Abstract

This study relates to water purification and thus environmental biotechnologies, but also possibly to other applications of decantation and sedimentation of particulate solids in the presence of biomacromolecules. Activated sludge settling characteristics are of paramount importance both for design and performances of activated sludge water treatment plants and we developed a device to observe this phenomenon. Using our device, our dynamic measurements of activated sludge decantation in the near infrared region (940 nm) presented apparent aberrations. For example, light transmission in the sample transitorily exceeded 100% of the transmission of pure water under certain conditions. Arguments are provided to interpret these results by a modification of the solvent (H₂O) properties, especially concerning some vibrational modes of water molecules. This assumption warrants a meticulous validation involving spectrometric analysis in the visible and near infrared region.

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