Study of the variation of ecotoxicity at different stages of domestic wastewater treatment using Vibrio-qinghaiensis sp.-Q67
2011
Ma, Xiaoyan Y. | Wang, Xiaochang C. | Liu, Yongjun J.
A bioassay using the luminescent bacterium Vibrio-qinghaiensis sp.-Q67 associated with solid-phase extraction (SPE) was developed for evaluating the variation of ecotoxicity along with the reduction of organic substances in a domestic wastewater treatment plant employing an oxidation ditch process. With effective elimination of the interference from all inorganic substances by the SPE operation, the ecotoxicity of the water, as expressed by the toxicity impact index, TII₅₀ (%) after a model-based regression and parameter transformation, was found to decrease from 50.51% in the influent to 25.84% after the grid chamber and then to 1.38% for the secondary effluent, but the final chlorination stage resulted in a slight TII₅₀ increase. Of the two typical tertiary treatment processes, coagulation could not assist further reduction of the ecotoxicity while carbon adsorption could reduce the TII₅₀ to as low as 0.96%. When enhanced primary treatment was conducted, the influent TII₅₀ could be directly reduced to 7.36%. A good correlative relationship was found between the total COD concentration and the TII₅₀ value at different stages of the wastewater treatment process.
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