Limitation du colmatage dans un bioréacteur à membranes à l’échelle semi-industrielle : modélisation et caractérisation de l’hydrodynamique

Abstract

Membrane bioreactors (MBRs) are widely used in the wastewater treatment sector. In spite of many benefits of MBRs, the fouling of their membranes leads to important maintenance and energy costs. Several strategies have been industrially developed to enhance MBR productivity, including coarse bubble sequenced aeration for fouling mitigation. However, more research is needed to characterize hydrodynamics in MBRs filled with activated sludge at industrial scale. A semi-industrial reactor was designed, equipped with membranes and fed with activated sludge from one of the reactors of the Seine Aval (Siaap) wastewater treatment plant. This reactor was used to study the impact of aeration strategies on filtration performance by coupling statistical analysis (fuzzy inference systems) and hydrodynamic characterization (electrical resistivity tomography, ERT). Preferential flow paths have been observed at high mixed liquor suspended solids concentration and low air flow rates with ERT measurements. These observations give explanations for the obtained decision tree focused on the impact of air flow rate on the daily permeability evolution. The suspended solids concentration and chemical oxygen demand difference between supernatant and permeate turn out to have a major impact for the studied operating conditions. They influence the aeration efficiency on fouling mitigation, due to the heterogeneity of aeration or the release of fouling materials. These results reinforce the interest in linking aeration parameters to sludge properties, suggesting to consider control strategies for these operating parameters at industrial scale.