Environmental Science & Engineering - www.esemag.com - July 2005
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Membrane wastewater treatment plants cropping up in food industry
By Lawrence Novachis
Variability is unacceptable in
the food and beverage
industry. Great care is taken
to ensure that production
lines are finely tuned to deliver high
quality products that consistently meet
customer expectations every time.
Whereas variability in manufacturing
is virtually unthinkable for quality
controllers, the unpredictable nature of
the byproducts generated by the food
and beverage industry is a constant
challenge for wastewater treatment
plants and their operators.
Such is the case for Richardson
Foods, a growing food manufacturer in
the small south-western Ontario town
of St. Marys that makes a wide range
of condiments including sauces, sundae
toppings, drink syrups, and salad
dressings. With the capability to manufacture
over 200 different products
for the food service industry,
Richardson Foods, a division of Heinz
Canada, has as much diversity in its
product lines as it does in its wastewater
composition.
“There is a great deal of variability
in the wastewater that the plant produces,”
says Ivan Facey, Environmental
Technician, at Richardson Foods. The
wastewater is high in oil, grease and
sugar, and changes every day; it really
depends what particular products are
being manufactured. We see BOD
ranging from 1,500 to 4,000 mg/L,
while COD can go from 3,500 to 6,000
mg/L.”
Like many food and beverage manufacturers,
Richardson Foods is not
permitted to discharge its raw wastewater
to the municipal sewer since the
high organic content would overwhelm
the community’s wastewater treatment
plant (WWTP). An on-site system was
required, and in 1986, Richardson
Foods installed a sequencing batch
reactor to provide pretreatment of the
wastewater prior to releasing it to the
municipal WWTP.
Food production continued to increase,
and by 1999, the batch reactor was having
trouble treating up to 189 m3/day
(50,000 GPD) of nutrient-rich wastewater.
Although the plant implemented
innovative new procedures to dramatically
reduce water consumption, the aging
batch reactor was still having difficulty
keeping up. The neighbours also noticed,
as odours from the plant’s equalization
tanks, which held the raw wastewater
prior to treatment, would waft through
town on hot summer days.
“In 1999 Richardson Foods began
constructing a much larger facility about
one kilometre (0.6 miles) from our previous
site,” says Dave Dykeman,
Maintenance and Engineering Manager,
at Richardson Foods. “We saw this as an
ideal opportunity to upgrade our onsite
wastewater treatment plant to a system
that would treat the highly variable
waste stream from our production lines.
We wanted a system that was robust,
highly automated, efficient both in cost
and process, and would produce very little
odour.”
Richardson Foods explored several
options that included conventional systems
and membranes. The company’s
evaluation showed that a ZENON
immersed ultrafiltration (UF) membrane
system would provide the best
performance at the lowest cost, and the
containerized ZeeWeed® industrial
system could be easily and cost-effectively
expanded and upgraded to
accommodate future needs.
ZENON supplied complete designbuild
services to Richardson Foods,
providing a single-source of accountability
for the turn-key project. The
plant was quickly constructed in seven
months during 2000, and included an
equalization tank, a dissolved air flotation
(DAF) pretreatment system, a
membrane bioreactor system, and all
pipes, pumps, blowers, and control
equipment.
“Our new treatment plant has introduced
many new processes for us to
manage such as the DAF system, the
membranes, and more recently a new
filter press,” says Dave Dykeman.
“However, the treatment plant is only
about half the size of the old one, and
its automated functionality means that
we can still run it with only one operator.”
Wastewater from the food manufacturing
processes is first discharged to
an equalization tank and is then
pumped into the DAF system for oil
and grease removal. Pretreated wastewater
is pumped to an aerobic bioreactor
where sugars and other organic
compounds are digested before the
mixed liquor is pumped to the membrane
tanks.
ZeeWeed membrane cassettes are
immersed directly in the mixed liquor
and provide ultrafiltration for up to
150 m3 (40,000 gallons) of wastewater
per day. Thousands of membrane
fibers hang loosely in each membrane
cassette and a slight vacuum is applied
to the end of each membrane fiber to
draw water through microscopic pores
and into the hollow fibers. With a
nominal pore size of 0.04 µm, the
membrane fibers act as a physical barrier,
preventing suspended solids from
entering into the final effluent.
