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Water System Design for Stanford University Green Dorm: Progress Report JJC Engineering Consultants Jessica Chong Julia Schmitt Cheng Boon “C-Bo” Yap Stanford.

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Presentation on theme: "Water System Design for Stanford University Green Dorm: Progress Report JJC Engineering Consultants Jessica Chong Julia Schmitt Cheng Boon “C-Bo” Yap Stanford."— Presentation transcript:

1 Water System Design for Stanford University Green Dorm: Progress Report JJC Engineering Consultants Jessica Chong Julia Schmitt Cheng Boon “C-Bo” Yap Stanford University, June 8, 2007

2 Scope of Presentation Introduction to JJC Summary of Approach JJC’s proposed technologies: - Green Roof - Stormwater Management - Ecological Wastewater Treatment Highlights from each research area Integrated research summary

3 Introduction to JJC Passion and Focus: Sustainability -optimize use of resources -non-intrusive - “living” Good fit with the Green Dorm Associates from JJC hard at work

4 Water Balance Administered a 2-week survey (jointly with KJB and LCC) Determine water requirement for the Green Dorm Estimate greywater and blackwater output from the Green Dorm Improve on existing data (e.g. JBM Associates report from 2005)

5 Water Balance Sample of portion of our survey form Duration of shower Duration of faucet use (washing face, brushing teeth, etc) Duration of Drinking Fountain Use Number of Toilet Flushes (include if you flush twice) Duration of Dish RinsingOther Example 15 min4 min2 min41 min Wednesday2-May Thursday3-May # in-dorm toilet flushes: ~= 7 Loads of laundry per week ~= 1

6 Water Balance ItemDemand (gal/day)Demand (gal/month) Dish Washing Domestic Cleaning Leaks Faucet - Kitchen Faucet - Bathroom Shower Laundry Toilet Flushing Hobart (sanitizing) Irrigation Total~2300~69000 Greywater sources: Domestic Cleaning, Bathroom Faucet, Shower, Laundry (~ 28,500 gallons total) Blackwater sources: Dishwashing, Kitchen Faucet, Toilet Flushing, Hobart (~ 30,000 gallons total)

7 Proposed Target Consider California Title-22 Domestic house cleaning, irrigation, toilet flushing and laundry Total demand of about 25,000 gallons per month

8 Roof: Rainwater Harvesting Harvest rainwater - why? –Optimize use of natural resources reuse collected/treated water for potable uses reduce demand for potable supply close the water loop –Minimize environmental impacts reduce erosion & flooding of surrounding areas reduce runoff to sewer system Meet laundry and domestic cleaning demands of 150 gal/day

9 Roof: Rainwater Harvesting Identified problem: accumulation of debris on roof First Flush Diverter: diverts first flow of water away from storage tank Routed into lab for student research –What is on the roof? adjustable pipe lengths for chamber –Runoff quality comparisons: green roof vs. photovoltaic vs. conventional roof Initial runoff vs. storage tank vs. post- treatment Source: The Texas Water Development Board

10 Roof: Rainwater Harvesting Gutter & downspout specifications (for 10-year storm) Catchment area for each gutter section: 400 ft 2 –Spaced 20 feet apart –Requires 4-8 gallons diverted Semicircular cross section gutters: –Top width: 1.0 feet –Height: 0.5 feet

11 Roof: Rainwater Harvesting parameters: -average precipitation -runoff coefficient = 0.75 Specifications Two 15,000 gal underground cisterns Material: ferrocement Integrated into dorm design

12 Treating Rainwater –No rainwater use regulations –Used for drinking water in two State Guidelines/Manual publications –Also used for greywater treatment, stored in Greenhouse Roof: Rainwater Harvesting 5 micron filter 2 micron filter UV treatment from cistern To Green Dorm

13 Roof: Green Roof Green Roof Benefits Drawbacks JJC’s Design Thermal Comfort Plant Choice Materials Precipitation + Irrigation Runoff Agenda:

14 Roof: Green Roof Urban Heat Island (UHI) Effect Mitigation Aesthetic: Sound Insulation, Visually Pleasing Stormwater Runoff Reduction -- esp. Peak Runoff Energy Demand Reduction Particulate Matter Capture Roof Garden : Grow Edible Plants! Increases Roof Lifespan Recreation Area Benefits

