The effect of triethyl phosphate on the biodegradation of diesel fuel

Abstract

Bioremediation is a repudiation technique that is gaining popularity because of its low cost and the ability to perform in situ treatments in contaminated surface and subsurface environments. The effectiveness of bioremediation in subsurface environments is dependent on soil texture, soil organic matter content, pH, moisture content, temperature, oxygen and nutrient availability, and the concentration of the compound to be repudiated (Atlas, 1981). Recent studies conducted at the Savannah River Site in Aiken, South Carolina have injected a gaseous phase nitrogen and phosphorous nutrient mixture into an aquifer contaminated with trichloroethylene (TCE). The results indicate that the injected nitrous oxide and triethyl phosphate (TEP) stimulate the growth of methanotrophic bacteria and also increase the amount of TCE degradation (Brockman et a1., 1995., Palumbo et a1., 1995., Pfiffner et a1., 1997). However, no extensive research has been done on the effects of triethyl phosphate on the biodegradation of diesel fuel. Three types of treatments (sterile soil with diesel and TEP, a pictorially active soil with diesel, and a pictorially active soil with diesel and TEP) were set up in microcosms and housed in a controlled temperature chamber for 48 days. The samples were destructively sampled in triplicate on Days 0, 3, 6, 12, 24, and 48. Microbial populations were quantified by total heterotrophic plate counts. Total petroleum hydrocarbons were quantified by GC/FID. The data showed that, during Days 3 through 24, the TEP treated sediment that contained bacteria initially degraded more diesel than the diesel-only sediment. The TEP amended sediments stimulated more growth in the bacterial populations. However, after 48 days, the percent degradation and the number of microbes in the diesel-only sediment and the diesel and TEP treated sediments were similar. The control samples indicate that in the absence of microbes, TEP is lost abiotically.