Biodegradation of nitroaromatic compounds, interrelationships between catabolism of nitrophenols and nitrobenzene

Abstract

This thesis describes biological mechanisms of degradation of nitroaromatic compounds and more specifically the interrelationships between biodegradative metabolism of nitrophenols (NPs) and nitrobenzene (NB). An initial study on conversion of NB to NPs by electron beam provided the impetus for the biodegradative study.

Electron beam irradiation of aqueous solutions containing 15-30 mg/L of NB at 60kGy dose removed 78% of the contaminant. Three mono-NPs were detected as byproducts of electron beam treatment of NB. A mixed culture which degraded both NPs and NB was enriched from municipal activated sludge using a mixture of three mono-NPs as sole carbon, nitrogen and energy sources. Bacterial growth and degradation rate could be increased by supplementing the medium with 0.1% YE. The mixed culture degraded both the residual NB and the NP products in the electron beam treated samples, and this observation led to the conceptual design of a two-stage electron beam microbial process for degradation of NB. Percentage removal of NB in this two-stage treatment, increased with increasing electron beam dose.