“The ZeeWeed system produces
effluent with a BOD reading that
ranges between 2 to 10 mg/L, well
below the regulated BOD requirement
of 300 mg/L for the municipal sewer,”
says Ivan Facey.
Since the system removes solids by
filtration rather than settling, the
process is much faster than conventional
treatments, and can operate at a
much higher mixed liquor suspended solids (MLSS) concentrations. Richardson
Foods operates its bioreactor at an
MLSS of 12,000 mg/L, compared to
3,000 to 5,000 mg/L for a conventional
system.
This higher MLSS concentration in
the ZeeWeed MBR, coupled with a
longer solids retention time, means
that Richardson Foods is producing far
less sludge than with its previous batch
reactor system. The batch reactor
would produce about 30 m3 (8,000 gallons)
of sludge per day that had to be
removed by tanker truck, whereas the
MBR produces only about 15 per cent
of that amount.
Tanker trucks are no longer
required by the company since the filter
press was installed. The press
dewaters sludge from the DAF and the
MBR to 35 per cent solids that are disposed
of in the landfill, which has
reduced disposal costs by an additional
15 per cent.
The efficiency of the system, combined
with the new equalization tank
has also dramatically reduced odours
from the plant. The new equalization
tank is completely covered with only a
small vent to release gases. However,
the membranes provide much faster
treatment than the old batch reactor, so
raw wastewater does not sit for long in
the equalization tank. According to
Ivan Facey the equalization tank is seldom
more than 50 percent full for any
length of time.
“We have a subdivision right across
the road from the plant, but since our
new system went online we have not
had a single complaint about odour,”
Ivan Facey says. “With our old plant, it
was almost a daily occurrence during
the warm summer weather.”
The operation of the system is highly
automated and fibers can be easily
cleaned with a clean-in-place backpulsing
process that forces permeate
water back through the membranes.
This dislodges any particles that may
adhere to the membranes. Aeration of
the membranes is also used to scour
debris from the fibers and provides
mixing within the process tank to
maintain solids in suspension. When
necessary, in situ chemical cleaning
can be automatically performed if
membrane fouling reduces permeability
below a specified performance
level.
Efficient and automated cleaning
processes have also reduced some
chemical usage for Richardson Foods.
The batch reactor required approximately
300 L of hypochlorite per week
to combat filamentous bacteria growth
in the bioreactor. However, Ivan Facey
is not concerned about such bacteria in
the ZeeWeed MBR, and has been able
to reduce the plant’s hypochlorite consumption
to just 40 L/week, which is
now used for membrane cleaning
processes.
Food and beverage producers
throughout North America and the
world are turning to advanced membrane
technology to achieve regulatory
compliance with compact and costeffective
on-site wastewater treatment
plants. The modular technology can
easily accommodate much larger producers
with greater volumes of wastewater,
such as a potato processing
plant in Idaho that produces 5,000
m3/day (1.3 MGD) of wastewater that
is high in nitrogen. Constructed and
commissioned in only seven months,
ZeeWeed MBR reduced total nitrogen
to only 6 mg/L, enabling the potato
processor to safely discharge the effluent
into the environment.
The membranes can also upgrade
an existing conventional treatment
plant to produce tertiary quality effluent.
Such was the case for a large olive
cannery in California that needed
advanced treatment for wastewater that
is high in ferrous gluconate, acetic
acid, salt, sodium benzoate, calcium
chloride, soluble organics, and organic
particulate. The membranes now filter
up to 3,000 m3/day (800,000 GPD) of
effluent from the plant’s bioreactors
and produce high quality water that is
discharged directly to a local river. The
plant does not discharge any wastes to
the municipal treatment plant and no
longer pays municipal surcharges for
wastewater treatment.
Membrane-based wastewater treatment
options vary considerably for
food and beverage producers—from
retrofit applications for existing plants
to compact new systems that will not
only meet or exceed today’s requirements
but will position operators to
comply with increasingly stringent
regulations that are yet to come.
Lawrence Novachis, P.Eng., MBA,
is Vice-President, Industrial Systems,
ZENON Environmental Inc.,
www.zenon.com
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