The role of fouling mechanisms in a submerged membrane bioreactor during the start-up

In the last years a great attention has been addressed towards new technologies to treat wastewater. Among these, the membrane bioreactor (MBR), combining a high efficiency in organic substance removal with an exceptional ability in suspended solids removal, is that one that in future will be able to have greater possibilities of technological development and application. However also this process shows some problems and among these the fouling seems to be that mainly influences the process as well as the life of the membrane. There are different fouling mechanisms, such as macromolecule adsorption, pore blocking and cake deposition. In particular, fouling phenomena is affected by concentration and composition of biomass and feed water, process configuration, membrane material and process operation, including hydrodynamic system [1]. The present study has been aimed to quantify the role of pore blocking and cake deposition in MBR fouling during the start-up period. In particular, it has been aimed to investigate about the relationship between solid accumulation and fouling increase during the biomass growth period in MBR. In order to characterize the fouling phenomena, the resistance-in-series model has been applied. Several resistances (intrinsic membrane, pore blocking and cake resistance) using such model have been evaluated. When the flux is constant, the total resistance depends basically by the TMP (Transmembrane Pressure) variations and the permeate viscosity.