Rainwater harvesting


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Crisis of water, Rainwater harvesting, A sample design

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Rainwater harvesting

  2. 2. The World Water Crisis Rapid population growth, combined with industrialization, urbanization, ag ricultural intensification and water-intensive lifestyles is resulting in a global water crisis. In 2000, at least 1.1 billion of the world’s people - about one in five – did not have access to safe water. Asia contains 65 per cent of the population without safe water and Africa 28 per cent.
  3. 3. Bangladesh Water Crisis Bangladesh’s water crisis affects both rural and urban areas, and is a matter of both water scarcity and water quality. In the late 1970 s, approx. four million wells were drilled to replace the traditional contaminated surface water sources. The projects made significant headway, and mortality due to water-related diseases declined. However, in 1993, high arsenic concentrations were discovered in the groundwater of several wells in western Bangladesh. Long-term intake of high concentrations of arsenic from drinking water gives rise to a number of health problems, particularly skin disorders. Internal cancers have also been linked with arsenic in drinking water.
  4. 4.  The size of the urban population is increasing at alarming rates. Taking into account the current groundwater depletion trend at 2.81 m/y, a projection has been made for 2050 and it predicts that the groundwater table will be lowering down to 120 meters by 2050 from the existing water .
  5. 5. Current Water Supply in Dhaka Total production capacity of DWASA is 2247.47 Million Liter per Day (MLD) (both groundwater and surface water. Water supply in Bangladesh relies mainly on groundwater. In rural areas, more than 97 percent of the population extracts groundwater to fulfill drinking water demands. Whereas, 87.72 percent of the Dhaka city‟s water supply is dependent on groundwater resources. Even though Dhaka city is surrounded by the four rivers namely Buriganga, Balu, Turag and Tongi Khal but only 12.28 percent of supplied water is obtained from these rivers. Table 1: Water production scenario of DWASA
  6. 6. Whatcan we do? some other recommendations to improve the water Crisis in bd may be listed as follows:  Surrounding rivers and canals inside should be kept free from pollution and illegal occupation and increase the treatment plant for surface water to supply as demand .  Rainwater harvesting should be introduced at a massive scale to ensure supply of drinking water to the households who still have no piped connection.  Sense of ownership is crucial to manage water supply sustainably. Active participation of key stakeholders i.e. officials, representatives, individuals, community people etc. should be ensured at all levels of planning, implementation, regulation, monitoring, and evaluation of water supply scenario.  Sewerage treatment system should be more efficient so that effluents do not pollute their destination.  New technologies should be incorporated to improve the quality and efficiency of surface water treatment plants (SWTPs).  Proper awareness campaign through print and electronic media should be carried out to inform and to aware people regarding „right to water‟ and the reduction of the misuse of water.
  7. 7. Basic idea of Rainwater Harvesting Rainwater harvesting, in its broadest sense, is a technology used for collecting and storing rainwater for human use from rooftops, land surfaces or rock catchments using simple techniques such as jars and pots as well as engineered techniques.
  8. 8. RainwaterHarvestingAroundtheWorld The concept of rainwater harvesting has been accepted by many cities, government agencies, societies, individuals, etc in different countries around the world. They have set the examples of RWH systems. There are many success stories of RWH in developing and developed countries of Asia, Africa, Latin America, USA, Japan, Germany, Singapore and others. A wooden water tank in Hawaii, USA ‘Rajison’ a simple and unique rainwater utilization facility at the community level in Tokyo, Japan. Thai Jar: RWH System inThailand
  9. 9. Rainwater Harvesting - Multiple Benefits  Improvement in the quality of ground water  Rise in the water levels in wells and bore wells that are  Drying up  Mitigation of the effects of drought and attainment of drought proofing  An ideal solution to water problems in areas having inadequate water resources  Reduction in the soil erosion as the surface runoff is reduced  Decrease in the choking of storm water drains and flooding of roads  Saving of energy, to lift ground water. (One-meter rise in water level saves 0.40-kilowatt hour of electricity)
  10. 10. Rainwater Harvestingbasicelements: Typically, a rainwater harvesting system consists of three basic elements:  The collection system : Collection systems can vary from simple types within a household to bigger systems where a large catchment area contributes to an impounding reservoir from which water is either gravitated or pumped to water treatment plants.  The conveyance system : Conveyance systems are required to transfer the rainwater collected on catchment surfaces (e.g. rooftops) to the storage tanks .  The storage system : Storage tanks for collecting rainwater may be located either above or below the ground.
