Water utilities have come under increasing scrutiny as the agencies responsible for controlling human exposure to pharmaceuticals, endocrine disrupting compounds and other compounds of emerging concern (CECs) in drinking water. For example, a Associate Press article reported on the presence of pharmaceuticals in the drinking water of 24 major American metropolitan areas. This report prompted public concern and put additional pressure on water utilities to respond to what was presented as a threat to public health.
Most CECs are likely benign to humans at the concentrations detected in the environment and in drinking water. They are of concern, however, because many of these compounds are Endocrine Disrupting Compounds (EDCs), which can have effects on the human endocrine system at extremely low concentrations.
More importantly, the issue of EDCs is becoming a growing public concern following these reported studies additionally linking endocrine disruptors to adverse biological effects in aquatic life, further giving rise to the concern that low-level exposure through drinking water might poise a threat to human health. There is also evidence that some CECs that aren’t EDCs demonstrate more traditional toxicity towards aquatic organisms at environmentally relevant concentrations.
One of the significant routes for CEC into environment is through the discharges from wastewater treatment plants (WWTPs). While more research needs to be conducted regarding the human and aquatic health effects of CECs, it is likely that these compounds represent the next realm of regulatory concern, and that their removal will drive the research agenda, and the selection of water and wastewater treatment processes in the future.
CECs are ubiquitous downstream of wastewater discharges
While many of CECs have been present in the environment for decades, concern about their possible effects on humans and wildlife is being driven by improved analytical techniques that are able to detect them at decreasingly lower concentrations. In general, these compounds are present at trace concentrations (i.e. part per trillion or less), in complex mixtures.
CECs encompass a large number of different types of compounds, as described in Table 1. Compounds can be grouped either by their intended use, such as pharmaceutical products or surfactants, or by their potential environmental or human health effects. For example, endocrine disruptors, which interfere with human or animal hormonal function, sometimes at very low levels, are comprised of trace constituent classes such as pharmaceuticals, personal care products, detergent metabolites, plasticizers, brominated flame retardants and pesticides. Additionally, individual compounds within a class can have significantly different toxicities and fate within WWTPs and in the environment.
CECs are have been detected in surface waters and groundwater downstream or downgradient of wastewater discharges. Much of the early occurrence survey work was conducted in Europe – particularly Germany and Switzerland – where high population densities, and low per capita water use, leads to relatively high concentrations of CECs in wastewater and receiving waters. Even illegal drugs such as cocaine are detectable in some surface waters that are impacted by wastewater (Zuccato, E., et al, 2005).
There has been, and continues to be, a significant amount of investigation into the presence of CECs in the environment in North America. For example, (Kolpin, D.W., et al, 2002) at the USGS performed a survey of trace organic contaminants in US surface waters, and detected 82 of 95 individual CECs on their analyte list, with low levels detected in almost all samples. As a testament to the attention this topic has been attracting, the resulting report from the USGS survey was the most-downloaded article ever published in the periodical “Environmental Science and Technology.”
David Sedlak, a professor at the University of California at Berkeley, and the principle investigator of an AWWARF-sponsored occurrence survey of pharmaceuticals in wastewater effluent, has been researching the fate and transport of CECs over the last decade. He commented, “At this point, it’s not whether we can find them. We see them everywhere. The question now is whether they’re having adverse effects on wildlife populations, and what can we do about it.”
CECs in Wastewater Adversely Affect Aquatic Organisms
There has been considerable attention in the last several years from both the public and the scientific and wastewater communities on the potential ecological effects of trace constituents. For example, over the past two years, significant media coverage was given to reports that up to 100 percent of the male smallmouth bass in some sections of the Chesapeake Bay watershed are intersex (Associated_Press, 2006).
Wildlife are exposed to CECs and endocrine disrupting compounds in effluent-dominated streams or by eating plants or animals in which they have bioaccumulated. Aquatic organisms may have a greater risk than humans because they are subject to a greater exposure. Although many of these compounds undergo natural attenuation in the environment, because they are being constantly discharged, organisms that are exposed to them experience a “pseudopersistence.”
