Aridgides, LJ, Doblin, MA, Berke, T, Dobbs, FC, Matson, DO & Drake, LA 2004, 'Multiplex PCR allows simultaneous detection of pathogens in ships' ballast water', MARINE POLLUTION BULLETIN, vol. 48, no. 11-12, pp. 1096-1101.
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There is enormous potential for global transfer of microorganisms, including pathogens, in ships' ballast water. We contend that a major advancement in the study of ballast-water microorganisms in particular, and of aquatic pathogens in general, will be expedited sample analysis, such as provided by the elegant technology of DNA microarrays. In order to use DNA microarrays, however, one must establish the appropriate conditions to bind target sequences in samples to multiple probes on the microarrays. We conducted proof-of-concept experiments to optimize simultaneous detection of multiple microorganisms using polymerase chain reaction (PCR) and Southern hybridization. We chose three target organisms, all potentially found in ballast water: a calicivirus, the bacterium Vibrio cholerae, and the photosynthetic protist Aureococcus anophagefferens. Here, we show simultaneous detection of multiple pathogens is possible, a result supporting the promising future use of microarrays for simultaneous detection of pathogens in ballast water.
Baines, SB, Fisher, NS, Doblin, MA, Cutter, GA, Cutter, LS & Cole, B 2004, 'Light dependence of selenium uptake by phytoplankton and implications for predicting selenium incorporation into food webs', LIMNOLOGY AND OCEANOGRAPHY, vol. 49, no. 2, pp. 566-578.
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The potentially toxic element selenium is first concentrated from solution to a large but highly variable degree by algae and bacteria before being passed on to consumers. The large loads of abiotic and detrital suspended particles often present in rivers and estuaries may obscure spatial and temporal patterns in Se concentrations at the base of the food web. We used radiotracers to estimate uptake of both selenite (Se(IV)) and C by intact plankton communities at two sites in the Sacramento/San Joaquin River Delta. Our goals were to determine (1) whether C and Se(IV) uptake were coupled, (2) the role of bacteria in Se(IV) uptake, and (3) the Se:C uptake ratio of newly produced organic material. Se(IV) uptake, like C uptake, was strongly related to irradiance. The shapes of both relationships were very similar except that at least 42-56% of Se(IV) uptake occurred in the dark, whereas C uptake in the dark was negligible. Of this dark Se(IV) uptake, 34-67% occurred in the 0.2-1.0-μm size fraction, indicating significant uptake by bacteria. In addition to dark uptake, total Se(IV) uptake consisted of a light-driven component that was in fixed proportion to C uptake. Our estimates of daily areal Se(IV):C uptake ratios agreed very well with particulate Se:C measured at a site dominated by phytoplankton biomass. Estimates of bacterial Se:C were 2.4-13 times higher than for the phytoplankton, suggesting that bacteriovores may be exposed to higher dietary Se concentrations than herbivores.
Doblin, MA, Popels, LC, Coyne, KJ, Hutchins, DA, Cary, SC & Dobbs, FC 2004, 'Transport of the harmful bloom alga Aureococcus anophagefferens by oceangoing ships and coastal boats', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 70, no. 11, pp. 6495-6500.
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It is well established that cyst-forming phytoplankton species are transported in ships' ballast tanks. However, there is increasing evidence that other phytoplankton species which do not encyst are also capable of surviving ballast transit. These species have alternative modes of nutrition (hetero- or mixotrophy) and/or are able to survive long-term darkness. In our studies of no-ballast-on-board vessels arriving in the Great Lakes, we tested for the presence of the harmful algal bloom species Aureococcus anophagefferens (brown tide) in residual (i.e., unpumpable) ballast water using methods based on the PCR. During 2001, the brown tide organism was detected in 7 of 18 ballast water tanks in commercial ships following transit from foreign ports. Furthermore, it was detected after 10 days of ballast tank confinement during a vessel transit in the Great Lakes, a significant result given the large disparity between the salinity tolerance for active growth of Aureococcus (>22 ppt) and the low salinity of the residual ballast water (similar to2 ppt). We also investigated the potential for smaller, recreational vessels to transport and distribute Aureococcus. During the summer of 2002, 11 trailered boats from the inland bays of Delaware and coastal bays of Maryland were sampled. Brown tide was detected in the bilge water in the bottoms of eight boats, as well as in one live-well sample. Commercial ships and small recreational boats are therefore implicated as potential vectors for long-distance transport and local-scale dispersal of Aureococcus.
GATIDOU, G, ZHOU, J & THOMAIDIS, N 2004, 'Microwave-assisted extraction of Irgarol 1051 and its main degradation product from marine sediments using water as the extractant followed by gas chromatography–mass spectrometry determination', Journal of Chromatography A, vol. 1046, no. 1-2, pp. 41-48.
