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Dr Sarah Ward
Rainwater harvesting –
challenges & opportunities aka
“thinking outside the tank”
Universidad Industrial de Santander, Bucaramanga, Colombia, 12—10-2017
What is rainwater harvesting (RWH)?
Where does the RWH niche fit in the water landscape?
– technological innovation system
You are here
From a slide I presented in London in 2011… (http://slideplayer.com/slide/7323685/)
Challenges
• Conflicting Messages
• Unclear Guidance
• Energy Consumption in Context
• Uncertainty on scale and skill
Opportunities
• Assessing Receptivity/Acceptability
• Perceptions of Health and Safety
• Evidence for Water Saving Efficiency
Moving towards ‘Safe & SuRe’ RWH
Threat
SystemConsequences
Impact
Learn Mitigate
Cope Adapt
What do we mean by ‘Safe & SuRe’?Safe ≈≈≈≈ Reliable - “the degree to
which the system minimises
level of service failure
frequency over its design life
when subject to standard
loading”:
Rel = min (failure: probability)
Sustainable (Su) - “the degree
to which the system maintains levels of service in the long-
term whilst maximising social, economic and environmental
goals”:
Sus = max (capital: social, economic, environmental)
Resilient (Re) - “the degree to which the system minimises
level of service failure magnitude and duration over its
design life when subject to exceptional conditions”:
Res = min (failure: magnitude, duration)
“Individual systems of
provision, such as
water infrastructure
and water resources”
“The degree of non-compliance with
the defined level of service”
“Efforts to increase system
reliability and resilience”
“Better protected or
prepared”
“Any outcomes and effects of the impacts
(i.e. non-compliance with a level of service)
on each pillar of sustainability”
“Any event with the potential to reduce the degree to which the
system delivers a defined level of service”
“Embedding experiences and new
knowledge in best practice”“Reducing the threat”
Interventions
e.g. RWH
Opportunity: making RWH reliable
Verify performance against a required level of service
(India)
Design for it (prevention)
Treat it (cure)
Opportunity: making RWH reliable
Exeter
Inlet (no/ml) Tank (no/ml) Outlet (no/ml)
PCV Range Mean Std.
Dev.
Range Mean Std.
Dev.
Range Mean Std.
Dev.
Coliform 0 0-510 185 203 N/A 0 N/A N/A 0 N/A
E. coli 0 0-210 57 75 N/A 0 N/A N/A 0 N/A
Enterococci 0 0-900 229 309 N/A 0 N/A N/A 0 N/A
P. aeruginosa confirmed
(presumptive)N/A 0-1 (0-1000) N/A
(264)
N/A
(352)
0 (0-
110)
N/A
(18)
N/A
(41)
0 (0-
1000)
N/A
(287)
N/A
(487)
Ward et al (In preparation)
Multi-scale performance of
an off-grid water treatment
device. TBC
Full removal of pathogens
(where source water is selected carefully)
Opportunity: assessing environmental impact
of RWH technologies
Challenge: reducing that environmental impact
Figure 4. Relative LCIA results for 1 m3
of potable water from centralized
supply and the decentralized RHW
RainSafe system under different UK
electricity supply scenarios (the option
with the highest impact in each
category is shown as 100%)
Challenge: tackling the tech – ‘old’ systems
• Mostly German
tech – does it
really fit the UK?
• Designed to
maximise water
saving – what
about other
threats/failure
states/impacts?
Opportunity: new systems & business models
¨Smart¨ RWH
Mitigate
Adapt
“Efforts to increase system
reliability and resilience”
“Reducing the threat”
Threat: population growth
Failure mode: demand increase
Impact: supply deficit
Adapt: RWH to increase potable
water saving efficiency
Threat: climate change (averages)
Mitigate: RWH systems with lower operational
energy to reduce CO2 emissions & lessen CC
Threat: urban creep
Failure mode: increased runoff to sewer
Impact: flooding (pluvial or sewer)
(Mitigate: install permeable paving/enforce planning controls)
Adapt: install RWH (or PP) to reduce stormwater flow
Threat: climate change (extremes)
Failure mode: CSO spill
Impact: point-source pollution
Adapt: RWH to minimise sewer
discharge (frequency & volume)
Opportunity: making RWH resilient, sustainable
Challenge: getting decision makers to adopt these indicators
Driver Target
D1 Capital cost of system T1 Minimize capital cost of RWH system
D2 Water Efficiency T2 Maximize water saving efficiency of system
D3 Reduction in operational energy
consumption for rainwater supply
T3 Minimize energy used to supply water
D4 Reduction in stormwater flow T4 Minimize discharge (rate and volume) of
rainwater during storms
D5 Reduction in combined sewer
overflow
T5 Minimize discharge (frequency and volume)
of sewer network spills downstream of the site
Challenge and opportunity: multi-objective
assessment of new systems
Challenge: getting decision makers to adopt these indicators
http://www.rainwaterharvesting.co.uk/downloads/brochures/rain-activ-brochure.pdf
http://www.waterpoweredtechnologies.com/page.php?id=20
http://www.flushrain.co.uk/
Re-designing assessment
of new systems
Identifying
RWH systems
in this space
Challenge: assessing all systems
Challenge: getting new RWH
configurations into the market
Opportunity: assessing the UK RWH niche/network
Social network analysis
UK RWH niche – what are the strong points?
