Of 11 pharmaceuticals commonly found in sewage, University of Hawaii graduate student Jeffrey Murl has recently determined that seven of them have the potential to leach into Oahu’s groundwater, one poses an uncertain risk, and the remaining three — which are perhaps the most likely to impact humans and animals at low doses — are unlikely to leach into Oahu aquifers.
Whether or not those “micro-pollutants” pose a threat to human health remains to be seen. Using his research, as well as recent studies conducted by other scientists with the university’s Water Resources Research Center, the state Department of Health is planning to revise its guidelines on wastewater reuse to ensure that any health effects are minimized or avoided altogether.
Murl’s findings are part of an effort by the Health Department to determine how and where recycled wastewater should be used, given that it is likely laden with contaminants of emerging concern.
These contaminants are ubiquitous and include everyday products such as detergents, cosmetics, antimicrobials, insect repellant and drugs. As they’ve only been detectable since the early 2000s, no federal regulatory standards exist regarding their release into the environment.
Even so, studies have shown they pose a risk to ecological health. Impacts to humans — from the contaminants and their metabolites, alone or in combination with others — is poorly understood, although several studies suggest levels in effluent are perhaps too low to have any effect.
What is known is that current wastewater treatment processes do a poor job of removing the contaminants.
Although government regulatory agencies rarely test for them in wastewater, drinking water, or in the environment, studies done by the U.S Geological Survey have shown that they are commonly found in streams near wastewater treatment plants and in drinking water.
Nearly 40 years ago, the Water Resources Research Center first assessed the potential for drinking water contamination as a result of irrigating crops with treated wastewater. Testing then for things such as nitrates and viruses on experimental plots of sugarcane in Central Oahu, researchers concluded that pollutants in effluent were unlikely to find their way into the aquifers below.
Murl’s research, however, suggests that may not be the case with respect to the contaminants of emerging concern.
Although Murl says contaminant levels found so far in effluent are so low they probably wouldn’t even be considered trace contaminants, he cautioned, “We need to keep monitoring these compounds. They have poorly understood impacts, but are frequently detected.”
Treated wastewater has been used for irrigation in Hawaii for nearly a century. According to a 2013 water reuse plan developed for the state Commission on Water Resource Management, recycled water was used on sugarcane fields in Waialua, Oahu, as early as 1928.
And in the 1960s and ’70s, the Pioneer Mill Company on Maui blended chlorinated effluent from the Kaanapali sewage treatment plant with groundwater to irrigate 400 acres of sugarcane fields. By the late 1970s, about 10 million gallons of effluent a day from nearly 20 wastewater treatment plants were being used to irrigate golf courses, crops, and lawns across the state. By the early 2000s, the use of wastewater for irrigation had more than doubled to 23 million gallons per day. By 2011, it had reached than 30 million.
As state and county agencies seek to protect potable water supplies, the use of recycled wastewater will probably continue to grow. On Oahu, in particular, an ordinance instructs the Honolulu Department of Water Supply to require large, landscaped areas such as golf courses, parks, schools, cemeteries and highways be irrigated with non-potable water if it’s available.
What’s more, the Commission on Water Resource Management’s 2014 Central Oahu Non-Potable Water Master Plan identifies treated effluent as the main non-potable water source for state agricultural lands purchased from the former Galbraith Estate and for lands surrounding Kunia Road.
Together, those areas are expected to need nearly 20 million gallons per day of non-potable water.
The plan acknowledges concerns surrounding impacts of recycled water use above aquifers used for drinking water, and notes that the Heath Department, WRRC, the Agriculture Department and the U.S. Geological Survey and the Honolulu Board of Water Supply had all initiated studies — including Murl’s — to assess “the safety and efficacy” of irrigation with treated wastewater, giving particular attention to contaminants of emerging concern.
“Anywhere we’re searching for these compounds, we’re finding them around the world,” Murl said last month during a Water Resources Research Center talk on his research. Referring to results from a recent USGS-BWS study, where the agencies tested for 62 contaminants in Wahiawa Wastewater Treatment Plant effluent, Kaukonahua Stream (which receives the effluent via Lake Wilson), and waters in Haleiwa, he said, “they looked for 62 (contaminants of emergency concern) and found 62.”
What’s more, he noted that in the effluent and the stream, one of the contaminants found — the antibiotic sulfamethoxazole — exceeded the level at which environmental effects have been found.
Although the Health Department has never tested drinking water for these contaminants, Murl said he thinks they’re probably there given the results of studies across the globe. Robert Whittier of the Safe Drinking Water Branch notes that, in Hawaii, recycled water is applied mostly downgradient from drinking water wells and the further the effluent has to percolate to an aquifer and the longer it takes, the lower the resulting contaminant concentrations.
