PLANT-ENHANCED SUBSURFACE BIOREMEDIATION OF NONVOLATILE HYDROCARBONS

In recent years, phytoremediation, i.e., the use of plants to clean up soils contaminated with organics, has become a promising new area of research, particularly for in-situ cleanup of large volumes of slightl y contaminated soils. A model that can be used as a predictive tool in phytoremediation operations was developed to simulate the transport a nd fate of a residual hydrocarbon contaminant interacting with plant r oots in a partially saturated soil, Time-specific distribution of root quantity through soil, as well as root uptake of soil water and hydro carbon, was incorporated into the model. In addition, the microbial ac tivity in the soil rhizosphere was modeled with a biofilm theory, A sa ndy loam, which is dominant in soils of agricultural importance, was s elected for simulations, Cotton, which has well-documented plant prope rties, was used as the model plant. Model parameters involving root gr owth and root distribution were obtained from the actual held data rep orted in the literature and ranges of reported literature values were used to obtain a realistic simulation of a phytoremediation operation. Following the verification of the root growth model with published ex perimental data, it has been demonstrated that plant characteristics s uch as the root radius are more dominant than contaminant properties i n the overall rate of phytoremediation operation. The simulation resul ts showed enhanced biodegradation of a hydrocarbon contaminant mostly because of increased biofilm metabolism of organic contaminants in a g rowing root system of cotton. Simulations also show that a high mean d aily root-water uptake rate increases the contaminant retardation fact ors because of the resulting low water content. The ability to simulat e the fate of a hydrocarbon contaminant is essential in designing tech nically efficient and cost-effective, plant-aided remedial strategies and in evaluating the effectiveness of a proposed phytoremediation sch eme, The model presented can provide an insight into the selection and optimization of a specific strategy.