Impact of electron donors on chlorinated ethane degradation and native bacteria response in aged contaminated groundwater: A systematic study with insights

To systematically investigate the effects of three electron donors—namely, sodium lactate (SL), sodium pyruvate (SP), and sodium acetate (SA)—on the degradation of high concentration chlorinated ethanes (CEAs) and the diversity of native bacteria, in this work, we collected groundwater and aquifer soils from practical contaminated sites and conducted batch microcosmic experiments. We found that a low dose of SL was more beneficial to the deep dechlorination of CEAs via various pathways and could effectively shorten the half-life of 1,1,2-trichloroethane; however, excessive introduction had an inhibitory effect on microbial activity. The distribution of indigenous bacterial communities indicated that the system was gradually biased toward dominant anaerobic microorganisms under biostimulation culture conditions. The effect of electron donor type on indigenous bacterial communities was greater than the electron donor concentration, but this difference decreased with incubation time. Compared to SP and SA, SL was conducive to the more abundant and uniform development of the bacterial community. The stimulation effect on Desulfitobacterium and Dehalobacter was the strongest with an SL addition of 300 mg L−1, which corresponded to most the efficient degradation of CEAs.