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A microwave-assisted extraction (MAE) method for the determination of Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) and its main degradation product M1 (2-methylthio-4-tert-butylamino-s-triazine) in marine sediments by gas chromatography-mass spectrometry (GC-MS) was developed. The key parameters of MAE procedure, including the amount of the sediment, the volume of the extraction solvent, the duration and the temperature of the extraction procedure were optimized. The extraction procedure was followed by solid-phase extraction (SPE) on reverse phase C 18 cartridges. The isolation of the target compounds from the matrix was found to be efficient when 3 g of marine sediment were extracted with 30 ml of water for 10 min at 115°C. Final determination was accomplished by GC-MS. Quantification was performed with matrix-matched calibration using atrazine-d 5 as internal standard. Mean recoveries higher than 85.4% were obtained for both compounds at three fortification levels with relative standard deviations (R.S.D.) ≤ 14%. The limits of detection (LOD) of the developed method were 0.9 and 1.7 ng g -1 dry weight for M1 and Irgarol 1051, respectively. © 2004 Elsevier B.V. All rights reserved.
Gatidou, G, Zhou, JL & Thomaidis, NS 2004, 'Microwave-assisted extraction of Irgarol 1051 and its main degradation product from marine sediments using water as the extractant followed by gas chromatography–mass spectrometry determination', Journal of Chromatography A, vol. 1046, no. 1-2, pp. 41-48.
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Guo, WS, Vigneswaran, S, Ngo, HH & Chapman, H 2004, 'Experimental investigation of adsorption-flocculation-microfiltration hybrid system in wastewater reuse', JOURNAL OF MEMBRANE SCIENCE, vol. 242, no. 1-2, pp. 27-35.
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Membrane hybrid systems are becoming increasingly important as cost effective solutions in wastewater treatment and reuse. The effect of pretreatments namely floating medium flocculation (FMF) and powdered activated carbon (PAC) adsorption on organic and phosphorus removal was studied. The FMF was found to increase the phosphorus removal up to 97%. This preflocculation improved the dissolved organic removal only marginally (from 20% to 40%) whilst the pretreatment of adsorption increased the organic removal to more than 98%. The decline in filtration (permeate) flux of microfiltration was reduced by the incorporation of these pretreatment methods. Detailed studies on the effect of PAC dose indicated that a PAC dose of 1 g/L was the optimum in terms of organic removal and filtration flux. PAC doses in excess of 1 g/L contributed to a significant decrease in filtration flux. The critical flux was experimentally evaluated for crossflow microfiltration (CFMF) with and without the pretreatment. The pretreatment of adsorption led to six times higher critical flux than that without any pretreatment. The preflocculation alone did not significantly increase the critical flux. There was only a 33% increase with preflocculation. However, the preflocculation combined with PAC adsorption resulted in nine times higher critical flux. The results showed that a pretreatment of flocculation and adsorption led to almost complete phosphorus and organic removal while reducing the membrane clogging. © 2004 Elsevier B.V. All rights reserved.
Hill, R, Larkum, AWD, Frankart, C, Kuhl, M & Ralph, PJ 2004, 'Loss of functional Photosystem II reaction centres in zooxanthellae of corals exposed to bleaching conditions: using fluorescence rise kinetics', PHOTOSYNTHESIS RESEARCH, vol. 82, no. 1, pp. 59-72.
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Hill, R, Schreiber, U, Gademann, R, Larkum, AWD, Kuhl, M & Ralph, PJ 2004, 'Spatial heterogeneity of photosynthesis and the effect of temperature-induced bleaching conditions in three species of corals', MARINE BIOLOGY, vol. 144, no. 4, pp. 633-640.
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Heterogeneity in photosynthetic performance between polyp and coenosarc tissue in corals was shown using a new variable fluorescence imaging system (Imaging-PAM) with three species of coral, Acropora nobilis, Cyphastrea serailia and Pocillopora damicornis. In comparison to earlier studies with fibre-optic microprobes for fluorescence analysis, the Imaging-PAM enables greater accuracy by allowing different tissues to be better defined and by providing many more data points within a given time. Spatial variability of photosynthetic performance from the tip to the distal parts was revealed in one species of branching coral, A. nobilis. The effect of bleaching conditions (33°C vs. 27°C) was studied over a period of 8 h. Marked changes in fluorescence parameters were observed for all three species. Although a decline in ΦPSII (effective quantum yield) and Yi (the first effective quantum yield obtained from a rapid light curve) were observed, P. damicornis showed no visual signs of bleaching on the Imaging-PAM after this time. In A. nobilis and C. serailia, visual signs of bleaching over the 8 h period were accompanied by marked changes in F (light-adapted fluorescence yield), NPQ (non-photochemical quenching) and Ek (minimum saturating irradiance), as well as ΦPSII and Yi. These changes were most marked over the first 5 h. The most sensitive species was A. nobilis, which after 8 h at 33°C had reached a ΦPSII value of almost zero across its whole surface. Differential bleaching responses between polyps and coenosarc tissue were found in P. damicornis, but not in A. nobilis and C. serailia. NPQ increased with exposure time to 33°C in both the latter species, accompanied by a decreasing Ek, suggesting that the xanthophyll cycle is entrained as a mechanism for reducing the effects of the bleaching conditions. © Springer-Verlag 2004.
Hoang, TTL, Shon, HK, Chaudhary, DS, Vigneswaran, S & Ngo, HH 2004, 'Granular Activated Carbon (GAC) biofilter for low strength wastewater treatment', Fluid - Particle Separations Journal, vol. 16, no. 2, pp. 185-191.
