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Cometabolic bioremediation is trending for the treatment of 1,4-dioxane (dioxane) and other emerging contaminants to meet stringent regulatory goals ( e.g. , <10 μg L −1 ) since biodegradation activities can be fueled by the supplementation of auxiliary substrates. In this study, we compared and investigated the effectiveness of two types of common auxiliary substrates, short-chain alkane gases ( e.g. , propane and butane) and primary alcohols ( e.g. , 1-propanol, 1-butanol, and ethanol), for dioxane removal in diverse environmental matrices with Azoarcus sp. DD4 as the inoculum. Physicochemical characterization at the pure culture level revealed that propane and 1-propanol are advantageous for stimulating cell growth and dioxane biodegradation by DD4. Parallel microcosm assays were conducted to assess the compatibility of DD4 bioaugmentation in diverse microbiomes recovered from five different environmental samples, including shallow and deep aquifer groundwater, contaminated river sediment, and municipal activated sludge. Propane was effective in sustaining efficient dioxane removal and the dominance of DD4 across all environmental matrices. Notably, amendment with 1-propanol promoted superior dioxane degradation in the deep aquifer groundwater, in which low pre-treatment biomass and post-treatment diversity were observed, suggesting its potential for intrinsic field applications. The combination of microbial community analysis and differential ranking identified that Ochrobactrum and several other indigenous bacteria were boosted by the inoculation of DD4, implying their commensal or mutualistic relationship. Collectively, propane and 1-propanol can be effective auxiliary substrate alternatives tailored for in situ bioaugmentation and their effectiveness is affected by the density and structure of environmental microbiomes.
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Distribution of a Sulfolane-Metabolizing Rhodoferax sp. Throughout a Contaminated Subarctic Aquifer and Two Groundwater Treatment Systems
An extensive plume of the emerging contaminant sulfolane has been found emanating from a refinery in Interior Alaska, raising questions about the microbial potential for natural attenuation and bioremediation in this subarctic aquifer. Previously, an aerobic sulfolane-assimilating Rhodoferax sp. was identified from the aquifer using stable isotope probing. Here, we assessed the distribution of known sulfolane-assimilating bacteria throughout the contaminated subarctic aquifer using 16S-rRNA-amplicon analyses of ~100 samples collected from groundwater monitoring wells and two groundwater treatment systems. One treatment system was an in situ air sparging system where air was injected directly into the aquifer. The other was an ex situ granular activated carbon (GAC) filtration system for the treatment of private well water. We found that the sulfolane-assimilating Rhodoferax sp. was present throughout the aquifer but was significantly more abundant in groundwater associated with the air sparge system. The reduction of sulfolane concentrations combined with the apparent enrichment of sulfolane degraders in the air sparging zone suggests that the addition of oxygen facilitated sulfolane biodegradation. To investigate other environmental controls on Rhodoferax populations, we also examined correlations between groundwater geochemical parameters and the relative abundance of the Rhodoferax sp. and found only manganese to be significantly positively correlated. The sulfolane-assimilating Rhodoferax sp. was not a major component of the GAC filtration system, suggesting that biodegradation is not an important contributor to sulfolane removal in these systems. We conclude that air sparging is a promising approach for enhancing the abundance and activity of aerobic sulfolane-degraders like Rhodoferax to locally stimulate sulfolane biodegradation in situ .
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- Award ID(s):
- 1636476
- PAR ID:
- 10313868
- Date Published:
- Journal Name:
- Frontiers in Microbiology
- Volume:
- 12
- ISSN:
- 1664-302X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fmicb.2021.714769
