A novel method for pH mediated electroflocculation in saltwater systems

Area of Science:

• Biotechnology and Bioengineering
• Sustainable Resource Management
• Aquaculture and Algal Cultivation

Background:

• Microalgae are a valuable resource for biomass, feed, food, and fuels.
• Harvesting microalgae is challenging due to low cell concentrations and small sizes.
• Electroflocculation offers a simple method for microalgal harvesting but can damage cells in seawater.

Purpose of the Study:

• To develop a method for protecting microalgal cells from oxidative damage during electroflocculation in seawater.
• To improve the harvesting efficiency of difficult-to-settle microalgal strains.
• To assess the energy requirements for membrane-protected electroflocculation.

Main Methods:

• Integration of a regenerated cellulose membrane into an electroflocculation system using non-sacrificial anodes (graphite or titanium).
• Testing the technique on the saltwater microalga Picochlorum celeri TG2.
• Measurement of clarification, settling velocity, compaction factor, and energy consumption.

Main Results:

• The membrane protected microalgal cells from oxidative damage caused by Cl2 and chloride compounds.
• Achieved approximately 95% clarification and a compaction factor below 0.2 for Picochlorum celeri TG2.
• Reported energy consumption values, with the best volumetric energy consumption at 3.1 kWh/m³ and biomass energy requirement at 3.0 kWh/kg.

Conclusions:

• Membrane-protected electroflocculation is a viable technique for efficient microalgal harvesting, especially for challenging species.
• The method simplifies harvesting by significantly increasing settling efficiency.
• The energy efficiency is suitable for integration into continuous microalgal biomass production processes.