Browsing by Author "Chen, Wen-Hsing"

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Effect of carriers on the performance of anaerobic sequencing batch biofilm reactor treating synthetic municipal wastewater
(2014-11-01)
Dutta, Kasturi
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Tsai, Cheng-Yu
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Chen, Wen-Hsing
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Lin, Jih-Gaw
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環境工程研究所
In this study, effects of granular activated carbon (GAC) and natural zeolite as attached carriers for microbes on anaerobic treatment of synthetic municipal wastewater were evaluated in laboratory scale anaerobic sequencing batch biofilm reactors (ASBBRs). An anaerobic sequencing batch reactor (ASBR) and three ASBBRs, individually named ASBR-1 without any carrier (control), ASBBR-2 with GAC, ASBBR-3 with zeolite, ASBBR-4 with both GAC and zeolite, were operated at 2.5 d HRT with non-fat dry milk to mimic municipal wastewater. The four reactors were successfully started up and attained steady state within two weeks of operation. Total COD and soluble COD removal efficiencies of more than 93% and 98%, respectively, were observed in the four reactors during steady-state. The average biogas productions for ASBR-1, ASBBR-2, ASBBR-3 and ASBBR-4 were 229, 246, 238 and 278 mI/d, respectively. Addition of carriers improved both the COD removal efficiency and biogas production. Apparently GAC improved COD removal efficiency and zeolite improved gas production. SEM results suggested higher number of biomass attached to GAC than zeolite. (C) 2014 Elsevier Ltd. All rights reserved.
Evaluation of biobutanol production from non-pretreated rice straw hydrolysate under non-sterile environmental conditions
(2013-05-01)
Chen, Wen-Hsing
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Chen, Yi-Chun
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Lin, Jih-Gaw
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環境工程研究所
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Institute of Environmental Engineering
The study aims to investigate a cost-effective approach to convert non-pretreated rice straw hydrolysate into biobutanol. The influences of the initial cell concentration and incubation temperature on biobutanol production were evaluated under both sterile and non-sterile conditions. Results indicate that 100% glucose utilization could be achieved for initial cell concentrations greater than 2100 mg/L under both sterile and non-sterile conditions. Regression analyses resolve that under the sterile condition, the maximum butanol productivity of 1.45 g/L/d was projected at 1.96 g/L of cells and 32.3 degrees C, while the maximum butanol yield of 0.22 g/g was predicted at 2.01 g/L of cells and 26.3 degrees C. These two maximum values could not be projected by the regression analyses for the non-sterile condition. However, this study confirms that a high initial cell concentration of Clostridium saccharoperbutylacetonicum N1-4 can minimize interference from other microbes so that non-sterile biobutanol production is comparable to sterile biobutanol production. (C) 2012 Elsevier Ltd. All rights reserved.
Mass transfer efficiency inside the polyvinyl alcohol-sodium alginate carriers: kinetic changes of immobilized anammox bacteria
(1970-01-01)
Chen, Wen-Hsing
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Lin, Jih-Gaw
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Wei, Yi-Lin
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Chen, Shen-Yi
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環境工程研究所
BACKGROUND Mass transfer inside the plain polyvinyl alcohol (PVA)-sodium alginate (SA) carriers was determined to correlate with nitrogen removal by anaerobic ammonium-oxidation (anammox) bacteria in this study. The anammox bacteria immobilized by the PVA-SA material for nitrogen removal were inoculated into a sequencing batch reactor (SBR) operated at a hydraulic retention time of 4 days and a temperature of 35 +/- 1 degrees C while another identical reactor inoculated with the un-immobilized biomass was run for comparison. RESULTS Results show that the total nitrogen removals were 81 and 92% for the immobilized and un-immobilized biomass, respectively, when the ammonium- and nitrite-nitrogen, both at 200 mg N L-1, were fed into the SBRs. The poorer performance observed from the immobilized biomass was due to the lower mass transfer efficiency. The obtained diffusion coefficient of the ammonium-nitrogen and specific surface area were 15.2 x 10(-6)cm(2)s(-1)and 29.35 m(2)g(-1)gel beads, respectively. In addition, the mass transfer efficiency influenced the kinetics of the immobilized anammox bacteria. Results indicate that the ammonium-nitrogen removal rate of the un-immobilized biomass was 28 to 34% greater than that of the immobilized biomass, while the nitrite-nitrogen removal rate was greater by 9 to 24% for the un-immobilized biomass. This influence was more significant at high levels of ammonium- and nitrite-nitrogen concentrations. CONCLUSION Increasing the mass transfer efficiency inside the plain PVA-SA carriers was needed before using the PVA-SA carriers to immobilize anammox bacteria. (c) 2020 Society of Chemical Industry
Removals of pharmaceuticals in municipal wastewater using a staged anaerobic fluidized membrane bioreactor
(2019-05-01)
Chen, Wei-Hsiang
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Wong, Yu-Ting
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Huang, Tsung-Hsien
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Chen, Wen-Hsing
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Lin, Jih-Gaw
