Due to intensified usage of diesel-biodiesel blending oils, solving potential contamination problems becomes crucially important. The objective is to investigate various percentages of diesel-biodiesel mixtures caused contamination and remediation approaches, including bioaugmentation with seven proved diesel-degrading bacterial species. Degradation of 80%-99% was achieved with the proposed remediation approach. The TPHd degradation efficiency (%) and rates (k) in the control batch (CT) found either similar or superior to the bioaugmentation batch (BA). The batches with 20% and 50% biodiesel achieved 10% improvement of TPHd degradation in CT over BA. The TPHd degradation was enhanced by the increase of biodiesel. For example, degradations of 99% were achieved in the soil polluted with 100% biodiesel. The increase of the biodiesel enlarged the total heterotrophic bacterial counts from 10(7) to 10(9) CFU/g dry soil. The molecular data concluded Gordonia alkanovorans and Gordonia desulfuricans were most dominant in the indigenous community. Pseudomonas aeruginosa was a strong survivor last for the entire remediation. The growth patterns of bacteria indicated the introduced species were useful only in the beginning. Using the recommended molecular tools to identify the useful bacteria prior to a remediation project would be helpful in reducing the cost and determine a wise remediation strategy. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.