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Water System Design for Stanford University Green Dorm: Progress Report

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. Scope of Presentation.

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Water System Design for Stanford University Green Dorm: Progress Report

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  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 # in-dorm toilet flushes: ~= 7Loads of laundry per week ~= 1

  6. Water Balance 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 ft2 • 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 Specifications • Two 15,000 gal underground cisterns • Material: ferrocement • Integrated into dorm design parameters: -average precipitation -runoff coefficient = 0.75

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

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

  14. Roof: Green Roof Benefits • 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

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

  16. Roof: Green Roof JJC’s Proposed Design Photovoltaic/GR • 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 Garden Landscaping Flowers/Sedum = extensive = intensive

  17. Roof: Green Roof

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

  19. Roof: Green Roof Plant Choice • Criteria: • Drought Tolerant • Native to this Region • Recommended to Clean Runoff recommendations…

  20. Roof: Green Roof Materials All Sections can have same materials, but vary growing medium - composition - depth http://www.glwi.uwm.edu/research/genomics/ecoli/greenroof

  21. Roof: Green Roof

  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 Peak Reduction Total Runoff Reduction

  25. Roof: Green Roof Summary

  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-ft2 ≈ 1.6 in/hr • Runoff coefficient: 0.15-0.25 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): • Might be land intensive (probably need greenhouse) • Technology not yet approved by California State Department of Health

  32. Ecological Wastewater Treatment • Danish Folkcenter of Renewable Energy (treats 3-4 m3/day, meets “Danish overall standard”—1.5 mg/L total-P, 15 mg/L total-N, 15 mg/L BOD5) • Stensund Wastewater Aquaculture (treats ~17 m3/day. Nearly meets Swedish organic and bacteria standards for swimming water) • 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 Anaerobic Settling Tank (~ 5000 gallons) Aeration Basin (~5000 gallons) Duckweed basin with fish (e.g. tilapia) 5m Basins are ~1.5 m deep Greenhouse housing treatment system (~ 2000 ft2) Aerial view of a possible design for greywater ecological treatment system (not to scale)

  35. Ecological Wastewater Treatment CMFR: Cn/Co = [1/(1+ kctn)]n PFR: Ce/Co = exp(-kpt) Influent Longitude Influent Effluent PFR CMFR Effluent -Open system -Constant input = Constant output -Uniform Concentration at steady state -Open system -Input = Output -Perfect lateral mixing only

  36. Ecological Wastewater Treatment • Calculations: Wehner and Wilhelm Equation: Ce/Co = 4ae1/(2D)/[(1+a)2(ea/(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 ft2 -Estimated total (dissolved plus particulate) BOD of effluent, Ce = 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

  38. Ecological Wastewater Treatment Greenhouse for greywater ecological treatment system can be integrated in this area (2000ft2 of ~15,000 ft2).

  39. Ecological Wastewater Treatment *

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

  41. 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: chengboon.yap@stanford.edu, or (650)-200-9198

  42. Questions? Questions

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