Engineering

Publication Search Results

Now showing 1 - 10 of 11
  • (1997) Peters, G; Maher, WA; Barford, JP; Gomes, VG
    Journal Article
    Selenium (Se) is a contaminant of concern in environments affected by discharges from smelting and coal-burning industries. Experiments have been performed to investigate the phase associations of selenium in contaminated sediments under a range of controlled redox conditions. In this study, Se sediment associations were examined using the BCR sequential extraction technique after stabilisation at different redox states. It was shown that although most of the sediment-bound Se is associated with the operationally-defined "organic/sulfide" fraction, as the measured redox potential of the system is increased, more Se moves into the "exchangeable" and "iron/manganese oxyhydroxide" fractions. In these fractions, contaminants can be expected to be more bioavailable. As the mass of Se absorbed to sediments is typically at least an order of magnitude higher than the mass dissolved in porewaters, significant Se exposure may result from oxidative shifts in Se sediment associations.

  • (1999) Peters, G; Maher, WA; Jolley, D; Carroll, BI; Jenkinson, AV; McOrist, GD
    Journal Article
    This paper examines the history of selenium pollution in Lake Macquarie, NSW, Australia, and three factors that may affect the redistribution and remobilisation of particle bound selenium: changes in redox state, bioturbation, and bioaccumulation by macrobenthos and bacteria. Sediment cores were taken from Nords Wharf, a relatively unpolluted area, and from Mannering Bay near the Vales Point coal-fired power station. The age profile at the unpolluted site seems to indicate that mild selenium pollution has been occurring for over 100 years, however, some mixing of the sediments has occurred. At the polluted site, the age profile indicated that major contamination has occurred in the last 30 years, due to an ash dam associated with nearby electric power generation facilities. The contamination chronology suggests that remobilisation and reduction processes have affected the selenium profile. Changing the redox state of Lake Macquarie sediment results in a release of selenium under oxidising conditions and immobilisation under reducing conditions. The sediment-bound selenium was associated with the operationally defined `organic/sulfide' fraction under reducing conditions, and as the redox potential increases this moves into the `exchangeable' and `iron/manganese oxyhydroxide' phases to a limited extent. Bioturbation by the animals Marphysa sanguinea and Spisula trigonella caused increases in the redox potential and pore water selenium concentrations in surfcial sediments relative to unbioturbated controls. Both animals accumulated significantly more selenium when exposed to contaminated sediment than when exposed to uncontaminated control sediments. Selenium concentrations in molluscs from Mannering Bay were all significantly higher than those collected from Nords Wharf. Most of the selenium in the mollusc tissues was found to be associated with the protein fraction. Selenium isolated from hydrolysed muscle tissue was not present as selenate or selenite but as selenomethionine and an unidentified compound. Seven types of bacteria were isolated from Lake Macquarie sediment. All seven isolates were able to transform selenite quantitatively to elemental selenium as evidenced by a red precipitate and identified by X-ray diffraction. Six isolates grew on media containing selenate but no elemental selenium was formed. Mass balances showed that for three isolates total selenium was conserved, selenate decreased and selenium (0; II-) increased indicating the production of non-volatile organic selenium compounds. For two isolates both total selenium and selenate decreased with no increase in selenium (0; II-), therefore, loss of selenium occurred from the media. Selenium is immobile in anoxic reduced sediments but may become available to benthos and fish as a consequence of sediment oxidation associated with bioturbation leading to bioaccumulation and transformation by macrobenthos and bacteria. These mechanisms can be invoked as possible transport pathways to explain the presence of selenium above background concentrations in preindustrial sediments, but further work dating the sediments in which elevated concentrations of selenium are found is needed to confirm this hypothesis.

  • (1997) Nobbs, Denis M.; Barford, John P.; Carroll, Brett I.; Peters, Gregory M.
    Journal Article
    Lake Macquarie, an estuarine lake on Australia's eastern seaboard, has been subject for almost a century to anthropogenic contamination by heavy metals and metalloids, including selenium, arising from industrial sources including a lead-zinc smelter, coal-fired power stations and sewage works. , Selenium tissue concentrations in fish from the Lake have recently been reported at up to twelve times those recommended for human consumption. This paper describes an integrated investigation into selenium contamination in the Lake over a four-year period. One key component of these investigations is the ability of indigenous micro-organisms to reduce selenium in estuarine sediments from higher to lower oxidation states, therefore immobilising or volatilising it, and the use of this in the treatment of industrial wastewaters or potentially the in-situ bioremediation of contaminated sediments. A second key component is a study of the mechanisms controlling sediment-stored selenium concentrations and the extent to which they can be influenced by bioturbative organisms. Integrated into these two broad areas and described here are a number of related investigations into: bioavailability of sediment-bound selenium; computer modelling of selenium biogeochemistry; representation of heavy metal data in a GIS format; and determination of the specific historical contributions of a power station to selenium loads in the Lake. Through this integrated approach we have built on synergies between the separate components of our research program to add to our understanding of the nature of selenium biogeochemistry in the Lake and to propose potential bioremediation strategies for both the Lake and contaminated industrial wastewaters or surface water.

