The application of activated carbon for the treatment and reuse of the aqueous phase derived from the hydrothermal liquefaction of a halophytic Tetraselmis sp.

• Active carbon treatment greatly affected the organic nitrogen content.
• 1000× dilution of the treated HTL AP generated 0.41 g/L of biomass.
• Heavy dilutions required for microalgae growth.

The aim of this study was to determine how the treatment of the HTL AP with activated carbon would affect both growth and chemical composition of the microalgae. Tetraselmis MUR233 was grown in HTL AP (filtered and unfiltered) at 500×, 1000×, and 2000× dilutions in hyper saline conditions. The organic nitrogen and carbon component of the HTL AP was greatly reduced with the activated carbon treatment (TKN 52,000 ± 520 mg/L to 5900 ± 59 mg/L; TOC 19,000 ± 190 mg/L to 13,000 ± 130 mg/L). Growth of Tetraselmis MUR233 was achieved on all dilutions of HTL AP, with a maximum growth observed in the AP filtered 1000× dilution treatment (0.41 ± 0.09 g/L), this compares to a yield of 0.49 ± 0.10 g/L when grown in traditional culture media.