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Point-of-Use Membrane Ultrafiltration (The DROP Filter® & Sawyer PointONE)

Hollow-fiber membrane (HFM) ultrafiltration filters pass raw water through thousands of microscopic U-shaped capillary tubes with 0.1-micron (100 nanometer) absolute pore sizes. They establish a physical, chemical-free barrier against pathogenic bacteria, protozoan cysts, and microplastics.

Technical Specifications

  • Pore Size: 0.1 Micron absolute (100 nanometers).
  • Filtration Efficacy:
  • 99.99999% (7-log) Bacteria removal (Vibrio cholerae, Salmonella, Escherichia coli, Campylobacter).
  • 99.9999% (6-log) Protozoan cyst removal (Cryptosporidium parvum, Giardia lamblia, Entamoeba histolytica).
  • Gravity Flow Rate: 1.0 to 1.5 liters per minute (under standard 20-liter bucket hydraulic head).
  • Engineering Lifespan: Up to 10 years (1 million+ gallons) with regular maintenance and backwashing.
  • Unit Cost:
  • The DROP Filter® (Wine To Water): $40 USD per complete bucket adapter kit.
  • Sawyer PointONE Household Kit: $45–$60 USD per complete household assembly.

Field Care, Cleaning & Syringe Backwashing Protocol

To ensure a membrane filter achieves its 10-year operating life, community committees and mothers must be trained on the standard three-step maintenance protocol:

1. Routine Syringe Backwash (Weekly or when flow slows)

  1. Fill the 60mL Cleaning Syringe with previously filtered, clean drinking water. Never use raw turbid water to backwash.
  2. Firmly press the syringe tip against the clean-water output nozzle of the filter cartridge.
  3. Depress the syringe forcefully in a quick, assertive stroke to blast clean water in reverse through the hollow fibers.
  4. Repeat 3 to 5 times until the water exiting the intake hose runs completely clear of expelled silt and biofilm.

2. Deep Sanitization Soak (Monthly or after heavy river silt)

  1. Prepare a cleaning solution of 5 liters of clean water mixed with 1 capful (approx. 5mL) of unscented household bleach (yielding ~20–30 ppm free chlorine).
  2. Push 60mL of the chlorinated water in reverse through the filter using the syringe.
  3. Allow the filter cartridge to sit immersed in the solution for 15 to 20 minutes to dissolve organic slime, algae, and microbial biofilm.
  4. Flush thoroughly with 1 liter of fresh filtered water before returning to daily drinking service.

3. Protection Against Fiber Damage & Freezing

  • Freeze Hazard Warning: If water freezes inside a hollow-fiber cartridge, ice expands and punctures the 0.1µm membrane walls, permanently ruining the filter. In high-altitude or sub-zero climates, keep filters indoors or against body warmth.
  • Integrity Test (Syringe Back-Pressure Check): If a filter has been dropped or suspected of freezing, fill a syringe with air, attach to the wet nozzle, and attempt to push air through into a glass of water. If large continuous bubbles stream freely at low pressure, the fiber walls are compromised and the cartridge must be replaced.

Community Multiplier Model (The "Water Woman" / Cluster Approach)

  • In dispersed smallholder communities where piping is unaffordable, equipping one host mother with a bucket filter kit ($40–$80 USD) to purify drinking water for 3–4 neighboring households (~20–25 people) drops capital costs to just $2.00–$4.00 per person.
  • Daily Flow Schedule: Purifying 100 liters of drinking water for 4 families takes approximately 1 hour and 15 minutes of gravity flow each morning.
  • Sharing Covenant: Success requires host mothers to sign an agreement committing to weekly backwashing, while neighbor families contribute local soaps or cleaning labor.

Video Demonstrations & Field Training Resources

Official Filter Care & Assembly Videos

  • 📺 Wine To Water Video Training Portal: Wine To Water YouTube Channel — Demonstrates community filter distributions, bucket installations, and field backwashing in the Amazon, East Africa, and post-disaster zones.
  • 📺 Sawyer PointONE Bucket Assembly & Syringe Backwash: Sawyer Bucket Filter Field Training Video — Comprehensive 4-minute demonstration of drilling a standard 20-liter bucket, attaching the food-grade silicone bulkhead gasket, priming the membrane, and forceful reverse syringe flushing.
  • 📺 CAWST Household Water Treatment & Safe Storage (HWTS): CAWST Educational Training Series — Open-source training on multi-barrier water treatment and preventing secondary recontamination during transport and storage.

Downloadable Field Documentation (Wine To Water)

Community Facilitator Lesson Plans & Teaching Toolkits (CAWST)

  • 📖 Multi-Barrier Water Treatment & Safe Storage Lesson Plan: Download HWTS Lesson Plan — Turn-key 45-minute lesson plan for field trainers teaching rural mothers how hollow-fiber membranes fit into the multi-barrier approach (protection, sedimentation, filtration, disinfection, safe storage).
  • 📖 How to Clean Safe Water Storage Containers (Pictorial Lesson): Download Container Cleaning Guide — Illustrated step-by-step lesson plan on sanitizing kitchen jerrycans with soap and clean pebbles to eliminate secondary pathogen recontamination.
  • 🃏 Household Water Treatment Methods Comparison Activity: Download Facilitator Flashcards — Interactive card-sorting activity for village workshops comparing membranes, chlorination, BioSand, and SODIS on cost, flow rate, and pathogen removal.