Reactive Barrier in Fazerila site, Vantaa

Ekokem-Palvelu carried out a pilot of purification of groundwater contaminated by chlorinated solvents by in situ permeable reactive barrier (PRB) in Fazerila site, Vantaa 2003. In PRB polluted groundwater flows through reactive material that is placed underground. Material of PRB has been designed to purify the contaminated groundwater during its flow through the PRB. Trichloroethene was degraded in pilot 100 %.

The plume of the Fazerila site was 50 m wide. Despite several studies that had been conducted since 1996 the source or cause contamination was not found, but had been any case cut off. PRB requires no over ground structures. The length of barrier structure is 12 m, thickness 1.5 m and depth down till bedrock 10 m.

The reactive material was installed to ground by an innovative method that is specifically designed for PRB in USA. The very steep trench was simultaneously backfilled by biologically degradable viscous sludge as excavation passed on. When the excavation of trench was finished a dense ferric-rich reactive material was backfilled on top of less dense sludge. Gravity forced the reactive material to settle on the bottom of trench. The sludge on top layer was degraded to water and harmless gas.

PRB was placed downstream from source and perpendicular to groundwater flow pattern in order the capture the entire plume. The reactive material of permeable barrier causes contaminants of water to degrade. PRB is left to ground permanently. The purification of plume produces no waste. Also the over ground activities are not affected. The reactive material is consumed slowly and the impact to water lasts years, possibly decades. The PRB project carried out by Ekokem-Palvelu was first of its kind in Finland. Suitable PRB solution can be found for most pollutants. The positive results of the pilot make a flying start for future implementation of PRB in Finland.