Robert Pi*, Emeritus Cudworth Professor of Urban Water Systems, University of Alabama And other commi*ee members

Transcription

1 Robert Pi*, Emeritus Cudworth Professor of Urban Water Systems, University of Alabama And other commi*ee members

2 Study Task 1. Quan'ty and suitability. What is the potencal to significantly increase stormwater and graywater use in the U.S., and where would increases have the most benefit? 2. Treatment and storage. What types of treatment are available and how do these treatment methods compare in terms of cost and energy use? 2

3 Study Task (cont.) 3. Risks. What are the human health and environmental risks for various uses? 4. Costs and benefits. What are the costs and benefits of the beneficial use of stormwater and graywater (including non- moneczed costs and benefits)? 5. Implementa'on. What are the legal and regulatory constraints for use of captured stormwater and graywater? Related to 1-5, what research is needed? 3

4 9 Sponsors EPA (OW, ORD, Region 9) NaConal Academies Presidents Fund NaConal Science FoundaCon Water Research FoundaCon Water Environment Research FoundaCon Los Angeles Department of Water and Power City of Madison, Wisconsin WateReuse NaConal Water Research InsCtute (NWRI) 4

5 CommiAee Members RICHARD LUTHY, Chair, Stanford University RICHARD ATWATER, Southern California Water Commi*ee GLEN DAIGGER, University of Michigan (formerly CH 2 M- Hill) JÖRG DREWES, Technische Universität München, Germany BENJAMIN GRUMBLES, Maryland Dept. of the Environment ARPAD HORVATH, University of California, Berkeley ROBERT PITT, University of Alabama MARCUS QUIGLEY, OpCRTC, Boston ROBERT RAUCHER, Stratus ConsulCng/Abt Associates SYBIL SHARVELLE, Colorado State University CLAIRE WELTY, University of Maryland BalCmore County MARYLYNN YATES, University of California, Riverside Commi*ee held 6 meecngs starcng in Nov. 2013; authored consensus report. 5

6 Original Analysis of PotenCal Savings Analysis of residencal stormwater and graywater use: 100 acres, 12 persons per acre Site- specific data: LA, Sea*le, Madison, Lincoln, Newark, & Birmingham rainfall, long- term ET to escmate monthly irrigacon needs Graywater assumed U.S. average graywater daily supply Scenarios considered: Graywater: whole house and laundry to landscape (irrigacon only) Stormwater: roof runoff in 2 rain barrels (70 gal total) or 2,200 gal tank Calculated potencal savings for: ConservaCon irrigacon (barely meet ET) for turfgrass Toilet flushing IrrigaCon and toilet flushing 6

7 7 PotenCal Household Graywater Savings

8 Roogop Capture: PotenCal Savings with 2 Rain Barrels per House 8

9 Roogop Capture: PotenCal Savings using 2,200 Gal Tank per House 9

10 Water Availability Stormwater: Dependent on tank size and amount/cming of precipitacon relacve to demand Neighborhood and regional- scale projects can contribute significantly to urban water supplies Graywater: SubstanCal potencal savings, parccularly useful in arid regions If water conserva6on is the objec6ve, strategies to reduce outdoor water use should first be examined. 10

11 Original Analysis of PotenCal Savings 11 Blue=rainfall; red=irrigacon demand to barely meet ET

12 Maximum Water use by Plants and Soil Moisture Deficit Plots Showing Maximum Irriga'on Possible without Harming Plants (scenario to decrease stormwater of CSO discharges)

13 8,000 20,000 Annual Water Savings ([3/ac/yr) 7,000 6,000 5,000 4,000 3,000 2,000 1, SW MDR annual water savings (ET) (g3/ac/yr) SW MDR annual water savings (max irrig) (g3/ac/yr) Annual Water Savings ([3/ac/yr) 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2, Tank Storage ([3/[2 roof area) CEN MDR Commercial annual water savings (ET) (g3/ ac/yr) CEN MDR Commercial annual water savings (max irrig) (g3/ac/yr) Tank Storage ([3/[2 roof area) 25,000 Annual Water Savings ([3/ac/yr) 20,000 15,000 10,000 5, EC MDR annual water savings (ET) (g3/ac/yr) EC MDR annual water savings (max irrig) (g3/ac/yr) Use of roof runoff at medium density residencal areas for irrigacon for different sized storage tanks and US locacons. Tank Storage ([3/[2 roof area)

