Groundwater from a xylene-contaminated aqui-above ground. Adsorption of aromatic hydrocarbons to fer was enriched in the laboratory in the presence of hydrophobic materials in the aquifer can exacerbate the toluene, xylenes, ethylbenzene, and benzene. A pure culproblem and lead to exceedingly long treatment times ture that degrades toluene and m-xylene under nitrateand high costs. In some cases, in situ biodegradation of reducing conditions was isolated. Fatty acid analysis, 16S soils contaminated with aromatic hydrocarbons may be rRNA sequencing, and morphological traits indicate that a less expensive and more effective alternative to comthe isolate was a strain of Azoarcus tolulyticus. The kinetics of toluene degradation under nitrate-reducing condimonly used physical methods. Aerobic biodegradation tions by this isolate was determined. Nitrate reduction of aromatic compounds has been studied in detail; the does not proceed beyond nitrite. Nitrate and toluene are microorganisms responsible for degradation have been substrate limiting at low concentrations, whereas tolucharacterized, and many of the enzymatic and genetic ene, nitrate, and nitrite are inhibitory at high concentraregulatory mechanisms have been determined (Smith, tions. Several inhibition models were compared to experimental data to represent inhibition by these substrates.
1994). However, due to the low solubility of oxygen in
A kinetic model for toluene and nitrate degradation as water it is not always possible or economically viable well as for cell growth and nitrite production was develto aerate a contaminated groundwater aquifer.
oped and compared to experimental data. The results of Anaerobic degradation of aromatic compounds was this work may find important application in the remediaonce thought to be impossible. Recently, there have tion of groundwater aquifers contaminated with aromatic hydrocarbons.