15 Roof: Green Roof Costly Uses Rain [could be harvested] Irrigation Requirements [sometimes] Added Structural Support Maintenance: - Difficult - Time Consuming Drawbacks Alternatives to Green Roof: Rainwater Harvesting “Cool” Roofing (white / high albedo materials)

16 Roof: Green Roof Checkerboard for cooling effect [no large areas ungreened] Variety for experimentation Greater area Intensive [more insulation and runoff reduction benefits] Flowers visible Landscaping and Garden accessible Native grasses Flowers/Sedum Garden Photovoltaic/GR Landscaping = extensive = intensive JJC’s Proposed Design

17 Roof: Green Roof Roof Covering Roof Area Reasoning Extensive: Native Grasses 750 ft 2 No irrigation, grow on any slope, used on GR in San Bruno successfully Extensive: Flowers/Sedum 700 ft 2 No irrigation, don’t transpire as much (sedums), used in many GRs Extensive: PV - GR 400 ft 2 Experimental area -- not as large Near to other PVs for maintenance Intensive: Landscaped 1250 ft 2 Easy to access on roof deck, large for recreation, experiments, variety Intensive: Roof Garden 750 ft 2 Smaller for lower irrigation needs, large enough for several crops

18 Roof: Green Roof Thermal Comfort Metal, shingle, or red tile (Stanford) roofs get hot!! Green roof = nice - Keep roof cooler; make house cooler. - If air-conditioned, reduces energy demand. - Summer max temp only 35% of unvegetated roof max Monitoring heat flux…

19 Roof: Green Roof Plant Choice Criteria: Drought Tolerant Native to this Region Recommended to Clean Runoff PV-GR Less drought tolerant, like shade more Flower/SedumNative GrassesIntensive Coffee - berry California Poppy Purple Needle - grass Oregon Grape Emerald Carpet Manzanita Lupine Blue-eyed grass Pacific ninebark recommendations…

20 Roof: Green Roof Materials SectionGrowing Medium Depth Grasses, Flowers/Sedum 4-6” because this is considered ideal for sedums; grasses and flowers tolerate it too PV-GR 8” Because we use plants with slightly deeper root structures All Intensive ” hilly, varied thickness All Sections can have same materials, but vary growing medium - composition - depth /genomics/ecoli/greenroof

21 Roof: Green Roof MaterialTypeAll Sections? Reasons Growing Media 25% coarse sand, 25%fine brick, 25% compost, 25% limestone No, just extensive. Intensive w/ peat + more organics This mix was shown to leach least organic matter and fewer metals than other growing media tested Drainage Layer Recycled roof tiles Yes, but add’tl water storage good for intensive Recycled materials help overall sustainability of project and can reduce costs Root Barrier Heavy duty plastics w/ non- toxic membrane protecting layer Yes Roots need to be stopped with additional plastic layer, with non-toxic layer on top to prevent runoff contamination Waterproof Membrane Post-consumer recycled tires Yes Recycled material use better. Alternatives not recycled but similar.

22 Roof: Green Roof Precipitation vs. Irrigation Approach: - Most of roof NOT irrigated - Some sections healthier with irrigation - PV-GR section - Roof Garden - Part of Landscaped section - Compared evapotranspiration to precipitation and calculated demands

23 Roof: Green Roof Precipitation vs. Irrigation

24 Roof: Green Roof Runoff Total Runoff Reduction Rainfall Event SizePeak Flow Reduction (% compared to shingles) inches inches inches68 >1.6 inches50 Peak Reduction

25 Roof: Green Roof Summary Thermal Comfort~ 6 - 8˚ F cooler Peck, et. al 1999 Irrigation Demand 8, ,000 gallons/yr JJC’s calculations, Stanford Grounds Maintenance Precip vs. Et o chart Annual Runoff 5, ,000 gallons/yr JJC’s calculations, Mays, 2002 SCS method Runoff Time Lag estimate ~ 30 min delay on average York University Study, Canada Green Roof Research Program

26 Stormwater Management But how to deal with runoff from the yard (not just the roof??) Source: Dierkes, Carsten

27 Stormwater Management Porous Unit Pavers Double layered –Top fine layer acts as filter for pollutants –Bottom layer provides good infiltration, air exchange with soil Average infiltration rate: 3.6 gal/hr-ft 2 ≈ 1.6 in/hr Runoff coefficient: Source: Dierkes, Carsten 70% reduction compared to asphalt

28 Stormwater Management Bioretention Cells Grass buffer strips Sand bed Ponding area Organic layer Planting soil Vegetation Source: France, Robert L.

