Roaring Brook News

BIOREMEDIATION

ENGINEERING A

BETTER FUTURE

Engineered Bioremediation

The employment of bioremediation technology is at least 20 years old. The first bioremediation systems were used to mitigate petroleum spills, and bioremediation is still best used in cleaning up easily degraded petroleum products. What is new is the use of bioremediation on a commercial scale to treat compounds other than easily degraded petroleum products.

Engineered bioremediation is a more rapid contamination remedy than intrinsic bioremediation. Engineered bioremediation manipulates, and therefore accelerates, biodegradation reaction rates, thus requiring less time than intrinsic bioremediation. The shorter remediation time can reduce the costs required to maintain and monitor the site.

Oxygen is an important factor in bioremediation. Because most petroleum hydrocarbons require oxygen for degradation, the emphasis of engineered bioremediation systems has been in delivering oxygen to the contamination source. However, bioremediation of other contaminants, such as chlorinated solvents, will not necessarily be controlled by oxygen.

Bioremediation systems for soil above the water table (the vadose zone) may consist of soil vapor extraction. Bioremediation systems for soil and groundwater below the water table may consist of a set of air injection and recovery wells used to circulate oxygen and nutrients dissolved in water.

Bioremediation with other Technologies

In general, bioremediation is best employed after free phase contamination is removed. When soil is heavily contaminated, bioremediation is best implemented after excavating soils near the contaminant source. This sequencing reduces the demand on the bioremediation system and avoids the migration of the contaminant to the groundwater. Similarly, bioremediation is best employed after a groundwater pump-and-treat system is implemented for sites with floating product at the top of the groundwater table. Bioremediation may also be combined with a vapor recovery system to extract volatile contaminants from soils. It is possible to follow engineered bioremediation, which cleans up most of the contamination, with intrinsic bioremediation, which may be used for final polishing and contaminant containment. This approach is generally referred to as natural attenuation.

In the next issue of Roaring Brook News we will explore how to evaluate your bioremediation project and provide information regarding specific projects Roaring Brook Consultants is involved in.

Roaring Brook Consultants

Environmental Services Include:
•Phase I and II Site Assessments
• Soil and Groundwater Remediation
• Human Health Risk Assessment
• Environmental Field Services

ENGINEERING A BETTER FUTURE