Removal of hexadecane by hydroponic root mats in partnership with alkane-degrading bacteria: bacterial augmentation enhances system's performance

In this study, degradation of hexadecane was investigated in the contaminated water by employing plant-bacteria partnership in hydroponic root mat system. A halophyte grass, Leptochloa fusca, was planted in the presence of three hydrocarbons-degrading bacteria, namely Acinetobacter sp. ACRH82, Acinetobacter sp. BRRH61, and Bacillus niabensis ACSI85. The strains were screened based on their in vitro potential of hexadecane degradation as well as plant growth-promoting activities. Hydroponic systems containing vegetation or bacterial consortium separately attenuated a good proportion of hydrocarbons, chemical oxygen demand, biochemical oxygen demand, and total dissolved solids. Nevertheless, combined application of vegetation and bacteria significantly enhanced the system performance; i.e., hydrocarbons degradation was recorded up to 92%, chemical oxygen demand was reduced up to 95%, biochemical oxygen demand up to 84%, and total dissolved solids up to 47%. The inoculated bacteria displayed highest persistence in the roots followed by shoots and then in the wastewater. The biotoxicity assay revealed that hydroponic root mat containing plant-bacteria partnership was highly efficient in reducing the toxicity level. Conclusively, the present study implies that application of L. fusca in partnership with the hydrocarbon-degrading bacteria in hydroponic root mat is a suitable choice for the phytoremediation of hexadecane. Similar systems may be exploited for the enhanced degradation of other long-chain saturated alkanes from oil-contaminated wastewaters.