[PACKET_03_SUS]: THE BIO-SAND WATER STACK OBJECTIVE: Remove 90-99% of pathogens and particulates using local materials. I. THE LAYERING (TOP TO BOTTOM) You need a container at least 3 feet tall (barrel, PVC pipe, or large bucket stack). Standing Water (Top): 2 inches of water must always sit above the sand to keep the "Schmutzdecke" alive. Fine Sand: 20 inches. This is where mechanical filtration happens. Coarse Sand: 2 inches. Prevents fine sand from clogging the gravel. Fine Gravel: 2 inches. Coarse Gravel: 2 inches. Surrounds the outlet pipe. II. THE BIOLOGICAL ENGINE (SCHMUTZDECKE) Within 1-3 weeks of use, a slimy layer of beneficial bacteria (the Schmutzdecke) will grow in the top 1 inch of sand. Crucial: This layer eats harmful pathogens (Cholera, E. coli). Maintenance: Never let the sand dry out, or the biological layer will die. III. ASCII SCHEMATIC Plaintext [ BIO-SAND FILTER COLUMN ] |~~~~~~~~~~~~~~~~| <-- [1] INLET (Standing Water) |================| <-- [2] SCHMUTZDECKE (Active Layer) |::::::::::::::::| |:::: SAND ::::::| <-- [3] FINE SAND (20") |::::::::::::::::| |................| <-- [4] COARSE SAND (2") |oooooooooooooooo| <-- [5] GRAVEL (4") \________________/ || ||------------> [OUTLET] (Filtered Water) IV. PURIFICATION CHECKLIST Initial Run: The first 20-50 gallons will be turbid. Discard until clear. Flow Rate: Water should come out in a steady drip or thin stream. If it gushes, your sand is too coarse. Final Step: For 100% safety, combine this with SODIS (Solar Water Disinfection): Place filtered water in clear PET plastic bottles on a metal roof in direct sun for 6 hours. [ END OF PACKET // ARCHIVE_REF: 03-SUS-H2O-REV1 ]