The total number of contaminants of emerging concern worldwide may exceed 10,000, Murl said, but current technologies can detect just 600 of them. That makes testing for their presence far too expensive to be undertaken regularly by government agencies, Whittier said.
“When the USGS did a study in North-Central Oahu for (contaminants of emerging concern) and other wastewater indicators, the cost per sample set was in the thousands of dollars.”
To narrow the field, Murl chose the 11 drugs that are most frequently detected in effluent and are also likely to have the greatest environmental impact.
“The most damaging is estrogen, which can work in concentrations as low as 1 nanogram per liter,” he said, citing cases where male fish exposed to estrogen in the environment have been found with eggs growing in their gonads. Estrogens are used in hormone therapy and birth control pills; Murl chose to assess three of them.
Given growing concerns worldwide about the development of antibiotic-resistant bacteria due to rampant antibiotic use, Murl also assessed six commonly prescribed antibiotics.
These “nightmare bacteria” can kill half of the people infected with them, he said, adding, “If (antibiotics) leach or are applied directly into the water … we’re throwing the dice on the next pandemic possibility.”
Murl also assessed Carbamazepine, an epilepsy medication that studies have found to be detrimental to mussels and block reproduction of non-biting midges.
Finally, Murl assessed Propranolol, a beta blocker used to treat high blood pressure and which has been found to lower egg production of some species of fish.
Using a modified model that was originally devised by the university’s Department of Civil and Environmental Engineering to assess the likelihood of pesticides to leach through soils, Murl assessed the leaching potential of Carbamazepine, Propranolol, sulfamethoxazole, Azithromycin, Clarithromycin, Roxythromycin, Ciprofloxacin, Ofloxacin, and the three estrogens (Estrone, Estradiol, and Ethinylestradiol).
He found that Carbamazepine, Clarithromycin, Ciprofloxacin, and Propranolol were all likely to leach throughout Oahu (except for conservation areas where no wastewater was expected). Ofloxacin, Roxythromycin, and Azithromycin were likely to leach through all but the southwest corner of the island. As for sulfamethoxazole, the model found that it would likely leach in a few scattered areas, but it was uncertain whether it would leach elsewhere.
While none of the estrogens were likely to leach, Murl stated that direct effluent discharge to water bodies such as Lake Wilson pose a “high risk for environmental impacts.”
Given his seemingly dire results, one audience member at his recent talk asked whether they mean that wastewater shouldn’t be reused on the island.
“I actually think recycling wastewater is great,” Murl replied. “The model is just kind of a first-order swipe. It’s not a definitive, ‘this will happen; this won’t happen.’”
Whittier suggested that Murl’s results, validated with actual monitoring data, will help the department better assess what’s in the aquifers.
“We don’t have the budget to sample for 62 (contaminants of emerging concern). We might have the budget to sample for five. We can take this large data set … and reduce it down to something manageable,” he said.
Given Murl’s results, Whittier said, “maybe we’re applying the recycled water in the wrong spot. Maybe we should do it upslope rather than on the coast.”
Keeping wastewater reuse upslope increases the soil’s ability to filter out contaminants and gives them more time to degrade and a greater a chance to be diluted with groundwater before they’re discharged into the coastal zone, he stated in an email.
Even though the Health Department’s treated wastewater use guidelines were revised recently, Whittier said they aren’t very restrictive and the department will continue to update them. At some point, they will include testing requirements, he said.
As the state moves toward more widespread use of recycled water in upslope areas, the Health Department intends to periodically sample recycled water as well as water in soils to determine where selected contaminants go and what happens to them, he added, noting, “This will be likely be a collaborative partnership between DOH, the recycled water providers and users, and the University of Hawaii.”
In addition to the DOH’s monitoring efforts, Michael Cooney, Marek Kirs, and Roger Babcock of the University of Hawaii are investigating wastewater treatment options that could cheaply and significantly reduce contaminant levels in effluent.
“Results from our work are expected to show that application of low-energy, low-chemical, anaerobic-aerobic biofilm reactors linked to downstream unit operations employing disinfection (i.e., UV irradiation) and advanced oxidation processes (i.e., UV plus H2O2) can cost-effectively produce reuse water devoid of these emerging pollutants,” they state in an abstract of their study.
Their project is expected to conclude in February of next year.
Reprinted with permission from the current issue of Environment Hawaii, a non-profit news publication. The entire issue, as well as more than 20 years of past issues, is available free to Environment Hawaii subscribers at www.environment-hawaii.org. Non-subscribers must pay $10 for a two-day pass.