water conservation: a cohesive approach...dsb_2_water_081014 3 end use and the water-energy...

DSB_2_Water_081014 1

Water Conservation: A Cohesive ApproachWATER CONSERVATION SHOWCASE, 2009

Kirstin Weeks, Energy and Building Ecology Specialist

Contents

• Background

• Design Approach

• Project Examples


Background

Water stress index (WSI)

Local water shortages due to development in dry areas, increasing demand, sociopolitical factors, annual weather variability and climate change create a challenging situation.

Pink areas are currently using 75% or more of their available water resources.

Background


End use and the Water-Energy Connection

U.S. Water Use, 2000 (USGS)

Energy Production

47%

Agriculture/Irrigation

34%

Other3%

Domestic Use11%

Industry5%

US Commercial buildings consume approximately 11% of total water supply (but a higher % of treated potable). Note that energy production consumes almost four times that amount. Thus, buildings that save energy also save water.

Background

0

100

200

300

400

500

600

700

gallons/day

Thermoelectric Hydroelectric

Energy Source

Residential Water Uses (2 person household)

Other off-siteEnergy GenerationOutdoor UsesIndoor Uses

Why does energy production consume water?

Evaporation!• Cooling towers in gas, coal

and nuclear plants

• Large dam reservoirs in hydroelectric plants

Lake Mead, Hoover Dam, NVCooling Towers, Cofrentes Nuclear Power Plant

Water use in power production, NREL 2003

Background


Why does water supply consume energy?Pumps are energy intensive

• Extraction (groundwater) pumps

• Distribution pumps

Treatment has impacts

• Energy

• Chemicals

• Land use

• Construction of Infrastructure also requires energy

The US water supply consumes roughly 75 billion kWh/yr (3% of national usage), roughly equal to California’s entire residential electricity demand

Background

Embodied energy in waterOffsite energy in water consumed in a typical Southern California household is equivalent to 1/3 of household energy demands

150 8900 kWh/MG

2.5 kWh/MG

1 MGD = 12.7 MWh in Southern California= 4.0 MWh in Northern California

100 kWh/MG

1200 kWh/MG n.a.

Can water efficiency be a more effective energy and carbon strategythan traditional energy efficiency and renewable energy technologies?

Source:


Energy Intensity of Water Sources in San Diego, CA

Source: Pacific Institute, Wolff et al., 2004

Background

Design Approach


Goals for buildings and sites• Reduce the environmental impacts associated with water use

• Minimize strain on the local water supply and sewer system

• Provide good stewardship of stormwater

Design Approach

Appropriate Baselining

Potable Water Demand Reduction

3.01

1.771.84

2.22

1.421.24

0.95

1.93

1.02

2.53

0.81

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Pota

ble

Wat

er D

eman

d (M

GD

)

BAU Historical Benchmark BAU Updated Plumbing Code Sustainable Development

Climate Appropriate Planting

Mechanical efficiencyRecycled Water for Public Space Irrigation

Efficient Fixtures

Recycled Water for interior use(non-residential)

Internal and External Leakage Reduction

Recycled Water for exterior use (non-residential)

Historical Benchmark BAU Demand

Adjusted to Codes BAU Demand

Recycled Water for interior use(residential: toilet fllushing may be permitted in some instances)

Recycled water for exterior use (residential)

Sustainable Case Demand = 1.72 MGDAfter Recycling Demand = 0.92 MGD

16% reduction

25% reduction

27% reduction

Adjust to Code

Efficiency

AlternativeSupply


Approach to Water MinimizationDesign Strategies

Fixture water Efficiency• Use lowest flow (gpm) available for faucets• Use waterless urinals where allowed by code• Use dual flush toilets or, where feasible,

composting/foam flush toilets*

Design Strategies


Site Water Efficiency• Use native and adapted plants, which require

little or no irrigation

• Irrigation technology• Use ET Controllers to allow irrigation

system to provide only what water is needed based on evapotranspiration

• Use drip irrigation rather than spray systems

• Irrigate at night to reduce evaporative losses

Mechanical Water Efficiency

• First, save energy! Cooling load especially…

• Use non-chemical treatment regimes in cooling towers that reduce necessary blowdown volume


Low-Impact Sources

• Sources with lowest embodied energy and other environmental impacts

• Often (but not always) includes• Rainwater harvesting• Municipal recycled water• Air conditioner condensate• Local surface water

