Rainwater Harvesting in a Drought by Phyllis Muska and Dan Behringer
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Transcript of Rainwater Harvesting in a Drought by Phyllis Muska and Dan Behringer
Rainwater Harvesting in a Drought
Dan Behringer & Phyllis Muska
Texas Master Naturalist – Hill Country Chapter
October 26, 2011
Why rainwater?Conserve water resources to help preserve water levels in the aquiferSuperior water quality – softer water means less detergent, no lime/calcium buildup on shower walls and appliancesPlants and landscape prefer rainwaterMay be more dependable than a wellSave money if using city water –30-50% of total water used by a typical home is for landscape wateringReduces volume of storm water during heavy rain eventsMay lessen erosion from runoffNo chemicals or additives necessaryIt tastes good!
What are the components of a Rainwater Harvesting system?
Collection
Conveyance
Storage
Treatment
System Components
Collection –Catchment surface: the collection surface from which rainfall runs offConveyance from catchment surface –Gutters, downspouts, and pipe channel water from the roof to the tankStorage –One or more tanksConveyance to point of use –Delivery system gravity-fed or pumped to end useTreatment/purification –
Initial filtration – Leaf screens, first wash diverters, and roof washers remove debris and dust from the captured rainwater before it goes to the tankFor potable systems, filters, UV lights, and other methods make the water safe to drink
System Schematic
Catchment Surface #1
Phase 1 – 550 sq ft garage – 1996
Catchment Surface #2
Phase 2 – 2000 sq ft house - 2001
Catchment Surface #3
Phase 3 – 2003
2400 sq ft barn
Gutters and Downspouts
Gutters and Downspouts
Fiberglass Tanks with Food-Grade LinerPhase 1: 5,000 gal
Phase 2: 10,000 gal
Phase 3: 10,000 gal
Tanks must be same height!
Polyethylene tanks
Riverside Nature Center – 5000 gallons
Metal tanks
Pioneer tanks from Australia
First Wash System – standing pipe
First Wash System – rain barrel
First Wash System – the Eliminator
Cost ~$1200
First Wash System – vortex filter
First Wash System – Filtration box
Fiberglass box with removable filters – $600-$800
Floating Cistern Filter
~$450
Grundfos MQ pump
~$575
Filters
UV light
- Sanitron Ultraviolet S-37B
- UV disinfection to kill bacteria
- 12 gpm
- Built-in bulb cleaning apparatus
- ~$900
Pump, Filtration and UV Light
~$2000
Quick-Connect Valve
What happens if it doesn’t rain?
1” rain -> 600 gallons for each 1000 sq ft collection surface, depending on efficiency
2500 sq ft house: 1500 gallons per inch of rain
Add a barn and garage to the system to total 5000 sq ft = 3000 gallons with just 1” rain!
It’s All About Storage . . .
2007: 45” of rain
135,000 gallons went through system
Our annual usage: approximately 36,000 gallons
So . . . almost 100,000 gallons got away!
. . .
2011: 6” of rain over last 12 months
May need to have water hauled in
. . . And timing
Figure approximately 50-75 gallons per day per person
For 2 people: 3000-4500 gallons/month requires an average of 1”-1½” rain/month
25,000 gallons = 7-8 month supply
1996 – summer 2011: never below a two-month supply
To calculate capacity needed, figure on historic maximum number of days with no rain
How pure is the water?Is it really OK to drink?
5-micron spin filter
3-micron charcoal filter
UV light
Tests almost the same as distilled water
pH around 6.0
Tests available through UGRA, LCRA
Summer 2009 UTHSC StudyUT Health Science Center at Tyler - Potable Rainwater Study - Summer 2009
Rainwater Sampling Results
Participant: Behringer/Muska
Date of Sampling: 8-8-09
Test Result pre-filtration Result post-filtration Recommended Limit of Detection
(LOD)
pH 6.5 5.9 6.5-8.5
alkalinity ppm 20 20 <150 mg/L
hardness ppm 0 0 >120 mg/L=hard water
free chlorine ppm 0 0
total chlorine ppm 0 0 <4 ppm
nitrates ppm 0 0 <10 ppm
nitrites ppm 0 0 <1 ppm
conductivity µS/cm 13.93 16.68 <1000 µS/cm
total dissolved solids mg/L 6.1 7.5 <500 mg/L
total bacteria light growth, <100 0 <500 colonies/ml
coliform bacteria 0 0 0
lead ppb 2.813 not detected <15 ppb .2622 ppb
copper ppm not detected 0.0723 <1.0 ppm .0057 ppm
iron ppm not detected not detected <0.3 ppm .003 ppm
zinc ppm 0.2694 0.357 <5 ppm .0006 ppm
aluminum ppm 0.0198 not detected <0.05 to 0.2 ppm .0162 ppm
arsenic ppm
Heavy metal testing was performed by the Water Analysis Lab at Stephen F. Austin University
CostsRough estimate for 20,000 gallon system, 2000 sq ft footprint, potable water:
Two fiberglass, polyester resin-lined 10K tanks @ $7,500: $15,000
Or one metal Pioneer tank 20K: $12,000
Gutters and downspouts: $500
First wash: $600-1500 per inlet
Pump: $600
Filtration and UV: $1000
Total: $15,000-$20,000 + delivery + labor – comparable to drilling a well in many areas
Maintenance
Change filters monthly/quarterly ~$100/yr
Clean gutters as needed –1-2 times/year
Replace UV bulb every 12-14 months ~$80-$100
It’s Catching On . . .Recent survey by TRCA – data from over 1,000 systems with total capacity of over 15,000,000 gallons
More than 6,000 rain barrels were installed through the City of Austin’s incentive program from 1995-2005
More than 100,000 residential systems in the US installed by professionals
Countless do-it-yourself systems in place
Kroc Center in Kerrville – 135,000 gallons
Boerne Champion High School
Willow City Volunteer Fire Department –24,000 gallon system: gravity flow dispensing system can fill a 400-gal tank on a brush truck in 2 minutes
Riverside Nature Center 5,000 gallon system collecting off ~4500 sq ft – takes only a 2” rain to fill
Menard Library – with demonstration gardens
Lady Bird Johnson Wildflower Center in Austin – 70,000 gallons
Commercial applications
Non-potable applications
Collecting water for irrigation purposes: can be as simple as running a hose from a downspout to a rain barrel
Non-potable applicationsRain “pillow” – 1000+ gallons stored in a bladder under the deck
10' x 8' x 2' tall (when filled) 1000 gallons ~$2500
Non-potable applications
Guzzler – watering station for wildlife and/or livestock
Water Conservation
Key to preserving our precious water resourcesCultivate a mindset for conservation until it becomes second nature – use, re-use, then use again!Pay special attention to these guzzlers:
ToiletsAppliances Landscape wateringSprinkler systems
Avoid bare dirt – prevent runoff and erosion Landscaping: use native grasses, shrubs, forbsCollect condensate from A/C
Additional Resources
http://www.twdb.state.tx.us/iwt/rainwater.asp
http://www.greenbuilder.com/sourcebook/Rainwater.html
http://www.rainwatercollection.com
Taste test
Have a sample of our ‘cloud juice’ – fill your water bottle!