Doblin, MA, Blackburn, SI & Hallegraeff, GM 2000, 'Intraspecific variation in the selenium requirement of different geographic strains of the toxic dinoflagellate Gymnodinium catenatum', JOURNAL OF PLANKTON RESEARCH, vol. 22, no. 3, pp. 421-432.
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The requirement for selenium (IV) was assessed in five strains of the toxic dinoflagellate Gymnodinium catenatum Graham, representing three populations from Tasmania (Australia), as well as one each from Japan and Spain. Strains were grown in nutrient-en
Jegatheesan, V 2000, 'Transient stage deposition of submicron particles in deep bed filtration under unfavorable conditions', Water Research, vol. 34, no. 7, pp. 2119-2131.
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JEGATHEESAN, V & VIGNESWARAN, S 2000, 'Surface Coverage of Filter Medium in Deep Bed Filtration: Mathematical Modeling and Experiments', Separation Science and Technology, vol. 35, no. 7, pp. 967-987.
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Khalili, N, Khabbaz, MH & Valliappan, S 2000, 'An effective stress based numerical model for hydro-mechanical analysis in unsaturated porous media', Computational Mechanics, vol. 26, no. 2, pp. 174-184.
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Kwon, DY, Vigneswaran, S, Fane, AG & Ben Aim, R 2000, 'Experimental determination of critical flux in cross-flow microfiltration', SEPARATION AND PURIFICATION TECHNOLOGY, vol. 19, no. 3, pp. 169-181.
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Li, H 2000, 'An assessment of depolarisation models of crossflow microfiltration by direct observation through the membrane', Journal of Membrane Science, vol. 172, no. 1-2, pp. 135-147.
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Ngo, HH, Vigneswaran, S, Kim, SH, Bidkar, A & Moon, H 2000, 'Microfiltration-adsorption hybrid system in organics removal from water', Water Science and Technology, vol. 41, no. 10-11, pp. 51-57.
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A series of experiments was conducted with a Millipore flat plate microfiltration module modified to incorporate in-line powdered activated carbon (PAC) addition. In-line PAC was mixed continuously through a spiral mixing device for a predetermined time prior entering a membrane unit. The results showed that this system is excellent in removing fulvic acid (FA). This system provides to sufficient contact time for PAC to adsorb organics compared to the system with in-line adsorbent addition. More than 85% of FA was removed from water containing 8 mg/l of FA. To achieve this following conditions were used:.(i) a velocity gradient G (mixing intensity) of 160.4 s–1; (ii) a hydraulic residence time (mixing time) of 4 minutes; (iii) a PAC dose of 260 mg/l; and (iv) membrane pore size of 0.22 μm. In case of low FA concentration (e.g. 1.2 mg/l) in water, the removal efficiency was almost 100%. The removal efficiency also increased with the increase of mixing intensity and mixing time. The permeate flux slightly improved when a membrane of pore size 0.22 μm was used with shorter hydraulic residence time and lower PAC concentration. This paper presents a mathematical model developed based on surface diffusion. The model successfully predicted the performance of this hybrid system.
Sargent, CJ, Bowman, JC & Zhou, JL 2000, 'Levels of antifoulant irgarol 1051 in the Conwy Marina, North Wales', Chemosphere, vol. 41, no. 11, pp. 1755-1760.
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Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an antifouling agent used in paint formulations that are applied to the hulls of ships. A survey was carried out at Conwy Marina in North Wales to determine the levels of the herbicide over a period of three months. Liquid/liquid extraction was used to concentrate the analyte for quantitative analysis using gas chromatography/mass spectrometry (GC/MS) in the selected ion monitoring (SIM) mode. The concentrations of Irgarol 1051 in Conwy marina ranged from 7 to 543 ng/l, similar to the levels found in many other marinas, estuaries and ports in England, although much lower than those in Cote d’Azur, France. The concentrations of Irgarol 1051 were not found to be influenced by salinity, pH or temperature, although there is a strong correlation between the average concentrations of Irgarol 1051 and the density of boating activity. At the levels found in the marina, it is possible that non-target photosynthetic inhibition could occur. © 2000 Elsevier Science Ltd.
Vigneswaran, S, Ngo, HH, Hashimoto, K, Hasegawa, T & Watanabe, Y 2000, 'High rate floating medium flocculation-filtration with in-line polysilicato-iron (PSI) addition', ENVIRONMENTAL TECHNOLOGY, vol. 21, no. 3, pp. 317-325.
