On paper Marbella’s desalination plant has the capacity to produce 15 cubic hectometres of drinking water per year. However, the reality is that half of the plant is so old that it only produces about half that amount.
The water mainly comes from reserves in the La Concepción reservoir. "Water is taken from the reservoir and from the desalination plant, mixed and distributed upstream in the same pipeline," explained Carlos Cañavate, CEO of the Acosol, the public company that supplies drinking water to the Costa del Sol.
This is where the problems begin: when the reservoir contains a lot of organic matter and it is mixed with the desalinated liquid, volatile chemical compounds are produced during the purification process.
As such the regional government has been asked to look into replacing tanks so that the problem does not occur in future. "When many sections of the desalination plant are activated, the numbers go up and the health authorities start to get concerned about the quality of the water," Cañavate explained. At present, only three or four sections are normally used, which provides around six cubic hectometres a year.
An investment is needed to modernise four sections that were not updated when Acosol renewed half of the machinery several years ago. The Junta has a project under way in its regional drought decree, to update the remaining ones to achieve 15 Hm3; the maximum capacity of the plant.
"That is what needs to be done in the short term, now, and the Junta tells us that it is working on it, although the investment has not yet arrived," warned Cañavate. The works will cost four million euros in total.
But Acosol has a second proposal on the table, which is much more ambitious than the first. Years ago there was an agreement between the Spanish government and the Junta de Andalucía to build a desalination plant in Mijas. However, the project never progressed although a contract was awarded at the time, due to problems in obtaining the necessary land.
"That agreement is dead, while the Marbella desalination plant already has the most important section in place, which is the pipe that goes from the sea to the plant, but which is what causes the most environmental problems,” explained Cañavate.
As such, Acosol has proposed to the national and regional governments that the old agreement for the Mijas project should be forgotten and the 50 million euros that had been earmarked for Mijas should be used to modernise the existing plant in Marbella, which began supplying water in July 2005. In this way, production could be increased to 30 cubic hectometres per year and the cost of this work is in the region of 40 million euros.
"The overall need along the coast is around 100 cubic hectometres a year, so the enlargement would be a very important guarantee". Currently, the La Concepción reservoir provides around 55 Hm3 per year; and the rest is shared between the desalination plant and the network of wells that exist in the different towns and villages, depending on the time of year.
The solution to the water supply on the Costa del Sol, one of the areas with the highest population growth in Spain, involves a series of short and medium-term improvements, which must be centred on the Marbella desalination plant.