Proceedings

Thermal and kinetic energy drive water from their bondage in sludge – but what about the structures that hold the water in place? Water is retained in a matrix of charged compounds around the sludge, and in a classical dewatering system, these compounds are bound together with poly-electrolytes to create a dense floc in which the next dewatering unit applies thermal and/or kinetic energy to release the water. However, if some of the charged compounds that make up this matrix are selectively degraded while maintaining the flocculation effect of the poly-electrolyte, then a denser floc can be formed that allows the release of water with less energy and in effect enhances the action of the poly-electrolyte. This concept is core to the action of Novozymes’ BioSec®, a cocktail of proteases and cellulases selected to specifically target water retaining compounds in municipal anaerobic digestion sludge, thus creating drier, denser flocs alongside more efficient poly-electrolyte. Here we present a statistical analysis of the full-scale applications of BioSec® to date compared against the normal output of the notoriously variable wet-cake, as well as perspectives on future gains and challenges, with a focus on sustainability.