Diphasic transfer of oxygen in vertical flow filters: a modelling approach

摘要

Oxygen renewal, as a prominent phenomenon for aerobic bacterial activity, deeply impacts verticalnflow constructed wetland (VFCW) treatment efficiency. The authors introduce a multiphase modelnable to simulate oxygen transfer in VFCWs. It is based on a two-phase flow module, and a transportnmodule. The transport module is able to deal with convection/diffusion phenomena, inter-phasen(air–water) mass exchange, and first-order kinetics. The first results displayed for the air phase allownus to draw the following ideas on the design of vertical filters. The ponding phenomenon is morenefficient for oxygen renewal than non-ponding batch loading: it provides a higher value, sooner, andndeeper in the filter. In non-colonised filters and for standard batch loading, oxygen convection in thenair phase is predominant for oxygen renewal. The seepage front limits oxygen renewal through thenbottom of the filter and leads to an insufficient oxygen concentration on the lowest part of the filter.