Hydraulic Properties Investigation of the Potters For Peace Colloidal Silver Impregnated Ceramic Filter



Christopher J. Fahlin
Undergraduate Independent Study Research
University of Colorado at Boulder
College of Engineering
Advising Professor: Dr. Angela Bielefeldt
March 7, 2003


This study investigated the hydraulic properties of the Potters For Peace filter in greater detail than previous studies by Sten Eriksen and Daniele Lantagne. Hydraulic properties such as the hydraulic conductivity and tortuosity are important because they help determine the contact time of pathogens in the water with silver to provide inactivation. Two laboratory tests were conducted using both experimental and numerical methods for attaining the results. Unfortunately, the hydraulic conductivity results were questionable for many reasons and the tortuosity results varied considerably due to the porosity variability results. This research does not conclusively describe the hydraulic properties for the PFP ceramic filter, but it does have model improvements and many recommendations for future research. Future work resulting from this research will hopefully lead to accurate and conclusive results about the hydraulic properties of this economically feasible and effective filter.

Engineers Without Borders, Potters For Peace, Filtrón, Appropriate technology, ceramic filter, colloidal
silver, developing countries, drinking water, point-of-use treatment.

Ceramic Water Purifier Cambodia Field Tests

IDE Working Paper No. 1
October 2003
Michael Roberts, M.S.
International Development Enterprises


This report summarizes results from a year-long pilot project in Cambodia to test the Ceramic Water Purifier, a low-cost household water treatment technology that removes microbiological contamination at the point of use. The pilot project was conducted by International Development Enterprises (IDE) with financial assistance from the Health and Nutrition Initiatives Fund supported by the Canadian International Development Agency (CIDA).

The Ceramic Water Purifier (CWP) consists of a porous, pot-shaped filter element made of kiln-fired clay and impregnated with colloidal silver. The ceramic filter element is set in a plastic receptacle tank with a lid and a spigot. Raw water is poured into the filter element and seeps through the clay producing potable water at a rate of 2 to 3 litres per hour. The filter element holds approximately 10 litres, allowing a family to produce 20 to 30 litres of water
per day with two to three fillings. Monthly maintenance consists of scrubbing the ceramic filter element to unclog pores and washing the receptacle tank and spigot to prevent bacterial growth. The current cost of the CWP is approximately $7.50 for a complete unit (including manufacturer and retailer profit but not including transportation) and approximately $4.50 for the filter element alone, which needs to be replaced about once every two to three years.

Comparative Analysis of the Filtron and Biosand Water Filters

William F. Duke, MD,1* Rick Nordin2 and Asit Mazumder2

1University of Victoria, Restoration of Natural Systems Program , Victoria, British Columbia,
2University of Victoria, Department of Biology, P.O. Box 3020 STN CSC, Victoria, British Columbia

* Corresponding author;


For many of the 1.1 billion people who now lack access to safe water, affordable water filters designed for use in individual households provide a practical alternative to municipal water treatment systems. Two of the most commonly promoted filters in developing countries are the Filtron ceramic filter and the BioSand intermittent slow sand filter.

To compare the performance of these two filters, pond water was put through each filter for 30 consecutive days. Turbidity, TOC, DOC, E. coli and total coliform counts were recorded daily for the source water and for the filtered water from each filter. Flow rates and frequency of cleaning were also recorded for each filter. Both filters lowered the turbidity, TOC, DOC, and bacterial counts significantly.

The Filtron filter was more effective in removing bacteria, but it was limited by flow rates of only 1-2 liters per hour as well as the need for frequent cleaning. The biosand filter produced flow rates of about 20 liters per hour and did not require cleaning during the study period, but it was less effective in removing bacteria.

Colloidal Silver – Briefing

Colloids are submicroscopic particles of material suspended in a liquid. Silver is converted to colloidal
silver by running a positive electrical current through bars of pure silver suspended in water. The size of
colloidal silver particles is generally between .015 – .005 microns. Upon becoming a colloid, silver takes
on a positive ionic charge.

