Design, construction, and operation of tailored permeable reactive barriers

In Germany, nine permeable reactive barriers (PRBs) for passive in situ remediation of contaminated groundwater have been erected over the last 3 to 4 years (in Bernau, built 2001; Bitterfeld, 1999; Denkendorf, 2000; Edenkoben, 1998 and 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 what is probably one of today's largest funnel-and-gate (F and G) systems (approximately 450 m long, equipped with six gates). This paper provides an introduction to German PRB projects, focusing on design and engineering features as well as on some major first outcomes regarding contaminant destruction efficiency and long-term performance, where available. It shows the prevalence of F and G and related systems, which are, predominantly equipped with specially positioned or designed funnels and/or gates (for example, relatively flat gates installed close below ground level, or reactors receiving passively or even actively diverted or lifted groundwater). Different zero valent iron types or activated carbon are the reactive materials exclusively applied in German PRBs to treat chlorinated volatile organic carbons and polycyclic aromatic hydrocarbons (PAHs), though a biological treatment zone to degrade PAHs is planned to be set up at Offenbach, and different alternative innovative materials are currently being tested in a semitechnical scope at Bitterfeld and elsewhere.