Removal of Toxic Organics in Wetlands: A Mechanistic Model

• Main Author: Florez, Luz Edith
• Other Authors: John H. Pardue
• Format: Others
• Language: en
• Published: LSU 2004
• Subjects: Civil & Environmental Engineering
• Online Access: http://etd.lsu.edu/docs/available/etd-04072004-165638/

The ability of removing toxic organic compounds in natural systems is important due to the capacity of these toxicants to increase risk of diseases when they are ingested by humans. This study developed a mechanistic model to estimate the removal efficiency of toxic organics in wetlands using the tanks-in-series model. Sensitivity analyses were performed for different values of the hydraulic loading rate and two kinds of wetlands: bottomland hardwood forest and freshwater marsh. It was observed the effect in the removal efficiency by the number of cell in series was principally perceived for values of N between 1 and 4; that for both kind of wetlands. The most hydraulic loading rate, the less removal of organic compounds was observed in both kinds of wetlands and for the different values of N. For the same value of hydraulic loading rate, number of sections considered (N) and the same kind of wetland, soluble organics (low K_ow) as naphthalene were more assimilated than hydrophobic organics (high K_ow) as hexachlorobenzene. Two zones were well defined on the logarithmic space defined by Sorption versus Henry's Constant for two conditions total recycle and no recycle: Air zone and sediment zone. Removal efficiency went down when the value of DOC in the water column went up for insoluble organics as hexachlorobenzene. For soluble organics as naphthalene no effect was observed. That was observed in both kinds of wetlands. Removal efficiency has no a large dependence of the value of DOC in the sediment bed, in both kinds of wetlands and for both kind of compounds (lower and higher K_ow value). The higher K_w of the pollutant, the higher removal in both of the kind of wetlands was observed in this analysis. It was observed that removal efficiency is higher when the sediment bed depth is higher until determined values depending of the kind of pollutant. It was observed that removal efficiency is higher for soluble organics as naphthalene than for hydrophobic organics as hexachlorobenzene, and in addition higher removal efficiency is observed in bottomland hardwood forest wetlands than in freshwater marshes.