Tech focus: Dissolved air flotation technology

Red tide can turn the sea a rusty red colour as algae devour oxygen in the water.

Solution proposed to limit impact of algae on desalination

An industry expert has called for wider use of dissolved air flotation technology, to battle the affects of algal bloom on desalination and water treatment plants.

Coastal areas of the UAE have been plagued by an algal bloom – also known as red tide – for several months. The bloom became so dense it forced the Ghalileh desalination plant in Ras Al Khaimah to shut down periodically.

“Algae is floating in the water, so if that layer is close to the screen then it will go into the suction. Dissolved air flotation is a possible solution because it has been used in harvesting and farming for a long time,” Ahmed Al Shuha, technical director at Corodex Concorde Group, explained.

“We have seen in Brazil they use dissolved air flotation and then filters and pressure and disinfection, so it has been used before.”

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Algal bloom occurs when algae accumulate rapidly in a water column. The overpopulation of the algae can happen naturally, or due to human activity.

“It’s a natural phenomenon; the main reason is the temperature of the sea. If the nutrients are there and the temperature is warm enough then the algae will grow,” explained Al Shuha.

The danger of the red tide is it will increase fouling in membranes. “The algae is a very small size but if you try and push it through filters the cells will explode. This means the membranes get fouled,” said Al Shuha.

Dissolved air flotation involves dissolving air into the water  under pressure, then releasing it at atmospheric pressure in a flotation tank.