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The performance of a high rate floating medium flocculation-filtration system with an in-line addition of a silica-polymer compound, namely polysilicato-iron (PSI) has been investigated for water treatment. This study is intended to investigate the applicability of PSI as a sole flocculant or as a combined flocculant with an organic polymer in the downflow floating medium filter. The filter system was operated at a high loading rate of up to 60 m3 m-2 h-1. Filter column experiments were conducted at different PSI doses, filtration rates, filter depths and buoyant medium types and sizes. Results showed the filter system was able to yield uniform and filterable flocs (15 - 20 µm), even at a very high filtration rate of 60 m-3 h-1, through out the filter run time of 4 hours. Better filter performance was obtained when: (i) polystyrene beads of 1.9 mm diameter or polypropylene beads of 3.8 mm diameter; (ii) an in-line single dosage of 2.5 mg l-1 PSI; (iii) in-line combined dosages of 1.5 mg l-1 PSI and 0.4-0.6 mg l-1 organic polymers (cationic polyacrylamides, cationic polystyrene or Pollyallylamine hydrochloride) were used. When PSI was introduced as a sole flocculant, more than 90% turbidity was removed from a 54 NTU artificial kaolin clay suspension at a filtration rate of 30 m-3 m-2h-1 with very low headloss development. Greater removals were achieved when SIF was used in combination with a polymer (e.g.greater than 95% turbidity removal). Frequent (once in every 90 minutes) but short duration backwash (less than 60 s) by air and water enables the system to maintain a superior effluent quality (e.g. turbidity less than 1 NTU) during the filter run. Backwash water requirement was very low (approximately 1%-2% of filtered water production). A lower amount of sludge was produced from the filter in case of combined PSI and organic polymer coagulant addition.
Zhou, JL & Liu, YP 2000, 'Kinetics and equilibria of the interactions between diethylhexyl phthalate and sediment particles in simulated estuarine systems', Marine Chemistry, vol. 71, no. 1-2, pp. 165-176.
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The sorption of diethylhexyl phthalate (DEHP) by sediment particles has been studied under simulated estuarine conditions, using freshwater and seawater samples collected from the Conwy Estuary, North Wales. The sorption process was rapid, reaching a sorption equilibrium within 6 h at a sediment concentration (SC) of 2.16 g l-1. With an increase in SC, it took longer for the sorption equilibrium to be reached. The sorption equilibrium can be adequately described by the linear partition model at low equilibrium aqueous concentrations. The sorption of DEHP was enhanced in the presence of salts, due to the salting out effect, and a salting constant of 1.156 l mol-1 was obtained. The sorption coefficient of DEHP decreased with increasing SC, from 1.28 x 104 ml g-1 at 0.1 g l-1 SC to 6.75 x 103 ml g-1 at 14.66 g l-1 SC, due to the presence of colloidal particles in suspension which were able to bind DEHP. This third phase was quantified by measuring its dry weight, which was found to increase with increasing SC. The effect of colloids on DEHP sorption was studied by correcting the observed partition coefficients based on the concentration of colloid particles, and the true partition coefficients obtained (1.61 x 104 ± 1.29 x 103 ml g-1) were found to show much smaller variations than apparent partition coefficient (9.37 X 103 ± 2.12 x 103 ml g-1) at different SCs. Furthermore, the true organic carbon-normalised partition coefficients for the two sediments with different organic carbon content became similar and relatively independent of SCs. (C) 2000 Published by Elsevier Science B.V.
Zhou, JL, Hong, H, Zhang, Z, Maskaoui, K & Chen, W 2000, 'Multi-phase distribution of organic micropollutants in Xiamen Harbour, China', Water Research, vol. 34, no. 7, pp. 2132-2150.
