Dear etienne Without more ...

Dear etienne

Without more information I am not sure what exactly is the problem. I do share the views of many of the responses regarding the suitability of chlorine and its practical application for well disinfection. 

My only comment would be to suggest taking a wider view of the problem and, if you have not done so already, view chlorination as one of several barriers for producing safe drinking water. For example, can anything be put in place to avoid contamination of the wells in the first place. In addition, waterborne diseases come with sewage contamination to some extent which would exert a considerable demand on the applied chlorine dose. Some form of prior treatment may be necessary to remove / reduce organic matter to make disinfection more effective. Also, does chlorination need to be undertaken in the well itself as others have pointed out the drawbacks of this approach. Extracting water from the well before chlorination would offer more control over the process.

Kind regards

Robert