1,4-dioxane is a synthetic chemical used in a variety of industries and produced as a byproduct or impurity in household and industrial products.
It was detected above 0.35 μg/L (the 10-6 cancer risk level) in approximately 7% of the drinking water systems during the USEPA's Third Unregulated Contaminant Monitoring Rule (UCMR3), the second highest exceedance frequency among the contaminants monitored in UCRM3. There is no federal maximum contaminant level (MCL), but several states have taken regulatory actions. The physical and chemical properties of 1,4-dioxane lead to ineffective treatment by the most commonly used water treatment processes, and the only effective treatment technology is advanced oxidation process (AOP). Similarly, 1,4-dioxane needs to be treated for potable reuse. Domestic wastewater typically contains about 1 to 10 μg/L of 1,4-dioxane which passes through all the unit processes in water reuse treatment trains, except for AOPs in the "full advanced treatment" (FAT) process.
AOP treatment has some disadvantages and the industry (particularly small systems in rural areas) needs an alternative. Recent progress in research has demonstrated that 1,4-dioxane is biodegradable, but most researchers believe that a low concentration, such as the regulatory levels imposed or proposed by multiple states, can only be achieved with a co-metabolic process which requires the addition of a second substrate as the carbon and energy source. The second substrate is usually an alkane gas, which creates problems in chemical handling, cost, and demand for operator attention. Only a metabolic biological treatment process for 1,4-dioxane would significantly overcome these issues.
This presentation will describe the proof of concept for metabolic treatment of 1,4-dioxane in drinking water by biofiltration. The bench-scale biofiltration columns were packed with a porous media, which acted as a weak adsorbent for 1,4-dioxane, and inoculated by a naturally occurring mixed microbial culture capable of degrading 1,4-dioxane at low concentrations. Two biofiltration columns were operated concurrently at the influent 1,4-dioxane concentrations of 25 and 500 μg/L, respectively, as the sole carbon and energy source for the culture for over two years. Media tested included granular activated carbon (GAC) and a variety of common and proprietary adsorbents. The empty bed contact time (EBCT) was varied from 0.3 to 3 hours. For each set of operating conditions, influent and effluent 1,4-dioxane concentrations were monitored until the effluent concentration reached a steady state for at least four weeks.
Preliminary results showed that a significant percentage of 1,4-dioxane can be removed with biofiltration using GAC. The bioreactor performance was affected more significantly by EBCT than by the influent concentration. Types of adsorbent had a major impact on 1,4-dioxane removal. The maximum steady-state removal efficiency achieved during the bench testing was 99%.
- Geosyntec Authors: Chao Zhou, Bryan VanDuinen, Brian Petty
- All Authors: Chao Zhou, Bryan VanDuinen, Brian Petty
- Title: 25th Triennial Borchardt Conference – Symposium on Advancements in Water and Wastewater
- Event or Publication: Event
- Practice Areas: Water and Natural Resources
- Citation: Chao Zhou, P.E. (California) and Bryan VanDuinen, P.E. (Michigan) will present at the 25th Triennial Borchardt Conference – Symposium on Advancements in Water and Wastewater at the University of Michigan in Ann Arbor, Michigan on February 25 - 26, 2020.
- Date: February 25-26, 2020
- Location: Ann Arbor, Michigan
- Publication Type: Platform Presentation