  • (1999) Peters, G; Maher, WA; Krikowa, F; Roach, AC; Jeswani, HK; Barford, JP; Gomes, VG; Reible, DD
    Journal Article
    Measurements of selenium in sediments and benthic infauna of Lake Macquarie, an estuary on the east coast of Australia, indicate that sediments are a significant source of selenium in the lake's food web. Analysis of surficial sediment samples indicated higher selenium con- concentrations near what are believed to be the main industrial sources of selenium to the lake: a smelter and a power station. Sediment cores taken from sediments in Mannering Bay, near a power station at Vales Point, contained an average of 12 times more selenium in surficial sections than sediment cores from Nord's Wharf, a part of the lake remote from direct inputs of selenium. The highest selenium concentration found in Mannering Bay sediments (17.2 mg/g) was 69 times the apparent background concentration at Nord's Wharf (0.25 mg/g). Pore water concentrations in Mannering Bay were also high, up to 5 mg/l compared to those at Nord's Wharf which were below detection limits (0.2 mg/l). Selenium concentrations in muscle tissues of three benthic-feeding fish species (Mugil cephalus, Platycephalus fuscus, Acanthopagrus australis) were significantly correlated ( p < 0:05) with surficial sediment selenium concentra- tion. Selenium concentrations in polychaetes and molluscs of Mannering Bay were up to 58 times higher than those from Nord's Wharf. Two benthic organisms, the eunicid polychaete Marphysa sanguinea and the bivalve mollusc Spisula trigonella, were maintained at different densities in selenium-spiked sediments. Both animals accumulated selenium from the spiked sediment, confirming that bioaccumulation from contaminated sediments occurs. Collectively, these data suggest that benthic food webs are important sources of selenium to the fish of Lake Macquarie.

  • (2001) Peters, G; Lundie, S
    Journal Article
    Biosolids are the reusable organic materials removed from sewage during treatment. Different options for biosolids handling in Sydney, Australia, are compared using life-cycle assessment. Two key comparisons are made: of system scenarios (scenario one - local dewatering and lime-amendment; scenario two - a centralized drying system) and of technologies (thermal drying versus lime-amendment). The environmental issues addressed are energy consumption, global warming potential (GWP) and human toxicity potential (HTP). Scenario two would consume 24% more energy than scenario one. This is due to the additional electricity for pumping and particularly the petrochemical methane that supplements biogas in the dryer. A centralized system using the same technologies as scenario one has approximately the same impacts. The GWP and HTP of the different scenarios do not differ significantly. The assessment of technology choices showed significant differences. The ample supply of endogenous biogas at North Head Sewage Treatment Plant (STP) for the drying option for allows reductions, relative to the lime amendment option, of 68% in energy consumption, 45% in GWP and 23% in HTP. Technology choices have more significant influence on the environmental profile of biosolids processing than the choice of system configurations. Controlling variables for environmental improvement are the selection of biogas fuel, avoidance of coal-sourced electrical energy, minimization of trucking distances and raising the solids content of biosolids products.

  • (2012) Schulz, Matthias; Short, Michael; Peters, Gregory
    Journal Article
    Water supply is a key consideration in sustainable urban planning. Recycling may increase the expense and energy consumption of supply systems, raising optimisation questions. Ideally, detailed quantitative sustainability assessments are undertaken during the planning stage in order to inform the decision-making process. In reality, however, the significant time and cost associated with undertaking such detailed environmental and economic assessments is often cited as a barrier to wider implementation of these key decision-support tools, particularly for decisions made at the local or regional government level. In an attempt to counter this barrier of complexity, four water service providers in Melbourne (Australia) funded the development of a publicly available streamlined Environmental Sustainability Assessment Tool (ESAT). The tool is aimed at a wide range of decision-makers to assist them in broadening the type and number of water servicing options that can be considered for greenfield or backlog developments. ESAT consists of a simple user interface and draws upon life cycle inventory data to allow for rapid estimation of the environmental and economic performance of different water servicing scenarios. Scenario options can then be further prioritised by means of an interactive multicriteria analysis. The intent of this paper is to identify the key issues to be considered in a streamlined sustainability assessment tool for the urban water industry and to demonstrate the feasibility of generating accurate life cycle assessments (LCAs) and life cycle costings (LCCs) using such a tool. We use a real-life case study consisting of three separate scenarios for a planned urban development to show that this kind of tool can emulate LCA and LCC outcomes obtained by more detailed studies. We hope this kind of approach will support ‘sustainability thinking’ early on in the decision-making process, thereby encouraging more sustainable water and sewerage infrastructure solutions.

