A simple technical solution

A purification system using ultraviolet rays

“1001 fontaines pour demain” has developed a purification system that exploits ultraviolet rays (with wavelengths of between 250 and 260 nm), which have the capacity to purify 600 to 800 litres per hour. The system includes the following components:

Solar power (a panel of 0.5 m² and a battery), which supplies enough power for 5 days of autonomous operation. A small pump, which circulates the water within the system. An array of filters, which eliminate the impurities that could otherwise interfere with the ability of ultraviolet radiation to kill the bacteria. An ultraviolet sterilisation chamber with a photoelectric cell that maintains the intensity of the ultraviolet rays. An electronic module that ensures the operation and monitoring of the system: the system is programmed to provide a level of ultraviolet radiation that ensures sterilisation of the water for the life of the system. This guarantees that the water is always properly sterlised. In the case of a problem with this electronic module, it can easily be replaced. The system is designed in such a way that a local operator does not need to have any special qualifications to maintain it or to perform routine repairs.

A rigourous process

The process of sterlisation using ultraviolet radiation is effective for water contaminated with bacteria, but does not apply to water which is polluted with chemicals. In addition, contrary to chlorination, sterilisation with ultraviolet radiation is not permanent, as the water may become re-contaminated unless a certain number of precautions are taken.

As a result of our practical experience, we have been able to develop a rigorous approach which maximises the effectiveness of the ultraviolet sterilisation and prevents the purified water becoming contaminated anew.

Pre-treatment of the water to be purified

Many villagers currently use the process of “flocculation” and decantation to filter out visible sediments and materials from water prior to consuming or using it. This is accomplished with aluminum sulphate. In order that the water to be treated is sufficiently clear to avoid clogging the filters and to enable the ultraviolet purification to be of maximum effectiveness, the “fountain” includes a cistern in which the water is pre-treated by means of flocculation and decantation, as well as sand filtration.

Conditioning

The purified water must be transported in such a way as to prevent re-contamination. It is therefore put into 20 litre containers which have been thoroughly disinfected. These containers are sealed as soon as they have been filled.

The local operators receive on-going assistance in the application of the purification process from trained technicians. These technicians also perform regular quality controls of the purified water.

Investment costs

The studies conducted in 2004 and the pilot projects conducted in Cambodia since 2005 demonstrate that a purification system can be installed in a small village at a cost of less than €10,000 for deployment on a large scale. This includes the costs of training the operator and providing him/her with a salary during the training period. Based on these costs and some conservative assumptions about the level of consumption, this implies a cost of less than 10 euro per beneficiary.

The village in which the “fountain” is to be installed supplies the building for it according to the criteria specified by “1001 fontaines pour demain”.