How the sun can turn salty water into drinking water
For coastal villages, access to clean drinking water is a real problem. There is plenty of water but it comes from the sea and is therefore undrinkable. Rainfall is low and open wells soon become salty.
To solve this problem Practical Action has created a simple water distiller which takes advantage of one abundant resource: solar energy.
The distiller simply consists of a galvanised steel tray with slanting glass lid. Water evaporates, condenses on the lid and runs down to a collection pipe. A distiller like this produces 8-10 litres of water a day, and it is extremely high quality. When scientifically tested, the water was free of salts, microbes and nitrogen compounds. The distiller works for any kind of water.
- Galvanized iron sheets are given the shape of rectangular basins, which are lined with corrugated sheet and covered on top with glass lids. The iron sheets are painted black to absorb the sun rays and the radiations. The basins are then fixed on pillars in an area that receives maximum sunlight for the maximum hours of the day.
- Each of the basins is filled with brackish water and has a small channel running towards its base to collect water. The channels are connected with a pipe leading into a can or pot where purified water gets collected.
- The pillars of the basins are placed in such a way that the complete structure is placed at an angle of 15 degrees, slanting towards the channel. When the iron sheet gets heated, water in the basin evaporates and water droplets appear on the glass lid. These droplets roll down into the channel and gradually this purified water flows into the can/pot through the pipe.
Mr Jayaratne from Andaragasyaya in Sri Lanka
Mr Jayaratne resides in Andaragasyaya and is a farmer by profession. He takes care of a family of seven with his meagre income of 12,000 LKR/month. Like many other families residing in Kirinda, sourcing drinking water is a major concern. Women of the households have to fetch water from an open dug well two kilometres away from their home.
Jayaratne heard about the water distillation system in a meeting where Practical Action explained about water purification technology. After discussions with the family, a water distillation system was installed at Jayaratne's premises. Now the family get 8-10 litres of good quality water every day.
Jayaratne's wife says that "previously many hours were spent on fetching water from distant places but now I use my time finishing day to day work and rearing cattle, which has enhanced the family income considerably".
You can download further information on water quality and treatment from Practical Answers, the technical information service of Practical Action, or you can submit a technical enquiry to the Practical Action staff via the online form.
Solar distillation is the process of removing salts and other impurities using the energy of sun to get a pure water for drinking.