Recent research has examined the effects of CECs and EDCs in particular on wildlife, both in the lab and in the field. For example, a causal relationship between exposure to human and synthetic hormones, plasticizers and detergent metabolites and the induction of an egg protein in male fish is shown in many species. Intersex fish found downstream of WWTPs have been linked to estrogenicity in wastewater discharges (Harries, J.E., et al, 1996).
Most significantly, in a seven-year study in the Experimental Lakes Area in northern Ontario, the population of fathead minnow, exposed to a low but constant constant concentration of the hormone found in birth control pills, ultimately collapsed (Kidd, K.A., et al, 2007). While these specific results cannot be immediately extrapolated to other species and watersheds, there is cause for concern.
The Spotlight on Water Utilities is Driven by Human Health Concerns
Potential human health effects due to exposure to CEC are harder to detect than effects on wildlife. Humans are exposed to pharmaceuticals and endocrine disrupting compounds through various routes. For example, water-soluble compounds such as most human pharmaceuticals can be consumed in drinking water, and fat-soluble compounds such as flame retardants or PCBs can be consumed by eating aquatic animals in which they have bioaccumulated. This first route is of concern to the drinking water industry.
Research is just beginning to address questions about effects of chronic low-level exposure, including possible synergism and other toxicological factors associated with these compounds. It is difficult to predict the effects of chronic exposures to extremely low concentrations of a contaminant; often, tests are done with higher concentrations, and the effects are extrapolated to lower concentrations using a dose-response curve. Because toxicological studies are not often conducted with human subjects, the effects of these compounds must be examined by extrapolating from other organisms, or by exposing human tissue cultures to the compounds being examined. Neither of these types of experiments provides conclusive evidence about the human health effects of exposure to part-per-trillion levels of pharmaceuticals in drinking water.
The class of constituents of greatest potential concern are the Endocrine Disrupting Compounds (EDCs) mentioned at the beginning of this article. The potential human health effects of EDCs are being studied by many groups, including the United States Environmental Protection Agency (EPA). The endpoints of exposure to pharmaceuticals and endocrine disrupting compounds in water that are being considered by researchers include endocrine system effects, neurological problems, reproductive and developmental abnormalities, and cancers.
Estrogen-mimicking compounds are under particular scrutiny due to possible effects at very low concentrations. They also pose a disproportionate threat to fetal development, and young children, since they interfere with normal developmental chemical signals in the body. Therefore, it is not just the level of exposure of EDCs that can be of concern, it is also the timing of the exposure in the development of humans and animals that is of concern.
Many researchers point out that the quantity of estrogens that may be consumed in reclaimed water is tiny compared to phytoestrogens and estrogenic hormones naturally present in the human diet. In fact, risk assessments that have been performed to date have not shown an unacceptable risk to humans (Snyder, S., 2007). However, at the present time, most researchers agree that there are many unknowns about possible synergistic effects, and of long-term chronic exposure to low levels of complex mixtures of these compounds.
Regulatory requirements for CECs are on the horizon
Regulations can control the input of CECs into the environmental and drinking water in two ways:
- By restricting which chemicals can be marketed and therefore make their way into the waste stream;
- By setting wastewater effluent and drinking water concentration limits for individual compounds, or bulk parameters such as estrogenicity.
So far, regulators have been more inclined to do the first of these, since toxic effects can more readily be shown in the parent product, rather than diluted in wastewater or drinking water.
European countries are further along than the United States in phasing out endocrine disruptors. Norway, for example, has banned the production, import, distribution, and most uses of nonylphenol and octylphenol ethoxylates. These are surfactants that have been shown to contribute significant estrogenicity to rivers downstream of industrial wastewater discharges. Additionally, the European Union requires the submission of Environmental Risk Assessments (ERAs) to gain market approval for new pharmaceuticals. These ERAs focus on the fate and effects of the compounds. In Canada, a similar requirement is under consideration.
The United States already has banned the use of some known endocrine disruptors, such as PCBs, DDT, and chlordane. However, these compounds were banned because of their carcinogenic effects rather than their estrogenic effects. In 1996, Congress passed new legislation requiring EPA to determine whether certain substances may have an effect in humans that is similar to an effect produced by a naturally occurring estrogen or other such endocrine effect. In response, EPA developed the Endocrine Disrupter Screening and Testing Advisory Committee (EDSTAC), whose members include representatives of academia, industry, public health interests, water providers, and various state and federal agencies.
