Browsing by Author "Ma, Ying-Shih"

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Degradation of carbofuran-contaminated water by the Fenton process
(2009-07-15)
Ma, Ying-Shih
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, the Fenton process was applied for the degradation of carbofuran from aqueous system. Batch experiments were conducted at two different carbofuran concentrations i.e., 10 and 50 mg/L, and at pH 3. Batch experiments at each carbofuran concentration were designed by central composite design (CCD) with two independent variables i.e. Fe(2+) and H(2)O(2). Experimental results indicate that more than 90% of carbofuran removal was observed within 5 mins of Fenton reaction at 5 mg/L of Fe(2+) concentration and 100 mg/L of H(2)O(2) concentration. Increases in Fe(2+) and/or H(2)O(2) concentrations beyond 5 and 100 mg/L, respectively produced 100% carbofuran removal. Based on the experimental observations, the optimal Fe(2+) and H(2)O(2) dosages required for 10 mg/L of aqueous carbofuran removal were estimated as 7.4 and 143 mg/L, respectively. During this study, three carbofuran intermediates such as 7-benzofuranol,2,3,-dihydro-2,2-dimethyl, 7-hydroxy-2,2-dimethyl-benzofuran-3-one and 1,4-Benzene-di- carboxaldehyde were identified using GC/MS analyses.
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.
Photo-Fenton pretreatment of carbofuran - Analyses via experimental design, detoxification and biodegradability enhancement
(2011-10-10)
Lu, Li-An
;
Ma, Ying-Shih
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
The central composite design (CCD) and response surface methodology (RSM) were employed to evaluate the effect of H(2)O(2) dosage rate (1-10 mg L(-1) min(-1)) and Fe(3+) dosage (1-100 mg L(-1)) in the photo-Fenton treatment of carbofuran and to develop the second-order polynomial equations in terms of carbofuran and dissolved organic carbon (DOC) removals and BOD(5)/DOC ratio with different reaction times. Both H(2)O(2) dosage rate and Fe(3+) dosage have significant effects on the dependable variables. Based on the results of carbofuran removal and BOD(5)/DOC ratio, H(2)O(2) dosage rate of 5.4 mg L(-1) min(-1) and Fe(3+) dosage of 59 mg L(-1) were found to be the favorable reagent dosages for carbofuran degradation. Under these conditions, the toxicity unit measured by Microtox(R) test with 5 min exposure was decreased from 47 to 6 and the biodegradability evaluated by BOD(5)/COD ratio was increased from 0 to 0.76 after 60 min reaction. The results obtained in this study demonstrate that the photo-Fenton process is a promising pretreatment before the application of biological treatment for carbofuran removal from contaminated water/wastewater. (C) 2011 Elsevier B.V. All rights reserved.
Photochemical degradation of carbofuran and elucidation of removal mechanism
(2011-01-01)
Lu, Li-An
;
Ma, Ying-Shih
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
Carbofuran removal by the photo-Fenton reaction was investigated under various H(2)O(2) dosage rate (0-6 mg L(-1) min(-1)) and Fe(3+) dosage (5-50 mg L(-1)). The outcomes demonstrate that the photo-Fenton reaction was influenced by both the factors. An initial carbofuran concentration of 50 mg L(-1) was completely degraded within 30 min, and 93% dissolved organic carbon (DOC) removal was observed after 120 min of treatment at initial pH 3, H(2)O(2) dosage rate of 4 mg L(-1) min(-1) and Fe(3+) dosage of 35 and 50 mg L(-1). However, no significant improvement in the carbofuran removal was observed when the H(2)O(2) dosage rate and Fe(3+) dosage were increased beyond 4 mg L(-1) min(-1) and 35 mg L(-1), respectively. The carbofuran removal was fitted using the pseudo-first order reaction model and the highest apparent rate constant of 10.5 x 10(-2) min(-1) was obtained. Five major carbofuran intermediates were identified, which indicate that C-O bond of the carbamate group and 3-C position of the furan ring were oxidized as a result of the photo-Fenton reaction. (C) 2010 Elsevier B.V. All rights reserved.
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.
Sono-alkalization pretreatment of sewage sludge containing phthalate acid esters
(2011)
Ma, Ying-Shih
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
This work experimentally elucidates the efficiencies of sono-alkalization treatment on municipal sewage sludge. The total solids (TS) concentration of the sewage sludge was pre-adjusted at 29.7 g/L. Two parameters such as sodium hydroxide (NaOH) dosage and sonication time were considered by the central composite design (CCD) program to investigate the effect on the degradation of phthalate acid esters (PAEs) and solubilization of soluble chemical oxygen demand (SCOD). The mean concentrations of dibutyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and butyl benzyl phthalate (BBP) in the sewage sludge were 718, 41 and 8 mg/kg dry weight sludge, respectively. Sono-alkalization process was effective on the degradation of DBP but worthless for DEHP and BBP. Overall degradation of DBP in sewage sludge was estimated to be 100% at the NaOH dosage of 68 mM and sonication time of 2.2 min. Sono-alkalization was responsible for 6,000 mg/L increase of SCOD based on the decrease of volatile solids in sewage sludge.