OxyFile #352

 


Chlorine out, ozone in as water purifier

Los Angeles Herald Examiner
Tuesday, December 13, 1988

By Emilla Askari

Of all the deadly technologies developed during World War 1, none 
was more gruesome, none more cruel than poisonous chlorine gas.

One strong whiff and a soldier would start coughing blood.  The 
tortured hacking could go on for days, inevitably, the gas would 
kill -- hundreds of thousands of young men.

In farmhouses and hospitals throughout Europe, people watched.

And when the War To End All Wars was done, they gagged at the 
thought of disinfecting their drinking water with chlorine.

Not so across the Atlantic.  In America, hundreds of water systems 
began disinfecting their water with chlorine in the 1920s and 
'30s.

To this day, it is a commonplace chemical that we drink every day, 
rub from our eyes after staying too long in the pool and use to 
kill bugs in the water as a matter of course.  Soon, however, this 
will all change.

American technology has finally confirmed what the Europeans 
suspected all along: Adding chlorine to drinking water is not a 
healthy practice.

When chlorine combines with the byproducts of rotting leaves, a 
family of chemicals called trihalomethanes, or THMs, are formed.

THMs are carcinogenic.

One study by the President's Council on Environmental Quality 
found that people drinking chlorinated water had a 13 percent to 
93 percent greater chance of developing rectal cancer and a 53 
percent greater chance of getting colon cancer than people who 
drank untreated water.

For years, no one knew that people were getting small doses of 
THMs every time they brushed their teeth or made lemonade.

It wasn't until the mid-1970s that the Environmental Protection 
Agency's water quality lab in Cincinnati first isolated THMs in 
drinking water.

Before that, "We didn't worry about these cancer-causing chemicals 
because we didn't know they were there," said Pete Rogers, chief 
of the California Department of Health Services' drinking water 
branch.

"We didn't know how to measure them, and we didn't really know 
what the long-term effects (of drinking them) were."

All that is much clearer now.

At the current maximum contaminant level of 100 parts of THM per 
billion parts of water, the EPA estimates that one additional 
cancer will strike among 100,000 people who drink two liters of 
water a day for 70 years.

The EPA takes fewer risks with other drinking water contaminants.  
For example, its recommended level for the industrial solvent 
trichloroethene, or TCE, is five times stricter when measured by 
the number of projected cancer deaths.

The reason the EPA went easy on THMs: If the standard had been any 
tougher, water agencies wouldn't have been able to meet it unless 
they stopped chlorinating.

And there was no alternative.

Not in this country, not in 1979, when the standard was set.

As it was, the water industry balked at having to meet even the 
lenient 100 parts per billion standard for THMs.

The first reaction of the American Waterworks Association, an 
industry group, was to file a suit attempting to block the 
standard's implementation.

Too hard to meet, the association claimed, especially for agencies 
that get a lot of their water from rivers and streams, which are 
heavily laced with THMs' chemical "precursors."

Well water, in contrast, doesn't contain THM precursors; it never 
comes in contact with decaying leaves.

Eventually, the suit was settled when the EPA granted variances 
from the THM standard for some agencies that had a particularly 
hard time complying.

Next year, however, the EPA says it's really going to get tough.

It plans to lower the maximum allowable level of THMs to between 
50 and 10 parts per billion.

Again, water agencies are balking.  This time, however, they also 
are scrambling to find an other method of disinfecting water.

One possibility that has been used for years in Europe: ozone.

The gas, which smells like watermelons, disinfects as well as 
chlorine does.  It is more expensive.  Europeans pay much more for 
their water than Americans.  But, unlike chlorine, ozone 
disappears into the air within 24 hours, leaving behind no toxic 
residuals -- as far as researchers can tell so far.

"The fact of the matter is that our analysis of drinking water is 
incomplete," said William Glaze, a professor at UCLA's School of 
Public Health who specializes in water treatment.  "We're still 
finding things we didn't know were there."

For more than a year, Glaze has been focusing his microscope on 
water samples from the city of Los Angeles' new filtration plant 
in Sylmar.

The 2-year-old, $106 million plant is one of the largest in the 
world that disinfects with ozone.

So far, Glaze says he has found nothing alarming in the product of 
the plant he calls "one of the best in the world."

There, where the Los Angeles Aqueduct dumps its relatively pure 
load of runoff from the Owens Valley, man-made lighting bolts pass 
through thousands of glass tubes in the plant's huge ozone 
generators.  Inside the tubes, the electricity converts liquid 
oxygen into ozone.

The gas is then piped over to holding tanks the size of small 
auditoriums.  The tanks are filled with water and the ozone is 
allowed to percolate through it.  A thick porthole allows visitors 
to peek inside the cement tanks and watch the ozone bubble away 
like champagne.

From Egypt, Japan and Monroe, Mich., water managers have come to 
observe.

Some visitors also have come across town, from the mighty 
Metropolitan Water District of Southern California.

MWD, the state's largest water wholesaler, already has converted 
its treatment plants from chlorine to chloramine, a combination of 
chlorine and ammonia that's less likely to combine with the THM 
precursors.

But MWD gets all of its water from rivers: the Colorado to the 
east and the Sacramento to the north.  These sources are high in 
decomposing leaves, and thus in THM precursors.

When the new EPA standards come out, MWD is going to have to do 
even more to reduce THMs.

The agency -- which supplies half the water used by coastal 
Southern California -- is studying the possibility of converting 
all five of its treatment plants to a combination of ozone and 
peroxide.  The estimate cost: $150 million.

At that price, MWD is fervently hoping that future research 
doesn't uncover any ozone byproducts as unhealthy as chlorine's.

"If there are problems with ozone," said MWD water quality 
director Michael McGuire, "we're in a hell of a mess."