Transcript Slide 1

Presented by: Brian Soderholm
Water Control Corporation
1500 year-old, 21 million gallon Basilica Cistern in Istanbul, Turkey.
You May Have Major Questions!
• How big of a rainwater cistern to use?
• What to do with rainwater?
• What are other sources of reclaimable water?
• Where can I use graywater?
• What are the benefits and payback?
• What about sanitation? Is it safe?
• How to collect the water?
• How to store the water?
• How to best disinfect the water?
• How to best deliver the water to fixtures?
• What system options are available in the market?
• What about code compliance?
• 1 ft² roof surface can generate approximately 0.62 gallons of usable
water per inch of rainfall.
•Example: a 15,000 ft² roof in MN could generate approximately
15,000 X 4.34 X 0.62 = 40,362 gallons in an average July.
• A 40,000 gallon cistern may not be practical in a wetter climate.
• Only full after spring snow melt or major storm!
• Fixtures/equipment may not require so much water
• (in a dry climate, size near 100% and look for other sources)
• Wetter Climate Rule of Thumb: divide total gallons by avg.
peak monthly rainfall events – ex. For MN: 2 or 3 (i.e. 20,000 or
13,ooo gallon cistern) and compare to gal. required.
• Choose the smaller of the two when sizing cistern.
Other Potential Sources:
• Cooling System Condensate:
• 0.1 gal/ton hour at 70% relative humidity
• 0.2 gal/ton hour at 80% relative humidity
• 0.3 gal/ton hour at 90% relative humidity
• Challenge: low pH, bacteria
• Cooling Tower Blowdown
• Challenge: high TDS, chemicals
• Groundwater
• Challenge: soil-based minerals
• Softener/Filter Backwash
• Challenge: suspended solids and high TDS (depending
on type of filter)
Many Potential Uses:
• Rainwater can be collected and re-used for:
• Landscape irrigation
• Cooling tower/Boiler make-up water
• Tanker filling/ Backup fire systems
• Nursery irrigation systems
• Flushing toilets and urinals
• Vehicle washes
• Industrial process
• Potable water applications not recommended – and
probably not legal!
Graywater Reclamation:
• Graywater = Water from showers, bathroom lavs, clothes washers,
(possibly pool backwash).
• Reclaimed for sub-surface irrigation and (possibly) fixture flushing
• Toilet/urinal flushing requires disinfection and is only
legal/possible without special approval in IPC (and IPC-based)
states!
Graywater System Design Considerations:
• Enough storage for 1 or 2 days’ demand (code dependent).
• Tank water should turn at least every 3 - 7 days (code dependent).
• Overflow to sanitary sewer
• No blackwater! (toilet, kitchen sink, laundry with diaper service, etc.)
• Occupant # / Graywater discharge estimation tables in UPC and
IBC
• Up to 12+ LEED™ points may be available:
• “Stormwater Design: Quantity/Quality Control (2)”
• “Water Efficient Landscaping (4)”
• “Innovative Wastewater Technologies (2)”
• “Water Use Reduction (4+)”
• A virtual MUST for LEED™ Gold and Platinum
certification!
• Potential for drastically reduced sewer/water impact fees
• Reduced water and sewer fees
• Calculating “payback” requires number crunching!
• Good systems: $2000 - $200,000
Sanitation
• Public health risks:
• Bacteria, algae, pathogens, mold, insects, rodents,
(and almost anything else imaginable) seem to find
their way into cistern/storage tanks (ask your
grandparents!).
• Graywater is of particular concern.
• Cooling towers and irrigation systems can diffuse
these harmful agents into the air (think Leigionella
bacteria!).
• Toilets, urinals, and other fixtures supplied with
reclaimed water can cause internal contact with
these agents.
= Potential for major liability!
Designing a System: The 4 Concerns:
• Collection
• Storage
• Treatment
• Delivery
Thoughts on Collection:
• Consider roof drains with mesh screens if debris on roof
will be minimal
• Pre-filtration is always highly recommended!
• Water from drain tiles may contain iron or other minerals
(extra filtration required)
• Water from parking lots not recommended:
• May contain salt, oil, antifreeze, trash, goose feces,
etc.
Thoughts on Storage:
• Polyethylene, fiberglass, corrugated (lined), galvanized steel
or concrete tanks (verify compatibility with disinfection
method)
• Buried or located indoors in northern climates
• Overflow, vent, manhole access, and inlet/outlet tappings
required
• If above-ground, consider black or green color to prevent
algae growth
• Chlorination (oxidation):
• Advantages:
• Measurable
• Residual disinfection
•Calcium hypochlorite tablets
•Sodium hypochlorite solution
•Chlorine gas
•Chlorine dioxide solution
• Disadvantages:
• Not terribly “green” (LEED®)
• Chemical handling and storage
• Not good for landscaping
• Expensive/ongoing chemical purchase
• Trihalomethanes (THM’s) and other
harmful byproducts!
• Only ClO2 effective with algae
• Ultraviolet (DNA destruction to prevent replication):
• Advantages:
• No chemicals
• Relatively low cost and
maintenance up to 80 GPM systems
• Disadvantages:
• No residual disinfection (circulation highly
recommended!!!)
• Ineffective if water is discolored or turbid (UV
sensor highly recommended!!!)
• Not as effective with viruses or cysts
• Ozonation (oxidation using O3):
• Advantages:
• No chemicals – generated on demand
• 2000 times faster than chlorine
• Back to O2 in approx. 17 minutes
• Residual disinfection
• Powerful deodorizer
• Works in dirty/discolored water
• Measurable
• May help with Green Roof discoloration
• Disadvantages:
• More $$ and maintenance if under 80 GPM
• Cistern cannot be vented indoors w/o destructor
Thoughts on Delivery:
• pH may be an issue! (consider appropriate
piping materials!). Ozone/ chlorine also corrosive.
• Particulate filtration needed prior to delivery
(cartridge, bag, basket, or membrane filter)
• Most states have strict marking requirements
(“Non-Potable Water”)
• Incorporate a fresh-water bypass or make-up if
tank goes dry, disinfection goes down, etc.
• Ensure appropriate backflow prevention!
(RPZ assembly or “break tank” with air gap).
So How Are People Doing It?
• Individual component systems
designed in-house (contractor builds)
• Residential or light commercial
“rainwater harvesting kits”
• Large commercial turnkey systems
What About The Codes???
• Code Issues:
• A lack of clarity and consistency in state codes can lead to
confusion, delays, and disapprovals.
• Public health concerns
• Confusion at state, engineer, customer and inspector level
• Current code status:
• IPC: Rules for graywater only – no rainwater
• UPC: Rules for graywater and municipally treated
wastewater. Rainwater code currently under development
• Draft codes being developed by ARCSA, IAPMO
• California Title 22 statutes and USEPA 2004 Guidelines
for Water Reuse
•Plan Review is the norm! The more robust a system, the less likely
you are to experience hang-ups at state or inspector level!!!
Questions?