that several drought-plagued Texas cities are planning to turn treated
wastewater into drinking water has got Texans talking. And the conversation may
not be exactly what you might expect.
Rather than wringing their hands over the
“yuck factor” and “toilet-to-tap” concerns, a majority are expressing relief,
according to officials in two affected communities.
“You always get one or
two who say they won’t drink it [recycled water],” said John Grant, general
manager of the Colorado River Municipal Water District (CRMWD; Big Spring,
Texas). “But people here have more appreciation for water than you might see in
an area where the supply is plentiful. Most are asking why we haven’t done this
This is good news to CRMWD, which supplies
untreated water to five West Texas cities, including Odessa and Midland. Faced
with dwindling supplies, the district recently completed the first direct
potable-water reuse (DPR) project in the U.S., a 7600-m3/d (2-mgd)
water-reclamation and reuse plant built next to the existing wastewater
resource recovery facility (WRRF) in Big Spring. Today, reclaimed water
produced there is blended with the untreated water from the city’s reservoir
and distributed to CRMWD member cities for conventional water treatment and
concerns accelerate acceptance
CRMWD customers aren’t alone in their
increasing acceptance of DPR. Some 400 km (250 mi) to the northeast in Wichita
Falls, Texas, residents are anxious for the completion next spring of a
19,000-m3/d (5-mgd) DPR project, said Daniel Nix, the city’s
utilities operations manager. Wichita Falls provides water and wastewater
services to about 120,000 residents of the city and the surrounding region,
which is also in the midst of a lengthy drought.
“People here realize that technology exists
to make our wastewater effluent reusable, and they know it is now going
downstream for someone else to use,” Nix said. “The question on their minds is
whether the plant will be up and operating before we run out of water in the
This is a legitimate concern in a community
that saw lake levels drop below 40% of capacity earlier this year.
Could Wichita Falls run out of water? “If we
have another year [in terms of rainfall] like 2011, it will be very close,” Nix
said. “If it’s more like 2012, it will extend our supply by 8 to 9 months.”
The current drought is hardly a first in this
part of the country.
“Every decade, we’ve needed more water,”
Grant said. Since the 1950s, CRMWD has constructed a series of reservoirs to
hold water from the Colorado River, in addition to developing Ward County
DPR is one of the few viable options that
remain, Grant said. It’s an approach the district began considering in 2002.
“We made the decision at that time that we
were not going to build any more lakes or reservoirs,” Grant said. “And the
good-quality groundwater is already taken.”
If the region were to grow, it needed
alternative water sources. “That’s when we began asking if there was a way to
reuse the water we were already sending to these cities, rather than developing
a new source,” Grant said.
CRMWD spent the next several years
determining its next step. It considered three possible sites for a
water-reclamation plant: a large WRRF plant in Odessa and two smaller ones in
Snyder and Big Spring.
In its research, the district made an
important discovery. “Whatever location we chose, it would take the same basic process
and technologies to treat the effluent to drinking water standards,” Grant
explained. “It’s how all the parts came together — where the water comes from,
where the output goes — that drove economic feasibility.”
In Odessa or Snyder, for example, reclaimed
water would have to be transported 48 km (30 mi) to injection wells for
discharge, Grant explained. In Big Spring, all it would take was a 90-m-long
(300-ft-long) pipeline to discharge the treated effluent into a nearby creek.
Those differences were reflected in the
projects’ estimated costs. In Big Spring, a water-reclamation plant could
produce about 7600 m3 (2 mgd) at a cost of about $0.92/m3
($3.48/1000 gal), compared to a larger-scale plant in Odessa that could produce
30,000 m3/d (8 mgd) — but at a cost of $0.26 more per 1 m3 ($0.98
more per 1000 gal).
By comparison, untreated water in the region
today costs about $0.71/m3 ($2.69/1000 gal). “No matter what new
water supplies we develop, the cost is going up,” acknowledged Grant. “If you
think otherwise, you are dreaming.”
Falls: Same song, next verse
Wichita Falls, where interest in alternative
water sources dates back to the late 1990s, tells a similar economics-driven
At that time, utility leaders identified two
projects to offset the shrinking reservoir supply: a reverse-osmosis system to
treat water in a previously untapped brine lake and a pilot microfiltration
system to treat effluent leaving the WRRF.
When the drought ended a year or two later,
the infrastructure was in place, but demand waned for the water that was
produced. By the time water shortages returned in 2011, environmental
regulations had grown more stringent, and the water the projects produced no
longer met permitting requirements.
The additional nutrient-removal requirements
for the brine lake were especially onerous, Nix said. “It was too much to get
our arms around in the short term,” he said.
The city instead began working with the Texas
Commission on Environmental Quality to determine how it might adapt the
microfiltration and the reverse-osmosis systems already in place to treat its
wastewater effluent to drinking water standards.
“If we were starting from scratch, the
economics wouldn’t have worked,” Nix said. Instead, it became a matter of providing
additional treatment to address three areas of deficiency and adding a pipeline
between the WRRF and reclamation plants.
To allay any lingering public misgivings,
officials in Big Spring and Wichita Falls point to multiple backup systems and
strict testing regimens.
In Big Spring, water quality is monitored as
it goes through each phase of treatment — microfiltration, reverse osmosis, and
ultraviolet disinfection. Testing begins even before it reaches the reclamation
plant. “If chlorine levels aren’t high enough, we won’t take it,” Grant said.
“If it doesn’t meet our parameters at any step along the way, we send it back
to the beginning.”
After it leaves the plant, the reclaimed
water is blended with untreated water, with the reclaimed water comprising 15%
or less of the initial blend, before it is distributed to CRMWD member cities
for conventional water treatment. When the pipeline connects with other
raw-water pipelines, it is diluted even further, Grant said.
When its operation comes on-line next spring,
Wichita Falls will follow a similar process but without the ultraviolet
disinfection, Nix said. Plans are to blend the reclaimed water with water from
two reservoirs at a 50:50 ratio prior to conventional water treatment.
There is no “magic” ratio of reclaimed to raw
water, Nix said. “These projects need to be considered on a site-by-site basis,
with the understanding that each project must be evaluated on its own merit,”
From a regulatory standpoint, reclaimed water
is no different from groundwater or river or lake water, Nix said. “You have to
look at the water quality and see what you have, and then put a treatment
process in place that brings it to regulatory standards,” he said.
DPR involves a learning curve for utilities
and regulators alike, Nix said.
Because few rules and regulations exist, it’s
important to confer with your regulatory agency from Day 1, Nix said. It’s also
critical to understand the quality of the effluent leaving the WRRF, which, in
many cases, is remarkably good.
“Forty years ago, when there were rivers on
fire, direct potable reuse was not doable,” Nix said. “But the Clean Water Act
changed all that. It has helped make wastewater effluent a high-quality
resource. We need to start treating it that way.”