Clemens Fritzmann, Matthias Hausmann, Matthias Wessling, Thomas Melin:
Structured spacers for fouling control with low energy consumption in submeged membrane systems
Poceedings 13th Aachener Membran Kolloquium, pp. 77
Submerged membrane systems are applied in filtration of mixtures that are characterized by high solid loads, high fouling propensity and that bear a high risk of channel blockage. Typical applications such as membrane bioractors (MBRs) therefore suffer from severe fouling and measures to consistently clean the membrane and to minimize fouling during operation must be sought . In submerged membrane systems, air scouring is used for removal of a fouling layer to maintain stable operation . Rising bubbles result in higher shear stress and further initiate fluid cross flow as well as lateral movement of the membranes, which contributes to the removal of foulants from the membrane. The downside of the application of air sparging is its high energy demand, which has been estimated to contribute 50 - 80 % to the total energy consumption of the overall process [3-5]. The high energy demand is thus one of the main bottlenecks of current submerged systems and is a main cause for the limited spread of the technology. Therefore measures must be taken to further reduce the necessity for air sparging aiming at a more energy efficient overall process. In flat sheet membrane modules, applied for example in reverse osmosis or ultrafiltration, spacers largely contribute to efficient operation, since the spacer induced hydrodynamics enhances mass transfer, while at the same time fouling is reduced. Due to the current spacer designs with filaments that provide obstacles in the flow field leading to local stagnant flows and a high risk of channel blockage, the application of spacers is limited to filtration of fluids with limited solid loads. In this work, a new type of membrane spacer is introduced that is especially suitable for the rather harsh conditions found in filtration of high solid loads. Main spacer and process design parameters are evaluated in experiments with model fouling solutions. The filtration performance with application of spacers is then compared to the process without the use of spacers. The spacers are further applied to filtration of digestate to test their performance in a real filtration problem.