Sodium lactate is an inexpensive, soluble, food grade and fast acting substrate, which rapidly establishes reducing conditions to support the biodegradation of chlorinated solvents. Sodium lactate is readily bio-available and as such has a short lifetime follow injection. Sodium lactate is often combined with longer lasting substrates such as emulsified vegetable oil (EVO) to provide a jump start to the bacteria population while the EVO will provide carbon and hydrogen to support biodegradation of the chlorinated solvents over a longer period of time.
The anaerobic bioremediation process uses microorganisms to degrade chlorinated solvents such as tetrachloroethene (PCE) and trichloroethene (TCE). An organic substrate is added to the groundwater to generate reducing conditions and provide the necessary carbon and hydrogen to support biodegradation of the chlorinated solvents.
In anaerobic conditions, microorganisms will ultimately metabolize organic contaminants to methane, limited amounts of carbon dioxide, and trace amounts of hydrogen gas. In anaerobic reactions, bacteria gain energy and grow as an atom on a contaminant is replaced with hydrogen. Anaerobic metabolism encompasses many processes including fermentation, methanogenesis, reductive dechlorination, sulfate- and iron-reducing activities, and denitrification. Depending on the contaminant of concern, a subset of these activities may occur. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds, such as chlorinated hydrocarbons, may replace oxygen as the electron acceptor. Hydrogen used in the reaction typically is supplied indirectly through the fermentation of organic substrates.
In general, anaerobic conditions are used to degrade highly halogenated contaminants, though some petroleum hydrocarbons may also be biodegraded anaerobically. The halogenated compound, typically a chlorinated solvent such as tetrachloroethene (PCE), trichloroethene (TCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride (CT), chloroform (CF), and methylene chloride or their degradation products dichloroethene (DCE), vinyl chloride (VC), dichloroethane (DCA), and chloroethane serves as the electron acceptor while hydrogen serves as the direct electron donor. Chlorinated solvents can exist and migrate in multiple phases depending on how they were released and the site conditions present. These include a vapor phase in unsaturated soils, dissolved phase in groundwater, and non-aqueous phase liquids (NAPL) in the subsurface. Most chlorinated solvents are denser than water and hydrophobic.
During anaerobic biodegradation of chlorinated compounds, sequential removal of chloride ions is generally observed. Figure 1 demonstrates the dechlorination of PCE to TCE to cis-DCE or trans-DCE to VC to the final degradation product, ethene. In this reaction, hydrogen, the electron donor, is oxidized while the chlorinated ethene, the electron acceptor, is reduced. Hydrogen is generally the most important electron donor for anaerobic dechlorination.
The anaerobic reductive dechlorination of the more highly chlorinated (more oxidized) chlorinated hydrocarbons, such as PCE and TCE, occurs more readily than the dechlorination of chlorinated hydrocarbons that already are somewhat reduced (less oxidized), such as DCE and VC.
Hepure is a premier sodium lactate supplier. Our sodium lactate is distributed as a 60 percent solution in 605 pound drums (55 gallons) and 3025 pound totes (275 gallons).
PRINCIPLES AND PRACTICES OF ENHANCED ANAEROBIC BIOREMEDIATION OF CHLORINATED SOLVENTS,
Naval Facilities Engineering Service Center Port Hueneme, California, August 2004
Terra System, Terrasystems.net, 2018