POWER March 2017 - 34

WATER & WASTEWATER
Using Reclaimed Water in Power
Plant Cooling Applications
Courtesy: Jirí Sedlácek/Wikipedia
Using reclaimed water as a makeup supply for cooling tower systems has become
a popular option for reducing impacts on local water resources, but it comes with
its own challenges because of its unique chemistry. Use of a novel terpolymer can
greatly reduce the operational costs involved.
Robert A. Hendel, Caroline Sui, and Jeffrey Melzer
M
ounting trends in global water
stresses are creating an urgent
need for water conservation
strategies across industries that depend on
large volumes of reliable supplies. The power
industry, one of the heaviest users in the U.S.,
requires tremendous amounts of water for
use in cooling towers. Based on heightened
concerns related to water scarcity, greater
competition for limited freshwater resources,
and driven by the need to minimize risks related
to water supply disruptions, the power
industry is increasingly being forced to turn
to non-traditional resources.
One option is treated municipal wastewater,
or reclaimed water, which can help
relieve strains on diminishing freshwater
supplies. In recent years, the use of reclaimed
water as a makeup water source in power
plants has become more prevalent, especially
in drought-prone areas such as the Southwest
and water-challenged regions like Florida.
Indeed, reclaimed water is becoming the
standard for new power plant construction
as well as a viable alternative makeup water
source for existing facilities that are looking
34
to expand production. (For one recent example
of such a retrofit, see Tampa Electric
Co.'s Polk Power Station, a 2015 POWER
Top Plant.)
However, the use of reclaimed water for
cooling tower applications represents a dramatic
departure from freshwater. Not unexpectedly,
reclaimed water presents a number
of operational risks and challenges related to
the propensity for elevated and variable concentrations
of phosphate, ammonia, organics,
chlorine, select metals, and other potentially
problematic constituents. In particular, the
phosphate concentration is a key factor that
can dictate process requirements and operational
parameters of the cooling water system
in large part due to its tendency to form scaling
species such as calcium phosphate.
High-phosphate reclaimed water can also
exert additional challenges on cooling water
chemistries, dictating the need for pretreatment/treatment
steps, limiting attainable
cycles, and impacting overall performance.
In some cases, the level of phosphate concentration
is a primary factor in determining
whether a wastewater source is a suitable
www.powermag.com
makeup water option.
This analysis explores the key drivers,
risks and challenges, and treatment approaches
in using reclaimed water as a cooling
tower makeup supply in power plants.
Particular emphasis is placed on an advanced
chemical treatment program that allows for
reclaimed water with variable and elevated
phosphate levels to be used in a cooling
tower system. This chemical approach-a
novel terpolymer-has demonstrated that
high-concentration phosphate waters can be
successfully maintained in a cooling tower
without the need for additional unit operations
and pretreatment/treatment steps, thus
eliminating capital- and operational-intensive
processes and increasing the applicability
of available reclaimed waters that can be
used as a makeup water supply.
Reclaimed Water Characteristics
" Reclaimed water " refers to municipal wastewater
that has been treated to meet specific
water quality criteria with the intent of being
reused for a range of beneficial purposes.
Widely available in sufficient volumes across
POWER | March 2017
http://www.powermag.com
POWER March 2017

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