EDC Treatments Put to the Test
Study compares different methods’ effectiveness at removing endocrine disrupting compounds, drugs and personal-care products
- By Debbie Bolles
- Mar 18, 2008
Reverse osmosis (RO) proved the most effective method for treating contaminants such as endocrine disrupting compounds (EDCs) in a four-year study that compared the ability of different contaminant removal technologies.
The research, conducted by the American Water Works Association Research Foundation (AwwaRF), also gave high marks to ozone, advanced oxidation, nanofiltration and activated carbon as “superior” at removing pharmaceuticals and personal-care products (PPCPs) and EDCs.
“It provides utilities with an idea of how effective their current processes can be and allows them, as they look toward future expansion and future infrastructure changes, to have a good comprehension of what various treatment options would do,” said Shane Snyder, a principal investigator on the project who works for a research division of the Southern Nevada Water Authority.
The foundation’s report, “Removal of EDCs and Pharmaceuticals in Drinking and Reuse Treatment Processes,” analyzes and documents the ability of conventional and advanced water treatment processes to remove 36 EDCs and PPCPs likely to be found in source waters. The testing occurred at 20 drinking water utilities and six water reuse plants across the United States. AwwaRF published its findings in August.
(These drinking water utilities do not represent the average utility. Researchers purposely chose utilities treating source waters with known wastewater influence for their greater potential to detect EDC/PPCP concentrations and to evaluate different removal processes.)
The study rated these methods "highly effective" at removing contaminants: RO, nanofiltration, activated carbon, advanced oxidation processes and high-energy ultraviolet irradiation at oxidative doses. Methods deemed "least effective" were conventional coagulation, flocculation and sedimentation, magnetic ion-exchange and ultraviolet irradiation at disinfection doses.
The research team included Snyder, Eric Wert, and Hongxia (Dawn) Lei, all with the Water Quality Research and Development Division at the Southern Nevada Water Authority, and Paul Westerhoff and Yeomin Yoon from the Department of Civil and Environmental Engineering at Arizona State University.
Among other study conclusions:
- Free chlorine disinfection removed many target compounds, depending on the structure of the contaminant.
- Chloramines were less effective than free chlorine at EDC/PPCP removal.
- Ozone, found to be more effective than chlorine, removed the majority of tested contaminants.
- Biological removal and sorption processes reduced the concentrations of many target analytes during riverbank filtration, biological filtration, and soil aquifer treatment.
- Treatment methods combining various processes were the most effective at removing trace concentrations of EDCs and PPCPs.
One Size Does Not Fit All
Selecting the right treatment method depends on cost, a utility’s scale and how pervasive a certain contaminant may be in water or wastewater.
“For the maximum amount of removal without consideration of energy costs, it’s clear that reverse osmosis is the most effective,” said Snyder, with RO removing 80 percent to 99 percent of contaminants tested. “However, if we take into account the water loss during reverse osmosis and the energy consumption for the average utility, it would appear the most promising options are ozonation, UV advanced oxidation and activated carbon."
In disinfectants, ozone proved the most powerful at removing the targeted contaminants, with more than 50 percent removed to below detection by typical disinfection doses.
With activated carbon, test results were mixed. Researchers termed this method “effective” in the study. Powdered activated carbon successfully removed the target compounds, although dose and contact time were critical to achieve good results. Tests using granular activated carbon showed excellent removal capability at utilities that routinely regenerated the carbon; however, those with granular activated carbon that had been in service a long time saw “little or no removal of contaminants,” according to the report.
UV advanced oxidation provided “excellent removal for nearly all target compounds,” the report said. Oxidizing the majority of EDCs and PPCPs, however, required an ultraviolet dose significantly greater than that commonly used for disinfection.
Of other treatment processes, the study found that ultrafiltration and microfiltration “were of little value for contaminant removal in general” and that nanofiltration “provided good removal of many target compounds at all scales.”
What’s in the Water?
Along with testing various treatment methods, the study examined the presence of EDCs and PPCPs at 20 full-scale water utilities.
Researchers found the pesticide DEET common in both raw and finished drinking waters, with 100 percent occurrence in raw waters and 90 percent occurrence in finished waters.
Pharmaceuticals most frequently found in raw drinking water (in more than 80 percent of samples) were carbamazepine, dilantin, sulfamethoxazole and meprobamate. In finished drinking water, contaminants of greatest occurrence (more than 65 percent of samples) were meprobamate, dilantin, ibuprofen and iopromide. The pesticide atrazine occurred in the largest concentrations of any contaminants in both raw and finished drinking water, yet levels were well below the maximum contaminant limit of 3,000 ng/L.
Hormones were found infrequently, or not at all, while pharmaceuticals rarely occurred in concentrations greater than 10 ng/L in raw and finished drinking waters.
“Since EDCs and PPCPs occur in U.S. drinking water only at minute concentrations, it is highly unlikely that most of these chemicals will pose any credible threat to human health via drinking water exposure,” the report stated.
Snyder said the study provided good information on the efficacy of treatment methods for removal of specific contaminants, yet scientists still don’t know enough about the effects of these microscopic compounds, if any, on humans.
Studies have shown that EDCs impact estrogen, androgen and/or thyroid hormone function in animals such as fish, resulting in some unusual genetic changes such as male fish exhibiting female characteristics in some waterways. Natural and synthetic estrogens have been reported in U.S. wastewaters since the 1960s, but not until recent years has analytical technology improved enough to detect such water contaminants at trace levels.
“This particular study did not go into the risks or health effects [to humans] related to these chemicals,” said Snyder, adding that a new AwwaRF study will analyze potential human health risks.
No current federal regulations mandate removal of EDCs and PPCPs. However, utilities may wish to plan ahead should these contaminants come under future scrutiny, which many believe is likely.
“The overall message is that there are commercially available processes to reduce the concentrations of micro-contaminants that are ubiquitous in the environment,” Snyder said. “My prediction is that removal would have to take place in the wastewater treatment process, not drinking water process, if EPA in the future decides to regulate removal of micro-contaminants.”
For more information or to purchase the report, go to www.awwarf.org/research/TopicsAndProjects/execSum/2758.aspx.