Biological approach of chlorinated solvents

The alternative for soil injections is the application of permanent filters to extract groundwater and infiltrate it back into the soil after inoculation with DHC and nutrients. The process of extraction and infiltration can be installed entirely underground, in order to prevent nuisance at street level.

For a project in The Hague, 1 extraction source and 5 infiltration sources were used. During this project, in 2 years’ time, the soil volume was provided with DHC and nutrients, as a result of which a colony of bacteria incorporated and the degradation process took place.

The dehalococcoides entheogens bacteria (DHC), required for the degradation process, are grown in an own developed breeder reactor through a cooperation between T&K and Bioclear Earth.

The breeder reactor, with a volume of 10,000 litres, achieves a breeding density of 3 x 10⁸ cells/ml. The cultivation is transported in oxygen tight containers to the decontamination location and injected into the soil, with nutrients, on-site. The combination of cultivation and nutrients causes the DHC quantity to quickly increase and the biological degradation of the contamination will start.

This method is excellently suitable for situations where previously the biological degradation in the soil was not at all demonstrable. It was proven that this approach also works under non-optimal field conditions. The huge volume of the breeder reactor allows us to quickly inoculate a significant soil volume, ensuring that the degradation process will start immediately and the entire degradation process is followed.

In order to support the biological degradation process, nutrients are added to the soil. The nutrients of T & K Service are composed by means of an own recipe and contain both fast, medium and slowly working carbon sources. Our nutrients contain 2 times as much carbon source (TOC) as the usual nutrients. This guarantees longer activity of the DHC and reduces the risk that soil injections must be performed for a second time, for the administering of nutrients.