Remediation of Artificially Hydrocarbon Polluted Vadose Zone Soil in Glass Column through Percolation with Solution of Nutrient, Nutrient-Surfactant or Surfactant

Remediation of hydrocarbon polluted vadose zone (HPVZ) through percolation with solution of nutrient, nutrient-surfactant, or surfactant in glass columns was investigated in this study using standard methods. Percolated liquids from the columns and soils retrieved at the end of the experiment were analyzed for nitrate, phosphate, sulphate, total-petroleum hydrocarbon, and selected microbial groups. Results obtained showed that there were nitrate, phosphate, and sulphate in the percolated liquids. Cumulative hydrocarbon in the percolated liquids was 5.35 – 7.59 % of cumulative hydrocarbon start-up concentration in the columns. Cumulative hydrocarbon attenuation across soil layers in column flooded with solution of nutrients (column NT), nutrient-surfactant (column NTS), and surfactant (column SF) were 89.29, 95.27, and 66.92 % respectively. There was more phosphate reduction in column NTS, and more sulphate reduction in column NT. Hydrocarbon-utilizing fungi in columns NT and NTS increased from 3.5 Log₁₀ CFU.g^-1 to between 4.0 – 5.0 Log₁₀ CFU.g^-1, whereas a decrease was observed for column SF. Hydrocarbon-utilizing bacteria in all the columns increased from between 1.0 – 2.5 Log₁₀ CFU.g^-1 to between 2.0 - 3.5 Log₁₀ CFU.g^-1. Emergence of hydrocarbon utilization among anaerobic bacteria population was also observed in all the columns. It is concludedthat percolation with nutrient-surfactant solution will be more effective in remediation of HPVZ, and that consequential migration of nutrients alongside hydrocarbons into groundwater can aid in enhancing biodegradation of the infiltrated hydrocarbons.

Keywords
Biodegradation; petroleum hydrocarbons; vadose zone; inorganic nutrients; surfactant.