INT-Dehydrogenase 시험법에서 슬러지 일령이 Cr6+, Zn2+ 및 Cd2+ 독성에 미치는 영향
Effect of Sludge Age on the Toxicity of Cr6+, Zn2+, and Cd2+ in INT-Dehydrogenase Assay
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This study was initiated to elucidate the relation between the toxicity of Cr6+, Zn2+, and Cd2+ and sludge age (Solids retention time, SRT). The effect of SRT on the toxicity of Cr6+, Zn2+, and Cd2+ in activated sludge system was investigated with INT-dehydrogenase assay. Experimental results showed that the inhibitory effects of Cr6+, Zn2+, and Cd2+ were reduced as the sludge age increased from SRT 5 d to SRT 25 d. It is noteworthy that the experimental results enabled to determine the relative toxicity of the tested metals depending on the sludge age. At the SRT of 5 and 9 days, the order of toxicity of the three metals to the activated sludge was Cr6+ > Zn2+ > Cd2+ (the IC50 value of Cr6+, Zn2+, and Cd2+ was 16.15, 25.90, and 32.49 mg/L, respectively) and Zn2+ > Cr6+ > Cd2+ (the IC50 value of Cr6+, Zn2+, and Cd2+ was 39.12, 27.93, and 42.31 mg/L, respectively), respectively. However, the toxicity of three metals was almost same at the SRT of 14 and 25 days (the range of IC50 in SRT 14 and 25 days was from 49.80 mg/L to 53.44 mg/L among three heavy metals). This results would be explained by that the quantity of biopolymer formed in short SRT was small, whereas that in long SRT was large. Consequently, it is recommended that sludge age be maintained at long SRT in order to avoid the toxicity inhibition of heavy metals such as Cr6+, Zn2+, and Cd2+.
Abstract
This study was initiated to elucidate the relation between the toxicity of Cr6+, Zn2+, and Cd2+ and sludge age (Solids retention time, SRT). The effect of SRT on the toxicity of Cr6+, Zn2+, and Cd2+ in activated sludge system was investigated with INT-dehydrogenase assay. Experimental results showed that the inhibitory effects of Cr6+, Zn2+, and Cd2+ were reduced as the sludge age increased from SRT 5 d to SRT 25 d. It is noteworthy that the experimental results enabled to determine the relative toxicity of the tested metals depending on the sludge age. At the SRT of 5 and 9 days, the order of toxicity of the three metals to the activated sludge was Cr6+ > Zn2+ > Cd2+ (the IC50 value of Cr6+, Zn2+, and Cd2+ was 16.15, 25.90, and 32.49 mg/L, respectively) and Zn2+ > Cr6+ > Cd2+ (the IC50 value of Cr6+, Zn2+, and Cd2+ was 39.12, 27.93, and 42.31 mg/L, respectively), respectively. However, the toxicity of three metals was almost same at the SRT of 14 and 25 days (the range of IC50 in SRT 14 and 25 days was from 49.80 mg/L to 53.44 mg/L among three heavy metals). This results would be explained by that the quantity of biopolymer formed in short SRT was small, whereas that in long SRT was large. Consequently, it is recommended that sludge age be maintained at long SRT in order to avoid the toxicity inhibition of heavy metals such as Cr6+, Zn2+, and Cd2+.
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