Bench-scale biodegradation tests to assess natural attenuation potential of 1,4-dioxane at three sites in California

Abstract

1,4-Dioxane (dioxane) is relatively recalcitrant to biodegradation, and its physicochemical properties preclude effective removal from contaminated groundwater by volatilization or adsorption. Through this microcosm study, we assessed the biodegradation potential of dioxane for three sites in California. Groundwater and sediment samples were collected at various locations at each site, including the presumed source zone, middle and leading edge of the plume. A total of 16 monitoring wells were sampled to prepare the microcosms. Biodegradation of dioxane was observed in 12 of 16 microcosms mimicking natural attenuation within 28 weeks. Rates varied from as high as 3,449 ± 459 µg/L/week in source-zone microcosms to a low of 0.3 ± 0.1 µg/L/week in microcosms with trace level of dioxane (<10 µg/L as initial concentration). The microcosms were spiked with (14)C-labeled dioxane to assess the fate of dioxane. Biological oxidizer-liquid scintillation analysis of bound residue infers that 14C-dioxane was assimilated into cell material only in microcosms exhibiting significant dioxane biodegradation. Mineralization was also observed per (14)CO2 recovery (up to 44% of the amount degraded in 28 weeks of incubation). Degradation and mineralization activity significantly decreased with increasing distance from the contaminant source area (p < 0.05), possibly due to less acclimation. Furthermore, both respiked and repeated microcosms prepared with source-zone samples from Site 1 confirmed relatively rapid dioxane degradation (i.e., 100 % removal by 20 weeks). These results show that indigenous microorganisms capable of degrading dioxane are present at these three sites, and suggest that monitored natural attenuation should be considered as a remedial response.

Biodegradation of 1,4-dioxane: Effects of enzyme inducers and trichloroethylene

“…Chemical oxidation like chlorination (Klečka and Gonsior, 1986) and advanced oxidation techniques are impractical for remediating large diluted plumes (Adams et al, 1994;Félix-Navarro et al, 2007;Stefan and Bolton, 1998). Similarly, while natural attenuation is possible for 1,4-dioxane, it is not ubiquitous (Chiang et al, 2012;Li et al, 2013Li et al, , 2014Sei et al, 2010). However, 1,4-dioxane is biodegradable.…”

Sustainable Remediation Considerations for Treatment of 1,4‐Dioxane in Groundwater

“…Chiang et al (2006Chiang et al ( , 2007Chiang et al ( , 2008 reported a similar half-life was required in attempts to model a 1,4-dioxane plume from a manufacturing facility. Li et al (2015a) found 1,4-dioxane biomarkers present at three of four California sites, and Li et al (2014Li et al ( , 2015b found native degraders at multiple sites were capable of degrading 1,4-dioxane in microcosms. More work is required in this area because the findings above are somewhat in conflict with the conventional wisdom regarding degradation of 1,4-dioxane.…”

“…Li et al. () found 1,4‐dioxane biomarkers present at three of four California sites, and Li et al. (, ) found native degraders at multiple sites were capable of degrading 1,4‐dioxane in microcosms.…”

1,4‐Dioxane Treatment Technologies

“…A second data mining effort that estimated decline in concentrations in wells over time suggested DX was degrading at rates similar to groundwater contaminants that are known to degrade, such as commingled chlorinated VOCs (Adamson et al, 2015). A study of DX groundwater sites in California indicated evidence of DX degraders present at all three sites (Li et al, 2014). In microcosm studies performed at Rice University, DX concentrations declined over time relative to killed control microcosms, suggesting biodegradation was active at these sites.…”