Electric Resistance Heating System
The efficiency of in-situ remediation can be strongly limited due to low permeable or heterogeneous lithology`s, because many in-situ methods are based at mass transport of gasses and fluids. This mass transport is difficult in low permeable layers and selective in heterogeneous soils. Soil heating strongly effects the kinetics of many organic contaminants like benzene, trichloroethene and perchloroethene. Due to changes of vapor pressure and Henry Law many contaminants can be removed more rapidly and far more effectively.
Heating of low permeable clayey or loamy layers can be achieved effectively with the electrical based technique Electric Resistance Heating. Nocon has state-of-the-art experience at several European sites with engineering and operating the required systems. Actually Nocon has been primarily involved in all the European projects at which ERH has been used.
Basically the remedial system consists of electrodes, which are located within the impacted zone, and DPE wells, which are used to extract the contaminated gasses and fluids. Electrodes are energized and with a power supply unit, hence voltage is regulated between electrode couples. As electrical current is induced, soil heats up, as it acts as a resistor. Subsurface temperature rises until the boiling point of water or to the boiling point of an azeoptropic mixture (DNAPL and water), which in many occasions is lower then that of sole water or sole DNAPL. In this respect the heat propagation in it self tells us whether or not DNAPL has been removed sufficiently. The contaminated gasses and fluids or extracted and transported to cooling and treatment units. ERH has particularly added value for source zones at which DNAPL is suspected, if time is a strong driver and if soils are considered difficult to treat as for their low permeability.
One of our projects as performed in Sheffield (UK) with TerraVac UK as the main contractor has been awarded winner in the prestigious section "most innovative remediation method" for the remediation innovation awards 2008 at the brownfield briefing conference in London. For the project summary please visit our download section.