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Perspectives on Rainwater Harvesting: Perspectives on Rainwater Harvesting:
Past, Present and FuturePast, Present and Future
David ButlerDavid Butler
Professor and Director, Professor and Director,
Centre for Water SystemsCentre for Water Systems
University of Exeter, UKUniversity of Exeter, UK
The Future of Rainwater Harvesting in BuildingsThe Future of Rainwater Harvesting in Buildings
University of Exeter, 21University of Exeter, 21stst January 2011January 2011
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• Past
• Present
• Future
• What needs to be done?
• Conclusions
OutlineOutline
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PastPast
• By no means a modern concept!
• Simple concept
• Systems found in:
– Israel, Africa, India, 2000BC
– Mediterranean area, 1700BC
– Petra, Jordan
• Decline of systems
• Uses of collected rainwater
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PastPast
Rain was an important source of water in the ancient trading city of Petra,
Jordan, which supported a population of 20,000 in a place where just 150
mm of rain fell a year.
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• Present day RWH remains a simple concept
• System Components
– Catchment
– Collection system (First flush diverter)
– Treatment
– Storage
– Pump
PresentPresent
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PresentPresent
Indirectly pumped
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Directly Pumped
OVERFLOW
100%
FILTER/SCREEN
PUMP
SEWER
SUPPLY
PresentPresent
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PresentPresent
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PresentPresent
BedZed, LondonBedZed, London
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• Benefits:– Saves potable water (by displacing non-
potable water use)
– Saves energy/carbon (at least that associated with the displaced water)
– Reduces flood risk (especially summer storms & can be enhanced by better design)
– Reduces load on regional water resources and central water infrastructure (and potentially delays/limits expansion)
PresentPresent
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Saves potable water (by displacing non-potable water use)
PresentPresent
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Reduces flood risk (especially summer storms & can be enhanced by better design)
PresentPresent
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• Drawbacks:– Requires maintenance (to ensure reliability)
– Requires energy/carbon to operate (at least most current systems) and construct
– Has potential water quality issues (although these are minimised by careful design/installation)
– Payback period depends on scale of provision (shorter in bigger buildings)
– Users/specifiers may be unfamiliar
PresentPresent
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Gravity Feed Systems
C I S T E R N
C R O S S F L O W
F I L T E R
M A IN S T O P U P
O V E R F L O W
S U P P L Y
S E W E R /D R A IN
FutureFuture
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FutureFuture
Rainwaterhogs are modular, DIY, expandable, reusable, and
recycled storage units that can be connected to create a custom
system placed at several different locations throughout the property.
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FutureFuture
Dwr Cymru/Welsh Water, consultants MWH and manufacturer
Aqualogic are working to produce affordable wall-mounted rainwater
harvesting systems
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To supply
(WCs)
90-120L
• Rainsense is a prototype, patented system that uses tiled gullies to
collect runoff part way down the roof and stores the rainwater in modular,
storage tanks in the eaves space – then supplies the harvested rainwater
via gravity
FutureFuture
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FutureFuture
The CISTA rainwater harvesting system provides storage for rainwater
within a vertical planted frame, allowing conservation of water and
increased green space.
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FutureFuture
BabyGROW is a prototype planted water recycling system
for collection & treatment of grey and/or rainwater to improve
water quality and provide increased green space
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FutureFuture
Personal rain saver?
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What needs to be done?What needs to be done?
• New RWH designs, especially
for domestic dwellings. Need to:
– be easily retrofitable
– make better use of space for water
storage
– reduce or eliminate the need for
fossil-derived energy for pumping
– be reliable, easy to use and
maintain.
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What needs to be done?What needs to be done?
• New RWH designs need to be
multi-functional to:
– supply in-building water needs
– provide flood protection
– improve water quality
– provide a greener environment and
– use less embedded carbon.
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What needs to be done?What needs to be done?
• New business models:
– consider system leases from a
supplier or water company
– mitigates the capital cost to user
– saves money for the householder
– ensures regular maintenance
– provides a profit opportunity for
the provider.
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What needs to be done?What needs to be done?
• Improved governance of
emerging approaches at
institutional level:
– to help lead the way forward
– to integrate them into everyday
thinking
– by providing authoritative advice
and leadership.
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What needs to be done?What needs to be done?
• Increased public awareness
and acceptability by:
– Better best practice guidance
– Incentives and grants
– Exemplars of successful
approaches
– Identification of ‘trusted’ sources.
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ConclusionsConclusions
• RWH systems are currently appropriate and viable at large building scale
• New RWH technologies are emerging for retrofit in domestic dwellings where there is greatest need and potential benefit
• Creativity and commitment needed on ownership and reliability.
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Perspectives on Rainwater Harvesting: Perspectives on Rainwater Harvesting:
Past, Present and FuturePast, Present and Future
David ButlerDavid Butler
[email protected]@exeter.ac.uk
The Future of Rainwater Harvesting in BuildingsThe Future of Rainwater Harvesting in Buildings
University of Exeter, 21University of Exeter, 21stst January 2011January 2011
Thanks to Alan Fewkes & Sarah Ward for some of
the slides used in this presentation