Use of simulated constructed wetlands for organic wood preservatives bioremediation

Soil and water from a freshwater wetland on the Mississippi Gulf Coast were set up in laboratory-scale simulated wetlands. Six treatments, including a control, were ran in triplicate to determine if certain amendments would enhance biodegradation of two organic wood preservatives, creosote and pentachlorophenol (PCP). 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 selected polycyclic aromatic hydrocarbons (PAHs) (creosote constituents) and PCP in the treatments. Microbial counts were also performed at day 0 and at 45-day intervals. Reduction of total selected PAHs and PCP was observed for all treatments from day 0 to day 45. Only two treatments produced a significant reduction in PAHs after day 45. All treatments had significantly lower PAHs than the control by day 90. Treatments containing fertilizer, bacteria, or both showed significant reduction of PCP by day 90. 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.