In the simplest form, bioremediation is the breakdown of contaminants through biological means, typically some type of metabolism.  more...

In the simplest form, bioremediation is the breakdown of contaminants through biological means, typically some type of metabolism. The biological process of metabolism is based on a transfer of electrons from one substance to another resulting in a net gain in usable energy for the organism. This transfer of electrons requires a "donor" material that is commonly referred to as "food" and an "acceptor" material. In higher organisms, the last, or terminal electron acceptor is oxygen. In typical natural uncontaminated systems, food is limited which causes a competition among indigenous microbial populations for the available food, or electron donors. When an organic electron donor is released to the environment, the system becomes unbalanced and there the microbes compete for any available electron acceptors. Bringing the system back into balance is the basic concept behind enhanced bioremediation.

Most common organics like petroleum products readily act as electron donors and quickly degrade if an adequate supply of electron acceptors is present or introducted into the system. Other organics like chlorinated solvents are poor electron donors but degrade very quickly under anaerobic conditions as electron acceptors. The first step in a successful project is to determine your project goals. The second step is to determine if your contaminant will degrade faster aerobically or anaerobically. One good resource to determine degradation rates is the Handbook of Environmental Degradation Rates (Philip H. Howard et. al., 1991, CRC Press LLC). The third step is to determine the mass of contaminants and other interfering sinks such as other organics or competing electron acceptors.less...

In cases where the contaminant preferentially degrades faster aerobically, enhancing bioremediation can be easily accomplished by adding  more...

In cases where the contaminant preferentially degrades faster aerobically, enhancing bioremediation can be easily accomplished by adding an electron acceptor. There are a number of electron acceptors but oxygen is usually the most efficient. Other electron acceptors include nitrate, iron, and sulfate. Typically the form of electron acceptor is not critical as long as sufficient material can be added to meet the goals of the project. As an example, oxygen can be added mechanically through air sparging, soil vapor extraction, or tilling or chemically though the addition of dilute hydrogen peroxide or solid peroxygens. In all cases the ability to cost-effectively provide sufficient electron acceptor adequately distributed through the system is critical to successfully meeting the goals of the project.less...

Many chlorinated solvents degrade faster as electron acceptors. In these cases, an electron donor is added to the system to begin the process.  more...

Many chlorinated solvents degrade faster as electron acceptors. In these cases, an electron donor is added to the system to begin the process. As the substrate is metabolized under anaerobic conditions, an electron is released and is then used to replace a chlorine atom on the chlorinated solvent in a process known as reductive dechlorination or halorespiration. less...