And here is a practical answer:
The OMS recommends a residual concentration of chlorine in the water of 0.2-0.6 mg/L.
A quick calculation leads to 25ml of 15% solution to 10L of water giving you a theoretical free chlorine concentration of 0.375ml/L.
However! Caution is in order as the water is for human use!
The water should have been filtered to minimize organic matter.
Make sure that the water is not contaminated by toxic materials or detergents.
As important, measure and monitor the achieved concentration to ensure it is within the OMS recommendations.
Here is a similar text in Portuguese.
As concentrações preconizadas pela OMS de cloro residual livre devem estar no intervalo de 0,2-0,6 mg/L. Assim sendo, com solução a 15%, com 25 ml dessa solução para 10 litros de água conseguimos uma concentração de 0,375.
Será fundamental garantir que a água provém de zona protegida contra contaminações e dependendo da origem se está filtrada para minimizar quantidade de matéria orgânica e assim a formação de subprodutos de desinfeção, igualmente garantir que a solução não tem adicionados detergentes ou outros produtos perigosos. Será igualmente muito bom que tenham equipamento de medição para verificarem se a concentração final se encontra dentro do intervalo referido e por quanto tempo de mantém...
I hope this helps.
Good question, but often you need to act fast and be practical. Therefore we advised to use a spoon (is about 15 ml.), also to avoid contact with the solution.
Therefore we used some years ago in Angola during a cholera epidemie the following:
Because most people use 20 liter buckets:
For every 20 liter bucket you add 2 spoons of the 15% solution, this will give you about 0,4 ml/L in the bucket. which is sufficient. Stir well and cover the bucket.
Indeed, in case the water is not clean, part of the chlorine will be used up by the dirt, so in that case you can add half a spoon extra to be sure. The same is valid for very contaminated water, in that case the bacterias will use up most of the chlorine, so you have to add half a spoon extra.
Important ! Don't forget always to explain to the users of the water to wait at least half an hour before using the water, because chlorine needs some time to work.
Advise people to use the water in the bucket within 1 day, or add another half spoon, because with time the chlorine concentration will get less.
If you want to have better and faster results and work more easy, we recommended not to use Chlorine, but Chloor-Dioxide, you can buy this now in small pills in convenient strips, brand name is AquaProve. This works already within 10 minutes and does not leave this typical "chlorine" smell. So also better for children.
Fact: In agriculture they use Chloor-Dioxide to disinfect drinking water now a lot because animals don't like the smell of chlorine.
Paul van Beers FairWater.org
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