Photo credits: Buildinggreen.com and www.ci.clovis.ca.gov

Code considerationsDesign Strategies

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Moderate-Impact Sources• Sources requiring slightly higher energy/chemical

inputs or carrying other impacts

• Often (but not always) includes:• Grey water• Cooling tower blowdown• Groundwater

• Determine water demands and available water sources

• Assess flow balance within building’s “watershed”• Match sources by volume and treatment needs

• Potable: faucets, showers

• Nonpotable with minor human contact: spray irrigation, toilet flushing, cooling towers

• Nonpotable with no human contact: subsurface irrigation

Strategy for Applying Nonpotable SourcesDesign Strategies

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Matching sources with uses

No treatment needed

Minimal treatment needed

Intensive treatment needed

Design Strategies

What’s Left?

• If demand remains, must be met by higher-impact sources

• Often (but not always) includes• Municipal potable supply• Treated blackwater• Desalinated water

• Marin County Example

• Orange County & Las Vegas Examples

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Offsets and Offsite Water Use Reduction• Funding offsite water reduction as a means of

offsetting use onsite or making a building “potable water positive”

• Sometimes more cost-effective than avoiding 100% of potable use onsite

• Coca cola claims 100% water offsets through World Wildlife Fund (WWF) – restoration focused

• Some water-challenged municipalities are requiring that all new developments carry out water offsets by funding retrofits to the community’s existing buildings

• Can also include saving energy and accounting for embedded water

Case Studies

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California Academy of Sciences

Water Conservation Components• Low-flow fixtures

• Faucets• Toilets• Urinals

• Dual plumbing of all nonpotable uses for future municipal recycled water

• All irrigation• All flushing

• Also: reduced stormwater volume from roof flows to infiltration cisterns

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Water Achievements

• LEED Platinum – achieved all 5 Water Efficiency credits and all 14 Sustainable Sites credits

• ~85% potable water reduction compared to baseline once purple pipe is charged

Stanford: Y2E2 & Graduate School of Business (GSB)

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Y2E2• Recycled water from cooling towers at Central Energy Facility

is used for toilet flushing

• 30% water savings

• Lakewater is also used

• Annual savings are estimated at $2 million, paying back in 13 years.

System Examples

GSB

•Water supply/demand balance

•CEF water for non-potable uses

•Rainwater stored and treated onsite

•Estimated 70% water savings

System Examples

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South Bay Confidential Office Project

• “Max Green” mandate from client

• Office space, fitness center, kitchens & cafes

• Green roofs, landscape

• Municipal recycled water “to be available”

Annual Demand Trends

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

Jan

Feb Mar AprMay Ju

n Jul

Aug Sep Oct Nov Dec

Fixtures

Kitchens

Flushing

Cooling Tower Make-up

Irrigation

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Annual Supply Trends

0

50,000

100,000

150,000

200,000

250,000

300,000

Jan

Feb

Mar

Apr

May Ju

n

Jul

Aug

Sep Oct

Nov

Dec

RainwaterCooling Tower BlowdownFixture Gray WaterBlackwater

Water Balance

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Components & Expected Performance

• Dual flush toilets, pint urinals, efficient faucets

• Primarily native and adapted planting

• Tank sharing for blowdown and rainwater reduces size

• Potable use reduction: 94% (12.8 million gallons/year)• Site Reduction: 5.1 million gpy• Building Reduction: 2.7 million gpy• Nonpotable supply: 5 million gpy

• Remaining 6% to be offset via community program

• Next Step: Energy and material analysis to determine whether onsite reuse provides enough benefit over municipal recycled to justify investment.

Angwin EcoVillage, Pacific Union College

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Water and Wastewater

Components• Water efficient fixtures and irrigation systems• Rainwater harvesting and reuse• Improve existing sewage treatment facility for the new

development to tertiary level• Reuse 100% of wastewater for irrigation including

campus facilities

Performance Targets• Ecovillage to use 50% less water than EPA standards• No more groundwater draw than Pacific Union has

historically used; no water use from existing water districts

Water Supply – Development Baseline

Development Baseline Water Supply Analysis

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000

35,000,000

40,000,000

45,000,000

Janu

ary

Februa

ryMar

chApri

lMay

June Ju

ly

Augus

t

Septem

ber

Octobe

r

Novem

ber

Decem

ber

Wat

er U

se (g

allo

ns p

er m

onth

) Groundwater for Irrigation

Stored Rainwater

Springwater

Stored and TreatedWastewater

Reservoir Rainwater

Groundwater for PotableUse

Peak Potable Water Demand in the Summer

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Water Supply – Angwin Ecovillage

