Denver converts sewer water
to drinking water
By NORM UDEVITZ
The Denver Post
DENVER Scientists laboring in a
high-tech plant on the banks of the South
Platte River in north Denver say they are
near to developing a system to recycle
sewage into clean, pure drinking water.
That long-sought goal daily transfor-
mation of 100 million gallons of waste wa-
ter into tap water is "in sight," says Bill
Lauer, 39, a chemist and manager of the
little-known project. "It appears possible
now that reused water could constitute
about 15 percent of Denver's tap require-
ments by 2000."
He and other officials say that they are
encouraged by the water purified at the
Denver Water Board plant a maze of
multi-color tanks, pipes, valves, switches,
dials and computers that looks like the en-
gine compartment of a Star Trek space
There are only three other such recy-
cling plants in the world, and none is as
advanced as the Denver facility. Lauer
said. Two plants are in California and Vir-
ginia. The third is in South Africa. All pro-
.duce small amounts of potable water from
But Denver's plant already produces 1
million gallons a day of water that "satis-
fies all existing and proposed federal and
Denver's recycling plant already produces I million gallons a
day of water that "satisfies all existing and proposed federal and
state drinking water standards. Additionally, the reclaimed
water compares favorably with Denver's existing high quality
drinking water supply," said Bill Lauer, project manager.
state drinking water standards. Addition-
ally, the reclaimed water compares favor-
ably with Denver's existing high quality
drinking water supply." he said.
"It isn't quite ready to drink yet," he
added, noting: "There were some ammo-
nia-nitrogen concentration problems, but
we are solving that with a ... process that
removes the ammonia. That's important
because ammonia can convert to nitrite or
nitrate, which can be harmful to humans.
And the costs are still quite high."
The treatment costs have been about
$2.50 for each 1.000 gallons produced.
That compares with the department's cur-
rent cost of 30 cents to treat a similar
amount of fresh water.
Lauer said that in the next two years
project scientists will seek ways to sub-
stantiall. lower the treatment cost, pri-
marily by altering or eliminating
redundant steps in the recycling process.
"By 2i00 and beyond." Lauer said. "We
expect the cost to compare favorably with
the cost of treating any of Denver's other
water supplies. The cost of all water will
be somewhat higher by then, of course,
because acquisition and development
costs will continue to escalate."
By the end of 1988, if all goes well,
Lauer's 20-man team also will start a two-
year program of testing the treated water
on animals The health-effects tests on ani-
mals will be necessary to "cover the areas
that can't be done by chemical analysis,"
"That part of the process, will be much
like developing new drugs or medicines.
except that it', never been done with wa-
ter before." he said. "We have to establish
a lot of new methods concerning controls.
checks and balances and the kinds of con-
centrations of treated water we will use on
Lauer. assistant supervisor of the de-
partment's regular treatment program un-
til 1980, thinks he may be able to
recommend the agency build a full-scale
commercial water reuse plant by 1991.
"After that, it would be up to the water
board," he said. "But it appears quite pos-
sible now that such a plant could be oper-
ating by 2000."
Few water experts in the region doubt
that Denver will need the added treatment
capacity by then. Studies now indicate the
number of households served by the water
board could nearly double by 2000 from
about 245,000 now to more than 435,000.
But the department's water capture.
storage and treatment capacity may not
keep pace. particularly if there are delays
in the planned Two Forks Dam and Wil-
liams Fork projects.
That might mean existing or only slight-
ly expanded supplies might have to be
stretched more. Reuse, particular a sys-
tem that could recycle enough water to
serve the daily needs of about 125.000
house holds about 375.000 people -
could become vital.
It is under that kind of pressure that
scientists at Denver's $30 million re-use
project have worked.
The experiments spurred primarily
by arid Denver's constant quest for water
- actually began in 1968. In 1970, a
small pilot plant was built. In 1979,
scientists, bolstered by a $23 million
commitment from the water board
and a $7 million grant from the Envi-
ronmental Protection Agency, began
designing and building the full-scale
demonstration plant near the Metro-
politan Wastewater Treatment Plant
where sewage-laced water has long
been cleaned to secondary standards
for return to the South Platte.
SThe space-age reuse plant began
full-scale operations on Oct. 1. 1985,
Employing technical processes devel-
oped earlier: lime clarification and
recarbonation. sand and coal filtra-
tion, ion exchange, carbon adsorp-
tion, ozone disinfection and reverse
The processes sound formidable
The water, which comes from the
metro waste water treatment plant
and eventually is returned there, ar-
rives already treated to a secondary
standard That means it is clean
enough to return it to the river, but it's
far from being ready for humans to
Lime clarification settles out most
heavy suspended organic particles.
including many man-made pesti-
cides, along with minerals, viruses