Browsing by Author "Lin, Jr-Lin"

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Algal removal from cyanobacteria-rich waters by preoxidation-assisted coagulation-flotation: Effect of algogenic organic matter release on algal removal and trihalomethane formation
(2018-01-01)
Lin, Jr-Lin
;
Lap-Cuong Hua
;
Shih Kai Hung
;
Huang, Chihpin
;
環境工程研究所
The cyanobacteria-bloom in raw waters frequently causes an unpredictable chemical dosing of preoxidation and coagulation for an effective removal of algal cells in water treatment plants. This study investigated the effects of preoxidation with NaOCl and ClO2 on the coagulation-flotation effectiveness in the removal of two commonly blooming cyanobacteria species, Microcystis aeruginosa (MA) and Cylindrospermopsis raciborskii (CR), and their corresponding trihalomethane (THM) formation potential. The results showed that dual dosing with NaOCl plus ClO2 was more effective in enhancing the deformation of cyanobacterial cells compared to single dosing with NaOCl, especially for CR-rich water. Both preoxidation approaches for CR-rich water effectively reduced the CR cell count with less remained dissolved organic carbon (DOC), which benefited subsequent coagulationflotation. However, preoxidation led to an adverse release of algogenic organic matter (AOM) in the case of MA-rich water. The release of AOM resulted in a poor removal in MA cells and a large amount of THM formation after oxidation-assisted coagulation-flotation process. The reduction in THMformation potential of CR-richwaters is responsible for effective algae and DOC removal by alum coagulation. It is concluded that the species-specific characteristic of cyanobacteria and their AOM released during chlorination significantly influences the performance of coagulation-flotation for AOM removal and corresponding THM formation. (C) 2017 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.
Chemical structures of extra- and intra-cellular algogenic organic matters as precursors to the formation of carbonaceous disinfection byproducts
(2017-11-15)
Hua, Lap-Cuong
;
Lin, Jr-Lin
;
Chen, Pei-Chung
;
Huang, Chihpin
;
環境工程研究所
Algal eutrophication in reservoirs is frequently accompanied by a remarkable increase in the concentration of algogenic organic matter (AOM). Because AOM is well-known as an important precursor to disinfection by-products (DBPs) in drinking water, algal eutrophication poses severe concerns for public health. This study aimed to characterize the chemical properties of AOM from two major origins, i.e. extra-(EOM) and intracellular organic matter (IOM), of a commonly found green alga Chlorella sp. as precursors to trihalomethanes (THMs) and haloacetic acids (HAAs). Particularly, the corresponding relation between the chemical functional structure of EOM and IOM and their THM and HAA formation potential (THMFP and HAAFP) was comprehensively investigated. Results show that IOM chiefly comprised of aromatic and other aliphatic protein-like materials (high organic nitrogen content) those have high activity for chlorine substitution (high UV253/UV203 value) due to the high hydroxyl and amide contents in its chemical structures. EOM alternatively exhibited the characteristics of humic-and fulvic-like materials accompanying with high DOC/DON ratio and aromaticity. However, the chemical structure of EOM had a low tendency for chlorine substitution (low UV253/UV203 value); it was also accompanied by a considerable content of carboxylic moisture, which likely resulted in an unfavorable substitution reaction of EOM with chlorine. As a result, the carbonaceous DBP formation potential (C-DBPFP) showed that IOM yielded higher levels of both THMFP and HAAFP than that yielded by EOM.
Coagulation behavior of Al-13 aggregates
(2008-10-01)
Lin, Jr-Lin
;
Chin, Ching-Ju M.
;
Huang, Chihpin
;
Pan, Jill R.
