| intern summary |
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Sparta Foods Saves Nearly $10,000 through
Water Conservation
Water Use and Wastewater
Loading in the Food Processing Industry
| Company |
Sparta Foods, St.
Paul, Minnesota |
| Results |
Reduced water use
by nearly 1.9 million gallons a year. |
|
Process
Background
Sparta Foods is a Mexican food producer manufacturing flour
tortillas, salsa, barbecue sauces, corn tortillas and corn
chips. They have approximately 125 employees.
Before the intern project,
Sparta used an average of 25,000 gallons of water daily, costing
$125 a day in sewer fees. In the past, they had paid as much
as $25,000 annually in strength charges for total suspended
solids (TSS) and chemical oxygen demand (COD).
Incentives
for Change
The wastewater treatment plant was going to access service
availability charges (SAC) of $10,200 unless Sparta was able
to show reduced water use.
Water
Use
Processing whole-kernel corn accounts for 70 percent of Sparta's
overall water use. Water is used to cook, transport and wash
the corn.
Corn Flushing. After
being cooked, the corn was flushed with water to cool it and
lower the pH. The intern found that the flushing was ineffective
at cooling corn below the surface and the pH was relatively
unchanged regardless of the time for flushing.
Automatic shut-off valves were
installed to control the amount of water used to flush the
corn. The valves will help eliminate excess flushing and reduce
tank overflow by decreasing the volume of incoming water.
Savings: Approximately $4,500
in water costs annually by eliminating the use of 3,000 gallons
of water daily—10 percent of overall water use.
Corn Transporting. Sparta
used 5,200 gallons of water daily to transport the corn from
the cooking tanks. The intern researched dry methods to transport
corn: 1) Screw conveyors were unacceptable because they degraded
the corn. 2) Although belt conveyors might work on the vertical
cook tanks of the chip line and reduce water by 10 percent,
the initial investment was not justifiable.
In a test, the intern recycled
20 percent of the transport water back into the process. Recycling
did not affect product quality, neither pH (which affects
shelf life of the product) nor cleanliness (which affects
appearance). Higher recycling rates could be tested to determine
what rate is most efficient for the process while maintaining
product standards.
Potential savings: Recycling
20 percent of the transport water could save approximately
1,040 gallons daily—3.5 percent of overall water use—
savings $1,570 annually.
Equipment Cleaning. The
flour product line is first given a dry cleaning by scraping
and blowing compressed air over the equipment. After a sweeping,
high-pressure washers and normal garden hoses are used.
High-pressure washers ($200)
can replace the garden hoses to clean the equipment more quickly
and efficiently, using half the water.
Potential savings: Replacing
hoses with high-pressure washers will return a savings of
$1,050 per year by reducing water use by 217,000 gallons annually.
Substituting Ingredients.
Using corn flour eliminates the need for water to cook, wash
and transport the whole corn. Sparta plans to substitute corn
flour in only ten percent of its stone-ground corn products
because switching from stone-ground corn to flour can alter
product quality.
Potential savings: $2,300
per year from reducing water use by 477,000 gallons annually.
Decreases water use by five to six percent.
Lawn Sprinkler. Sparta
has already reduced water use by shutting off the lawn sprinkler
system. During August, the system used 84,000 gallons, 8.4
percent of the total water used.
Savings: Over $400 a month
in water costs.
Wastewater
Loading
Because the corn wash water elevates TSS and COD levels in
the wastewater, the intern investigated several options for
removing the corn solids for use as animal feed. An estimated
one ton per day of corn sludge could be reclaimed if solids
could be removed.
Because the sludge has a 95
percent moisture content the food recycler's pick-up fee would
not be economical. Reducing the moisture to 60 to 70 percent
by dewatering would eliminate any pick-up charges.
Options. Several equipment
options were identified: 1) A filter followed by a centrifuge
was too expensive. 2) With the gravity screen and belt press,
the press was unable to remove water when tested. And, 3)
a rotating drum with an evaporator was not tested.
Potential savings: If a
workable method is found, Sparta could save $16,500 in strength
charges per year.
Results
Implementing water conservation options has reduced Sparta's
water use by nearly 1.9 million gallons a year—saving
almost $10,000 annually. They are working toward reducing
water use by 25 percent overall.
More
Information
MnTAP has a variety of technical assistance services available
to help Minnesota companies to manage and reduce their industrial
waste. If you would like assistance or more information about
MnTAP's Intern Program, call 612.624.1300 or 800.247.0015
from greater Minnesota.
This
project was conducted in 1996 by MnTAP intern Jeremy Yarwood,
a civil/environmental engineering senior at the University
of Minnesota.
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