A novel ex-situ bio-remediation process for perchlorate contaminated soil

A novel, ex-situ remediation process for perchlorate contaminated soil is reported in this study. This approach comprises washing the contaminated soil with water, followed by treatment of the wash water in a bioreactor. The treated water reused for the next batch of soil, and the cycle continued. The pilot-scale treatment unit comprising of a soil washing unit (0.75 m3) and a fixed-film bioreactor (140 L), both connected in series for continuous operation for a period of three months. The bioreactor was inoculated with a novel perchlorate reducing microbial consortium comprising Serratia marcescens (Gen bank no. HM751096), Bacillus pumilus (Gen bank no. JQ820452) and Micrococcus sp. (Gen bank no. KJ410671). The microbial activity was supported by glucose (glucose/perchlorate ratio = 5), and trace mineral solution. In a typical washing cycle, 2.5 g perchlorate (KClO4) spiked in 670 kg soil was completely removed in three washing cycles, that completed in 6.3 h consuming ∼360 L water. The pooled wash water containing perchlorate at 8.5 mg/L was treated completely in the bioreactor operated at 4.5 h HRT and -200 mV ORP. Compared with both in-situ and ex-situ remediation methods reported, the present approach has many advantages for treating perchlorate contaminated soil.