Microfiltration for separation of green algae from water

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Green algae cultivation is crucial for biofuels and wastewater treatment.
• Efficient separation of microalgae from water is a key challenge in algal biotechnology.
• Microfiltration (MF) is a promising technology for algal biomass recovery.

Purpose of the Study:

• To evaluate the effects of transmembrane pressure (TMP) and cross-flow velocity on microfiltration performance for Chlorella sp. separation.
• To investigate the impact of preozonation on microfiltration flux and fouling behavior.
• To compare the performance of hydrophobic and hydrophilic membranes during algal microfiltration with preozonation.

Main Methods:

• Cross-flow microfiltration experiments were conducted using Chlorella sp. in freshwater.
• Transmembrane pressure was varied (40, 50, 60 kPa) and cross-flow velocity was set for laminar (0.43 m/s) and turbulent (0.84 m/s) flow.
• Preozonation was applied, followed by microfiltration using both hydrophobic and hydrophilic membranes. Hydrodynamic resistances were analyzed.

Main Results:

• Flux increased with TMP from 40 to 50 kPa, but declined sharply at 60 kPa.
• Increased cross-flow velocity enhanced initial flux at 60 kPa TMP, but turbulent flow did not mitigate the drastic flux decline.
• Preozonation reduced algal cell size and viability, increased dissolved organic carbon and polysaccharide content, and generally improved MF performance by reducing cake compressibility and biomass loading.
• Hydrophobic membranes showed increased fouling resistance due to adsorbed polysaccharides from preozonation.

Conclusions:

• Optimal TMP and cross-flow velocity are critical for efficient algal microfiltration.
• Preozonation can enhance microfiltration efficiency by altering algal cell characteristics and extracellular organic matter.
• Membrane material choice (hydrophobic vs. hydrophilic) significantly influences fouling behavior when preozonation is applied, necessitating careful selection for effective algal separation.