In its 1998 final report, EDSTAC recommended a priority-based tiered screening system to evaluate chemicals for endocrine-disrupting effects. However, this program has received little funding, and the past ten years have seen little progress on the screening of suspected EDCs.
So far, neither the EPA nor regulators in other countries have released any guidance about the effects of relevant levels of most trace constituents in drinking water. Regulatory action at the Federal level in the United States has been delayed until more research is done because most existing data on listed man-made chemicals focuses on cancer risks, and CECs are generally present at too low a concentration to trigger concerns about carcinogenicity.
In response to the Associated Press article on pharmaceuticals in drinking water, a Senate Subcommittee on Transportation Safety, Infrastructure Security, and Water Quality hearing was held on “Pharmaceuticals in the Nation’s Water: Assessing Potential Risks and Actions to Address the Issue” (April 15, 2008). While not immediately resulting in regulatory action, this hearing demonstrates that the issue has caught the attention of United States senators, which may provide impetus for further regulatory developments.
State regulators in the United States are beginning to move ahead with adopting criteria, absent a Federal mandate to do so. Several states, such as Massachusetts and California, have adopted water quality criteria for perchlorate, a CEC that is found in rocket fuel and other explosives, that has been shown to interfere with fetal development at extremely low concentrations. Massachusetts intends to use the process they developed to regulate perchlorate to move ahead with examining possible limits for a list of 100 pharmaceuticals and personal care products.
Other agencies, while not yet ready to set drinking water limits for CECs, are beginning to require that they be monitored in anticipation of possible future requirements. For example, the California Department of Public Health (CDPH) recently updated their Groundwater Recharge Reuse Draft Regulations Criteria (August 2008) to include project-specific monitoring requirements for endocrine disruptors and pharmaceuticals, or for CEC indicator compounds or surrogates, in recycled water and groundwater recharge projects.
The link between CECs in wastewater and adverse ecological effects is stronger than for drinking water and human health, and therefore has attracted more attention for possible regulation at the Federal level. The EPA recently release a draft white paper concerning the development of criteria for CECs (USEPA, 2008). In this document, they acknowledge the difficulty of adopting criteria for constituents with non-traditional endpoints related to endocrine disruption, and begin to lay out a framework to address this.
Future regulatory action is likely as research progresses, and, once officially identified, industrial chemicals and personal care products that are strong endocrine disruptors probably will be phased out of use. In the meantime, wastewater treatment facilities could be regulated for their releases of suspected endocrine disruptors to the environment to protect aquatic habitats. Further down the road, it is likely that drinking water criteria will be developed for some CECs. Therefore, master planning studies for both water and wastewater facilities would be prudent to address the possibility of new endocrine disruptor regulations when making their 10- to 20-year long-term plans.
Scientific research and pilot testing are leading to CEC removal solutions
Both water and wastewater treatment can provide a barrier to prevent the introduction of CECs into drinking water. However, for the protection of aquatic life, the preferred barrier is removal during wastewater treatment. Although most WWTPs are not specifically designed to remove trace constituents, the majority of these compounds are removed at least partially during conventional wastewater treatment.
One of the most effective ways of increasing the removal of trace constituents during biological wastewater treatment is to increase the sludge retention time to at least15 days, or more. Under these conditions, (Salveson, A.T., et al, 2007)found that most pharmaceuticals, surfactants and plasticizers are removed to below the limit of detection. Concentrations of human estrogens are reduced by 90-100% with high sludge retention times. In fact, removal rates depend more on the sludge retention time than on the treatment technology, since trace constituents are removed equally in an activated sludge process as a membrane bioreactor. For treatment plants with excess capacity, sludge retention times can be increased by changing operating procedures without expanding biological treatment facilities.
Several advanced treatment technologies have been shown to be effective for removing trace constituents from wastewater. Filtration through granulated activated carbon (GAC), advanced oxidation and membrane treatment have all been studied to determine how well they remove trace constituents. Table 2 provides a summary of the removal efficiencies for CECs by different technologies.
