Efficient use of liquid digestate in microalgae cultivation for high biomass production and nutrient recovery

Abstract

In this study, different pre-treatment methods were applied to liquid digestate (LD) for the growth of the mixed microalgal culture. In addition, nutrient removal in the LD was investigated. Dilution, filtration, and centrifugation were applied as pre-treatment methods. Microalgal growth was evaluated as dry weight (DW) and nutrient removal was investigated with the analysis of ammonium (NH4+-N) and phosphate (PO4−3-P). Microalgal DW constantly increased throughout the experiment and reached the maximum values of 4.24, 4.02, and 1.47 g/L in centrifuged, diluted, and filtered medium, respectively. Maximum NH4+ (97.7%) and PO4−3 (50.4%) removal efficiency was observed in the centrifuged LD. Based on the results of this study, the optimum growth medium for microalgal growth was centrifuged LD but this culture can be cultivated in diluted LD up to 40-fold. Results also showed that using LD for microalgae production is a suitable application for both nutrient supply for microalgal growth and nutrient recovery from LD. HIGHLIGHTS Dilution, filtration, and centrifugation were performed as pre-treatment applications to liquid digestate.; Maximum biomass (4.24 g/L) was provided in the centrifuged medium after 29 days of cultivation.; The maximum removal of ammonium (97.7%) and phosphate (50.4%) was observed in the centrifuged liquid digestate.;

Keywords

• anaerobic digestion
• biogas
• microalgal growth
• nitrogen
• phosphorus