InnoDAF · Innovative model-based design and operational optimization of Dissolved Air Flotation

Innovative model-based design and operational optimization of Dissolved Air Flotation

Water scarcity is being recognized as a global threat to human activity and water reuse strategies deserve special attention. Traditional wastewater treatment technologies deals with diluted wastes with diffuse emissions of methane and nutrients and are not deemed sustainable. The time has come to start redesigning sewage treatment focusing on maximizing the reuse in line with the cradle-to-cradle concept. This project is paving the way for the exploitation of a promising up-concentration approach, Dissolved Air Flotation (DAF), through a holistic modelling and experimental campaign to characterise and optimise processes and parameters. DAF, being explored as an emerging separation technology for up-concentration, is however vastly still a black box. Fundamental and applied research (spanning TRL 3-6) about DAF to optimize its performance is, therefore, urgently needed. Nevertheless, a fundamental understanding of complex systems can be achieved by using complex, yet powerful, mathematical modeling frameworks. In the case of DAF, this boils down to the interplay between three phases (solids, liquid and gas) in a three-dimensional space by means of partial differential equations. CFD (computational fluid dynamics) is specifically designed for this purpose and shows how velocity within the DAF tank changes as a function of design and operational variables. The reliability and accuracy of CFD simulation, however, are constrained due to the lack of physical understanding on the mechanism of the drag force, a dominating momentum exchange mechanism between phases. As for DAF, it could be even more challenging due to the difficulty for the mesh of given size (prefer coarse considering the computational load limit) to capture the flow behavior at both micro-scale (bubble) and macro-scale (reactor) level. Besides, the average bubble and floc size were usually assumed due to the complexity of describing the particle size distribution dynamics, which may not sufficiently capture the flow behavior, the key to DAF. InnoDAF aims to propose a multi-scale hypothesis of the three-phase interactions in DAF based on mechanistic models obeying principles such as mass, energy and momentum conservation. The model is completed by considering the bubble breakage/coalescence, and bubble-solid attachment/detachment. This complete model is used to optimize DAF to advance its TRL level significantly from both operational and system design perspectives.

Data: CORDIS, © European Union