The mechanism by which silver accomplished the disinfection of bacteria was first termed �oligodynamic�
referring to the fact that it�s qualities may be observed even when present only in extremely limited
quantities. Silver reacts strongly with thiol (sulphydryl, SH) groups in both functional and structural
proteins of the bacterial cell. Research indicates that silver inhibits glucose, succinate, and lactate
oxidation (dehydrogenation), possibly by means of an uncoupling effect. Zimmerman (1952) had already
demonstrated that low concentrations of silver do not enter the cell. Rather, they are adsorbed onto the
bacterial surface just as silver tends to adsorb to other surfaces thus silver ions immobilize
dehydrogenation because respiration occurs across the cell membrane in bacteria rather than across the
mitochondrial membrane as in eukaryotic cells.

Prior to 1938, when patentable antibacterial drugs began to be developed, colloidal silver was a
mainstream antibacterial agent in the US. It is still widely used to prevent scumming in water storage
tanks. It is used to sterilize water aboard NASA’s Space Shuttle program. Many airlines companies
routinely use colloidal silver for in-flight water purification. Today interest in colloidal silver as a powerful
home remedy, as well as an effective water purifier, is at an all time high.

Many colloidal silver enthusiasts recommend this material as a safe topical and internal cure-all for a wide
variety of maladies. Some encourage daily ingestion of colloidal silver as a preventative measure. Others
warn consumers of self-interested marketing efforts designed to cash in on whatever the latest personal
health fad might be. Warnings are posted as to possible toxic side effects which could result from the
buildup of silver in the bloodstream.

Potters for Peace takes no position on the claim of colloidal silver’s effectiveness as an antibacterial agent
to be directly ingested in relatively large daily, or regular doses. Our interest is strictly focused on the
historical and well-documented application of colloidal silver as a safe and effective water purification
agent used in conjunction with various filtration and storage methods for both large and small water

Colloidal silver is not listed as a toxin by the Environmental Protection Agency’s Poison Control Center.
Likewise, the Food and Drug Administration has no regulations regarding the use of colloidal silver as an
antibacterial in any form or method, although due to the recent upsurge of interest in this material, many
believe some sort of guidelines will be forthcoming.

The toxic side effect, mentioned previously, resulting from a buildup of silver in the bloodstream is known
as “Argyreia;” a blueish-grey discoloration of the skin. Medical science recognizes Argyreia as specifically
caused by intensive long-term exposure to silver compounds, such as silver nitrate, silver sulfate, silver
sulfadiazine, etc., not from micro-particles of ionic silver.

The Filtron employs colloidal silver through a one time initial saturation of the filter medium by a .32%
solution in approximately 200 grams of water. See Test Request for application details. It is highly
recommended that the filter medium be periodically cleaned (at least annually in case of high turbidity
levels in the source water) and re-saturated with colloidal silver. On-going studies are focused on
determining a more or less exact timetable of filter medium renewal, but the longest (albeit unscientific)
study yet indicates that after 15 years the filter is still doing it’s job.

Although the total amount of colloidal silver used in the Filtron is relatively minute, it is still
possible that even smaller trace quantities of the material could pass directly into the filtered
water. To date, no medical study conducted on colloidal silver has indicated that it poses a
threat to human health. In his “Case Study of 30 Years of Use with Silver Disinfected Drinking
Water” (1983), Michael Owen states that “Colloidal silver does not appear to be readily
absorbed by the human body. Excess silver deposited in the stomach is precipitated as silver
chloride by the stomach bile, and almost immediately excreted through the feces.”

For a more detailed description of the properties of colloidal silver, refer to the following
documents;”A Closer Look At Colloidal Silver,” by Peter A. Lindemann, and “A Brief History of
ColloidalSilver,” by Dr. Gary Smith; �Antimicrobial Activity and Action of Silver�, Progress in
Medicinial Chemistry, Hugo Russel, Elsevier Science B.V. Vol 31, 1994; Drinking Water and
Health, Vol. 2 National Academy Press, Washington D.C. 1980.

