Do lectins play an important role in the micro colony formation of activated sludge flakes?

The (cost) efficiency and, hence, sustainability of biological wastewater treatment systems very much depends on the bioflocculation ability of the biomass. Poorly flocculated activated sludge severely hampers the water-sludge separation step, no matter whether it is gravitational (in classic activated sludge systems (CAS)) or filtration-driven (in membrane bioreactors (MBR)). Although bioflocculation of activated sludge has been intensively researched in the past, the underlying mechanisms are still not completely understood. Reasons for this reside in the complexity of the process involving the dynamically changing activated sludge composition and the interplay between different binding forces. The major building blocks of activated sludge flocs are the microcolonies which will dictate the overall strength of the activated sludge floc. In addition to the (commonly accepted) electrostatic and hydrophobic forces, this research will investigate whether lectins play a role in microcolony formation being a crucial prerequisite for activated sludge bioflocculation. Lectins are non-enzymatic proteins that can bind soluble carbohydrates or a carbohydrate which is part of a glycoprotein or glycolipid. Lectins have been reported to play an important role in plants, in pathogenesis of bacteria and in the coaggregation of bacteria such as in dental plaque and aquatic biofilms but are thus far not investigated in the context of activated sludge bioflocculation.