Browsing by Author "Kumar, Mathava"

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Anaerobic biotransformation of fluorene and phenanthrene by sulfate-reducing bacteria and identification of biotransformation pathway
(2009-05-30)
Tsai, Jen-Chieh
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
In the present study, anaerobic biotransformation of fluorene and phenanthrene by sulfate-reducing bacteria (SRB) was investigated and biotransformation pathways were proposed. SRB was enriched from anaerobic swine wastewater sludge and its abundance was determined by the fluorescence in situ hybridization (FISH) technique. Batch anaerobic biotransformation studies were conducted with fluorene (5 mg L(-1)), phenanthrene (5 mg L(-1)) and a mixture of the two (10 mg L(-1)). After 21 d of incubation. 88% of fluorene and 65% of phenanthrene were biotransformed by SRB. In contrast to previous studies, a decrease in biotransformation efficiency was observed in the presence of both fluorene and phenanthrene. Throughout the study, sulfate reduction was coupled with biotransformation of fluorene and phenanthrene. However, no increase in bacterial cell density was observed in the presence of an inhibitor, i.e. molybdate. Identification of metabolites by gas chromatography-mass spectrometry (GC-MS) revealed that fluorene and phenanthrene were biotransformed through a sequence of hydration and hydrolysis reactions followed by decarboxylation with the formation of p-cresol (only in the phenanthrene system) and phenol. The metabolites identified suggest novel biotransformation pathways of fluorene and phenenthrene. (C) 2008 Elsevier B.V. All rights reserved.
Assessment of di-(2-ethylhexyl) phthalate (DEHP) in municipal and industrial sludges of taiwan by supercritical fluid extraction (SFE) and gas chromatography with electron ionization detection
(2008)
Cheng, Hsiao-Fen
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
In the present study, DEHP in selected municipal sewage (raw and treated) and industrial sludges of Taiwan was quantified by SFE and GC/EID. As a precursor, the optimal operating parameters of SFE were identified by laboratory experiments using DEHP spiked quartz sand. DEHP extraction efficiency was increased by the addition of modifier i.e. methanol (0.5mL, 7%). DEHP concentration in all sewage sludge (M-1 to M-4) and a textile industry (I-6) samples were above the limit suggested by the European Union (100 mg/kg). The results suggest that excess DEHP concentration observed in the sewage sludge needs considerable attention before disposal.
Assessment of di-(2-ethylhexyl)phthalate (DEHP) Removal in a Rotating Biological Contactor and Activated Sludge Process Treating Domestic Wastewater
(2010)
Cheng, Hsiao-Fen
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Di-(2-ethylhexyl) phthalate (DEHP) is one of the most representative persistent micro-pollutants detected in the sewage sludge. In the present study, the presence of DEHP and its removal in various treatment units of a sewage treatment plant (STP) including an attached growth biological system i.e., a rotating biological contactor (RBC) and a suspended growth biological system i.e., activated sludge process (ASP) were investigated. Representative samples of sewage and sludge were collected at each stage of the STP for 2 years to explore the DEHP flow in the dissolved (DEHP(d)) and adsorbed (DEHP(a)) phases. The combination of RBC with a final clarifier was responsible for 50.4 and 58.2% of DEHP(d) and DEHP(a) removals, respectively. Both DEHP(d) and DEHP(a) removals were greater in RBC compared to ASP, demonstrating that an attached growth biological system is more efficient in the removal of DEHP compared to the suspended growth biological system. A good correlation between DEHP and organic matter removal was observed by using Pearson-correlation matrix approach.
Biodegradation of endosulfan-contaminated soil in a pilot-scale reactor-bio augmented with mixed bacterial culture
(2007-08-01)
Kumar, Mathava
;
Philip, Ligy
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環境工程研究所
;
Institute of Environmental Engineering
A novel mixed bacterial culture was enriched from an endosulfan (6, 7, 8, 9, 10, 10 - hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 3, 4-benzo (e) dioxathiepin-3-oxide) processing industrial surface soil. The cultures were successful in the degradation of aqueous phase endosulfan in both aerobic and anaerobic conditions. Using the cultures, endosulfan degradation in silty gravel with sand (GM) was examined via pilot scale reactor at an endosulfan concentration of 0.78 0.01 mg g(-1) of soil, and optimized moisture content of 40 1%. During operation, vertical spatial variability in endosulfan degradation was observed within the reactor. At the end of 56 days, maximum endosulfan degradation efficiency of 78 0.2% and 86.91 0.2% was observed in the top and bottom portion of the reactor, respectively. Both aerobic and anaerobic conditions were observed within the reactor. However, endosulfan degradation was predominant in anaerobic condition and the total protein concentration in the reactor was declined progressively down the soil depth. Throughout the study, no known intermediate metabolites of endosulfan reported by previous researchers were observed.