Evaluating the water treatment effectiveness of the Filtron


Angela R. Bielefeldt
Associate Professor, Dept. Civil, Environmental, & Arch. Engineering
University of Colorado – Boulder

Professor R. Scott Summers,
Chris Fahlin, Suzanne Givler, Kate Kowalski,
Katie Medina, Lucas Hollenkamp,
Anisha Malhotra, Heather Wright


Research Questions
• Hydrodynamic conditions during flow
– Contact time of pathogens with silver
• Physical removal vs Inactivation
– Filtration (and impacts of accumulated dirt within the
filter); if inactivation, potential for reactivation / repair
• Necessary to “pre treat” very turbid water?
– Particles clog filter too rapidly and decrease flow rate
• Quantitative understanding of colloidal silver’s
ability to kill bacteria and viruses
– “CT” concentration * contact time relationship?
– Long term effectiveness, as silver leaches away
– Bacterial “static” vs “cidal” – bioclogging over time?

Cambodian Filter Factories Study


Resource Development International Cambodia (RDIC)
Mickey Sampson / Marc Hall

Resource Development International (RDI) is a faith-based NGO with bases of operation in Kean Svay and Siem Reap, Cambodia, although the reach of their programs is nationwide. RDI believes that its role is to provide resources to the development world as well as the developing world, a policy that is through their eagerness to share manufacturing details, marketing materials, and educational strategies.


Cambodian Red Cross (CRC)
M. Sichan / Mao Song (Factory Manager)

The Cambodian Red Cross water filter factory is the newest ceramic silver filter operation in Cambodia. It was begun in early 2005, and build according to advice provided by IDE based on RDI’s findings. The pilot project and the factory construction were originally funded by the World Bank’s Development Marketplace Competition and by the American Red Cross1.

Analysis and Comparison of Sustainable Water Filters


Skye McAllister
Department of Mechanical Engineering
University of Wisconsin – Madison
May 4, 2005

In 2001 the United Nations declared clean water a “basic human right,” and set a goal to halve the
number of people without access to clean water and sanitation by the year 2015. There are currently
thousands of types of water filters on the market with the ability to purify water contaminated in
many different ways. However, most of these filtering methods are too expensive and don’t meet
the specific needs of many unindustrialized nations of the global south. Such organizations as the
United Nations and World Health Organization are currently pushing the water filter industry to
develop sustainable solutions to empower many unindustrialized nations with the ability to filter
their own water. These sustainable technologies are innovative, simple, and incorporate
combinations of basic science and local materials to create usable and efficient filters. It is the goal
of this report to investigate the different sustainable water filter technologies, determine a set of
guidelines for creating sustainable filters, and then give suggestions about the specific technologies
that will help best meet the UN goal.

Keywords: sustainable, water filter, global south, United Nations, World Health Organization.

Investigation of the Potters For Peace Colloidal Silver Impregnated Ceramic Filter

In September 2001, Jubilee House Community contracted with USAID to provide intrinsic and field investigations of the Potters for Peace (PFP) colloidal silver impregnated ceramic filter. Daniele Lantagne, MIT Lecturer in Civil and Environmental Engineering and Principal of Alethia Environmental, was hired to complete the work. Ms. Lantagne spent three weeks in Nicaragua in October 2001 conducting experiments on the filter and sampling water quality in homes using the filter. Further research was conducted in November and December 2001 with filters that were transported back to the United States.

Report 1: Intrinsic Effectiveness
Daniel S. Lantagne
Alethia Environmental
Executive Summary of Report 1

Report 2: Field Investigations
Daniel S. Lantagne
Alethia Environmental
Executive Summary of Report 2

Analysis of Filtered Water for Barium

Attached is the first part of the report from  Dr. Kingsley Donkor and Megan Campbell of the Thompson Rivers University Chemistry department analyizing water from the first of two filters that were brought to be evaluated for the possiblility of problems with Barium in clay used to form filters. These results are for the new 100% Plainsman red earth filter. You can read the report but essentially even analysis of a un flushed filter shows the barium level to be one third of the allowable limit initially and then  reduced to one third of that level very quickly.

