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Finding, Gathering, and Treating Water

Finding, Gathering, and Treating Water. Luke Miller Lindsay Ellis Abby Krich Xinning Zhang. Introduction. Water sources Water collection Water treatment Development vs. Relief. Water Sources. Groundwater (wells and springs) Surface water (fresh) Rainwater Other options.

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Finding, Gathering, and Treating Water

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  1. Finding, Gathering, and Treating Water Luke Miller Lindsay Ellis Abby Krich Xinning Zhang

  2. Introduction • Water sources • Water collection • Water treatment • Development vs. Relief

  3. Water Sources • Groundwater (wells and springs) • Surface water (fresh) • Rainwater • Other options

  4. Groundwater (Wells and Springs) • Requires least input • Energy efficient • Clean • Inexpensive • If ground sources are available, make use and/or make extreme efforts to not contaminate

  5. Groundwater: Wells • Requires pumping • Minimum of 50’ deep and 200’ from surface water to avoid contamination • Test drilling should be done to determine probable well productivity, depth, spacing, water quality, and location

  6. Hand Pumped Well http://www.unep.or.jp/ietc/Publications/TechPublications/TechPub-8a/instream.asp

  7. Spring Water Collection • most reliable source of natural filtered water in rural areas • If flow is less than 15 L/min a reservoir is not required • If storage is planned, the top of the storage tank must be below the eye of the spring for gravity feed.

  8. Spring Box If the slope is very steep or the spring has a large flow, if may be necessary to build a spring box. Normally the spring box is less than one meter by one meter.

  9. Surface Water (Fresh) • Many sites have an abundance • Rivers • Lakes • Streams • Should be used only when groundwater is not available

  10. Surfacewater Concerns Must investigate • Drainage areas • Rainfall, runoff, evaporation • Sanitary survey • Reservoir necessity • Downstream effects

  11. Surfacewater Problems Factors that can block intake • Floating Debris • Suspended Solids • Bed load

  12. Stream Intake and Settlement Stream intake and settlement in small mountain streams in Seychelles (UNESCO, 1991). http://www.unep.or.jp/ietc/Publications/TechPublications/TechPub-8d/instream.asp

  13. Tilted Perforated Plate http://www.lboro.ac.uk/departments/cv/wedc/papers/22/groupd/prakke.pdf

  14. Vertical Perforated Plate http://www.lboro.ac.uk/departments/cv/wedc/papers/22/groupd/prakke.pdf

  15. Rainwater • Should be a last-resort method • Requires extra construction of complex rain catchment devices • Roofs should also be made of material that will not contaminate the water (no metal, shingles, etc.) • Water supplies are limited and unpredictable

  16. Catching clean rain water is one of the most common and oldest methods for collecting safe drinking water. Rainwater Catchment System

  17. Other Options • If all else fails, freshwater can be extracted from seawater, brackish water, or water vapor in the air • Methods include reverse osmosis, electrodialysis, distillation, and vapor compression • All are complex, costly, difficult to operate and maintain, and present disposal problems • Let’s stay away from these

  18. SLOW SAND FILTRATION A LOW TECH SOLUTION TO WATER TREATMENT

  19. HISTORY • At the beginning of the 19th century, a Scotsman named John Gibb developed a way to provide clean water for his bleachery. Gibb built a built a water treatment plant that utilized the slow sand filtration technique, which is now regarded the oldest type of municipal water filtration.

  20. Possibilities • Slow sand filters continue to provide a cheap and relatively easy way for obtaining potable water. • They may be a suitable water treatment choice for rural communities.

  21. How the filter works • Raw water percolates very slowly through the bed of uniformly porous sand. • As raw water filters down the bed, a layer of microorganisms begins to form in the tops few millimeters of the filter. • In a mature filter, this rich, sticky, mat-like biological layer is called a Schmutzedecke. • The microorganisms break down and feed off of organic matter in the water. Inorganic particles are trapped in this layer as well, possibly by adsorption.

  22. A combination of physico-chemical and biological mechanisms are involved in the filtration process. Biological mechanisms are not yet fully understood. • Depending on the raw water quality, cleaning of the filter bed will be necessary after a few weeks or months to prevent clogging. This is done by scraping off only the top inch.

  23. Capacity • The capacity of a slow sand filter depends mainly on the filter surface. • The recommendations are in the range of 100 to 300 L per m2 and hour m2 (25 – 75 gal/sq. yd. per hour).

  24. Figure 1. Typical cross section of a slow sand filter.

  25. There is a minimal amount of maintenance work (most time consuming is scraping off the top layer). COST of materials and operation. Materials can be found locally. No known negative impacts to the environment, as of yet. Energy consumption is low. No pre-treatment chemicals are needed. Advantages

  26. Need a lot of land and filtration materials to produce significant amounts of treated water. Raw water turbidities need to be low so that the filters are not clogged too quickly. Filters treat cold water less effectively due a smaller population of microorganisms. Raw water needs to contain nutrient content for the Schmutzedecke to form. Organic chemicals are not completely removed. Disadvantages

  27. Table 1. Typical Treatment Performance of Conventional Slow Sand Filters

  28. Table 1. Continued

  29. Conclusions • Slow sand filtration is a practical and low cost method for treating water. • Slow sand filters are easy to construct and require a minimum amount of maintenance.

  30. References • http://www.drilleronline.com/CDA/ArticleInformation/features/BNP__Features__Item/0,3643,76891,00.html • http://www.mnd.fh-wiesbaden.de/fag/bio/pf/pfSFengl14.html • http://www.cee.vt.edu/program_areas/environmental/teach/wtprimer/slowsand/slowsand.html • http://www.refugeecamp.org/learnmore/water/slow_sand_filter.htm • www.sungravity.com • www.nps.gov/dsc/dsgncnstr/gpsd/toc.html

  31. Instructions for building a slow sand filter: • http://www.refugeecamp.org/learnmore/water/slow_sand_filter.htm

  32. Development rather than relief • Relief • Immediate but temporary help for times of disaster • Easier, so you can help more people • Development • Slower, but lasting • Concerned not so with helping people have more, but helping them be more • Long-term goal of sustainability

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