Ceramic candle filter
There are several producers of ceramic candle filters. The product discussed here is the Water4life Gravity Unit ceramic candle filter.
The system consists of two reservoirs on top of each other. The top reservoir contains at least one candle and at most two filter candles. The lower bucket works as safe storage for treated water. The top reservoir is filled with contaminated source water. Gravity pushes the water gradually through the porous filter candle. The average flow rate of the water is limited to about 1 to 2 litres per hour.
The filter candles are from India, China, Indonesia or Brazil. Layer 1 is made from clay which is fired to attain a fine pore structure. The size of these pores differ. But the Brazil Stefani candles can stop any particles / bacteria larger than 0,5 micrometer. The second layer is impregnated with colloidal silver on the inside and outside which deactivates bacteria. In layer 3, it is filled up with activated carbon. This is a material that has huge potential to adsorb. Contaminants slide into the holes of this honeycomb and hold fast. thereby it can hold iron, chlorine, odour and colour.
| - High acceptance by user
- Simple operation
| - From surveys it appeared that users do not clean or clean the lower reservoir in a wrong manner. Consequently bacteria can again grow and multiply in the clean water and recontaminate it. |
- No reliable means to check the water quality, especially in regards to the end of life of the product which could cause the consumption of unsafe drinking water.
Construction, operations and maintenance
When new candles are used, don’t consume the first 5 litres for drinking water. Do not clean the unit and candles every day. Filter candles need to be cleaned when flow rate is very low. Use some water an a piece of cloth to rub the dirt off the candles. Never use soap or other detergents. If the dirt has penetrated the outer layers of the ceramics, scrapping off the outer layer is needed. This can be done by using hard brush. Take care that no crack is introduced. Once a crack is created the water is no longer safe.
Store clean water covered and away from sunlight. To prevent recontamination, refrain from opening the lower vessel for any reason and access the filtered water only through the tap.
Complete user’s directions are provided when unit is purchased. Motivational campaigns, extensive training or other instructions could optimize health benefits, reduce failures, and improve the longevity and sustainability of the intervention
Local entrepreneur Water4Life. Field testing in 17 villages throughout the Mpongwe District, Zambia in 2009; commissioned by Water4Lifes. Six months intervention study in a rural community near Cochabamba, Bolivia in 2003 .
Local manufacturer or local trading group is supported by Water4life.
The design of steel vessels are very robust. As long as proper O&M is conducted, no real damage should occur. However, candles need to be handled more cautiously especially during maintenance.
The need of replacing the candle filter is mainly due to clogging. One candle could normally produce 7.000 litres of water.
As for the steel vessels, they will easily last 10 years.
|Capital cost||Operating cost||Replacement cost||Estimated 5 year cost||Cost / metre cubed treated|
| [a] € 25,00
[b] ~US$ 25 = €18,00
[c] 485 Rs = €7,13
| [a] Rs. 75 = €1,1
| [a] €0,56 |
[b] US$ 0,25 = €0,18
[a] based on the Water4life filter; include production cost, training and education of users and manufacturers .[b] based on the filter system used in Charinco. Assuming daily usage of 25 litres/system. [c] price in India with 1 nanosilver candle [d] metal design water purifier with one candle [e] plastic water purifier consists of two plastic buckets that cost €1 each, a tap costs €0,30 and one candle. For all filters, extra carbon cartridge cost €1,30
According to the UN in 2009 over a quarter of the population of Senegal still did not have access to clean drinking water. However, even the “clean” drinking water can pose a problem due to contamination of pipes that are left open to aspirate with the municipal water supply is not adequate or from the contamination of wells. Ceramic candle filters are a cheap and cost effective means of combating water born illnesses for families in cities and villages alike. However, candle filters are not used as widely in Senegal as they are in other parts of the developing world, most notably South America. In Senegal the use of the filters suffers from a lack of availability and publicity about their effectiveness. Entrepreneurs are starting to import them from abroad but without a serious promotion campaign, most Senegalese are unaware of their benefits. However, there is no question about the quality of the filters available.
A comparative study between a variety of ceramic candle filters, including the low cost filters imported into Senegal and the top of the line British Birkfield filters, showed very little statistical difference between the performance of the filters. The $4 USD filters imported from Brazil work just as well as the $40 USD filters made in the UK. The study, titled “A Performance Study of Ceramic Candle Filters in Kenya,” can be found on the MIT.edu website.
To read the full study: Canary Water Filter Case Study.
- Commercial: Ceramic Candle filter parts. Alibaba.com
- A Performance Study of Ceramic Candle Filters in Kenya Including Test for Coliphage Removal. By Amber Franz. MIT, June 2005.
- This article is, in part, based on a factsheet from Aqua For All….
- Zach Swank. Canary Water Filter Case Study Peace Corps Senegal. 2011.