Ceramic filters are devices that have long been used for water filtration.  We define a water filter as a device that improves water quality by capturing unwanted particles and microorganisms while allowing the… water to flow through it.  This is a general definition, as the practical uses of these devices are very diverse, as is their construction.  It is important to take into account that the majority of filters do not purify water, but only improve its taste.

These filters are produced in a number of countries in Latin America (Brazil, Mexico, Nicaragua, Guatemala, Honduras, etc.).  Numerous studies have demonstrated the effectiveness of filters in disinfecting water.

Designs:

There are three primary designs of ceramic filters: flower pot, candle, and siphon.  These three designs can be described as follows:

This type of filter is made of a mixture of 50% red clay and 50% sawdust or a similar organic material such as rice or coffee husks, depending on what is locally available.  Water is added to this mixture and it is put into a mould and compressed by a car jack, which is usually easily acquired.

Through this process, a microporous membrane is formed which prevents the passage of bacteria.  A further step to guarantee water potability is the impregnation of the filter with a colloidal silver solution, which is applied once and which prevents bacterial regrowth.  This process renders water potable and removes turbidity.

Advantages

• It can be used in areas with a reliable water supply.
• It can be used by people of all ages and socioeconomic status.

Disadvantages

• It does not remove contamination by chemicals or heavy metals.
• It is very fragile.
• It costs approximately $35 USD.

The candle design filter works according to the same principle as the porous ceramic pot design, however, its candle shape allows water to flow down its walls.  Like the two other types of filters, the ceramic components of the candle design filter must be washed carefully and replaced periodically.  In comparison with the flower pot filter design, the candle design has a more rapid output of filtered water and its filters are less likely to become blocked.

Each candle design filter is composed of two 20 liter PVC buckets.  The upper bucket contains the following elements: calcified sand, two ceramic candles, geo textile, and a grommet (fastening ring).  The filtered water collects in the lower bucket, and is accessed through a tap.

Advantages

• Effectively improves water quality, rendering it suitable for human consumption.
• Easy operation and maintenance.

Disadvantages

• This filter is designed for treatment of household water with a low bacterial load and a turbidity of up to 100 NTU.  It has an average flow rate of 15 liters per hour.
• It does not remove contamination by chemicals or heavy metals.
• It costs approximately $20 USD.

This filter type consists of two containers, a porous ceramic tube, a plastic tube, and a small manual pump (bulb).

This is the newest filter design and has not been studied long term.  However, it is expected to be highly effective long term and has several advantages:

• It can be adapted to any type of container.
• It has a greater flow rate.
• It is smaller and more durable as compared to the other 2 filter types.
• It is possible to wash it via reverse flow.

Sand filters (also known as “slow filters”) have been used for decades by cities and municipalities around the world to treat community water supplies.  Basically, the water passes through a layer of sand, which prevents the passage of organisms and thereby improves the quality of the water.  The same process was adapted for household use and, due to the sand barrier, is known as a “biofilter”.  There are various designs, brands, and material constructions of biofilters.  The majority of these are promoted and/or distributed by non-governmental organizations (NGOs).

Note:

• Sand filters remove parasites but do not effectively remove bacteria or viruses.  It is therefore not a method of water disinfection.
• Sand filters are rapidly blocked when they are used to filter turbid water.  For this reason, it is necessary to clean them frequently.

Advantages

• It can be used anywhere.
• It absorbs, kills, and filters some pathogens.
• It can be used by people of all ages and socioeconomic status.
• This type of filter can be made using locally available materials such as sand, cement, etc.
• The long life of the product

Disadvantages

• The water quality is under the control of the user.
• The water output by a sand filter requires a complementary method of water disinfection to make it safe to drink.
• The effectiveness of the filter is reduced for a period of one month after the sand is washed.
• The (potentially) lower quality of water supplied as compared with other filter designs.
• Time is needed to form the organic layer (sand barrier).
• The filter weighs approx. 225 kg, making transportation of the filter difficult.
• It costs approximately $75 USD.

Explanation of numbers in figure:

This device contains nanopores which filter substances and organisms greater than 0.2 microns in diameter.

Advantages

• It can be used anywhere
• It removes organic, chemical, or heavy metal contamination.
• It can be used by people of all ages and socioeconomic status.

Disadvantages

• There is little information on this filter.
• High cost.

This plastic, flute-shaped filter contains a series of filters and iodine-impregnated chambers.  The iodine works to instantly kill any bacteria present in the water source.