;
Wang, Dongsheng
The coagulation behavior of Al-13 aggregates formed in coagulation of kaolin was investigated by small angle static light scattering (SASLS), solid-state Al-27 NMR and tapping mode atomic force microscope (TM-AFM). A kaolin suspension was coagulated by PACl containing high content of Al-13 polycation (PACl-Al-13). The results indicated that Al-13 was predominant in destabilizing kaolin particles for PACl-Al-13 coagulation even though at alkaline pH (pH 10). At such high pH, Al-13 aggregates were observed when the dosage of PACl-Al-13 was increased. In addition, the mechanism of coagulation by PACl-Al-13 at alkaline pH was affected by dosage. When the dosage was insufficient, coagulation was caused by electrostatic patch, which led to compact flocs with high fractal dimension (D-f) Interparticle bridging dominated the coagulation when the coagulant dosage approached the plateau of adsorption, which caused the looser flocs with low Df. The in-situ AFM scanning in liquid system proved that the existence of linear A113 aggregates composed of a chain of coiled Al-13 in coagulation by PACl-Al-13 at a high dosage and alkaline pH. Meanwhile, several coiled Al-13 aggregates with various dimensions were observed at such condition. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.
Coagulation dynamics of fractal flocs induced by enmeshment and electrostatic patch mechanisms
(2008-11-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Chin, Ching-Ju M.
;
Pan, Jill R.
;
環境工程研究所
The size and structure of flocs during floc formation were monitored for various coagulation mechanisms. Two distinctive mechanisms, namely, enmeshment and electrostatic patch, govern the dynamics of kaolin particles coagulation by polyaluminurn. chloride (PACl). They were investigated by small angle static light scattering (SASLS) and solid-state Al-27 NMR. In addition, a novel wet SEM (WSEM) was used in-situ to image the morphology of the aggregate in aqueous solution. Synthetic suspended particles were coagulated by two PACl products, a commercial product (PACl) and one laboratory product (PACl-E). The PACl-E contained more than 60% Al-13 while the PACI contained only 7% Al-13, with large percentage of colloidal Al. For coagulation by PACI at neutral pH and high dosage where the strong repulsion between particles occurs, the enmeshment ruled by reaction-limited aggregation (RLA) results in larger sweep flocs as well as higher fractal dimensional structure. For coagulation by PACl-E at alkaline pH and low dosage, the flocs were coagulated predominately by electrostatic patch with Al-13 aggregates. At such condition, it is likely that diffusion-limited aggregation (DLA) predominately rule PACl-E coagulation. The fractal dimension (D-s) values of PACl and PACl-E flocs formed at enmeshment and electrostatic patch increased with dosage, respectively. When breakage of flocs occurs, the breakage rate of PACI-E flocs is slower than that of sweep flocs. By WSEM imaging, the adsorption of spherical Al precipitates onto the particles was observed to form sweep flocs with a rough and ragged contour, while the PACI-E flocs were formed with a smooth and glossy structure. (C) 2008 Elsevier Ltd. All rights reserved.
Effect of Al(III) speciation on coagulation of highly turbid water
(2008-05-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Pan, Jill Ruhsing
;
Wang, Dongsheng
;
環境工程研究所
In Taiwan, the turbidity of raw water for fresh water treatments can sometimes reach as high as 40000 NTU due to intensive rainfall, especially in typhoon seasons. In response, water works often apply large quantities of coagulants such as polyaluminium chloride (PACl). In this study, simulated and natural highly turbid water was coagulated with two PACls, a commercial product (PACl-1) and a laboratory product (PACl-E). The Al species distributions of PACl-1 and PACl-E under various pH conditions were determined, and the corresponding coagulation efficiency was evaluated. The PACl-E has a wider range of operational pH, while the efficiency of PACl-1 peaks at around neutral pH. For simulated water up to 5000 NTU, the PACl-E was superior to PACl-1 at low dosage and in the pH range studied. Similar results were discovered with natural water, except that when the turbidity was extremely high, the coagulation efficiency of PACl-E decreased significantly due to the presence of large amounts of organic matter. The coagulation of PACl-E was closely related to the content of polycationic aluminium (Al-13) while that of PACl-1 was dictated by the amount of Al, The sludge from PACl-E coagulation had better dewaterability when the optimum dosage was applied. The experimental results suggest that for natural water up to 5000 NTU, PACl containing high Al-13 species is recommended for coagulation. In cases when the water contains high organic matter, efficient coagulation depends upon enmeshment by amorphous aluminium hydroxide. (C) 2008 Elsevier Ltd. All rights reserved.
