Anaerobic means without oxygen. More specifically, it refers to occurring or living without oxygen present; therefore, the chemistry of the system, environment, or organism is characterized by reductive conditions. Many organic contaminants are degraded under anaerobic conditions by anaerobic bacteria called anaerobes. This process is known as anaerobic biodegradation. Anerobes use nitrate, sulfate, iron, manganese, and carbon dioxide as their electron acceptors. A related /term is anoxic.  

Anaerobic Biodegradation is the breakdown of organic contaminants by microorganisms when oxygen is not present. Some anaerobic bacteria use nitrate, sulfate, iron, manganese, and carbon dioxide as their electron acceptors, and break down organic chemicals into smaller compounds, often producing carbon dioxide and methane as the final products. This general mechanism of anaerobic biodegradation is an example of anaerobic respiration. Alternatively some anaerobic microorganisms can break down organic contaminants by fermentation. Fermentation is where the organic chemical acts as an electron acceptor. Anaerobic biodegradation is an important component of the natural attenuation of contaminants at many hazardous waste sites.  

Anoxic is an adjective that means without oxygen. For example, anoxic ground water is ground water that contains no dissolved oxygen. Anoxic ground-water conditions at hazardous waste sites are common because biodegradation processes often use up all the available oxygen. A related term is anaerobic.

Biodegradation is the breakdown of organic contaminants by microbial organisms into smaller compounds. The microbial organisms transform the contaminants through metabolic or enzymatic processes. Biodegradation processes vary greatly, but frequently the final product of the degradation is carbon dioxide or methane. Biodegradation is a key processes in the natural attenuation of contaminants at hazardous waste sites. A related term is biotransformation.

Electron Acceptor Microorganisms such as bacteria obtain energy to grow by transferring electrons from an electron donor to an electron acceptor. An electron acceptor is a compound that receives or accepts an electron during cellular respiration. The microorganism through its cellular machinery collects the energy for its use. The process starts with the transfer of an electron from an electron donor. During this process (electron transport chain) the electron acceptor is reduced and the electron donor is oxidized. Examples of acceptors include oxygen, nitrate, iron (III), manganese (IV), sulfate, carbon dioxide, or in some cases the chlorinated solvents such as tetrachloroethene (PCE), trichloroethene (TCE), dichloroethene (DCE), and vinyl chloride (VC). These reactions are of interest not only because they allow organisms to obtain energy, but also because they are involved in the natural

09.21.23