Complete biological reductive transformation of tetrachloroethene to ethane

Abstract

Reductive dechlorination of tetrachloroethene (perchloroethylene; PCE) was observed at 20°C in a fixed-bed column, filled with a mixture (3:1) of anaerobic sediment from the Rhine river and anaerobic granular sludge. In the presence of lactate (1 mM) as an electron donor, 9 ,uM PCE was dechlorinated to ethene. Ethene was further reduced to ethane. Mass balances demonstrated an almost complete conversion (95 to 98%), with no chlorinated compounds remaining (<0.5 ,ug/liter). When the temperature was lowered to 10°C, an adaptation of 2 weeks was necessary to obtain the same performance as at 20°C. Dechlorination by column material to ethene, followed by a slow ethane production, could also be achieved in batch cultures. Ethane was not formed in the presence of bromoethanesulfonic acid, an inhibitor of methanogenesis. The high dechlorination rate (3.7 ,mol l-l h-'), even at low temperatures and considerable PCE concentrations, together with the absence of chlorinated end products, makes reductive dechlorination an attractive method for removal of PCE in bioremediation processes.

Anaerobic reduction of ethene to ethane in an enrichment culture

“…Evidence for the microbial reduction of ethene to ethane was found in an anaerobic £ow-through soil column in which tetrachloroethene was reductively dechlorinated to ethene [13]. This paper describes ethene reduction by a methanogenic enrichment, originating from that soil column.…”

“…The methanogenic consortium was enriched from an anaerobic ¢xed-bed column, in which PCE was completely dechlorinated to ethene and ethane [13]. The column had been ¢lled with a mixture of Rhine river sediment and ground granular sludge from an up£ow anaerobic sludge blanket reactor.…”

“…Komatsu et al [12] found traces of ethane in anaerobic enrichment cultures originating from anaerobic sewage sludge, which were capable of dechlorinating cis-1,2-dichloroethene (cis-DCE) to ethene. In a ¢xed-bed column study, we have found that tetrachloroethene (PCE) is reductively dechlorinated to ethene under anaerobic conditions and that ethene was completely further reduced to ethane [13].…”

Geochemistry and microbial diversity of a trichloroethene-contaminated Superfund site undergoing intrinsic in situ reductive dechlorination

“…In situ reductive dechlorination is considered to be the most promising mechanism for bioremediation of chloroethene spill sites [5]. When trichloroethene (TCE) represents the primary contaminant, sequential reductive dechlorination may yield cis-1,2-dichloroethene (cis-DCE), minor quantities of trans-1,2-dichloroethene, vinyl chloride, and ultimately non-toxic, chlorine-free end products in the form of ethene and ethane [6,7]. Many of these transformations can be performed cometabolically by methanogenic, acetogenic and sulfate-reducing microorganisms that produce enzymes containing transition metal cofactors (see [8,9] and references therein).…”

Inhibition of methanogenesis by C1‐ and C2‐polychlorinated aliphatic hydrocarbons

“…Chemically, the tri-and tetrachlorinated aliphatic hydrocarbons are highly oxidized and therefore are resistant to biological oxidation but are susceptible to reductive dechlorination by some anaerobic bacteria. There have been a number of observations of reductive dechlorination of polychlorinated hydrocarbons either by complex methanogenic cultures [2][3][4][5][6] or by pure cultures of methanogenic bacteria [6,[7][8][9][10][11][12]. Chloroform is mostly dechlorinated by methanogens to DCM [6,11], which can be further degraded slowly by acetogens in mixed methanogenic cultures [13,14].…”