Browsing by Author "Hua, Lap-Cuong"

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Algogenic organic matter derived DBPs: Precursor characterization, formation, and future perspectives - A review
(2019-10-02)
Hua, Lap-Cuong
;
Lai, Chun-Hsi
;
Wang, Gen-Shuh
;
Lin, Tsair-Fuh
;
Huang, Chihpin
Algogenic organic matter (AOM) in water is a critical issue for sustainable treatment of drinking water, especially when algal eutrophication occurs because it is not amenable to removal by traditional coagulation/sedimentation/filtration processes. AOM is thus proved as a major precursor of disinfection by-products (DBPs). Its occurrence in water is undesirable and impacts the safety of drinking water. This review paper aims to broaden our current knowledge on the formation of AOM-derived DBPs and its precursor characterization. The future perspectives of research needs on AOM-DBP precursor characterization for an effective prediction are also given by this review. AOMs from various algal species have high-yielding potentials to produce both carbonaceous and nitrogenous DBPs upon chlorination, especially for the intracellular OM (IOM) from the algal cell. The practical treatment of eutrophic water with preoxidation thus should be used in caution to avoid the release of IOM from ruptured cells. Characterization of the physiochemical properties, such as basic parameters, optical properties, molecular weight distribution, and chemical functional groups, of AOM can give advantages for the better understanding of AOM-derived DBPs. Among the characterization tools, the fluorescent technique is highly recommended for the application of AOM-DBP prediction.
Characteristics of low and high SUVA precursors: Relationships among molecular weight, fluorescence, and chemical composition with DBP formation
(2020-07-20)
Hua, Lap-Cuong
;
Chao, Shu-Ju
;
Huang, Kochin
;
Huang, Chihpin
;
環境工程研究所
Disinfection by-products (DBPs) formed upon water treatment is an emerging issue worldwide. While monitoring of DBP precursors can easily be achieved for high specific UV absorbance (SUVA) organic (>6 L/mg.m), low and extremely low SUVA precursors (<2 L/mg.m) are difficult to monitor or even to predict their DBP formation behaviour. This study investigated the relationships among NOM characteristics, such as molecular weight (MW), fluorescence, and chemical composition, with DBP formation resulting from the chlorination of relatively high and low SUVA precursors. High SUVA precursors were formed by C-rich substances (82-85% of total mass) corresponding with high C/N and C/O (>100 and >5, respectively). Such precursors exhibited the fluorescence of long-wavelength humic-like signal and occurred at a high MW range (>30 kDa). By contrast, low SUVA precursors were either N-rich and/or O-rich substances, associated with much lower carbon content (40-70%). Low SUVA, N-rich precursors particularly also occurred at a high MW region (>100 kDa) and produced a strong protein-like fluorescence signal. When SUVA values of O-rich precursors were extremely low (<1 L/mg.m) they were accompanyied by short-wavelength humic-like fluorescence. During DBP tests, high SUVA produced only high yields of carbonaceous DBPs (e.g trichloromethane, haloacetic acids, haloketones), whereas low SUVA Nrich precursors yielded high levels of both C and NDBPs (e.g. haloacetonenitrile, chloropicrin). By contrast, extremely low SUVA precursors produced significantly lowlevels of both C and NDBPs (total <30 mu g/mgC). Furthermore, 19 of 20 regression models of DBP formation using log-transformed MW gave R-2 = 0.50-0.97. The strong regressions and correlations of NOM characteristics with DBPs in this study provide a better understanding of the influence of precursors characteristics on DBP monitoring, especially for low SUVA NOM. (C) 2020 Elsevier B.V. All rights reserved.
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.
Effects of electro-coagulation on fouling mitigation and sludge characteristics in a coagulation-assisted membrane bioreactor
(2015-12-01)
Hua, Lap-Cuong
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Huang, Chihpin
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Su, Yu-Chun
;
Tran-Ngoc-Phu Nguyen
;
Chen, Pei-Chung
Although much research effort has focused on methods to mitigate fouling of membrane bioreactors (MBRs), fouling is still inevitable. This paper aims to corroborate the roles of electro-coagulation approach within a coagulation-assisted MBR, termed electro-MBR. The effects of electro-coagulation on sludge characteristics and fouling behavior were investigated. A batch-scale experiment was carried out to identify an optimum electric current condition for electro-MBR study, in which the electro-MBR and a traditional MBR were identically set for numerous comparisons. The average fouling rate was substantially reduced 7.8 fold resulting in no chemical cleaning requirements during the entire operation of the electro-MBR. Enhanced sludge compressibility and controlled growth of filamentous bacteria positively affected by electro-coagulation were also obtained in the electro-MBR. This paper suggests that fouling mitigation in electro-MBR can be attributed to two mechanisms; (i) charge neutralization and adsorption for soluble foulants; (ii) electro-chemical oxidation for bound foulants. Furthermore, we conclude that electro-coagulation can simultaneously alter morphology and microbial structure of sludge flocs to become more compressible with lower fouling tendency, which would be beneficial for the mitigation of membrane fouling in electro-MBR. (C) 2015 Elsevier B.V. All rights reserved.