  • (2008) Balaei, Asghar; Motella, Beatrice; Dempster, Andrew
    Journal Article
    In the global positioning system (GPS), code division multiple access (CDMA) signals are used. Because of the known spectral characteristics of the CDMA signal, continuous wave (CW) interference has a predictable effect on the different pseudo random noise (PRN) spreading codes (unique to each satellite) depending on the Doppler frequency of the signal. The Doppler frequency for each signal is also predictable once the receiver position is known. As different satellite signals have different Doppler frequencies, the effect on the signal quality is also different. In this paper first the effect is studied analytically. The concept of an `exclusion zone` is defined and analyzed for each satellite. This exclusion zone, where that satellite should not be used due to interference degradation, is shown to be predictable for each satellite as a function of time. Using this prediction, the CW interference effect on the positioning quality of the receiver can be mitigated by ignoring the affected satellites within exclusion zones when performing position evaluation. The threshold beyond which a satellite should be excluded is then derived by studying the mutual effects of the geometry and the signal quality of that satellite on the positioning quality. Receiver autonomous integrity monitoring (RAIM) uses redundancy in measurements to perform an internal consistency check to see if all of the measurements are satisfactory. In this paper this technique is also used to mitigate the effect of CW interference on the positioning accuracy. Finally it is shown that the prediction of the exclusion zone for each satellite outperforms the RAIM algorithm in mitigation the effect of the interference when 5 satellites are visible. © 2007 Springer-Verlag.

  • (2007) Tappero, Fabrizio; Dempster, Andrew; Iwata, Toshiaki
    Journal Article
    To provide the proper positioning signal, global navigation satellite systems (GNSSs), need very accurate satellite on-board time references. For GPS, GLONAS and GALILEO, such time references are spaceborn atomic clocks. The augmentation/positioning system QZSS (Quasi-Zenith Satellite System) would need the same kind of accuracy. However, due to the high QZSS satellite visibility, a completely new kind of time reference method, where no on-board atomic references are needed, could be adopted. If an opportune ground location is chosen, QZSS satellites are fully visible for the whole orbital period. Therefore, a main time reference (atomic clock), located on the ground, could be kept synchronized to a inexpensive and compact time reference (VCXO) on board each QZSS satellite. In the following article, a new practical implementation of such a remote synchronization method is proposed and some of its problematic are discussed.

  • (2008) LI, Y; MUMFORD, P; RIZOS, C
    Journal Article
    A real-time GPS/INS integrated system based on a field programmable gate array (FPGA) platform has recently been developed at the Satellite Navigation and Positioning Laboratory, School of Surveying & Spatial Information Systems, University of New South Wales. Compared with an application-specific integrated circuit (ASIC) approach, the FPGA approach can shorten the research and development cycle. Its reprogrammable hardware provides a system design methodology of lower risk and maximum flexibility, being able to integrate a wide range of GPS and INS sensor packages. Tests demonstrate the feasibility of this type of system on an FPGA platform. Functionality of the system has been tested including; the stability and accuracy of the time synchronisation mechanism, the performance of the hardware and software architecture, the workability and accuracy of the algorithm, and finally, the capability of the integrated system to bridge GPS outages.

  • (2005) Woo, Daniel; Mariette, Nicholas; Helyer, Nigel; Rizos, Chris
    Journal Article
    Syren, a location-based, multi-speaker augmented audio reality installation was presented as a shipboard exhibit at the 12th International Symposium on Electronic Art in August 2004. It was conceived as a continuous 3-day spatial audio experience that augments the landscape through the Baltic archipelago with location-based audio media, spatialised through a 12- channel speaker array. As the ship tracks between Helsinki, Mariehamn, Stockholm and Tallinn, listeners on the upper deck hear sounds that are perceived to originate from geographic features. Our custom GIS is derived from electronic nautical charting information that includes coastlines, buoys and beacons. A handheld GPS provides both position and direction data that was used by a software system to drive parameters of the spatial audio presentation. The sound production for the artwork was created using the custom application that enabled the artist to place sound media in relation to a real-world map. An important component to this software was the ability to audition the audio experience without ever taking the journey.