What are they and how do they work?
The Colloidal Silver Impregnated Ceramic Water Filters (Silver Filters) consist of two parts: A simple, bucket shaped piece of pottery that is made with a mix of 95% clay and 5% sawdust and a 30-liter plastic or ceramic receptacle that stores and dispenses filtered water.
Colloidal Silver (CS) consists of microscopic particles of ionic silver suspended in water and is applied to the ceramic filters after the firing process. The silver acts as a broad-spectrum germicide, and in some cases, as a bacteriostatic that essentially deactivates bacteria as it passes through the ceramic filter’s pores: it thus renders the water potable.
It is believed that CS suffocates bacteria by disabling the particular enzyme that pathogenic bacteria and fungi use for oxygen metabolism. Other pathogens are destroyed by the electric charge of the silver particle, causing their internal protoplast to collapse. Others are rendered unable to reproduce. Parasites are killed while in their egg stage.
The effective filtration rate is between 1.5 and 3.0 liters per hour and, if the filter is scrubbed periodically with a soft brush, it will maintain this rate. In one study commissioned by Potters for Peace, the filters removed 100% total coliform, fecal coliform and E. Coli, and 94-100% of fecal Streptococcus. In homes with negative results for hydrogen sulfide producing bacteria and E-coli, no child had had diarrhea in the month prior to the study.†
Colloidal Silver is used widely to prevent scumming in water storage tanks, to sterilize and purify water aboard NASA’s Space Shuttle and on commercial airline flights.
For effective use in rural households, a program to introduce the Silver Filters requires basic Health/Sanitation Education, monitoring and follow-up.
Such Health/Sanitation Education would include how the filter works, water storage, acceptable cleaning procedures, hand washing, water borne pathogens, fecal transmission methods, etc. The filters themselves include cleaning instructions and a brush. The cleaning instructions include pictures to accommodate the low literacy rate among female participants.
†Investigation of the Potters for Peace Colloidal Silver Impregnated Ceramic Filter: Intrinsic Effectiveness and Field performance in Rural Nicaragua, December 2001, D.S Lantagne.