Application of Fe(NO3)3-based as nitrogen source and coagulant for cultivation and harvesting of Chlorella sorokiniana

- Ferric nitrate served both as coagulant and nitrogen source.
- 0.8 g/L ferric nitrate showed highest harvesting efficiency.
- The spent medium well supported Chlorella sorokiniana growth.
- Substantial amounts of nutrients could be saved.

In this study, Chlorella sorokiniana was successfully cultivated in the recycled medium whose nitrogen was supplied directly from the coagulant, Fe(NO3)3. With a dosage of 0.80 g/L, harvesting efficiency of 95% could be achieved. What is more, this amount of nitrate in the coagulant was enough to fully support the growth of C. sorokiniana during the 8 day cultivation period, almost as much as the initial nitrogen content in the BG11 culture medium. Other nutrients had to be supplemented, however, with at least 50% amount as in the BG11 recipe. C. sorokiniana culture grown in recycled medium replenished with 50% of nutrients showed much higher Fatty acid methyl esters (FAME) productivity than the control, with 88.3 mg/L/day. The recycle of the medium is certainly a way of reducing the water footprint for the purpose of microalgae-derived biodiesel production; better still, it may serve to lower the nutrient footprint.