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27 April 2018

Ceramic Candle Filter

Author/Compiled by
Lerica G. Shrestha (Environment and Public Health Organization, ENPHO)
Raju Shrestha (Environment and Public Health Organization, ENPHO)
Dorothee Spuhler (seecon international gmbh)
Executive Summary

Ceramic candle filters are simple devices made out of clay and used to filter drinking water in order to removes turbidity, suspended materials and pathogens. Removal takes place by physical process such as mechanical trapping and adsorption on the ceramic candles, which have micro-scale pores. Water is poured into the upper of two container and flows through a candle situated in the bottom. Once the water has passed through the candle, it is collected in the lower container. This system both treats the water and provides safe storage until it is used. The filters are easy to assemble and no energy is required. Maintenance includes frequent scrubbing with a brush and proper care during transport and its use. They can be constructed with locally available material, which can contribute to the development of local commerce.

Advantages
Cheap, simple and easy to use and clean
Removes pathogens, turbidity and suspended solids
Somewhat effective for the removal of viruses and iron
Improves taste, smell and colour of water
Can be constructed with locally available material
Keeps water cold and safe
Durable, easy to move and transport (except clay pot)
Disadvantages
Does not remove all the pathogens
Does not remove chemical contaminants and colour
Highly turbid or iron containing water plugs candle pores
Low flow rate
Ceramic candle and clay container is not easy to transport due to its fragility and heavy weight
Quality control difficult to ensure in local production
In Out

Freshwater

Drinking Water

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Introduction
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The use of ceramic material for the filtration of drinking water is one of the oldest drinking water treatments. Nowadays, the ceramic candle filters and the colloidal silver filter (see also the colloidal silver filter factsheet) are the most widely used. The devices consist of two compartments, which allow simultaneous treatment and save storage of the drinking water. Candle filters are used in various countries and produced by a range of manufacturers around the globe.

Outer and inner view of common stainless steel candle filter. Source: ENPHO

Outer and inner view of common stainless steel candle filter. Source: ENPHO

Filter with one ceramic candle in plastic vessels. Source: CAWST (2009)

Filter with one ceramic candle in plastic vessels on the left side and on the right side different types of ceramic candles. Source: CAWST (2009)

Ceramic candle filters basically consist of an upper and a lower container, one or more ceramic candles in between, a tap and a lid. Usually the containers have a diameter of about 30 by 25 cm depth for a treatment capacity of about 8 L and a flow rate of 1-2 L per hour per candle. The ceramic candles are screwed into the base of the upper container. To the lower container is attached a tap that allow to withdraw safe water without risking recontamination. A lid is placed on top of the upper container to prevent contamination.

Candles can have very slow flow rates, so it is common to use two or more candles in one filter. The candles are made up of clay and the container can be made from plastic, aluminium, copper, steel or clay material. Though clay containers keep water cold and tasty, due to its fragile nature other materials nowadays replace it.

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How does it work?
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Water is poured into the upper container and flows through the candle and collects in lower container. Turbidity, suspended materials and pathogens are removed from water through mechanical trapping and adsorption in micro-scale pores of ceramic candles. Colloidal silver is sometimes used in candle for more effective pathogen removal.

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Operation and maintenance
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Water should be poured slowly into the container, not above the candle as regular water pressure may damage fragile candle. Candle needs to be replaced if any cracks are found: cracks will reduce the effectiveness since water can pass through that crack without being filtered through the ceramic pores.

Candle needs regular cleaning, particularly when the flow rate slows down. The candle is cleaned by (slightly) scrubbing the candle surface with a soft scrubber brush or cloth to remove any accumulated dirt. Only clean water (no soap, chlorine or other chemicals!!!) should be used for cleaning. The candle should not be touched with dirty hands, and not placed on a dirty surface during cleaning. Storage containers, tap and lid should be cleaned on a regular basis using soap and water.

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Effectiveness
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Ceramic candle filters are effective in removing bacteria, protozoa, helminths and turbidity from water. It also removes some viruses and iron and taste, smell and colour of water are improved. The effectiveness of the filter also depends on the production quality, the initial water quality, and the handling practices of users. Highly turbid or iron containing water may plug candle pores easily so that container and candle need to be cleaned more frequently. In this case, the water should be pre-settled before pouring it into filter. It is recommended to use raw water with less iron (

  Bacteria Viruses Protozoa Helminths Turbidity
Laboratory >99 % >90 % >100 % >100 % * 88-97 %
Field >99.95 % Not available >100 % >100 % * 97-99 %

Summary of Ceramic Candle Filter Technical Performance.
* Not researched, however helminths and protozoa are too large to pass between the 0.6-3 μm pores. Therefore, up to 100% removal efficiency can be assumed. Source: MATTELET (2006); CLASEN & BOISSON (2006); FRANZ (2004); CHAUDHURI et al. (1994); HORMAN et al. (2004) in CAWST (2009)

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Production and market
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Candle filters can be manufactured at a local level and contribute to the development of local commerce. Local production process provides financial supports to household and voluntary labours. However, the production of ceramic filters is a lengthy process and a quality control process is required to ensure candle filter‘s effectiveness. Quality can be affected by variations in clay composition across geographic regions. Variability in weather conditions also makes long-term production planning difficult, and lack of storage can complicate storage of filters. The fragility of ceramic filters can make their transport difficult. A supply chain and market availability for replacement of candles and taps is required. Filters typically come with illustrated instructions in market.

