Environmental Science & Technology Online News

August 4, 2005


QUOTABLE: "Researchers are finding these contaminants at levels so low
that they might not even be harmful. 'The precautionary principle
would say that if you can remove these substances in a reasonable
manner, then that is probably a good thing.'"

By Paul D. Thacker

Forget well-known toxics such as pesticides and industrial chemicals:
Scientists are now focusing their energies on common household
chemicals and medicines that are not regulated by the U.S. EPA1 but
still come trickling out of your kitchen tap. Americans consume
thousands of pharmaceuticals and produce tons of chemicals to maintain
their modern lifestyles, and new findings published today on ES&T's
Research ASAP website (es04847992) reveal that technologies to
remove these products from drinking water have different levels of

Ozone disappears within seconds after disinfecting water."I think the
general overall pattern we are seeing is that ozone is better at
removal of these compounds," says Shane Snyder, a project manager with
the Southern Nevada Water Authority and one of the authors of the
study. The research evaluated several water treatments commonly used
in the U.S., including chlorination, ozonation, and ultraviolet (UV)

When researchers compared the effectiveness of ozone and chlorine in
removing 31 chemicals from drinking water, they found that ozone
successfully eliminated far more chemicals at much higher percentages.
Of the 31, 26 were reduced to at least 30% of their original
concentration by ozonation. These substances included testosterone,
estrogen, naproxen, caffeine, and the mosquito repellent DEET. Only
two chemicals seemed resistant to ozonation: the fragrance compound
musk ketone and the flame retardant tri(2-chloroethyl) phosphate

For chlorine, 15 of the chemicals remained at levels exceeding 70% of
their original concentration. Like ozone, chlorine was ineffective at
eliminating significant amounts of TCEP, but caffeine, progesterone,
and the anticonvulsant drug carbamazine also resisted degradation.
Snyder adds, "I don't think it's been recorded before, but chlorine
was not effective at removing testosterone."


Changes driven by cryptosporidium

The U.S. EPA began adding a series of new drinking-water rules --
known collectively as the Surface Water Treatment Rules -- after the
1993 outbreak of cryptosporidium in Milwaukee, Wis. According to the
Centers for Disease Control and Prevention,3 more than 403,000
residents were sickened, and the outbreak caused by this protozoan
cost Milwaukee $96.2 million. From 1990 to 2000, the U.S. faced nine
other outbreaks of cryptosporidium illnesses from contaminated water.

Cryptosporidium is a hardy protozoan that contaminates the water
supply through fecal contamination by humans, livestock, or wildlife.
Ingestion of the parasite causes diarrhea and may lead to death,
especially in immunocompromised people, such as HIV patients.

In 1994, 32 people died in Las Vegas, Nev., from cryptosporidium.4
"It was never conclusively linked to the drinking water," says Snyder,
"but the public relations problems caused us to move to ozone." He
says that the destruction of hormones, personal care products, and
other chemicals in the process is an added benefit. -- PDT


"Ozone has been around to help with taste and odor for some time,"
says Craig Adams, a professor of environmental engineering at the
University of Missouri-Rolla. "Ozone is also used for color removal if
you have colored water. It's really a holistic sort of treatment, and
it works better for some of these chemicals such as endocrine

Snyder has also compared ozone with UV treatment5 and found that the
latter shows little effectiveness at destroying these chemicals. "At
the dose used in most plants for disinfection, there is essentially no
removal of these types of compounds," says Snyder. "That's a real
disappointment because UV is actually a more modern type of

But ozonation does have some drawbacks. Snyder points out that, like
chlorination, ozone generates byproducts that can be harmful. For
instance, ozone can generate bromate in water with high bromide
levels. UV technology does not create these problems because most
organics are not very photoreactive.

Alan Roberson, the director of regulatory affairs with the American
Water Works Association, says that many cities designing new drinking-
water facilities are gravitating toward either UV or ozone because of
EPA regulations aimed at controlling cryptosporidium. "Generally,
you're seeing the middle to large cities moving in this direction
because they have the financial resources and the skilled operators to
run these plants," he says. He estimates that a switch to UV or ozone
treatment might add about 10% to typical water treatment costs.

Snyder agrees that the switch to UV and ozone has been spurred by
EPA's Surface Water Treatment Rule,6 a response to outbreaks of
cryptosporidium that hit the U.S. in the 1990s (see sidebar).
Chlorination is not very effective at removing the protozoan, but
ozone works by directly attacking the pathogenic cells, whereas UV
scrambles the DNA inside.

Adams says that research into which treatment proves more effective at
destroying organic chemicals in the water is simply an added benefit
for modern water treatment. Researchers are finding these contaminants
at levels so low that they might not even be harmful. "The
precautionary principle would say that if you can remove these
substances in a reasonable manner, then that is probably a good

Copyright 2005 American Chemical Society