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An Integrated Multi-Process Phytoremediation System For Removal of Persistent Organic Contaminants from Soils

Bruce M. Greenberg, Xiao-Dong Huang, D. George Dixon and Bernard R. Glick Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1 Canada Abstract: Many techniques, both mechanical and biological, have been applied to the removal of persistent organic contaminants from soils. Bioremediation processes usually are slow, often because they have been employed independently. To improve the remediation process, application of multiple techniques that affect different aspects of contaminant removal can improve the rate and extent of remediation, especially for persistent organic pollutants. We have developed a multi-process phytoremediation system (MPPS) for removal of persistent organic pollutants from soils. The MPPS is composed of physical (volatilization), photochemical (photooxidation), microbial degradation and plant growth (phytoremediation) processes. The techniques applied to realize these processes are land farming (aeration and light exposure), microbial remediation (introduction of contaminant degrading bacteria) and phytoremediation (plant growth with plant growth promoting rhizobacteria [PGPR]). The results of several case studies have shown that this MPPS has greatly improved and accelerated the overall remediation process. Importantly, organic contaminants are degraded. Moreover, In a case study with creosote contaminants, the MPPS was able to remove 95% of PAHs (at 3 g/kg) from so il in an 8month period. In a 4-month trial with PAH containing soil from a 50-year-old weapons foundry, the MPPS removed 55% of the PAHs, as well as 50% of lowlevel metals. In a case study with oil sludge contaminants from a land farm soil, the MPPS was able to remove 90% of the TPHs (at 50 g/kg) in an 8 month period. Promisingly, in a field trial, the MPPS was able to perform with the same remediation kinetics and efficiency as observed in the laboratory and greenhouse trials. For instance, the MPPS was able to remove 60% TPHs (at 100 g/kg) in 3 month period. Thus, this system was very effective at removal of persistent and recalcitrant hydrocarbon contaminants from soil. Further, preliminary evidence suggests the MPPS can be used to remediate metals.