Applicability

Ceramic candle filters are easy to set up and operate, cheap and effective in removing bacteria, protozoa, helminths and turbidity from water. It also removes some viruses and iron and taste, smell and colour of water are improved. But due to the limited flow rate (i.e. 1-2liter/hour) and storage capacity, filters are only suitable for small families, organisations or school classroom. It is suitable where drinking water is little turbid (<5NTU) and contaminated and with little iron (<0.3mg/L). In the case of too high turbidity, water can be presettled. Chlorinated water should not be used in candle filters! Except for clay, filter containers of other materials are easy to transport and handle.

Library References

Ceramic Candle Filter. Fact Sheet - Academic

Factsheet on the principles, construction, operation and maintenance of ceramic candle filters for drinking water treatment in developing countries.

CAWST (2009): Ceramic Candle Filter. Fact Sheet - Academic, (= Household Water Treatment and Safe Storage Fact Sheet - Academic ). Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Household-Based Ceramic Water Filters for the Treatment of Drinking Water in Disaster Response: An Assessment of a Pilot Programme in the Dominican Republic

CLASEN, T. ; BOISSON, S. (2006) Household-Based Ceramic Water Filters for the Treatment of Drinking Water in Disaster Response: An Assessment of a Pilot Programme in the Dominican Republic, In: Water Practice & Technology. 1 .

Household Ceramic Water Filter Evaluation Using Three Simple Low-Cost Methods: Membrane Filtration, 3M Petrifilm and Hydrogen Sulfide Bacteria in Northern Region, Ghana

MATTELET, C. ; (2006): Household Ceramic Water Filter Evaluation Using Three Simple Low-Cost Methods: Membrane Filtration, 3M Petrifilm and Hydrogen Sulfide Bacteria in Northern Region, Ghana, (= Master Thesis ). Cambridge: Massachusetts Institute of Technology (MIT) URL [Accessed: 21.07.2010]
Further Readings

Health, Environment and the Burden of Disease; A Guidance Note

This guidance note examines the conditions that determine whether an environmental hazard leads to diseases, and whether feasible measures are available to prevent it. It considers three problems which account for nearly three quarters of the environmental burden of disease: Water, sanitation and hygiene; indoor air pollution; and injuries.

CAIRNCROSS, S. ; ONEILL, D. ; MCCOY, A. ; SETHI, D. ; (2003): Health, Environment and the Burden of Disease; A Guidance Note, London: Department for International Development (DFID)

Ceramic Candle Filter. Fact Sheet - Academic

Factsheet on the principles, construction, operation and maintenance of ceramic candle filters for drinking water treatment in developing countries.

CAWST (2009): Ceramic Candle Filter. Fact Sheet - Academic, (= Household Water Treatment and Safe Storage Fact Sheet - Academic ). Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Ceramic Pot Filter. Fact Sheet - Academic

Factsheet on the principles, construction, operation and maintenance of ceramic pot filters for drinking water treatment in developing countries.

CAWST (2009): Ceramic Pot Filter. Fact Sheet - Academic, (= Household Water Treatment and Safe Storage Fact Sheet - Academic ). Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Ceramic Pot Filter. Fact Sheet - Simplified

Simplified factsheet on the principles, construction, operation and maintenance of ceramic pot filters for drinking water treatment ion developing countries.

CAWST (2009): Ceramic Pot Filter. Fact Sheet - Simplified, (= Household Water Treatment and Safe Storage Fact Sheet - Simplified ). Center for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 01.04.2010]

Ceramic Filtration

Factsheet on the implementation of ceramic filters.

CDC (2008): Ceramic Filtration, Household Water Treatment Options in Developing Countries Factsheets. Centers for Diseases Control and Prevention (CDC) URL [Accessed: 01.04.2010]

Filtration & Chlorination Systems

Introduction to filtration and chlorination systems at the household level.

CDC/USAID (2009): Filtration & Chlorination Systems , (= CDC Household Water Treatment Options in Developing Countries Factsheets ). New York: Center for Disease Control and Prevention (CDC) and United States Agency for International Development (USAID) URL [Accessed: 01.04.2010]

Preventing Diarrhoeal Disease in Developing Countries: Proven Household Water Treatment Options

One-page introduction to main household water treatments methods, and further reading links.

