Reintroduction of Contaminant in Groundwater Alters Bacterial Community

摘要

Bioaugmentation, a form of bioremediation, involves addition of microbial populationacclimated with the contaminant of concern to degrade contaminants in situ. Duringbioremediation, periodic absence of the contaminant can alter the microbial community resultingin less efficient degradation. This study investigates the effects of supplying an alternate carbonsource during the contaminant absence periods and/or bacterial degrader after the absenceperiods on the diversity of the bacterial community and the contaminant removal efficiencywhen the contaminant is reintroduced. Benzene being a common groundwater contaminant wasused as the model contaminant in this study. Sand columns were set up to simulate groundwaterflow and benzene breakthrough experiments were conducted to investigate benzene removalefficiencies (BREs) and bacterial community changes. Two benzene absence periods (BAP) of10 or 25 days were tested during which only deionized water with no organic carbon source orethanol was supplied. The effect of the absence period on the removal efficiency was moreprominent during the longer absence period. Columns that received bacteria immediately afterthe absence periods showed superior performances than those that did not. A strain with 100%identity to Pseudomonas putida disappeared during the BAP but reemerged following thereintroduction of benzene. Columns provided with an alternative carbon source (ethanol) duringthe BAP and/or bacterial culture helped in maintaining the bacterial community and improvingthe BRE. This work identified changes in the bacterial community and their responses due tocontaminant absence periods.