Year Round Use Water Supply Analysis

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000

35,000,000

40,000,000

45,000,000

Janu

ary

Februa

ryMarc

hApri

lMay

June Ju

ly

Augus

t

Septem

ber

Octobe

r

Novembe

r

Decembe

r

Wat

er U

se (g

allo

ns p

er m

onth

) Groundwater forIrrigation

Stored Rainwater

Springwater

Stored and TreatedWastewater

Reservoir Rainwater

Groundwater forPotable Use

Potable Water Only needed during the Peak Summer Season

Water Supply Summary

Water Supply Scenarios

0

50,000,000

100,000,000

150,000,000

200,000,000

250,000,000

300,000,000

Existing Baseline Development Baseline Year Round Use

Ann

ual W

ater

Use

(gal

lons

Alternative WaterSource for Irrigation

Groundwater forIrrigation

Groundwater forPotable Use

Analysis Shows that Groundwater Consumption can Decrease

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Qingdao Ecoblock: Closing the water/energy loopSystem Examples

Thank You!

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Beyond Conservation: Ecological Stormwater Management

Stormwater runoff implications

• Infrastructure capacity constraints

• Prevention of groundwater recharge

• Pollutants from roads, ground carried to surface water bodies

• Combined sewer overflow (CSO) in urban areas means excess stormwater runoff can cause sewage spills (San Francisco and Sacramento have combined sewer systems)

• Hydromodification alters the existing watershed regime, promotes soil erosion and influences downstream ecosystems

Beyond the Building

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• Pre-development hydrological conditions should be restored to the extent possible.

• Stormwater should be retained, cleansed and infiltrated onsite as much as possible.

• Arup value-added approach:

“Integrate stormwater facilities into the site plans to create multi-use features, e.g. wet pond is an amenity and adds value to adjacent properties, floodable park area for seasonal storage is usable all year and saves land.”

Stormwater GoalsBeyond the Building

Strategies Include

• Rainwater collection

• Permeable pavement

• Bioswales

• Green roofs

Beyond the Building

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Case Study: Bay MeadowsBeyond the Building

(Courtesy of CMG)

Case Study: Bay Meadows

Comprehensive 3 tiered approach• Pond, streetscape planters, parcel

BMP’s

Triple bottom line of sustainability –environment, society and the economy

• Efficient stormwater management system

Early planning and collaboration to reduce necessary infrastructure

• Designed within site constraints• Coordination with public agencies to

gain approval• Appreciative client (Courtesy of CMG)

Conclusion

Beyond the Building

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Appendix: Definitions (part I)• Potable water: water that is safe for drinking and showering, generally supplied by cities

• Non-potable water: water that is unsafe for drinking but may be appropriate for other uses in buildings, such as irrigation or toilet flushing.

• Greywater (aka gray water): non-potable water from sinks and showers, not containing sewage or water from kitchen sinks.

• Blackwater: water that contains sewage from toilet flushing.

• Reclaimed water: wastewater treated to tertiary level, usually by a municipality, then distributed separate from potable water for non-potable uses (usually via purple pipe to distinguish from other pipes).

• Recycled water: generally, this is defined as reclaimed water.

• Mechanical process water:

• Cooling tower blowdown: non-potable water released from water-based cooling systems, usually at roof level. Can be treated and reused (easier if a non-chemical treatment regime is employed), but generally contains elevated levels of salt and minerals.

• Air conditioner condensate: water condensing around cooling coils due to temperature differential. Considered non-potable, but generally of very high purity.

Design Approach

Appendix: Definitions (part II)• Reverse osmosis: a technique for producing potable quality water from seawater

(desalination) or other contaminated water.

• Disinfection: eliminating bacteria and other microbes from water. Can be accomplished using UV light, chlorine compounds or ozone.

• Tertiary level: wastewater undergoes primary, secondary and tertiary treatment, after which it is safe for non-potable uses with some human contact.

• Advanced treatment: refers here to methods for achieving potable quality from a previously non-potable source. Reverse osmosis and UV filtration are often used.

• Combined sewer overflow (CSO): in cities with combined sanitary and storm piping, this is an event in which stormwater mixes with sewage and overflows untreated or partially treated into surface water due to insufficient treatment capacity.

Design Approach

water conservation: a cohesive approach...dsb_2_water_081014 3 end use and the water-energy...

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