  11. 11. ComponentsofaRainwaterHarvestingSystem All rainwater-harvesting systems comprise six basic components irrespective of the size of the system. 1. Catchment area/roof 2. Gutters and downspouts 3. Leaf screens and roof washers 4. Cisterns or storage tanks 5. Conveying 6. Water treatment.
  12. 12. Catchment Surface The catchment area of a water harvesting system is the surface, which receives rainfall directly and contributes the water to the system. It can be a paved area like a terrace or courtyard of a building, or an unpaved area like a lawn or open ground. For in house uses, rooftop harvested rainwater is safer for drinking purposes than the runoff harvested water.
  13. 13. Storing Rainwater or Recharging Ground Water Aquifers Rainwater can be stored for direct use or alternatively it can be charged into the ground water aquifers. This can be done through any suitable structures like dug wells, bore wells, recharge trenches and recharge pits.
  14. 14. Filters The types of treatment units most commonly used by rainwater systems are filters that remove sediment, in consort with either ultraviolet light or chemical disinfection. Filters A filter is an important part of the inflow structure of a RWH System. Once screens and roof washers remove large debris, other filters are available which help improve rainwater quality.  Gravity Based Filter  Sand Filters  Pressure Based Filter
  15. 15. From Where We Can Harvest Rainwater Rainwater can be harvested from the following surfaces:  Rooftops: If buildings with impervious roofs are already in place, the catchment area is effectively available free of charge and they provide a supply at the point of consumption.
  16. 16.  Paved and unpaved areas: landscapes, open fields, parks, storm water drains, roads and pavements and other open areas can be effectively used to harvest the runoff. The main advantage in using ground as a collecting surface is that water can be collected from a larger area. This is particularly advantageous
  17. 17.  Water bodies: The potential of water bodies such as lakes, tanks and ponds to store rainwater is immense. The harvested rainwater can be used not only to meet water requirements of the city; it also recharges ground water aquifers.
  18. 18. QualityConsiderationsinUtilizingRainwater It is generally believed that rainwater can provide clean, safe and reliable water which can be consumed without pre-treatment. This however may be used in some areas that are relatively unpolluted. Rainwater collected in many locations contains impurities. Therefore, in order to ensure quality of water, the collection systems will have to be properly built and maintained and the water shall also have to be treated appropriately for intended uses.
  19. 19. Lets Introduce A Sample Design Of Rainwater Harvesting system
  20. 20. PlanViewof Design Catchment area Gutter Discharge Pipe Sedimentation & filtration Chamber Dark & Close StorageTank
  21. 21. Design Data  City: Dhaka, Bangladesh  Rainfall Intensity : 2540mm annually(last 10 years )  Building Type: Residential (2 storied)  Number of people :18  Catchment Area: 2400 ft2 = 223 m2  Runoff Coefficient : 0.8  Storage Factor : 0.5  Pipe Dia= 9 inch  Filtration material : Local sand and Gravel (Recommended size)  & Filter paper
  22. 22. DailyDemand  Amount of water used for different Household activities (Activities Per capita consumption per day)  Bathing =18.9 liter  Drinking = 2.5 liter  Personal hygiene =2.9 liter  Kitchen =8.4 liter  washing clothes =27.7 liter  Toileting =6.7 liter  Cleaning Houses=12.1 liter  Others =4.0 liter  For all purposes = 83.2 lpcd
  23. 23. Available Rainwater  Q=CIA  =0.8*2540*10^-4*223  = 453 m3/yr  Loss (for flashing first water and others)  = 53 m3/yr  FinalAvailable Rainwater = 400 m3/yr  or, q= 60lpcd **Here we use rain water except Bathing ,Drinking & Personal hygiene. For more rain water we have to increase catchment area.
  24. 24. StorageTankDesign Volume V =0.365*18*60*.5=197.1 m3 =2121 cft (Length*wide*depth) =(16*15*9)cft
  25. 25. Cost  For installing this type of rain water harvesting system total costing is 75000 to 80000 taka.
  26. 26. Sourceof data:  Source of data: 1. Domestic water consumption patterns in a village in Bangladesh -by M. Al – Amin & K. Mahmud Islamic University of Technology, Gazipur, Bangladesh S. Hosen Dhaka WASA, Dhaka, Bangladesh M. Akhsanul Islam Public Works Department, Dhaka, Bangladesh 2. Water supply & sanitation By Md. Feroze Ahmed and Md. Mujibar Rahman 3. Bangladesh Meteorological Department , Bangladesh. 4. Water supply of Dhaka city: murky future the issue of access and inequality by A.F.M Azim Uddin Mohammed & Abdul Baten 5. MIST Rainwater harvesting project.
  27. 27. MIST Rainwater Harvesting Project.
  28. 28. THANK YOU