[en] This conference is an established event covering a broad range of specialty areas in environmental sciences and radiation, thermal, and other environmental pollutant effects on living organisms and biological materials. It particular covers aspects of contaminated site assessment, management and remediation. The proceedings include the program list of speakers with abstracts for the 265 scientific and 32 poster presentations.

[en] Site-Specific Trigger Levels (SSTLs) and Remediation Criteria values for signature chemicals in groundwater have been developed for a coastal Alumina Refinery. The values have been developed to protect sensitive receptors in the adjacent ocean in the following manner: SSTLs are to be applied to sentinel wells (located near the site boundary on the groundwater migratory path to the respective marine receiving environments). Remediation criteria are to be applied at the source zone wells. In order to achieve the above outcomes, the following steps were undertaken: Modelling the fate and transport rates of signature chemicals from the source to the sentinel wells, and from the sentinel wells to the ocean, and calculating a diffusion, dispersion and advection coefficient. Measuring the geochemical interactions of the impacted groundwater with the saline intrusion zone boundary (by direct laboratory experimentation) to assess the magnitude of chemical precipitation, followed by calculating a precipitation coefficient for each signature chemical. Using an existing hydrodynamic model to understand the tidal and current effects on discharged chemicals in conjunction with flux rates from the fate and transport modelling and conceptual site model to calculate the reduction in concentrations between the seabed at the point of discharge and the receptors at the point of exposure. Establish acceptable site-specific ecotoxicological and human health exposure levels in the adjacent marine environment. Using the various attenuation coefficients, back-calculating the signature chemical concentrations in the sentinel wells and source wells that would attenuate to an acceptable level prior to discharging into the receiving marine environment. (author)

[en] For many decades in environmental cleanup, the question of “How clean is clean enough?” remains at the forefront of decision making in Australia and New Zealand, North America, Europe, and more recently in China. Using a systematic three-tiered risk-based method, the ASTM risk-based corrective action (RBCA) approach has been widely adopted worldwide as a reasonably defensible way to establish cleanup goals for remediation of contaminated sites. Based on ASTM E1739-95 standard guides for RBCA applied at petroleum release sites (and for chemical release), hundreds of sites have been successfully remediated to risk levels that are protective of both human health and ecological systems. (author)

[en] The challenges of operating traditional per- and poly-fluoroalkyl substances (PFAS) fixed bed adsorbers has driven innovation to overcome the problems associated with these types of systems. Issues can include high plant cost due to the requirement to have standby capacity, unexpected breakthrough of PFAS due to microbiological fouling or undetected changes in PFAS concentration, and difficulty ensuring that PFAS is removed to low enough levels throughout the life-cycle of the adsorber; especially in the presence of co-contaminants that are known to impact adsorption. Furthermore, scaling a treatment plant up from bench scale or pilot scale to full-scale is difficult to achieve with a high level of confidence. InSite has invented a PFAS water treatment process (patent pending) based on adsorption of PFAS on a proprietary adsorbent called InTreat™. The process comprises a series of continuous stirred-tank reactors (CSTRs) and a filtration system, which completely eliminates the issue of unexpected breakthrough of PFAS. This is achieved by continuously dosing the liquid InTreat™ in direct proportion to the feedwater at a predetermined rate. The dose rate can be determined in bench scale tests beforehand, and a conservative safety margin can be applied to cope with anticipated PFAS concentration variations in the feedwater. Currently there is no means available to detect PFAS concentration on-line or in the field – laboratory results typically take 4-5 working days. InSite has developed a means of detecting the presence of the InTreat™ amendment in the feedwater in real time, and by inference are able to give ‘treatment assurance’, which further adds to the reliability of the treatment process. In this study PFAS impacted groundwater from a confidential site was obtained by pumping from bores and by collecting flushing water produced during well development (this water contained colloidal clay, and has higher salinity than the natural groundwater). Several experiments were performed to evaluate the effectiveness of the InTreat™ process to remove PFAS to non-detect; at standard detection levels, and super-trace levels. The impact on treatment effectiveness of salinity variation and the presence of heavy metal co-contaminants was also tested. (author)

[en] Rarely do typical site remedial Conceptual Site Models demonstrate a perfectly defined plume, contained to homogeneous soil conditions on a flat structure-less site. However, with normal variable site conditions both above and below ground, multiple remedial methods are usually available, giving the consultant a choice of technologies to attain the remedial goals. At some sites, challenging constraints both limit the remedial technology choices and require specific application methods to overcome the site’s challenges. This abstract presents the remedial evaluation case studies for two such sites. Case study 1 is an active retail service station site in south-east Queensland, multiple site conditions such as shallow groundwater, potential acid sulphate soils and a residential property within close proximity to the hydrocarbon source area provided technical and non-technical limitations to our remedial choices. Case study 2 is an active retail station near Sydney evaluated for multiple technologies to clean up a release that had spread significantly downgradient. Soil conditions were fine grained clay to silt over weathered to unweathered shale which results in very poor recovery. Due to the poor hydrologic recovery, planned construction activities and the current site infrastructure, any remedial method chosen was going to be challenging to implement successfully. (author)

[en] The occurrence, fate and transport of PFAS in the environment differ in some important ways to many more common contaminants. As an emerging contaminant, it is only more recently that they have been assessed in detail at a range of sites. The aim of this presentation is to discuss their occurrence, fate and transport drawing on a range of case studies where PFAS has been assessed in detail as the primary contaminant of concern. The presentation outlines where PFAS are found and at what concentrations in a range of media including soil, groundwater, surface water, vegetation, produce and biota; the primary methods of PFAS transport; and how PFAS concentrations change over time in media, particularly in groundwater and surface water. The presentation is based on data collected from several sites where a large range of media has been sampled. They include those where regular monitoring has been ongoing for more than two years. The findings will be discussed in the context of designing an assessment program when investigating PFAS impacts. (author)

