Passive Systems

The construction of passive treatment systems beneath contaminated sites represents a relatively new method for in-situ remediation of contaminated groundwater.

Permeable reactive barriers

Permeable reactive barriers are installed underground using special foundation techniques. They are filled with reactive or adsorbing material, e.g. iron sponge, intercepting the contaminants from the groundwater. The treatment process takes place along the entire surface of the barrier (CRB: Continuous Reactive Barrier).

The major disadvantage of the continuous reactive barriers is that in case of large aquifers great amounts of costly reactive material have to be installed reducing the economic efficiency of the remediation. Besides, overdimensioning of the reactive zone may result in insufficient treatment performance. To avoid that, funnel-and-gate systems have been developed.

Funnel-and-Gate Systems

For funnel-and-gate systems funnel-shaped cut-off walls are erected directing the groundwater to one or a series of gates. There, the groundwater is treated using for example activated carbon or bioreactors. The groundwater passes the gate following the natural gradient without pumping. After treatment, the cleaned water re-enters the aquifer downstream the gate.

In the past years, several of these passive treatment systems have been installed in Germany and the world. BAUER Environment Group has gained wide experience from four innovative projects and the erection of the world’s largest funnel-and-gate system in Munich.