Coupling air-assisted backwash and rinsing steps: a new way to improve ultrafiltration process operation for inside-out hollow fibre modules

Ultrafiltration is a modern technology used for the production of drinking water. Current research in this area focus on the reduction of production costs through the development of innovative plants. The aim of this work is to study ways to limit the fouling of hollow fibre membranes during dead-end filtration for drinking water production. Effective fouling control is necessary to ensure sustainable operation. For this study two complementary procedures are studied and coupled: (i) rinsing to limit the accumulation of material prior to the formation of a deposit and (ii) air-assisted backwash (AABW) to remove the loosened deposits from the membrane and then to transport the deposits from the module. Results obtained during the filtration of natural surface water are discussed based on a comparison between the coupled process and conventional single phase backwash. The analysis initially compares the fouling velocities; then the energy consumption determined for the different operating conditions. The results confirm that backwash with two-phase flow greatly improves the removal of particulates and this has direct consequences on the degree of fouling. Furthermore, by coupling the rinsing step and the AABW procedure the fouling is significantly reduced leading to energy savings of 65% compared to a conventional backwash, without air injection.