A.6 Laboratory Eliminates Single-Pass Cooling
proximity to Lake Superior, MED made a concentrated effort to eliminate all uses of
potable water for non-contact, single-pass cooling and replace it with lake water. As
a result, MED was able to reduce its total potable water consumption by 90 percent.
Instead of sending the lake water to the sanitary sewer, however, once the water is
used, it is sent directly back to Lake Superior. Since the cooling water doesn’t come in
contact with any sources of contamination, it can be returned in the same quantity
and quality as before without any needed treatment.
In addition, from a 2009 water assessment at MED (see the discussion in
A.2: Federal Agency Implements Comprehensive Water Management Strategy
noted that a significant amount of potable water was still used to supply single-pass
cooling of an ice machine. At a flow rate of 0.54 gallons per minute (gpm), MED was
discharging approximately 283,000 gallons of water per year to the sewer just to cool
the ice machine. As a result of the assessment, MED recalibrated the cooling water
control valve to only allow water to flow when needed for cooling. Ultimately, MED
decided to eliminate this single-pass cooling water use by replacing the ice machine
with an ENERGY STAR® qualified, air-cooled model. This replacement allowed MED to
completely eliminate the use of potable water for single-pass cooling at the facility,
and even further reduce its overall potable water consumption.
By shifting to using lake water for non-contact, single-pass cooling, MED was able to
reduce its potable water use by 90 percent between 1993 and 2003, which resulted in
a water savings of approximately 7.5 million gallons per year or 55.4 million gallons in
total, as illustrated in Figure A-5.
Figure A-5. MED PotableWater Use, 1987 to 2003
Water Use (in thousands of gallons)