Hielscher Ultrasound Technology

Ultrasonic Cleaning of Photo-Bioreactors

Microalgae can be grown in shallow ponds or photo-bioreactors. In bioreactors, an algae film tends to grow on the inner reactor surface, blocking sunlight and restricting photosynthesis. Ultrasonic cleaning – applied from the outside – removes this algae film efficiently.

Photosynthetic microalgae is used in industries aiming to produce healthy food, food additives or biofertilizers. Microalgae can also be a means to sequester CO2 from industrial sources.

Design of Photo-Bioreactors

Photo-Bioreactor for Growing MicroalgaeThe single most important factor in limiting algae productivity is light. Therefore, continuous bioreactors primarily consist of transparent vessels columns or tubes, made of specialty plastics or glass. An algae bearing fluid is slowly pumped through the system, presenting all the algae to the sun absorption zone. The algae grows inside the closed system. This reduces the possibility of infestation. A controlled amount of CO2 is injected into the photo-bioreactor to maximize photosynthesis.

Ultrasonic Reactor Cleaning

Ultrasonic Cleaning of Bioreactor
A special ultrasonic sonotrode can travle along the bioreactor tubes to remove fouling.

Fouling at the inner surfaces of the bioreactors block sunlight – a crucial factor for algae productivity. Hielscher ultrasonic devices are used in a novel method to clean the inner surface of glass reactor tubes effectively. An ultrasonic sonotrode is pressed against the outer surface. This couples ultrasonic vibrations to the glass, that lead to a vibration of the glass itself. This removes the fouling from the inner surface. The loose algae is flushed away and the sunlight can reach into the reactor again. In order to clean multiple long tubes, a single ultrasonic system can be moved along each tube and from tube to tube.

More Ultrasonic Processes for Algae

Algae is also an interesting sustainable feedstock for biodiesel manufacturing. Ultrasonication improves the extraction of oil from the algae cells and the conversion to biodiesel.

We recommend pilot scale trials e.g. using a special UIP500hd system. This will show the general effects and improvement for your particular reactor. All results can be scaled up. We will be glad to discuss your requirements with you and to recommend further steps.

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