Difference between revisions of "Stormwater re-use and rainwater harvesting"
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<p>This treatment can include varying levels of filtration (for removal of debris, suspended and colloidal solids, residual suspended solids, residual colloidal solids, dissolved solids, residual and specific trace constituents) and disinfection (ultraviolet radiation, chlorination, and ozone). Many of the typical filtration methods can filter out particle sizes greater than 5 microns to 500 microns, depending on the type of filter selected and the level of treatment required (Contech, 2012). Common filtration methods include mechanical sand or disc filtration, in-pipe treatment filtration, cartridge and bag filters, filter screens, and sediment tanks. Ultraviolet (UV) disinfection is the most practical and commonly used disinfection techniques for small- to medium-sized systems, while chlorination can be more common in larger systems (Australia, 2009).</p> | <p>This treatment can include varying levels of filtration (for removal of debris, suspended and colloidal solids, residual suspended solids, residual colloidal solids, dissolved solids, residual and specific trace constituents) and disinfection (ultraviolet radiation, chlorination, and ozone). Many of the typical filtration methods can filter out particle sizes greater than 5 microns to 500 microns, depending on the type of filter selected and the level of treatment required (Contech, 2012). Common filtration methods include mechanical sand or disc filtration, in-pipe treatment filtration, cartridge and bag filters, filter screens, and sediment tanks. Ultraviolet (UV) disinfection is the most practical and commonly used disinfection techniques for small- to medium-sized systems, while chlorination can be more common in larger systems (Australia, 2009).</p> | ||
===Pumping and Distribution System=== | ===Pumping and Distribution System=== | ||
| − | <p>The final component of the stormwater harvesting and reuse system includes the pumping and distribution system. Typically, the pumping system is set-up in conjunction with the treatment system. | + | <p>The final component of the stormwater harvesting and reuse system includes the pumping and distribution system. Typically, the pumping system is set-up in conjunction with the treatment system. Additionally, the type and requirements for the distribution system are dependent on the end use of the stormwater. Often when designing stormwater harvesting and reuse systems as a means of runoff reduction, there is need for a back-up supply of water for essential applications (Contech, 2012).</p> |
<p>There are a variety of irrigation distribution systems. Each type of irrigation system has different potential for public exposure to the water used for irrigation and may impact the required water quality standards for the reused water to be utilized. Systems often used for urban irrigation include:</p> | <p>There are a variety of irrigation distribution systems. Each type of irrigation system has different potential for public exposure to the water used for irrigation and may impact the required water quality standards for the reused water to be utilized. Systems often used for urban irrigation include:</p> | ||
*Drip, or trickle, irrigation is a method if localized irrigation that allows for water to drip slowly to the roots of plans. This irrigation occurs either at the surface or subsurface, where it is directly to the root zone. This system is comprised of emitters to distribute water either along the length of the line or at point emitters along the distribution line. These systems allows for efficient use of water as well as safe use of non-potable water. However, these systems typically require sufficient filtering of the water as they can easily become clogged with soil and sediment particles, algae, or mineral precipitates (NDSU, 2003). | *Drip, or trickle, irrigation is a method if localized irrigation that allows for water to drip slowly to the roots of plans. This irrigation occurs either at the surface or subsurface, where it is directly to the root zone. This system is comprised of emitters to distribute water either along the length of the line or at point emitters along the distribution line. These systems allows for efficient use of water as well as safe use of non-potable water. However, these systems typically require sufficient filtering of the water as they can easily become clogged with soil and sediment particles, algae, or mineral precipitates (NDSU, 2003). | ||
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<p>Uniform Plumbing Code. 2012 (draft). Chapter 17 Nonpotable Rainwater Catchment Systems.</p> | <p>Uniform Plumbing Code. 2012 (draft). Chapter 17 Nonpotable Rainwater Catchment Systems.</p> | ||
<p>University of Minnesota Water Resources Center. January 2010 (draft). Water Use in Minnesota.</p> | <p>University of Minnesota Water Resources Center. January 2010 (draft). Water Use in Minnesota.</p> | ||
| − | <p>University of Minnesota Extension. 2009. Watering Lawns and Other Turf.</p> | + | <p>University of Minnesota Extension. 2009. Watering Lawns and Other Turf.</p>--> |
Revision as of 19:39, 19 June 2013
Rain water harvesting is the practice of collecting rain water from impermeable surfaces, such as rooftops, and storing for future use. There are a number of systems used for the collection, storage and distribution of rain water including rain barrels, cisterns, evaporative control systems, and irrigation.
