Assessing Contaminants of Emerging Concern (CECs)
in Cooling Tower Drift
Authors: James P. Laurenson (HEAC) and Edward L. Carr (ICF International)
US-FL-Turkey Point
Background
One of the primary industrial uses of reclaimed water
is for recirculating evaporative wet cooling at electric
power generation plants. With power generation
expected to increase by about 18 percent in the United
States and close to 70 percent globally between 2012
to 2035 (EIA, 2011), the use of reclaimed water is
expected to increase as fresh water supplies for
cooling declines.
Wet cooling at power plants typically results in the
majority of cooling water leaving the plant via
evaporation and aerosolization, often collectively
known as drift. Drift, and any associated
microorganisms, particulate matter (PM), or chemicals,
can be inhaled by plant workers and the public. Other
exposures might occur, such as through dermal
contact or ingestion, but inhalation is expected to be
the dominant exposure pathway. If exposure is greater
than health-based thresholds, such as minimum
infective doses for pathogens, PM standards, or
minimal risk levels (MRLs) for chemicals, then risks
could be considered significant and require mitigation
through additional treatment or greater setback
distances from the towers. While considerable
attention in recent years has been given to the risks
and mitigations related to microorganisms and PM
levels in cooling tower drift at power plants, less
attention has been given to contaminants of emerging
concern (CECs), which are present in reclaimed water.
Capacity and Type of Reuse
Application
Florida Power & Light Company (FPL) and MiamiDade County (MDC) have been collaborating on an
agreement to use reclaimed water as the primary
supply for cooling for two new nuclear power units
(Units 6 and 7) that are proposed for completion in
2023 at the Turkey Point, Fla., facility (FPL, 2011). The
reclaimed water also would be used for cooling an
existing natural gas combined-cycle steam electric
generating unit (Unit 5) that currently uses
2012 Guidelines for Water Reuse
groundwater for cooling. Saltwater from Biscayne Bay
would provide a backup cooling water supply for all
three units. Waste heat would be dissipated by
mechanical draft cooling towers. Draw-down
(blowdown) wastewater from these towers would be
discharged through the use of deep injection wells to
the lower Floridan aquifer.
The use of reclaimed water at Units 5, 6, and 7 would
be in addition to the current primary cooling system in
place for existing units. The current system is a
closed-loop set of approximately 5,900 ac (2,390 ha)
of canals used for two natural gas/oil steam electric
generating units (Units 1 and 2) and two existing
nuclear units (Units 3 and 4). Because the canals are
not lined, groundwater flow interacts with the
hypersaline water in the canals, which has become a
source of concern for this ecologically sensitive area
within the Everglades watershed. Further, as part of a
broader water resources management plan, MDC
must increase its use of reclaimed water to more than
170 mgd (7450 L/s) by 2025. Thus, an MDC resolution
was passed that prevents FPL from applying for any
water withdrawals from the Biscayne aquifer and
encourages the use of reclaimed water.
As part of the Environmental Impact Statement (EIS)
being developed by the Nuclear Regulatory
Commission (NRC) for the application process, the
impact of the reclaimed water on the environment and
human health is being assessed (NRC, n.d.). One
area of concern highlighted by public comments is
inhalation of cooling tower drift by workers and the
public (NRC, 2010).
Water Quality Standards and
Treatment Technology
Under the current plan, MDC would produce and
deliver up to 90 mgd (3940 L/s), or 75 mgd (3290 L/s)
on average, of reclaimed water to Turkey Point (FPS,
2011). The reclaimed water would be treated using
high-level disinfection in accordance with Florida
Department of Environmental Protection (FDEP)
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Appendix D | U.S. Case Studies
regulations (Florida Administrative Code 62-610.668).
Reclaimed water would be conveyed 9 mi (14 km) via
pipelines from to the Turkey Point plant property where
an onsite FPL treatment facility would further treat
reclaimed water to reduce iron, magnesium, oil and
grease, total suspended solids, nutrients, and silica to
suitable concentrations for the circulating water
system.
only. Non-volatile CECs thus also are likely to be
deposited in a similar fashion, i.e., with the majority of
deposition occurring in the immediate vicinity of the
cooling towers. Screening level modeling of CECs
exposure is being conducted by NRC and will become
publicly available when the draft EIS is published in
the near future.
For each of the two proposed nuclear power units, the
cooling system would consist of three mechanical draft
cooling towers and an open channel (flume) with a
pump intake structure. Heated cooling water would
flow through return piping to the mechanical draft
cooling towers where heated cooling water would be
circulated and heat would be transferred to the
ambient air via evaporative cooling and conduction.
After passing through the cooling tower, the cooled
water would collect in the tower basin and be pumped
back to the power unit, completing the closed cycle
cooling water loop.
Makeup water from the FPL reclaimed water treatment
facility would compensate for water losses during plant
operation from drift and blowdown. Six circulating
water cooling towers for Units 6 and 7, plus the
existing Unit 5 towers, are estimated to result in
evaporation and aerosol water losses of approximately
50 mgd (2190 L/s) during normal plant operation, or
approximately 67 percent of the makeup water.
Exposure Modeling
An Environmental Report (ER), often used as a
reference for developing an EIS, has been developed
for Turkey Point (FPL, 2011). In the ER, the EPA
CALPUFF and AERMOD dispersion models were
used to evaluate cooling tower plume behavior. Five
years (2001 through 2005) of hourly meteorological
data from the Miami International Airport were used,
along with physical and performance characteristics of
the mechanical draft cooling towers. In the current
version of the ER, CEC exposure has not been
assessed, in large part because the additional
treatment that FPL will apply to the reclaimed has yet
to be fully designed. In the meantime, NRC is
examining as a surrogate analysis the expected salt
deposition described in the ER for the scenario
whereby saltwater from Biscayne bay would be used
as a backup cooling water source for Units 6 and 7.
Figure 1 illustrates the predicted salt deposition near
the plant when these units would be using salt water
2012 Guidelines for Water Reuse
Figure 1
Surrogate for CECs deposition: predicted monthly
salt deposition from use of only Biscayne Bay water
for backup cooling (Photo credit: FPL, 2011)
D-108
Appendix D | U.S. Case Studies
References
Energy Information Administration (EIA). 2011. International
Energy Outlook 2011. Retrieved on April 2, 2012 from
<http://www.eia.doe.gov/oiaf/ieo/electricity.html>.
Florida Power & Light (FPL). 2011. Turkey Point Plant, Units
6 & 7, COL Application, Part 3, Environmental Report.
Retrieved
on
March
25,
2012
from
<http://pbadupws.nrc.gov/docs/ML1136/ML11362A171.html>.
U.S. Nuclear Regulatory Commission (NRC). n.d. Turkey
Point, Units 6 and 7 Application. Retrieved on Sept. 5, 2012
from <http://www.nrc.gov/reactors/new-reactors/col/turkeypoint.html>.
U.S. Nuclear Regulatory Commission (NRC). 2010.
Environmental Impact Statement Scoping Process,
Summary Report. Retrieved on March 25, 2012 from
<http://pbadupws.nrc.gov/docs/ML1031/ML103130609.html>.
2012 Guidelines for Water Reuse
D-109