PRB technologies in Germany: Recent progress and new developments

In Germany, nine pioneering permeable reactive barriers (PRB) for passive in situ remediation of contaminated groundwater have been erected over the last 3-4 years, e.g., in Bernau (built 2001), Bitterfeld (1999), Denkendorf (2000), Edenkoben (1998, 2001), Karlsruhe (2000), Oberursel (2002), Reichenbach (2000), Rheine (1998) and Tübingen (1998), all revealing interesting design and engineering features. At the Edenkoben site, one can find one of today's probably largest funnel-and-gate (F&G) systems (appr. 450m long, equipped with six gates). This contribution provides an introduction to German PRB projects focusing on design and engineering features as well as on some first major outcomes regarding the destruction efficiency and long-term performance, where available. It is shown that F&G and related systems prevail, predominantly equipped with specially positioned or designed funnels and/or gates, e.g., relatively flat gates installed closely below ground level, or reactors receiving passively or even actively diverted/lifted groundwater. Different zerovalent iron (ZVI) types or activated carbon are the exclusively applied reactive materials in German PRBs to treat chlorinated volatile organic carbons (cVOC) and polycyclic aromatic hydrocarbons (PAH), though a biological treatment zone to degrade PAHs is planned to be set up at Offenbach, and different alternative innovative materials are currently tested in a semi-technical scope at Bitterfeld and elsewhere.