Microalgae Filtration Using an Electrochemically Reactive Ceramic Membrane: Filtration Performances, Fouling Kinetics, and Foulant Layer Characteristics

Abstract

Electrochemical membrane filtration has proven to be successful for microbial removal and separation from water. In addition, membrane fouling could be mitigated by electrochemical reactions and electrostatic repulsion on a reactive membrane surface. This study assessed the filtration performances and fouling characteristics of electrochemically reactive ceramic membranes (a Magneli phase suboxide of TiO 2 ) when filtering algal suspension under different dc currents to achieve anodic or cathodic polarization. The critical flux results indicate that when applying positive or negative dc currents (e.g., 1.25−2.5 mA•cm −2 ) to the membrane, both significantly mitigated membrane fouling and thus maintained higher critical fluxes (up to 14.6 × 10 −5 •m 3 •m −2 •s −1 or 526 LMH) compared to the critical flux without dc currents. Moreover, applying dc currents also enhanced membrane defouling processes and recovered high permeate flux better than hydraulic and chemical backwash methods. Moreover, fouling kinetics and the cake layer formation were further analyzed with a resistance-in-series model that revealed many important but underexamined parameters (e.g., cake layer resistance and cake layer thickness). The cake layer structures (e.g., compressibility) were shown to vary with the electrochemical activity, which provide new insight into the biofouling mechanisms. Finally, the algogenic odor, geosmin, was shown to be effectively removed by this reactive membrane under positive dc currents (2.5 mA•cm −2 ), which highlights the multifunctional capabilities of electrochemically reactive membrane filtration in biomass separation, fouling prevention, and pollutant degradation.

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

“…The total resistances were 5.2×10 11 ± 1050, 1.8×10 12 ± 800, and 2.1×10 12 ± 500 m −1 for P19‐60, T1‐0.2 μm, and T1‐0.8 μm membranes, respectively. The same trend of total resistances with ceramic UF membranes with various pore sizes were reported with Arthrospira platensis (5.0 × 10 12 m −1 ) at CFV 3.0 m s −1 and TMP 100 kPa, 46 and with Scenedesmus diphormis (4.0 × 10 12 and 9.0 × 10 11 m −1 ) when applying DC currents 27 . They showed a higher contribution of R r than that of the irreversible one to R T .…”

“…The flux dropped from 79.12 ± 12 to 58.4 ± 15, from 90.5 ± 10 to 62.5 ± 16, and from 114.3 ± 11 to 69.8 ± 13 L m −2 h −1 , which represent a flux loss of 26.10, 30.55, and 38.95% for 50, 75, and 100 kPa, respectively. Indeed, the flux decline was due to the deposition of microalgae cells and EOMs released by the microalgae cells, which clogged the membrane pores during the filtration process 11,27 …”

“…They reported that the dynamic method initially provides higher water flux, but leads to more energy consumption and a substantial reduction in permeability over time compared to crossflow filtration 26 . In another study, Hua et al 27 introduced a crossflow filtration system equipped with electrochemically reactive ceramic membranes for microalgae harvesting. Although their reports show that electrochemical reactions and electrostatic repulsion on a reactive membrane surface provide membrane fouling mitigation, the energy consumption of the proposed system remains a big barrier for its industrial applications 27 .…”

“…In another study, Hua et al 27 introduced a crossflow filtration system equipped with electrochemically reactive ceramic membranes for microalgae harvesting. Although their reports show that electrochemical reactions and electrostatic repulsion on a reactive membrane surface provide membrane fouling mitigation, the energy consumption of the proposed system remains a big barrier for its industrial applications 27 . In addition, Purnima et al 28 .…”

Harvesting Microalgae for Food and Energy Products

“…[ 65 ] Negatively charged membrane surfaces can alternately be created by applying current to conductive ceramic filters, with comparable benefits to fouling resistance. [ 66 ]…”