An advanced oxidation technique that is being studied for removing trace constituents is the irradiation of filtered wastewater with ultraviolet light after hydrogen peroxide has been added. This process generates free hydroxyl radicals that react quickly and nonspecifically with organic constituents in wastewater. In a study by Rosenfeldt et al. (2004), two common hormones in wastewater were more than 95% removed from lab water with a concentration of 15 ppm hydrogen peroxide and either a low pressure or medium pressure UV lamp.
Ozonation is often put forth as a good technique for oxidizing trace contaminants in wastewater. Although ozone reacts preferentially with some compounds depending on their structure, it can also react with natural organic matter to for hydroxyl radicals and indirectly oxidize a greater number of constituents. Hormones are among the compounds that react well with ozone, as are most pharmaceuticals that have been tested. Ozone is effective at oxidizing some of the most frequently detected trace constituents, such as carbamazepine (an anti-epileptic drug), caffeine, cotinine (a nicotine metabolite) and atrazine (a pesticide).
Of the two advanced oxidation technologies that have been studied, both UV/peroxide and ozonation would be good treatment technologies for trace constituents. Both of these technologies also provide disinfection for the wastewater, and improve its aesthetic qualities. However, several analyses have shown that ozone can provide removal at a lower cost (Ternes, T., Joss, A. & Siegrist, H., 2007).
In general, trace constituent removal is poor during sand filtration. However, with chemical addition prior to sand filtration, Salveson et al. (2007) showed that the increased particle size can improve removal to 70 percent for some of the more hydrophobic compounds such as hormones. This can be an economical treatment strategy for WWTPs that already practice sand filtration.
In membrane filtration, water and wastewater are pushed through tiny pores at high pressures to reject particles that are not desired in the permeate. Microfiltration and nanofiltration have progressively decreasing pore sizes and require increasing pressure for operation, with reverse osmosis having the smallest pore size and the highest pressure.
Microfiltration rejects relatively fewer compounds than nanofiltration or reverse osmosis, since most trace constituents are smaller than membrane pore size, although some hydrophobic compounds are excluded through adsorption. Nanofiltration performs better than microfiltration with most compound since its pores are small enough to reject many compounds based on size, but it is more expensive. Reverse osmosis removes most compounds with a very high efficiency except for NDMA, which is small, polar and behaves like a water molecule. However, while reverse osmosis removes most constituents to below the limit of detection, its capital and operating costs are extremely high.
Source control is an attractive option to reduce the contribution of EDCs into the water cycle
Cash-strapped utilities may not have the means to implement advanced treatment to remove unregulated constituents from their wastewater or drinking water. Additionally, with recent focus on climate change and carbon footprints, the cost of advanced treatment can be counted in carbon dioxide emissions as well as dollars (Jones, O.A., et al, 2007). Therefore, source control is being looked at as an alternative for reducing the concentrations of CECs in the environment and in drinking water.
While the potential for CEC reduction in wastewater is much smaller for most compounds through source control than advanced treatment, it is an immediate step that can be taken by local governments and utilities that does not require facility upgrades or changes in operation procedures.
Source control can include the following measures:
- Pharmaceutical take-back programs to prevent the practice of flushing unneeded or expired pills. It is estimated that a maximum of 8 percent of pharmaceuticals are flushed down the toilet, and removing this source would lead to an approximately 9 percent reduction in surface water loading (Tischler, L., et al, 2007).
- Ecolabeling of household and personal care products to encourage consumers to choose products with non-persistent, non-toxic ingredients. There would need to be regulatory oversight to allow products to claim eco-friendliness on their labels.
- Reduction of over- and unnecessary medication. This has already been recommended to prevent the development of antibiotic resistant bacteria and could also help reduce concentrations of CECs
- Requiring ERAs for new pharmaceutical products, and phasing out persistent or toxic pharmaceuticals where there is another compound that could have the same effect.
So far, source control efforts have focused on pharmaceutical take-back programs. Several states have initiated such programs to great success, as measured by the quantity of unused drugs that are recovered. Although most drugs enter the water cycle via human excretion, these programs can remove a portion of the loading to WWTPs, and have additional benefits such as reducing accidental prescription drug poisoning and misuse.
