21 september 2015

The largest hybrid desalination plant in the world

The most energy-efficient desalination solution.


Fujairah 2 is the largest hybrid desalination plant in the world, with a capacity equivalent to 595,000 m3/day of potable water. The hybrid desalination plant is exceptional not only due to its size but also because it combines the two technologies, Multiple Effect Distillation (MED) and Reverse Osmosis (RO), to which is added a pretreatment Dissolved Air Flotation (DAF) system. This state-of-the-art combination has proven to be a solution which meets the requirement for a constant, high quality potable water output, despite vast seasonal variations in the power output as well as algae bloom periods. 

The desalination plant is linked to a 2,000 MW power plant. The high drinking water demand in the UAE does not vary substantially with the seasons whereas the power demand does: during summer, the power demand is high due to the use of air-conditioning while it is lower during the winter months. Therefore, an innovative hybrid solution including MED and RO was called for to best match the demands from a cost as well as a performance perspective. The hybrid design is the most energy-efficient solution for production of desalinated water today.

The MED system composes the first section of the desalination plant and is the largest system of the two. It includes 12 MED units that are driven using steam extracted from the two condensing steam turbines and from the exhaust of the back pressure steam turbine. This provides maximum output from the MED units during the summer.
The second part of the desalination plant is based on RO and is driven by power rather than steam hence it can be operated independently of steam output and be used during winter to maintain water output when power demand is low. 


Spidflow: a new generation of rapid flotation

Red-tide events are often a problem in the region and as such, the leading-edge technical solution put in place at Fujairah 2 also features an innovative pretreatment solution upstream of the RO system: Veolia’s Spidflow™ Dissolved Air Flotation (DAF). Clarification of water containing low density particles is a delicate step, especially during episodes of fast algae growth.

Spidflow specifically fits seawater desalination pretreatment as an upstream step of a reverse osmosis membrane treatment chain. It is especially efficient during red tide algal bloom periods and provides unequalled water treatment efficiency by eliminating over 99% of algae. The efficiency was confirmed during strong algae blooms in February 2011 and March 2013, when Fujairah 2 was able to maintain its daily production capacity while other plants in the region were forced to shut down or greatly reduce their production.