Effect of cell integrity on algal destabilization by oxidation-assisted coagulation
(2015-09-04)
Lin, Jr-Lin
;
Huang, Chihpin
;
Wang, W. M.
;
環境工程研究所
;
Institute of Environmental Engineering
A hybrid oxidation-coagulation process is commonly adopted to destabilize algae and subsequently improve the removal of algae from water through sedimentation and filtration in water treatment plants (WTPs). Preoxidation is crucial to improving algae removal by a coagulation-sedimentation process. The goal of this study was to investigate the effect of oxidation with NaOCl and ClO2 on the cell integrity of algae (i.e. diatoms) and the destabilization of algae by means of Alum coagulation. The effects of oxidation-assisted coagulation on the performance of sedimentation as well as filtration were evaluated. The results show that ClO2 reduces cell integrity more severely than NaOCl during oxidation. The degradation of chlorophyll a and humic-like substances generated by cells ruptured by ClO2 oxidation is stronger than that by NaOCl oxidation. During oxidation both NaOCl and ClO2 fail to cause significant cell lysis, while cell settleability can be improved markedly by using only ClO2. Preoxidation with ClO2 is more effective in destabilizing the particles and algae when applying Alum coagulation at low dosages. It was found that the residual algae counts in the supernatants are inversely well-correlated to its filterability instead of its residual turbidity. The reduced cell integrity resulting from ClO2 preoxidation effectively improves the performance of coagulation-sedimentation for algae (diatoms) removal and reduces the burden of filtration operation in the WTPs. (C) 2015 Elsevier B.V. All rights reserved.
Effect of coagulation mechanism on membrane permeability in coagulation-assisted microfiltration for spent filter backwash water recycling
(2011-03-20)
Huang, Chihpin
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Lin, Jr-Lin
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Lee, Wen-Shan
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Pan, Jill R.
;
Zhao, Bingqing
Coagulation is an effective pre-treatment process in membrane filtration for recycling spent filter backwash water (SFBW). To optimize the operation of the coagulation/filtration process for SFBW recycling, it is important to understand the critical role of coagulation mechanism on membrane filtration. In this study, SFBW samples were coagulated with polyaluminum chloride (PACI), followed by a dead-end micro-filtration (MF), and the mean permeate flux and permeate quality were determined. The results showed that pre-coagulation improved the flux decline and the degree of the improvement was closely related to coagulation mechanisms. The permeate flux was enhanced most effectively by precipitation charge neutralization (PCN) coagulation, followed by charge neutralization and then sweep flocculation. Close examination of cake properties indicated that the reduced cake resistance (R(c)) was subjected to the coagulated SFBW flocs in response to different coagulation mechanism. Smaller flocs, induced by PCN, were more compact and stronger, forming less compressible cake, which facilitated membrane filtration, while slower membrane filtration was observed when more compressible cake formed from larger flocs of looser and weaker structure. Coagulation mechanism also governed the size distribution of SFBW floc, which is strongly related to the subsequent cake compressibility as well as membrane permeability in membrane filtration. (C) 2011 Elsevier B.V. All rights reserved.
Enhanced particle destabilization and aggregation by flash-mixing coagulation for drinking water treatment
(2013-08-30)
Lin, Jr-Lin
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Pan, Jill R.