Biodegradation of soil-applied polycyclic aromatic hydrocarbons by sulfate-reducing bacterial consortium
(2009)
Kumar, Mathava
;
Wu, Pei-Chi
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Tsai, Jen-Chieh
;
Lin, Jih-Gaw
;
環境工程研究所
In the present study, the potential of polycyclic aromatic hydrocarbons (PAHs) biodegradation by sulfate-reducing bacterial consortium enriched from piggery wastewater was investigated. The batch experiments of soil-applied PAH biodegradation were conducted with a mixture of PAHs, i.e., naphthalene, fluorene, phenanthrene, fluoranthene and pyrene, at a concentration of 50 mu g of each PAH per g of soil. A central composite design (CCD) was applied to determine the experimental conditions of each batch assay. The pH, biomass and ethanol concentrations were selected as independent variables and the PAH removal percentage was considered as a dependent variable. The optimal conditions for PAH biodegradation were found to be a pH between 4 and 6.5, an ethanol concentration less than 35 mg/L and a biomass concentration greater than 65 mg/L. Bench scale experiments were carried out at the optimal conditions. At the end of experiment (27 d), total PAH removals by biodegradation and volatilization were around 74% and 20%, respectively. The order of PAH removal was naphthalene, phenanthrene, fluorene, fluoranthene, and pyrene. Throughout the study, PAH biodegradation was in good correlation with sulfate reduction. Results of the kinetics study indicated a competitive inhibition between PAHs investigated.
Co-composting of green waste and food waste at low C/N ratio
(2010-04-01)
Kumar, Mathava
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Ou, Yan-Liang
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Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, co-composting of food waste and green waste at low initial carbon to nitrogen (C/N) ratios was investigated using an in-vessel lab-scale composting reactor. The central composite design (CCD) and response surface method (RSM) were applied to obtain the optimal operating conditions over a range of preselected moisture contents (45-75%) and C/N ratios (13.9-19.6). The results indicate that the optimal moisture content for co-composting of food waste and green waste is 60%, and the substrate at a C/N ratio of 19.6 can be decomposed effectively to reduce 33% of total volatile solids (TVS) in 12 days. The TVS reduction can be modeled by using a second-order equation with a good fit. In addition, the compost passes the standard germination index of white radish seed indicating that it can be used as soil amendment. (C) 2009 Elsevier Ltd. All rights reserved.
Co-existence of anammox and denitrification for simultaneous nitrogen and carbon removal-Strategies and issues
(2010-06-15)
Kumar, Mathava
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Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
The discovery of anaerobic ammonium oxidation (anammox) has greatly improved the understanding of the nitrogen cycle. Anammox provides great promise for the removal of nitrogen from wastewater, containing high concentration of ammonium. However, the presence of organic carbon is considered as unfavorable to this autotrophic process, i.e. anammox. Most of the real wastewaters contain both organic carbon and nitrogen. Under this circumstance, several processes have been established primarily for the complete removal of organic carbon. Subsequently, the wastewater containing no or low organic carbon and nitrogen is treated via a variety of nitrogen removal processes. The co-existence of anammox and denitrification could be useful for the simultaneous removal of nitrogen and organic carbon in a single system rather than a sequential chain of treatment. This review addresses the microbiology, strategies, consequences and the future research challenges in the co-existence of anammox and denitrification. (C) 2010 Elsevier B.V. All rights reserved.
