Virgin (Fe0) and microbially regenerated (Fe2+) iron turning waste for treating chlorinated pesticides in water

This work investigated the applicability of iron turning waste as filtration media for treating mixture of organochlorine pesticides (OCPs) in water and the ability of non-pathogenic bacterium Shewanella oneidensis to regenerate the exhausted iron turning waste for reuse. In batch experiments, 1.5 x 10(4) mg/L of iron turning waste efficiently removed (>= 85%) five out of six pesticides in 200 mL of water (20 mu g/L for each pesticide) in 10 min. Increasing the iron dose from 2.5 x 10(3) to 1.5 x 10(4) mg/L enhanced the removal of heptachlor, endosulfan, dieldrin, and endrin by 5.7, 13.2, 23.3, and 39.4%, respectively, whereas lindane and dichlorodiphenyl trichloroethane removal was comparable when using 2.5 x 10(3) and 1.5 x 10(4) mg/L of iron. Better pesticide removal (except lindane) was achieved when the initial concentration of each pesticide was higher (20 mu g/L versus 1 mu g/L) in the solution. Acidic pH favored OCPs (except endosulfan) removal. S. oneidensis efficiently reduced 80 +/- 5% of dissolved ferric iron (Fe3+) to ferrous iron (Fe2+) in 72 h. Microbially regenerated Fe2+ iron removed all six OCPs in water efficiently (52-91%) and at similar levels as provided by virgin iron turning (38-100%). Lindane, endosulfan, and dieldrin removal increased 4-fold using S. oneidensis regenerated iron compared to exhausted iron.