Nah, but at least its not a by-product from atomic bombs ......... I
learned that at sci.med.dentistry!
Posted on Tue, Sep. 23, 2003
Towns trickle away from chlorine use
Instead, ozone is bubbled through the water to rid it of bad tastes
and bacteria.
By Tom Avril
Inquirer Staff Writer
When the rains of Hurricane Isabel washed pollution into rivers last
week, older water-treatment plants had to add more chlorine to make
the water safe to drink.
In a glass-walled room in South Jersey - the high-tech nerve center of
a treatment plant that serves one million customers - a different
technique was under way Thursday night.
With several computer keystrokes, a technician added a few extra
pounds of a colorless gas, ozone, to the water before it was pumped to
local homes.
Better known for its role in the upper atmosphere, where it shields
the Earth from the sun's rays, ozone is gaining popularity in the
world of water treatment. It is one of several alternatives to the
century-old use of chlorine, under scrutiny for its apparent unhealthy
side effects.
Plus, there's the issue of that swimming-pool taste.
"Before this plant, everyone in South Jersey drank well water," said
Arthur Shearman Jr., manager of the New Jersey American Water plant,
in Delran. "We wanted to provide them with a [low-chlorine]
alternative that they wouldn't notice was different."
Ozone also is used at plants in Chalfont, Bucks County, and Altoona,
Pa. Another new option is to treat water with ultraviolet light, a
method patented by Pittsburgh-based Calgon Carbon Corp.
Why the move away from chlorine, a chemical workhorse that has
effectively disinfected U.S. water supplies since it was introduced in
Jersey City, in 1908?
Before chlorine was used, thousands of Americans died each year from
typhoid fever and cholera, often in outbreaks caused by rain and
floods. In Philadelphia in 1906, six years before the city began
adding chlorine to the water, 1,063 people died of typhoid.
Yet drawbacks to chlorination have surfaced in recent years.
Chlorine reacts with organic matter from rivers and streams to form
several byproducts, among them a class of chemicals called
trihalomethanes.
With evidence indicating that these chemicals caused bladder cancer,
the U.S. Environmental Protection Agency began to regulate them in
1979.
More recently, researchers have concluded that the trihalomethanes
themselves are not at fault, but perhaps some other chemical culprit
that is associated with them - that is, present in drinking water at
the same time.
Meanwhile, other researchers suspect that high levels of chlorine
byproducts can lead to miscarriages.
The various findings and EPA regulations have spawned a great deal of
experimentation.
Yet some water officials are anxious about replacing an old standby -
especially with research showing that some of the replacements,
including ozone, can have their own side effects.
"You know that chlorine has been effective for 100 years," said Dave
Katz, deputy commissioner for the Philadelphia Water Department, which
still uses chlorine. "Before you ever go away from it, you have to be
damned sure you know what you're doing."
The Delran plant opened in 1996, the result of a state requirement
that South Jersey customers use less water from dwindling underground
supplies, specifically the Potomac-Raritan-Magothy aquifer.
In some areas, demand on the aquifer caused it to turn brackish.
The Delran plant draws water instead from the Delaware River,
supplying dozens of communities in Burlington, Camden and Gloucester
Counties with 40 percent of their water - an average of 20 million
gallons per day.
The plant makes its own ozone on site, converting liquid oxygen (O2)
to ozone (O3) by using 3,500 volts of direct current. Chemically, it's
the same substance as that in smog, but it is not harmful in drinking
water.
The gas is then bubbled through the water, wiping out odor, bad taste,
and bacteria, as well as tough cysts such as cryptosporidium and
giardia. All without the byproducts of chlorination.
So why isn't everyone using it?
It's more expensive than chlorine, for one thing. And ozonation has
its own byproducts that are thought to be harmful, said David Reckhow,
professor of civil and environmental engineering at the University of
Massachusetts, Amherst campus.
Those byproducts are called bromates, which can be formed if the water
contains bromide salts.
Officials at New Jersey American say bromates are not a problem for
them because the Delaware River does not contain significant levels of
bromides. Yet they concede that there is no one way of water
treatment.
"All of them have their issues," said Mark W. LeChevallier, research
director at American Water, an affiliated company. "There's no kind of
idiot-proof answer."
In the meantime, it is unlikely that chlorine will go away anytime
soon as a means of water treatment.
Virtually all water-treatment plants, including the New Jersey
American facility, must still add at least a small amount of chlorine
to the water just before it is sent off to customers.
Without a residual level of chlorine in the distribution pipes,
bacteria would prosper, said Peter Lusardi, an engineer with CET
Engineering in Harrisburg.
Water-treatment plants in Philadelphia and many other places have
mixed ammonia with this post-treatment chlorine, a step that results
in lower trihalomethanes, said Mark Johnson, a chief official with the
water supply management program in the Pennsylvania Department of
Environmental Protection.
But even that step can have its drawbacks, leading to the formation of
still another group of harmful chemicals, nitrosamines.
Bottom line, said Reckhow: In the centuries-old field of
drinking-water treatment, there are still more questions than answers.
"Before you jump into something," Reckhow said, "you've got to fully
investigate it to make sure it's not worse than what you're jumping
from."
--------------------------------------------------------------------------------
Contact staff writer Tom Avril at 215-854-2430 or
[email hidden].
--
Joel M. Eichen, .
Philadelphia PA
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