Anaerobic Bioremediation to Petroleum Source Areas: A Better Alternative than Conventional Cleanup Strategies
For years, conventional wisdom held that either in-situ chemical oxidation (ISCO) or aerobic bioremediation were the "best available technologies" for in-situ hydrocarbon remediation of petroleum impacted source areas. In reality, these popular remediation methods have been met with limited success, particularly in source areas characterized by high levels of sorbed-phase (non-aqueous) mass.
The reason why ISCO and aerobic bioremediation have not lived up to expectations is because microbial activity in petroleum impacted source-areas typically creates an anaerobic and reducing conditions, as oxygen and other high-energy electron acceptors (such as nitrate) are depleted. The low-solubility of oxygen and its highly reactive nature in the subsurface make it exceedingly difficult to supply the quantities of oxygen needed to drive successful aerobic bioremediation in anaerobic environments.
Many years of field applications have revealed that anaerobic bioremediation processes, such as denitrification-based bioremediation (DBB), are better suited to treat hydrocarbon source-areas characterized by pre-existing anaerobic conditions. The principal advantage of DBB is the efficient and cost-effective reduction of source-area hydrocarbon mass. DBB can also reduce and eliminate residual free-product via a combination of fungal and bacterial biodegradation processes. DBB is relatively non-intrusive and does not generate heat or volatile-gas emissions - important considerations at active facilities and near occupied structures where vapor-intrusion is of concern.
The long-term benefits of DBB also work well within the 'more realistic' administrative goals of Licensed Site Remediation Professionals (LSRPs) these days. Specifically, DBB can achieve downward trends in contaminant levels that are clearly the result of enhanced biological processes. Such results can support a Limited Restricted Use Response Action Outcome (RAO) and transition a property to a monitored natural attenuation program under a Classification Exception Area (CEA) and Remedial Action Permit for Ground Water.