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Dairy Plant Reduces
Water Use and BOD Saving Over $26,000
Fine Tuning Clean-In-Place Systems (CIP)
| Company |
110-employee Minnesota dairy |
| Results |
Decreased water use by adjusting CIP systems.
Saved over 8.5 million gallons of water and over
$20,000 annually. Decreased biochemical oxygen
demand (BOD) loading by 2.5 percent, saving an
additional $6,000 per year.
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Process Background
In 1999, a Minnesota dairy plant received
1.7 million pounds of milk daily to produce cream, cheese,
lactose products and protein concentrates. The 110-employee
facility made 96,000 to 160,000 pounds of cheese per day.
At the end of each day’s run, clean-in-place (CIP) systems
sanitized the equipment, readying it for the next day.
Incentives for Change
Together, the plant and its adjunct product drying facility
started overloading its water pretreatment plant—both
with water volume and BOD. BOD is a measure of how much oxygen
is required to biologically decompose organic matter in the
water. Because the water pretreatment plant was at capacity,
the company could not expand the operation at the dairy plant
and it was charged for the excess loading.
The dairy speculated that the flushes and
rinses of its CIP systems were too long, contributing to the
overloading of the water pretreatment plant. With all employees
focused on production, the company did not have extra staff
time to analyze water use from all of its CIP systems or to
fine tune the computer program that ran the CIPs.
In the summer of 1999, the dairy requested
a MnTAP intern to review most of its CIP systems. The
intern's research confirmed that the rinses were consuming
excess water. He evaluated and adjusted the duration of the
water flushes and rinses, and also investigated ways to reduce
BOD loading.
CIP Systems
CIP eliminates the need to dismantle equipment in order to
clean and sanitize. Many production facilities manually run
CIP systems. Fully automated CIP is more consistent than manual
operations and the level of cleaning is typically more effective.
If facilities produce multiple products, fully automated CIPs
help maximize the use of equipment.
The technology of each room’s CIP system
at the dairy varied. Aside from the few manually operated
CIP systems, all CIP systems were controlled and monitored
by the Programmable Logic Controller (PLC). It was programmed
to run pumps and valves, control timing and temperatures,
and monitor conductivity and other parameters. The CIP process
generally consists of rinses, which go to the drain, and acid
and caustic washes, which return to the tanks for reuse.
Reducing Rinse Water
The CIPs assured product consistency and sanitary production conditions. But, the company speculated that the flushes and rinses for production cleaning were generous and possibly excessive. Working with dairy's employees, the intern optimized CIP rinse times for:
- pre-rinses which clear the line of material.
- rinses between wash solutions which separate chemical washes.
- post-rinses which clear the line of all chemical wash solution.
Overall, pre and post rinses were shortened slightly and wash rinses were shortened substantially.
Example of CIP changes:
evaporator room
In the evaporator room, whey permeate and whey protein are
concentrated. It was the plant's most diverse room and the
one with the most advanced CIP. The rinse that falls in between
the wash solutions had the greatest potential for reduced
water use.
The CIP systems were set to rinse wash solutions
completely from the lines—bringing the conductivity to
zero—before the next wash solution was added. Depending
on the length of the line or tank being cleaned, hundreds
of gallons of fresh water went down the drain. The intern
found that conductivity did not need to return to zero. Rather,
it only needed to dip down to a minimum conductivity to signal
the PLC when the solution could be returned to the tank for
reuse and when to begin the next wash.
Because conductivity was measured at the
end of the line and the supply pumps and valves were at the
beginning, the CIP was programmed with a "wash return
delay." This prevented the CIP from using the conductivity
measure of the exiting wash solution to represent the wash
solution entering the system.
Rinse results
Adjustments like those in the evaporator room yielded similar
water use reductions in most of the dairy's production rooms.
All together, the company saved nearly 8,500,000 gallons of
water and $20,100 annually.
| CIP savings |
|
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gal water/yr
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$/yr
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| Evaporator room |
1,858,000
|
$4,070
|
| Make room |
4,243,000
|
9,970
|
| Standardizing room |
216,000
|
550
|
| Intake room |
1,474,200
|
3,940
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| Block former |
680,400
|
1,570
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| Totals |
8,471,600
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$20,100
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Decreasing BOD Loading
BOD waste streams all resulted from either mechanical or operational
procedures. Often CIP procedures contributed significantly
to BOD loading, especially during cleaning at the end of a
day’s run when the product remaining in the line is washed
down the drain. Other operations also resulted in excess BOD
loading. For example, when sanitizing was initiated too early
on the slurry line the amount of product loss doubled.
The solutions to most of these problems
were adjustments to operating procedures. By requiring operators
to flush systems before they are drained at the end of the
day, only five to six percent solid waste exited the machine
instead of 20 percent. By not pushing the sanitizing button
while the clarifier was desludging, BOD loading was reduced
by almost a third in that room.
Overall Results
With the assistance of a MnTAP intern and a MnTAP staff person,
the dairy was able to reduce its waste effectively without
overhauling its current technology. The company decreased
water use by nearly 8.5 million gallons annually, saving over
$20,000. The dairy also decreased its BOD loading by 2.5 percent,
saving an additional $6,000 per year. The company has since
expanded production.
More Information
MnTAP has a variety of technical assistance services available to help Minnesota businesses implement industry-tailored solutions that maximize resource efficiency, prevent pollution, increase energy efficiency, and reduce costs.Our information resources are available online or,
call MnTAP at 612.624.1300 or 800.247.0015 from greater Minnesota
for personal assistance or more information about MnTAP’s
Intern Program.
This project was conducted in 1999 by MnTAP
intern, Zachery Perry a junior at University of Notre-Dame.
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