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Biofilter can be a cost-effective alternative treatment unit, especially for low strength wastewater. In this study, detailed experimental investigation of a GAC biofilter was carried out in a laboratory-scale unit using low strength synthetic wastewater and biologically treated sewage effluent (BTSE). Performance of the biofilter was evaluated in terms of total organic carbon (TOC) removal. The TOC removal efficiency of the biofilter was found to be stabilized at around 40-45 % after 30 days (even for a short depth of GAC column of 7-15 cm). The maximum biomass retained on the activated carbon was measured to be 44 mg/ g of GAC after 49 days of continuous operation. Filter backwashing provided at 30% bed expansion for 5 minutes on a daily basis to overcome physical clogging of the filter by attached mass, did not have any adverse effect on the active biomass attached to the media and thus the organic removal efficiency of the filter remained unchanged. Molecular size distribution analysis showed that a significant removal of organics of small molecular weight (MW) at the initial stage of operation of biofilter followed by mainly large MW organic matter after one day of operation. This shows that adsorption was the main mechanism at the initial period and biological degradation as the predominating mechanism after one day of operation throughout the rest of the operation. The biofilter was found to remove a majority of hydrophilic organic compounds.
Huang, Z, Sun, X, Xiu, Z, Chen, S & Tsai, C-T 2004, 'Precipitation synthesis and sintering of yttria nanopowders', Materials Letters, vol. 58, no. 15, pp. 2137-2142.
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Indraratna, B, Bamunawita, C & Khabbaz, H 2004, 'Numerical modeling of vacuum preloading and field applications', CANADIAN GEOTECHNICAL JOURNAL, vol. 41, no. 6, pp. 1098-1110.
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This study describes the effect of unsaturation at a drain boundary on the behaviour of a single prefabricated vertical drain subjected to vacuum preloading based on a two-dimensional plane strain finite element model incorporating the modified Cam-Clay model. Unsaturation of soil adjacent to the drain can occur due to mandrel withdrawal or application of vacuum pressure through prefabricated vertical band drains (PVDs). Following initial laboratory simulation in a large-scale radial drainage consolidometer, the authors have attempted to explain the observed retardation of pore pressure dissipation through a series of models, which consider the effect of unsaturation at the drain-soil interface. The results indicate that the introduction of an unsaturated soil layer adjacent to a PVD improves the accuracy of numerical predictions. Lastly, a multidrain analysis is conducted to study the behaviour of an embankment stabilized with vertical drains subjected to vacuum preloading, and the field measurements are compared with a series of numerical model predictions.
Kalam, MA & Masjuki, HH 2004, 'Emissions and deposit characteristics of a small diesel engine when operated on preheated crude palm oil', Biomass and Bioenergy, vol. 27, no. 3, pp. 289-297.
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King, AJ, Readman, JW & Zhou, JL 2004, 'Determination of polycyclic aromatic hydrocarbons in water by solid-phase microextraction–gas chromatography–mass spectrometry', Analytica Chimica Acta, vol. 523, no. 2, pp. 259-267.
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A solid-phase microextraction (SPME)-gas chromatography (GC)-mass spectrometry (MS) analytical method for the simultaneous separation and determination of 16 polycyclic aromatic hydrocarbons (PAHs) from aqueous samples has been developed, based on the sorption of target analytes on a selectively sorptive fibre and subsequent desorption of analytes directly into GC-MS. The influence of various parameters on PAH extraction efficiency by SPME was thoroughly studied. Results show that the fibre exposure time and the use of agitation during exposure are critical in enhancing SPME performance. The presence of colloidal organic matter (as simulated by humic acid) in water samples is shown to significantly reduce the extraction efficiency, suggesting that SPME primarily extracts the truly dissolved compounds. This offers the significant advantage of allowing the differentiation between freely available dissolved compounds and those associated with humic material and potentially biologically unavailable. The method showed good linearity up to 10 μg/l. The reproducibility of the measurements expressed as relative standard deviation (R.S.D.) was generally <20%. The method developed was then applied to extract PAHs from sediment porewater samples collected from the Mersey Estuary, UK. Total PAH concentrations in porewater were found to vary between 95 and 742 ng/l with two to four ring PAHs predominating. Results suggest that SPME has the potential to accurately determine the dissolved concentrations of PAHs in sediment porewater. © 2004 Elsevier B.V. All rights reserved.
King, AJ, Readman, JW & Zhou, JL 2004, 'Dynamic behaviour of polycyclic aromatic hydrocarbons in Brighton marina, UK', Marine Pollution Bulletin, vol. 48, no. 3-4, pp. 229-239.
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The distribution of polycyclic aromatic hydrocarbons (PAHs) between various phases is fundamental in the control of their movement and impact in the marine environment. In this study samples of water and sediments were regularly collected from Brighton marina, UK, to quantify the intensity, spatial and temporal variations of PAH contamination. The results show clearly that PAH behaviour in marine systems is highly complex, and controlled by the interplay of PAH sources, compound physicochemical properties, water and sediment movement, and field conditions. Levels of total PAHs (16 compounds) in the dissolved phase were found to vary between <2 and 11,400 ng/l, with higher values observed in the winter months. Total PAH concentration in sediment samples varied between 24 and 4710 ng/g dry weight. PAHs in water were dominated by low molecular mass compounds (2-ring), while PAHs in sediments were mainly derived from 2-4 ring compounds. In addition, dissolved concentrations were increased during sediment dredging and after a period of severe rainfall. PAHs in Brighton marina are likely to be from both pyrolytic and petrogenic sources; as a result, field-derived distribution coefficients for individual PAHs between sediment and water tend to follow the equilibrium partition models, although slight exceedance is apparent. The extended partition model incorporating soot carbon has achieved limited success in better predicting PAH behaviour. © 2003 Elsevier Ltd. All rights reserved.