Contents
Design Criteria
- The system should be watertight, have a smooth interior surface, be located on level and stable ground, have a tight-fitting lid, good screens on the inlet and outlet and have an emergency overflow device.
- To prevent the breeding of mosquitoes, empty the water in less than 5 days or place a fine screen over all openings.
- Material can withstand the pressure of water over long periods of time.
- Disconnect and drain rain barrels and cisterns in the winter to prevent freezing and deformation of the rain water harvesting system.
Management suitability
- Water Quality (Vwq) - High1
- Channel Protection (Vcp) - Med.
- Overbank Flood Protection (Vp10) - Low
- Extreme Flood Protection (Vp100) - Low
- (Recharge Volume (Vre) - High1
1Assumes water is drained to a vegetated pervious area. does not apply to volume of runoff that bypasses the system.
Mechanisms
- Infiltration1
- Screening/ Filtration1
- Temperature Control
- Settling
- Evaporation
- Transpiration1
- Soil Adsorption1
- Biological/ Micro. Uptake1
1Assumes water is drained to a vegetated pervious area. does not apply to volume of runoff that bypasses the system.
Pollution Removal
- Total Suspended Solids - 100%1
- Nutrients - Total Phosphorus/Total Nitrogen- 100%1
- Metals - Cadmium, Copper, Lead, and Zinc- 100%1
- Pathogens - Coliform, Streptococci, E. Coli- 100%1
- Toxins - Hydrocarbons, Pesticides- 100%1
1Assumes water is drained to a vegetated pervious area. does not apply to volume of runoff that bypasses the system.
Site factors
- Drainage Area - Rooftop
- Max. Slope - NA
- Min. Depth to Bedrock - NA
- Min. Depth to Water Table - NA
- SCS Soil Type - can be used in C&D soil types with modifications (e.g. underdrains) - NA
- Poor Freeze/ Thaw Suitability - NA
- Potential Hotspot Runoff - Suitable
1Assuming water is drained to a vegetated pervious area. Does not apply to volume of runoff that bypasses the system
Benefits
- Protects water supplies by reducing use during peak summer months.
- Mimics the natural hydrology of the area by infiltrating a portion of the rain water falling on the site.
- Reduces volume of storm water being delivered to downstream waterbodies.
- Results in cost savings by reducing municipal water bill.
Limitations
- Not suitable for the following roof types: tar and gravel, asbestos shingle and treated cedar shakes.
- Depending on the design, requires a certain amount of operation and maintenance.
- Proprietary systems can be expensive.
Description
Rain water harvesting can be accomplished using rain barrels and/or cisterns. Rain barrels are typically located at the downspout of a gutter system and are used to collect and store rainwater for watering landscapes and gardens.
The simplest method of delivering water is by the force of gravity. However, more complex systems can be designed to deliver the water from multiple barrels connected in a series with pumps and flow control devices.
Cisterns have a greater storage capacity than rain barrels and may be located above or below ground. Due to their size and storage capacity, these systems are typically used to irrigate landscapes and gardens on a regular basis reducing the strain on municipal water supplies during peak summer months. Again, cisterns may be used in series and water is typically delivered using a pump system.
The storage capacity of a rain barrel or cistern is a function of the catchment area, the depth of rainfall required to fill the system and the water losses. A general rule of thumb in sizing rain barrels or cisterns is that one inch of rainfall on a 1,000 square foot roof will yield approximately 600 gallons of runoff.