Degradation kinetics of di-(2-ethylhexyl) phthalate (DEHP) and organic matter of sewage sludge during composting
(2008-06-15)
Cheng, Hsiao-Fen
;
Kumar, Mathava
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
The potential degradation of di-(2-ethylhexyl) phthalate (DEHP) and organic matter of sewage sludge by composting was investigated using laboratory reactor at different operating conditions (E-1, E-2 and E-3). In all conditions, single stage thermophilic phase was observed within 2 days and almost, 60% of DEHP was degraded under this phase. At the end of composting, total DEHP degradation of more than 85% was observed in all conditions and total carbon reduction was 11.8% in E-1, 7.6% in E-2 and 10.8% in E-3. Similar trend was observed in the degradation of total nitrogen. The reduction of volatile solids (VS) in the composting reactors was 5.4% in E-1 (18 days), 5.5% in E-2 (12 days) and 4.3% in E-3 (18 days). The degradation kinetics of DEHP in thermophilic phase (including initial mesophilic phase) and the phase there after were determined by first order and fractional power kinetics, respectively. The significance of experimental parameters in DEHP degradation was assessed by Pearson correlation approach. Elevated temperature produced during composting was effective for the rapid degradation of DEHP from sewage sludge compared to mesophilic treatment. (c) 2007 Elsevier B.V. All rights reserved.
Degradation of carbofuran-contaminated water by the Fenton process
(2009-07-15)
Ma, Ying-Shih
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Kumar, Mathava
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Lin, Jih-Gaw
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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.
Determination of optimal phenanthrene, sulfate and biomass concentrations for anaerobic biodegradation of phenanthrene by sulfate-reducing bacteria and elucidation of metabolic pathway
(2009-11-15)
Tsai, Jen-Chieh
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Kumar, Mathava
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Chang, Sue-Min
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Lin, Jih-Gaw
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環境工程研究所
Anaerobic biodegradation of phenanthrene (PHE) was investigated using an enrichment culture consists predominantly of sulfate-reducing bacteria (87 +/- 6%). Aqueous biodegradation experiments were designed using the rotatable central composite design with five levels. The designed concentrations were 2-50 mg L(-1) for PHE, 480-3360 mg L(-1) for sulfate, and 5-50 mg L(-1) for initial biomass. Experimental results indicated that the biomass concentration was the most significant variable, followed by the sulfate and PHE concentrations. The desirability functions methodology (DFM) was applied to find out the maximum specific PHE removal rate (R(s)). The maximum R(s) of 9.0 mg g(-1) VSS d(-1) within the designed ranges was obtained when the initial PHE, sulfate and biomass concentrations were 18.5, 841 and 50 mg L(-1), respectively. The R(s) observed in the present study was higher than the values reported in the previous studies. Subsequently, a confirmation study was performed under the optimal conditions. and the results matched well with the R(s) estimated using DFM. Samples collected during PHE biodegradation experiments inferred the formation of two novel metabolic intermediates, 2-methyl-5-hydroxybenzaldehyde and 1-propenyl-benzene, and subsequently degraded to p-cresol, phenol and hydrocarbons. (C) 2009 Elsevier B.V. All rights reserved.
Development of linear irreversible thermodynamic model for oxidation reduction potential in environmental microbial system
(2007-08-01)
Cheng, Hong-Bang
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Kumar, Mathava
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Lin, Jih-Gaw
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環境工程研究所
;
Institute of Environmental Engineering
Nernst equation has been directly used to formulate the oxidation reduction potential (ORP) of reversible thermodynamic conditions but applied to irreversible conditions after several assumptions and/or modifications. However, the assumptions are sometimes inappropriate in the quanti. cation of ORP in nonequilibrium system. We propose a linear nonequilibrium thermodynamic model, called microbial related reduction and oxidation reaction (MIRROR Model No. 1) for the interpretation of ORP in biological process. The ORP was related to the affinities of catabolism and anabolism. The energy expenditure of catabolism and anabolism was directly proportional to overpotential (eta), straight coefficient of electrode (L-EE), and degree of coupling between catabolism and ORP electrode, respectively. Finally, the limitations of MIRROR Model No. 1 were discussed for expanding the applicability of the model.
Development of simultaneous partial nitrification, anammox and denitrification (SNAD) process in a sequential batch reactor
(2011-05-01)
Lan, Chien-Ju
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Kumar, Mathava
;
Wang, Chih-Cheng
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Lin, Jih-Gaw
;
環境工程研究所
Simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed in a sequential batch reactor (SBR) and the influence of hydraulic retention time (HRT) on the SNAD process was investigated. Around 96% NH(4)(+)-N removal and 87% COD removal were observed at 9 d HRT. Marginal decreases in the removal efficiencies were observed when the HRT was reduced to 3 d or the loading rate was increased by three times. On the other hand, a drastic decrease in NH(4)(+)-N and COD removals were observed when the DO, pH and temperature were dropped shockingly. The response of the SNAD system towards the shock in substrate loading and operating conditions was evaluated by sensitivity index. Finally, the extent of total nitrogen (TN) removal by partial nitrification with anammox and denitrification was modeled using stoichiometric relationship. Modeling results indicated a TN removal of 85-87% by anammox with partial nitrification and 7-9% by denitrification. (C) 2010 Elsevier Ltd. All rights reserved.
