Phytotoxicity complements chemical assessment for re-use and re-purposing of refinery wastes for soil amendment purposes after bioremediation.

The objective of this study was to assess the suitability of onsite re-use of mature compost for landscaping and tree mulching, produced from the bioremediation of oily sludge from the refinery. Compost samples from the co-composting process were analysed for a range of contaminants, including a human health risk assessment fractionation (HRAF) of the remaining petroleum hydrocarbons, as well as a phytotoxicity test. The chemical characterisation demonstrated that the process removed more than 94% of the original petroleum hydrocarbons from the sludge, and the removal rates were high at 1155 mg/kg/day. The HRAF demonstrated no residual risks, posed by the petroleum hydrocarbons present in the compost to human health if used on-site when compared to the relevant Australian environmental investigation levels (ILs). However, the phytotoxicity assessment demonstrated that the compost was toxic to germinating lettuce. The gap in the literature this study addressed was to provide an estimate of the LD50 and no effect concentration (NEC) for the compost using a standard plant bioassay containing a range of residual (aged) and bioremediated refinery process wastes, including petroleum hydrocarbons. The values estimated for LD50 and NEC were approximately 125 and 43 mg/kg, respectively for compost containing residual petroleum hydrocarbon fractions, filling a gap in the current literature which has limited data on standard toxicity values that can be used in determining and informing commercial remediation strategies and their outcomes with aged sludges. Phytotoxicity was shown to be an important complement to conventional analyses and HRAF data when characterising the sludge, and understanding its potential for re-use. The novelty of the study is that it highlighted a gap in the complementary use of chemical and bioassay analyses for evaluating refinery waste remediation endpoints, which has potential for broader application to other projects.

Evaluating treatment pathways for managing packaging materials from construction of a solar photovoltaic power station.

The reuse of end-of-life packaging materials (EOLPM) on site represents, particularly for remote sites, an important contribution to sustainable business practice because it provides a higher value end use when used to develop on-site mulch to enable soil improvement, thereby reducing transport emissions (in relation to the least preferred option of off-site disposal to landfill), lowering costs and offering employment to local contractors. The objective of the study was to demonstrate a local application of the circular economy for EOLPM to a utility-scale solar electricity (USSE) construction site. Although the principles of the circular economy could not be applied fully at the site, it was possible to demonstrate that EOLPM can be reused on site for a higher value than off-site disposal would give. Given the common occurrence of these materials in the rapidly growing renewable energy sector, this represents an important step forward for the sector internationally. The study is the first of its type reported, and the methods used for characterization of the EOLPM included a range of organic and inorganic chemical analyses and phytotoxicity testing, which were followed by an environmental and financial cost-benefit analysis. The selected option of on-site reuse of the materials as a mulch had a global warming potential of 58 t CO2e compared with the business as usual option (transport to landfill) of 3145 t CO2e. The results also demonstrated the broader potential for using EOLPM from USSE sites for soil improvement at remote locations rather than transporting these materials off site for disposal or reuse.

Bioremediation of diesel from a rocky shoreline in an arid tropical climate.

A non invasive sampling and remediation strategy was developed and implemented at shoreline contaminated with spilt diesel. To treat the contamination, in a practical, cost-effective, and safe manner (to personnel working on the stockpiles and their ship loading activity), a non-invasive sampling and remediation strategy was designed and implemented since the location and nature of the impacted geology (rock fill) and sediment, precluded conventional ex-situ and any in-situ treatment where drilling is required. A bioremediation process using surfactant, and added N & P and increased aeration, increased the degradation rate allowing the site owner to meet their regulatory obligations. Petroleum hydrocarbons decreased from saturation concentrations to less than detectable amounts at the completion of treatment.

A safe, efficient and cost effective process for removing petroleum hydrocarbons from a highly heterogeneous and relatively inaccessible shoreline.

A rocky, intractable and highly heterogeneous, intertidal zone, was contaminated from a diesel fuel spill that occurred during refuelling of a grader used in road construction, on an operational mine's shiploading facility. A practical, cost-effective, and safer (to personnel by avoiding drilling and earthworks), and non-invasive sampling and remediation strategy was designed and implemented since the location and nature of the impacted geology (rock fill) and sediment, precluded conventional ex-situ and any in-situ treatment where drilling would be required. Enhanced biostimulation with surfactant, available N & P (which were highly constrained), and increased aeration, increased the degradation rate from no discernable change for 2 years post-spill, to 170 mg/kg/day; the maximum degradation rate after intervention. While natural attenuation was ineffective in this application, the low-cost, biostimulation intervention proved successful, allowing the site owner to meet their regulatory obligations. Petroleum hydrocarbons (aliphatic fraction) decreased from ∼20,000 mg/kg to <200 mg/kg at the completion of 180 weeks of treatment.

Environmental liability and life-cycle management of used lubricating oils.

Used oil handling, as a business, requires an extensive understanding by management that environmental liabilities exist through its supply chain. Findings from a review of the legal requirements of operating a used oil handling business were: understanding the transfer of ownership of used petroleum hydrocarbons is critical to any such business and how this is documented; used oil handlers are responsible for providing training to their staff, including site personnel and any third party waste contractors, and for communicating best practice procedures relating to the management of used petroleum hydrocarbons to all those individuals and organisations involved in business relationships that the used oil handling companies have; used oil handlers should audit the performance of any third party contractors that it engages to conduct work on behalf of its customers. Hypothetical situations of a company planning to enter the used oil handling market are described in relation to petroleum hydrocarbon wastes it handles to illustrate the range of potential liabilities. Companies proposing to establish a used oil handling business should ensure that they provide accurate advice to its employees, its customer's employees and to its third party contractors, all of which may be responsible for handling used petroleum hydrocarbons as part of the service it intends to provide, and that it has a well documented system addressing how environmental issues are managed.

An application of permeable reactive barrier technology to petroleum hydrocarbon contaminated groundwater.

A funnel and gate permeable reactive barrier was designed and built to treat groundwater contaminated with dissolved phase toluene. ethyl benzene. and xylene and n-alkanes in the C6-C36 fraction range. Removal efficienicies for the funnel and gate system varied from 63% to 96% for the monocyclic aromatic hydrocarbons. Average removal efficiencies for C6-C9, C10-C14, and C15-C28 fraction ranges were 69.2%, 77.6% and 79.5%. respectively. The lowest average removal efficiencies were 54% for the C29-C36 n-alkane fraction. The overall average removal efficiency for the funnel and gate system towards petroleum hydrocarbons present in the groundwater was 72% during the 10 month period over which the data were collected, and has allowed relevant water quality objectives to be met.