The extent of chlorine’s importance

Chlorine eliminates 99.9% of bacteria and protects water against recontamination

Chlorine is by far the most commonly-used disinfectant in the world, states the World Chlorine Council. It is used to destroy disease-causing organisms in water, an essential step in delivering safe drinking water and protecting public health. Where widely adopted, chlorine has helped to virtually eliminate water-borne diseases such as cholera, typhoid and dysentery. Chlorine also eliminates slime bacteria, moulds and algae that commonly grow in water supply reservoirs, on the walls of water mains and in storage tanks. Only chlorine-based disinfectants leave a beneficial ‘residual’ level that remains in treated water, helping to protect it during distribution and storage.

Chlorine is a versatile and low-cost disinfectant appropriate for any size water system, whether it serves a remote rural village or a large modern city. Where piped water supplies are not available, chlorine can also be used for treating water in individual households.

In responding to the 2004 tsunami disaster in South Asia, the World Health Organization (WHO) reported:

“Chlorine is most widely and easily used, and the most affordable of the drinking water disinfectants. It is also highly effective against nearly all water-borne pathogens.”

From a Fact Sheet prepared as a co-production of Akvo and Aqua for All
1.Bacteria include Burkholderia pseudomallei, Campylobacter jejuni, Escherichia coli, Salmonella typhi, Shigella dysenteriae, Shigella sonnei, Vibrio cholerae, Yersinia enterocolitica.
2.Viruses include enteroviruses, adenoviruses, noroviruses, rotavirus.
3.Protozoa include Entamoeba histolytica, Giardia lamblia, Toxoplasma gondii, Cryptosporidium parvum.
4.CDC (2007)
5.AWWA (2006) shows that chlorine is ineffective for Ascariasis lumbricoides ova.
6.Mercado-Burgos et al.(1975) show moderate effectiveness for Schistosoma species. Assume moderate effectiveness for Dracunculus medinensis.

Sodium hypochlorite is a chemical compound with the formula NaClO.

Today, sodium hypochlorite is produced in 85 countries. Production has risen from 35,000 tons at the end of the 19th century to 44 million tons today. It is still used in most water supply networks in northern Europe and North America, to guarantee the perfect hygiene of drinking water.

Proper storage as a condition to stability

The active chlorine concentrate must be stored in opaque receptacles, properly closed and away from the light. Note that a full receptacle will keep longer than a half-empty one, where the air will oxidise the concentrate.

Please see our recommendations on sodium hypochlorite shelf life.

The intake of concentrated active chlorine is very unlikely to happen, considering its irritant smell and bad taste. Nevertheless, in case a child takes a large gulp of it, just make the child drink water in order to lessen the bad taste.

Occasional chlorine over-dosage in drinking water involves absolutely no risk for health. For that matter, drinking water supplies in large cities of developing countries often have chlorine concentrations above WHO standards (up to 2 mg/l). Besides, the consumer immediately recognises the strong smell and taste of chlorine in drinking water when it is over-dosed. Regular quality control with the WataBlue reagent avoids such excesses and thus enables drinking safe and good-tasting water.

Click here to visit our page about the use of chlorine

The differences with bleach

There are two fundamental differences between bleach and the concentrated solution of active chlorine produced with WATA. First, bleach contains a stabiliser (caustic soda) to raise its pH and thus ensure a longer lifetime to the product. Secondly, the solution produced with WATA is five times less concentrated in chlorine than bleach. However, as it contains no caustic soda, the active chlorine reacts faster.

The solution produced with WATA is not corrosive. Moreover, drinking bleach is very dangerous because of the toxicity of caustic soda. On the other hand, an intake of the solution produced with WATA is certainly unpleasant, but there are no risks to health.

Part of this text was compiled using information from the publication Drinking Water Chlorination, a 2008 position paper of the World Chlorine Council, an industry association. The Antenna Technologies Foundation is not a member of the WCC.