October 2012
A-23
A.8 University Makes the Most of Onsite Alternative Water Sources
At one point, UT Austin maintained nearly 250 pieces of equipment connected to
the recovery system. Over time, UT Austin has replaced some of the older single-pass
cooling equipment with more efficient, air-cooled equipment to eliminate some
unnecessary water use, including replacing the old drinking fountain chillers with
air-cooled heat exchangers.
GroundWater Sump Recovery
Some buildings on campus sit two or three stories
below ground level and, as a result, ground water
must be removed from these foundations to prevent
building flooding. Before the mid-1980s, all of the
recovered foundation ground water was pumped to
the storm sewer. However, UT Austin saw this as an
opportunity to use water that otherwise would go
down the drain, as long as the hard water is treated
prior to use in the cooling towers.
Air Handler Condensate Recovery
In 1985, UT Austin began recovering air handler condensate and using it as make-up
water for the cooling tower. Air handler condensate has relatively low conductivity
and is cold, so it provides a good source of make-up water for the cooling tower. In
addition, it is produced during the hot, humid summer months, when the cooling
towers are running constantly and generate the highest demand for make-up water.
With the use of air handler condensate as make-up water, UT Austin was able to
increase the average cycles of concentration of the cooling tower from five to an
average of nine and a peak of 14 cycles in the hottest summer months. Due to
the success of air handler condensate recovery, UT Austin now constructs all new
buildings with air handler condensate recovery systems. Approximately 40 buildings
recover condensate from 100 air handler units. UT Austin has also been working to
retrofit existing buildings to recover air handler condensate. Because the generation
of single-pass cooling water has diminished due to the installation of air-cooled
equipment, UT Austin now relies primarily on air handler condensate, rainwater
harvesting, and some recovered foundation ground water to provide cooling tower
make-up.
Rainwater Harvesting
Rainwater harvesting has been a relatively new addition
to the UT Austin’s alternative water source repertoire.
Over the last five or six years, all newly constructed
buildings on the campus have been equipped with
rainwater harvesting capability, some with 5,000-gallon
storage tanks, which collect rainwater for lawn irrigation.
The rainwater harvesting system at UT Austin recovers 40
to 50 million gallons of water per year, depending upon
the amount of rainfall.
A chilling stationmaking chilledwater to cool campus buildings
Two 2,500-gallon tanks storing air handler
condensate and harvested rainwater for irrigation
