Anaerobic biodegradation of 1,4-dioxane by sludge enriched with iron-reducing microorganisms

The potential on anaerobic biodegradation of 1,4-dioxane was evaluated by use of enriched Fe(III)-reducing bacterium sludge from Hangzhou municipal wastewater treatment plant. The soluble Fe(III) supplied as Fe(III)-EDTA was more available for the Fe(III)-reducing bacterium in the sludge compared to insoluble Fe(III) oxide. The addition of humic acid (HA) further stimulated the anaerobic degradation of 1,4-dioxane accompanying with apparent reduction of Fe(III) which is believed that HA could stimulate the activity of Fe(III)-reducing bacterium by acting as an electron shuttle between Fe(III)-reducing bacterium and Fe(III), especially for insoluble Fe(III) oxides. After 40-day incubation, the concentration of 1,4-dioxane dropped up to 90% in treatment of Fe(III)-EDTA + HA. Further study proved that more than 50% of the carbon from 1,4-dioxane was converted to CO2 and no organic products other than biomass accumulated in the growth medium. The results demonstrated that, under the appropriate conditions, 1,4-dioxane could be biodegraded while serving as a sole carbon substrate for the growth of Fe(III)-reducing bacterium. It might be possible to design strategies for anaerobic remediation of 1,4-dioxane in contaminated subsurface environments.