A biotic Fe0-H2O system for nitrobenzene removal from groundwater

Batch experiment was conducted to evaluate the capability of a biotic Fe0-H2O for nitrobenzene (NB) removal from groundwater. In this study, iron dosage was 0.25 g L−1 throughout the whole experiment and the Fe0-H2O system was amended with 180 mg L−1 VSS of mixed culture. The biotic system was tested at low concentrations (50 mg L−1 as COD) of organic substrates (e.g., ethanol, glucose and sodium acetate) and different concentrations of sulfate, nitrate and dissolved oxygen. The bio-iron system exhibited higher NB removal rate and more AN production. The increasing order of efficiency of tested substrates was: glucose > sodium acetate > ethanol. A complicated enhancement from oxygen was obtained, with 100% of NB removal rate and without any AN accumulation in the solution amended by dissolved oxygen. Sulfate and nitrate functioned as inhibitors since they competed with NB for electron donors (H2), and nitrate showed more significant suppression on NB removal as compared to sulfate. AN elimination occurred during both sulfate-reducing and nitrate-reducing processes and microorganisms got extra reduction capacity from the degradation of AN to reduce nitrate and sulfate, causing the mineralization of NB under anaerobic or anoxic conditions. It suggested that the bio-iron treatment could function as a simplified process for the remediation of groundwater contaminated by combined NB and sulfate, nitrate.