A portion of a Superfund site is impacted with perchlorate in both the vadose zone and in ground water at 120+ feet. I helped design and evaluate a large recirculation pilot test for biological treatment and migration control of the plume. Perchlorate concentrations were reduced from 2000 ug/l to < 100 ug/l at the first two monitoring points in the test cell in less than six months, and concentrations dropped to < 300 ug/l throughout the entire 600 ft section of plume being treated (Leo et al. 2010). The anti-biofouling system used on the injection well performed admirably.
Concentrations at the extraction well and first two monitoring wells declined to the point where the extraction well has been shut down. This was even after a pilot test flush of the vadose zone in the source area was performed in late 2010 and high levels of perchlorate were flushed into ground water (Leo et. al. 2010).