Presented by: Brian Soderholm Water Control Corporation

Transcription

1 Presented by: Brian Soderholm Water Control Corporation

2 1500 year-old, 21 million gallon Basilica Cistern in Istanbul, Turkey.

3 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?

4 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.

5 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)

6 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!

7 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!

8 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

9 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

10 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!

11 Designing a System: The 4 Concerns: Collection Storage Treatment Delivery

12 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.

13 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

14 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

15 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

16 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

17 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).

18 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

19 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!!!

20 Questions?