Pilot‐scale microalgae harvesting with ceramic microfiltration modules: evaluating the effect of operational parameters and membrane configuration on filtration performance and membrane fouling

Abstract

BACKGROUND Membrane fouling is one of the major drawbacks in microalgae harvesting that prevents the widespread application of membrane filtration. This study investigates the effects of operating parameters on the filtration performance and the fouling phenomenon of a pilot‐scale microfiltration (MF) system equipped with different ceramic membranes for Chlorella vulgaris culture harvesting. RESULTS A higher permeate flux was obtained with increasing the transmembrane pressure, resulting in lower irreversible and reversible filtration resistances. On the other hand, at a higher crossflow velocity above 4 m s−1, a high amount of extracellular organic matter (EOM) released by microalgal cells led to a higher irreversible resistance which, in turn, caused severe membrane fouling and a lower filtration flux. Furthermore, the membrane configuration and pore size have also significantly affected the permeate flux. Compared to the tubular membranes, and regardless of pore sizes, the multichannel MF membrane (pore size: 0.2 μm) exhibited a higher permeate flux that resulted in lower membrane resistances due to the lower release of EOM by microalgae cells. Moreover, the tubular membrane (pore size: 0.8 μm) showed a higher flux reduction with higher pore size because of the increase in the irreversible resistance with a high amount of EOM release. CONCLUSION The results revealed that the amount of EOM significantly associated with filtration conditions plays an important role in membrane fouling control. Considering the membrane configurations, the multichannel ceramic MF membrane (pore size: 0.2 μm) demonstrated a higher permeate flux due to its lower fouling property. © 2020 Society of Chemical Industry (SCI)

The Fouling Effect on Commercial Ceramic Membranes during Filtration of Microalgae Chlorella vulgaris and Monoraphidium contortum

“…The following resistances [15,17] occur in the microalgae filtration process: clean membrane resistance (R m ); irreversible resistance (R ir ); reversible resistance (R r ); and total hydraulic resistance (R t )-the sum of all resistances. R m is the resistance that occurs when water flows through a clean membrane.…”

“…Usually, in ultrafiltration, the permeate flux is higher than in microfiltration [14,15] but the opposite situation has also been reported [16]. The discrepancies may result from the hydrodynamic conditions and microalgae culture characteristics, and consequently on concentration polarization, pore blocking and cake formation, which can be explained by the resistance-in-series model [11,17].…”

“…One of the basic parameters in membrane processes is the material, from which the membranes are made. The most widely used are organic (polymeric) membranes, while inorganic (e.g., ceramic) membranes are much less popular [17]. Ceramic membranes, although more expensive, are characterized by a higher resistance to chemical washing, which allows for their longer use in the technological process.…”

“…Ceramic membranes, although more expensive, are characterized by a higher resistance to chemical washing, which allows for their longer use in the technological process. Furthermore, the higher hydrophilicity of ceramic membranes results in their higher permeability and better resistance to fouling [7,8,17,18]. For example, Elcik et al [15] studied polymeric membranes and noted severe membrane fouling in microalgae harvesting.…”

“…For example, Elcik et al [15] studied polymeric membranes and noted severe membrane fouling in microalgae harvesting. One of the effects of the higher membrane fouling of polymeric membranes compared to ceramic membranes is the lower permeate flux in filtration [17]. A comparison of the flux variation depending on the membranes tested is presented in the Supplementary Material (Table S1).…”