Biostimulation of <i>n</i>-Alkane Degradation in Diesel Fuel-Spiked Soils

<p>Nutrient enhancement of bioremediation with nitrogen, namely biostimulation, increases process performance. Selection of a proper nitrogen source is critical for bioremediation applications. In this study, the effects of different nitrogen sources on biodegradation of C<sub>10</sub>–C<sub>25</sub> <i>n</i>-alkane compounds in diesel fuel-spiked soil were revealed, and the most appropriate nitrogen source for biodegradation of semi- and non-volatile <i>n</i>-alkanes was investigated. Bioremediation of diesel fuel contaminated soil was monitored in lab-scale reactors for 15 days. Ammonium sulfate, potassium nitrate and urea were used as nitrogen sources. Carbon dioxide and oxygen levels in the reactors were recorded to monitor microbiological activity. Contaminant removal process was investigated by pH, heterotrophic plate count, total petroleum hydrocarbons (TPH) and C<sub>10</sub>–C<sub>25</sub> <i>n</i>-alkane analyses. First-order kinetic constants were calculated via respirometric and contaminant concentration data. According to total C<sub>10</sub>–C<sub>25</sub> <i>n</i>-alkane removal levels and degradation rate constants, ammonium sulfate addition resulted in the most efficient contaminant removal followed by potassium nitrate and urea. Simultaneous degradation of individual <i>n</i>-alkanes was observed for all of the nitrogen sources. Urea addition changed the distribution of individual <i>n</i>-alkane concentrations relative to the pre-experimental concentrations. Nitrogen source type had no differential effect on degradation rates of semi- (C<sub>10</sub>–C<sub>16</sub>) and non-volatile (C<sub>17</sub>–C<sub>25</sub>) fractions.</p>