Actually, you can't remove it, it is present in every WWTP which I visited. You can apply only mechanical removal, but in normal conditions, it shouldn't grow so well.

Nevertheless, if there is really a lot of it, you should check whether the nutrients' removal efficiency is sufficient.

Please refer to the following interesting document.

https://www.krwa.net/portals/krwa/lifeline/currentissue/0507reduce.pdf

Regards

Thank you Anna Klepacz-Smolka and Bachir Achour for the reply! do you have any suggestions for valorization after mechanical removal? Maybe biogas?

Dear Fabiano,

The question of the use of algae in water treatment is a recurring subject that refers to:

On the one hand the production of recoverable materials

On the other hand to the capacity of assimilation and therefore of associated treatment.

Indeed, algae and more particularly micro and macro algae represent a significant diversity (and therefore a very large potential) with a high conversion rate (production of matter) based on metabolism that can be fermentative (heterotrophic) or photosynthetic ( autotroph). Finally, the algal cells are devoid of lignins, which facilitates their recovery via methanization.

It is photo-synthetic algae (assimilation of CO2, N and P) that can be used in water treatment, which requires pre-treatment of water to eliminate suspended matter and degradable carbon and thus promote good diffusion. light radiation necessary for photosynthesis. To do this, the applications of algae in water treatment are limited to the tertiary sector or to pre-treated anaerobically digested sludge dehydration centrates with the primary purpose of producing easily biodegradable and energy-generating biomass.

The use of algae for the production of material with high added value for the food industry, chemicals, cosmetics or even pharmaceuticals or biofuels does not come under this part insofar as the primary vocation is not the Wastewater.

It should also be noted that the interest of the production of algae is to be linked to international issues on the emission of greenhouse gases and the questions of "carbon tax" via their role in the fixation/capture of CO2.

In water treatment, two types of technologies are implemented for the growth and recovery of algae.

Excess algae can be:

1. Digested under anaerobic conditions and thus produce methane and therefore energy

2. Fermented to produce ethanol and other alcohols that can be used for the production of biofuels.

Algae processing technologies are being developed but the current production cost does not allow this sector to be competitive.

In the field of water treatment, the use of algae is currently not industrialized mainly for the following reasons:

Algae do not really carry out treatment but rather a fixation of nutrients (nitrogen and phosphorus). Thus, in the event of anaerobic digestion, these nutrients are released into the centrate and therefore brought back to the waterline. The interest of algae would therefore be exclusively the production of matter and the energy recovery that can be made of it (contribution in digestion).

The collection and thickening of algae remains a little industrialized point and can represent nearly 30% of the total operating cost. Depending on the type of culture, Physico-chemical sedimentation, flotation or filtration can be used but back to full-scale operations are available for real evaluation.

Regards

I would consult., "Standard Methods for the Examination of water and Waste water" available on line as well as from "American Water Works Association".

Dear Fabiano,

The presence of Lemna Major in WWTP secondary settling, makes it best feedstock for HTC process focusing on Lactic acid production. Perform the run 10-25% solid, time (2-6h), temperature (200-220 not more).