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Rainwater Harvesting For Decision Makers

Rainwater Harvesting For Decision Makers. Environment and Water Resource Department February 2008. What Is Rainwater Harvesting?.

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Rainwater Harvesting For Decision Makers

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  1. Rainwater Harvesting For Decision Makers Environment and Water Resource Department February 2008 .ppt (1)

  2. What Is Rainwater Harvesting? • 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 .ppt (2)

  3. Why Rainwater Harvesting? Conserve and supplement existing water resources Available for capture and storage in most global locations Potentially provide improved quality of water Supply water at one of the lowest costs possible for a supplemental supply source. Capturing and directing storm water (run-off) and beneficially use it Commitment as a corporate citizen - showcasing environmental concerns Public Mandate (India) Replenishing local ground water aquifers where lowering of water tables has occured .ppt (3)

  4. Why Not RWH? • 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 .ppt (4)

  5. Condensation Let’s take a look at The Water Cycle Precipitation Evapotranspiration Evaporation Infiltration Surface Runoff Surface Water Consumption Groundwater Sea water intrusion .ppt (5)

  6. Condensation Rainfall Definitions Intensity – Quantity per time of the rainfall event (mm/hour) Precipitation 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 Consumption Groundwater Surface Water .ppt (6)

  7. Design and Feasibility Criteria • Collection Area • Rainfall • Demand • Primary Use (Direct Use, Artificial Recharge (AR) or Aquifer Storage and Recovery (ASR)) • Storage capacity • Level of Security - risk of the storage tank running dry Harvesting potential(m3) = Area (m2) X Rainfall (m) X Collection Efficiency .ppt (7)

  8. Collection Area and Characteristics • Measure Area • Runoff Characteristics • Roof top 0.75 – 0.95 • Paved area 0.50 – 0.85 • Bare ground 0.10 – 0.20 • “Green area” 0.05 – 0.10 Water harvesting potential(m3) = Area (m2) X Rainfall (m) X Collection Efficiency .ppt (8)

  9. Average Annual Precipitation for Mexico Water harvesting potential(m3) = Area (m2) X Rainfall (m) X Collection Efficiency .ppt (9)

  10. Estimate Precipitation Quantity and Timing (All data in cm) .ppt (10)

  11. Feasibility Analysis • Example #1 • Roof area = 6000 sq meters • Average Annual Rainfall = 400 mm • Collection Coefficient = 0.90 • 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) .ppt (11)

  12. Feasibility Analysis 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 (12)

  13. 1 2 4 3 5 6 Raw water tank or Aquifer 7 Rain Water as Source WaterDesign Considerations Typical Diagram Recomendation 1 Roof 2 Screen 3 Discharge of water 4 Pre-filter 5 Storage tank 6 Flow meter 7 Storm water discharge .ppt (13)

  14. Aquifer Storage and Recovery or Artificial Aquifer Recharge? Require complete hydrogeological analysis, stakeholder engagement and potentially regulatory approval .ppt (14)

  15. Ground Water Recharge 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. .ppt (15)

  16. Storage • Storage devices may be either above or below ground • Different types include • Storage Tanks • Water Containers • Lagoons or Lined Ponds • Infiltration Ponds • Size based on rainfall pattern, demand, budget and area .ppt (16)

  17. Percolation Pit • To divert rainwater into an aquifer, • The percolation pit is covered with a perforated concrete slab • The pit is filled with gravel/ pebbles followed by river sand for better percolation. • The top layer of sand must be cleaned and replaced at least once in two years to remove settled silt for improving the percolation .ppt (17)

  18. Recharge Wells • The runoff water from rooftops or other catchments can be channelized into an existing /new well via sand filter to filter turbidity and other pollutants • Abandoned wells can also be used • Cost-effective process, which not only conserves rainwater for immediate use but also helps to enhance the local ground water situation .ppt (18)

