BTEX aerobic degradation

Benzene is one of a group of related aromatic monocyclic hydrocarbons (BTEX—benzene, toluene, ethylbenzene, and xylene), and since these are water soluble, there has been concern for their dissipation and persistence in groundwater under both aerobic and anaerobic conditions. Although aerobic growth at the expense of benzene was established many years ago, the pathway for its degradation was established only much later. The aerobic degradation of benzene by bacteria is... 

Salanitro (1993) has summarized the aerobic degradation rates for BTEX in laboratory subsoil-groundwater slurries and aquifers. The data indicate that decay rates for benzene are highest (19-52% per day) for benzene concentrations less than 1 ppm when initial dissolved oxygen levels are about 8 ppm. Rates are significantly reduced (0-1.1% per day) when benzene levels are 1-2 ppm, and no degradation was observed when benzene levels were greater than 2 ppb. 

Ex situ bioremediation relies on management of groundwater flow, with optimization of retention times in the bioreactor, biomass retention in bioreactors, temperature and pH control and most importantly, maintaining aerobic conditions. In addition, co-contaminants as BTEX compoimds or iron, Fe(lll), can jeopardize aerobic degradation of MTBE, both in and ex situ. 

In many situations, such as in deep groundwater, oxygen concentration may be severely limiting due to its consumption by surflcial aerobic organisms, or its low rate of transport into the system. Therefore, there has been great interest in the anaerobic degradation of BTEX. Although this has been... 

The vast amount of data from natural attenuation studies of petroleum hydrocarbon plumes generally supports anaerobic degradation, especially for benzene, toluene, ethylbenzene, xylenes (BTEX) under field conditions. The first-order degradation rates observed under unspecified anaerobic conditions (Suarez and Rifai, 1999) are typically one or two orders of magnitude lower than rates reported under aerobic conditions (Nielsen et al, 1996). 

The maximum growth rate (ttmax) reported for aerobic BTEX degrading and nitrifying organisms at 25 °C Hes in the range 3-9 d [86] and about... 

Alvarez, P.J. Vogel, T.M. (1995). Degradation of BTEX and their aerobic metabolites by indigenous microorganisms under nitrate reducing conditions. Water Science and Technology, Vol.31, pp. 15-28... 

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