Session 334 Grant Thornley
Transcript of Session 334 Grant Thornley
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Atlanta Rainwater
Harvesting systemfor Therell High School
Presented by: UV Pure and Rain Harvest Systems (GA)
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Rainwater HarvestingTherell High School
First school in Atlanta, GA to install a
Rainwater Harvesting system
Project objective was to achieve a50% reduction in potable water use
for the flushing of toilets (LEED point WE2 – a water efficiency credit)
This presentation will review thesizing, design and challenges of the
Rainwater Harvesting System
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System Design
Roof Rain Water Drains
80,000 gal
Main Tank
Transfer
Pump
SedimentFilters
Day Tank
500 galUVDisinfection
Booster
Pump
To ToiletsStandby
Potable
Water
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Rain Water Treatment System
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Challenges of the Project
• Limited space within the mechanical room
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Flow would not be constant and UV Systemwould be left on (overheating concern)
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Toilets would be required to be operationalregardless of Rainwater
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Solution
• An 80,000 gal tank for rain water collection
and transfer pump station was installed
• In the mechanical room, a 500 gal day tank
was installed which would act as a buffer and
allow smaller treatment components to be
used
• (2) UV Pure Upstream UV Systems were
installed since they could be left on without
overheating
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Selection of the Components
Day Tank
-Typical sizing of a day tank;
expected occupancy X 3 gal/person
-Since size was a constrain, a 500 gal tank was
used rather than normal sizing
(A day tank allows for lower flow rates and in turn smaller
components)
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Selection of the Components
Sedimentation Filter
-Filters are required to ensure the aesthesis of the
water and proper UV operation.
-Filters were required to be back flushable and
filter down to 5-10 um
-Filters are sized based on a 1-2 hr day tank filltime. For sizing 100 minutes was used
500 gal (day tank)/ 100 minutes = 5 gpm
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Selection of the Components
UV Disinfection
-UV Disinfection is used to deactivate
Viruses and Bacteria Instantaneously
-UV system was sized based on day tank fill time
(same as sediment filter)
-The selected UV system had to be able to not
overheat during no flow conditions and be self
cleaning
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Selection of the Components
Conventional TechnologyCrossfire Technology
The selected UV system located its UV Lamps outside of theprocess stream and had a self cleaning UV reactor
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Results
-50% water reduction was achieved for the
flushing of toilets and earned LEED Credits
-Installation of the day tank allowed for
smaller components to be used, resulting
in a significant cost savings
-The UV system did not overheat duringno-flow conditions, simplifying overall
operations
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Questions