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Huang, Chihpin
;
環境工程研究所
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生物科技學系
In water treatment plants (WTPs), the operation of rapid mixing in coagulation units dominates particle destabilization and the formation of flocs. The goal of this study was to investigate the effect of enhanced rapid-mixing intensity (velocity gradient [G]) on the performance of coagulation for natural turbid water treatment. Two surface-water samples of low and high turbidity were coagulated by using polyaluminum chloride (PACl), with G values ranging from 200 to 800 s(-1),and the destabilization of particles and dissolved organic matter (DOM) was determined, followed by measurement of filterability of the supernatant. Furthermore, the effect of high rapid mixing on the coagulation efficiency was studied by using a pilot-scale, in-line instantaneous flash mixer (IFM) which could generate much higher G than a conventional mechanical mixing of WTP. The results of Jar test showed that the enhanced reduction in turbidity was accompanied by the improved filterability of the supernatant, which was due to the formation of larger flocs with strong structure in response to higher rapid-mixing intensity, especially for low-turbidity water. It was found that the fractal dimension (D-f) of coagulated flocs is inversely proportional to the recovery factor of broken flocs. The in-line IFM with intensive mixing (G > 5000 s(-1)) substantially improved the removal of particles and DOM, as a result of the formation of large flocs. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.
Fate of hydrolyzed Al species in humic acid coagulation
(2014-06-01)
Lin, Jr-Lin
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Huang, Chihpin
;
Dempsey, Brian
;
Hu, Jing-Yi
;
環境工程研究所
The hydrolysis of Al-based coagulants in acidic conditions is necessary for the removal of organic matter by the coagulation/sedimentation process. However, interactions between hydrolyzed Al species and organic matter are complicated and this makes it difficult to optimize coagulant dosing for organics removal. The goal of this study was to investigate the reactions of hydrolyzed Al species in the coagulation of organic matter. Two polyaluminum chloride (PACl) coagulants, a commercial product with sulfate (PACl-C) and lab-prepared material (PACl-Al-13) containing 7% and 96% of total Al as Al-13, respectively, have been applied to investigate the coagulation of humic acid (HA). At pH 6, a lower dosage of PACl-Al-13 than of PACl-C was required for optimized HA removal through coagulation/sedimentation due to the strong complexation and charge neutralization by Al-13. Observation of the coagulation process using wet scanning electron microscopy showed that PACl-C produced both clustered flocs and linear precipitates in the presence of sulfate while PACl-Al-13 produced curled precipitates due to the formation of intermolecular complex, when both coagulants were added at the optimum doses. Investigation of Al HA floc by Al-27-NMR and Al 2p XPS suggested that monomeric Al (Al-m) was hydrolyzed into Al(OH)(3) with tetrahedron for PACl-C coagulation while a half of Al-13 slowly decomposed into octahedral Al-HA precipitates for PACl-Al-13 coagulation. Meanwhile, C ls XPS indicated that aromatic C=C of HA was preferentially removed from solution to Al HA flocs for both PACl-C and PACl-Al-13 coagulation. It was concluded that Al HA complexation strongly affects the reaction pathways for Al hydrolysis and the final nature of the precipitates during PAC coagulation of HA and that the hydrolysis products are also strongly affected by the characteristics of the PAC coagulant. (C) 2014 Elsevier Ltd. All rights reserved.
Fouling mitigation of a dead-end microfiltration by mixing-enhanced preoxidation for Fe and Mn removal from groundwater
(2013-02-20)
Lin, Jr-Lin
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Huang, Chihpin
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Ruhsing, Pan Jill
;
Wang, Yau-Shian
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環境工程研究所
A combination of oxidation and microfiltration (oxidation-MF) is commonly used to remove Fe and Mn from groundwater. The characteristics of Fe and Mn oxides formed by oxidation can be significantly affected by the mixing intensity during oxidation, which subsequently influences the performance of membrane filtration. To optimize oxidation-MF, the critical role of mixing intensity on Fe and Mn oxide formation was investigated. Sufficient oxidant (NaOCl) was added to a prepared ferrous solution with or without Mn ions to oxidize the ions at different mixing intensities, followed by a dead-end MF for 30 min at a constant transmembrane pressure of 1 kg/cm(2). A custom-made module surrounded by a tube membrane was used in microfiltration. The resistance of membrane filtration was calculated by a resistance-in-series model. Cake resistance (R-c) dominated the fouling of the membrane, which depended on the composition of oxides. Oxides formed at high mixing intensity were smaller and more compact, which resulted in reduced R-c, and increased permeate flux. The presence of oxidized Mn aggravated membrane fouling. Permeate flux declined rapidly as a result of the cake formed by Fe-Mn oxides with increased hydrophobicity. The irreversible fouling of the dead-end MF was insensitive to mixing intensity during prechlorination, while the irreversible fouling induced by Fe-Mn oxides was more severe than that by Fe oxides as membrane filtration cycle progressed. The results show that membrane flux of a dead-MF can be effectively improved by prechlorination with enhanced mixing due to the formation of a permeable cake layer with low cake compressibility in the membrane filtration. (c) 2012 Elsevier B.V. All rights reserved.
