Coal tar contaminated soil at site in NSW

Monday, 03 October, 2005

Innova Soil Technology has developed a thermal desorption process (DFTD) for the remediation of contaminated sites. The process is suitable for treating all organic-based contaminated soils including those contaminated with petroleum hydrocarbons, tars, pesticides, transformer oils and other chemicals. The process is fully mobile and can process up to 1000 tonnes of soil per day.

The process will be used for a proposed project in Newcastle, NSW, to remediate its coal tar contaminated soil and allow for its reuse as clean fill on the site. Approvals have recently been granted and the project will soon commence.

A trial at the site was recently conducted to remediate a 6000 tonne stockpile of coal tar contaminated soil. The trial was implemented to establish plant operating procedures.

Specific aims of the trial included: assessing the ability of the technology to process the heavily PAH impacted soils. (Typical thermal desorption plants are limited to 1% hydrocarbon contamination in soils, in some cases this soil contained over 3% hydrocarbon); proving that remedial objectives for the treated soil - 'industrial site reuse' - as set by the NSW EPA accredited auditor, could be met by the technology, despite the high hydrocarbon loading; and assessing the suitability of using an alternative fuel compared to conventional burner fuel (diesel) as an energy source for the process.

The results of the trial indicated that the Innova DFTD process successfully processed and treated the contaminated soil, despite the high hydrocarbon levels in the feed soil of 1.35 to 3.1 wt% (see TPH levels Table 1).

To allow smooth processing of the soils, the plant throughput rate was slowed from 30 to 15-18 tonnes per hour and water was injected in the converter chambers. These two measures ensured the plant could easily handle the high energy associated with the high hydrocarbon level in the soil.

The treated soil analysis results showed that there was a massive reduction in soil contaminant levels for all hydrocarbons. In all cases, the soil contaminant levels were reduced to non-detectable or near non-detectable levels. The soil clean-up level for TPH of 1000 ppm was easily met. Similarly, the clean-up level for PAHs of 100 ppm was also easily met as product samples showed PAH levels to be non-detectable to 9.5 ppm.

The process burners were successfully operated using both the conventional burner fuel (diesel) as well as an alternate fuel - the latter requiring some minor burner re-tuning. The trial confirmed that the fuels were almost interchangeable, resulting in no operability issues or changes to process emissions. Indeed, process emissions were low for the entire trial signifying the efficiency of the hydrocarbon contaminant removal and conversion.

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