Phytoremediation of Solid Oil Shale Waste from the Chemical Industry

The processed oil shale (semi‐coke) contains several organic and inorganic compounds (oil fractions, sulphides, phenolic compounds, polycyclic aromatic hydrocarbons) and is highly toxic. The solid waste deposit is a source of toxic phenolic leachate, which is discharged into nearby bodies of water without any treatment. Field experiments were carried out in order to test the effect of phytoremediation to enhance in‐situ microbial biodegradation of pollutants in semi‐coke. Four pilot test plots (50 m2) were established at a semi‐coke deposit in July 2001. The growth rate of plants was approximately twice higher in the case of soil amendment. The phytoremediation increased the number of biodegradative bacteria and diversity of microbial community in semi‐coke. The presence and diversity of multi‐component phenol hydroxylase (mPH) genes in the environment were assessed using the microbial DNA directly extracted from semi‐coke. The changes in the genotypes of mPHs indicated shifts in the microbial community structure towards the more efficient degradation of pollutants due to plant treatment. Within a four‐month period starting from the establishment of test plots in July, the concentration of phenolic compounds decreased three times in average and the concentration of oil products up to ten times, compared to the control plot.