Comparative bioremediation of carbofuran contaminated soil by natural attenuation, bioaugmentation and biostimulation

This study investigated the effect of bioremediation treatments including natural attenuation, bioaugmentation, combined biostimulation and bioaugmentation and biostimulation on carbofuran degradation in rice field soil. Experiments were conducted in soil microcosms at the initial carbofuran concentration of approximately 20 mg kg−1 soil. Mixed-cultures isolated from soil that was collected from rice fields with a history of carbofuran application were used as inoculum in bioaugmentation technique in comparison to a specific carbofuran degrader, Burkholderia cepacia PCL3. Sludge from a production process of renewable energy including hydrogen (HY), ethanol (ET) and methane (ME) were used as organic amendments in the biostimulation technique. The shortest half-lives (t1/2) of carbofuran (1.60 days) was observed in soil inoculated with both mixed-cultures and PCL3 followed by soil inoculated with PCL3 (3.62 days) and soil inoculated with mixed-cultures (4.02 days), respectively. HY was the most effective amendment to biostimulate carbofuran degradation in soil giving a short t1/2 of 9.53 days followed by ET (t1/2 of 12.68 days) and ME (t1/2 of 13.24 days). Combined bioaugmentation and biostimulation provided the effective carbofuran degradation with the short t1/2 in soil of 2.20-4.90 days when PCL3 or PCL3 together with mixed cultures; was used as the inoculum while the prolonged t1/2 of 7.08-9.37 days were observed when only the mixed cultures was used as the inoculum.