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Optimization and performance evaluation of the continuous algal toxicity test
(1997-07-01)
Chen, CY
;
Lin, KC
;
環境工程研究所
;
Institute of Environmental Engineering
Responses of Selenastrum capricornutum to cadmium in a chemostat are evaluated under various test conditions defined by the nitrogen to phosphorus ratio, phosphate strength, dilution rate, and ethylenediaminetetraacetic acid content. Based on the test results, these parameters were optimized to achieve superior test sensitivity. This continuous system was also modified to allow testing on a weekly basis. The performance of the modified testing technique was evaluated, employing six different metal toxicants. Compared with batch test results reported by other researchers and our own experiment, the continuous test achieved superior sensitivities and reproducibility. The test method presented in this study is believed to be an ideal technique both for research and regulatory purposes.
寶山原水含高藻及鐵、錳淨水處理操作最適化之研究
(2012)
袁如馨
;
Jill Ruhsing Pan
;
國立交通大學工學院防災工程研究中心
寶山淨水場原水主要來自寶山水庫及寶山第二水庫，夏季時水庫常有大量藻類滋生，且在枯水期時原水中鐵、錳含量突增，甚至超過飲用水水源水質標準，此時寶山場淨水前處理加藥操作如前氧化及混凝加藥控制不易，致使後續沉澱池效能不彰及過濾池嚴重堵塞、反沖洗頻率增加及水質惡化等問題發生，甚至發生紅水事件，延宕正常供水作業，無法即時滿足工業園區及民生用水需求。本研究計畫擬每個月針對寶山給水廠、寶山及寶山第二水庫原水進行原水調配比例調查、例行性水質及物化特性分析，並調查各淨水單元之藻種及藻數，以確認影響淨水操作之問題藻種。另外，分析原水中鐵及錳之濃度及型態，以探討原水調配方式及廢水迴流操作對原水鐵及錳濃度變化之影響，以了解原水鐵及錳濃度突增之原因。於研究期間，本研究團隊將評估寶山場含藻及鐵、錳原水經不同前氧化劑(次氯酸鈉及高錳酸鉀)搭配不同混凝劑(硫酸鋁及聚矽酸鐵)混沉處理之最適加藥模式，最後，提出寶山場因應含藻及鐵、錳原水問題之最適淨水操作策略及原水調配對策。
Collision efficiencies of algae and kaolin in depth filter: The effect of surface properties of particles
(1999-04-01)
Huang, CP
;
Pan, JRS
;
Huang, SH
;
環境工程研究所
;
Institute of Environmental Engineering
Column filtration experiments with 2 mm-Phi glass beads were conducted to investigate the behavior of colloids during filtration. Algae and kaolin were used as model particles, while the chemical system was altered by changing the electrolyte concentration and pH. The collision efficiencies from the interaction between colloids and the filter medium were calculated with a semi-empirical approach of the single sphere model and clean-bed filtration theory. The experimental results indicate that ionic strength enhance the removal efficiencies for both algae and kaolin particles significantly. The removal efficiency of the filter for algae decreased with the increase in pH for up to pH 6. No significant change was observed beyond pH 6. Removal efficiencies for kaolin decreased with an increase in pH. It is concluded that collision efficiencies are sensitive to ion strength and pH. (C) 1999 Elsevier Science Ltd. All rights reserved.
Dewatering characteristics of algae-containing alum sludge
(1999-05-01)
Pan, JR
;
Huang, CP
;
Chuang, YC
;
Wu, CC
;
環境工程研究所
The presence of algae in source waters not only causes problems in the water treatment process, but also complicates the treatment and disposal of sludge. This has become a major concern in Taiwan because of the increasing eutrophication of water sources. The purpose of this study was to determine the effects of algae during aging process on the characteristics of potable water treatment residuals and investigate their conditioning in order to provide water treatment plants with guidelines for treating algae-containing sludge. In this study, we measured the bound water content and CST to evaluate the influence of algae and their exudates on sludge conditioning. The change in zeta potential was monitored during sludge aging. During the aging process up to 5 days, the surface charge of sludge became more negative and the dewaterability was enhanced by algal exudates. Microphotographs of the algae-containing sludge suggest that algae and their exudates cause the bio-flocculation phenomenon. (C) 1999 Elsevier Science B.V. All rights reserved.
