water system design for stanford university green dorm: progress report jjc engineering consultants...
TRANSCRIPT
Water System Design forStanford 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
• 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
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
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)
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
Rinsing Other
Example 15 min 4 min 2 min 4 1 min
Wednesday 2-May
Thursday 3-May
# in-dorm toilet flushes: ~= 7Loads of laundry per week ~= 1
Water Balance
Item Demand (gal/day) Demand (gal/month)
Dish Washing 50 1500
Domestic Cleaning 70 2100
Leaks 130 3900
Faucet - Kitchen 310 9600
Faucet - Bathroom 200 6000
Shower 600 18000
Laundry 80 2400
Toilet Flushing 500 15000
Hobart (sanitizing) 140 4200
Irrigation 180 5400
Total ~2300 ~69000Greywater sources: Domestic Cleaning, Bathroom Faucet, Shower, Laundry (~ 28,500 gallons total)Blackwater sources: Dishwashing, Kitchen Faucet, Toilet Flushing, Hobart (~ 30,000 gallons total)
Proposed Target
• Consider California Title-22
• Domestic house cleaning, irrigation, toilet flushing and laundry
• Total demand of about 25,000 gallons per month
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
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-
treatmentSource: The Texas Water Development Board
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
Roof: Rainwater Harvesting
0
10000
20000
30000
40000
50000
60000
70000
J F M A M J J A S O N D
Month
Cummulative Runoff [gallons]
maximum storage needed30,000 gal
demand for laundryand cleaning150 gal/day
parameters:-average precipitation-runoff coefficient = 0.75
Specifications• Two 15,000 gal
underground cisterns
• Material: ferrocement
• Integrated into dorm design
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
UVtreatment
from
cistern
To Green
Dorm
Roof: Green Roof
Green Roof Benefits
Drawbacks
JJC’s Design
Thermal Comfort
Plant Choice
Materials
Precipitation + Irrigation
Runoff
Agenda:
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
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)
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
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
Roof: Green Roof
Roof CoveringRoof Area
Reasoning
Extensive:Native Grasses 750 ft2
No irrigation, grow on any slope, used on GR in San Bruno successfully
Extensive:Flowers/Sedum 700 ft2
No irrigation, don’t transpire as much (sedums), used in many GRs
Extensive:PV - GR 400 ft2
Experimental area -- not as large
Near to other PVs for maintenance
Intensive:Landscaped 1250 ft2
Easy to access on roof deck, large for recreation, experiments, variety
Intensive:Roof Garden 750 ft2
Smaller for lower irrigation needs, large enough for several crops
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 maxMonitoring heat flux…
Roof: Green Roof
Plant Choice Criteria: Drought Tolerant Native to this Region Recommended to Clean Runoff
PV-GRLess drought tolerant, like
shade more
Flower/Sedum Native Grasses Intensive
Coffee - berry
California Poppy
Purple Needle -
grass
Oregon Grape
Emerald Carpet
ManzanitaLupine
Blue-eyed grass
Pacific ninebark
recommendations…recommendations…
Roof: Green Roof
Materials
Section Growing 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 12 - 18” hilly, varied thickness
All Sections can have same materials, but vary growing medium - composition - depth
http://www.glwi.uwm.edu/research/genomics/ecoli/greenroof
Roof: Green Roof
Material Type All 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
YesRoots 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.
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
Roof: Green Roof
Precipitation vs. Irrigation2004 Precipitation, Runoff & Irrigation from Green Roof
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
1 18 35 52 69 86 103 120 137 154 171 188 205 222 239 256 273 290 307 324 341 358
day
inches
Rainfall4-inch roof6-inch roof12-inch roof18-inch roofaverage irrigation
Roof: Green Roof
Runoff
Roof Runoff
1.215
0.39
0.88
0.093
0.67
0.039
0.31
0.13
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Inches
Rainwater Harvesting4'' Growing Medium6 inches12 inches18 inches
Ten Year Storm,1.62 inches total
Average Storm,.522 inches total
Total Runoff Reduction
Rainfall Event Size Peak Flow Reduction (% compared to shingles)
.4 - .8 inches 88
.8 - 1.2 inches 87
1.2 - 1.6 inches 68
>1.6 inches 50
Peak Reduction
Roof: Green Roof
Summary
Thermal Comfort ~ 6 - 8˚ F coolerPeck, et. al
1999
Irrigation Demand8,000 - 12,000
gallons/yr
JJC’s calculations, Stanford Grounds Maintenance Precip vs. Eto chart
Annual Runoff 5,000 - 8,000 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
Stormwater Management
But how to deal with runoff from the yard (not just the roof??)
Source: Dierkes, Carsten
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
Stormwater Management
Bioretention Cells• Grass buffer strips• Sand bed• Ponding area• Organic layer• Planting soil• Vegetation
Source: France, Robert L.
Stormwater Management
Florida Aquarium Parking Lot Study
Source: Environmental Protection Agency, Low Impact Development Guide
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) system4) Greater potential for research, experimentation
and education
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
Ecological Wastewater Treatment
1) 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)
2) Stensund Wastewater Aquaculture (treats ~17 m3/day. Nearly meets Swedish organic and bacteria standards for swimming water)
3) Solar Aquatic Systems (United States, British Columbia, Mexico—at least secondary standards)
Ecological Wastewater Treatment
• Observations Made from Case Studies1) 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
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 ft2) Basins are ~1.5 m deep
5mDuckweed basin with fish (e.g. tilapia)
Ecological Wastewater Treatment
CMFR: Cn/Co = [1/(1+ kctn)]n PFR: Ce/Co = exp(-kpt)
CMFR
-Open system -Constant input = Constant output -Uniform Concentration at steady state
Influent Effluent
Longitude
Influent
Effluent
-Open system -Input = Output -Perfect lateral mixing only
PFR
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
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
Ecological Wastewater Treatment
Greenhouse for greywater ecological treatment system can be integrated in this area (2000ft2 of ~15,000 ft2).
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:[email protected], or (650)-200-9198