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Towns Trickle Away from Chlorine Use

Instead, Ozone is Bubbled Through the Water to Rid it of Bad Tastes and Bacteria 

TOM AVRIL / Philadelphia Inquirer 23sep03

[More to read below]

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 [see below], 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."

source: http://www.philly.com/mld/inquirer/news/front/6836322.htm 23sep03

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