Bioremediation of 6 % [w/w] diesel-contaminated mainland soil in Singapore: Comparison of different biostimulation and bioaugmentation treatments

The efficacy of indigenous microorganisms to degrade diesel oil in contaminated mainland sites in Singapore was investigated. A semi-scale trial was made by spiking topsoil with 6 % [w/w] of diesel oil. The results indicated that in the presence of NPK commercial (Rosasol (R)) fertilizer a 53 % reduction in contaminant concentration was recorded after 60 days compared to untreated controls while the addition of a mixture of urea and K2HPO4 effected a 48 % reduction in the Total Recoverable Petroleum Hydrocarbons. A commercial culture and an enriched/isolated microbial association proved to be the least effective with 25 and 9 % reductions, respectively. The results confirmed the bioremediation potential of indigenous microorganisms for diesel-oil contaminated mainland soil. Identification of the persistent Compounds was done and perceived as a toot in decision-making on strategies for speeding up of the degradation process to achieve clean-up standards in shorter remediation periods.