1,4-dioxane is a probable human carcinogen frequently found in water and wastewater systems at concentrations above the EPA one-in-one-million cancer risk level of 0.35 ug/L. 1,4-dioxane is not well removed through conventional treatment methods due to its polarity and resistance to biodegradation, especially when present at low (μg/L) concentrations. Cometabolic degradation of 1,4-dioxane has been achieved in groundwater remediation by stimulating bacteria carrying cyclic ether-degrading soluble diiron monooxygenases (SDIMOs) through the addition of simple alkane gases, such as propane. A recent pilot-scale study demonstrated that addition of such co-substrates prior to biological active filtration (BAF) holds potential as a novel potable reuse treatment approach that can effectively remove 1,4-dioxane.
Characterization of the microbial communities associated with propane-induced cometabolism of 1,4-dioxane has largely been limited to culture or polymerase chain reaction (PCR)-dependent methods, which are highly limited in throughput, generally providing information about one organism or one gene at a time. Shotgun metagenomic sequencing is a high-throughput nontargeted means of broadly profiling microbial taxa and functional genes involved in various metabolic processes. In this thesis, methods for DNA extraction from granular activated carbon applied to full-scale BAF amended with propane for the purpose of 1,4-dioxane cometabolism were optimized and metagenomic sequencing was performed. Insights were gained into the microbes and functional genes involved in 1,4-dioxane biodegradation, furthering our understanding of a potentially powerful new water reuse treatment technology that effectively polishes recalcitrant contaminants. / Master of Science / Water reuse systems use advanced wastewater treatment technologies to treat wastewater to such high standards that it can even be used as a source for drinking water. Expanding water reuse is a vital means of protecting water resources, but the treatments can be very costly. Biofiltration is a reuse treatment technology in which water is filtered through media - such as activated carbon - that is commonly used in household filtration systems, providing surface area for the growth of beneficial microorganisms that can naturally biodegrade contaminants in the water. Some contaminants are more difficult to degrade than others, especially trace levels of pharmaceuticals and personal care products. One common manufacturing ingredient that ends up in wastewater and is difficult to biodegrade is 1,4-dioxane, a compound that is potentially carcinogenic to humans at μg/L concentrations when consumed via drinking water over a lifetime.
It was recently discovered that adding propane to a biofilter can help to improve biodegradation of 1,4-dioxane down to very low levels. Propane acts as a co-metabolite, i.e., providing a food source on which 1,4-dioxane-degrading bacteria can thrive. In this study, DNA sequencing technology was applied to help identify the bacteria that are responsible for co-metabolic degradation of 1,4-dioxane in a granular activated carbon biofilter. The research was conducted at a demonstration-scale research facility that is investigating innovative ways to treat wastewater to levels that are suitable for recharging a groundwater aquifer that is used as a drinking water source. The main contributions of this study include an optimized protocol for obtaining DNA from the BAF media for DNA sequencing and new insight into the bacteria and enzymes involved in co-metabolic degradation of 1,4-dioxane.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119537 |
| Date | 26 June 2024 |
| Creators | Scott, Katherine Denise |
| Contributors | Environmental Science and Engineering, Pruden-Bagchi, Amy Jill, Widdowson, Mark A., Bott, Charles B. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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