Influence range closeness centrality (IRCC)
hierarchy for the rainwater harvesting network
• Strong technology:
RWH innovators
• Strong networks &
forums
• Plenty of innovation
without financial
incentive (e.g. from
Government)
• Rise to challenge of
meeting SuRe drivers
(low energy,
maintenance etc)
CWS
UKRMA
RWH niche – what are the weak points?
• Small, dense, disconnected from the “bigger picture”
• Heavy bias of RWH innovators & overlapping networks
• Innovation in isolation – not priority for policy/decision
makers
• Policy makers are poorly represented
• Policy makers focus on evidence of meeting
(undefined) drivers e.g. energy consumption (no target)
• End-users are not represented
• Few social enterprises
Opportunity: niche governance (i.e. not management)
Respond to
regime
sust’y aims
Tech, soc
& service
innovation
Dynamic &
reflexive
learning
Persuasive &
influential
intermediaries
No
protected
spacesNetwork
with/out
converged
expectations
Polycentric
governance –
including end-
users
Rainwater
Users Forum?
Critical analysis & reflection on a
range of data sources/knowledges
led to definition of 7 niche
governance categories:
Opportunity: include end users…look at the tank from both sides
• Co-create evidence (e.g.
performance data, energy
consumption, cost-benefit)
• Critically evaluate all RWH
configurations/enterprises
Grupo de Investigación en Recursos Hídricos y
Saneamiento Ambiental:
End-User Cost-Benefit Prioritization for
Selecting Rainwater Harvesting and Greywater
Reuse in Social Housing
Isabel Domínguez, Sarah Ward, Jose Gabriel
Mendoza, Carlos Iván Rincón & Edgar Ricardo
Oviedo-Ocaña
Financial feasibility of end-user designed
rainwater harvesting and greywater reuse
systems for high water use households
Edgar Ricardo Oviedo-Ocana, Isabel
Dominguez, Sarah Ward, Miryam Lizeth Rivera-
Sanchez & Julian Mauricio Zaraza-Pena
Ongoing work by GPH at
different building scales
Opportunity: community/social enterprise
What happens elsewhere?
Mexico
• Connecting people with too much
runoff with those who need more!
• Including the end-user - making
space for people
• Reconnecting people with water –
giving back ownership
• Helping communities
grow/wash/flush (swapping non-
potable for potable)
• Keeping rainwater out of
sewers/slow its entry to sewers (local
source control)
rainshare.co.uk
Changing the world, one roof at a time……
What’s happening in
the UK?
in action……
rainshare.co.uk
http://waterenergynexus.co.uk/rainshare/
Need more RainSharers!
= distributed communal harvested rainwater storage
Project A – Commercial - Residential
Exploring other potential projects
Project B - Residential/domestic
Project C – Urban Greening
Taxi firm washing 3 cars, 2-3 times/week
Reflecting on where we are with the challengesWe can:
• Size & design tanks using a number of methods
• Verify performance to specified levels of service (e.g.
demand requirements, water quality standards)
• Reduce threats (e.g. energy use/carbon emissions)
• Reduce (negative) consequences (e.g. lower capital cost)
• Increase (positive) consequences (e.g. higher water
saving efficiency; end-user participation)
• Contribute to stormflow reduction (helping adapt the
drainage system to extreme conditions)
• But we must do it across international case
studies & there are many more things to do…
What next?
“We are often water-short when demand is greatest.
And now our climate is changing. What are the
implications and opportunities for rainwater
harvesting as a source of water for potable and non-
potable uses?"Kim Stephens, Partnership Executive Director
(Tracking Adaptation & Measuring Development (TAMD))
• Multi-objective, reliable, resilient,
sustainable RWH for all?
• Combining technical & social innovation
• For non-UK contexts finding out the ‘how’
• Much more research going on in this area
References for work shown in this presentation can be found at:
http://emps.exeter.ac.uk/engineering/staff/sw278/publications
Thank you
¿Preguntas?
¿como es en colombia?
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