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Phoenix fighting odor from algae
Judy Nichols
The Arizona Republic Jun. 22, 2004
Phoenix has spent $370,000
in extra water treatment because of algae blooms that have killed thousands
of fish in the Salt River water system.
The treatment, powder activated carbon, is mostly to control odor and is in
addition to the usual filtration and chlorination.
Officials assure residents that the water is safe to drink, said Annie
DeChance, public information specialist for the Phoenix Water Services
Department.
The water treated by Phoenix
is also distributed to Mesa through the Val Vista Water Treatment Plant,
jointly owned by Phoenix and Mesa.
Scottsdale pays Phoenix to treat some of its water.
Some other cities have chosen not to treat with additional carbon.
Thousands of fish have died in the Saguaro, Canyon and Apache lakes, and
officials have attributed the deaths to toxins from algae blooms in still
and slow-moving water.
The blooms of Cylindrospermopsis raciborskii were fed by ash runoff from the
"Rodeo-Chediski" fire of June 2002 and record heat this May.
Drought cited as factor
"We think it's in part due to the drought, with less new
water coming in, so the lake's not as cold," said Gregg Elliott,
environmental scientist for Salt River Project.
The toxins from the algae are short-lived and would dissipate quickly in
running water. None of the algae or their toxins has been detected in water
delivered to Phoenix.
But the city has chosen to treat the water with carbon as a precaution,
DeChance said.
Adding carbon helps with odor control and absorbs organic particles.
The same treatment is used regularly in late summer because of different
types of algae that grow in the canals.
The city began adding the carbon about a month earlier than usual, she said.
The additional expenses are paid through a contingency fund and should not
affect water rates.
SRP, which operates the dams along the Salt River, does not treat the water
with any chemicals.
"We convey raw water, including river and ground water," Elliott said. "We
don't do any drinking-water treatment. That's all done by the individual
cities."
No health concerns
Elliott said the dead fish in the lakes do not pose a health
hazard in treated drinking water.
"The anglers don't like it having a bunch of dead fish around, and you may
not want to water-ski in it," he said. "But it's not a problem for the
drinking water because there's just not that many fish in a large volume of
water."
Officials continue to monitor the water for increased organic particles and
for bacteria but have not found any.
"Any bacteria is normally removed through chlorination at the treatment
plant," Elliott said.
Elliott said officials from the U.S. Fish and Wildlife Service expect the
algae to continue blooming throughout the summer and to cause intermittent
fish die-offs.
"There is no clear way to predict when and where, though," he said.
Once the algae appear, they are likely to return the following summer after
becoming dormant over the winter.
"It's dormant in the colder, darker weather, then grows again when it warms
up," Elliott said.
Water from the Central Arizona Project is not affected.
Scottsdale's new
water treatment plant is being built at McDonald Drive
and Hayden Road.
That plant, scheduled for completion by early 2006, will have a full-time
carbon system and use membranes to filter the water, said Jim Clune, water
quality treatment director.
Nearby cities unfazed
Other
cities have not followed Phoenix's
lead.
Tom Gallier, Tempe's Water Utilities Department manager, said Tempe has not instituted
additional treatment because it has not detected any effect from the blooms.
Officials in Glendale
reached the same conclusion.
Rick Scott, superintendent for plant operations, said Glendale officials are
pretreating the water with chlorine but didn't think they needed to use
carbon.
And Lee Hecht, water quality laboratory supervisor, pointed out that in two
years, Glendale will have two new water treatment facilities that will use
granular carbon and eliminate the need for the powder. |
