POWER March 2016 - 20

WATER & WASTEWATER
Zero-Discharge Pozzolanic Brine
Solidification: Another Option for
Treating FGD Wastewater
Courtesy: GE
With its expected 30% to 50% lower capital expense and 20% to 40% lower operating
cost than traditional zero-discharge systems, a new approach to compliance
with the EPA's effluent limitation guidelines could be attractive.
Bill Heins and Lanny Weimer
I
n late 2015, the U.S. Environmental Protection
Agency (EPA) published new regulations
governing wastewater discharge
from steam electric power plants. These new
regulations, or effluent limitation guidelines
(ELGs), were put into place to reduce or
eliminate toxic metals and other pollutants
from entering surface water. Specifically
addressing flue gas desulfurization (FGD)
wastewater from coal-fired power plants, the
EPA identified best available technologies for
treating and discharging FGD waste, namely
chemical precipitation followed by biological
treatment for existing power plants, and
zero discharge for new facilities.
The ELGs also offer a voluntary incentive
program for existing plants that implement
zero discharge technology, allowing these
operators more time to meet the requirement.
Regardless of their treatment path, every
plant must comply with the ELGs between
2018 and 2023, depending on when its new
Clean Water Act permit is needed.
20
Not Your Father's Zero Discharge
System
Although both chemical/biological treatment
and evaporation/crystallization technologies
have become a staple in treating power plant
wastewater streams, zero discharge using
pozzolanic brine solidification is a new application
for the industry. Developed and optimized
over several years-and incorporating
many tried and true industry solutions-this
new technology is not like a traditional zerodischarge
system (Figures 1 and 2). First and
foremost, it requires an anticipated 30% to
50% less in capital expense because no softening
or crystallization is needed. As a result,
operating cost is also expected to be reduced
by 20% to 40%.
The new evaporator/solidification system
utilizes an evaporator or brine concentrator
followed by pozzolanic solidification to reduce
chemical addition, sludge handling, and
energy costs. It also reduces long-term environmental
risks by eliminating the discharge
of FGD wastewater and greatly simplifies
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landfill operations. This approach provides
a sustainable solution for power plant operators
while producing high-quality water for
recycle and reuse.
Development Path
GE started development of this technology
to solidify concentrated evaporator brines for
the oil sands industry in 2010 because that
industry generates large volumes of concentrated
evaporator brines when treating
produced water from steam-assisted gravity
drain (SAGD) operations. The Oil Sands
Leadership Initiative, a network of oil sands
operators, contracted GE to develop concentrated
evaporator brine solidification based
on pozzolanic chemistry. During this process,
several companies supplied produced water
samples of evaporator brine for solidification
process testing.
As a part of the process development program,
GE developed a three-tier bench-scale
treatability test protocol to identify the optimized
reagent blend, which included flyash
POWER | March 2016
http://www.powermag.com
POWER March 2016

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