#05 | Desalination and water reuse: alternative and guarantee

Authors: Miguel Esteban Martín and Belén Miranda (ACOSOL)

Marbella Seawater Desalination Plant was built in 1997 and started to work continuously in 2005, as one of the water infrastructures of the integral water cycle managed by Acosol in Western Costa del Sol.

Desalination treatment is the process of taking out the salt from seawater through a chemical-physical process and reverse osmosis to get drinking water for urban supply (complying with RD 3/2023 for human consumption). In reverse osmosis seawater is pumping at high pressure through semi-permeable membranes, so water and salt are separated, getting a clean flow of water with low salt concentration (desalinated) and another flow with a high concentration of salts which is thrown into the sea again. Desalinated water is remineralized and treated with sodium hypochlorite for disinfection before being pumped to the water tank in the Drinking Water Treatment Plant, where is mixed with already treated drinking water and forms part of the urban water supply system.

The annual production of desalinated water is about 5,5 Hm3, which means about 100 Hm3 since started to work in 2005.

Nowadays the different contributions that Acosol makes to the management of water for human consumption are:

Reservoir La Concepcion 76%, Desalination plant 12%, underground water 8%, externals suppliers 4% (from another reservoir in Cadiz).

Drought periods are very common in Mediterranean climates. But also in this area, La Costa del Sol, tourism comes every year, and the population triples from that of the rest of the year (from 530.000 to almost 1.200.000 people), increasing demand for drinking water. For these reasons, Desalination is an effective solution to supplying part of the water demand. The production plan for the Seawater Desalination Plant depends on the following aspects: the estimation of the demand for drinking water, the situation of the reservoir in La Concepcion the level of water also depends on the rainfall of the previous year, the level of underground water and the production capacity of Drinking Water Treatment Plant. However, other aspects could have an influence on the production plan, such as the energy crisis or a Health crisis (COVID).

If we observe the rainfall data from recent years in this area, we can see that the summer period when there is no rain at all, is also the period when the demand for drinking water is highest (due to tourism). These months are when the Desalination plant is working more, as well as in the winter period of a dry year.

*AEMET , estación de meteorología Málaga Aeropuerto.

Climate Change and Global Warming make dry periods more frequent and longer, also the evaporation of surface water is higher. This is why we have to make sustainable management of our resources. Desalination is an effective and safe alternative to increase water resources and cope with the demand for water in coastal areas and periods of drought. Desalination presents production flexibility, reduced environmental impact and a tendency to increase its energy efficiency.

Another technology like aquifer recharge with recycled wastewater (reclaimed water) is researching in our facility in Marbella, with a LIFE MATRIX PROJECT: Safe water reuse in Managed Aquifer Recharge: innovative solution combining physical, digital and governance aspects.