Bioaugmenting the poplar rhizosphere to enhance treatment of 1,4-dioxane

1,4-Dioxane is a highly mobile and persistent groundwater pollutant that often forms large dilute plumes. Because of this, utilizing aggressive pump-and-treat and ex-situ technologies such as advanced oxidation can be prohibitively expensive. In this study, we bioaugmented the poplar rhizosphere with dioxane-degrading bacteria Mycobacterium dioxanotrophicus PH-06 or Pseudonocardia dioxanivorans CB1190 to enhance treatment of 1,4-dioxane in bench-scale experiments. All treatments tested removed 10 mg/L dioxane to near health advisory levels (<4 μg/L). However, PH-06-bioaugmented poplar significantly outperformed all other treatments, reaching <4 μg/L in only 13 days. Growth curve experiments confirmed that PH-06 could not utilize root extract as an auxiliary carbon source for growth. Despite this limitation, our findings suggest that PH-06 is a strong bioaugmentation candidate to enhance the treatment of dioxane by phytoremediation. In addition, we confirmed that CB1190 could utilize both 1,4-dioxane and root extract as substrates. Finally, we demonstrated the large-scale production of these two strains for use in the field. Overall, this study shows that combining phytoremediation and bioaugmentation is an attractive strategy to treat dioxane-contaminated groundwater to low risk-based concentrations (~1 μg/L).

Groundwater remediation from the past to the future: A bibliometric analysis

Groundwater is an important component of terrestrial ecosystems and plays a role in geochemical cycling. Groundwater is also used for agricultural irrigation and for the domestic supply of drinking water in most nations. However, groundwater contamination has led to many research efforts on groundwater remediation technologies and strategies. This study evaluated a total of 5486 groundwater remediation-related publications from 1995 to 2015 using bibliometric technology and social network analysis, to provide a quantitative analysis and a global view on the current research trend and future research directions. Our results underline a strong research interest and an urgent need to remediate groundwater pollution due to the increasing number of both groundwater contamination and remediation publications. In the past two decades, the United States (U.S.) published 41.1% of the papers and it was the core country of the international collaboration network, cooperating with the other 19 most productive countries. Besides the active international collaboration, the funding agencies also played positive roles to foster the science and technology publications. With respect to the analysis of the distribution of funding agencies, the National Science Foundation of China sponsored most of the groundwater remediation research. We also identified the most productive journals, Environmental Science and Technology and Journal of Contaminant Hydrology, which published 334 and 259 scientific articles (including research articles and reviews) over the past 20 years, respectively. In addition to journal publications, a patent analysis was performed to show the impact of intellectual property protection on journal publications. Three major remediation technologies, including chemical oxidation, biodegradation and adsorption, have received increasing interest in both journal publication and patent development. Our results provide a valuable reference and global overview to identify the potential obstacles and opportunities for researchers who currently work on groundwater contamination, remediation and related topics.