POWER July 2021 - 24

WATER AWARD
Eco-Friendly Ultrasonic
Treatment System Controls Algae
in Power Plant Settling Pond
Courtesy: LG Sonic
Water treatment professionals often turn to chemicals to control algae in power
plant settling ponds. While this can be effective, environmentally friendly ultrasonic
technology may do a better job at a fraction of the cost-and with no harm to fish
or plants.
Aaron Larson
T
he National Pollutant Discharge
Elimination System (NPDES) permit
program was created in 1972 by the
Clean Water Act. The NPDES helps address
water pollution by regulating point
sources that discharge pollutants to waters
of the U.S.
Effluent limitations serve as the primary
mechanism in NPDES permits
for controlling discharges of pollutants
to receiving waters. Effluent limitations
guidelines and standards are established
by the U.S. Environmental Protection
Agency for different non-municipal
categories. These guidelines are developed
based on the degree of pollutant
reduction attainable by an industrial category
through the application of pollutant
control technologies.
It can be difficult for power plants to
comply with NPDES permit limits. For
example, Northern Indiana Public Service
Co.'s (NIPSCO's) Rollin M. Schahfer
Generating Station, located in Jasper
County near Wheatfield, Indiana, operates
four coal-fired units with a combined
capacity of about 1,943 MW. The
facility takes its cooling water from the
Kankakee River. Before being returned
to the river, the water is discharged to a
final settling basin, which has a surface
area of about 194 acres and an average
depth of about 10.7 ft. The water must
meet NPDES permit limits when being
discharged back to the river.
Among the requirements are that the
concentration of total suspended solids
24
(TSS) must be less than 30 parts per million
(ppm) on a daily basis and less than
15 ppm on a monthly average, and the
water pH must be less than 9. Settling
ponds are commonly rich in nutrients,
and the temperature of water in Schahfer's
basin is warmer than river water,
having absorbed heat in condensers
while passing through the plant. This
causes algae to grow at a relatively fast
rate, and algal blooms have an adverse
effect on TSS and pH.
NIPSCO used algaecides for years
in its cooling water program in order to
meet the NPDES limits at the final settling
basin. However, algaecides can be
expensive and options were limited because
algaecides could not be directly
added to the basin due to the pond
discharge going back to the river. The
company tested other options to lower
TSS levels, but results were inconsistent
and filters from TSS samples were often
green. Filtration of the pond discharge
was considered, but it was not really an
economical option.
Ultrasonic Treatment
Finally, NIPSCO came across LG Sonic,
a company that calls itself a " leader in
sustainable algae management. " NIPSCO
worked directly with the company
to develop an ultrasonic solution, utilizing
LG Sonic's MPC-Buoy technology. MPCBuoy
is a floating solar-powered system
that combines real-time water quality
monitoring and ultrasonic sound waves
to effectively control algae.
www.powermag.com
" Controlling algae with low-power ultrasound
is a well-established technology
that has been in existence for many
years. It is an environmentally friendly
technology that is harmless to fish and
plants, " Lisa Brand, CTO for LG Sonic,
told POWER.
Ultrasound can be used in both fresh
water surfaces, such as lakes, drinking
water reservoirs, and irrigation basins,
as well as in maritime environments. By
controlling the algae, it is possible to improve
the clarity of the water, and reduce
TSS and pH.
The Science Behind the
Technology
To understand how LG Sonic's MPCBuoy
system targets algae, it is helpful
to understand algae's growing mechanism.
All single-celled planktonic algae
use some form of buoancy regulation to
remain at the surface of the water where
most light is available, Brand explained.
During the day, algae are photosynthesizing
in the top layer, using carbon dioxide
and dissolved nutrients from the
surrounding water to produce oxygen
and polysaccharides.
To control algae, the LG Sonic system
transmits specific ultrasonic waves in
the water. The sound waves can spread
through the water column for hundreds
of meters. The ultrasound waves create
a sound layer in the top layer of the water,
which affects the buoyancy regulation
of the algae, fixing them in the water
column. The algae cells sink to the deepPOWER
| July 2021
http://www.powermag.com
POWER July 2021

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