Performance analysis of Picochlorum maculatum reared on a twin-layer recirculation system in nutrient recovery from aquaculture effluents

This study evaluates the feasibility of microalgae cultivation in a twin-layer recirculation system (TLRS) for nutrient removal from the aquaculture effluents. The green microalga Picochlorum maculatum (KJ754560) was cultivated in a TLRS module made up of two different types of layers, a macroporous metal wire mesh source layer and the microporous substrate layer. Three different microporous substrate layers, viz. Protran reinforced nitrocellulose membrane (PRNM), printing paper (PP) and nylon mesh (NM) were assessed for their efficiency in anchoring the algae. With continuous water flow in the TLRS system, there was no need for aeration or an external CO 2 supply. Further, no eukaryotic contaminations were noticed during the experiment owing to the microporous substrate layer, which reduced risk of contamination. During the 15 th day treatment period, the highest growth of P. maculatum on PRNM substrate was 7.52 ± 1.12 gm −2 on a dry weight basis, which was significantly higher ( p > 0.05) than the growth on the other two substrates such as NM (5.61 ± 0.1 gm −2 ) and PP (2.53 ± 0.3 gm −2 ). After treatment, P and N concentrations in the effluents could efficiently be reduced by 85–99%. Thus, it could be concluded that the TLRS with NM as microporous substrate provided best environment for cultivation of P. maculatum , in removing nitrogen and phosphorus from aquaculture effluents. Graphical abstract