Increasing electron donor concentration does not accelerate complete microbial reductive dechlorination in contaminated sediment with native organic carbon

• Published in: Biodegradation (Dordrecht) Vol. 32; no. 5; pp. 577 - 593
• Main Authors: Haluska, Alexander Arthur, Finneran, Kevin T.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-10-2021; Springer; Springer Nature B.V
• Subjects: Acetates; Acetic acid; Aquatic Pollution; Attenuation; Biomedical and Life Sciences; Contaminated sediments; Contamination; Dechlorination; Electrons; Ethene; Ethylene; Geochemistry; Iron; Lactate; Lactic acid; Life Sciences; Lipids; Methanogenesis; Microbial contamination; Microbiology; Microorganisms; Molecular weight; Natural attenuation; Olefins; Organic carbon; Original Paper; Sediment; Sediment pollution; Sediments (Geology); Sodium; Sodium lactate; Soil Science & Conservation; Solvents; Soybean; Soybean oil; Soybeans; Stoichiometry; Substrates; Terrestrial Pollution; Trichloroethene; Trichloroethylene; Vinyl chloride; Waste Management/Waste Technology; Waste Water Technology; Water Management; Water Pollution Control; Trichloroethylene; Emulsified vegetable oils; Vinyl chloride; Microbial reductive dechlorination
• DOI: 10.1007/s10532-021-09953-y
• EISSN: 1572-9729
• ISSN: 0923-9820

Experiments with Fe(III)-rich, chloroethene-contaminated sediment demonstrated that trichloroethylene (TCE) and vinyl chloride (VC) were completely reduced to ethene regardless of whether electron donor(s) were added at 1 × stoichiometry or 10 × stoichiometry relative to all-electron acceptors. Unamended controls uniformly reduced TCE to ethene with a mean
time to complete dechlorination
(operationally defined as the presence of stoichiometric ethene production) of 79 days. Adding 1 × and 10 × acetate hindered the rate and extent of TCE and VC reduction relative to unamended controls, with several only partially reduced when the experiments were terminated. Adding high molecular mass (soybean oil derivative) substrates did not increase microbial reductive dechlorination relative to unamended incubations, and in many cases, hindered microbial dechlorination in favor of methanogenesis. The mean
time to complete dechlorination
was comparable between low (× 1) and high (× 10) electron donor concentration for all lipid-based electron donors tested. Those tested included Newman Zone® Standard without sodium lactate (96 vs. 75 days, respectively), CAP 18 ME (85 vs. 94 days, respectively), EOS 598B42 (68 vs. 72 days, respectively), and acetate (134 vs. 125 days, respectively). These data suggest that the addition of an electron donor does not always increase the rate and extent of reductive dechlorination but will increase costs. In particular, increasing the concentration of electron donors higher than the stoichiometric demand only decreased complete microbial reductive dechlorination, which is the opposite of most standard “more time and more electrons” approaches. These data argue that site-specific electron donor demands must be evaluated, and in some cases, a monitored natural attenuation (MNA) approach is most favorable.