Continue reading “Analysis of Filtered Water for Barium”

Marketing Safe Water Systems – By Urs Heierli

Why It Is So Hard To Get Safe Water To The Poor – And So Profitable To Sell It To The Rich?

Why is it that the global market for bottled water is booming, with astounding annual growth rates, sometimes as high as 50 per cent, and why is the progress in providing safe water to the poor so sluggish ? Why do more than 300 children still die of diarrhoeal diseases every hour ?
It is not for the lack of affordable solutions. Solar disinfection, chlorination, filtration by slow-sand and ceramic filters, and ultraviolet treatment are all effective methods and have been scientifically proven to reduce child mortality considerably.
For some years the right solution seemed to be to provide piped water to all households, with ‘ Point of use water treatment and storage systems ‘ ( POUs ) considered either unnecessary or merely intermediate solutions. However, of late, two factors have put POUs much higher on the
development agenda :
1. First, many poor people will have to wait for quite some time until they get access to piped water, and they need a solution now.
2. Second, even if piped water is available, it can be contaminated or re-contaminated on the way to the user, either by leaks in the piped system or by re-contamination during transport and storage.
There is thus a huge need for POUs that treat water and make it safe just before it is consumed. Several studies have shown that diarrhoeal diseases can be reduced considerably when sanitation and hygiene standards are improved.
POUs lack good dissemination and marketing strategies.
Many POU systems are poorly marketed and have considerable deficiencies in respect of the five Ps of marketing :
1. The products are not very suitable, practical or well designed. If anything, they are practical but do not look like ‘ must-have ‘ products.
2. The pricing of POUs is not attractive for either buyer or seller. While mobile phones can be paid for in instalments while being used, water filters need to be paid for upfront in cash.
3. There is no obvious point-of-sale to buy POUs because there is no money in it for retailers.
4. Promotion leaves much to be desired, even when it is present, despite the fact that safe water may require
behavioural changes.
5. People ( the 5th P ) do not automatically put safe water high on their agenda, and there is very little continual social marketing to influence them. They claim they do not have 10 dollars to buy a filter but may spend much higher amounts on beer, cosmetics and other less-essential consumer goods.
For POUs to take hold would require a marketing campaign similar to that used with insecticide-treated mosquito nets. This means a concerted and comprehensive action programme involving the public and private sectors to bring about change and to scale-up dissemination from tens of thousands of POUs per year to tens of millions. We hope that this book provides inputs and suggestions for bringing POUs to that other, higher, level of dissemination. This will only be possible if the level of funding inputs is comparable to that used for mosquito nets.

François Muenger
Senior Water Advisor
SDC Swiss Agency for Development
and Cooperation

Author : Urs Heierli is an economist ( Ph.D., University of St . Gallen ).
From 1987 to 1999 he served as country director of SDC – the Swiss
Agency for Development and Cooperation in Bangladesh and India.
During a subsequent sabbatical, he wrote the study ‘ Poverty Alleviation
as a Business ‘ and then joined the Employment and Income
Division at SDC head office in Berne. In November 2003, he launched
his own consulting company, msd consulting ( Markets, Sustainability
and Development ) in Berne, to focus further on the market creation
approach to development.

Foreword : François Muenger, Senior Water Advisor, SDC
Peer review: Armon Hartmann, former Senior Water Advisor, SDC
Editor : Paul Osborn, Médiateurs, Netherlands
Photos : Urs Heierli, Population Services International ( Waterguard ),
G . Allgood, Procter & Gamble ( PUR Photos ), Antenna Technologies
( WATA photos ), SODIS Foundation ( SODIS new designs ).
Design/layout : Claudia Derteano, Isabelle Christ
Copyright : SDC – Swiss Agency for Development and Cooperation,
Employment and Income Division / Urs Heierli ( msd consulting ),

