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Wuxi, China

This study presents an analytical method for the determination of petroleum oils in sewage sludge samples using infrared spectrophotometry. The proposed method is based on the use of ultrasonic solvent extraction for sample preparation. Analytical conditions were studied and optimized through uniform experimental design of U 9*(9 5). The optimized experimental conditions were obtained as follows: the extraction temperature was 50 °C, the extraction time was 45 min, the volume of extractant was 30 mL, and the ultrasonic power was at 250 W. The moisture content of the sewage sludge samples was below 10%. Similar extraction effects could be achieved through both ultrasonic solvent extraction and Soxhlet extraction methods. The detection limit was 0.9 mg kg -1 (k = 3, N = 8) with 91.6-102.0% recovery. The relative standard deviation (RSD, n = 5) for the measurements of the sewage sludge samples was in the range of 1.6% and 3.5%. The proposed method was validated by the analysis of simulation soil samples and successfully applied to the determination of petroleum oils in real samples of sewage sludge with satisfactory results. © 2012 The Royal Society of Chemistry.


In this work, an improved hydride-generation atomic fluorescence spectrometry (HG-AFS) method for the determination of total arsenic (As) in wastewater and sewage sludge samples was applied. The samples were digested completely with mixtures of HNO3 and HClO4. Analytical conditions were studied and optimized through uniform experimental design U*10(108) combined with a single factor test. A mathematical model was established, and a quadratic polynomial stepwise regression analysis by using the DPS software was employed to obtain the factors that impact the fluorescence intensity. This technique is then combined with a single factor test. The optimized experimental conditions were obtained as follows: PMT voltage was 305 V, lamp current was 70 mA, KBH4 concentration was 2.0% (m/v), carrier liquid (HCl) concentration was 5% (v/v), carrier gas (Ar) flow rate was 300 mL min-1, and reaction acidity was 10% (v/v) HCl. The pre-reduction of all forms of As to As(III) was performed by using a mixed solution of 1% thiourea and 1% ascorbic acid. The content of total As was determined under the optimized experimental conditions. The detection limits for total As in wastewater and sewage sludge were 0.09 μg L-1 and 0.01 mg kg-1, respectively. The linear ranges were 0.24-100 μg L-1, and the recovery was 91.0-102.0%. The relative standard deviation (RSD, n = 5) for eleven replicate measurements of the certified reference materials containing 60.6 ± 4.2 μg L-1 As (certified sample of water) and 10.7 ± 0.8 mg kg-1 As (certified sample of soil) were 3.1% and 1.6%, respectively. The proposed method was validated by the analysis of certified reference materials and was successfully applied to the determination of total As in real samples of wastewater and sewage sludge with satisfactory results. © 2012 Copyright Taylor and Francis Group, LLC.


Li J.,Jiangnan University | Luo G.,Wuxi Drainage Company | Gao J.,Wuxi Drainage Company | Yuan S.,Wuxi Drainage Company | And 2 more authors.
Chemistry and Ecology | Year: 2015

In this study, the potential ecological risks and eco-toxicity of heavy metals (Cu, Pb, Zn, Ni, Cd, Cr, As and Hg) in sewage sludge were quantitatively evaluated. Sewage sludge samples were collected from three wastewater treatment plants in Wuxi city during five years from 2009 to 2013. The levels of the eight metals temporally varied. The contents of Zn and Cu in the tested sewage sludge were the highest, followed by Cr, Ni, Pb and As, and the contents of Cd and Hg were the least. The Community Bureau of Reference (BCR) sequential extraction results showed that Zn, Ni and Cd had the highest mobilisation potential, while Cu, Pb, Cr and Hg were not stabilised and would release to the environment under oxidising conditions. The removal efficiency of Cu and Cr was higher than 70%, while that of As, Cd and Hg was less than other heavy metals. The overall potential ecological risk index (RI) of heavy metals in sewage sludge was 1376.34, revealing very high risk. However, the environmental risk values based on the index of geo-accumulation (Igeo) and risk assessment code (RAC) were both low. Cd contamination is the major concern while the treated sewage sludge is used for agricultural purposes. © 2014, © 2014 Taylor & Francis.

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