  19. Quality Issues • Roofs contain: bird droppings, atmospheric dust, industrial and urban air pollution .ppt (19)

  20. Operational Procedures and Design Considerations • Screen to prevent birds, animal and insects; • Lead based paint must not be used on the roof; • Tar based roof coatings and materials should not be used – Phenolics and other organics can leach from materials • If roofs painted with acrylic paints, new concrete or metal roofing - first few rainfalls should not be collected to avoid metals, detergents, and other chemicals • Clean the gutters and tank every 3 months; .ppt (20)

  21. Operational Procedures and Design Considerations • Storage tank – dark materials to exclude light and algae formation • Corrosion resistant materials • Tank in protected shaded area – lower temperature • For multiple storage tanks – design for frequent turnover • Regional wind direction and industrial activity – Lead, Mercury, other heavy metals .ppt (21)

  22. Operational Procedures and Design Considerations • 10 minute purge • Chlorinate in storage • Clean tank when not used for long periods Cl2 Plant Use .ppt (22)

  23. Microbiological testing Total coliform Fecal coliform Heterotrophic bacteria Inorganic contaminant testing (metals) Organic chemicals Pesticides, Industrial Chemicals, Hydrocarbons Turbidity pH Acid rain (4.5) is often associated with man-made pollution Volcanic activity - sulfur dioxide (SO2) Frequency – annual or seasonal? Effect on treatment system? Initial Water Quality Sampling and Screening .ppt (23)

  24. Final Considerations • Legislation and Regulations in development in most of the countries in the world • Check on regulatory requirements especially if AR or ASR • Few operational projects all over the Operations System, but lots of interest showing up – • Use the TCCC Global Rainwater Harvesting Committee for help and approvals (web site soon?) • Very powerful tool towards sustainability • Safe, once the reccomended practices are fully observed .ppt (24)

  25. Andina Pilot Projectrainfall rates Rio de Janeiro State Rainfall rates (12 months) = 1,300 mm .ppt (26)

  26. Andina Pilot Project Cost-saving analyze • Estimated Calculation model • (estimated for all roof size) • Total volume = rate of rain per year x area (M²) • 1.3 x 55,700 • 72,410 M³ • 7% total income water • Savings = Total volume (M³) x Cost water (US) • 72,410 x 3.8 US$ Savings = $275,000/YEAR Payback less then 1 year .ppt (27)

  27. Lateral view gutters Rain water pipe VF-6 Filter Discharge the excess water Discharge - storm water system Rain water filtered Andina Project, Brazil 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 .ppt (28)

  28. Andina Pilot ProjectHarvesting system • Rain water distributed across the filter cascade; • 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. Cosh VF6 Filter operation: .ppt (29)

  29. SOLAR PANELS SLOPING GLASS FACADE WATER TANK GREEN ROOF WATER STORAGE GREEN ROOF WATER STORAGE POROUS PARKING WATER STORAGE FACADE – THERMAL MASS PASSIVE COOLING SYSTEM DEEPLY RECESSED WINDOWS – FILTERED LIGHT Green Design - Nairobi CHILLER UNITS .ppt (30)

  30. RAIN WATER HARVESTING FOR OFFICES – Developing a GREEN BUILDING in Nairobi, Kenya RAIN WATER ACCUMULATION IN LIEU OF STORM WATER ATTENUATION POND GREEN ROOF GREEN ROOF MANICURED LAWN GARDEN POROUS PARKING OZONATION FILTRATION OVERFLOW GROUND WATER REPLENISHING WELLS Concept & Design Principles BACKUP MUNICIPAL SUPPLY .ppt (31)

  31. PRINCIPLES OF A GREEN BUILDING - WATER • SYSTEM OF RAIN WATER HARVESTING AND GREY WATER ARE COMBINED TO ACHIEVE THE FOLLOWING: • 25% OF POTABLE WATER CONSUMPTION REDUCTION • 100% OF POTABLE WATER PROVIDED BY RAIN • 50% REDUCTION OF SEWER QUANTITIES .ppt (32)

  32. Establishing the need in India… A news article says that ground water levels in New Delhi are falling and RWH will become mandatory. .ppt (33)

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