14 Storage Tank Sizes for Different Ranges of Captured Runoff storage tank volume ([ 3 ) Approximate runoff removal range (% of long- term runoff for 1,000 [ 2 impervious area at six US regions) number of 35 gal rain barrels per 1,000 [ 2 impervious area number of 5 [ D, 5 [ tall tanks (730 gallons; 98 [ 3 ) per 1,000 [ 2 impervious area number of 10 [ D, 10 [ tall tanks (5,900 gallons; 785 [ 3 ) per 1,000 [ 2 impervious area to to to to to ,

15 Percola'on of Stormwater for Later use Source: SCWC Stormwater White Paper

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18 Urban Stormwater Capture & Recharge Future distributed capture Future centralized capture Baseline Incidental recharge Exis'ng spreading LA s stormwater capture master plan an aggressive path this century could add nearly 200,000 afy from today s baseline (SWCMP, 2015) 18

19 Stormwater : Water Quality Highly variable over space and Cme, although related to land use Li*le is known regarding human pathogens and organic chemicals in stormwater, addiconal research is needed Graywater: Pathogens & organic ma*er necessitate treatment for uses with human contact 19

20 Risk Risk assessment provides a means to determine fit- for- purpose criteria or treatment needs based on exposures Pathogens: the most significant acute risks Extremely limited data, which precludes a full assessment of risk, parccularly for roof runoff. Stormwater recharge poses risks of groundwater contaminacon and necessitates careful design to minimize those risks 20

21 State of PracCce: OperaCons OperaCons and maintenance of household and neighborhood graywater and stormwater use systems is not well guided or monitored. Many states require that systems meet water quality targets, but ongoing monitoring is not required. Online monitoring of surrogate parameters (e.g., on- line residual chlorine, turbidity) should be considered. 21

22 Costs and Benefits It is important to recognize the full suite of benefits as well as the full costs of graywater and stormwater projects, although it may be challenging to do so. Financial cost data are extremely limited Social & environmental costs and benefits rarely moneczed Energy savings are possible, but data for a sound assessment are lacking. 22

23 Costs and Benefits Simple systems can offer reasonable financial payback periods under certain scenarios/climates. However, behavioral factors on water use are poorly understood Economies of scale are evident Total Lifecycle Cost ($/AF) 23

24 Risk and water quality Research Needs 1. Assess the occurrence and fate of pathogens in graywater and stormwater 2. Assess the occurrence and fate of chemical contaminants in stormwater 3. Understand the implicacons of enhanced water conservacon on graywater quality and use 4. Develop risk- based water quality guidance for various uses that could serve as a basis to develop standards of praccce 5. Develop monitoring technology and strategies to assure compliance with water quality criteria 24

25 Research Needs Treatment technology 6. Develop treatment systems to meet tailored (fit- for- purpose) water quality objeccves across a range of scales 7. Understand the long- term performance and reliability of graywater and stormwater treatment systems (from small to large scales) Infrastructure 8. Envision opportunices for water- and energy- conserving infrastructure designs in new construccon and demonstrate performance 9. IdenCfy strategies to retrofit exiscng infrastructure for enhanced beneficial use of stormwater 25

26 Social science and decision analysis Research Needs 10. Understand behavioral impacts on overall water use in the context of graywater and stormwater projects 11. Collect performance data (e.g., cost, energy, water savings, water quality, and other benefits) in support of integrated water supply management, decision making, and refinement of decision tools Policy and regulatory issues 12. IdenCfy incencves and various regulatory strategies that have proven effeccve in the implementacon of stormwater or graywater systems to conserve water supplies 26

27 Summary Graywater and stormwater capture and use can expand local water availability while providing addiconal benefits. Treatment can help address contaminants in the water, but a lack of risk- based treatment guidelines hinders the broader use of stormwater and graywater. There is no single best way to use graywater or stormwater to address local water needs many important consideracons including legal and regulatory constraints, potencal applicacons, climate, and source water availability vary widely with local condicons. Research on informacon about costs, benefits, risks, treatment needs, and behavioral factors would enhance decision making. 27

28 More Resources Full report at h*p:// AddiConal resources under Resources tab: 4- page report in brief Press release 28