Sorption and biological removal of creosote-contaminants from groundwater in soil/sand vegetated with orchard grass (Dactylis glomerata)

A combination of phytoremediation and filter technology (e.g. permeable barriers) was used in laboratory experiments for treatment of creosote-contaminated groundwater. Creosote consists of polycyclic aromatic hydrocarbons (PAHs), nitrogen/sulfur/oxygen (NSO)-heterocyclic compounds and phenols. Creosote-contaminated water was added to nine containers containing a 20/80-soil/sand mix (percent by volume). To differentiate between sorption to filter material, microbial degradation, and effects caused by the presence of orchard grass (Dactylis glomerata), three containers were kept sterile, three were non-sterile, and three were vegetated with orchard grass. The combination of sorption and microbial processes led to an efficient disappearance of all analyzed compounds from the water, where sorption processes were important for removal of PAHs and NSO-compounds, and biological processes were dominant for removal of phenols. Vegetated filter material was the most efficient in treating the contaminated water, and in particular the largest effect of plants was observed during periods where water residence time was short. The effect of vegetation was most apparent on dimethylphenols and trimethylphenols, but the vegetation also affected removal of phenol, methylphenols, and 2-ring NSO-compounds. The conclusion of the experiment is that a soil/sand filter material can efficiently treat creosote-contaminated groundwater, whereas the presence of orchard grass further improves treatment. (C) 2002 Elsevier Science Ltd. All rights reserved.