Remediation of LNAPL Contaminated Groundwater Using Plant-Assisted Biostimulation and Bioaugmentation Methods Brijesh K Yadav & Faiz A Ansari & Shreejita Basu & Anuj Mathur Received: 20 June 2013 /Accepted: 22 October 2013 /Published online: 29 November 2013 # Springer Science+Business Media Dordrecht 2013 Abstract Different cases of bioremediation technique were experimentally investigated here for decontaminating light non-aqueous phase liquid (LNAPL)-polluted ground- water collected from Panipat oil refinery situated in Haryana, India. Natural biodegradation of toluene, the selected LNAPL, was studied first under different vary- ing substrate concentrations at room temperature (21.6± 0.3 °C). Biostimulation was then studied by mixing the polluted groundwater with a primary treated domestic wastewater for providing nutrients and other supple- mentary components to the native microbial population. For studying the remaining cases, small-scale wetland having plants of Canna generalis was developed in the laboratory with and without the presence of toluene in the rhizosphere. The wetland system in the presence of toluene was used here for developing the pre-grown microbial cultures to enhance the degradation rate of the LNAPL (bioaugmentation). The plant-assisted bio- stimulation was studied in the third case by adding the polluted groundwater with the root zone water of the wetland system developed without the presence of toluene. In the fourth case, the biostimulation was coupled with the bioaugmentation strategy by mixing the groundwater with the root zone water of the wetland system developed in the presence of toluene. A comparative account of these four different bioremediation techniques was prepared for their respective rates of biodegradation, duration of lag phases, and the total time of degradation. It was observed that the plant-assisted bioremediation techniques had better perfor- mance over the natural biodegradation and biostimulation methods of the considered LNAPL. The plant-assisted biostimulation coupled with the bioaugmentation tech- nique needed almost no acclimatization time and acceler- ated the rate of degradation almost twofold compared to the natural bioremediation and, hence, is proved to be the best one among the other bioremediation techniques for decontaminating the LNAPL-polluted groundwater. The results of the conducted experiments can be used to obtain vital information on framing the engineered bioremedia- tion planning for LNAPL-contaminated sites. Keywords Biostimulation . Bioaugmentation . Canna generalis . LNAPL . Plant-assisted biodegradation 1 Introduction Petroleum fluids, popularly referred as non-aqueous phase liquids, are the basic building blocks of modern life and economy of a country. The oil refineries separate the different components of crude oil deriving different petroleum products primarily categorized based on their density as light and dense non-aqueous phase liquids (LNAPL and DNAPL, respectively) having various uses. Both NAPLs present a potential threat to the receiving soil–water system; however, the sites having complex Water Air Soil Pollut (2014) 225:1793 DOI 10.1007/s11270-013-1793-9 B. K. Yadav (*) Department of Hydrology, Indian Institute of Technology Roorkee, Roorkee 247667 Uttarakhand, India e-mail: brijeshy@gmail.com F. A. Ansari : S. Basu : A. Mathur Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India