Desalination of Well Water

Anyone know of a low cost method that farmers can desalinate water from a well? A friend is working with farmers in Kenya, and one of their challenges is that their water from wells is very salty. Is there anything that they can do within their local community to desalinate the water for irrigation and drinking?

Isaac, this is a tough problem, there are few low cost options. Dissolved minerals (including table salt) can’t be filtered out of water, and can present both health hazards and hazards for crops and livestock. Do you have a water test report available? The cheapest technology on an operating basis is solar distillation. Using a sloping plastic or glass cover and using the well water to wet materials that are under the cover clean water will condense on the cover and drain into a catch basin. A quick web search will give drawings/photos and details but these are usually fairly small, low capacity devices. Solar still - Wikipedia
Depending on the level of salts in the water dilution with water from a rain water catchment system can lower the dissolved materials to a level the water can be used for drinking and cooking BUT dissolved minerals tend to accumulate in soil when the water is used for irrigation. There are good references on how much of various dissolved minerals different crops and livestock can tolerate. They must be very careful with irrigation you don’t want to let minerals from irrigation water build up in soil to the point that crops can’t be grown in it.

Reverse osmosis isn’t a low cost technology but it will work but requires electrical power. Is that available for this community? Happy to give more information as you have details.

Good morning Larry. Thank you so much for this information.
There is no water test report. The village does not have electricity either. The solar distillation is very interesting, and we’ll hopefully try that, at least on a pilot scale. The challenge now would be, how much plastic would be needed for a household of 5? I don’t know how many villagers would be able to afford good plastic that can last for a long time.
Let’s brainstorm on solutions for sever resource starved areas.
Thanks again Larry. I really appreciate these resources.

Well, this might not be a direct answer to you question, but we had a similar situation: When we moved to Dodoma in 2017 to start a regenerative farming project, an existing deep well (150m) was giving salty/brakish water. We dug a total of almost 2km of water retention swales for reducing rainwater runoff and established other water harvesting measures, planting thousands of trees etc.

After three years we experienced a decrease of salt levels in the deep well. Obviously, some of the water we harvested percolated into the deeper layers of the soil and reached the underground aquifer, reducing salt content somehow. This process is still ongoing, leaving the deep well having increasingly sweet water.

Of course this would not be a solution for every environment, and it is not a quick working solution either, but it might work in your area as well…