WASHINGTON — The Environmental Working Group (EWG), an environmental advocacy group headquartered here, is recommending in its newly released report that the 1.1 million consumers of tap water treated by the Washington (DC) Aqueduct at least temporarily treat their water with point-of-use or point-of-entry systems to lower disinfection by-product (DBP) levels.

According to the executive summary of the report, released July 19, “Tap water tests from May 2007 revealed toxic by-products of the chemicals used to purify Potomac River water, at levels above annual federal health limits.”

The water samples were collected from 18 locations across the District of Columbia, including the US Capitol, US Environmental Protection Agency headquarters, parks, schools, and residences of pregnant women and other groups susceptible to health problems from exposures to DBPs.

The samples were tested by “an accredited lab” for two types of DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs), according to the 19-page EWG report.

Almost 90 percent of the samples had THMs at levels associated in epidemiological studies with low birth weight and serious birth defects in infants.

More than 40 percent of the tap water samples contained chemical by-products of water treatment above annual federal health limits. HAAs were found at their highest levels since 2001, the last year before the Washington Aqueduct modified its treatment techniques to reduce levels of THMs, which are related by-products of chlorination, the EWG reported.

Washington Aqueduct General Manager Thomas P. Jacobus said in a July 19 article in The Washington Post that the study results are what he would have expected.

Jacobus said in The Washington Post article that the higher DBP levels were probably temporary because the water samples were taken at the end of a month-long chlorine burn, which was conducted to remove sludge and sediment from pipes.

The Washington Aqueduct regularly uses chloramines to disinfect its source water. The DC Water and Sewer Authority delivers the water to consumers.

The EWG study made several recommendations for all 1 million-plus consumers of Washington Aqueduct tap water who live in Washington, DC, and northern Virginia, until the DBPs’ levels are consistently lower in the treated tap water.

The EWG recommended consumers consider using an activated carbon filter in a faucet-mounted device or in a larger under-counter system.

The EWG also recommended consumers “consider purchasing a whole-house filtration system to further reduce DBP exposure.”

The EWG recommended several policy changes, including:

EWG Executive Director Richard Wiles said in The Washington Post article that his organization recommends the US Army Corps of Engineers, which operates the Aqueduct, use carbon filtration to remove chlorine by-products and put in place a program to educate consumers about the health risks of chlorine and chloramine by-products.

In response to residents’ complaints in early July of objectionable taste and odor in their drinking water, Jacobus said carbon would be used.

For related information on this story, click here.

For more of the latest news, click here.

To subscribe to Water Technology® magazine, click here.

To discuss this topic with other water and wastewater industry professionals, click here.