Microbially Driven Fenton Reaction for Degradation of the Widespread Environmental Contaminant 1,4-Dioxane

The carcinogenic cyclic ether compound 1,4-dioxane is employed as a stabilizer of chlorinated industrial solvents and is a widespread environmental contaminant in surface water and groundwater. In the present study, a microbially driven Fenton reaction was designed to autocatalytically generate hydroxyl (HO•) radicals that degrade 1,4-dioxane. In comparison to conventional (purely abiotic) Fenton reactions, the microbially driven Fenton reaction operated at circumneutral pH and did not the require addition of exogenous H2O2 or UV irradiation to regenerate Fe(II) as Fenton reagents. The 1,4-dioxane degradation process was driven by pure cultures of the Fe(III)-reducing facultative anaerobe Shewanella oneidensis manipulated under controlled laboratory conditions. S. oneidensis batch cultures were provided with lactate, Fe(III), and 1,4-dioxane and were exposed to alternating aerobic and anaerobic conditions. The microbially driven Fenton reaction completely degraded 1,4-dioxane (10 mM initial concentration) in 53 h with an optimal aerobic-anaerobic cycling period of 3 h. Acetate and oxalate were detected as transient intermediates during the microbially driven Fenton degradation of 1,4-dioxane, an indication that conventional and microbially driven Fenton degradation processes follow similar reaction pathways. The microbially driven Fenton reaction provides the foundation for development of alternative in situ remediation technologies to degrade environmental contaminants susceptible to attack by HO• radicals generated by the Fenton reaction.