Design Document for Passive Bioventing
Abstract
Bioventing is a process of aerating water-unsaturated soils to stimulate in situ biologic activity and promote the bioremediation of nonchlorinated hydrocarbons. Conventional bioventing systems use at least one electrically powered blower to inject air, thereby aerating the hydrocarbon contaminated subsurface. Passive bioventing utilizes the difference between atmospheric and subsurface gas pressures, which develop with changes in barometric pressure, to drive air through vent wells for aerating contaminated soils. This document provides the information necessary to identify sites where barometric pressure changes are anticipated to induce airflow in vent wells, design and install a pilot-test system for evaluating the feasibility of using passive bioventing, and design a full-scale passive bioventing system. Passive bioventing may be an alternative approach to conventional bioventing at Department of Defense (DoD) sites where electrical power is either unavailable or would be expensive to obtain such as training and proving grounds, and ranges. Even at facilities where electrical power is available, contaminated sites are often not conveniently located near power distribution points. At these locations, passive bioventing may be a cost-effective approach. At sites being treated with conventional bioventing systems where contaminant concentrations are no longer decreasing, switching to a passive bioventing approach might be appropriate since the rate of biotransformation is limited by the low hydrocarbon concentration rather than the rate of oxygen delivery. Specific subsurface lithologic and stratigraphic conditions must exist for any change in barometric pressure to induce significant airflow through vent wells. A thick (e.g., >100 ft) soil layer of high air permeability or a thin soil layer of low air permeability can retard the flow of air between the atmosphere and subsurface, leading to a gas pressure difference.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2006
- Accession Number
- ADA607230
Entities
People
- Sherrie Larson
Organizations
- Naval Facilities Engineering Systems Command