Recycling Treated Municipal Wastewater for Industrial Water Use

Table 1.2. Water Use in Minnesota, 2004
Annual Average Water Use, mgd
Ground Surface
Category Water Water Total
Air Conditioning 6 1
7
Industrial Processing 56 385 442
Major Crop Irrigation 175 28 203
Non-Crop Irrigation 20 6 26
Power Generation 4 2,375 2,380
Special Categories 19 15 33
Temporary 4 1 5
Water Level Maintenance 5 95 100
Water Utilities 355 201 556
Total 644 3,106 3,750
Source: MDNR, 2004
Section 1: Introduction
Recycling Treated Municipal Wastewater for Industrial Water Use
Nearly two-thirds of the potable-quality
water supply in Minnesota is from
ground water, as depicted in Figure 1.2.
Water withdrawn by industries (those not
served by water utilities) for various
processing needs accounts for about 12%
of the total water used in Minnesota.
In terms of 2004 daily average demands,
nearly 2,500 million gallons per day
(mgd) of water was used by the state’s
power generation industry and over 500
mgd served as a potable-quality supply
for a variety of uses. Over 400 mgd was
withdrawn directly by industries for use
in their businesses.
Figure 1.2. Water Use in Minnesota Without Power Generation, 2004
Water Use, mgd
600 Surface
Water
500
400
300
200
100
0
Air
Cond.
Source: MDNR, 2004
Industry Crop
Irrig.
Water use was analyzed with a focus on
sources most vulnerable to water supply
limitations. Because little water is consumed in once-through cooling processes, replacing surface water
sources with recycled wastewater does little to conserve water. To benefit the state’s water resources,
recycled wastewater typically should replace a water supply that is used and not returned to its source of
origin. This applies to all uses of ground water, even for once-through cooling water uses because the
water is typically discharged
to a surface water and not
back to the original aquifer. It
also pertains to surface water
sources where water is
consumed, as through
evaporation in cooling towers
or in the production
operations of an industry. For
industries with little water
consumption, such as those
that use water primarily for
washing operations, the
benefits of replacing a surface
water source with recycled
wastewater will be casespecific.
Surface water
Non-Crop Special Temp. Water
Irrig.
Level
Maint.
Water
Utility
Ground
Water
sources could have quantity limitations that would require use of an alternative supply, particularly if the
discharge of the water is not in proximity to the withdrawal or to a different watershed. To focus on water
uses with the greatest benefit to Minnesota’s water resources, this study evaluated industrial water
demand without power generation facilities and in more detail for ground water uses.
The analysis of annual water use indicates that the various types of industrial water use represent a major
component of the state’s overall water use. Recycled wastewater could potentially be used by power
generation facilities using ground water or recirculating cooling water systems (which consume water)
and a variety of industries represented by the industrial processing category in the MDNR water use
database. Some industries also use municipal potable supplies. The potable water supply used by
industries was not assessed in detail for this study. It varies considerably from community to community,
but on a regional or state-basis is estimated to be 10-20% of the potable water demand.
Metropolitan Council Environmental Services 5