Interior of Greater Cincinnati Water Works' Granular Activated Carbon (GAC) contactor building. The 240-mgd post-filtration GAC facility with onsite reactivation removes contaminants such as pharmaceuticals by adsorption. Photo: Greater Cincinnati Water Works
Ozone generators at River Mountains Water Treatment Facility in Las Vegas treat up to 300 mgd of water each day. Photo: Southern Nevada Water Authority
By Robert Renner
No one — not even the U.S. EPA — argues that endocrine disruptors (EDCs) and pharmaceuticals and personal care products (PPCPs) shouldn't concern drinking water utility managers or their customers. But science hasn't proven these compounds pose a health risk to humans.
Every day, the active chemicals in herbicides and fungicides, cosmetics, and medicine are released into the environment through agricultural runoff, industrial operations, and human and animal waste. Inevitably, they're found in source and sometimes in finished water.
A 2008 series of Associated Press articles described how these compounds are found in 41 million Americans' tap water, prompting a Congressional inquiry. But while endocrine disruptors in particular are blamed for feminizing male fish, it's not clear that the levels at which the compounds occur — in some cases, parts per trillion — harm humans.
That same year the Water Research Foundation released Toxicological Relevance of Endocrine Disruptors and Pharmaceuticals in Drinking Water, an analysis of 62 representative chemicals. Risk evaluations for exposure through drinking water were conducted for 16 pharmaceuticals, 10 potential EDCs, and three steroid hormones. Researchers developed acceptable daily intakes for determining exposure levels not likely to be associated with adverse health effects. None of the concentrations exceeded those levels, a finding echoed by EPA upon its second six-year review of the compounds.
Both classes of compounds are moving up EPA's regulatory hierarchy, but the agency provides little guidance for monitoring, treating, and communicating their potential or actual effects. The agency added some to Contaminant Candidate List 3 in 2009. But less than a year later, in March 2010, its second six-year review of drinking water standards recommended no revisions for compounds such as alachlor (used in herbicides) and toluene (used in plastics manufacturing). Nor has EPA revised the existing maximum concentration limit of 3 micrograms/liter for the regulated chemical atrazine, a widely used agricultural herbicide.
So as managers prepare for the Stage 2 Disinfectants and Disinfection ByProducts Rule, which requires finished water to be tested using a primary or residual disinfectant other than ultraviolet (UV) light, they face a conundrum: Do they surpass the rule's current requirements by investing in technology that removes unregulated compounds? Or do they spend whatever's necessary to satisfy the rule's requirements now and address these compounds/contaminants when (or if) the agency decides they should be regulated?
Unfortunately, no single treatment process removes all EDCs and PPCPs.
The foundation found that ozone removes most. So do advanced oxidation processes such as ozone/peroxide and UV/peroxide, but they don't eliminate atrazine, X-ray contrast media, and flame retardants. While more effective than chloramination, chlorine only removes about half of the compounds investigated and it's one of the many treatments (aside from UV light) that has come under scrutiny in the byproducts rule. Biological filtration, nanofiltration, reverse osmosis, and granular activated carbon are highly effective, but also very expensive.
“Removing these compounds requires a robust combination of treatment technologies,” says Water Research Foundation Senior Project Manager Alice Fulmer. “Many are not only expensive but require a lot of energy.”
Depending as they do on such site-specific factors as source water quality, existing treatment train, design flow, and average flow, exact cost comparisons are difficult to calculate. Fulmer estimates ozonation for a plant with a design flow of 100,000 gallons per day (gpd) and daily flow of 30,000 gpd would require a $400,000 capital investment and $71,175 annually in operations and maintenance. Granular activated carbon for the same plant is approximately $150,000 and $57,488, respectively.
Depending on treatment system size and required retrofit, utilities begin their first year of compliance monitoring for the DBP rule between 2012 and 2016. Compliance is expected to cost the nation's water providers — both public and private — $79 million annually.
Although none treats specifically for EDCs and PPCPs, we asked managers in Philadelphia, Las Vegas, and Cincinnati how their operations test, or plan to test, for unregulated compounds and how they communicate these efforts.