GLOSSARY - Bioaugmentation for Groundwater Remediation - page 362

Anaerobic ‐ “Without air.” Generally refers to occurring or living without oxygen present.
Thus, in an anaerobic groundwater system, the chemistry is characterized by reductive
conditions. Sometimes anaerobic is used (e.g., in wastewater treatment) to indicate a lack of
any electron acceptors (including nitrate and sulfate). In groundwater, a dissolved oxygen
concentration below 1.0 mg per liter (mg/L) is generally considered anaerobic.

Anneal ‐ The pairing of complementary DNA or ribonucleic acid (RNA) sequences via
hydrogen bonding to form a double-stranded polynucleotide.

Anoxic ‐ “Without oxygen.” For example, anoxic groundwater is groundwater that contains
no dissolved oxygen.

Aquifer ‐ An underground geological formation that stores groundwater. A confined aquifer
lies beneath a confining unit of lower hydraulic conductivity. An unconfined aquifer does not
have a confining unit and is defined by the water table.

Aquitard ‐ An underground geological formation of low permeability that does not readily
transmit groundwater.

Attenuation ‐ Reduction of contaminant concentrations over space or time. Includes both
destructive (e.g., biodegradation, hydrolysis) and non-destructive (e.g., volatilization, sorption)
removal processes.

Bacteriophage ‐ Any one of a number of viruses that infect bacteria, often shortened to
simply “phage.” Bacteriophages are extremely abundant and widespread. In nature, phages
often transfer DNA among bacteria and have been used as designed carriers of DNA to spread
desirable genes into bacteria.

Bedrock ‐ The solid or fractured rock underlying surface solids and other unconsolidated
material or overburden.

Bioaugmentation ‐ Addition of microbes to the subsurface to improve the biodegradation of
target contaminants. Microbes may be “seeded” from populations already present at a site or
from specially cultivated strains of bacteria.

Bioavailability ‐ The degree or ability to be absorbed and ready to interact in an organism.

Biobarrier ‐ A remediation technology designed to intercept and biologically treat a
contaminant plume as it passes through a permeable subsurface barrier. Biobarriers are
created by installing wells or trenches across the width of a plume to deliver substrate to the
microorganisms in the aquifer as groundwater flows through the barrier.

Biodegradation ‐ Biologically mediated conversion of one compound to another.

Biofouling ‐ Impairment of the functioning of wells or other equipment as a result of the
growth or activity of microorganisms.

Biomarker ‐ A biochemical within an organism that has a particular molecular feature that
makes it useful for identifying a specific biological activity.