In Situ Bioremediation

Abstract

In situ bioremediation technologies are sustainable because they neither require transport and deposition of contaminated soil, nor groundwater pumping, treatment, and discharge to recipients. Successful full-scale cases have benefited from the understanding of the prevailing environmental conditions and microbial communities present in both the unsaturated and saturated zones. In particular, the expanding knowledge on anaerobic degradation pathways and degrader communities have encouraged the use of monitored natural attenuation (MNA) that relies on the monitoring of indicators of aerobic or anaerobic degradation processes and naturally develops in the subsurface upon contamination. The treatment of the unsaturated zone can be performed by MNA, by enhancing the natural attenuation by addition of air in bioventing, or by the infiltration with nutrients. The saturated zone can be treated by MNA, by enhancing the aerobic degradation by air sparging, or by addition of oxygen releasing compounds. More recently, the enhancement of anaerobic processes responsible for the biodegradation of contaminants has been used by adding alternative electron acceptors or electron donors. The use of inocula has proven to be successful in full scale for the remediation of methyl tert-butyl ether (MTBE) and chlorinated solvents.