POWER March 2017 - 41

WATER & WASTEWATER
A Two-Stage Process
ACTIFLO Turbo technology (Figure 3) uses
a patented draft tube design to flocculate
incoming solids with a proprietary
microsand. The dense microsand acts as
a ballast as flocculation occurs, and dramatically
increases the settling rate of
the solids. This results in excellent solids/metals
separation, using a very small
footprint. Hydrocyclones
separate
the
sludge from the microsand, and recycle it
back into the unit, adding to the sustainable
operation of the unit by minimizing
sludge volume.
The Hydrotech Discfilter process offers
the following benefits:
■ Low cost gravity filtration
■ Low power consumption
■ Small footprint
■ Continuous filtration
■ High water recovery
■ Low backwash rate (no large pumps or
sumps required)
■ Automatic backwash and flat panel design
are easy to keep clean
■ Low installed cost (can use existing
basins for frame design or flat pad for
tank designs)
3. State-of-the-art clarification. ACTIFLO is a high-rate, compact water clarification
process in which raw water is flocculated with microsand and polymer in a Turbomix
draft tube reactor. Courtesy: Veolia Water Technologies
Hydrocyclone
To sludge
treatment
Treated
water
Replicated Success
Veolia has also helped clients in custom-designing
biological processes to resolve other
specific treated effluent challenges, such as
ammonia. In New Jersey, Veolia furnished
West Deptford Energy with a BIOSTYR
biological aerated filter and Hydrotech
Discfilter system, allowing effluent from a
municipal wastewater plant to be reused in
the operation of their new environmentally
friendly energy station.
Polymer
Raw water/
Coagulant
The city turned to Veolia Water Technologies,
a global expert in optimizing water use
and wastewater treatment. Veolia provided
a two-stage treatment process using a combination
of its ACTIFLO and Hydrotech
Discfilter (Figures 1 and 2) processes (see
sidebar). The first stage ACTIFLO process
is a compact, extremely high-rate clarification
system that utilizes the combination of
coagulation, flocculation, and sedimentation,
using microsand as a seed for floc formation.
The microsand provides surface area
that enhances flocculation and acts as a ballast
or weight. This first stage was designed
to provide phosphorus removal for all of the
WWTP's current and future needs. The second
stage provides additional filtration to
meet the California Title 22 water reuse requirements,
which focus on suspended solids
and effluent turbidity reduction.
The system enabled the city to avoid
supplying water from its local surface and
groundwater supplies to the power facility
in order to accommodate the plant's needs.
Annual savings for the city from the process
March 2017 | POWER
changes were estimated to be about 680 million
gallons of water and $1.5 million in potable
water costs. In saving its natural water
supply and monetary expenses, the city was
able to turn waste into a resource.
The effluent water characteristics produced
by the Mankato treatment facility are:
■ Total phosphorus <0.4 milligrams/liter
(mg/L)
■ Total suspended solids <5 mg/L
■ Turbidity
<0.6
unit
■ Biochemical oxygen demand <2 mg/L
The water reuse project was the first of
its kind in the state of Minnesota and one
of the first in the nation. The Minnesota
chapter of the American Public Works Association
gave the Mankato facility its Project
of the Year award following the treatment
process upgrade, and it was also honored
with a Minnesota Government Reaching
Environmental Achievements Together
(MnGREAT) award (see opening photo).
www.powermag.com
nephelometric
turbidity
The BIOSTYR process (Figure 4) combines
biological treatment and filtration into
one compact system, removing ammonia and
a majority of wastewater solids. The BIOSTYR
effluent is then gravity fed into the
Discfilters, which provide an ideal filtration
system for solids removal above 10 micron,
thus producing much cleaner water needed for
use in plant operations. The use of recycled
water has proven to be a win for the environment
and for West Deptford Energy in saving
significant chemical oxidant costs while making
their power station a model of highly efficient
and sustainable energy generation.
After the power plant was operating, West
Deptford Energy decided to add ultrafiltration
(UF) to further treat the effluent from the
Discfilters. The UF treated water was a suitable
source for their existing boiler feedwater
system, which further reduced their reliance
on city water and the cost associated with it.
As the strain on freshwater resources
intensifies and energy demand grows, the
power industry is increasingly turning to reclaimed
water as a highly valuable resource.
Reclaimed water offers a win-win solution
that ensures the continued ability to respond
to rising global demand by an inseparable
pair. ■
-Michael Pudvay (michael.pudvay@veolia.com)
is an industrial projects business
development manager at Veolia Water
Technologies.
41
4. BIOSTYR. The BIOSTYR biological aerated
filter system removes ammonia and a
majority of solids from municipal wastewater.
Courtesy: Veolia Water Technologies
http://www.lia.com http://www.powermag.com
POWER March 2017

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