1st Edition : September 2008, printed in India

Copies : Hard copies are available from :
SDC Social Development Division ( sodev@deza.admin.ch ) and
SDC Employment and Income Division ; ( e-i@deza.admin.ch )
Electronic copies can be downloaded from :
www.deza.admin.ch/themes ; www.poverty.ch/safewater ;

Film clips : A companion CD with many film clips is in the back
cover of this book. The clips are also available for download from

This publication is supported by :
Employment and Income Division and
Social Development Division
SDC – Swiss Agency for
Development and Cooperation
Freiburgstrasse 130
CH-3003 Berne

This publication is co-published by :
Antenna Technologies
29, rue de Neuchâtel
CH-1201 Geneva

Connect International :
Jan van Houtkade 50
2311 PE

Download complete document:  Safewater.pdf 5.32MB

Diagram for a screening machine

Attached are two images and one sketchup file describing the components of a simple mostly wooden machine for screening materials (such as sawdust).




The sketchup file viewer program is necessary for viewing the sketchup 3D CAD diagram, you can download various versions of it here: http://sketchup.google.com/gsu6/download.html

IDEASS filter publication

Innovation for Development and South-South Cooperation (IDEASS Nicaragua)
This is a presentation by Ron Rivera combining many areas of supportive research towards CWF Filtron.
12 pages, useful images, bacteriological test chart, sanitation methods comparison chart, manufacturing process explained.

Download pdf document 308kb : UN filter publication.pdf

Capabilities and Short History of the Filtron Design Ceramic Water Filter (CWF)

The water filter design that is now used in Nicaragua was invented by a Guatemalan chemist, Fernando Mazareigos.   This design was the first that we know of where the capabilities of a ceramic filter were combined with the antimicrobial capabilities of colloidal silver. 

 In 1981, the InterAmerican Bank financed a comparative study to determine which of ten appropriate technology filters best met the following criteria:


 Has a sufficient flow rate for home use

 Is effective at removing bacteria

 Is simple to manufacture

 Can be made with available materials

 Can be made and sold at low cost

 Contributes to economic activity at low-income level

 Ease of distribution

Download Full Document: Capabilities of the Filter.doc

Problems in the Field and Solutions

The most basic of all problems with regard to “filter” use comes from the choice of words. In some information given out by PFP/Filtron, and in studies conducted in the field, clear distinctions were not made between the filter element (the filter that is made of clay and coated with colloidal silver), the receptacle (the plastic bucket or clay receptacle in which the filter element sits), and the complete product called Filtron in this manual…

Download Full Document: Problems in the Field.doc

Potable Water, Purified Water, and Water Treatment Processes

Potable Water can be described as all water used for human consumption that does not pose a health danger and which is microbiologically safe and free of all pathogenic microorganisms and bacteria associated with fecal contamination. In the United States, according to the U.S. Environmental Protection Agency (USEPA) it is water with (0) fecal coliforms, (0) Giardia lamblia, (0) Legionella, (0) enteroviruses. According to the World Health Organization (WHO) Guidelines for Drinking Water Quality (2002), “E.Coli or thermotolerant coliform bacteria must not be detectable in any 100 ml sample.” It can be produced by any method or can be naturally occurring.

Download Full Document: Methods of treatment Point of use.doc

Diarrhea and Its Causes

Diarrhea can be defined as the passing of frequent, loose or watery stools more than four times a day (SAFETI Adaptation of Peace Corps Resources). Diarrhea is, in effect, the effort of the body to expel the disease-causing microbes.

In order to survive and cause disease in the body, pathogenic bacteria must remain there and multiply. The cells of the gastrointestinal tract, the respiratory tract and the genito-urinary tract are covered in mucus membranes. A thick layer of mucus helps prevent penetration of bacteria. Mucus membranes are constantly flushed by fluids that prevent bacteria from becoming established, move bacteria through the system, and kill or inhibit growth. Natural antibodies and fever also kill pathogenic bacteria.

Download Full Report: Diarrhea and its Causes.doc

Follow Up Field Report

Report on follow-up training to accompany Filter projects in the field.

