An easy numerical evaluation of the DM growth in Self-Forming Dynamic Membrane Bioreactors (SFD MBR) for Wastewater Treatment

In the last years, self-forming dynamic membranes (SFD MBR) revealed as one of the most innovative technological solutions for wastewater treatment. In these systems, filtration takes place through a cake layer (Dynamic Membrane, DM) supported by a 10-200 µm filter mesh. Filtration efficiency may decrease when the DM becomes too thick or its composition changes, and this can be measured under constant flux through the increase of TMP (TransMembrane Pressure). In this study, three different DM maintenance strategies have been adopted to limit the loss of performance caused by excessive cake layer growth. A 4h filtration cycle was applied ending with a filtration break of 11' with different mesh cleaning strategies. The cake growth on the support mesh was analyzed evaluating the TMP increase rate. TMP peaks in the range 20-200 mbar were observed during the 4h filtration cycles. These data were interpreted with second order interpolations and linear trends. Here, the slopes of the trend lines are used to evaluate the performance of the different DM maintenance strategies considered. These lines provide a simplified representation of the speed at which the pressure of 200 mbar is reached, once the DM thickness starts to increase (lower TMP instability threshold of 20 mbar). These slopes allow to estimate cake layer accumulation: the lower the slope value, the longer the time to reach the critical TMP value. Filtration efficiency may decrease when the DM becomes too thick or its composition changes, and this can be measured under constant flux through the increase of TMP (TransMembrane Pressure). In this study, three different DM maintenance strategies have been adopted to limit the loss of performance caused by excessive cake layer growth. A 4h filtration cycle was applied ending with a filtration break of 11' with different mesh cleaning strategies. The cake growth on the support mesh was analyzed evaluating the TMP increase rate. TMP peaks in the range 20-200 mbar were observed during the 4h filtration cycles. These data were interpreted with second order interpolations and linear trends. Here, the slopes of the trend lines are used to evaluate the performance of the different DM maintenance strategies considered. These lines provide a simplified representation of the speed at which the pressure of 200 mbar is reached, once the DM thickness starts to increase (lower TMP instability threshold of 20 mbar). These slopes allow to estimate cake layer accumulation: the lower the slope value, the longer the time to reach the critical TMP value.