Electron‐acceptor loadings affect chloroform dechlorination in a hydrogen‐based membrane biofilm reactor

Abstract

Chloroform (CF) can undergo reductive dechlorination to dichloromethane, chloromethane, and methane. However, competition for hydrogen (H 2 ), the electron-donor substrate, may cause poor dechlorination when multiple electron acceptors are present. Common acceptors in anaerobic environments are nitrate (NO 3 − ), sulfate (SO 4 2− ), and bicarbonate (HCO 3 − ). We evaluated CF dechlorination in the presence of HCO 3 − at 1.56 e − Eq/m 2 -day, then NO 3 − at 0.04-0.15 e − Eq/m 2 -day, and finally NO 3 − (0.04 e − Eq/m 2 -day) along with SO 4 2− at 0.33 e − Eq/m 2 -day in an H 2based membrane biofilm reactor (MBfR). When the biofilm was initiated with CFdechlorination conditions (no NO 3 − or SO 4 2− ), it yielded a CF flux of 0.14 e − Eq/m 2day and acetate production via homoacetogenesis up to 0.26 e − eq/m 2 -day. Subsequent addition of NO 3 − at 0.05 e − Eq/m 2 -day maintained full CF dechlorination and homoacetogenesis, but NO 3 − input at 0.15 e − Eq/m 2 -day caused CF to remain in the reactor's effluent and led to negligible acetate production. The addition of SO 4 2− did not affect CF reduction, but SO 4 2− reduction significantly altered the microbial community by introducing sulfate-reducing Desulfovibrio and more sulfur-oxidizing Arcobacter. Dechloromonas appeared to carry out CF dechlorination and denitrification, whereas Acetobacterium (homoacetogen) may have been involved with hydrolytic dechlorination. Modifications to the electron acceptors fed to the MBfR caused the microbial community to undergo changes in structure that reflected changes in the removal fluxes.

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

“…54 Dechloromonas was possibly responsible for CF reductive dechlorination. 55 Our results show that Acinetobacter, Sediminibacterium, Methyloversatilis, and Dechloromonas are the specic genera and bloom in H 2 /O 2 microcosm, indicating that they potentially transform CHCs through an aerobic or anaerobic pathway.…”

“…Some genera, such as Acinetobacter , Pseudomonas and Dechloromonas , have been associated with the bioremediation of aromatic hydrocarbons. 55,57 Many aromatic hydrocarbons degrading bacteria can co-metabolically degrade chloroethene, such as TCE, c DCE and VC. 10 Acinetobacter can utilize dimethyl sulfide (DMS) as the sole sulfur source and degrade TCE and three DCE isomers.…”

Two distinct Dehalobacter strains sequentially dechlorinate 1,1,1-trichloroethane and 1,1-dichloroethane at a field site treated with granular zero valent iron and guar gum

“…Certain Sulfurospirillum and Geobacter species have been shown to dechlorinate chlorinated ethenes (Buttet et al, 2013;Sung et al, 2006), but not chlorinated ethanes. Dechloromonas was reported to dechlorinate chloroform (Lai et al, 2019). We examined the relationship between Sulfurospirillum abundance and 1,1,1-TCA and 1,1-DCA biodegradation.…”