Optical properties of algogenic organic matter within the growth period of Chlorella sp and predicting their disinfection by-product formation
(2018-04-15)
Hua, Lap-Cuong
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Lin, Jr-Lin
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Syue, Ming-Yang
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Huang, Chihpin
;
Chen, Pei-Chung
Algogenic organic matter (AOM) in eutrophic waters is a well-known precursor to disinfection by-product (DBP) formation in drinking water. This purpose of this study is (i) to characterize the optical properties of AOM origins, including intra- (IOM) and extra-cellular organic matter (EOM), derived from Chlorella sp. growth as precursors to two major carbonaceous DBPs (C-DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs) and (ii) to correlate these optical properties with THM and HAA formation potential (FP) in order to predict DBP formation. The results show that both EOM and IOM had low UV254 and UV280 absorbance during their entire growth phase. While IOM chiefly comprised of aromatic proteins and soluble microbial products-like substances (80% of average fluorescent intensity-AFI), EOM spectra were rich in humic- and fulvic-like substances (60% AFI). However, its chemical nature likely differed from terrestrial humics. In DBPFP tests, IOM was a higher-yielding precursor of THMs and HAAs compared to EOM, regardless its growth status. Consequently, C-DBPFP of IOM was always higher than EOM during four growth phases. Results from DBP tests also showed insignificant variation of EOM-derived THMFP and HAAFP during the algal growth phase, while the algal growth status strongly influenced the yields of IOM-derived THMFP and HAAFP. From correlation analysis, our results showed no correlation between UV absorbance with THMFP and HAAFP. Conversely, the regional AFI showed a good correlation with HAAFP and C-DBPFP. Predicting models based on AFI for the formation of HAAs and C-DBPs consequently yielded great predictability for laboratory AOM-containing water samples, with a coefficient of determination R-2 = 0.879, p < 0.01 and R-2 = 0.846, p < 0.01. This study indicates a promising application of fluorescent spectra for predicting DBPs derived from algae-rich water sources. (c) 2017 Elsevier B.V. All rights reserved.
Probing algogenic organic matter (AOM) by size-exclusion chromatography to predict AOM-derived disinfection by-product formation
(2018-12-15)
Hua, Lap-Cuong
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Lin, Jr-Lin
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Chao, Shu-Ju
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Huang, Chihpin
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環境工程研究所
High-performance size exclusion chromatography (HPSEC) coupled with peak-fitting technique was used to probe molecular weight (MW) properties of algogenic organic matter (AOM). The qualitative and quantitative MW information derived was used to predict AOM-derived disinfection by-product (DBP) formation. We resolved overlapping HPSEC chromatograms of all AOM samples into six major peaks with R-2 > 0.996. This study gave significant insight into the HPSEC profiles of AOM, in which resolved peaks A and B (biopolymers) and peak C (humic substances) showed a strong correlation with the formation of carbonaceous-DBPs (C-DBPs). This likely resulted from the abundance of aromatic structures and conjugated C=C double bonds in their chemical nature. Our results also indicated the importance of algal cells, including intra-cellular and cell-bound organic matter, over extra-cellular organic matter as precursors to C-DBP formation. The application of the information extracted from HPSEC profiles associated with the fluorescent components of AOM showed great improvements in the predictability of THMs, HAAs, and C-DBPs with R-2 > 0.7 and p < 0.05. The outcome of this study will significantly benefit effective control of AOM-derived DBP formation by the chlorination of eutrophic waters. (C) 2018 Elsevier B.V. All rights reserved.
