Fabrication of Novel In-Situ Remediation Tools for Unconventional Oil Contamination

Abstract

The aftermath of unconventional oil (UO) accidents highlights the lack of preparedness of governments to deal with UO emergencies. Because bioremediation is considered slow process, physicochemical treatment processes are necessary in removing contaminants to constrain the spread of oil. In preliminary phase of study, bed systems for adsorption of oil compounds packed with modified dolomite were applied as pre-treatment for bioremediation systems. The high affinity of oil molecules to the active sites due to hydrophobic nature of dolomite surface, as well as low solubility of oil in water, resulted in rapid process of oil adsorption on external surface of modified dolomite. UO contaminated site contain high concentration of polyaromatic hydrocarbons (PAHs). Thus, the final phase of study focused on finding enzyme mixture for biodegradation of PAHs contaminated sites for water and soil treatment. In this regard, screening of indigenous bacteria, identification of involved enzymes, and biodegradation tests were carried out. Several combinations of the pre-selected strains were used to create most prompting consortium for enzyme production. To mimic in situ application of enzyme mixture, bioremediation of pyrene contaminated soil was carried out in soil column tests. The average values of pyrene removal after 6 weeks indicated that the enzyme cocktail can be an appropriate concentration for soil enzymatic bioremediation in the soil column system. A bioinspired device was fabricated as a sustainable remedial method. Our results showed that after 200 seconds of circulating the enzyme solution 100% of anthracene in 1.5 L of 4.6 mg/L was removed from the beaker side. In addition to the circulation of PAH degrading enzymes in hollow fiber lumens, aliphatic degrading enzymes confined in multilayer nanofibrous membrane systems play an important role in the removal of oily compounds. Based on our studies, modified polyimide aerogels were suitable to support enzyme immobilization. The degradation tests clearly showed that immobilized enzymes had biodegradation ability for model substrate in contaminated water. Our results confirmed that immobilization of cocktail enzyme mixture enhanced their storage stability, more than 45% of its residual activity at 15 ± 1 ºC for 16 days. This study could set the guideline for the enzymatic bioremediation of aromatic pollutants especially polycyclic aromatic hydrocarbons in highly contaminated soil and water body