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Choose topic: Introduction Types of Filters Performance Parameters Pros/Cons Prices Weblinks

Introduction

Ceramic water filters have been used in various places around the world as a means of treating drinking water at the household level. The fact that ceramic filters can be manufactured and produced by local ceramists with local materials makes them particularly attractive as a household water treatment technology that is affordable, appropriate, and sustainable. Some examples include the Potters for Peace Filtron (Nicaragua), the TERAFIL terracotta filter (India), and the candle filter (India, Nepal, Bangladesh, Brazil, etc).

Although the use of ceramic water collection and storage vessels goes back centuries, there is little documentation and testing of the effectiveness of low-cost ceramic water filters both in the laboratory and especially in the field in developing countries.

What research has been done suggests that the commercially available ceramic water filter systems in places such as India, Nepal, Nicaragua, and Brazil are a step in the right direction, but could be improved to better meet the safe drinking water needs of citizens. In particular, many commercially available filter systems are too expensive for the poor who are suffering the most from waterborne diseases.

Several organizations, including MIT, are currently pursuing laboratory and field research on the effectiveness of ceramic water filters. This year, the MIT Nepal Water Project continued research on the feasibility of developing a new disk-filter prototype that could potentially eliminate some of the problems associated with existing filters, at a retail price that is affordable to the poor.

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Types of Filters

Ceramic water filters can be categorized according to various key parameters:

1. Shape (e.g.: candle element, disk, pot) (see diagram at below);
2. Type of clay (e.g.: white kaolin, red terracotta, black clay…);
3. Combustible material (e.g.: sawdust, flour, risk husk…).
   

Ceramic water filters can also be described by their function(s):

1. Microbial removal (e.g.: Potters for Peace Filtron);
2. Chemical contaminant removal such as arsenic and iron (e.g.: 3 Kolshi filter for arsenic) (Hurd, 2001; Tabbal, 2003);
3. Secondary contaminant removal like taste and odor (e.g.: Katadyn® Gravidyn ceramic candle filter with activated carbon).

Other key variables that influence the properties of ceramic water filters include:

1. Use of additional materials in production (e.g.: grog, sand, combustible materials…);
2. Firing temperature;
3. Mode of production (e.g.: hand mold, wheel, mechanical press).
   

The entire filter unit is often defined in terms of two components: the filter element or media through which water passes and the filter system which houses the media, usually consisting of an upper and lower storage vessel for holding water (see diagram at below).

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Ceramic Filter System

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Performance Parameters

Ceramic water filters can help improve water quality in terms of:

• Microbial removal
• Turbidity reduction
• Arsenic removal (in conjunction with coagulation)
• Taste (when used with activated carbon)

Typical flow rates: 1-4 L/hr

For information on water quality guidelines: World Health Organization Guidelines for Drinking Water Quality.

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Pros & Cons

• Relatively cheap to manufacture and produce;
• The ceramics trade is well established in many countries;
• Materials (clay, sawdust, rice husk…) are often readily available;
• If designed and used properly, can remove up to >99% of indicator organisms and reduce turbidity to below World Health Organization guideline values.

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• Very slow filtration rates. (typically ranging between 0.5 and 4 L/day);
  
• Filter maintenance and reliability depends on the user - herein lies many non-technical social issues;
  
• Breakage during distribution or use can be a problem since ceramic filters are often fragile;
  
• Requires regular cleaning;
  
• The rate of production as implemented in countries such as Nicaragua and Nepal has tended to be relatively slow;
  
• It is difficult to maintain consistency (quality control is an issue)

Prices

Prices vary depending on the country, but typically range from $5.00 US to $30.00 US for a complete filter system. Household ceramic water filters in industrialized countries typically cost a lot more; on the order of $100's of dollars.

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Links to Websites and Information Resources

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