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Biological Sand Filtration by Brian Koser

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Presentation on sand filters and creating your own sand filters. The presentation also gives an overview of water emergency preparation.

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Biological Sand Filtration by Brian Koser

  1. 1. Biological Filtration Sand Filters 101
  2. 2. What is a Biological Filter ● Mechanical trapping of particles and pathogens ● Predation of pathogens by organisms living in the filter ● Adsorption where organisms clump together and bind to the sand layer ● Natural deaths where pathogens finish their life cycle and cease multiplying
  3. 3. Basic Sand Filter Parts ● ● ● ● ● ● Input Schmutzdecke Sand Layer Activated Carbon (optional) Gravel Layer Output
  4. 4. Schmutzdecke! This is the active biological layer at the top of the sand filter. It does the work by trapping and breaking down pathogens. ● Bacteria, fungi, rotifers, algae,and protozoa ● Do keep it. ● Don’t disturb it - slow flow...
  5. 5. Sand! ● Provides a substrate for the biofilm layer ● Use different particle sizes ● Needs to be exchanged periodically
  6. 6. Activated Carbon- What is it? This is highly porous charcoal. It is useful because it can bind chemical impurities through adsorption. The contaminants are locked up, but the carbon needs to be changed out periodically, in order to remain effective.
  7. 7. Gravel Layer This layer keeps the sand in the filter, and allows the water to come out - slowly…
  8. 8. Outflow and Storage
  9. 9. Other Sand Filter Plans… ● Surfers Without Borders Slow_Sand_Filter ● CAWST Biosand Filter ● National Drinking Water Clearing House Slow Sand Filter
  10. 10. Sunlight Ultraviolet light is pretty good at killing pathogens, but takes time, and is not guaranteed.
  11. 11. Water Testing How safe is this water…?
  12. 12. Water Testing The most basic test - sight and smell...
  13. 13. Water Quality Measures ● ● ● ● ● ● ● Turbidity TDS - Total Dissolved Solids Ph Level - Neutral is best Nitrates Fecal Coliform Biochemical Oxygen Demand Phosphorous
  14. 14. Testing for Everything…? It’s difficult to test for everything for a number of reasons: ● Cost - Example Price List Water and Wastewater ● Technology ● Identification Know your source!
  15. 15. Streamer
  16. 16. Commercial Tests Home test kits range between $9 and $40 for a single use. Commercial lab kits cost more (~$1000), and will not test for everything...
  17. 17. Emergency Preparedness How to be ready
  18. 18. How Much Water Do I Need? ● Minimum: One gallon of water / a person /a day ● Hot outside? - double that - two gallons / day ● Consider how long it will be before another source of water becomes available (keep at least three days worth).
  19. 19. How Should I Store It? ● Keep it in a cool, dark place. ● Keep the water sterile (covered and sealed). ● Replace it every six months.
  20. 20. Purifying Water In a Pinch 1. 2. 3. 4. 5. Boiling…(160 degrees for 30 minutes) Bleach… (~two drops per a quart) Iodine Tablets…(usually two tablets / quart) Solar Stills… Portable Water Filters...
  21. 21. Food! Don’t forget about food - you need at least three days / person in your household. ● Dry or canned goods keep best. ● Avoid salty foods if water is an issue.
  22. 22. Other Things to Consider... The best resource in an emergency is community. Charleston Rain Catchers (Facebook Group)
  23. 23. Resources Appropriate Technology, Development Wiki - EPA Guide to Home Water Testing Filter Design and Construction - How to Filter Water with a Sand Filter - Iodine Tablets - Water Emergency Preparation - Water for the World -