Compiled by:
Julie Bergamin (Antenna Technologies), Carole De Bazignan (Antenna Technologies), Dorothee Spuhler (seecon international gmbh)

Executive Summary

Chlorination, which means adding active chlorine (sodium hypochlorite) to water, is the most common method used for disinfecting of drinking water. Active chlorine destroys or inactivates most pathogenic microorganisms, including parasites, bacteria and viruses with a very high reliability. The WHO estimates that chlorination is the most secure, effective and economic option. Yet, generally speaking, chlorine is not produced in low-income countries, but imported in the form of tablets or bleach, at relatively high cost. WATASOL is an approach developed by Antenna Technologies which integrates health education with the local production of chlorine by electrolysis (the WATA device) in a sustainable supply chain, making safe water treatment a profitable activity.

In Out


Drinking Water

A study published in January 2008 by the UNICEF shows that household-based interventions were about twice as effective in preventing diarrhoeal disease (47%) than improved wells, boreholes and communal stand pipes (27%). It is thus fundamental to find solution to enable population address their drinking water problem in a self-sufficient and perennial way. Aware of the need to introduce simple and affordable water treatment methods at household level, Antenna Technologies has developed a line of WATA devices (Mini, Standard and Maxi WATA), part of the WATASOL approach. Until today the WATA kits have been implemented in over 45 countries.

 Antenna Technologies

Production of concentrated active chlorine using the Standard WATA. Source: Antenna Technologies

The WATA Devices

WATA is a handy and robust device for the local production of active chlorine through the electrolysis of salted water. The resulting solution can be used for drinking water chlorination (1 L of chlorine per 4.000 L of contaminated water) or disinfection of food preparation materials, premises and other equipment. Based on 12 hours of daily operation, Mini WATA can serve 240 individuals, Standard WATA 2.400, and Maxi WATA 36.000.

 Antenna Technologies.

Electrolysis process turning salted water into active chlorine. Source: Antenna Technologies.

The device requires water, salt and electricity. When immersed, and connected to a reliable source of electricity, a process of electrolysis takes place, converting the saline solution (sodium chloride) - with 25 g of salt per litre - into active chlorine (sodium hypochlorite) at 6g/L. Water, which is possibly contaminated can be made potable by adding a small dose of chlorine (5 mL chlorine into 20 L water). The strong oxidising power of the chlorine will destroy most of the pathogenic germs. The water will be drinkable after 30 minutes.

 Antenna Technologies

Use of active chlorine concentrate: Disinfection and cleaning. Source: Antenna Technologies

The active chlorine concentrate solution produced with WATA devices can also be used as a disinfectant. In diluted form, it can be used for cleaning latrines, disinfecting kitchen utensils and surfaces, or even washing rough fruits and vegetables. It can also be used for disinfecting laboratory equipment. The concentrate is similar to Dakin’s solution, a neutral disinfectant, and can be used directly for cleaning wounds.

WataTest™ and WataBlue™ reagents are part of the WATA kits and allow the user simple onsite water quality control. WataTest™ is a non-toxic and inexpensive reagent, which is used to control the concentration of sodium hypochlorite in the produced solutions form the WATA devices. WataBlue™ measures the concentration of residual free chlorine in the water. Residual chlorine keeps the water pathogen free after disinfection. Minimal residual chlorine should be at least 0.5 ppm in order to prevent regrowth of the pathogens. But the chlorine should be below 1 ppm. WataBlueTM allows the user to carry out a safe and systematic quality control of the treated drinking water.


Specifically designed for the needs of developing countries, these devices give even the poorest of the poor an affordable solution to produce their own drinking water. Without the initial investment, the cost price for one litre of active chlorine concentrate is below € 0,01. Excluding shipping, investment costs for the Mini WATA are € 40, Standard WATA € 200, and Maxi WATA € 1.700.

Operation and Maintenance

Active chlorine is very sensitive to light. It is therefore very important to store the solution produced with the WATA devices in closed and opaque recipients, and to keep them in the shade. Under these conditions, the active chlorine concentrate can be conserved over 4 weeks without any problem.
It is important to have clear water, both for the process of electrolysis and the water to be treated with the active chlorine solution. Chlorination cannot be guaranteed if the water is cloudy or muddy. In such cases, it is necessary to first filter the water, or settle or flocculate suspended solids.
Devices need to be rinsed after each procedure with clear water. With time, calcareous deposits form on the electrodes. The frequency of which this deposits need to be cleaned depends on the water hardness, it is recommended to do it after about 150 hours of functioning. The deposits for the Mini and Standard WATA can be removed as follows: 1) Fill a recipient with lemon juice or vinegar; 2) Immerse the WATA device overnight into the lemon juice / vinegar – Do not scrub; 3) Rinse the device with clear water, dry it and store it. WATA maxi calls for different procedures.

Properly used, well maintained and carefully stored after each use, WATA devices are guaranteed to operate for at least 20 000 hours of operation (4,5 years on the basis of 12 hours use per day).

