Monitoring the biodegradation of TPH and PAHs in refinery solid waste by biostimulation and bioaugmentation

The effect of natural attenuation, biostimulation and bioaugmentation-biostimulation on the removal of petroleum pollutants, specifically Total Petroleum Hydrocarbons (TPH), as well as Polycyclic Aromatic Hydrocarbons (PAHs) in a refinery solid waste was estimated. The experimental procedure took place on a laboratory scale in three separate tanks (natural attenuation, biostimulation and biostimulation-bioaugmentation tank) for a period of 80 days. Optimal conditions of temperature, humidity and ventilation were applied in order to ensure an efficient performance of the microdigesters. According to the results, addition of indigenous microorganisms and nutrients in biostimulation-bioaugmentation tank, proved to be particularly effective on the biodegradation of petroleum pollutants, achieving a removal efficiency of 52 and 87% for TPH and PAHs, respectively. In the biostimulation tank, the efficiency of TPH and PAHs removal was 47 and 59%, accordingly. Less effective appeared to be the natural attenuation process with a reduction efficiency of 37% for TPH and 42% for PAHs.