Liu, R, Zhou, JL & Wilding, A 2004, 'Microwave-assisted extraction followed by gas chromatography–mass spectrometry for the determination of endocrine disrupting chemicals in river sediments', Journal of Chromatography A, vol. 1038, no. 1-2, pp. 19-26.
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In this study, microwave-assisted extraction (MAE) followed by gas chromatography (GC)-mass spectrometry (MS) analysis has been successfully developed for the simultaneous extraction and determination of contrasting endocrine disrupting chemicals (EDCs) including 17β-estradiol, estrone, 17α-ethynylestradiol, 16α-hydroxyestrone, 4-nonylphenol, 4-tert-octylphenol and bisphenol A in river sediments. For MAE, the effects of various parameters on the extraction efficiency were investigated. It is shown that the most efficient extraction (recovery >74%) of the target compounds was achieved by using methanol as the solvent, an extraction temperature of 110°C and 15 min of holding time. The cleanup of extracts was carried out by passage through a non-deactivated silica gel column, and a satisfactory elution efficiency of all compounds was achieved using a solvent mixture of ethyl acetate-hexane (4:6, v/v). The spiking experiments show that the mean recovery of the target compounds exceeded 61% at a spiking level of 5 ng/g dry mass, and 73% at 10, 40 and 100 ng/g dry mass with a good reproducibility. The method developed was applied to the determination of target EDCs in river sediments collected from rivers Uck and Ouse, UK, and results revealed the presence of the chosen compounds at low ng/g level. © 2004 Elsevier B.V. All rights reserved.
Liu, R, Zhou, JL & Wilding, A 2004, 'Simultaneous determination of endocrine disrupting phenolic compounds and steroids in water by solid-phase extraction-gas chromatography-mass spectrometry', JOURNAL OF CHROMATOGRAPHY A, vol. 1022, no. 1-2, pp. 179-189.
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Liu, R, Zhou, JL & Wilding, A 2004, 'Simultaneous determination of endocrine disrupting phenolic compounds and steroids in water by solid-phase extraction–gas chromatography–mass spectrometry', Journal of Chromatography A, vol. 1022, no. 1-2, pp. 179-189.
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A solid-phase extraction (SPE)-gas chromatography (GC)-mass spectrometry (MS) analytical method for the simultaneous separation and determination of endocrine disrupting chemicals (EDCs) from water samples is described in detail. Important and contrasting EDCs including estrone, 17β-estradiol, 17α-ethynylestradiol, 16α-hydroxyestrone, 4-nonylphenol, bisphenol A and 4-tert-octylphenol were selected as the target compounds. The SPE technique, followed by the derivatisation with bis (trimethylsilyl) trifluoroacetamide was used for the extraction recoveries of target compounds from water samples. A number of parameters that may affect the recovery of EDCs, such as the type of SPE cartridges, eluents, as well as water properties including pH value, and concentration of salts and humic substances were investigated. It is shown that the Oasis cartridges produced the best recoveries of target EDCs while ethyl acetate was efficient in eluting EDCs from SPE cartridges. The recovery of some EDCs was enhanced by the addition of salt, but reduced by the increase in pH value and humic acid concentration. The optimised method was further verified by performing spiking experiments in natural river water and seawater matrices, with good recovery and reproducibility for all the selected compounds. The established method was successfully applied to environmental water samples from East and West Sussex, UK, for the determination of the target EDCs. © 2003 Elsevier B.V. All rights reserved.
Macinnis-Ng, CMO & Ralph, PJ 2004, 'In situ impact of multiple pulses of metal and herbicide on the seagrass, Zostera capricorni', AQUATIC TOXICOLOGY, vol. 67, no. 3, pp. 227-237.
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Tides and freshwater inflow which influence water movement in estuarine areas govern the exposure-regime of pollutants. In this experiment, we examined the in situ impact of double pulses of copper and the herbicide Irgarol 1051 on the photosynthesis of the seagrass, Zostera capricorni. Despite a 4-day recovery period between the two 10h pulses of toxicant, the effective quantum yield of photosystem II (ΔF/Fm′) and total chlorophyll concentrations indicated that multiple-pulses had a greater impact than a single pulse. During the first exposure period, samples exposed to Irgarol 1051 had ΔF/Fm′ values as low as zero while controls remained around 0.6 relative units. After the second exposure period, treated samples recovered to only 0.4 relative units. Samples exposed to copper had ΔF/Fm′ values around 0.3 relative units during the first exposure period and while these samples recovered before the second dose, they remained below 0.2 relative units after the second exposure period. Alternate samples were also exposed to one toxicant, allowed to recover and then exposed to the other toxicant. ΔF/Fm′ values indicated that copper exposure followed by Irgarol 1051 exposure was more toxic than Irgarol 1051 exposure followed by copper exposure. © 2004 Elsevier B.V. All rights reserved.
