Water: Santa Lucia


GTI Awards 2019 – Water

A new hybrid system, which combines Reverse Electrodialysis and Reverse Osmosis, Santa Lucia (Carribean Islands)

General information:

Island (Region, Province, Country):
Santa Lucia (Carribean Islands)


Budget / cost of the project:
€ 450.000


Project objectives:

A new hybrid system, which combines Reverse Electrodialysis and Reverse Osmosis, is proposed to be installed in Santa Lucia to produce drinking water. This installation will provide fresh water for about 5000 inhabitants, avoiding the import from the mainland.


Project description of activities and specific interventions:

Reverse Electrodialysis, in short-circuit conditions, is used to pre-desalt seawater (SW) by the transport of salt from the feed seawater into a sink stream that can be for example treated wastewater (TWW). Pre-desalted SW is fed to a Reverse Osmosis pressure vessel, which can operate at lower pressures than in conventional RO.


Public outreach, education and awareness efforts and results:

The performance of this new hybrid system was studied in the operating conditions (feed SW concentrations, TWW concentration, temperature) typical of Santa Lucia, by using a purpose-built process model. The system was designed to produce about 960 m3/day. The proposed technology was compared with a conventional seawater RO (SWRO) plant. The hybrid system showed lower specific energy consumptions compared to SWRO.


Economic value added and how calculated:

The economic added value was estimated in terms of cost-saving, comparing the hybrid RED-RO system with the SWRO system. Capex (including manufacturing, indirect, proportional, and financial costs) were depreciated in 10 years, considering the plant working for 8640 h/y, and the total cost is obtained by adding the Opex (including energy consumption, material and labour). The economic value added is estimated as the difference of the import cost (4.04 €/m3) and the final cost for the hybrid system (1.809 €/m3) and was equal to 2.23 €/m3, leading to a cost saving of 55%.


Ecological and social project outcomes:

The installation of this system will provide fresh water for 5000 inhabitants, avoiding naval transport and thus reducing sea pollution.