest ecotoxicity (toxicity index as EC50,% = 0.18%), which might be mainly caused by organic contaminants, while the ecotoxicity of the electroplating wastewater (EC50,% = 6.08%) would be mainly caused by heavy metals. The ecotoxicity on Q67 could provide a comprehensive evaluation of the wastewater without knowing exactly the contaminants composition.