Mahlia, TMI 2004, 'Methodology for predicting market transformation due to implementation of energy efficiency standards and labels', Energy Conversion and Management, vol. 45, no. 11-12, pp. 1785-1793.
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Mahlia, TMI, Masjuki, HH, Saidur, R & Amalina, MA 2004, 'Cost–benefit analysis of implementing minimum energy efficiency standards for household refrigerator-freezers in Malaysia', Energy Policy, vol. 32, no. 16, pp. 1819-1824.
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Mahlia, TMI, Masjuki, HH, Saidur, R & Amalina, MA 2004, 'Viewpoint', Energy Policy, vol. 32, no. 16, pp. 1783-1787.
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Nghiem, LD, Schäfer, AI & Elimelech, M 2004, 'Removal of Natural Hormones by Nanofiltration Membranes: Measurement, Modeling, and Mechanisms', Environmental Science & Technology, vol. 38, no. 6, pp. 1888-1896.
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Nguyen, TV, Vigneswaran, S, Huu, HN, Pokhrel, D & Viraraghavan, T 2004, 'Iron coated sponge in arsenic removal', Fluid - Particle Separations Journal, vol. 16, no. 2, pp. 175-184.
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Arsenic (As) contamination in water has raised a grave concern in many regions of the world. Arsenic can lead to a number of health problems even at very low concentration. This paper presents the laboratory-scale experimental results on the specific treatment technology: iron coated sponge (IOCSp) adsorption in As removal. The results indicated that IOCSp could remove 47.3% to 65% of As (III) and As (V) after a 1 hour contact with IOCSp (initial As concentration = 260 μg/l; 0.15g sponge/100ml solution). A nine hour-adsorption led to a very high As removal efficiency (more than 92.4% removal for both As (III) and As (V)). Each gram of IOCSp adsorbed about 160μg of As (III) and As (V) upon a 9 hour - contact of IOCSp with the As solution. After adsorption, IOCSp can be easily regenerated by NaOH.
Ryan, KG, Ralph, P & McMinn, A 2004, 'Acclimation of Antarctic bottom-ice algal communities to lowered salinities during melting', POLAR BIOLOGY, vol. 27, no. 11, pp. 679-686.
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Sea-ice brine algal communities were exposed to salinities between 30 and 10‰ during melting. There was a progressive decline in maximum quantum yield, relative electron transfer rate (rETRmax) and photosynthetic efficiency (α) with decreasing salinity of the final melted sample. While all species showed a drop in these parameters, Fragilariopsis curta and Entomoneis kjellmannii showed the least inhibition. There was a steady increase in rETRmax and alpha; over 5 days after melting, especially in the samples melted into the highest salinities. In addition, the samples melted from the ice without added filtered seawater showed no photosynthetic activity after 2 days. Our results suggest that for experimental work using sea-ice microalgae, the final salinity of the melted sample should be greater than 28‰ (i.e. the ratio of sea ice to filtered seawater should be at least 1:2). © Springer-Verlag 2004.
Shim, WG, Chaudhary, DS, Vigneswaran, S, Ngo, HH, Lee, JW & Moon, H 2004, 'Mathematical modeling of granular activated carbon (GAC) biofiltration system', KOREAN JOURNAL OF CHEMICAL ENGINEERING, vol. 21, no. 1, pp. 212-220.
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In this study, a mathematical model of a fixed bed Granular Activated Carbon (GAC) biofiltration system was developed to predict the organic removal efficiency of the filter. The model consists of bulk transportation, adsorption, utilization, and biodegradation of organics. The variation of the specific surface area due to biofilm growth and the effect of filter backwash were also included in the model. The intrapellet diffusion and the diffusion of substrate in the biofilm were described by linear driving force approximation (LDFA) method. Biodegradation of organics was described by Monod kinetics. Sips adsorption isotherm was used to analyze the initial adsorption equilibrium of the system. The model showed that the organic removal efficiency of the biofilter greatly depends on the parameters related to the biological activities such as the maximum rate of substrate utilization (kmax) and biomass yield (Y) coefficients. Parameters such as suspended cell concentration (Xs) and decay constant (Kd) had little effects on the model simulation results. The filter backwash also had no significant impact on the performance of the biofilter.
Shon, HK, Guo, WS, Vigneswaran, S, Ngo, HH & Kim, IS 2004, 'Effect of flocculation in membrane-flocculation hybrid system in water reuse', SEPARATION SCIENCE AND TECHNOLOGY, vol. 39, no. 8, pp. 1871-1883.
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Preflocculation reduces the fouling of membranes in cross-flow microfiltration (CFM) thus leading to high quality product water at economic filtration flux. As such, this hybrid system will have a major impact in treating the biologically treated sewage effluent. The preflocculation achieved through the floating medium flocculation (FMF) was found to increase the phosphorus removal up to 96%. The decline in microfiltration permeate flux with time was reduced by the incorporation of flocculation. However, the improvement in the removal of dissolved organic carbon (DOC) was marginal from 20% with membrane alone to 46% with the membrane-flocculation hybrid system). The flocculation followed by adsorption its pre-treatment helped to increase the DOC removal as high as 98%. Flocculation was found to remove more than 66% of colloidal effluent organic matter (EfOM). An attempt was also made to quantify the hydrophobic fraction in the pretreated effluent and to identify the molecular weight (MW) range of organics removed by the flocculation. The pretreatment of flocculation was found to remove 68.5%, 61.8%, and 62.9% of hydrophobic, hydrophilic, and transphilic organic matter. The MW size distribution analysis indicated that flocculation with ferric chloride removed a majority of organic matter in the MW range of 300-5000 Da.
