Integrated Anaerobic-Aerobic Biodegradation of Multiple Contaminants Including Chlorinated Ethylenes, Benzene, Toluene, and Dichloromethane

Abstract

Complete bioremediation of soils containing multiple volatile organic compounds (VOCs) remains a challenge. To explore the possibility of complete bioremediation through integrated anaerobic-aerobic biodegradation, laboratory feasibility tests followed by alternate anaerobic-aerobic and aerobic-anaerobic biodegradation tests were performed. Chlorinated ethylenes, including tetrachloroethylene (PCE), trichloroethylene (TCE), cis-dichloroethylene (cis-DCE), and vinyl chloride (VC), and dichloromethane (DCM) were used for anaerobic biodegradation, whereas benzene, toluene, and DCM were used for aerobic biodegradation tests. Microbial communities involved in the biodegradation tests were analyzed to characterize the major bacteria that may contribute to biodegradation. The results demonstrated that integrated anaerobic-aerobic biodegradation was capable of completely degrading the seven VOCs with initial concentration of each VOC less than 30 mg/L. Benzene and toluene were degraded within 8 days, and DCM was degraded within 20 to 27 days under aerobic conditions when initial oxygen concentrations in the headspaces of test bottles were set to 5.3% and 21.0%. Dehalococcoides sp., generally considered sensitive to oxygen, survived aerobic conditions for 28 days and was activated during the subsequent anaerobic biodegradation. However, degradation of cis-DCE was suppressed after oxygen exposure for more than 201 days, suggesting the loss of viability of Dehalococcoides sp., as they are the only known anaerobic bacteria that can completely biodegrade chlorinated ethylenes to ethylene. Anaerobic degradation of DCM following previous aerobic degradation was complete, and yet-unknown microbes may be involved in the process. The findings may provide a scientific and practical basis for the complete bioremediation of multiple contaminants in situ and a subject for further exploration.

Challenges of solving the problem of soil and groundwater contamination

“…For the decomposition of VOCs using microorganisms, we conducted decomposition tests under conditions replicating combined pollution that occurs at actual contamination sites rather than on a single contaminant. [18] [19] Moreover, in decomposition of combined pollution, we identified which microorganism contributed to the decomposition of which contaminant using stable isotope probing. [20] R&D is all conducted with practical application in mind.…”

“…To contribute to risk communication of heavy metal contamination and to land use planning in the next generation, the Geo-Environmental Fig. 4 Example of complete decomposition of multiple VOCs using environmental microorganism [19] Risk Research Group compiled the "Geochemical and Risk Assessment Map of Subsurface Soils" which considers the total concentration, leaching concentration of various elements including heavy metals in the subsurface soil, as well as the local industrial structure and the lifestyle of residents. The compilation of these maps was completed for the prefectures of Miyagi, Toyama, Tottori, Ibaraki, and Kochi, and the maps are available on the web (https://unit.aist.…”

Distribution of Dehalococcoides 16S rRNA and Dehalogenase Genes in Contaminated Sites

“…2; The sediment sample for microbial analysis was homogenized and mixed in the tube, followed by DNA extraction from 0.5 g of the sediment sample. The DNA was extracted with the FastDNA™ SPIN Kit for Soil (Q-BIO Gene, Irvine, CA, USA) (Yoshikawa, Zhang, & Toyota, 2017). When the sediment sample was applied to the kits, 20 mg skim milk was added to increase the efficiency of DNA extraction (Takada-Hoshino & Matsumoto 2004;Yoshikawa et al, 2017).…”

“…Concrete pavement reduces oxygen infiltration into the soil (Viswanathan, Volder, Watson, & Aitkenhead-Peterson, 2011). Yoshikawa et al (2017) showed successful degradation of chlorinated ethylenes to harmless ethylene by Dehalococcoides after exposure to oxygen when soil particles existed in the test environment.…”

Biodegradation of Volatile Organic Compounds and Their Effects on Biodegradability under Co-Existing Conditions

“…Alexander ( 4 ) reported that the effects of one VOC on other co-existing VOCs are largely unknown, and these effects have rarely been examined. Yoshikawa et al ( 208 ) recently described a successful case study on the complete biodegradation of multiple VOCs including chlorinated ethenes, benzene, toluene, and dichloromethane through integrated anaerobic-aerobic biodegradation.…”