Manufactured gas plants (MGP) produce different contaminants that when released into the environment cause significant soil and ground water pollution In situ enhanced bioremediation techniques are effective in remediation of MGPs particularly for contaminants such as the dense non-aqueous phase liquids (DNAPL), like coal tar The aim of this study was to assess the potential of in situ technologies in a laboratory column experiment. In situ amendments of nitrogen, phosphorus and oxygen releasing compound were performed on site Soil samples were collected from a site and leached daily to equate a 20 years cycle. The biosensor Escherichia coli HB101 were used to assess the toxicity of soil leachate while standard chemical analysis was performed The result of this study suggests that the presence of tar in the soil resulted in an increase in retention time of leachate and water chemistry over time Nutrients release in the soil leachate was very low which reflected slow in situ biodegradation of the contaminants

Key words Leachate, Tar, DNAPL, Contaminant, MGP, Retention time.