LAUSR

Abstract This study investigates the capability of Tetraselmis sp. for treating mariculture wastewater in a 70-L high-rate algal pond and determines the feasibility of using the resulting biomass. The culture medium contained 45 mg L–1 nitrates, 10 mg L–1 nitrites, 30 mg L–1 ammonium, 17 mg L–1 orthophosphates and 270 mg O2 L–1 of dissolved organic matter as chemical oxygen demand (COD). The culture was kept under a 12 h:12 h light:darkness photoperiod using a photosynthetically active photon flux density of 1500 μmol m–2 s–1, and a temperature of 23 ± 2 °C. A 4-cycle growth semicontinuous culture was used obtaining on average 1.19 g L−1 dry biomass, with lipid content of 62.16 mg g−1. In the first batch culture cycle, 11.4 % of highly non-saturated fatty acids were obtained, and a significant decrease thereof was observed in subsequent batch culture cycles. Nutrient removals were 95.5 ± 0.4 % total nitrogen, 94.4 ± 0.5 % ortho-phosphates and 61.4 ± 3.9 % COD. These results show the feasibility of mariculture wastewater treatment using the studied microalga, with the advantage of producing biomass containing accumulated lipids and usable as food for mariculture species. Thus, it may be possible to reduce the cost of wastewater treatment and of culturing marine species.