Shon, HK, Vigneswaran, S, Kim, IS, Cho, J & Ngo, HH 2004, 'Effect of pretreatment on the fouling of membranes: application in biologically treated sewage effluent', JOURNAL OF MEMBRANE SCIENCE, vol. 234, no. 1-2, pp. 111-120.
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Reuse of wastewater can help in maintaining environmental quality and relieving the unrelenting pressure on conventional and natural freshwater sources. Membrane processes find an important place in the wastewater treatment for reuse. Nonetheless, reverse osmosis (RO) and nanofiltration (NF), i.e. non-porous membranes require higher operational costs and energy. Thus, in this research NTR 7410 ultrafiltration (UF) membrane which is porous was used without and with pretreatment to treat biologically treated sewage effluent (BTSE). Four different pretreatment methods, namely, ferric chloride (FeCl3) flocculation, powdered activated carbon (PAC) adsorption, flocculation followed by adsorption, and granular activated carbon (GAC) biofilter were used in this study to compare their relative merits. Experimental results indicate that the most suitable pretreatment was flocculation followed by adsorption leading to a total organic carbon (TOC) removal of 90%. To assess the suitability of the membranes, it is important to conduct a detailed membrane characterization. The fouled NTR 7410 membrane surface was analyzed in terms of contact angle, zeta potential, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), flux decline, and TOC removal. The contact angle of the fouled membrane surface was lower than that of the clean membrane surface. This suggests that the majority of the foulants may have been the hydrophilic organic compounds such as polysaccharides, urea, etc. which are the extracellular enzyme of microorganisms in BTSE
Shon, HK, Vigneswaran, S, Kim, IS, Cho, J & Ngo, HH 2004, 'The effect of pretreatment to ultrafiltration of biologically treated sewage effluent: a detailed effluent organic matter (EfOM) characterization', WATER RESEARCH, vol. 38, no. 7, pp. 1933-1939.
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Ultrafiltration alone can remove only a portion of the effluent organic matter (EfOM) from biologically treated sewage effluent (BTSE). Use of pretreatment not only improves the EfOM removal but also reduces the membrane fouling. In this research, NTR 7410 ultrafiltration membrane was employed to remove EfOM from BTSE. Different pretreatments namely FeCl3 flocculation and powder activated carbon adsorption were evaluated. The highest removal of organic matter was observed when flocculation followed by adsorption was used as pretreatment. The flocculation and adsorption removed 68.5% and 71.4% of hydrophobic organics, respectively. The molecular weight (MW) of the EfOM in BTSE ranged from 300 to about 400,000Da. After the flocculation pretreatment, the majority of large MW organic matter was removed. The pretreatment of the flocculation followed by adsorption led to very high removal of both small and large organic matter. Further, this pretreatment led to practically no filtration flux decline. © 2004 Elsevier Ltd. All rights reserved.
Smith, PJ, Vigneswaran, S, Huu, HN, Ben-Aim, R & Nguyen, H 2004, 'Investigation of membrane de-clogging techniques in the Submerged Membrane Filtration Adsorption Hybrid System (SMFAHS)', Fluid - Particle Separations Journal, vol. 16, no. 2, pp. 165-173.
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Membrane clogging is a major obstacle to the successful operation of the membrane separation process. A submerged hollow fibre membrane with powdered activated carbon (PAC) adsorption (adsorption-membrane hybrid system) was used for the removal of organics from a synthetic wastewater representative of biologically treated sewage effluent. PAC usage successfully adsorbs the majority of the organics, and then the organic laden PAC is separated by the membrane reducing the direct organic loading to the membrane. However, membrane clogging still occurs. This study involved the development of an automation system and Supervisory Control and Data Acquisition (SCADA) system for performing an investigation and evaluation of three automated de-clogging techniques. The first de-clogging method involved the use of periodic relaxation, whereby permeate production for 12 minutes was periodically stopped for 3 minutes and the shear forces created by the aeration system and the absence of suction pressure during the relaxation period were used to de-clog the membrane. The second de-clogging method involved the use of a series of periodic back flush experiments with varied frequencies and durations to force permeate in the opposite direction out through the membrane pores. The optimal results in terms of de-clogging the membrane were achieved using a 15 second backflush after 15 minutes of permeate production. The third de-clogging method involved the application of an understanding of results of the periodic back flush series of experiments to design an automation system with a new approach to backflushing where an upper limit of a transmembrane pressure (TMP) increase each cycle was used to initiate the backflush. The transmembrane pressure represents the pressure measured across the membrane and it is a vital parameter indicating the degree of fouling of the membrane. A periodic backflush was found to be significantly more effective in terms of increasing the total ...
