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).

Ecological Wastewater Treatment

*

Integrated Design Summary

~= 26,000 gals/mon output

~= 6000 gals/mon output

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

QuestionsQuestions?