Browsing by Author "Hsu, Hsiu-Feng"

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Extent of Precipitation and Sorption During Copper Removal from Synthetic Wastewater in the Presence of Sulfate-Reducing Bacteria
(2009-06-01)
Hsu, Hsiu-Feng
;
Kumar, Mathava
;
Ma, Ying-Shih
;
Lin, Jin-Gaw
;
環境工程研究所
A sulfate-reducing bacterial culture was successfully enriched from the seed sludge of anaerobic sludge digester. Sulfate-reducing bacteria (SRB) in the enriched culture (around 42%) were characterized by fluorescence in situ hybridization (FISH) with group and genus specific 16S rRNA-targeted oligonucleotide probes. Desulfosarcina, Desulfococcus, Desulfofaba, and Desulfofrigus spp. were identified as the dominant species of the enriched SRB. Subsequently, batch experiments were conducted at initial copper and sulfate concentrations of 10 and 300mg/L, respectively, to quantify the ability of the enriched SRB in simultaneous sulfate reduction and copper removal. Sulfate reduction efficiencies of the culture in the absence (biotic system without copper, BS-1) and the presence (biotic system with copper, BS-2) of copper were 96.8 and 98.8%, respectively, after 6 days. In BS-2, 99.2% copper removal was observed after 1 day. However, 67% of copper was removed by chemical precipitation and bioaccumulation. No significant inhibition of bacterial growth was observed at the copper concentration studied, that is, 10mg/L. Chemical precipitation as hydroxide/carbonate caused a copper removal of 44% in AS-1 (abiotic system without lactate) and 36% in AS-2 (abiotic system with lactate), after 6 days. However, the majority of copper was removed as copper sulfide well before the occurrence of copper hydroxide precipitation. Energy dispersive X-ray spectroscopy (EDS) analysis of the precipitates obtained from biotic and abiotic systems confirmed the origin of copper sulfide as the result of SRB. As a whole, the results of this study could be useful to understand the mechanisms of copper removal, i.e. chemical precipitation, bioprecipitation and biosorption/bioaccumulation during sulfate reduction by SRB.
Simultaneous sulfate reduction and copper removal by a PVA-immobilized sulfate reducing bacterial culture
(2010-06-01)
Hsu, Hsiu-Feng
;
Jhuo, Yu-Sheng
;
Kumar, Mathava
;
Ma, Ying-Shih
;
Lin, Jih-Gaw
The effect of a sulfate reducing bacteria immobilized in polyvinyl alcohol (PVA) on simultaneous sulfate reduction and copper removal was investigated. Batch experiments were designed using central composite design (CCD) with two parameters, i.e. the copper concentration (10-100 mg/L), and the quantity of immobilized SRB in culture solution (19-235 mg of VSS/L). Response surface methodology (RSM) was used to model the experimental data, and to identify optimal conditions for the maximum sulfate reduction and copper removal. Under optimum condition, i.e. similar to 138.5 mg VSS/L of sulfate reducing bacteria immobilized in PVA, and similar to 51.5 mg/L of copper, the maximum sulfate reduction rate was 1.57 d(-1) as based on the first-order kinetic equation. The data demonstrate that immobilizing sulfate reducing bacteria in PVA can enhance copper removal and the resistance of the bacteria towards copper toxicity. (C) 2010 Elsevier Ltd. All rights reserved.