Thermal remediation: Cleaning up the site of the BT Kemi pesticide plant, Sweden

19 Nov 2021

Positioned just south of the Teckomatorp-Helsingborg railway, Sweden, the 2,082m2 site of the former BT Kemi plant is notorious for its contamination levels.

A beet processing factory turned pesticide production facility, soils are polluted with a complex mix of phenoxy alkanoic acids, chlorophenols, and chlorocresoles.

Now, over 40 years since the factory was demolished, McAuliffe remediation partners, McMillan McGee (MC2), are finalising the site’s long-awaited clean-up.

Through its patented Inductive-Thermal Dynamic Stripping Process (IT-DSP™), MC2 is on track to achieve a 5mg/kg remedial goal. All while minimising noise, odour and vehicle movements for local residents through in-situ treatment.

Here’s how they’re doing it:

The site conditions

MC2’s team is working with a material volume of 14,602m2. Geology transitions from fill, construction rubble, organic matter (mud and peat) to clay, silt, and sand, while depth to water sits at 4-6 mBGS.

Preliminary estimates showed approx. 2,000kg of mass in place. COCs are equal parts phenoxy alkanoic acids, chlorophenols, and chlorocresoles.

An enhanced thermal remediation system

IT-DSP™ is an intensive in-situ environmental remediation method, which uses induced eddie currents in steel pipe to heat the soil and groundwater to evaporate contaminants.

The process starts with an IT-DSP™ Thermal Remediation Bench-Scale Treatability Study, which has indicated a 300°C temperature would result in desorption and decomposition of the contaminants of concern. This allows for vapour-phase recovery.

The team designed the system to heat from surface to depth (6 mBGL). Features include:

• 235 heater wells placed on 3.5-meter centers
• A sheet pile wall surrounding the thermal zone
• A 50cm cellular concrete thermal cover

Because of the nature of the contaminants, a custom PTFE lined conveyance piping network and acid scrubber system were installed to help deal with anticipated hydrochloric acid production in the well field.

The 300°C temperature target is expected to be achieved in December, with peak power to the heaters exceeding 1,500 kW at points.

Multi-Phase Extraction

Once the soil heating system has volatised the pesticides/contaminants of concern, they are captured by the Multi-Phase Extraction system and treated.

This MPE system was modified for use with high temperature vapors and liquids, and was designed and installed to extract and treat the COCs. Effluent was treated using thermal oxidation.

The thermal inertia of the soil meant a reliable plant was vital to ensure continuous extraction of vapours, with MC2 monitoring the process closely.

The results

Site works will shut down this winter, with the 5mg/kg remedial goal on track to be achieved.

After decades of infamy as a local polluter in Teckomatorp, the BT Kemi site will blend back into its rural surroundings as a natural area.