Simultaneous anaerobic transformation of tetrachloroethene and carbon tetrachloride in a continuous flow column

Abstract

Tetrachloroethene (PCE) and carbon tetrachloride (CT) were simultaneously transformed in a packed column that was bioaugmented with the Evanite culture (EV). The data presented here have been obtained over a period of 1930days. Initially the column was continuously fed synthetic groundwater with PCE (0.1mM), sulfate (SO4(2-)) (0.2mM) and formate (2.1mM) or lactate (1.1mM), but not CT. In these early stages of the study the effluent H2 concentrations ranged from 7 to 19nM, and PCE was transformed to ethene (ETH) (81 to 85%) and vinyl chloride (VC) (11 to 17%), and SO4(2-) was completely reduced when using either lactate or formate as electron donors. SO4(2-) reduction occurred concurrently with cis-DCE and VC dehalogenation. Formate was a more effective substrate for promoting dehalogenation based on electron donor utilization efficiency. Simultaneous PCE and CT tests found CT (0.015mM) was completely transformed with 20% observed as chloroform (CF) and trace amounts of chloromethane (CM) and dichloromethane (DCM), but no methane (CH4) or carbon disulfide (CS2). PCE transformation to ETH improved with CT addition in response to increases in H2 concentrations to 160nM that resulted from acetate formation being inhibited by either CT or CF. Lactate fermentation was negatively impacted after CT transformation tests, with propionate accumulating, and H2 concentrations being reduced to below 1nM. Under these conditions both SO4(2-) reduction and dehalogenation were negatively impacted, with sulfate reduction not occurring and PCE being transformed to cis-dichloroethene (c-DCE) (52%) and VC (41%). Upon switching to formate, H2 concentrations increased to 40nM, and complete SO4(2-) reduction was achieved, while PCE was transformed to ETH (98%) and VC (1%), with no acetate detected. Throughout the study PCE dehalogenation to ethene was positively correlated with the effluent H2 concentrations.

Response of chlorinated hydrocarbon transformation and microbial community structure in an aquifer to joint H2 and O2

“… 6 Carbon tetrachloride (CT) and especially CF have been observed to inhibit the reductive dehalogenation of perchloroethylene (PCE) and trichloroethylene (TCE). 7 Hence, a better understanding of mixed CHC transformation under laboratory conditions may provide a basis for groundwater remediation when multiple contaminants are present.…”

Biodegradation of carbon tetrachloride from groundwater in an upflow solid-phase biofilm system

“…9 CT has been anaerobic biotransformed under sulfate-reducing, methanogenic, nitrate-reducing, iron-reducing, fermenting, and mixed electron acceptor conditions. 10 M. F. Azizian 11 et al reported that the simultaneous anaerobic transformation of tetrachloroethene (PCE) and CT in a continuous ow column that was bioaugmented with the Evanite culture (EV). Additionally, CT biodegradation under denitrication conditions is of particular interest because of the simultaneous occurrence of both CT and nitrate in groundwater.…”

Structural dynamics and transcriptomic analysis of Dehalococcoides mccartyi within a TCE-Dechlorinating community in a completely mixed flow reactor

“…Structural and functional dynamics of dechlorinating communities have been investigated in continuous-flow biofilm and packed column systems (Carr et al 1998, Chung et al 2008, Maphosa et al 2010, Sabalowsky et al 2010, Azizian et al 2016, Mirza et al 2016, Mirza et al 2017, Delgado et al 2017. Continuous-flow suspended growth systems have also been used to study the impacts of solids retention times (SRTs) and other critical parameters on dechlorination activity of synthetic consortia and more complex communities (Gerritse et al 1997, Carr et al 2000, Drzyzga et al 2001, Zheng et al 2001, Sabalowsky et al 2010.…”