Among the environmental management services provided by ACT is the remediation of soil and groundwater impacted by various types of contaminants. Among the most recalcitrant compounds requiring remedial technologies are volatile organic compounds (VOCs). And among this group is a number of regulated contaminants such as solvents and degreasers commonly used for everything from dry cleaning to printed circuit board degreasing.
The remediation of VOCs commonly involves the introduction of various amendments capable of producing mineral, chemical or biological reactions that kick off the chemical process of dechlorination. There are two types of reactions that lead to dechlorination: chemical oxidation and chemical/biological reduction. Oxidation results in the loss of electrons, while reduction results in the gain of electrons.
Oxidation is one half of a reduction/oxidation (redox) pathway, where electrons are mobilized by the reaction. The electron donor causes an electron to move from the oxidant to the contaminant. One of the reactants in the reaction becomes oxidized, or loses electrons, while the other reactant becomes reduced, or gains electrons. In chemical oxidation, chemicals such as sodium and potassium permanganate, peroxides and persulfates are strong oxidizers that give electrons away to other compounds in a reaction and are used to reduce contaminant concentration or oxidize the contaminant into harmless compounds. The electrons attach to chlorine rings, breaking the bonds and beginning a process that breaks down the chemical to either ethene or ethane, depending on the parent contaminant.
Chemical reduction is the other half of the redox pathway. Iron powder is commonly used here. The iron begins to oxidize when it comes in contact with groundwater, then the electron is released and migrates to the chlorine rings, starting the dechlorination process.
A third type of remedial amendment utilizes biological agents to produce a chemical reduction pathway. The goal is to introduce a food source to populations of microbes which are relatively ubiquitous in the subsurface. The microbes degrade the food source, which causes the release of electrons. Additionally, if sampling reveals an insufficient microbial population, a microbial culture may be introduced along with the food source.
Please contact us when you find yourself in need of these types of remediation services.
– John Poulson, Senior Account Manager