Effect of supplementary carbon addition in the treatment of low C/N high-technology industrial wastewater by MBR
(2012-06-01)
Kumar, Mathava
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Lee, Pei-Yun
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Fukusihma, Toshikazu
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Whang, Liang-Ming
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Lin, Jih-Gaw
The effect of supplementary carbon addition for the treatment of high-technology industrial wastewater in a membrane bioreactor (MBR) was investigated. The MBR was operated for 302 days under different C/N (BODL/NH4+-N) ratios, i.e. 0.9-1 to 20 days, 1.6-21 to 42 days, 2.9-43 to 82 days. 3.6-83 to 141 days, 4.8-165 to 233 days and 9.3-240 to 302 days. Irrespective of the C/N ratios investigated, SS and BOD5 removal efficiencies were above 95% and above 80% COD removal efficiency was observed. In addition, complete nitrification was observed throughout the investigation. However, denitrification and total nitrogen removal efficiencies reached their maximum values at the highest C/N ratio (9.3) investigated. Real-time PCR analysis revealed 10 times higher ammonia oxidizing bacteria to total bacteria ratio under the highest C/N ratio condition (9.3) compared to the low C/N ratio condition (1.6). (C) 2012 Elsevier Ltd. All rights reserved.
Extent of Precipitation and Sorption During Copper Removal from Synthetic Wastewater in the Presence of Sulfate-Reducing Bacteria
(2009-06-01)
Hsu, Hsiu-Feng
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Kumar, Mathava
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Ma, Ying-Shih
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Lin, Jin-Gaw
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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.
High-rate composting of barley dregs with sewage sludge in a pilot scale bioreactor
(2008-05-01)
Lu, Li-An
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Kumar, Mathava
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Tsai, Jen-Chleh
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Lin, Jih-Gaw
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環境工程研究所
The feasibility of high-rate composting of barley dregs and sewage sludge was examined using a pilot scale bioreactor. A central composite design (CCD) was used to optimize the mix ratio of barley dregs/sewage sludge and moisture content. The performance of the bioreactor was monitored as a function of carbon decomposition rate (CDR) and total volatile solids (TVS) loss rate. The optimum range of mix ratio and moisture content was found to be 35-40% and 55-60%, respectively. High CO2 evolution rate (CER) and TVS loss rate were observed after 3 days of the composting and the compost was matured/stable after 7 days. Cardinal temperature model with inflection (CTMI) was used to analyze the compost stability with respect to CER as a parameter of composting efficiency. After examining the phytotoxicity, the compost can be promoted for land application. (C) 2007 Elsevier Ltd. All rights reserved.
Influence of organic matter and solute concentration on nitrate sorption in batch and diffusion-cell experiments
(2011-05-01)
Remya, Neelancherry
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Kumar, Mathava
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Mohan, S.
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Azzam, Rafig
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環境工程研究所
Nitrate sorption potentials of three surface soils (soils-1-3) were evaluated under different solute concentrations. i.e. 1-100 mg L(-1). Batch and diffusion-cell adsorption experiments were conducted to delineate the diffusion property and maximum specific nitrate adsorption capacity (MSNAC) of the soils. Ho's pseudo-second order model well fitted the batch adsorption kinetics data (R(2) > 0.99). Subsequently, the MSNAC was estimated using Langmuir and Freundlich isotherms; however, the best-fit was obtained with Langmuir isotherm. Interestingly, the batch adsorption experiments over-estimated the MSNAC of the soils compared with the diffusion-cell tests. On the other hand, a proportionate increase in the MSNAC was observed with the increase in soil organic matter content (OM) under the batch and diffusion-cell tests. Therefore, increasing the soil OM by the application of natural compost could stop nitrate leaching from agricultural fields and also increase the fertility of soil. (C) 2010 Elsevier Ltd. All rights reserved.