Fluorescent and molecular weight dependence of THM and HAA formation from intracellular algogenic organic matter (IOM)
(2019-01-01)
Hua, Lap-Cuong
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Chao, Shu-Ju
;
Huang, Chihpin
;
環境工程研究所
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Institute of Environmental Engineering
This study (i) examined the formation of two major carbonaceous disinfection by-products (C-DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), during the chlorination of intracellular algogenic organic matter (IOM) extracted from two commonly blooming algae M. aerugittosa (MA) and Chlorella sp. (CH), and (ii) investigated the roles and relationships of fluorescent and molecular weight (MW) properties on/with IOM-derived THMs and HAAs. The extracted IOM samples were separated into different MW fractions by centrifugal devices with membrane support with MW cut-offs of 100, 30, 10, 3, and 1 kDa. We observed an overall reduction of C-DBPs with a decrease of IOM-MW from >100 kDa to <1 kDa. Of six fractionated IOM, a large fraction (>100 kDa) contributed the largest amount to the MW distribution of IOM, accounting for 33 and 42% of the total dissolved organic carbon (DOC) of MA and CH, respectively. It also had the highest-yielding potential to produce significant levels of THMs and HAM, and total C-DBPs over other small MW fractions. Although small MW fractions (>10 kDa) contributed around 50% of the total DOC, they made an insignificant contribution (>20%) to the THMs, HAM, and overall C-DBPs. Furthermore, the decrease of IOM MW caused a shift from the domination of HAA formation to THM formation, especially when MW was <10 kDa. By canonical correspondent analysis, the relationship of IOM-derived THMs and HAAs with IOM properties was examined. In particular, large fractions of IOM, exhibiting aromatic protein- (AP) and soluble microbial product- (SMP) like fluorescence, are favorable for the formation of HAAs, whereas small MW fractions of IOM with HA- and FA-like fluorescence preferentially tends to form THMs. Our findings evidently show the strong dependence of IOM-derived THMs and HAAs on the fluorescent and MW properties. Therefore, the characterization of MW and fluorescent properties can provide the advantages in the control of algae-derived DBPs upon the chlorination of eutrophic water. (C) 2018 Elsevier Ltd. All rights reserved.
Novel Chlorination Byproducts of Tryptophan: Initial High-Yield Transformation Products versus Small Molecule Disinfection Byproducts
(2020-03-01)
Hua, Lap-Cuong
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Kim, Euna
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McCurry, Daniel L.
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Huang, Chihpin
;
Mitch, William A.
Because of the difficulty of carbon-carbon bond cleavage needed to liberate the small molecule chlorine disinfection byproducts (DBPs; e.g., trihalomethanes), they typically form at <1% yields. By using N-acetyl-tryptophan (NacTrp) as a model reactive peptide-bound monomer within natural organic matter (NOM), this study illustrates the characterization of its initial chlorine transformation products as an alternative approach to identify high-yield DBPs. When NacTrp was treated at 1-10 chlorine/NacTrp molar ratios, seven novel initial transformation products were purified and characterized by high-resolution mass spectrometry, including two chlorine-containing DBPs. The total concentrations of these novel DBPs accounted for 55-100% conversion of the parent NacTrp at 1-5 chlorine/NacTrp molar ratios over 24 h, compared to <= 5% for the total concentrations of small molecule DBPs. At a 10:1 molar ratio, the novel DBP concentrations declined over 24 h to account for 25% molar conversion, while small molecule DBP concentrations increased, yet still accounted for only 20% molar conversion. A reaction pathway consistent with these initial transformation products was proposed. The high yields of these novel DBPs are attributable to the lack of carbon-carbon bond cleavage. This study illustrates the identification of initial transformation products of important monomers as an efficient option to characterize the unknown DBPs.
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
;
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.
Pretreatment of algae-laden and manganese-containing waters by oxidation-assisted coagulation: Effects of oxidation on algal cell viability and manganese precipitation
(2016-02-01)
Lin, Jr -Lin
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Hua, Lap-Cuong
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Wu, Yuting
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Huang, Chihpin
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環境工程研究所
Preoxidation is manipulated to improve performance of algae and soluble manganese (Mn) removal by coagulation-sedimentation for water treatment plants (WTPs) when large amount of soluble Mn presents in algae-laden waters. This study aimed to investigate the effects of preoxidation on the performance of coagulation-sedimentation for the simultaneous removal of algae and soluble Mn, including ionic and complexed Mn. NaOCI, ClO2, and KMnO4 were used to pretreat such algae-laden and Mn containing waters. The variation of algal cell viability, residual cell counts, and concentrations of Mn species prior to and after coagulation-sedimentation step were investigated. Results show that NaOCl dosing was effective in reducing the viability of algae, but precipitated little Mn. ClO2 dosing had a strongest ability to lower algae viability and oxidize ionic and complexed soluble Mn, where KMnO4 dosing oxidized ionic and complexed Mn instead of reducing the viability of cells. Preoxidation by NaOCl only improved the algae removal by sedimentation, whereas most of soluble Mn still remained. On the other hand, ClO2 preoxidation substantially improved the performance of coagulation-sedimentation for simultaneous removal of algae and soluble Mn. Furthermore, KMnO4 preoxidation did improve the removal of algae by sedimentation, but left significant residual Mn in the supernatant. Images from FIowCAM showed changes in aspect ratio (AR) and transparency of algae-Mn flocs during oxidation assisted coagulation, and indicates that an effective oxidation can improve the removal of most compact algae-Mn flocs by sedimentation. It suggests that an effective preoxidation for reducing algal cell viability and the concentration of soluble Mn is a crucial step for upgrading the performance of coagulation-sedimentation. (C) 2015 Elsevier Ltd. 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
;
Lin, Jr-Lin
;
Chao, Shu-Ju
;
Huang, Chihpin
;
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.