Kinetic Studies on Biostimulation Process for Decontamination of Petroleum
Hydrocarbons in Polluted Soil NourSh. El-Gendy1, and Joseph Y. Farah2
1. Egyptian Petroleum Research Institute, Nasr City, Cairo, Egypt
2. National Research Center, El-Dokki, Cairo, Egypt
Abstract:
A microcosm study was constructed with the purpose of investigating the effect of
complex co-substrate (corn steep liquor, CSL) addition on the indigenous bacterial
community and the resulting rate and extent of total petroleum hydrocarbon (TPH)
degradation in an oily soil with TPH content of 63)353mg/kg. TPH degradation was
characterized by a rapid phase of degradation that lasted for the first three weeks where 76%
removal of TPH occurred, followed by a slower degradation phase, where 83% of the initial
TPH was removed by the end of incubation period, 35 days, Branched alkanes are more
resistant to microbial degradation than n-alkanes. Furthermore, unresolved complex mixture
(UCM) hydrocarbon components are less degradable than n- and iso- alkanes and pristine (Pr)
was the most recalcitrant aliphatic compound studied in this work. These results together with
the expressive bacterial growth observed (from 107
to 1010
CFU/g soil) give strong support
that the addition of CSL resulted in increased degradation rates. The indigeneuos bacteria
grew exponentially during the incubation period of 35 days with a growth rate of 0.26 day’1
.
In order to investigate the biodegradation process for different petroleum hydrocarbons
contaminating the collected soil, kinetic modeling was performed to estimate the rates of
biodegradation of each hydrocarbon component in the studied system. Five different error
functions (sum of the square of the errors, hybrid fractional error function, Marquardt’s
percent standard deviation, average relative error and sum of the absolute errors) were
employed in this study to evaluate the goodness of fit of the model equation to the obtained
experimental data. This showed that the degradation of £nC2o-nC24, ZnC35-nCi2 and nCia can
be best represented by a second order model, whereas the TPH, TRP, nCn, UCM, £nCi0-
HCL4. EnCis-nCi9, ZnC25-nC29, ZnC3o-nC34, ZnCn, ^ d ZisoCn and isoprenoids Pr and Ph
were found to follow first order model.