29 Stormwater Management Florida Aquarium Parking Lot Study Source: Environmental Protection Agency, Low Impact Development Guide

30 Ecological Wastewater Treatment Advantages (compared to established technologies): 1) Able to recycle resources other than water (e.g. nutrients as fertilizer) 2) Less intrusive on environment (create habitat for various species, add more green space) 3) Easier to modify or retrofit (greenhouse) system 4) Greater potential for research, experimentation and education

31 Ecological Wastewater Treatment Disadvantages (compared to established technologies): 1)Might be land intensive (probably need greenhouse) 2)Technology not yet approved by California State Department of Health

32 Ecological Wastewater Treatment 1)Danish Folkcenter of Renewable Energy (treats 3-4 m 3 /day, meets “Danish overall standard”—1.5 mg/L total-P, 15 mg/L total-N, 15 mg/L BOD 5 ) 2)Stensund Wastewater Aquaculture (treats ~17 m 3 /day. Nearly meets Swedish organic and bacteria standards for swimming water) 3)Solar Aquatic Systems (United States, British Columbia, Mexico—at least secondary standards)

33 Ecological Wastewater Treatment Observations Made from Case Studies 1) Algae and macrophyte (water hyacinth, duckweed, etc.) ponds seem to be popular in ecological wastewater treatment system design 2) Fish and invertebrates are widely used to remove unwanted nutrients 3) Ecological wastewater treatment systems seem to work best in green houses

34 Ecological Wastewater Treatment Aerial view of a possible design for greywater ecological treatment system (not to scale) Anaerobic Settling Tank (~ 5000 gallons) Aeration Basin (~5000 gallons) Greenhouse housing treatment system (~ 2000 ft 2 ) Basins are ~1.5 m deep 5m Duckweed basin with fish (e.g. tilapia)

35 Ecological Wastewater Treatment CMFR: C n /C o = [1/(1+ k c t n )] n PFR: C e /C o = exp(-k p t) CMFR -Open system -Constant input = Constant output -Uniform Concentration at steady state InfluentEffluent Longitude Influent Effluent -Open system -Input = Output -Perfect lateral mixing only PFR

36 Ecological Wastewater Treatment Calculations: Wehner and Wilhelm Equation: C e /C o = 4ae 1/(2D) /[(1+a) 2 (e a/(2D) )-(1-a) 2 (e -a/(2D) ] Proposed by Thirumurthi (1974) for systems in between CMFR and PFR

37 Ecological Wastewater Treatment Dimensions and Parameters -Recommended Total Hydraulic Residence Time, t = 14 days (7 days in each basin) -Width of Each Treatment Pond, W = 5 m -Length of Pond, L = 10 m -Depth of Liquid in Pond, d = 1 m -Land area required ~= 2000 ft 2 -Estimated total (dissolved plus particulate) BOD of effluent, C e = 11 mg/L << U.S. Minimum Treatment Standard of 30mg/L BOD (Criddle, 2007) -Estimated Output of Treated Greywater: 26,000 gallons per month - Extimated Output of Organic Matter from System: 40kg/ month

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40 Ecological Wastewater Treatment Greenhouse for greywater ecological treatment system can be integrated in this area (2000ft 2 of ~15,000 ft 2 ).

41 Ecological Wastewater Treatment *

42 Integrated Design Summary ~= 26,000 gals/mon output ~= 6000 gals/mon output

43 Conclusion JJC pledges to help the Green Dorm to “close the water loop” in innovative, sustainable, sanitary way Technologies explored include: - Green roof - Stormwater management - Ecological wastewater treatment For further information, contact C-Bo at: or (650)

44 Questions Questions?


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