Stewart, AR, Luoma, SN, Schlekat, CE, Doblin, MA & Hieb, KA 2004, 'Food web pathway determines how selenium affects aquatic ecosystems: A San Francisco Bay case study', ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol. 38, no. 17, pp. 4519-4526.
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Chemical contaminants disrupt ecosystems, but specific effects may be under-appreciated when poorly known processes such as uptake mechanisms, uptake via diet, food preferences, and food web dynamics are influential. Here we show that a combination of food web structure and the physiology of trace element accumulation explain why some species in San Francisco Bay are threatened by a relatively low level of selenium contamination and some are not. Bivalves and crustacean zooplankton form the base of two dominant food webs in estuaries, The dominant bivalve Potamocorbula amurensis has a 10-fold slower rate constant of loss for selenium than do common crustaceans such as copepods and the mysid Neomysis mercedis (rate constant of loss, k(e) = 0.025, 0.155, and 0.25 d(-1), respectively). The result is much higher selenium concentrations in the bivalve than in the crustaceans. Stable isotope analyses show that this difference is propagated up the respective food webs in San Francisco Bay. Several predators of bivalves have tissue concentrations of selenium that exceed thresholds thought to be associated with teratogenesis or reproductive failure (liver Se > 15 mug g(-1) dry weight). Deformities typical of selenium-induced teratogenesis were observed in one of these species. Concentrations of selenium in tissues of predators of zooplankton are less than the thresholds. Basic physiological and ecological processes can drive wide differences in exposure and effects among species, but such processes are rarely considered in traditional evaluations of contaminant impacts.
Tien, VN, Chaudhary, DS, Ngo, HH & Vigneswaran, S 2004, 'Arsenic in water: Concerns and treatment technologies', JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY, vol. 10, no. 3, pp. 337-348.
Vigneswaran, S, Shon, HK, Boonthanon, S, Ngo, HH & Aim, RB 2004, 'Membrane-flocculation-adsorption hybrid system in wastewater treatment: micro and nano size organic matter removal', WATER SCIENCE AND TECHNOLOGY, vol. 50, no. 12, pp. 265-271.
Wilding, A, Liu, R & Zhou, JL 2004, 'Validation of cross-flow ultrafiltration for sampling of colloidal particles from aquatic systems', Journal of Colloid and Interface Science, vol. 280, no. 1, pp. 102-112.
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The use of cross-flow ultrafiltration (CFF) for the isolation of colloids from the bulk aquatic matrices has been increasing over the last decade; however, a thorough validation of each CFF system is needed before its application to natural samples. Laboratory experiments have been conducted to validate a 1-kDa Millipore Pellicon 2 cartridge type CFF system, using a range of molecular probes spiked in natural waters. Using the separation data of these probes, key validation parameters have been calculated, including retention coefficient (RC), concentration factor (cf), colloid concentration, recovery, and mass balance. The permeation behaviour of these molecules has also been studied using a simple permeation model. Results show that good retention (>80%) of high molecular weight (HMW, >1 kDa) molecules and low retention (<20%) of low molecular weight (LMW, <1 kDa) molecules can be achieved at high cf values or over long timescales. In addition, permeation modelling and the calculation of colloid concentration demonstrate the same findings, again recommending high cf values or long timescales for ultrafiltration to minimise the retention of LMW molecules. The retention characteristics of 3-kDa dextran change slightly with salinity. Mass balance calculations show good recoveries for all of the molecules tested. The apparent membrane molecular cut-off of the CFF system has been estimated to be between 2.1 and 2.5 kDa, which is slightly greater than the manufacturer's nominal MW cut-off of 1 kDa. © 2004 Elsevier Inc. All rights reserved.
Zhang, ZL, Hong, HS, Zhou, JL & Yu, G 2004, 'Phase association of polycyclic aromatic hydrocarbons in the Minjiang River Estuary, China', Science of The Total Environment, vol. 323, no. 1-3, pp. 71-86.
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Persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) are of great concern due to their persistence, bioaccumulation and toxic effects. In this work the levels of 16 priority PAHs were determined in water, pore water, sediment, soil and vegetable samples from Minjiang River Estuary, China. Total PAH concentrations varied from 9.9 to 474 μg/l in water, 82.1 to 239 μg/l in pore water, 112 to 877 ng/g dry wt. in surficial sediments, 128 to 465 ng/g dry wt. in soil and 8600 to 111000 ng/g dry wt. in Chinese vegetables. Overall, the mean concentrations of PAHs were present in higher levels in pore water than that in surface water, due possibly to higher concentrations of dissolved organic carbon or colloids with which the hydrophobic pollutants were strongly associated. Such a concentration gradient implies a potential flux of pollutants from sediment pore water to overlying water. Contamination was dominated by high molecular mass PAH compounds in all samples, indicating combustion-derived sources (for example, pyrolysis at high temperature). The levels of PAHs in water and vegetable were relatively high in comparison to other studies, although PAHs in sediment and soil were comparable to those found in many other similar environments. The ratios of selected PAHs indicated again that PAHs in Minjiang River Estuary were mainly derived from incomplete combustion of fossil fuel. © 2003 Elsevier B.V. All rights reserved.
