Effects of Nitrogen and Phosphorus Concentration Changes on the Growth of Dunaliella Salina in Reverse Osmosis Concentrated Brine

With the rapid development of Seawater desalination industry, the amount of concentrated brine discharged from desalination plants has also increased year by year. At present, the use of concentrated brine after seawater desalination is mainly found in the fields of salt production and chemical elements extraction. In this paper, the growth conditions, and secondary metabolites of Dunaliella salina under different nitrogen and phosphorus concentrations were studied using the concentrated brine produced by the most representative reverse osmosis seawater desalination process in Zhejiang Province as the carrier. All the experiments were carried out in a 250mL triangular flask separately. The culture water used was f/2 medium, diluted with desalination brine, and high-pressure sterilization at 121℃ for20 minutes. The amounts of nitrogen and phosphorus added to each flask were controlled according to the experiment design. Parameters such as OD660, chlorophyll, total saccharide content, total lipid and β-carotene were examined to describe the growth status of Dunaliella salina. The experimental results showed that Dunaliella salina grew well in concentrated brine. Different nitrogen concentrations exerted significant effects on algal density, total chlorophyll and β-carotene of Dunaliella salina (P <0.05). Different phosphorus concentrations exerted significant effects on total chlorophyll, total sugar and total lipid of Dunaliella salina (P <0.05). Under the initial nitrogen concentrations of 3520μmol/L and the initial phosphorus concentrations of 144μmol/L, the growth of Dunaliella salina was the best and the total lipid accumulation was the most. Under the initial nitrogen concentration of 1760μmol/L and the initial phosphorus concentration of 36μmol/L, the total chlorophyll accumulation of Dunaliella salina was the most. Under the initial nitrogen concentration of 7040μmol/L and the initial phosphorus concentration of 36μmol/L, the total sugar accumulation of Dunaliella salina was the most. Under the initial nitrogen concentration of 7040μmol/L and the initial phosphorus concentration of 288 μmol/L, the total β-carotene accumulation of Dunaliella salina was the most. It is feasible to cultivate Dunaliella salina using concentrated brine after seawater desalination, which is of great significance for widening the utilization of concentrated brine.