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RWH technology consists of simple systems to collect, convey, and store rainwater. Rainwater capture is accomplished primarily from roof-top, surface runoff, and other surfaces.
RWH either captures stored rainwater for direct use (irrigation, production, washing, drinking water, etc.) or is recharged into the local ground water and is call artificial recharge.
In many cases, RWH systems are used in conjunction with Aquifer Storage and Recovery (ASR). ASR is the introduction of RWH collected rainwater to the groundwater / aquifer through various structures in excess of what would naturally infiltrate then recovered for use
Not applicable in all climate conditions over the world
Performance seriously affected by climate fluctuations that sometimes are hard to predict
Increasingly sophisticated RWH systems (ASR) necessarily increases complexities in cost, design, operation, maintenance, size and regulatory permitting
Collected rainwater can be degraded with the inclusion of storm water runoff
Collected water quality might be affected by external factors
Collection systems require monitoring and continuous maintenance and improvement to maintain desired water quality characteristics for water end-use
Certain areas will have high initial capital cost with low ROI
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.ppt ( ) Condensation Precipitation Evaporation Surface Water Infiltration Evapotranspiration Let ’ s take a look at The Water Cycle Consumption Surface Runoff Groundwater Sea water intrusion
.ppt ( ) Condensation Precipitation Surface Water Groundwater Consumption Rainfall Definitions Intensity – Quantity per time of the rainfall event (mm/hour) Duration – period of time for the precipitation event Average Annual and Monthly Precipitation – Average rainfall over one year period and monthly intervals and usually based on 30 or more years of data
Potential = 6000 sq meters * 0.4m * 0.90 = 2,160 cu meters/ year
Cost for Water = US $4.00/ cubic meter
Savings = $8,640.00 (does not include maintenance)
Demand = 50,000 cu meter/ month
Supply = 0.4% of demand
Overall Cost to Install = $150,000 (low ROI)
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Feasibility Analysis .ppt ( ) Example #2 Roof area = 6000 sq meters Average Annual Rainfall = 1400 mm Collection Coefficient = 0.90 Potential = 6000 sq meters * 1.4m * 0.90 = 7,560 cu meters/ year Cost for Water = US $4.00/ cubic meter Savings = $30,240.00 (does not include maintenance) Demand = 50,000 cu meter/ month Supply= 1.3% of demand Overall Cost to Install = $150,000 (acceptable ROI?)
.ppt ( ) 1 Roof 2 Screen 3 Discharge of water 4 Pre-filter 5 Storage tank 6 Flow meter 7 Storm water discharge Rain Water as Source Water Design Considerations Typical Diagram Recomendation Raw water tank or Aquifer 1 2 3 4 5 6 7
Aquifer Storage and Recovery or Artificial Aquifer Recharge? .ppt ( ) Require complete hydrogeological analysis, stakeholder engagement and potentially regulatory approval
Ground Water Recharge .ppt ( ) Under natural conditions it may take days to centuries to recharge ground water by rain water. As we need to replenish the pumped water, Artificial Recharge of Ground water is required at some locations.
Andina Pilot Project Cost-saving analyze .ppt ( ) US$ Savings = $275,000/YEAR Payback less then 1 year
Andina Project, Brazil .ppt ( ) Total investment: US$ 150,000 October/2006: Under implementation Rainwater harvesting system for 100% of the roof Pilot Project Pilot project: 2004/2005 Roof size: 6,000 m2 Collection rainwater from the gutters Filtration at filter system Storage in 5,000-liter tank Lateral view gutters VF-6 Filter Discharge - storm water system Discharge the excess water Rain water filtered Rain water pipe
Larger dirt particles are washed across the cascades;
Pre filtered water flows over a second filter (mesh size 0.55 mm), low maintenance;
Cleaned water flows to the storage tank;
Dirt goes to the sewer.
.ppt ( ) Cosh VF6 Filter operation:
Green Design - Nairobi .ppt ( ) CHILLER UNITS SOLAR PANELS GREEN ROOF WATER STORAGE GREEN ROOF WATER STORAGE POROUS PARKING WATER STORAGE WATER TANK FACADE – THERMAL MASS PASSIVE COOLING SYSTEM DEEPLY RECESSED WINDOWS – FILTERED LIGHT SLOPING GLASS FACADE
.ppt ( ) MANICURED LAWN POROUS PARKING GARDEN GREEN ROOF GREEN ROOF OZONATION FILTRATION BACKUP MUNICIPAL SUPPLY RAIN WATER HARVESTING FOR OFFICES – Developing a GREEN BUILDING in Nairobi, Kenya Concept & Design Principles OVERFLOW GROUND WATER REPLENISHING WELLS RAIN WATER ACCUMULATION IN LIEU OF STORM WATER ATTENUATION POND