Use of simulated wetlands for the bioremediation of organic wood preservative

Soil and water from a freshwater wetland on the Mississippi Gulf Coast were used to set up laboratory-scale simulated wetlands. Six treatments, including the control, were run in triplicate to determine if certain amendments would enhance biodegradation of the two organic wood preservatives creosote and pentachlorophenol. The treatments were as follows: control, grass, grass + fertilizer, bacteria, fertilizer, and bacteria + fertilizer. During the 90-day study, soil samples were taken at day 0 and at 45-day intervals thereafter to monitor the concentrations of polycyclic aromatic hydrocarbons or PAHs (creosote constituents) and pentachlorophenol in the treatments. Microbial counts were also performed at day 0 and 45-day intervals. Reduction of two-, three-, four-, and five-ring PAHs and pentachlorophenol was observed for all treatments from day 0 to day 45. Only two treatments produced a significant reduction in PAHs after day 45. Between day 45 and 90, the grass treatment significantly lowered three-ring PAH levels, and the bacteria treatment significantly decreased the concentration of four-ring PAHs. The lack of reduction in other treatments between day 45 and day 90 could be due to the fact that additional nutritional and bacterial amendments were not added to any of the treatments after day 30 of the study. Except for the control, Microtox analysis revealed a significant reduction in toxicity for all treatments by day 90.