Prof. dr. ir. Ingmar Nopens - Ghent University
Water scarcity is being recognized as a global threat to human activity and water reuse strategies deserve special attention as raised in EU water directives. Traditional sewage (used water) treatment technologies such as conventional activated sludge deals with diluted wastes with diffuse emissions of methane and nutrients and are therefore not sustainable.
The approach of up-concentration of municipal effluent upon arrival at the water treatment plant followed by anaerobic digestion for the recovery of bioenergy and maximal reuse of the mineral nutrients and water allows closing cycles. The bottleneck here is that sewage is too diluted for optimal direct anaerobic digestion in practice. The core scientific problem in this novel design lies in the revolution of the technology paradigm to address the up-concentration issue. Dissolved air flotation (DAF) is such a separation technology that has the potential to address this issue. DAF, being explored as an emerging separation technology for up-concentration, is however vastly still a black box.
- 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.
- complete the model considering the bubble breakage/coalescence, and bubble-solid attachment/detachment given its necessity according to the confronting results.
- optimise DAF to advance its TRL level significantly from both operational and system design perspectives using a precision & efficiency well-balanced model.
Computational fluid dynamics (CFD), emerging as a day-to-day tool for understanding and prediction of flow behavior , is taking its place next to experimental development and mathematical theory as a way to new discoveris in science and engineering. Here, CFD is employed to address the multi-scale problem in DAF by obeying a well justified physical mechanism. Size distribution (bubble and floc) will be taken into consideration by employing the Population balance models (PBMs) embedded in the CFD framework. The complete model is allowed to better understand and predict the DAF process, i.e., PSD and particle trajectory as well as the flow behaviour.