Guo, W, Vigneswaran, S & Ngo, H 1970, 'A Rational Approach In Controlling Membrane Fouling Problems: Pretreatments to a submerged Hollow Fibre Membrane System', Water Environment - Membrane Technology Proceedings, IWA Specialty Conference, Water Environment-Membrane Technology, IWA, Seoul, Korea, pp. 517-524.
Guo, W, Vigneswaran, S, Ngo, H & Ben Aim, RM 1970, 'Performance of a Submerged Membrane Adsorption Hybrid System (SMAHS) in Wastewater Treatment for Reuse', 4th World Water congress: innovations in Drinking Water Treatment, IWA World Water Congress, IWA, Marrakech, Morocco, pp. 1-8.
Indraratna, B, Khabbaz, H & Salim, W 1970, 'A laboratory study on improvement of railway ballast using geosynthetics', GEOTECHNICAL ENGINEERING FOR TRANSPORTATION PROJECTS, VOL 1, GeoTrans 2004 - Geotechnical Engineering for Transportation Projects, ASCE, Los Angeles, California, USA, pp. 617-626.
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The classical railway track basically consists of a flat framework made up of rails and sleepers, which are supported on ballasted track formation. Ballast particles breakdown and deteriorate progressively under heavy cyclic rail loading. Moreover, excessive consolidation settlement and progressive shear failure may occur in soft track formation under repetitive stresses. In order to rectify these problems, frequent maintenance operations are generally required in ballasted track. In order to minimize the deterioration of track substructure and also to reduce maintenance cost, the use of various types of geosynthetics including recycling of waste ballast have been studied in the laboratory. The prospective use of three types of geosynthetics (i.e. geogrids, geotextiles and geocomposites) in enhancing the performance of fresh and recycled ballast has been examined. The aspects of deformation and degradation of ballast under cyclic loading have been studied using a large-scale prismoidal triaxial rig. The research findings reveal that recycled ballast stabilized with geosynthetic reinforcement has a good potential for resilient track construction and for reducing the cost of track maintenance. The experimental findings may be beneficial to the railway engineers and encourage them to upgrade current tracks based on these innovative techniques.
Kalam, MA, Masjuki, HH, Maleque, MA, Amalina, MA, Abdesselam, H & Mahlia, TMI 1970, 'Air -Fuel Ratio Calculation for a Natural Gas Fuelled Spark Ignition Engine', SAE Technical Paper Series, SAE 2004 World Congress & Exhibition, SAE International.
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Air-fuel ratio (AFR) is a crucial parameter for combustion controls in internal combustion engines. An incorrect AFR metering for reciprocating internal combustion engine causes high toxic gases emissions formulation, serious fuel consumption problems and unbearable combustion noise and combustion deterioration. Traditionally, the AFR is obtained by direct measurement of intake air and the fuel either injected into the combustion chamber or pre-mixed at the carburetor. However, the accurate AFR obtained from direct measurement is difficult due to measuring equipments resolution prone to errors. This paper describes a method for accurate determination of air-fuel ratio based on exhaust emission gas analysis as an additional tool used to be validated the conventional direct air fuel flow rates measurement. This method explains all the possible parameters that may affect the accuracy of air-fuel ratio measurement which includes the instrument error, ambient conditions, the assumed water-gas shift reaction constant, the humidity of the atmospheric air and the inclusion of nitrogen in the air-fuel ratio model. Results show that four essential exhaust gas emission concentrations, namely carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2) and unburn hydrocarbons (HCs) are adequate for obtaining an accurate air-fuel ratio. The fuel type and the range of parameters that may affect the accuracy of air-fuel ratio are properly defined. This paper will also present experimental results of a bi-fuel natural gas spark ignition engine to be compared with computational results. The results of this investigation will be used to develop a new dedicated natural gas engine. Copyright © 2004 SAE International.
Nguyen, V, Vigneswaran, S, Ngo, H, Pokhrel, D & Viraraghavan, T 1970, 'Arsenic Removal by Iron Coated Sponge in Drinking Water Treatment', The 2nd International Symposium on Southeast Asian Water Environment, The Second International Symposium on Southeast Asian Water Environment, The University of Tokyo, Hanoi, Vietnam, pp. 214-221.
Shon, H, Vigneswaran, S, Kim, IS, Cho, J & Ngo, H 1970, 'Characterization of Different Treatments With Biologically Treated Sewage Effluent and Synthetic Wastewater', Enviro 04 Convention & Exhibition, Enviro 04, Enviroaust Convention Limited, Darling Harbour, Australia, pp. 1-10.
Shon, H, Vigneswaran, S, Kim, J, Ngo, H & Park, N 1970, 'Comparison of Nanofiltration with Flocculation-Microfiltration-Photocatalysis Hybrid System in Dissolved Organic Matter Removal', 9th World Filtration Congress, World Filtration Congress, The American Filtration and Separation Society, New Orleans, Louisiana, USA, pp. 1-19.
Turner, BD, Binning, P & Sloan, S 1970, 'The CO2 enhanced removal of fluoride using a calcite permeable reactive barrier', GEOCHIMICA ET COSMOCHIMICA ACTA, 14th Annual V M Goldschmidt Conference, PERGAMON-ELSEVIER SCIENCE LTD, Univ Copenhagen, Copenhagen, DENMARK, pp. A460-A460.
