Seawater desalination plant in Aguilas Guadalentín

The seawater desalination plant in Águilas has a capacity of up to 210,000 m³/day. It supports the water supply for irrigation demands in the southern region of the Segura Basin, as well as the supply to the municipalities of Lorca and Águilas.

The seawater intake is of an open sort. It is done through an intake tower made of reinforced concrete, a cylindrical structure that is 5.3 m in diameter and 6.5 m tall, supported on the sea floor at 18 m deep. The piping includes a 511 m stretch of PEAD pipes with an anchored inner diameter of 2,200 mm, which in turn connects to a stretch of concrete polymer pipe in a tunnel, built with pipe jacking in two stretches with a total length of 400 m.

The well where the seawater arrives under force of gravity, and where 6+1 submergible pumps with a unit flow if 3,399 m³/h and a discharge pressure of 48 m.w.c are located, has dimensions of 37 x 14.5 m². The drive pipeline is a FRP pipe with an inner diameter measuring 2,200 mm that allows saving the 3,260 m that separate the pumping facility and the desalination plant.

Pre-treatment consists of three stages of filtration, the two first through a granular bed, first by gravity and then under pressure, and the third is cartridge microfiltration.

The water filtered in the first stage goes to a 4,000 m³ underground tank from which the necessary pumps vacuum to elevate the water pressure to the level required in the second stage of filtration and the following processes. The pump is composed of a group of 12+1 horizontal centrifugal pumps. The pumping capacity of each of these is 1,761 m³/h to 7 bars.

Before the pre-treated water is sent to the reverse osmosis modules, it is filtered through 24 wound polypropylene cartridge filters with a breaking capacity of 5 microns (20 absolute microns). With this, not only is the water in need of treat refined, but there is also added safety in the event that filter media is lost in prior stages of filtration.

Among other innovations, the desalination plant at Águilas/Guadalentín has established limiting the boron content in processed water to 0.5 mg/l as design criteria. In order to reach this goal, the plant has a two-pass reverse osmosis process. A single-stage frame configuration with 190 pressure tubes, each capable of holding 7 reverse osmosis membranes for seawater, has been adopted.

For reject energy recovery, the use of isobaric chambers for pressure exchange was chosen. The particular system chosen is the DWEER device. There will be three chambers in each line for a total of 36 energy recovery chambers for the production of 60 hm³/year.

Some of the 60% of permeate produced in the first pass of osmosis is directed to a second partial step that serves as boron refinement with a 90% conversion. This way, after mixing with the remaining 40%, a boron concentration less than 0.5 ppm is guaranteed for the design’s temperature range.

The post-treatment line for permeate water selected for this facility consists of remineralization by saturated water dosing in lime and carbon dioxide for the entire flow and sodium hypochlorite dosing as a disinfecting agent in the product water allocated to supply.

We’ll highlight a few of the technical particularities of this project:

• Having established the maximum limit of boron in the product water at 0.5 ppm.
• Installing two pressurized filter units manufactured out of FRP.
• The use of high-pressure sectioned pumps instead of the usual split-case pump.
• The use of garnet as a filtration material in the second filtration stage.
• The use of DWEER pressure exchange chambers.

Desaladora Aguilas Guadalentin Planta desoladora de Águilas