The WATASOL Approach

Direct sales of flasks of active chlorine in a kiosk, Dabola, Guinea.

Direct sales of flasks of active chlorine in a kiosk, Dabola, Guinea. Source: Antenna Technologies.

WATASOL is more than a device; it is an approach, which integrates health education with the local production of chlorine in a sustainable supply chain, making safe water treatment a profitable activity. In the long term, the production and the dissemination of chlorine should generate an income for the local population and should insure their autonomy.
Several dissemination models have been identified and tested in the field:

  • Through health centre: they produce their own disinfectant (Dakin solution) at very low cost;
  • Through economical structure (i.e. women’s groups, salesperson in kiosks): they create an income-generating activity around the production of chlorine;
  • Through school structures responsible for promotional and awareness activities;
  • Through water user association.

The WATASOL approach can be introduced by organisations step by step:

  1. The Demo phase helps getting people familiar with the Watasol technology;
  2. The Try-out phase gives hands-on familiarity;
  3. The Testing phase confirms the viability of local production of chlorine;
  4. The Pilot phase will determine the right dissemination strategy and potential business model;
  5. The Scaling-up phase aims to replicate successes on a wide scale.


Chlorine is highly effective against bacteria and viruses, and provides residual protection against recontamination (residual free chlorine). However, chlorine is inefficient against cryptosporidium and certain worm cysts (helminths) and cannot purify chemically contaminated water.

Raw water should be considerably clear, both for chlorine production and for drinking. Chlorination cannot be guaranteed if the water is cloudy or muddy. In such cases, it is necessary to first filter the water, or settle/flocculate the suspended solids.

Chlorine concentrate can be used for drinking water chlorination or as a disinfectant. Therefore WATA device is an indispensable tool for households, but also for hospitals, community clinics and other health centres.

WATA is appropriate for urban and rural areas. The WATA devices need electricity supply to operate. Nonetheless, solar versions are available for WATA Mini & Standard.

Despite its simplicity, producing potable water for a community with a WATA device is quite a responsibility, and thus requires skilled people as operators, specially trained for that purpose.


  • Low cost
  • Local production (which avoid most storage and transportation problems and environment impacts)
  • Generation of income for local communities (e.g. water kiosk)
  • Easy to use
  • Solar versions available for use in rural areas
  • Disinfectant can be used for a large range of applications (e.g. cleaning latrines, disinfecting kitchen utensils and surfaces, washing rough fruits and vegetables, disinfecting laboratory equipment, wounds etc.)
  • Quality control is possible at every stage of production and use


  • Only clear water can be used to produce WATA solution and the solution only effective to treat clean water
  • Electricity required (but can be run with solar energy)
  • The device must only be used by adults
  • Education and training for operators are essentials, especially when using Maxi WATA
  • Reaction time of 30 min required before consumption after treatment
  • Chlorination can cause the generation of toxic disinfection by-products (DBPs) in the case of high organic content
  • Chlorine taste and smell
  • Dosage might more difficult than with tablets

References Library

UNICEF (Editor) (2008): Promotion of household water treatment and safe storage in UNICEF WASH programmes. pdf presentation. New York: United Nations Children's Fund. URL [Accessed: 17.03.2010].

NWP (Editor) (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].

WHO (Editor) (2008): Guidelines for Drinking-water Quality, Third Edition. Third Edition incorporating the First and Second Addenda. Geneva: World Health Organization (WHO). URL [Accessed: 23.04.2012].

ANTENNA TECHNOLOGIES (Editor) (2009): Drinking water, a global issue. ANTENNA TECHNOLOGIES . URL [Accessed: 01.07.2010].

Further Readings Library

Reference icon

AUTARCON (2012): AUTARCON SuMeWa System. SolarPV Driven-Drinking Water Treatment. Munich:

Powerpoint presentation of the water purification system implied by AUTARCON. This system uses solar energy to realise mechanical filtration and chlorification of water.

Reference icon

HEIERLI, U. (2008): Marketing Safe Water Systems: Why it is so hard to get safe water to the poor – and so profitable to sell it to the rich. Bern: Swiss Agency for Development and Cooperation (SDC). URL [Accessed: 07.06.2010].

This book provides unique insights – from the varied perspectives of users, disseminators, producers and retailers – into the marketing challenges of point-of-use water treatment devices.

Reference icon

UNICEF (Editor) (2008): Promotion of household water treatment and safe storage in UNICEF WASH programmes. pdf presentation. New York: United Nations Children's Fund. URL [Accessed: 17.03.2010].

Short introduction to household water treatment and the main treatment methods.

Reference icon

CDC/USAID (Editor) (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].

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

Reference icon

CDC/USAID (Editor) (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].

Introduction to filtration and chlorination systems at the household level.

Reference icon

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].

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.

