Bioreactor for Continuously Metabolizing 1,4-Dioaxane to Less Than a Half Microgram Per Liter

1,4-Dioxane is a contaminant of emerging concern.  It is found above the health-based reference level (0.35 microgram/liter) in 6.9% of the U.S. public water systems. It is also found in many sites on the Environmental Protection Agency (EPA) National Priorities List (NPL).  Bioreactors that are filled with adsorbent for biofilm attachment are widely utilized for water treatment.  They have been studied for 1,4-dioxane removal.  In such reactors, biofilms continuously metabolize 1,4-dioxane to harmless forms by respiring oxygen.  Existing bioreactors are not able to remove 1,4-dioxane to close to the health-based reference level.  The main reason is that the environmentally relevant 1,4-dioxane concentrations (< tens of microgram/liter) cannot sustain growth of microbes. 

This invention adds a screen above the adsorbent in the bioreactor, which is operated in the up-flow mode.  The screen retained the detached biofilm that would have been out of the reactor.  By accumulating biomass, the reactor was able to degrade 1,4-dioxane to <0.5 microgram/liter, which is the detection limit of the equipment in the researchers’ laboratory.  The combination of a medium empty bed retention time and a low influent 1,4-dioxane concentration also plays a critical role in the success of the bioreactor. 

Advantages

• The bioreactor can be directly used to treat contaminated water.
• It can also be used to enrich 1,4-dioxane-metabolizing microbes.
• These can then be injected into contaminated sites through bioaugmentation for in-situ remediation.