The staged anaerobic fluidized membrane bioreactor (SAFMBR) is effective to remove organic substances with reduced sludge production by minimizing excess waste sludge. This study investigated the removals of four pharmaceuticals present at trace levels in municipal wastewater by using a SAFMBR. The target pharmaceuticals included ibuprofen, naproxen, carbamazepine, and diclofenac. A pilot-scale SAFMBR with hydraulic retention times (HRTs) from 4.5 to 13.5 hr was established and operated for 450 days with a municipal wastewater spiked with four pharmaceuticals. In the results, the BOD and COD removals were effective and limitedly affected the presence of pharmaceuticals. The BOD removal efficiencies in the anaerobic fluidized membrane bioreactor (AFBR) and anaerobic fluidized membrane bioreactor (AFMBR) were 63.5 +/- 28.6% and 81.6 +/- 25.1%, respectively. However, the treatment efficiencies of four pharmaceuticals varied. Naproxen that contains electron donating group was treated efficiently (63.8%similar to 72.1%), whereas the removal efficiencies of ibuprofen (25.0%similar to 32.4%), carbamazepine (16.6-18.5%), and diclofenac (non-detected) remained low. Ibuprofen was less efficient to compete with other electron acceptors in an anaerobic environment. For pharmaceuticals such as carbamazepine with a high acid dissociation constant (pKa = 13.9) or diclofenac with a high octanol-water partition coefficient (log K-ow = 4.51), sorption onto the sludge could be one critical process affecting their concentrations in the water phase. By being positively charged at neutral pH and/or hydrophobic, the pharmaceuticals were initially adsorbed onto sludge, followed by being desorbed when sludge decayed after long operating hours. Nitrogen balance was analyzed to indicate the decay of the bacteria in the AFMBR. Increasing the HRTs only slightly improved the treatment efficiencies (e.g., the naproxen removal was increased from 63.8% to 72.1% when the HRT was increased from 4.5 to 7.5 h). The different processes responsible for the removals of these pharmaceuticals were more critical and their effects were limitedly changed by HRT adjustment, indicating the importance of knowing the properties of a pharmaceutical for selection of a proper treatment approach.
Study of chemical pretreatment and enzymatic saccharification for producing fermentable sugars from rice straw
(2014-07-01)
Chen, Wen-Hsing
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Chen, Yi-Chun
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Lin, Jih-Gaw
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環境工程研究所
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Institute of Environmental Engineering
This study evaluated a cost-effective approach for the conversion of rice straw into fermentable sugars. The composition of rice straw pretreated with 1 % sulfuric acid or 1 % sodium hydroxide solution was compared to rice straw with no chemical pretreatment. Enzymatic saccharification experiments on non-pretreated rice straw (NPRS), pretreated rice straw (PRS), and pretreated rice straw with acid hydrolysate (PRSAH) were conducted in a series of batch reactors. The results indicated that pretreating the rice straw with dilute acid and base increased the cellulose content from 38 % to over 50 %. During enzymatic saccharification, straight aliphatic cellulose was hydrolyzed before branched hemicellulose, and glucose was the major hydrolysis product. The glucose yield was 0.52 g glucose/g for NPRS and was comparable to the yields of 0.50 g glucose/g for PRS and 0.58 g glucose/g for PRSAH. The hydrolysis of rice straw to produce glucose can be described by a first-order reaction with a rate constant of 0.0550 d(-1) for NPRS, 0.0653 d(-1) for PRSAH, and 0.0654 d(-1) for PRS. Overall, the production of fermentable sugars from ground rice straw will be more cost effective if the straw is not pretreated with chemicals.
Treatment of campus domestic wastewater using ambient-temperature anaerobic fluidized membrane bioreactors with zeolites as carriers
(2019-01-01)
Chen, Wen-Hsing
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Tsai, Cheng-Yu
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Chen, Shen-Yi
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Sung, Shihwu
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Lin, Jih-Gaw
An anaerobic fluidized-bed bioreactor (AFBR) connected with an anaerobic fluidized membrane bioreactor (AFMBR) in series with natural zeolites as carriers was used to treat the campus domestic wastewater (chemical oxygen demand (COD) of 130 +/- 38 mg/L) at ambient temperature (20-35 degrees C) in this study. Results indicate that the attached growth of anaerobic microbes was observed on the surface of zeolite and 95% of COD were removed in the AFBR after 30 days of batch operation. When the AFBR-AFMBR system was run with a HRT from 3 to 4 h, the COD, biochemical oxygen demand (ROD), and suspended solid (SS) were removed by 84, 87, and 96%, respectively, with the corresponding effluent COD, BOD, and SS of 20, 8, and 2 mg/L, respectively. Overall, 41% of the COD removal was attributed to coupling with sulfate reduction by sulfate-reducing bacteria in this study. In the AFMBR, the transmembrane pressure remained lower than 0.2 bar at the membrane flux of 10 L/m(2)-h. The membrane module was operated consecutively for 333 days without chemical cleaning. In addition, the maximum substrate utilization rate of 37 g/L-d determined based on the modified Stover-Kincannon equation elucidates that the organics in the campus domestic wastewater were readily biodegraded. This facilitated the AFBR-AFMBR system removing the organics to the levels lower than the discharging limits.