Potters for Peace and the Filtron workshop in Nicaragua have produced over 20,000 colloidal silver impregnated ceramic water filters (Filtrons). The majority of these Filtrons were purchased and distributed by non-governmental organizations (NGOs) throughout rural Nicaragua. The Filtron consists of a filter that sits in a clay or plastic receptacle. Though laboratory testing of the ceramic filters showed a consistent 98% to 100% removal of bacteria, field studies revealed bacterial recontamination of water in up to 80% of water sampled from the filter receptacles. This can be largely attribute to bad cleaning practices, incomplete or inaccurate training of NGOs distributing the filters, and a general lack of understanding on the part of both rural health promoters and users about how the filter works, required maintenance, and the nature and origin of waterborne disease.

Download full document: Field report on filters use.doc

Colloidal Silver – Background

Silver has been used as a medicine and preservative by many cultures throughout history The Greeks used silver vessels for water and other liquids to keep them fresh.Silver was used by the Romans to preserve water in storage jars. During war campaigns Alexander the Great boiled and stored water in silver or bronze urns to reduce waterborne disease.

Silver was used as a medicine in the late 1800’s and early 1900’s. Silver, along with other metals was discovered to possess microbicidal properties but silver alone showed both strong microbicidal properties and low or no toxicity to humans. The colloidal state proved to be the most effective form because it lacked the caustic properties of salts (such as silver nitrate) and demonstrated a high level of activity with very low concentrations (oligodynamic). In 1881 silver nitrate was first used for the prevention of gonorrhea. In 1884, the German obstetrician F. Crede administered 1% silver nitrate to the eyes of newborn infants, virtually eliminating the incidence of disease-caused blindness in newborns. When antibiotics came into widespread use in the 1930s, the use of colloidal silver was dropped.
Download full document: Colloidal Silver1.doc

MIT Thinkcycle PFP Filter Evaluation


During the last decade, several projects tackling water treatment for low-income households have likely failed due the utilization of inappropriate technology or deficient monitoring. Our team has used a system that ensures a bi-directional transfer of technology and knowledge for water purification at a household level. Through an innovative methodology design based on an iterative and real-time feedback loop, we have been able to establish solid partnership with key players in the field who have implemented a 6-month monitoring program in order to assess the performance of Potters for Peace ceramic water filters. Microbiological performance of the filter in the filter was promising but did not meet WHO targets. Survey results suggest that periodic training and constant monitoring is essential to ensure the appropriate use and successful implementation of this new technology.

Download Full Document:  MIT thinkcycle PFP filter evaluation.doc

Zamorano Harvard Report

Household Water Filters as part of the Kitchen Improvement Project

(Cocinas Rurales)

PROMESA is a small international health program that has been working to improve the conditions in the Yeguare region of Honduras for the past four years. Currently PROMESA is working on a kitchen improvement project in four small communities (La Ciénega, Las Tablas, Las Agujas, and Rodeo) in the region. This project’s focus is to improve the health status of the families by improving the health standards in the kitchen by offering materials to improve earth stoves, install drains, sinks, install mesh on windows, and install concrete floors. One improvement that was offered to the families in the communities was a household size water filtration system to purify contaminated water. There are a variety of filtration systems; however, it was necessary to find an inexpensive, functional, and long lasting system. One filter that met those requirements was the Filtron.

The Filtron is a ceramic filter that is marketed by Potters for Peace and is one method to decontaminate water that is used for human consumption. The filter works in two ways: as a filter to remove large contaminants such as protozoa, helminthes, etc., and as a disinfectant by using colloidal silver to clean the water of potentially harmful bacteria. The silver is spread on the sides and bottom of the filter. Water passes through the pores that are formed in the manufacturing process. When the water passes through these pores it comes in contact with the colloidal silver, which acts as a bactericide. The filter is an alternative to chlorination, boiling, or using solar energy to decontaminate water (1).

Download full document:Zamorano Harvard report.doc