CDC/USAID (2008): Preventing Diarrhoeal Disease in Developing Countries: Proven Household Water Treatment Options, Atlanta and New York: Center for Disease Control and Prevention (CDC) and United States Agency for International Development (USAID) URL [Accessed: 15.03.2010]

Household Water Treatment and Safe Storage Options in Developing Countries. Review of Current Implementation Practices

Summary and brief evaluation of main household water treatment and safe storage (HWTS) options for developing countries. Options described are: chlorination, biosand filtration, ceramic filtration, solar disinfection, filtration and chlorination, flocculation and chlorination.

LANTAGNE, D. S. ; QUICK, R. ; MINTZ, E.D. ; (2006): Household Water Treatment and Safe Storage Options in Developing Countries. Review of Current Implementation Practices, ECSP (2006): Water Stories: Expanding Opportunities in small-scale Water and Sanitation Projects. Washington D.C.: ,17-38 . URL [Accessed: 06.04.2010]

Smart Disinfection Solutions

This booklet, part of the Smart Water Solutions series provides a wide range of methods and products for home water treatment in rural areas.

NWP (2010): Smart Disinfection Solutions, Examples of small-scale disinfection products for safe drinking water. (= Smart water solutions ). Amsterdam: KIT Publishers URL [Accessed: 07.07.2010]

Household Treatment and Storage

This technical brief presents the current options for safe storage and overview of seven types of point of use water treatment options. It also explains the working mechanism, and discusses the microbiological effectiveness of ceramic candle filter as well as community acceptance and sustainability.

OXFAM (2008): Household Treatment and Storage , (= Technical Brief No. 4 ). Oxford: OXFAM URL [Accessed: 21.07.2010]
Case Studies

Scaling Up Household Water Treatment Among Low-Income Populations

This report examines the evidence to date regarding the scalability of HWTS. It seeks to consolidate existing knowledge and experience and distil the lessons learnt. Its primary aims are to 1) review the development and evolution of leading household water treatment technologies in their efforts to achieve scale, 2) identify the main constraints that they have encountered and 3) recommend ways forward.

CLASEN, T.D. ; (2009): Scaling Up Household Water Treatment Among Low-Income Populations, (PhD Thesis). Geneva: World Health Organization (WHO) URL [Accessed: 09.04.2010]
Training Material

Water Treatment Technologies in Low Income Regions. Lecture "Water Resources and Drinking Water"

PDF Presentation on water treatment technologies in low income regions of the world, including many pictures and explaining the most common technologies.

BERG, M. ; HUG, S. ; (2007): Water Treatment Technologies in Low Income Regions. Lecture "Water Resources and Drinking Water", Duebendorf: Swiss Federal Institute of Aquatic Science and Technology

Household Water Treatment Manual

This manual on household water treatment system includes various useful topics on safe water and multi barrier approach (source protection, sedimentation, filtration, disinfection and safe storage).

CAWST (2008): Household Water Treatment Manual, Calgary: Centre for Affordable Water and Sanitation Technology (CAWST)

An Introduction to Household Water Treatment and Safe Storage, A CAWST Training Manual

This training manual describes the need of safe drinking water and sanitation and provides relevant information on HWTS process, technologies. It is good reference material for trainers to conduct training on HWTS.

CAWST (2009): An Introduction to Household Water Treatment and Safe Storage, A CAWST Training Manual, Calgary: Centre for Affordable Water and Sanitation Technology (CAWST) URL [Accessed: 08.04.2010]

Household Water Treatment Options, Technical Reference and Training Guide

This training manual on household water treatment options provides information on safe water, water pollution sources, water quality situation of Nepal and various household treatment options including introduction, its advantages and limitation with points to remember while boiling on pages 14 and 15 (Nepali).

DWSS (2008): Household Water Treatment Options, Technical Reference and Training Guide, Kathmandu, Nepal: Department of Water Supply and Sewerage (DWSS)

Household Water Treatment and Safe Storage (HWTS). Lecture Notes

Lecture notes on the technical and non-technical aspects of sanitation household-level drinking water treatment and safe storage (HWTS) in developing countries.

EAWAG/SANDEC (2008): Household Water Treatment and Safe Storage (HWTS). Lecture Notes, (= Sandec Training Tool 1.0, Module 3 ). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC) URL [Accessed: 08.04.2010]

Household Water Treatment and Safe Storage (HWTS). Presentation

Presentation on the technical and non-technical aspects of sanitation household-level drinking water treatment and safe storage (HWTS) in developing countries.

EAWAG/SANDEC (2008): Household Water Treatment and Safe Storage (HWTS). Presentation, (= Sandec Training Tool 1.0, Module 3 ). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC) URL [Accessed: 18.02.2011]
Awareness Raising Material

Amoeba and Water

This children’s book provides information on safe drinking water, ways of water contamination, simple HWTS options presented in attractive illustrations and simple languages so that school children can easily understand them.

ENPHO (2007): Amoeba and Water, Kathmandu and New York: Environment and Public Health Organization (ENPHO) and United Nations Children's Fund (UNICEF) URL [Accessed: 09.04.2010]

Alternative Versions to