[en] The chlorinated solvent stabilizer 1,4-dioxane (DX) has become an unexpected and recalcitrant groundwater contaminant at many sites. Increasing regulatory interest and promulgation of standards over the last several years has led to greater awareness among consultants, vendors and facility owners. Chemical characteristics of DX, such as miscibility and low sorption potential, enable it to migrate at least as far as the chlorinated solvent from which it often originates. This mobility and recalcitrance has challenged remediation professionals to redesign existing treatment systems and monitoring networks to accommodate widespread contamination from this previously unidentified compound. Furthermore, remediation technologies commonly applied to chlorinated solvents, such as extraction and air stripping or in situ enhanced reductive dechlorination, are relatively ineffective on DX removal. These difficulties in treatment have required the industry to identify, develop and demonstrate new and innovative technologies and approaches for both ex situ and in situ treatment of this emerging contaminant. (author)

[en] Full text: Introduction - The biodegradation of petroleum is an oxidative process which requires the use of terminal electron acceptors (TEAs) and ultimately produces carbon dioxide. If petroleum soil contamination is shallow, oxygen is the preferential TEA used by microbes. At deeper locations, oxygen is scarce, and microbes resort to TEAs: sulfate, nitrate, and oxidized forms of iron and manganese. As these electron acceptors are depleted in the soil, microbes revert to a process called methanogenesis, which produces methane (CH₄) and carbon dioxide (CO₂), and does not require external electron acceptors. As methane gas moves upwards in the unsaturated zone, it encounters ambient oxygen and under such conditions is used as a carbon source by methanotrophic (methane oxidizing) microorganisms, producing CO₂. Methods - The measurement of SZNA rates is conducted by performing mass balances of biodegradation by-products or reactants in the dissolved phase on in the vadose zone. LNAPL losses associated with electron-donors in groundwater are estimated based on the groundwater flux of such reactive species. For SZNA losses associated with the vadose zone, three methods exist: The Gradient Method estimates diffusive fluxes based on soil gas concentrations and in situ effective diffusion coefficients; The Dynamic Closed Chamber Method (DCC) is a short-term soil gas flux measurement (typically of c) done at the ground surface, based on measured changes in concentration on a closed chamber emplaced directly over the soil; and the passive CO₂ flux traps (Traps) estimate the longterm CO₂ flux at ground surface over multiple days using passive sorbents, followed by laboratory analysis of total and carbon-isotopic corrected CO₂ fluxes to determine the fossilfuel related fraction. This presentation will describe these different methods, including the assumptions made on each method, their best use, advantages and disadvantages. Case studies exemplifying their use and typical results will be described, including validation studies comparing results from multiple methodologies. Results and discussion SZNA - processes are consistently present at most LNAPL contaminated sites. Quantification of these processes reveals that LNAPL loss rates are in the range from 1000s to 10,000s of kg/Ha/yr. Most of these LNAPL losses are expressed in the vadose zone. This is the result of mass transfer limitations in the groundwater electron acceptor supply at sites, and also due to the volatility of the methanogenesis by-products CH₄ and CO₂. Different vadose-zone methodologies have been validated in laboratory experiments, and have measured SZNA rates of similar magnitude at field sites. Conclusions - SZNA-related processes are present at most LNAPL contaminated sites. Given the availability of methods to conduct SZNA measurements, and the significant rates measured at sites, SZNA is becoming a cornerstone tool of the LNAPL practice, from site characterization to final remedy. This includes screening-level mapping of source zones, informing the conceptual site model, quantifying NSZD rates at field sites, and evaluating and comparing remedies. NSZD itself has been recognized as a potential remedy for some low risk sites, provided other conditions are met (such as lack of LNAPL mobility). (author)

[en] The management of groundwater quality within Victoria is underpinned by the concept of protecting the existing and potential beneficial uses of the resource. Groundwater is considered to have become polluted when land or water management actions result in deterioration in groundwater quality. Where groundwater has become polluted, the quality must be remediated to the extent practicable in order to restore the beneficial use. Consistent with this policy, landfill and wastewater treatment facilities are deemed to be scheduled premises that require groundwater monitoring and evaluation programs for the purposes of identifying any changes in groundwater quality, and if there are changes, the extent and degree of contamination. On the irrigated Riverine Plains of northern Victoria, the brackish nature of most shallow groundwater, the presence of high intensity irrigated agriculture, and the types of point source waste being managed, means that the risks of compromising existing beneficial uses are generally considered to be low and hence low intensity monitoring programs are commonly considered to be sufficient. However obtaining conclusive evidence that groundwater contamination is or isn’t occurring is then challenged because of the temporal and spatial variability in background water quality data, the heterogeneous nature of the upper Shepparton Formation, and because lateral gradients are flat and influenced locally by land and water management activities. Similar challenges are faced by environmental auditors who are expected to offer clear and consistent advice on suitable monitoring and reporting frameworks for scheduled premises. (author)

[en] In the past, the assessment and management of groundwater contamination has been driven by contaminant concentrations, but concentration data alone are sometimes not sufficient to fully understand the behaviour of a plume over time. Mass flux and mass discharge estimates can help characterise and remediate groundwater contamination, and their inclusion in remedial design and optimisation may ultimately result in time- and cost-efficient groundwater remediation programs. The CRC CARE guidance illustrates how flux concepts, tools and measurements can be used to assess and manage groundwater contamination. Mass flux and mass discharge estimates are typically used to complement concentration-based assessments, rather than to replace them. (author)