Effect of Phytoremediation on Geotechnical Characteristics of Oil Contaminated Sands

ABSTRACT

The environmental contaminations occurred by exploration, drilling, extraction, transportation and storage of different substances for using in industries have serious effects on soils and their properties. This research examined the effects of phytoremediation on the removal of total petroleum hydrocarbons (TPHs) and geotechnical properties of a silty clayey sand contaminated by 3%, 5%, and 7% crude oil. Ophiopogon japonicus and Platycladus orientalis were two types of plants used to determine the phytoremediation effects within 30 and 60 days of operation. The scanning electron microscopy (SEM) images indicated that with increase in crude oil content at 0, 30, and 60 days of investigations, the soil particles become more flocculated. Comparison of the soil samples that experienced phytoremediation and without phytoremediation showed that flocculation of the soil particles became less during phytoremediation process. Use of Platycladus orientalis reduced soil flocculation more compared to Ophiopogon japonicus. The test results also showed that the TPHs removal rate using Platycladus orientalis was more than Ophiopogon japonicus. The addition of more crude oil contents caused enhancement of permeability while liquid limit, plastic limit, maximum dry density, optimum moisture content and CBR decreased. Investigation of the geotechnical properties of soil at different crude oil contents in 30 and 60 days of phytoremediation revealed that soil samples that experienced phytoremediation had more CBR and lower permeability compared to other ones without phytoremediation. It was also observed that upon more days of phytoremediation the liquid limit, plastic limit, optimum moisture content and permeability increased while the maximum dry density decreased. Using Platycladus orientalis compared to Ophiopogon japonicus yielded higher liquid limit, plastic limit, maximum dry density, and CBR along with lower optimum moisture content and permeability.

KEYWORDS:

• Phytoremediation
• silty clayey sand
• crude oil
• TPHs
• Atterberg limits
• CBR

Disclosure statement

On behalf of all authors, the corresponding author states that there is no conflict of interest.