Anaerobic biodegradation of no. 2 diesel fuel in soil: a soil column study R. Boopathy * Department of Biological Sciences, Nicholls State University, P.O. Box 2021, Thibodaux, LA 70310, USA Received 29 July 2003; received in revised form 8 December 2003; accepted 8 December 2003 Available online 13 February 2004 Abstract Soil and sediments are contaminated with petroleum hydrocarbons in many parts of the world. Anaerobic degradation of petroleum hydrocarbon is very relevant in removing oil spills in the anaerobic zones of soil and sediments. This research investigates the possibility of degrading no. diesel fuel under anaerobic conditions. Anaerobic packed soil columns were used to simulate and study in situ bioremediation of soil contaminated with diesel fuel. Several anaerobic conditions were evaluated in soil columns, including sulfate reducing, nitrate reducing, methanogenic, and mixed electron acceptor conditions. The objectives were to deter- mine the extent of diesel fuel degradation in soil columns under various anaerobic conditions and identify the best conditions for efficient removal of diesel fuel. Diesel fuels were degraded significantly under all conditions compared to no electron supplemented soil column (natural attenuation). However, the rate of diesel degradation was the highest under mixed electron acceptor conditions followed in order by sulfate reducing, nitrate reducing, and methanogenic conditions. Under mixed electron acceptor condition 81% of diesel fuel was degraded within 310 days. While under sulfate reducing condition 54.5% degradation of diesel fuel was observed for the same period. This study showed evidence for diesel fuel metabolism in a mixed microbial population system similar to any contaminated field sites, where heterogeneous microbial population exists. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Anaerobic bioremediation; Soil column; Vadose zone; Mixed electron acceptor; Diesel fuel; Petroleum hydrocarbon; Biodegradation 1. Introduction One of the major environmental problems in US is the petroleum hydrocarbon spill from under ground storage tanks (UST). The leaks from the USTs cause ground water contamination which affect water supply to many communities in the US. A variety of in situ bioremediation strategies exists for the clean up of petroleum hydrocarbons. Most of the clean-up methods have been solely based on aerobic processes. The dom- inance of aerobic technologies is related to historical observations that the initial steps in biodegradation of hydrocarbons by microorganisms involves oxidation of the substrates by oxygenases (Rehm and Reiff, 1981) and by the recognition of oxygen as a limiting factor in many natural environments (Alexander, 1980; Baker and Herson, 1990). Studies of the microbial ecology of soil and subsur- face habitats have largely focused on aerobic micro- organisms (Ghirose and Balkwill, 1983). Many pure cultures of aerobic bacterial strains capable of degrading pollutants have been isolated from these habitats; there have been only few examples of pure cultures of anaerobic bacteria, which degrade the organic com- pounds of petroleum hydrocarbons. Rather, there is a great deal of specialization and interspecies interaction in anoxic/anaerobic habitats. Very few organisms de- grade a single compound completely. Degradation of organic compounds in these environments is often the result of community-interacting microbial popula- tions, generally termed as a Ôconsortium’ (Alexander, 1980). Anaerobic bioremediation of hydrocarbon-contami- nated soils and groundwater can be promoted under denitrifying conditions. Although aromatic hydrocar- bons readily degrade under aerobic conditions, the use of nitrate as an electron acceptor may offer advanta- ges over the use of oxygen (Bouwer and McCarty, 1984). * Tel.: +1-985-448-4716; fax: +1-985-493-2496. E-mail address: biol-rrb@nicholls.edu (R. Boopathy). 0960-8524/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2003.12.006 Bioresource Technology 94 (2004) 143–151