Science News - December 8, 2004

Pollutants in New Jersey’s drinking water

In the largest screen of organic chemicals in finished drinking water to date, U.S. Geological Survey (USGS) scientists found that a surprising number of the chemicals that enter a drinking-water plant serving metropolitan New York also end up in people’s homes. Of the more than 100 chemicals screened—including pharmaceuticals, antibiotics, and household chemicals—22 were found in the finished water. Only one of these compounds, the cleaning solvent tetrachloroethene (TCE), is regulated. Parts of this research are being presented at national groundwater meetings, and a study will be published later this year.

All the chemicals found in the finished water were at very low levels that do not appear to be harmful, says research hydrologist Paul Stackelberg with USGS. For instance, the average concentration of TCE in the drinking water was 0.03 micrograms per liter or .03 ppb. The EPA limit is 5 ppb.

However, Stackelberg warns that even a screen on this scale represents a fraction of the chemicals that are in the environment and is missing any transformed products. He also notes that while these compounds were found at extremely low levels, they may have synergistic effects that increase their impact on human health.

By testing at different points in one treatment plant, Stackelberg found that most of the chemicals were probably adsorbed to solids and later removed during sedimentation and filtration. Other compounds were undetectable after treatment with chlorine, although transformed products probably remained.

Some of the chemicals showed marked resilience. Levels of the insect repellent DEET (N,N-diethyl-m-toluamide) in the raw water were about 0.13 ppb, while the finished water had levels at 0.08 ppb. The endocrine disrupter bisphenol A entered the plant at 0.1 ppb and left at 0.02 ppb.

“I think the big question is not what remains in the drinking water, but what happens to these parent compounds,” says Ed Furlong, a research chemist with USGS. For example, a recent paper found that the antibiotic sulfamethoxazole becomes chlorinated during water treatment (Environ. Sci. Technol., 2004, 38, 5607–5615).

“Chlorine and ozone love to react with certain compounds, especially anything with a benzene ring or a double bond,” says Susan Richardson, a research chemist with EPA in Athens, Ga. “This is an area with a lot of room for research.”

The drinking water in this city usually resides in the pipes for 8–10 days before it is used. Stackelberg simulated this process by storing finished water in jars with sodium hypochlorite and then testing it over multiple days to see whether residual pollutants degraded in the presence of the disinfectant. Some chemicals, such as tylosin and diazinon, degraded over time, but the antiepileptic drug carbamazepine, found at about 0.03 ppb in finished water, showed little reactivity.

Of the 58,000 community water plants in the United States, about 8500 serve large metropolitan areas, like the one Stackelberg studied, says Alan Roberson, director of regulatory affairs for the American Water Works Association. Roberson says that the levels of most organic chemicals in the water can be reduced even further by adding a carbon filtration step in the final filtration process. “Around 80% of the drinking-water facilities in the Midwest have a carbon filtration step to remove pesticides, such as Atrazine,” he says. However, facilities in metropolitan New York do not use this step.

Furlong says that a current study is looking at pollutants in a drinking water plant that uses ozonation. “I think the next big step is to see what happens inside a plant to these parent compounds,” he says. —PAUL D. THACKER