Granular biofilm for the production of exopolymer substances
Résumé
In this work, aerobic granular biofilms are seen not only as system for wastewater treatments but also as biofactories able to produce exoplymer substances with valuable commercial interest. Among EPS, a fraction having gelling capacity can be targeted by combining an alkaline solubilization step and an acidic precipitation. The polymers obtained by this extraction method are called ALE (aginate like exopolymers). Maximizing the production of ALE will make the valorization of granular biofilms more profitable. In this framework, experiments were performed on a lab-scale reator at different organic loading rates (from 4.5 to 10.12 kgCOD/m 3 /d) leading to various sludge retention times. Granule stability was maintained for all values of OLR and SRT. Though the content of EPS in VSS remained constant for the tested OLR, the ALE content of EPS substantially decreased. Considering the SRT decreased when increasing the OLR, it seems the specific growth rate strongly determines the ability of granular biofilm to produce ALE. Measured young modulus that gives the gel stiffness was equal to 16 kPa and rather constant for all conditions tested.
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