Water and chemical savings in cooling towers by using membrane capacitive deionization

• Desalination of cooling tower feed stream with MCDI
• MCDI enabled significant chemicals, water and waste water savings.
• MCDI showed lower energy use and lower fouling susceptibility compared to RO.
• Observed preferential uptake of chloride and calcium can further increase savings.

Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a voltage difference between two oppositely placed porous carbon electrodes. In front of each electrode, an ion exchange membrane is positioned, and between them, a spacer is situated, which transports the water to be desalinated. In this study we determined the water and chemical savings that can be achieved in a cooling tower by desalinating the feed water stream with a full-scale MCDI system. By monitoring the water use of the cooling tower, and comparing this to a scenario without MCDI, chemical savings up to 85% could be achieved. Additionally, water savings up to 28%, and waste water savings up to 48% could be achieved. MCDI energy use for desalination of cooling tower feed water was between 0.1 and 0.2 kWh per cubic meter of produced desalinated water. Preferential uptake of chloride and calcium was observed, which lowers the risk of scaling and corrosion in the cooling tower and allows for further chemical and water savings.