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Xiamen Harbour, in the Xiamen Special Economic Zone of the People's Republic of China, was studied for its water and sediment quality, by determining the levels of 16 polycyclic aromatic hydrocarbons (PAHs), 12 polychlorinated biphenyls (PCBs) and 18 organochlorine insecticides in water, suspended particulate matter (SPM), pore water and sediment samples from nine stations in the Harbour. Total PAH concentrations varied from 106 to 945 ng/l in water, <1 to 3548 ng/l in pore water, and 247 to 480 ng/g dry weight in surficial sediments. Total PCB levels varied from 0.1 to 1.7 ng/l in water, 2.7 to 34.8 ng/l in pore water, and <0.01 to 0.32 ng/g dry weight in sediments. The levels of all insecticides were in the range of 6.6-19.6 ng/l (water), 11.8-78.5 ng/l (pore water), and <0.01-0.58 ng/g dry weight (sediment). The levels of total hexachlorocyclohexane (HCHs) in sediments varied from <0.01 to 0.14 ng/g dry weight, and those of total DDTs were in the range of <0.01-0.06 ng/g dry weight. The micropollutants were present in higher levels in pore water than in surface water, due possibly to higher concentrations of dissolved organic carbon or colloids with which the hydrophobic pollutants are strongly associated. Such a concentration gradient implies a potential flux of pollutants from sediment pore water to overlying water. The levels of pollutants in sediments are one to several orders of magnitude lower than those found in 1993, suggesting their decreased inputs in recent years in the form of fresh and less contaminated material and possible degradation over a period of time. Further work is needed to quantify the levels of these contaminants in suspended particulate matter, which are currently below the limits of detection. (C) 2000 Elsevier Science Ltd.
Masjuki, HH, Mahlia, TMI, Choudhury, IA & Saidur, R 1970, 'A literature review on energy efficiency standards and labels for household electrical appliances', 2000 TENCON Proceedings. Intelligent Systems and Technologies for the New Millennium (Cat. No.00CH37119), 2000 TENCON Proceedings. Intelligent Systems and Technologies for the New Millennium, IEEE, KUALA LUMPUR, MALAYSIA, pp. A103-A107.
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Masjuki, HH, Saidur, R, Choudhury, IA & Mahlia, TMI 1970, 'Factors effecting energy consumption of household refrigerator-freezers', 2000 TENCON Proceedings. Intelligent Systems and Technologies for the New Millennium (Cat. No.00CH37119), 2000 TENCON Proceedings. Intelligent Systems and Technologies for the New Millennium, IEEE, KUALA LUMPUR, MALAYSIA, pp. A92-A96.
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Ngo, HH, Vigneswaran, S, Kim, SH, Bidkar, A & Moon, H 1970, 'Microfiltration-adsorption hybrid system in organics removal from water', Water Science and Technology, 2nd International Conference on Membrane Technology in Environmental Management, I W A PUBLISHING, TOKYO, JAPAN, pp. 51-57.
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A series of experiments was conducted with a Millipore flat plate microfiltration module modified to incorporate in-line powdered activated carbon (PAC) addition In-line PAC was mixed continuously through a spiral mixing device for a predetermined time prior entering a membrane unit. The results showed that this system is excellent in removing fulvic acid (FA). This system provides to sufficient contact time for PAC to adsorb organics compared to the system with in-line adsorbent addition. More than 85% of FA was removed from water containing 8 mg/l of FA. To achieve this following conditions were used:.(i) a velocity gradient G (mixing intensity) of 160.4 s-1; (ii) a hydraulic residence time (mixing time) of 4 minutes; (iii) a PAC dose of 260 mg/l; and (iv) membrane pore size of 0.22 μm. In case of low FA concentration (e.g. 1.2 mg/l) in water, the removal efficiency was almost 100%. The removal efficiency also increased with the increase of mixing intensity and mixing timer. The permeate flux slightly improved when a membrane of pore size 0.22 μm was used with shorter hydraulic residence time and lower PAC concentration. This paper presents a mathematical model developed based on surface diffusion. The model successfully predicted the performance of this hybrid system.
Vigneswaran, S, Kwon, DY, Ngo, HH & Hu, JY 1970, 'Improvement of microfiltration performance in water treatment: is critical flux a viable solution?', Water Science and Technology, 2nd International Conference on Membrane Technology in Environmental Management, IWA Publishing, TOKYO, JAPAN, pp. 309-315.
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In this study, three definitions for critical flux were introduced based on the crossflow microfiltration (CFMF) experiments conducted under an operational mode of constant permeate flux. The critical flux based on material balance was calculated from the rate of particles deposition. The highest permeate flux results in no particle deposition being taken at the critical flux. The second definition was based on the increase in transmembrane pressure (TMP). The critical flux based on the TMP increase is the flux below which the membrane fouling does not occur. The third definition was based on the direct observation of particles deposition through microscope. Detailed experiments were conducted with synthetic suspension of different sizes of latex particles. Long term experiments conducted with polydispersed kaolin clay suspension indicated that the critical flux based on material balance concept is more realistic in field conditions.
