Solar Powered Desalination Plant
& Reverse Osmosis

Location and Implementation

Kotri, a small village with 300 families in the Ajmer district of Rajasthan, received the first ever solar powered desalination plant in India. Nearly 100 villages surround Sambhar lake, a large saltwater lake where villagers make their livings manufacturing salt as it evaporates from the water. However, the salinity levels are so high that even after significant evaporation, the water is too brackish to consume or use for cooking and cleaning. Over time, the contaminated water has entered the groundwater and caused skin ailments and stunted growth in children as well as poor crops and infertile soil.

With the new desalination plant, brackish water from Sambhar lake enters the village through the government pipelines and is pumped through the plant and stored in a 5,000 litre tank. The plant is made from materials that are simple and easily available: a booster pump, a sand filter, a cartridge and a carbon filter that prevents waste and impurities from mixing with the desalinated water. The RO plant reduces salinity levels (Total Dissolved Solids or TDS) from 4,000-6,000 parts per million to only 450ppm, making the water clean and safe for consumption.

The RO plant runs on a 2.5 kilowatt power plant that allows it to produce 600 litres of water per hour for six hours each day. Even though Kotri already receives electricity from the traditional electric grid, the coverage is erratic and rarely powers the village for more than three hours per day. For this reason, the plant has been solar electrified to ensure an uninterrupted supply of electricity for six hours, with some power to spare for a computer, a solar workshop, fans and light.


The plant meets the drinking water needs of more than 1,000 men, women and children from Kotri and its surrounding villages. Each family can take 40 litres of water every day for a token fee of Rs.10 per month. It costs just INR.15.5 lakhs to install a mini-RO plant specially designed for operating in a village, which in turn brings drinking water to the entire rural community.