Reference icon

IFRC (Editor) (2008): Household water treatment and safe storage in emergencies. pdf presentation. Geneva: International Federation of Red Cross and Red Crescent Societies (IFRC). URL [Accessed: 23.04.2012].

This document is intended as a general manual on household water treatment and storage in emergencies. Methods of treatment but also promotion are presented, including factsheets, a decision tree and very comprehensive illustrations.

Reference icon

NWP (Editor) (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].

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

Reference icon

WADDINGTON, H.; SNILSTEIT, B.; WHITE, H.; FEWTRELL, L. (2009): Water, sanitation and Hygiene interventions to combat childhood diarrhoea in developing countries. (= Synthetic review, 001). New Delhi: International initiative for Impact Evaluation (3IE). URL [Accessed: 07.06.2010].

This document provides a review of the effectiveness of interventions in the water, sanitation and hygiene (WASH) sector in promoting better health outcomes in developing countries, as measured by the incidence of diarrhoea among children.

Reference icon

WHO (Editor) (2011): Guidelines for Drinking-water Quality, Fourth Edition. Geneva: World Health Organization (WHO) . URL [Accessed: 08.08.2011].

This volume of the Guidelines for Drinking-water Quality explains requirements to ensure drinking-water safety, including minimum procedures and specific guideline values, and how those requirements are intended to be used. The volume also describes the approaches used in deriving the guidelines, including guideline values. It includes fact sheets on significant microbial and chemical hazards.

Reference icon

WORLD CHLORINE COUNCIL (Editor) (2008): Drinking water chlorination. Position Paper. URL [Accessed: 07.06.2010].

This 8-pages information paper highlights chlorine’s critical role in providing safe drinking water; the potential health and environmental effects of chlorine and disinfection by-products; and considerations for selecting disinfection methods.

Reference icon

DESILLE, D. (2013): Conservation et Traitement de l Eau a Domicile. Paris: Programme Solidarite Eau (PSeau). URL [Accessed: 06.06.2013].

This practical guide provides a review of different processing techniques and adequate water conservation at home and is structured around 10 key questions that should be posed before choosing a suitable solution.

Case Studies Library

Reference icon

SOBSEY, M.D.; HANDZEL, T.; VENCZEL L. (2003): Chlorination and safe storage of household drinking water in developing countries to reduce waterborne disease. In: Water Science and Technology 47, 221-228. URL [Accessed: 07.06.2010].

This study evaluated point-of-use chlorination and storage in special plastic containers of gathered household water for improving microbial quality and reducing diarrhoeal incidences among consumers living under conditions of poor sanitation and hygiene.

Reference icon

WIDMAN, M. (2011): PV Meets Drinking Water. In: pv magazine 12. URL [Accessed: 16.07.2012].

This article describes the practicability of a water purification system which is not reliant on batteries but on solar radiation.

Important Weblinks

http://www.unicef.org/wcaro/2009_4073.html [Accessed: 01.07.2010]

In response to a severe cholera outbreak in 2006, UNICEF has partnered with Tinkisso, a local NGO in the region of Dabola that produces active chlorine with WATA devices.

http://www.humanitarianreform.org/Default.aspx?tabid=343 [Accessed: 01.07.2010]

A complete WASH Cluster Hygiene Promotion training package.

http://www.pedag-eau.fr/ [Accessed: 01.07.2010]

Awareness raising material on water, sanitation and hygiene (only available in French).

http://www.antenna.ch/en/drinking_water/wata_guides.html [Accessed: 01.07.2010]

User guide for WATA kit and quality control reagents.

http://www.youtube.com/ [Accessed: 01.07.2010]

This video explains how to produce active chlorine with WATA devices. FRENCH

http://www.youtube.com/ [Accessed: 01.07.2010]

This video explains how to use active chlorine produced with the WATA device for drinking water, disinfection and cleaning. It explains also how to use the tests to control disinfection and residual chlorine concentrations. FRENCH

http://www.antenna.ch/en/drinking-water.html [Accessed: 01.07.2010]

This website provides general information on chlorine and its different uses, WATA devices (user guides) and quality control reagents as well as on the WATASOL approach and its implementation around the world.

http://www.antenna.ch/en/drinking_water/wata_press.html [Accessed: 08.06.2010]

This internet link presents the WATA press release and various articles on WATA and the WATASOL approach.

http://www.akvo.org/wiki/index.php/WATAsol [Accessed: 01.07.2010]

Akvopedia is an open water and sanitation resource and provide information on production of active chlorine with WATA devices.

http://www.eaudejavel.fr/pages/eau/chimie.asp [Accessed: 01.07.2010]

This website in French is a host of information on chlorine. FRENCH

www.cdc.gov/safewater/about_pages/chlorinationtable.htm [Accessed: 01.07.2010]

This site describes the effect of chlorination on inactivating selected pathogens.

http://300in6.org/ [Accessed: 01.07.2010]

300in6 is an initiative to provide 300 million people with safe drinking water in 6 years with a focus on home water treatment options that include chorine.