Source control efforts require educational campaigns to inform and engage the public. Because the Southern Nevada Water Authority (SNWA) has led or been involved with much of the scientific work related to the low-level detection, treatment and health effects associated with pharmaceuticals and EDCs in drinking water supplies, the agency has been at the forefront of communication about this topic. JC Davis, the senior public information coordinator at SNWA, points out that, “by educating the public about the proper disposal of all types of chemicals--from household solvents and pesticides to unused pharmaceuticals--utilities are encouraging their customers to become stewards of both their water resources and the environment."
Source separation is another alternative that could be considered to reduce CECs in wastewater. The most feasible means of achieving this is to provide on-site advanced treatment to hospital wastewater, which is a significant point source of pharmaceutical discharges to WWTPs.
Looking ahead/moving forward
The public will continue to demand that the issue of CECs in the environment and in drinking water be addressed by their utilities, even in the absence of regulatory guidance. A coherent approach for treatment and control of CECs, as well as a communication strategy, is necessary to assure the public that the issue of pharmaceuticals in drinking water is being considered and addressed by their water purveyors and that aquatic life is being protected by wastewater dischargers.
Clearly, there is the need for more research, and funding for this research to elucidate the risk due to CECs. Shane Snyder, a scientist at the SNWA, who has contributed significantly to knowledge about the treatment and effects of CECs, has stated, “As a scientist, I recommend we focus on research related to health effects from trace pharmaceuticals wit ha lesser emphasis on occurrence, in order to determine whether there is in fact a problem to solve. The critical question we must address is not “Do they exist” but rather, “At what concentration are these compounds harmful to human health?” Only then can we make intelligent, rational decisions that protect he health of this country’s municipal water customers.”
CECs are an issue for both water and wastewater utilities. Members and member utilities should encourage cooperation between water and wastewater organizations, such as AWWA and WEF, to provide leadership and dialog for the development of standards and mutual policies to prevent and treat CECs in the water cycle.
- Associated_Press, 2006. Intersex Fish Are Found at High Rate in a Region New York Times.
- Harries, J.E., et al, 1996. A survey of estrogenic activity in United Kingdom inland waters. Environmental Toxicology And Chemistry, 15:11:1993.
- Jones, O.A., et al, 2007. Questioning the excessive use of advanced treatment to remove organic micropollutants from wastewater. Environ Sci Technol, 41:14:5085.
- Kidd, K.A., et al, 2007. Collapse of a fish population after exposure to a synthetic estrogen. PNAS, 104:21:8897.
- Kolpin, D.W., et al, 2002. Pharmaceuticals, hormones, and other organic wastewater contaminants in US streams, 1999-2000: A national reconnaissance. Environmental Science & Technology, 36:6:1202.
- Nash, J.P., et al, 2004. Long-term exposure to environmental concentrations of the pharmaceutical ethynylestradiol causes reproductive failure in fish. Environ Health Perspect, 112:17:1725.
- Rosenfeldt, E.J. & Linden, K.G., 2004. Degradation of Endocrine Disrupting Chemicals Bisphenol A, Ethinyl Estradiol, and Estradiol during UV Photolysis and Advanced Oxidation Processes. Environ. Sci. Technol., 38:20:5476.
- Salveson, A.T., et al, 2007. Innovative Treatment Technologies For Reclaimed Water - Ozone/Hydrogen Peroxide Pilot Test Report At DSRSD. 22nd Annual WaterReuse Symposium.
- Snyder, S., 2007. Relative Risks of Estrogens in Reuse Water. 22nd Annual WaterReuse Symposium.
- Snyder, S.A., et al, 2003. Pharmaceuticals, personal care products, and endocrine disruptors in water: Implications for the water industry. Environmental Engineering Science, 20:5:449.
- Ternes, T., Joss, A. & Siegrist, H., 2007. Contaminants of Emerging Concern - a Challenge for Urban Water Management. WEF Special Symposium on Compound of Emerging Concern.
- Tischler, L., et al, 2007. Potential Releases of Unused Medicines in Landfill Leachate. WEF Special Symposium for Sompounds of Eerging Concern.
- USEPA, 2008. Draft White Paper: Aquatic Life Criteria for Contaminants of Emerging Concern - Part I: General Challenges and Recommendations.
- Zuccato, E., et al, 2005. Cocaine in surface waters: a new evidence-based tool to monitor community drug abuse. Environ Health, 4:14.