Interpretation of redox potential variation during biological denitrification using linear non-equilibrium thermodynamic model
(2012-02-01)
Cheng, Hong-Bang
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Kumar, Mathava
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Lin, Jih-Gaw
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環境工程研究所
;
Institute of Environmental Engineering
In this study, the oxidation reduction potential (ORP) of biological denitrification processes is interpreted based on the MIRROR model No. 1, a linear non-equilibrium thermodynamic model developed in an earlier study. The model interconnects the affinities of catabolism and anabolism, the driving forces of microbial metabolism, with the system ORP and reaction rates of biological processes. Experimental results reported in the literature were used for calibrating the MIRROR model No. 1 to determine the optimal values of model stoichiometric, kinetic, and phenomenological parameters; the calibrated model was then used to simulate laboratory data. The simulation results agree well with the experimental observations. There is a close relationship between the affinities of catabolism and the system ORP of the biological denitrification process, but the ORP variation per unit affinity of catabolism is not a constant but proportional to the molarity of electrons transferred catabolically. The linear relationship between redox potential and reaction rate, which is derived based on MIRROR model No. 1, is subsequently verified by the experimental results reported in the literature. This linear relationship enables evaluation of the biological denitrification rate based on the real-time monitoring of the system ORP. (C) 2011 Elsevier Ltd. All rights reserved.
Landfill-leachate treatment by simultaneous partial nitrification, anammox and denitrification (SNAD) process
(2011-08-01)
Wang, Chih-Cheng
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Kumar, Mathava
;
Lan, Chien-Ju
;
Lin, Jih-Gaw
;
環境工程研究所
Simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed in a sequential batch reactor (SBR), and the application of SNAD process for landfill-leachate treatment was investigated. The SNAD process was developed from the biomass of a full-scale landfill-leachate treatment plant. After the adaptation of biomass, the SBR was operated in four stages (I-IV) with varying nitrogen loading rates (NLRs), i.e. 118-280 mg-N/L/d, and organic loading rates (OLRs), i.e. 100-200 mg/L/d. The increase in the NLR has proportionately reduced the NH(4)(+)-N removal. However, the NO(2)(-)-N concentration was close to zero and the NO(3)(-)-N concentration was less than 36 mg/L in all the stages. A consistent chemical oxygen demand (COD) removal was observed in stages I to IV, which indicate that the SBR was not affected by the increase or decrease of the OLR. The total nitrogen removal in the SBR was mainly achieved by partial nitrification and anammox (69-88%) that was evaluated by a stoichiometric model. Moreover, the influence of NLR and OLR on the SNAD process was determined based on sensitivity index (SI). The SI values indicate that the SNAD process was highly affected by the influent NH(4)(+)-N compared to COD.
Nano-bubble flotation technology with coagulation process for the cost-effective treatment of chemical mechanical polishing wastewater
(2007-12-01)
Tsai, Jen-Chieh
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Kumar, Mathava
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Chen, Shen-Yi
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Lin, Jih-Gaw
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環境工程研究所
The feasibility of nano-bubble flotation technology (NBFT) with coagulation/flocculation process for the enhanced treatment of chemical mechanical polishing (CMP) wastewater was investigated through laboratory and pilot-scale experiments. As a precursor, the effective combination of activator/collector was identified using a laboratory-scale flotation reactor. The results showed that polyaluminum chloride (PAC)/sodium oleate (NaOl) was the best combination of activator/collector, respectively and its application in the NBFT with coagulation process increased the wastewater clarification efficiency by 40% as compared with traditional coagulation/flocculation process. More than 95% turbidity, total solids and total silica removal efficiencies were observed in the pilot-scale flotation experiments. From the results, it was found that NBFT with coagulation process could be performed effectively at an optimum PAC concentration of 50-60 mg/L (as Al), NaOl concentration of 5-10 mg/L with a recycle ratio of 10-20% and I h hydraulic retention time HRT. The cost and performance assessment reflected that CMP wastewater could be treated efficiently at a minimum cost using the present approach. (c) 2007 Elsevier B.V. All rights reserved.
Photo-Fenton pretreatment of carbofuran - Analyses via experimental design, detoxification and biodegradability enhancement
(2011-10-10)
Lu, Li-An
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Ma, Ying-Shih
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Kumar, Mathava
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Lin, Jih-Gaw
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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.