Effects of inoculum's mean cell volume on algal toxicity tests
(2000)
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
The aim of the present study is to compare the effects of the mean cell volume (MCV) of algal inoculum to the sensitivity and reproducibility of the toxicity test. Two sets of experiments were conducted using inoculums with the MCV equal to 60 mum(3)/cell and 40 mum(3)/cell, respectively. The initial cell densities, however, were kept the same at 10,000 cells/ml. The results show that larger MCV of the inoculum results in greater EC50 values. Similar observations and conclusions were obtained from comparisons based on NOEC values. Thus, MCV of the inoculum significantly influences the observed toxic response in terms of EC50 and NOEC values. It is also evident that, there is a significant increase in the test variability if the MCV is not controlled properly. This study reports that standardizing the initial mean cell volume of algal culture can improve inter-laboratory and intra-laboratory precision. Furthermore, replacing the EC50 values by the calculated exposure values (EE50) can reduce the variability in data due to differences in the MCV of the inoculum.
Statistical comparisons of the no-observed-effect concentration and the effective concentration at 10% inhibition (EC10) in algal toxicity tests
(2001)
Shieh, JN
;
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
Batch-type algal toxicity tests were conducted to evaluate the low toxic effects of metal toxicants. Both the no-observed-effect concentration (NOEC) and the effective concentration at 10% inhibition (EC10) were calculated and compared. The results of this study indicate that, for algal toxicity tests, NOEC. offers better protection to the test organisms than EC10. In addition, the consistency of NOEC is found to depend on the response endpoints measured. A cut-off-value approach is proposed to determine whether NOEC or EC10 should be chosen for estimating low toxic effects. For a specific toxicity test, the average cut-off value directly indicates the magnitude of the square root of the within-group-variance. A precise test associated with small within-group-variances also produces relatively small average cut-off value (say, less than 10% of the growth reduction). This average value provides useful information on the minimum protection that can be offered by the NOEC.
Discrepancies between different response parameters in batch and continuous algal toxicity tests
(2001-03-30)
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
The test sensitivities and reproducibilities based on different response endpoints (cell density and total cell volume) were compared using both bath and continuous algal toxicity tests. Parameters related to algal cell density are found to be more sensitive and reproducible than total cell volume which bears a direct correlation to algal biomass or dry weight. The magnitude of differences in the median effective concentration values could be upto six folds. The main cause for the above discrepancies is because the cell density and total cell volume are two response endpoints reflecting the degree of inhibition on the binary fission mechanism and overall photosynthesis, respectively. At low toxicant concentrations, the inhibitory effect is primarily on the cell division rather than on the cellular photosynthesis. Thus, more severe toxic effects are expected to be observed based on the cell density than the total cell volume. The results of this study clearly demonstrate that sensitivity and reproducibility can be significantly improved if response parameters are calculated based on the cell density. Traditionally, cell density data are often converted into biomass before assessing the effects of toxicants. This procedure may not be necessary and may reduce the test sensitivity. (C) 2001 Elsevier Science B.V. All rights reserved.
