Effects of ferrous iron supplementation on reductive dechlorination of tetrachloroethene and on methanogenic microbial community

Abstract

Chloroethenes are common soil and groundwater pollutants. Their dechlorination is impacted by environmental factors, such as the presence of metal ions. We here investigated the effect of ferrous iron on bacterial reductive dechlorination of chloroethenes and on methanogen community. Reductive dechlorination of tetrachloroethene was assayed with a groundwater sample originally containing 6.3 × 103 copies mL–1 of Dehalococcoides 16S rRNA gene and 2 mg L–1 of iron. Supplementation with 28 mg L–1 of ferrous iron enhanced the reductive dechlorination of cis-dichloroethene (cis-DCE) and vinyl chloride in the presence of methanogens. The supplementation shortened the time required for complete dechlorination of 1 mg L–1 of tetrachloroethene to ethene and ethane from 84 to 49 d. Methanogens, such as Candidatus ‘Methanogranum’, Methanomethylovorans and Methanocorpusculum, were significantly more abundant in iron-supplemented cultures than in non-supplemented cultures (P<<0.01i>). Upon methanogen growth inhibition by 2-bromoethanesulfonate and in the absence of iron supplementation, cis-DCE was not dechlorinated. Further, iron supplementation induced 71.3% dechlorination of cis-DCE accompanied by an increase in Dehalococcoides 16S rRNA and dehalogenase vcrA gene copies but not dehalogenase tceA gene copies. These observations highlight the cooperative effect of iron and methanogens on the reductive dechlorination of chloroethenes by Dehalococcoides spp.

Dehalococcoides mccartyi strain NIT01 grows more stably in vessels made of pure titanium rather than the stainless alloy SUS304

“…Thus, the inhibition of TCE dechlorination by steel pieces was concluded to be caused by eluted Fe 2+ . This agreed well with a previous study that revealed that 0.54 mM Fe 2+ did not inhibit PCE dechlorination by a consortium containing Dehalococcoides (Yoshikawa et al, 2021), whereas 1.75 mM Fe 2+ inhibited TCE dechlorination by KB‐1 culture (Paul & Smolders, 2014). It is also believed that Ni 2+ does not inhibit dechlorination because D. mccartyi strain NIT01 has less sensitivity towards Ni 2+ .…”

Sequential Anaerobic/Aerobic Microbial Transformation of Chlorinated Ethenes: Use of Sustainable Approaches for Aquifer Decontamination

“…Aquifer depth seems not to affect the presence of dechlorination functional biomarkers. In aquifers at 14 m and 1.5-2 m below ground level, OHR biomarkers were in the range of 10 2 -10 4 gene copies L −1 in both conditions [147,148].…”

“…RDase genes were used as functional biomarkers for monitoring OHR activity. In a lower chlorinated ethenes-contaminated aquifer, tceA, vcrA, and bvcA were quantified in four wells [147]. Quantification showed a higher level of variability.…”

“…vcrA and bvcA concentrations were between 10 2 and 10 4 copies mL −1 and 10 2 and 10 3 copies mL −1 , respectively. The well with a lower concentration of tceA (10 1 ) showed a lower concentration of ethene [147].…”

Methodology to Increase the Efficiency of the Mineral Water Extraction Process

“…As a result, geological surveys can be very expensive and are required throughout the geological development process. A technical scheme for geological development is necessary and justifies a rational development method [31][32][33]. In countries such as the USA, Japan, Italy, and Germany, achievements have been recorded regarding the use of hydromineral raw materials and the extraction of rare elements and mineral salts [34,35].…”