Levakov, I., Z. Ronen, and O. Dahan.
Journal of Hazardous Materials 369:439-447(2019)

In Israel, perchlorate has been found at high concentrations in the vadose zone (up to 30,000 mg/L) and groundwater (up to 800 mg/L) underlying former industrial waste ponds. A proposed perchlorate-reduction method that utilizes the high degradation potential of shallow soil and the high mobility of perchlorate across the deep unsaturated zone combines recurrent pumping and application of contaminated groundwater amended with an electron donor to the shallow soil layers. As a result, perchlorate biodegrades in the upper soil and the treated water drains through the unsaturated zone, flushing the pollutant toward the water table, where it is immediately pumped back to the surface for further treatment through a cyclic process. This treatment approach was implemented in a one-yr full-scale unsaturated zone (40 m) pilot study. Results showed a daily reduction in perchlorate concentration from 800 mg/L to practically zero. A total of ~330 kg of perchlorate was reduced during the experiment. Competitive reduction (iron and sulfate) and soil acidification were found to be limiting factors.