Recycling of spent filter backwash water using coagulation-assisted membrane filtration: effects of submicrometre particles on membrane flux
(2010)
Huang, Chihpin
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Lin, Jr-Lin
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Wu, C. L.
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Chu, C. P.
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環境工程研究所
Membrane separation technology has been widely used for recycling of spent filter backwash water (SFBW) in water treatment plant. Membrane filtration performance is subject to characteristics of the particles in the SFBW. A bench-scale microfiltration (MF) coupled with pre-coagulation was set up to evaluate the recovery efficiency of SFBW. Effect of particle size distribution and zeta potential of the coagulated SFBW on the membrane filtration as well as the coagulation strategies were investigated. Pore clogging was more severe on the membrane with 1.0 mu m pore size than on the membrane with 0.5 mu m pore size due to the fact that submicrometre particles are dominant and their diameters are exactly closed to the pore size of the MF membrane. Pre-settling induced more severe irreversible fouling because only the submicrometre particles in the water become predominant after settling, resulting in the occurrence of more acute pore blocking of membrane. By contrast, pre-coagulation mitigates membrane fouling and improves membrane flux via enlarging particle size on membrane surface. The variations of zeta potential in response to coagulant dosing as well as fractal dimension were also compared with the performance of the subsequent filtration. The result showed that pre-coagulation induced by charge neutralization at the optimum dosage where the zeta potential is around zero leads to the optimal performance of the subsequent membrane filtration for SFBW recycling. At such condition, the fractal dimension of coagulated flocs reached minimum.
Role of Al speciation on humic acid coagulation
(2008-01-01)
Huang, Chihpin
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Lin, Jr-Lin
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Hu, Jinyi
;
交大名義發表
;
National Chiao Tung University
Role of Al speciation on humic acid coagulation
(2008-01-01)
Huang, Chihpin
;
Lin, Jr-Lin
;
Hu, Jinyi
;
環境工程研究所
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Institute of Environmental Engineering
The origin of Al(OH)(3)-rich and Al(13)-aggregate flocs composition in PACl coagulation
(2009-09-01)
Lin, Jr-Lin
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Huang, Chihpin
;
Chin, Ching-Ju M.
;
Pan, Jill R.
;
環境工程研究所
The composition of hydrolyzed Al species is essential for the understanding of coagulation with Al-based coagulants. Surface characteristics of flocs formed by coagulation with two distinct polyaluminum chloride (PACl) coagulants were identified. One commercial coagulant (PACl-C) with voluminous monomeric Al and colloidal Al(OH)(3) and a custom-made PACl (PACl-Al(13)) containing high Al(13) content were applied to destabilize kaolin particles. The flocs formed by PACl-C and PACl-Al(13) at neutral and alkaline pH ranges, respectively, were observed by FE-SEM and HR-TEM. In addition, the Al composition of these flocs was characterized by XPS and HR-XRD, and the imaging of Al(OH)(3) precipitates and Al(13) aggregates were conducted by SEM as well as tapping mode AFM in liquid system. The observations of flocs indicate that the morphology of Al(OH)(3)-rich flocs are fluffy and porous around the edge of flocs, while the Al(13)-aggregate flocs have a glossy contour and irregular structure. Both Al(OH)(3)-rich and Al(13)-aggregate flocs do not possess well-formed crystalline structure except for the Al(13)-like crystal exists in the Al(13)-aggregate flocs. Among Al(OH)(3) precipitates, colloidal Al(OH)(3) is micro-scale in size, while amorphous Al(OH)(3) is nano-scale. During the formation of Al(13) aggregates, some coiled and clustered Al(13) aggregates with smoother surface were observed. The XPS study on floc surface showed that tetrahedral (Al(IV))/octahedral (Al(VI)) Al ratio on the surfaces of PACl-C and PACl-Al(13) flocs is 1:1.6 and 1:9.9, respectively. Of the in situ formed Al(13), almost half of Al-hydroxide precipitates on the surface of Al(OH)(3)-rich flocs possess the Al(IV) center. It also found that the irregularly aggregated Al(13) with a similar Al(13) Crystalline structure subsists on the surface of Al(13)-aggregate flocs. (C) 2009 Elsevier Ltd. All rights reserved.
