Estimation of water footprint in seawater desalination with reverse osmosis process

Seawater desalination is one of the most applied approaches for freshwater replenishment. However, the process not only generates freshwater but also consumes it. It is important to evaluate the balance of the production and consumption of freshwater in desalination, which is also called as water footprint. It will reveal the feasibility of seawater desalination in terms of water production, but related study has not been reported. In this study, the water footprint of reverse osmosis desalination process has been investigated based on a real reverse osmosis desalination plant data. According to the calculation, the freshwater utilization of the reverse osmosis desalination plant was about 8.16 × 10⁻³ m³ with 1 m³ freshwater production. The study reveals that RO desalination is freshwater gain process as the utilized freshwater amount was less than the one produced. The sensitivity study showed that the energy source used in the process was the most significant parameter affecting on the water footprint. The freshwater required in the reverse osmosis desalination with energy supplied by thermal and solar was 8.01 × 10⁻³ m³ and 9.90 × 10⁻³ m³ in 1 m³ freshwater generation, respectively. It suggests that energy source selection is important in RO desalination system.