| Summary: | 碩士 === 朝陽科技大學 === 環境工程與管理系 === 104 === The prosperous industry in Taiwan applied enormous quantity of chemicals and led to very serious wastewater problems. The wastewater generate by electroplating factories is an extremely important one. It contains great amount of toxic compounds and heavy metals. If handled improperly and discharged directly into rivers, lakes, oceans, or other water resources, would have toxic effect to the aquatic environment, and the effect would be persistent, accumulatives, mutagenic and carcinogenic. In this study we took water samples at different steps of wastewater processing procedures, including the final effluent water, from three electroplating factories in Changhua industrial zone. The quality (pH, Chemical Oxygen Demand (COD), Suspended Solid (SS)) and the heavy metal containts of these water samples was measured, the biotoxicity was examined with the yore Microtox toxicity test, the hydrostatic test of Cyprinus carpio and of Daphnia magna. The toxicity of the heavy metals contained in the effluent water of these three factories was simulated and compared to the toxicity of single heavy metal to calculate the co-toxicity coefficient.
The heavy metal contents in the effluent water of the three sampled electroplating factories did not qualify to the wastewater standard established by Environmental Protection Agency (EPA) of Taiwan. The effluent water of factory A, B, and C contained too many of Zn (46.77 mg/L) and Ni (8.33 mg/L), Cr (1.25 mg/L) and Zn (1.01 mg/L), and Zn (1.95 mg/L) and Ni (0.78 mg/L), respectively. The toxicity of a single heavy metal to Daphnia magna in decreasng was Hg > Cu > Cr > Cd > Ni > Zn > Pb. Mercury is most toxic with a LC50 of 0.012 mg/L. Lead is least toxic with a LC50 of 129.74 mg/L. Among the three sampled electroplating factories, the effluent water of factory A, is industrial plating, is most toxic, with an EC50 of 7.57 mg/L in microtox test and a LC50 of 0.053 mg/L to Daphnia magna. Its cotoxicity coefficient is 61.64, in antagonic effect, while tested with microtox test and is 4871.26, in synergistic effect, while tested with Daphnia magna. Cotoxicity coefficient of the effluent water from all three sampled electroplating factories indicated compound heavy metals had antagonic effect to Vibrio fischeri (Microtox test) and had very high, in contrary, synergistic effect to Daphnia magna.
The results of biotoxicity tests of this study were combined with the results studied previously by this laboratory to compare the correlation between the TUa of effluent water of the three sampled electroplating factories and the chemical oxygen demand (COD) of water quality. The relationship is not steady. Correlation coefficient R2 is 0.3565,0.0006 and 0.8748 for the three factories, respectively.
All three biotoxicity test applied in this study have similar sensitivity to the toxicity of heavy metals. The Microtox method requires shortest time and can act as a quick bioassay method for the quality of wastewater of electroplating factory. Whereas the Cyprinus carpio test can act as an chronic test for understanding does the effluent water be toxic to vertebrate too.
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