Low-temp distillation system uses waste/renewable energy

A patented low-temperature cost-effective distillation process for seawater desalination has been introduced by Swiss company Watersolutions AG.

A pilot plant in El Gouna, Egypt, with a design capacity of 500 m³/d, has proven the principle, with very pure water being produced reliably and efficiently.

The Watersolutions LTD system condenses water at low temperature and pressure, using waste heat (50‑110°C) from thermal processes including renewable energy sources such as solar energy or geothermal energy. The system requires significant amounts of low grade waste heat (6‑30 MW), which can be derived from any source including thermal power plants, district cooling systems, general industry, mining and waste incineration.

Operating costs, excluding depreciation, are projected at only a third to a half of existing processes. For example, the Watersolutions LTD system with one cascade can produce pure water at less than 1.0 kWh/m³. By contrast, seawater reverse osmosis typically uses 3.5‑4.5 kWh/m³ of water production.

Another benefit is the high conversion ratio, with only 1.5 m³ of seawater needed to produce 1.0 m³ of clean water (<10 ppm of dissolved solids). Maintenance requirements are very low. The Watersolutions LTD system is modular, scalable and easy to install. The units are available in two sizes – a large module that produces 1,000‑2,000 m³/d (pending the amount of waste heat available and number of cascades) and a medium module with capacity of 500‑1,000 m³/d. These units can be combined to scale up production as needed. Watersolutions is currently targeting plants of 500‑20,000 m³/d capacity. The expected lifetime of an LTD plant is 25‑30 years, due to the simplicity of the design, the combination of high quality materials used, and its ability to function at relatively low pressure. Due to the robustness of an LTD plant and its high conversion ratio, the plant operates using a relatively small amount of chemicals for pretreatment etc.