Treating 1,4-Dioxane Contamination in Drinking Water

Clean and safe drinking water is essential for communities to thrive. Residents count on municipal and local government leaders to stay informed about both known and emerging contaminants so that water systems can continue providing high-quality water for their daily needs. One contaminant that is moving into the national spotlight in terms of both public concern and regulatory momentum is 1,4-dioxane. This synthetic chemical, often found in industrial solvents, has the potential to infiltrate water sources and pose a threat to the health and safety of communities. Exposure to it through drinking water contamination has been associated with an increased risk of liver toxicity and cancer.

As data continues to show the dangerous health effects of exposure to 1,4-dioxane, there has also been movement toward the establishment of updated EPA guidelines for the chemical. Several states have already enacted their own maximum contaminant levels (MCLs) as well. With attention surrounding 1,4-dioxane in drinking water steadily increasing, local decision-makers can stay ahead of potential issues by becoming aware of the most effective treatment methods for this contaminant.

Below, we describe the water treatment solutions that have proven effective in studies so far. While research into new methods is ongoing, municipal leaders who understand how to remove 1,4-dioxane from drinking water may benefit from evaluating their local water systems’ needs and available options before potential upcoming regulations take effect.

Effective Technologies for 1,4-Dioxane Drinking Water Treatment

Since 1,4-dioxane water contamination is often found deep in groundwater aquifers and wells, pump and treat remediation is the primary method of treatment used to remove this contaminant. This means that water is pumped out from groundwater, treated to remove 1,4-dioxane, then returned to the environment, either by discharging it into surface water sources or reinjecting it into groundwater sources. Pump and treat remediation not only makes groundwater safer for potential later use as a drinking water source, but it can also help control the migration of 1,4-dioxane plumes, preventing them from spreading into other areas and affecting additional populations. The most effective treatment processes used to remove 1,4-dioxane, as well as those that have been found ineffective, are outlined below.

Advanced Oxidation Processes (AOPs)

Advanced oxidation processes (AOPs) are considered to be the most effective treatment processes for 1,4-dioxane removal, routinely achieving greater than 99 percent reduction of contaminants. Two of the most common AOPs utilize hydrogen peroxide with ultraviolet (UV) light and hydrogen peroxide with ozone. Other AOPs have also been found to be effective, including UV light combined with titanium dioxide and hydrogen peroxide combined with ferrous iron (Fenton's reaction). An experienced environmental engineering firm can help determine the ideal treatment methods for each specific situation.

In AOPs that utilize hydrogen peroxide with UV light, the first step is to pretreat contaminated water if necessary to achieve ideal conditions for treatment. The water is then mixed with hydrogen peroxide. Then, the water passes through a system of UV lamps, causing a reaction that oxidizes organic contaminants. Finally, the pH is optimized again if necessary for release into the environment. The process is similar in systems that do not use UV light, but ozone or other substances are added during treatment instead of passing the water through UV lamps. This causes a similar oxidation process to occur.

Despite the high effectiveness of AOPs in the treatment of water contaminated with 1,4-dioxane, there are some limitations to their use in public water systems. For example, if the contaminated water contains bromide, adding ozone to the water will produce bromate. The International Agency for Research on Cancer (IARC) has classified bromate as a Group B2 (probable human) carcinogen. The risk of producing bromate during 1,4-dioxane treatment can be reduced by pretreating the water to decrease its pH level, then restoring pH to a safe level before returning treated water to the environment. Multiple case studies have shown success with this pretreatment strategy within water systems, helping them achieve optimal results with AOPs.

High turbidity, or cloudiness, of contaminated water may also limit the effectiveness of AOPs. If UV light is to be used, pretreatment may be necessary to reduce the turbidity. This allows the light to reach through the water better, maximizing the effects of treatment.

Reverse Osmosis Membrane Separation

Reverse osmosis, a common PFAS removal treatment method, has seen mixed results for 1,4-dioxane removal in studies at various scales. While some pilot studies showed potential for success, full-scale studies have reported rates of contaminant removal ranging from only 69 to 85 percent. One of the primary challenges for the use of reverse osmosis for 1,4-dioxane treatment is the very small molecular size of the chemical. As a result, the contaminant can easily pass through certain types of membranes typically used for this treatment method. Membrane separation can be used in conjunction with other methods to achieve better results.

Ineffective 1,4-Dioxane Treatment Methods

Unfortunately, many treatment systems that are very effective at removing other contaminants, such as PFAS, do not successfully remove 1,4-dioxane. This means that water systems that detect 1,4-dioxane through water quality testing will likely need to explore additional treatment solutions if regulations go into effect for the chemical. The following are methods that

Absorptive Media and Granular Activated Carbon (GAC)

Adsorptive media and granular activated carbon (GAC) are methods frequently used to remove PFAS from drinking water. Under very specific conditions, these strategies have been shown to remove some 1,4-dioxane, achieving only around 18 percent removal in column studies. While they may be used in combination with other, more effective, treatment solutions, water systems with 1,4-dioxane detections will not be able to depend on adsorptive media or GAC alone.

Chlorination

Chlorination, while found in some studies to be effective, also produces dangerous byproducts when used on water contaminated with 1,4-dioxane. These byproducts are significantly more toxic than 1,4-dioxane itself, making chlorination an undesirable method of water treatment in this case.

Other Ineffective Treatment Solutions

Most of the processes used in conventional water treatment fail to remove 1,4-dioxane sufficiently. Methods including aeration, permanganate addition, hydrogen peroxide addition in the absence of UV light or other additives used in AOPs, ozonation, powdered activated carbon, and UV irradiation alone have also proved unsuccessful at removing the contaminant. While 1,4-dioxane is not necessarily a “forever chemical” like PFAS, it is resistant to traditional water treatment due to its unique chemical and physical properties.

Emerging Technologies

Phytoremediation

Phytoremediation, or the use of plants to clean up contaminated environments, has been researched as a potential solution for 1,4-dioxane water contamination. Pilot-scale studies have shown promise in the use of hybrid poplars to take up the chemical from shallow groundwater and degrade or deactivate it.

Biological Treatment

Biological treatment has also been shown to be highly effective in laboratory studies. These methods employ the use of specific strains of bacteria that degrade 1,4-dioxane in bioreactors under specific conditions. However, co-contaminants were also found to interfere with biological treatment methods, leading to concerns over the reliability and accessibility of these treatment methods.

Funding Options for 1,4-Dioxane Treatment Costs

1,4-dioxane contamination is an emerging threat to water systems and municipalities across the country. While research has shown certain treatment methods to be more effective than others in the removal of this contaminant, each water system must determine the appropriate solutions for their unique needs. The best practice is to consult a treatment expert who can match your site specifics with the right technology to continue providing safe, clean water to your community.  

Regardless of which treatment solutions are selected, the expense of installing new or updated treatment facilities, continuing operation costs, and ongoing monitoring are likely to be a burden on water systems and ratepayers. If you are curious about the cost recovery solutions available to municipalities and water systems, schedule a free, no-obligation consultation with the team at SL Environmental Law Group.