The origin of Al(OH)(3)-rich and Al-13-aggregate flocs composition in PACl coagulation
(2009-09-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Chin, Ching-Ju M.
;
Pan, Jill R.
;
環境工程研究所
The composition of hydrolyzed Al species is essential for the understanding of coagulation with Al-based coagulants. Surface characteristics of flocs formed by coagulation with two distinct polyaluminum chloride (PACl) coagulants were identified. One commercial coagulant (PACl-C) with voluminous monomeric Al and colloidal Al(OH)(3) and a custom-made PACl (PACl-Al-13) containing high Al-13 content were applied to destabilize kaolin particles. The flocs formed by PACl-C and PACl-Al-13 at neutral and alkaline pH ranges, respectively, were observed by FE-SEM and HR-TEM. In addition, the Al composition of these flocs was characterized by XPS and HR-XRD, and the imaging of Al(OH)(3) precipitates and Al-13 aggregates were conducted by SEM as well as tapping mode AFM in liquid system. The observations of flocs indicate that the morphology of Al(OH)(3)-rich flocs are fluffy and porous around the edge of flocs, while the Al-13-aggregate flocs have a glossy contour and irregular structure. Both Al(OH)(3)-rich and Al-13-aggregate flocs do not possess well-formed crystalline structure except for the Al-13-like crystal exists in the Al-13-aggregate flocs. Among Al(OH)(3) precipitates, colloidal Al(OH)(3) is micro-scale in size, while amorphous Al(OH)(3) is nano-scale. During the formation of Al-13 aggregates, some coiled and clustered Al-13 aggregates with smoother surface were observed. The XPS study on floc surface showed that tetrahedral (Al-IV)/octahedral (Al-VI) Al ratio on the surfaces of PACl-C and PACl-Al-13 flocs is 1:1.6 and 1:9.9, respectively. Of the in situ formed Al-13, almost half of Al-hydroxide precipitates on the surface of Al(OH)(3)-rich flocs possess the Al-IV center. It also found that the irregularly aggregated Al-13 with a similar Al-13 Crystalline structure subsists on the surface of Al-13-aggregate flocs. (C) 2009 Elsevier Ltd. All rights reserved.
Visualization and quantification of transparent exopolymer particles (TEP) in freshwater using an auto-imaging approach
(2017-07-01)
Nguyen Thi Thuy
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Huang, Chih-Pin
;
Lin, Jr-Lin
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環境工程研究所
;
Institute of Environmental Engineering
Most water sources are full of microscopic transparent exopolymer particles (TEP), which are currently regarded as a major initiator of biofilm formation. This study developed and applied an auto-imaging FlowCAM-based method for online observation and quantification of TEP in freshwater. Samples from reservoirs in Taiwan with a wide range of water quality were directly used to develop this methodology. Factors that potentially affect the measurement were tested. The results showed that characteristics of the particles measured instantaneously after staining samples with Alcian blue differed significantly from those measured at steady states, as a result of particle aggregation. Compared to traditional microscopic methods, this proposed method provides a simple, rapid, and less labor-intensive analysis with particle morphological conservation and a large number of particle attributes. By overcoming the limitations from the former, this technique would offer routine monitoring of these transparent particles from various freshwater sources and feed water in membrane filtration, hence facilitating the use of TEP as a critical parameter for biofouling investigation in water treatment. Application of the method for Taiwan reservoirs showed a wide variety of morphological forms of TEP and its abundance, up to 25,000 ppm.