Toxicity of nitriles and their derivatives on Raphidocelis subcapitata (Algae)
(2005)
Huang, Chun-Pin
;
Chen, Chung-Yuan
;
環境工程研究所
;
Institute of Environmental Engineering
Algae are ecologically important organisms in the aquatic food chain and are frequently used in environmental studies for assessing the relative toxicity of various chemicals and/or waste discharges. Currently, however, most standard algal test protocols are based on conventional batch technique (ASTM, 1994; ISO, 1987; US EPA, 1996; OECD; 1984). The European Centre for Ecotoxicology and Toxicology of Chemicals (1996) has concluded that current algal toxicity test protocols are unsuitable for assessing the effects of volatile compounds because the experimental design for these methods may cause considerable losses of volatile organic toxicants and, consequently, underestimations of the toxicity of volatile organic chemicals. Nitriles and their derivatives are common intermediate products from plastic and resin manufactories. Their toxic effects to phytoplankton have rarely been investigated. This study evaluated the toxicity of 12 kinds of nitriles and halogen-substituted nitriles using a closed-system algal toxicity test with no head-space. Raphidocelis subcapitata was selected as the test alga. Toxicity testing was conducted by transferring adequate amounts of algal suspension, dilution water (with growth medium), and toxicants into 300-ml BOD bottles. The BOD bottles were completely filled up with no head-space left. The initial cell density and the exposure time were 15,000 cells/mL and 48 hours, respectively. Light intensity and temperature were kept at 65 mu EM(-2)s(-1) (+/- 10%) and 24 +/- 1 square. The DO level at the beginning of the test was approximately 1 to 3 mg/L. Two response endpoints, i.e., dissolved oxygen production and algal growth rate, were employed to assess the toxicity of the test chemicals. The median effective concentration (EC50) was defined as the toxicant concentration that resulted in 50% reduction with respect to the response endpoints (i.e., ADO, or growth rate). The median effective concentrations (EC50) range from 0.051 to 5843 mg/L. In general, the DO endpoint revealed higher inhibition than that from algal growth rate. The above phenomenon indicates that certain nitrils and their derivatives have stronger toxic effects to algal photosynthesis reactions. Furthermore, halogen-substituted nitriles were found to be extremely toxic to Raphidocefis subcapitata. With increasing numbers of the halogen molecules, stronger toxicity was observed. The bromine substitutent also seems to be more toxic than chlorine substitutent. Quantitative structure-activity relationships (QSARs) were established based on the chemicals'ELUMO values with R 2 values equal to 0.85. Such relationships can thus be used to predict the toxicity of other nitrile compounds.
A novel algal toxicity testing technique for assessing the toxicity of both metallic and organic toxicants
(2005-05-01)
Lin, JH
;
Kao, WC
;
Tsai, KP
;
Chen, CY
;
環境工程研究所
This study presents a closed-system algal toxicity test technique that is capable of detecting the effects of both organic and metallic toxicants. Toxicity testing was conducted by transferring adequate amounts of algal suspension, dilution water (with culture growth medium), and toxicants into 300-mL BOD bottles. The BOD bottles were completely filled up with no head-space left. The initial cell density and the exposure time were 15,000 cells/mL and 48 h, respectively. The performance of the above test method was evaluated using three heavy metals and six organic toxicants based on three different test endpoints, i.e., dissolved oxygen production, algal growth rate, and cell density. The proposed test revealed excellent test sensitivity and reproducibility. Currently, none of the existing algal toxicity test protocols is adequate for assessing the toxicity of organic chemicals. The closed-system algal toxicity tests developed by previous researchers also may not be ideal because the enlarged headspace and/or enriched bicarbonate buffer may result in either underestimations of the exposure concentrations or insensitive responses to both heavy metals and organic toxicants. Compared to the aforementioned algal toxicity test methods, the proposed technique in the present study has a more general applicability under conditions such as effluent samples containing both metals and organic toxicants or samples with unknown compositions. (c) 2005 Elsevier Ltd. All rights reserved.
Individual and combined toxicity of nitriles and aldehydes to Raphidocelis subcapitata
(2005-05-01)
Chen, CY
;
Chen, SL
;
Christensen, ER
;
環境工程研究所
;
Institute of Environmental Engineering
A closed- system algal toxicity test with no headspace was applied to evaluate the toxicity of I I aldehydes and two nitrites to Raphidocelis subcapitata. Algal growth rate and dissolved oxygen (DO) production were used as the test endpoints. Compared to literature data, our test results based on the endpoint of DO production is 2.5 to 257 times more sensitive than the conventional algal batch tests. In addition, our analyses show that different relative toxicity relationships may be observed when different test methods or different endpoints are applied. The test alga was found to be quite sensitive to aldehydes, and a quantitative structure- activity relationship (QSAR) relationship was established based on the n-octanol/water partition coefficient (log K,,.). This study also evaluated the combined effects of aldehydes and nitriles. Four synergistic joint actions related to majononitrile were identified. On the other hand, most of the combined effects between aldehydes and acetonitrile were antagonistic. In general, we find that greater-than-additive effects mainly are associated with toxicants displaying flat dose-response curves, and less-than-additive effects may be related to certain steep-slope chemicals. Model analyses show that the above mixture toxicity behavior may be due to response addition or response multiplication joint action modes.

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