1,2-DCA biodegradation potential of an aquifer assessed in situ and in aerobic and anaerobic microcosms.

Background: 1,2-dichloroethane (1,2-DCA) biodegradation can occur through aerobic or anaerobic pathways that can be exploited in bioremediation strategies. Bioremediation interventions are site specific and generally based on anaerobic pathways, nevertheless expanding knowledge on proper conditions favoring the biodegradation and especially on 1,2-DCA degrading microorganisms is crucial. In this work the intrinsic biodegradation potential of an aquifer impacted by Chlorinated Aliphatic Hydrocarbons (mainly 1,2-DCA) was evaluated by characterizing the aquifer microbiome across space and time and by setting up biostimulation treatments in microcosms under different aerobic and anaerobic conditions, in parallel.

Results: The microbial profiling of the aquifer revealed noticeable alpha and beta diversity across the sampling sites within the aquifer and strong fluctuations over time. Surprisingly both the anaerobic and aerobic biostimulation treatments led to the successful removal of 1,2-DCA in microcosms, the enrichment of known 1,2-DCA degraders and the detection of reductive or hydrolytic dehalogenases. Ancylobacter and Starkeya were enriched in aerobic microcosms. Desulfovibrio and Desulfuromonas, known as perchloroethylene degraders, were enriched in anaerobic microcosms, suggesting they could be yet unknown 1,2-DCA respirers.

Conclusions: Our results demonstrate the occurrence of both aerobic and anaerobic bioremediation potential in the aquifer despite its negative redox potential. Due to the feasibility of direct oxidation with oxygen insufflation, we propose that an enhanced bioremediation strategy based on direct oxidation of 1,2-DCA could be applied to the contaminated aquifer as an ecofriendly, efficient and cost-effective approach as an alternative to anaerobic biodegradation.